Tag Archives: gravity

China builds the world’s first artificial moon

Chinese scientists have built an ‘artificial moon’ possessing lunar-like gravity to help them prepare astronauts for future exploration missions. The structure uses a powerful magnetic field to produce the celestial landscape — an approach inspired by experiments once used to levitate a frog.

The key component is a vacuum chamber that houses an artificial moon measuring 60cm (about 2 feet) in diameter. Image credits: Li Ruilin, China University of Mining and Technology

Preparing to colonize the moon

Simulating low gravity on Earth is a complex process. Current techniques require either flying a plane that enters a free fall and then climbs back up again or jumping off a drop tower — but these both last mere minutes. With the new invention, the magnetic field can be switched on or off as needed, producing no gravity, lunar gravity, or earth-level gravity instantly. It is also strong enough to magnetize and levitate other objects against the gravitational force for as long as needed.

All of this means that scientists will be able to test equipment in the extreme simulated environment to prevent costly mistakes. This is beneficial as problems can arise in missions due to the lack of atmosphere on the moon, meaning the temperature changes quickly and dramatically. And in low gravity, rocks and dust may behave in a completely different way than on Earth – as they are more loosely bound to each other.

Engineers from the China University of Mining and Technology built the facility (which they plan to launch in the coming months) in the eastern city of Xuzhou, in Jiangsu province. A vacuum chamber, containing no air, houses a mini “moon” measuring 60cm (about 2 feet) in diameter at its heart. The artificial landscape consists of rocks and dust as light as those found on the lunar surface-where gravity is about one-sixth as powerful as that on Earth–due to powerful magnets that levitate the room above the ground. They plan to test a host of technologies whose primary purpose is to perform tasks and build structures on the surface of the Earth’s only natural satellite.

Group leader Li Ruilin from the China University of Mining and Technology says it’s the “first of its kind in the world” that will take lunar simulation to a whole new level. Adding that their artificial moon makes gravity “disappear.” For “as long as you want,” he adds.

In an interview with the South China Morning Post, the team explains that some experiments take just a few seconds, such as an impact test. Meanwhile, others like creep testing (where the amount a material deforms under stress is measured) can take several days.

Li said astronauts could also use it to determine whether 3D printing structures on the surface is possible rather than deploying heavy equipment they can’t use on the mission. He continues:

“Some experiments conducted in the simulated environment can also give us some important clues, such as where to look for water trapped under the surface.”

It could also help assess whether a permanent human settlement could be built there, including issues like how well the surface traps heat.

From amphibians to artificial celestial bodies

The group explains that the idea originates from Russian-born UK-based physicist Andre Geim’s experiments which saw him levitate a frog with a magnet – that gained him a satirical Ig Nobel Prize in 2000, which celebrates science that “first makes people laugh, and then think.” Geim also won a Nobel Prize in Physics in 2010 for his work on graphene.

The foundation of his work involves a phenomenon known as diamagnetic levitation, where scientists apply an external magnetic force to any material. In turn, this field induces a weak repulsion between the object and the magnets, causing it to drift away from them and ‘float’ in midair.

For this to happen, the magnetic force must be strong enough to ‘magnetize’ the atoms that make up a material. Essentially, the atoms inside the object (or frog) acts as tiny magnets, subject to the magnetic force existing around them. If the magnet is powerful enough, it will change the direction of the electrons revolving around the atom’s nuclei, allowing them to produce a magnetic field to repulse the magnets.

Diamagnetic levitation of a tiny horse. Image credits: Pieter Kuiper / Wiki Commons.

Different substances on Earth have varying degrees of diamagnetism which affect their ability to levitate under a magnetic field; adding a vacuum, as was done here, allowed the researchers to produce an isolated chamber that mimics a microgravity environment.

However, simulating the harsh lunar environment was no easy task as the magnetic force needed is so strong it could tear apart components such as superconducting wires. It also affected the many metallic parts necessary for the vacuum chamber, which do not function properly near a powerful magnet.

To counteract this, the team came up with several technical innovations, including simulating lunar dust that could float a lot easier in the magnetic field and replacing steel with aluminum in many of the critical components.

The new space race

This breakthrough signals China’s intent to take first place in the international space race. That includes its lunar exploration program (named after the mythical moon goddess Chang’e), whose recent missions include landing a rover on the dark side of the moon in 2019 and 2020 that saw rock samples brought back to Earth for the first time in over 40 years.

Next, China wants to establish a joint lunar research base with Russia, which could start as soon as 2027.  

The new simulator will help China better prepare for its future space missions. For instance, the Chang’e 5 mission returned with far fewer rock samples than planned in December 2020, as the drill hit unexpected resistance. Previous missions led by Russia and the US have also had related issues.

Experiments conducted on a smaller prototype simulator suggested drill resistance on the moon could be much higher than predicted by purely computational models, according to a study by the Xuzhou team published in the Journal of China University of Mining and Technology. The authors hope this paper will enable space engineers across the globe (and in the future, the moon) to alter their equipment before launching multi-billion dollar missions.

The team is adamant that the facility will be open to researchers worldwide, and that includes Geim. “We definitely welcome Professor Geim to come and share more great ideas with us,” Li said.

Why don’t satellites fall down from the sky?

Image via Pixabay.

Satellites are able to stay in Earth’s orbit thanks to a perfect interplay of forces between gravity and their velocity. The satellite’s tendency to escape into space is canceled out by Earth’s gravitational pull so that it is in perfect balance. This is the same principle that explains how natural satellites, such as the moon, become locked in a planet’s orbit.

But some very smart people had to run some very complicated math to design the perfect satellite launch. If the satellite moves too fast, it escapes into space. Too slow and it is destined to crash into the atmosphere.

With the right distance, speed, and trajectory, an object can defy Earth’s gravitational pull for quite a long time. In fact, gravity — the same force that is trying to drag these down to the surface — is a vital force in keeping satellites orbiting around our planet.

And to make it entertaining, we’re going to start with rollercoasters.

Perpetually falling

If you’ve ever been on a rollercoaster, you’ll know that strange sensation you get in your gut around bends or hills. Physically speaking, that sensation is produced by inertia; although the cart is changing directions, your body is resisting this shift. You’re strapped in safely to the cart, but your internal organs have a bit more leeway to move. So, for a few moments, they essentially keep moving on the old trajectory, while the rest of your body is on a new one.

This process is summarized neatly in the first law of motion: an object, either moving in a straight line or at rest, will maintain that state until acted upon by an external force. “External force” here can mean a great many things, from air resistance to gravity to you hitting a flying ball with a bat.

Artificial and natural satellites rely on this law to stay above the clouds. Since there is no air resistance in space, once a body gets moving, there’s virtually nothing to slow it down. It doesn’t lose kinetic energy (momentum), so it can keep moving forever.

The satellites we build today get their energy from the rockets that bring them to orbit. They do have internal fuel supplies and thrusters, but these aren’t used to maintain speed. They’re for maneuvers such as avoiding debris or shifting orbits. Rockets impart the satellites they carry with quite a lot of energy, as they need to travel at speeds of at least 17,600 mph (28,330 km/h) to be able to escape Earth’s gravity. After separation from the satellite, this leaves enough energy to keep that satellite in orbit around the Earth for several decades, even a few centuries.

Still, the purpose of a satellite is to stay closeby (relatively speaking) so it can beam our social media posts all over the world. But from what we’ve seen so far, shouldn’t they just travel into space forever? Yes. But there’s one other force at play here — gravity. While momentum keeps satellites moving, gravity is what keeps them in our orbit.

If you fill a bucket with water and spin it really fast, you’ll see that the water won’t pour out of it. It’s being pushed against the bottom of the bucket by inertia (in this case, centrifugal force), but that bucket and your arm work against the force. They even out in the end: the water can’t move through the bucket’s bottom, it can’t escape over the lip, either, so it kind of stays in one place.

For satellites, the Earth’s gravity acts as the arm and bucket in the above example. One really simple way to understand the process is to visualize the satellite as a rocket that’s always going forward, tied with a very long chain to the center of our planet — it will just go around in circles.

What’s important here is to get the distance right. First off, you want your satellite to be outside of the planet’s atmosphere, so as to avoid air drag and keep a constant speed. But you don’t want to be too far away, because the force of gravity is inversely proportional to the squared distance between two objects. So if you double the distance between a satellite and the Earth, gravity would only pull on it one-quarter as strongly. If you triple it, it would only be one-ninth of the force. In other words, put a satellite too close to Earth and it will fall. Put it too far away, and it escapes into space.

In essence, what engineers try to do when putting a satellite in orbit is to make it fall forever. We put it up high enough that air friction is almost zero (ideally, zero). Then we push it really fast in one direction. Finally, we rely on the Earth’s gravity to pull it down while it is moving forward, so the resulting movement is a circle. Because it’s moving forward and the planet is round, it’s essentially gaining altitude constantly. But, since it’s also falling at the same time, it’s losing altitude constantly. The sweet spot is to have it escape into space just as fast as it’s falling down to Earth, all the time.

If the math is done just right and the deployment phase goes properly, these two cancel each other out, and we get an orbiting satellite. In practice, it never goes quite perfectly, which is why these devices are fitted with fuel and thrusters so they can perform tiny adjustments to their direction of motion or altitude and keep them in orbit.

A good example of what would happen in the absence of these thrusters is the Moon. Our trusty and distinctive nighttime companion is not on a stable orbit — it’s slowly escaping Earth’s gravitational pull. Due to the specifics of how the Earth’s gravitational field interacts with the Moon, our planet is ever-so-slowly accelerating it into a higher orbit. Continuing with the above example, it’s making the ‘escape into space’ force a tad more powerful than the ‘falling down to Earth’ force. As a consequence, the Moon will probably break out of orbit with Earth in the future, but we’re talking billions of years here.

Alternatively, we have (had?) the Mir space station as an example. This Russian installation ended its mission in March 2001 and was brought to a lower orbit — it was ‘deorbited‘. Here, air friction steadily slowed it down. Because of this, gravity started gaining the upper hand and Mir eventually burned up in the atmosphere while spinning around the globe, closer and closer to the surface.

The physics of how bodies in space interact is always fascinating, at least it is to me, and generally has a weird quirk to it that spices every scenario up. The idea that something can keep falling forever without actually coming closer to the ground certainly is quirky, and it fascinated me ever since I first came upon it. Later, sci-fi would bring me to concepts such as gravitational slingshots, which are very similar to what we’ve discussed here, but they actually help you go to space faster. Cool.

Our discussion so far makes this whole process sound simple, and in theory, it is. But very many bright people had to crunch some extremely complicated math to make it possible, and many still do that, in order to keep satellites orbiting over our heads. As much as falling forever sounds like magic, it’s built on countless hours of intellectual work and, in this day and age, on some very powerful computers running calculations around the clock. 

Scientists measure the smallest gravitational field yet

Credit: Tobias Westphal, University of Vienna.

Physicists at the University of Vienna have managed to measure the gravitational field between two tiny gold spheres with a radius of merely 1 millimeter. In doing so, they’ve effectively measured gravity over the smallest distance to date and probed the nature of gravity at one of the smallest scales that our instruments permit.

Testing the boundaries of fundamental physics

Our knowledge about the subatomic composition of the universe is summarized in what is known as the Standard Model of particle physics. The Standard Model describes both the fundamental building blocks out of which everything is made and the forces through which these blocks interact. There are twelve basic building blocks that we know of (six quarks and six leptons) and four fundamental forces (gravity, electromagnetism, and the weak and strong nuclear forces). Each fundamental force is produced by fundamental particles that act as carriers of the force. For instance, the photon, which is a particle of light, is the mediator of electromagnetic forces.

The behavior of all of these particles and forces is described with the utmost precision by the Standard Model, with one notable exception: gravity.

By testing the coupling force of gravity between very small objects it may be possible to shed more light on what’s missing in our standard model of physics in order to account for gravity’s disconnect from quantum theory.

However, it’s just proven extremely challenging to describe gravity microscopically. This is one of the most important problems in theoretical physics today — finding a quantum theory of gravity.

This is where this new study may come into play.

Credit: Arkitek Scientific

For their research, the team at the University of Vienna led by quantum physicist Markus Aspelmeyer devised an experiment designed to isolate gravity as a coupling force between two tiny gold spheres, each with a mass of just 90 mg.

“The most fundamental questions in physics were always the ones that motivated me most. With this experiment we are already charting new territory, looking into long-standing puzzles like dark energy and fifth forces. The prospect of contributing to the question of gravity must be quantized, even if this is still a long way to go, is highly fascinating as well. As a first step to do this we established techniques to measure small gravitational forces and confirmed the known laws of gravitation on smaller scales than ever before,” Jeremias Pfaff, a physicist at the University of Vienna and co-author of the new study, told ZME Science.

This was actually a lot harder than it sounds, as the team had to overcome a number of painstaking challenges.

“A pendulum able to measure such small acceleration must be extremely
delicate. Building the first few prototypes, we had to insert an almost
invisible tungsten wire into the 10-micrometer hole of a hollow core
glass fiber – which took us hours upon hours – something I surely won‘t
forget,” Pfaff said.

But in the end, it all paid off. The setup was so sensitive that even tiny disturbances such as the rumble of passing-by buses, cable cars, and even earthquakes thousands of miles away could be detected.

To minimize external disturbances, the setup was encased in a Faraday shield that blocks electrostatic forces. One of the gold spheres was connected to a vacuum chamber to minimize seismic and acoustic effects.

The results weren’t surprising, confirming Newtonian physics in that the gravitational force between the two tiny objects depends on their masses and distance.

In the future, the team plans on improving the sensitivity of their experimental setup in order to probe gravitational coupling in objects with an even smaller mass — at least 1,000 times lighter and even shorter distances.

“Why is this interesting? Gravity is omnipresent in our daily lives, and yet our understanding of this phenomenon is far from complete! Experiments that investigate gravity at such small scales explore “terra nova” and may shed new light on its fundamental nature. Even though tackling these deep scientific questions is not motivated by an instant technological benefit, the process of discovering the underlying principles of nature is deeply rooted in human curiosity and hence of interest for everyone,” Pfaff concluded.

The findings appeared in the journal Nature.

NASA releases beautiful new animation of a black hole

A beautiful new animation produced by NASA helps visualize the relationship between gravity, time, and space.

Image credits NASA Goddard Space Flight Center / Jeremy Schnittman.

Researchers at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, have generated a new animation of a black hole and its surrounding matter disk. The animation is based on radio images of a black hole at the core of galaxy M87 taken by the Event Horizon Telescope.

Bendy time

“Simulations and movies like these really help us visualize what Einstein meant when he said that gravity warps the fabric of space and time,” says Jeremy Schnittman, Ph.D., the NASA astrophysicist who generated these gorgeous images using custom software

Schnittman’s work helps to showcase how the huge gravity around a black hole distorts the way we perceive its surroundings. That halo-like structure is, in fact, a disk. This accretion disk is a relatively thin mass of gas infalling into the black hole; we see it in the particular shape shown above because gravity is bending light around the black hole. It’s pretty similar to bending a picture of the disk.

Gas in accretion disks is very hot (through a combination of friction and compression), so it radiates in different parts of the electromagnetic spectrum. Those around the youngest of stars glow in infrared, but the disk in this animation glows with X-rays, because it has a lot of energy. It ripples and flows as magnetic fields move along its bulk. This creates brighter and dimmer bands in the disk.

The gas also moves faster the closer it gets to the black hole — close to the speed of light nearest to it. In the animation above, this makes the left side look brighter than the right side due to redshift.

The thin line of light that seemingly outlines the black hole is its “photon ring”. You’re actually looking at the underside of the disk, its image bent back to us by the massive gravitational pull there. What we see as the photon ring is made up of several layers that grow progressively thinner and dimmer — this is light that’s been bent several times around the black hole before escaping for our telescopes to capture. Schnittman’s model uses a spherical black hole, so here the photon ring looks identical from every angle.

“Until very recently, these visualizations were limited to our imagination and computer programs,” Schnittman says. “I never thought that it would be possible to see a real black hole.”

Physicists say sound waves might actually carry mass

Credit: Pixabay.

In a surprising new study, scientists claim that sound waves could theoretically carry mass, which implies that they’re also affected by gravity.

“You would expect classical physics results like this one to have been known for a long time by now,” Angelo Esposito from Columbia University, the lead author on the paper, told Scientific American. “It’s something we stumbled upon almost by chance.”

Previously, researchers at Columbia University and Carnegie Mellon University showed that phonons could have mass in a superfluid — a liquid that flows without friction. Phonons are particle-like excitations which correspond to collective oscillations of atoms inside a molecule or a crystal.

It’s easier to understand phonons in relation to their cousins, the much more famous photons. We know from Newtonian physics that atoms and molecules vibrate away from their equilibrium positions, a motion that we recognize as heat. Basically, the more the atomic lattice vibrates, the higher the temperature. But this classical view doesn’t offer the full picture unless we also include quantum mechanics — the physics of the microscopic world.

‘Quantum’ refers to the smallest indivisible unit to things. For instance, a quantum of light is a photon — the smallest amount of light there is. Similarly, when you apply quantum mechanics to a lattice structure, there’s a ‘smallest packet of lattice vibration’ called a phonon.

The word phonon is derived from ‘phonos’, which is greek for sound. This is because long-wavelength phonons can be interpreted as single waves of sound propagating through the lattice.

In their new study, Esposito and colleagues used approximations known as effective field theory to show that phonon could not only have mass in a superfluid, but in other types of materials as well, including room-temperature liquids and solids; even in air, the primary medium through which sound waves propagate.

The study not only contradicts that popular notion that phonons are massless, but also suggests that they carry negative mass. Something with negative mass also implies negative gravity, which means it would repel other matter around it. Likewise, if you’d push an object with negative mass, it would accelerate towards you. Phonons having negative mass implies that their trajectory would gradually move away from a gravitational field such as that of the Earth. For water, the researchers calculated that phonons traveling through such a medium would drift by about one degree over 15 kilometers, which makes it extremely challenging to measure.

“In a gravitational field phonons slowly accelerate in the opposite direction that you would expect, say, a brick to fall,”  Rafael Krichevsky, a graduate student in physics at Columbia University, told Live Science.

Hover, this mass is extremely tiny — comparable with a hydrogen atom, about 10–24 grams. This is another measuring challenge, although it is still theoretically possible to do. According to the researchers, we do not currently have the necessary technology to measure the mass of phonons. However, they envision an experimental setup where super-precise clocks would detect the slight curvature of a phonon’s path.

Although sound waves carrying mass will not influence our daily lives, the notion carries certain important practical implications in science. For instance, in the dense cores of neutron stars, sound waves move at nearly the speed of light — that’s a lot of energy, meaning that an anti-gravitational sound wave should pose significant effects on the star’s behavior.

The findings appeared in the journal Physical Review Letters.

Contour maps depict changes in gravity gradient immediately before the earthquake hits. Credit: Kimura Masaya.

New gravity earthquake detection method might buy more time for early warnings

Scientists from Japan, one of the most seismically active regions of the globe, claim that a new earthquake detection method based on gravity could provide an earlier warning than traditional methods.

Contour maps depict changes in gravity gradient immediately before the earthquake hits. Credit: Kimura Masaya.

Contour maps depict changes in gravity gradient immediately before the earthquake hits. Credit: Kimura Masaya.

In 2011, a magnitude-9 earthquake hit eastern Japan, along a subduction zone where two of Earth’s tectonic plates collide. The tremor came as a one-two punch, generating a huge tsunami in the process which led to the meltdown of the Fukushima Daiichi nuclear power plant. The effects of the powerful quake were devastating, with more than 120,000 buildings left in rubble and $235 billion-worth of incurred damage.

Japan handled the onslaught bravely and admirably. Thanks to its sophisticated network of sensors, Tokyo residents were given a minute warning via texted alerts on their cell phones before the city was hit by strong shaking. These sensors also recorded a wealth of data that is still keeping researchers busy with work that might lead to improved earthquake detection.

Exactly 8 years after the Tohoku earthquake, a team of researchers from the University of Tokyo’s Earthquake Research Institute (ERI) used some of this data to argue that a new detection method based on gravimeters could theoretically detect earthquakes earlier than seismometers.

Gravimeters are sensitive devices for measuring variations in the Earth’s gravitational field. They’re typically employed by industries to prospect subterranean deposits of valuable natural resources, including petroleum and minerals, but also by geodesists who study the shape of the earth and its gravitational field.

When an earthquake occurs at a point along the edge of a tectonic plate, it generates seismic waves that radiate outward at up to 8 kilometers per second. These waves transmit energy through the earth, thereby altering the density of the subsurface material they pass through. Denser material has a slightly greater gravitational attraction than less dense material, and since gravity waves propagate at the speed of light, it’s possible to measure these changes in density before the arrival of a seismic wave.

The Japanese researchers combined gravimetry and seismic data, which they fed into a complex signal analysis model. The results scored 7-sigma accuracy, meaning that there’s only a one-in-a-trillion chance that they are incorrect.

“This is the first time anyone has shown definitive earthquake signals with such a method. Others have investigated the idea, yet not found reliable signals,” ERI postgraduate Masaya Kimura said in a statement. “Our approach is unique as we examined a broader range of sensors active during the 2011 earthquake. And we used special processing methods to isolate quiet gravitational signals from the noisy data.”

TOBA prototype. Credit: Ando Masaki.

TOBA prototype. Credit: Ando Masaki.

At the moment, the researchers are working on a new kind of gravimeter called the torsion bar antenna (TOBA), which aims to be the first instrument specifically designed to detect earthquakes by gravity. A network of such devices could theoretically warn people 10 seconds before the first seismic waves arrive from an epicenter 100 km away. These precious extra seconds could mean the difference between life and death in many situations.

“SGs and seismometers are not ideal as the sensors within them move together with the instrument, which almost cancels subtle signals from earthquakes,” explained ERI Associate Professor Nobuki Kame. “This is known as an Einstein’s elevator, or the equivalence principle. However, the TOBA will overcome this problem. It senses changes in gravity gradient despite motion. It was originally designed to detect gravitational waves from the big bang, like earthquakes in space, but our purpose is more down-to-earth.”

The findings appeared in the journal Earth, Planets and Space.

New NASA data reveals many of Jupiter’s hidden secrets

A series of four papers using data from NASA’s Juno mission reveals intriguing information about Jupiter, including its gravitational field, its atmospheric flows, its interior composition and its polar cyclones.

Jupiter’s winds are tightly connected to the planet’s gravitational and magnetic fields. Image credits: NASA / ESA / UC Berkeley.

When the Juno mission was successfully launched in 2011, astronomers worldwide were thrilled. The shuttle had the potential to reveal valuable information about Jupiter and its satellites — and that potential has been thoroughly fulfilled. The new papers are the latest in a long chain of remarkable findings about the most massive planet in our solar system, adding some much-needed pieces to the puzzle.

In the first paper, researchers led by Luciano Iess of the Sapienza University of Rome in Italy used Doppler data to study Jupiter’s gravitational field. The data allowed researchers to measure Juno’s velocity down to 0.01mm/s accuracy, even while the shuttle is traveling at speeds of up to 70 km/s in orbit.

Jupiter’s gravitational field is famously asymmetrical, which is unusual for fast-rotating and oblate (squashed at the poles) gas giants. This gravitational asymmetry is caused by hydrogen-rich gas is flowing asymmetrically deep in the planet, and Juno was able to study this process.

This picture of the Jupiter’s South Pole is a mosaic of many images acquired by the Jovian InfraRed Auroral Mapper on board the Juno shuttle. The images have been taken in different times while Juno was leaving the planet after the closest approach. What you see here is the heat (measured as radiance) coming out from the planet through the clouds: yellow indicates the presence of thinner clouds and dark red the thicker ones.
Credit: NASA/SWRI/JPL/ASI/INAF/IAPS

Two other papers looked at different physical parameters of Jupiter. A team led by Yohai Kaspi of the Weizmann Institute of Science in Israel used another asymmetry, that of Jupiter’s magnetic field, to calculate the depth of Jupiter’s atmosphere, finding that the mass of the atmosphere amounts for about 1% of the planet’s total mass. Meanwhile, Tristan Guillot and co-authors report that at depths greater than 3,000 kilometers below cloud level, Jupiter’s deep interior is made up of a fluid mixture of hydrogen and helium, rotating as a solid body. They also found that the speed of the above-mentioned winds extend some 3,000 km beneath the cloud level, dropping in intensity with altitude.

Even with all this information, we’re still just barely scratching the surface of what we know about Jupiter.

“We’re at the beginning of dissecting Jupiter,” says Juno mission leader Scott Bolton of the Southwest Research Institute in San Antonio.

However, there’s also a downside to the Juno mission: it offered so much valuable data that it’s gonna be very hard to top it. In an accompanying News&Views article, planetary scientist Jonathan Fortney of the University of California Santa Cruz praised the work, writing:

“The work demonstrated here is extremely robust,” Fortney wrote in his editorial. “I do not foresee another leap in knowledge on Jupiter’s interior after the Juno mission ends, unless astronomers are able to study the planet’s internal oscillations, as has been done for the Sun.”

Fortunately, Juno will remain in orbit for at least a couple of years, so we’ll certainly have more to learn about Jupiter.

Journal References:

  1. Measurement of Jupiter’s asymmetric gravity field. Corresponding Author: Luciano Iess (Sapienza Università di Roma, Rome, Italy). DOI: 10.1038/nature25776. http://nature.com/articles/doi:10.1038/nature25776
  2. Jupiter’s atmospheric jet streams extend thousands of kilometres deep. Corresponding Author: Yohai Kaspi (Weizmann Institute of Science, Rehovot, Israel). DOI: 10.1038/nature25793. http://nature.com/articles/doi:10.1038/nature25793
  3. A suppression of differential rotation in Jupiter’s deep interior. Corresponding Author: Tristan Guillot (Université Côte d’Azur, Nice, France). DOI: 10.1038/nature25775. http://nature.com/articles/doi:10.1038/nature25775
  4. Clusters of cyclones encircling Jupiter’s poles. Corresponding Author: Alberto Adriani (INAF-Istituto di Astrofisica e Planetologia Spaziali, Rome, Italy). DOI: 10.1038/nature25491. http://nature.com/articles/doi:10.1038/nature25491
Mercury close to sun.

The Sun is slowly losing mass as it ages, weakening its grip on the planets

The Sun is losing its gravitational lock on the solar system, new research has found.

Mercury close to sun.

Image credits NASA/SDO.

The planets in our solar system are expanding their orbits, according to a team of NASA and MIT scientists. This drift is caused by the Sun slowly losing mass as it ages, which weakens its gravitational pull. The researchers studied Mercury’s orbit to indirectly measure the amount of mass our star lost.

Midlife crisis

The study began with the team refining Mercury’s ephemeris — its course around the Sun, charted over time. Scientists have been studying this planet and recording its position for centuries now, paying particular attention to its perihelion, the point in its orbit when it comes nearest the Sun.

Because we’ve had such a long observation period of the planet, we know that Mercury tends to shift its perihelion over time — a movement called precession. Part of the cause lies in other planets in the solar system, whose gravitational pulls gently tug at the scorched ball of rock. However, they don’t account for all of the observed precession. Most of what’s left, Einstein tells us, can be explained by the Sun’s mass warping space-time around it — this effect actually helped confirm the theory of general relativity.

But a small part of that precession motion comes down to tiny changes in the Sun’s internal structure and processes. Among them is the Sun’s oblateness (how much it bulges at the equator due to its spin). It was this last category of influences on Mercury’s precession that the team studied.

The researchers drew on radio data which tracked the position of NASA’s MESSENGER spacecraft (Mercury Surface, Space Environment, Geochemistry, and Ranging) while the mission was active. The vessel made three flybys over Mercury in 2008 and 2009 and subsequently orbited the planet from March 2011 through April 2015. By analyzing all the subtle changes in the planet’s motions throughout that time, the team could infer how the Sun’s physical parameters influence Mercury’s orbit.

Mercury Sun.

The position of Mercury over time was determined from radio tracking data obtained while NASA’s MESSENGER mission was active.
Image credits NASA / Goddard Space Flight Center.

They were able to separate some of these parameters from the star’s relativistic effects, something which previous research that looked at Mercury’ ephemeris never managed to do. At the same time, they developed a new analytical method that simultaneously estimated and integrated the orbits of Mercury and the MESSENGER craft. The end result is a solution which takes into account both relativistic effects and processes inside the Sun.

“Mercury is the perfect test object for these experiments because it is so sensitive to the gravitational effect and activity of the Sun,” said lead author Antonio Genova.

The researchers obtained an improved estimate of oblateness that is consistent with other types of studies. However, their estimate of the rate at which the Sun loses mass represents one of the first times this value was based on observation rather than calculated through secondary data. Previously, scientists predicted a one-tenth of a percentage loss of the Sun’s mass over 10 billion years — corresponding to any planet widening its orbit by 1.5 cm (0.5 in) per year per AU (one AU, or astronomical unit, is the distance between the Earth and the Sun).

The team’s observations by-and-large reinforce that estimate — their result is just slightly lower, but being based on observation it is much less uncertain. The team’s results also allowed them to more accurately pin the value of G, the gravitational constant, improving its stability by a factor of 10 compared to previous, estimated values.

“We’re addressing long-standing and very important questions both in fundamental physics and solar science by using a planetary-science approach,” said Erwan Mazarico, paper co-author.

“By coming at these problems from a different perspective, we can gain more confidence in the numbers, and we can learn more about the interplay between the Sun and the planets.”

The paper “Solar system expansion and strong equivalence principle as seen by the NASA MESSENGER mission” has been published in the journal Nature Communications.

The Power of Gravity and Its Capabilities

Gravity is a fundamental force. A force is best defined in the realm of science as a push or a pull that can change an object’s movement. This relation can be exemplified in a piece of pop culture that everyone can recognize — Star Wars. In the films, the “force” allows its users to push things away from them or draw (pull) things toward them. In the case of gravity, it is a force which pulls things toward each other.

The Force in Star Wars is a bit different from real-life gravity, though.

There are just two factors which affect the gravity’s strength in any circumstance: the mass of each object being attracted to one another, and the amount of space between each object. The three other fundamental forces active in our universe are electromagnetism, strong force, and weak force. Out of all of them, gravity is actually considered the weakest (to put it in perspective, electromagnetism is approximately a trillion-trillion-trillion times more powerful than gravity; it sounds ridiculous, but it’s true).

Yet gravity is the fundamental force that human beings usually come in contact with on a daily basis. It keeps us sitting down and makes people and objects fall to the ground. It binds the moon orbiting around Earth and other planets orbiting around the Sun. Gravity is a quality of all matter in the universe.

In addition, gravity is the key force in the scientific field of astronomy — the study of the universe outside the Earth’s atmosphere. Galileo Galilei and Sir Isaac Newton, both groundbreaking scientists of the 17th century, studied gravity as well as the planets and stars. In modern terms, the acceleration due to the gravity at the surface of the Earth is equivalent to what is now referred to as ‘one g’. G-force is the interaction of gravity on any celestial body.

Gravity actually had a big hand in forming a lot of the beauty found in the ever-expanding universe. Gravity pulls on an object from all directions simultaneously, thus forming objects in the shape of a sphere. This explains why common extraterrestrial bodies, such as planets and stars are round, spherical objects. Gravity is also a major driving force in the origin of galaxies.

Believe it or not, this is what the Earths’ gravitational field looks like. Image credits: NASA.

 

Nebulae, clouds of dust and gas (typically hydrogen and helium), are drawn together by gravity. This force then causes these compact clouds to collapse and begin rotating. The offspring of such structuring is usually a new galaxy. Just as gravity takes part in the birth of light and beauty, it also assists in the demolition of it. As already mentioned, gravity is the force which pulls objects together. It causes many extraterrestrial bodies to collide, often leading to the destruction of one or all of the objects involved.

One such collision was very recently observed and recorded. In an article published by National Geographic on October 16, 2017, it was released that an astronomical and historical event had been witnessed by a number of astronomers worldwide: a kilonova, a collision of two neutron stars. What is likely to be the most significant aspect of this occurrence is that the massive confrontation of the two stars allowed for detectable gravitational waves to be studied and their point of origin to be located.

Theorized as early as 1916 by Einstein, gravitational waves are actually distortions of space-time brought about via rather powerful astronomical events. Considered in a hypothetical context for decades, the first signs of proof to back a belief in gravitational waves were discovered in the early to mid-1970’s. But through this most recent incident, scientists were able to trace the gravitational waves to their source. We can see the pattern in which they move.

Gravity attracts things; it assists in the creation as well as the destruction of matter. It is the force which keeps the sun blazing. It quite literally makes the world go round. It keeps our feet firm on the ground. And without it, almost nothing would be within our reach.

By ZME reader John Tuttle. Are you a scientist, expert, student, or an artist? Do you want to share your work with the world? Learn how anyone who has something interesting to say can contribute to ZME Science. 

Physicists report new, solid observation of gravitational waves

It’s pretty much official now: there are gravitational waves. A collaboration between the LIGO Lab and the Virgo interferometer collaboration just reported the first joint detection of gravitational waves, adding much more weight to previous detection events.

Image credits: NASA/Ames Research Center/C. Henze.

Virgo had just been switched on

It’s not the first time gravitational waves had been detected. Physicists had recorded three previous events, offering serious proof to support the hypothesis first proposed by Albert Einstein a hundred years ago. Both the LIGO and Virgo detectors picked up the same event — a binary black hole system colliding. Together, the two observers provided 3D detail of the gravitational warping caused by the collision. To make things even more exciting, this comes just after Virgo had been switched on. It basically observed gravitational waves on its trial run.

“This is just the beginning of observations with the network enabled by Virgo and LIGO working together,” says David Shoemaker of MIT, LSC spokesperson. “With the next observing run planned for Fall 2018 we can expect such detections weekly or even more often.”

“It is wonderful to see a first gravitational-wave signal in our brand new Advanced Virgo detector only two weeks after it officially started taking data,” says Jo van den Brand of Nikhef and VU University Amsterdam, spokesperson of the Virgo collaboration. “That’s a great reward after all the work done in the Advanced Virgo project to upgrade the instrument over the past six years.”

Gravitational waves are basically ripples in the curvature of spacetime, generated in certain gravitational interactions. They propagate as waves outward from their source, at the speed of light. However, in order for us to observe them, we need dramatic interactions between the most massive objects we know of: black holes. Even these dramatic events send only a tiny observable wobble, which require finely tuned detectors, the likes of which only LIGO and Virgo provide. That two facilities, functioning independently, confirmed the same thing is highly encouraging.

“Little more than a year and a half ago, NSF [National Science Foundation] announced that its Laser Gravitational-Wave Observatory had made the first-ever detection of gravitational waves resulting from the collision of two black holes in a galaxy a billion light-years away,” says France Córdova, NSF director. “Today, we are delighted to announce the first discovery made in partnership between the Virgo Gravitational-Wave Observatory and the LIGO Scientific Collaboration, the first time a gravitational-wave detection was observed by these observatories, located thousands of miles apart. This is an exciting milestone in the growing international scientific effort to unlock the extraordinary mysteries of our Universe.”

Thanks to slightly different fine-tuning, the two observers allow researchers to observe different characteristics of the waves. Specifically, Virgo’s arms are angled differently than the two Ligo detectors, which allows it to extract new information about the polarisation of gravitational waves. This is extremely important because previous observations from LIGO came from two detectors with a parallel orientation. Vigo’s arms come at a different angle (an intentional design feature), allowing researchers to get a more 3D view of what’s happening.

“It’s like if I give you just one slice of apple, you can’t guess what the fruit looks like,” said Prof Andreas Freise, a Ligo project scientist at the University of Birmingham. “When you see things from different angles, suddenly you can see the 3D shape as well,” he said. “Einstein’s theory of what [the waves] look like is pretty clear.”

Although Henri Poincaré first suggested that in analogy to an accelerating electrical charge producing electromagnetic waves, gravitational waves are tightly associated to Albert Einstein, who first predicted their existence in 1916, in his famous general theory of relativity. His mathematical equations showed that massive accelerating objects (namely neutron stars or black holes orbiting each other) would disrupt the fabric of space-time, sending waves in the process, much like a stone thrown into a pond sends ripple in the water. However, later on in his work, Einstein started to doubt their existence. In 1936, Einstein and Nathan Rosen submitted a paper to Physical Review in which they argued that the gravitational waves could not exist in the full theory of general relativity. The paper was anonymously reviewed by mathematician Howard P. Robertson, who pointed out some miscalculations within the paper. Furious, Einstein withdrew the paper, but ultimately, one of his assistants, who had been in contact with Robertson, convinced Einstein that the criticism was correct. They rewrote the paper, but with exactly the opposite conclusions, supporting the existence of gravitational waves.

Gravity map reveals Martian crust might be lighter than we thought

This could help us better understand the Red Planet and its evolution.

A gravity map of Mars. Martian gravity can reveal a lot of the planet’s secrets, especially those of its crust. Credits: NASA/Goddard/UMBC/MIT/E. Mazarico.

Gravity on our planet isn’t uniform at all. Sure, it might seem that way to our human senses, but there are lots of variations, depending on the Earth’s subsurface and variations in its shape. For instance, denser rocks will lead to a slightly stronger gravitational field, whereas those with pores or voids lead to a weaker local field.

We’ve long created general gravity maps of the Earth and even localized, detailed maps. Even the Moon has been charted in detail, using NASA’s GRAIL mission, which sent two space probes to study the field. Since gravity decreases with distance, things closer to the surface have a stronger impact than things deeper in the underground, and now we have a significantly better understanding of the Moon’s crust (which has a more pronounced effect on the gravity field).

In fact, crustal density and gravity have many things in common — we can derive one from the other, through a sophisticated mathematical process called inversion. Map the gravitational field, and you’ll learn a lot about the density — you could even build a density model, as we’ve done for Earth. But using the same approach with Mars would be difficult because we just don’t have enough data, so NASA had to try a different strategy.

They used what little gravitational information we have about Mars, relying on what little we learned directly about the Martian surface and even more on the topography of the planet. They learned that Mars has a lighter crust than what was expected, based on what we know of the rocks’ composition. Researchers were expecting rocks about as dense as the oceanic crust here on Earth, but they came up with less than that.

“As this story comes together, we’re coming to the conclusion that it’s not enough just to know the composition of the rocks,” Greg Neumann, a researcher on the project, said in a statement. “We also need to know how the rocks have been reworked over time.”

The final density figure is 2,582 kilograms per meter cubed (about 161 pounds per cubic foot). That’s comparable to the average density of the lunar crust and significantly less than Earth’s oceanic crust, which is about 2,900 kilograms per meter cubed (about 181 pounds per cubic foot). This seems to indicate that the main culprit for this difference, the crust, is more porous than we initially thought.

“The crust is the end-result of everything that happened during a planet’s history, so a lower density could have important implications about Mars’ formation and evolution,” said Sander Goossens of NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Goossens is the lead author of a Geophysical Research Letters paper describing the work.

Before publishing these results, they tested their method using data from the GRAIL mission and came up with accurate results. They also correlated positive anomalies (stronger gravitational field) to known volcanoes, something which was expected. But the approach they used doesn’t have a good resolution, so we’ll have to wait for more data to confirm these findings.

The researchers also note that NASA’s InSight mission — short for Interior Exploration using Seismic Investigations, Geodesy and Heat Transport — will carry out the measurements which could confirm their finding. This Discovery Program mission, scheduled for launch in 2018, will place a geophysical lander on Mars to study its deep interior.

You can study the model and even download on this page from NASA’s website.

Journal Reference: Sander Goossens, Terence J. Sabaka, Antonio Genova, Erwan Mazarico, Joseph B. Nicholas, Gregory A. Neumann. Evidence for a low bulk crustal density for Mars from gravity and topography. DOI: 10.1002/2017GL074172

A flat-earther brought a spirit level on a plane to prove the Earth is flat. Yeah…

A Youtuber and conspiracy theorist from the US has taken pseudoscience to the next level — literally. He took a spirit level onto a plane, hoping to convince people that the Earth is flat.

This is the Earth. Some people believe it is flat.

That people still claim the Earth is flat is simply stunning to me. It’s not just watching ships sail off in the horizon or looking at constellations, we have gone into outer space and looked at the Earth. Heck, we have a massive research outpost, the International Space Station, constantly revolving around the planet and snapping photos. In this day and age, this level of ignorance is simply not allowed, even if you’re one of the greatest basketball players of all time. But back to our guy.

D Marble decided to take his spirit level to a plane. In case you’re not familiar with a spirit level, it’s an instrument designed to indicate whether a surface is horizontal or whether it dips. It has a slightly curved vial incompletely filled with a liquid so that an air bubble remains. When the surface is completely flat, the bubble rests exactly in the middle.

A spirit level. Image via Wikipedia.

He thought this would show the Earth has no curvature and that it is essentially flat:

“I recorded a 23 minute and 45 seconds time-lapse, which by those measurements means the plane travelled a little over 203 miles. According to curvature math given to explain the globe model, this should have resulted in the compensation of 5 miles of curvature. As you’ll see there was no measurable compensation for curvature.”

It’s not just the flat Earth that he was trying to prove — he also took a jab at gravity…

“Understand that gravity is a still just a theory,” he goes on to say. “No more defending what we know to be true! Now we take the fight to the enemy! #FEOffensive.”

We’ll give him a lot of creativity points, but he scores a big fat zero on the science scale. Try to figure it out for a moment. You can come up with a number of valid arguments, ranging from middle school physics to simple, common sense.

For starters, the spirit level requires a lot of stillness for the bubble to align, which plane travel can’t really ensure. Twitter was quick to point this one out.

If you want a more elegant approach, you could say that even if (theoretically) the plane would have been perfectly still and moved in a perfect way, the experiment still couldn’t have worked because that’s not how gravity works — his entire premise of curvature compensation is flawed. Twitter was all over this one as well.

Lastly, for crying out loud, the man was traveling on a plane, you’d expect he’d at least look out the window.

This really sums up perfectly the anti-intellectual and anti-scientific trend so prevalent in the US and the world: a man using a plane (developed with science) uses an instrument (developed through science,) then shares his opinion on an Internet platform (made possible through science) from a device built through science, to share anti-scientific opinions. He uses a badly-devised experiment and can’t even understand basic principles but hey, people are buying it so why not?

His initiative was well-received by other flat-Earthers — which doesn’t even come as a surprise by this point.

Take a moment and think that in the 21st century, when we are sending shuttles to the Moon and to Mars, when we are toying with the genetic make-up of the human body, when we are zooming closer towards understanding the fabric of the Universe, people are saying the Earth is flat on Youtube. What a world we live in.

Here’s the whole video, already with over 200,000 views, having been shared by several flat Earth societies, including Flat Earth ActivismGod’s Flat Earth and various other globe-deniers. Yes, there are societies like these all around the globe (heh).

 

Astronomers discover the first “middleweight” black hole

Generally speaking, black holes fall into two categories: small, with a mass comparable to that of the Sun, or supermassive, weighing millions or even billions of Suns. Researchers have postulated that middleweight black holes should also exist but were unable to actually find one — until now.

An artist rendition of the newly discovered middleweight black hole. New research suggests that a 2,200 solar-mass black hole resides at the center of the globular cluster 47 Tucanae.
Credit: CfA / M. Weiss

When most black holes are discovered, astronomers see X-rays coming from a hot disk of material swirling around it, but this only works if the black hole is actively feeding on nearby gas. Supermassive black holes can also identified by the gravitational effect they have on nearby stars, but that also only works in a limited number of cases. There’s a good chance that many black holes don’t respect either of these criteria and there may be a swarm of them lying undiscovered in our galaxy. Harvard astronomers have been on the lookout for such intermediate-sized black holes.

“We want to find intermediate-mass black holes because they are the missing link between stellar-mass and supermassive black holes. They may be the primordial seeds that grew into the monsters we see in the centers of galaxies today,” says lead author Bulent Kiziltan of the Harvard-Smithsonian Center for Astrophysics (CfA).

They focused on a globular cluster called 47 Tucanae,  located in the constellation Tucana, about 16,700 light years away from Earth, and 120 light years across. It can even be seen with the naked eye as it contains thousands of stars, as well as about two dozen pulsars. It’s not the first time 47 Tucanae has been investigated in the hope of finding a black hole at its center, but previous attempts have not been successful. Now, two pieces of evidence indicate the existence of such a black hole.

The first clue is the overall motion of the stars throughout the cluster. The globular cluster is so dense with stars that the big ones fall towards the center while the other ones spin around. The extra gravity from the black hole acts like a spoon “stirring the pot” of stars — causing them to slingshot faster and over greater distances. This change, even though subtle, is measurable. The second line of evidence comes from the pulsars mentioned above.

Pulsars are highly magnetized, rotating neutron stars or white dwarfs. The radio signals these pulsars emit are very recognizable and easy to detect by astronomers. These objects are also flung by the black hole’s gravity and are much farther from the center of the cluster than you’d expect.

So although we can’t see the black hole directly, we get a good glimpse of its gravity effect. Kiziltan believes the black hole has a mass of about 2,200 solar masses, which would make it a perfectly fit for the middleweight category they were looking for. The team now wants to look in similar clusters, to see if a similar analysis could reveal other hidden black holes.

Journal Reference: Bülent Kızıltan, Holger Baumgardt, Abraham Loeb. An intermediate-mass black hole in the centre of the globular cluster 47 Tucanae. Nature, 2017; 542 (7640): 203 DOI: 10.1038/nature21361

pluto heart

Pluto’s ‘heart’ might be filled with an ocean of liquid water

We’ve learned a lot from New Horizons’ flybys of Pluto, such as confirming it has an active geology, a climate, and almost certainly many more secrets waiting to be found. One of them might be an ocean of liquid water buried beneath Pluto’s thick nitrogen ice surface.

pluto heart

Credit: NASA/APL/SwRI

When New Horizons beamed back its best photos of the dwarf planet, it also showed to the world the largest geological feature on Pluto — a bright, heart-shaped Tombaugh Regio. In the western part of ‘the heart’ as it’s also called, lies the Sputnik Planum lobe, which is a 1000-km-wide plain of nitrogen and other ices.

Evidence suggests that Sputnik Planum was created by a giant impact with a cosmic body at least 200 kilometers across. Subsequently, this cataclysmic event should have displaced enough material to cause a negative gravitational anomaly because a crater is nothing but a big hole in the ground — less mass means less gravitational pull. At least, that’s what ought to have happened.

Instead, Sputnik Planum bears a positive gravitational anomaly which means something is filling that crater, and a team from Brown University think it’s liquid water.

“Thermal models of Pluto’s interior and tectonic evidence found on the surface suggest that an ocean may exist, but it’s not easy to infer its size or anything else about it,” said Brandon Johnson, who is an assistant professor in Brown’s Department of Earth, Environmental and Planetary Sciences. “We’ve been able to put some constraints on its thickness and get some clues about composition.”

Like Earth and the Moon, Pluto and its largest moon Charon are tidally locked, meaning the two always show the same face as they rotate. This happened over time and as Charon’s gravity pulled proportionately more on areas of higher mass, the two bodies became aligned on a tidal axis. Sputnik Planum sits directly on this tidal axis.

After the impact, the massive crater could have been filled with nitrogen with ice progressively layering on top of each other. But that couldn’t have been enough to cause the positive gravitational anomaly. Instead, what the Brown University researchers think happened was that liquid water, which is denser than ice, upwelled following the impact and evened the crater’s mass. Then, the nitrogen ice deposited on top of this liquid water would have been enough to explain the positive gravitational anomaly.

“This scenario requires a liquid ocean,” Johnson said. “We wanted to run computer models of the impact to see if this is something that would actually happen. What we found is that the production of a positive mass anomaly is actually quite sensitive to how thick the ocean layer is. It’s also sensitive to how salty the ocean is, because the salt content affects the density of the water.”

The computer models suggest this tentative layer of liquid ocean ought to be more than 100 kilometers thick, with a salinity of around 30 percent, as reported in Geophysical Research Letters

“What this tells us is that if Sputnik Planum is indeed a positive mass anomaly —and it appears as though it is — this ocean layer of at least 100 kilometers has to be there,” Johnson said. “It’s pretty amazing to me that you have this body so far out in the solar system that still may have liquid water.”

Too big to orbit: Jupiter is so massive it doesn’t actually orbit the Sun

The fifth planet from the Sun and owner of the most iconic stormy swirl in the Solar Sistem, Jupiter is nothing if not massive. So massive, in fact, that the planet doesn’t simply orbit our sun, but drags it along for the ride.

Image via pixabay

What?

It’s all a matter of physics and Newton’s universal law of gravitation. It’s the one which says objects pull on each other with a force proportional to the product of their masses and inversely proportional to the square of the distance between them. So more mass means a stronger gravitational pull, but as you move away from said mass this pull drops exponentially. This is why gravity can keep your feet on the ground but isn’t strong enough to pull every comet in the universe down on our heads.

Now because of this, in theory, whenever two objects in space meet and start orbiting, it’s not one body going round a fixed other — they both move around a central point whose position is determined by the relative masses of the objects. Think of how the Moon causes ebb and flow. It also pulls on the rocks and soil that make up our planet, pulling it as a whole towards the Moon. The ISS also pulls on Earth with its own very weak gravitational field. In both cases, the centre of gravity is so close to our planet’s centre that the effect is negligible. Earth doesn’t seem to move, and the Moon and ISS make perfect circles around it.

When talking about out neighbouring planets, the gravitational centre is so close to the Sun’s centre that we don’t even bother with it. Not even Saturn has a noticeable effect on its position in space. So, for all intents and purposes, we consider the centre of the Sun to be the point around which everything in our system orbits around.

Except Jupiter, Tech Insider reports.

Because of the sheer mass of the gas giant (Jupiter has two and a half times the mass of all other planets in the solar system combined) it’s centre of mass with the Sun is 1.07 solar radii outside the middle of the star. So the central point around which both Jupiter and the Sun orbit, the “barycenter” as it is known, lies 7 percent of the Sun’s radius above its surface. Both the Sun and Jupiter orbit around that point in space.

This gif NASA put together shows what I’m talking about.

This is, in essence, how Jupiter and the Sun move through space together – though the distances and sizes aren’t to scale. Jupiter is still only a fraction of the Sun’s size.

The moon’s phases affect rainfall, says first-of-its-kind study

The moon does more than cause tides and delight lovers – according to a new study, it can also affect how much rainfall falls down on the ground.

Image via Wikipedia.

Since ancient times, the moon has been an object of fascination for people, both romantics and scientists. Now, researchers from the University of Washington found that when the moon is high in the sky, it creates “bulges” in the planet’s atmosphere, slightly affecting falling rain. This is the first study to document the effect of the moon on rainfall.

“As far as I know, this is the first study to convincingly connect the tidal force of the moon with rainfall,” said corresponding author Tsubasa Kohyama, a UW doctoral student in atmospheric sciences.

 

Satellite data over the tropics, between 10 degrees S and 10 degrees N, shows a slight dip in rainfall when the moon is directly overhead or underfoot. University of Washington

He started noticing something was up while studying atmospheric waves, periodic disturbances of pressure, temperature or wind velocity. He noticed slight, but consistent oscillations in the air pressure. He and co-author John (Michael) Wallace, a UW professor of atmospheric sciences, spent the next two years tracking these oscillations and attempting to explain them.

It’s not the first time atmospheric variations have been tied with the moon. Air pressure changes were connected to the phases of the moon back in 1847 and temperature in 1932. Furthermore, a 2014 paper from the same University showed how air pressure varies with the phases of the moon.

“When the moon is overhead or underfoot, the air pressure is higher,” Kohyama said.

After that, it seemed highly likely that rainfall is also affected by the moon, and this did turn out to be the case. When the satellite is overhead, its gravitational attraction tugs and pulls a slight damper on the rain. Higher pressure also creates warmer temperatures in the air parcels below. Warmer air holds more moisture, and having a higher moisture capacity means they don’t shed as much water.

“It’s like the container becomes larger at higher pressure,” Kohyama said. The relative humidity affects rain, he said, because “lower humidity is less favorable for precipitation.”

They used data collected from 1998 to 2012 to show that the rain is indeed slightly lighter when the moon is high. It’s a very slight and subtle change, of only about 1% total rainfall. It is consistent, but you shouldn’t really worry about it.

“No one should carry an umbrella just because the moon is rising,” Kohyama said.

However, this could have an effect on weather and climate models. It’s another valuable piece of information to piece into extremely complicated prediction models. Wallace plans to continue exploring the topic to see whether specific types of rain are more affected by lunar phases.

Journal Reference [open access] – Rainfall variations induced by the lunar gravitational atmospheric tide and their implications for the relationship between tropical rainfall and humidity.

fire-zerogravity

How fire burns in zero gravity

In space, of course, you can’t have any fires because there isn’t any oxidizer (i.e. oxygen) to sustain the combustion process. Inside a spacecraft or in the International Space Station, however, things are a bit different: you have the same air mixture as on Earth, but because gravity is millions of times weaker, an open flame behaves significantly different.

Lighting a candle in space

fire-zerogravity

Left: a candle flame in normal gravity; right: a candle flame in microgravity. Image: Science.

 

First, let’s see how combustion works here on Earth. Imagine a big bonfire, beautifully blazing away in the mountainside, with you and your best friends roasting some marshmallows. For a moment, you ponder the fire itself. How does it all work? As carbon and oxygen molecules revolve around your head, you begin to understand. As the fuel (wood) burns, it heats the air around it making it less dense. Because gravity pulls down anything with a higher density, the hot air travels upwards and leaves the vicinity of the fire, which is very convenient. With the hot air gone, fresh air is drawn into the gap providing a new source of oxygen-rich air.

This is called buoyancy and is what makes the flame shoot up and flicker. Thus, the cycle continues until all the fuel is used up. In microgravity, however, things are a lot different.

fire in microgravity

fire in microgravity

In microgravity, there’s no updraft and oxygen is drawn into the flame through a completely different mechanism. The first such experiment was performed in 1997 aboard the Columbia shuttle. Called Structure of Flame Balls at Low Lewis-number (SOFBALL), the experiment consisted of a sealed chamber where flames flying onboard the space shuttle can burn for a long time.

 

 A schematic diagram of a flame ball. Credit: Paul Ronney.

A schematic diagram of a flame ball. Credit: Paul Ronney.

The first thing scientists noticed was the shape of the flame. While on Earth a fire’s flame is elongated, in microgravity it is spherical – like a fireball. That’s because the spherical flame is fed by the slower process of diffusion, so the flame occurs at a border between fuel and air; effectively the entire surface of the flame is the “bottom”, reacting with fresh air close enough to the fuel source to combust, in a rough sphere. Because exhaust gases like CO2 can’t leave the combustion area, by the same dictum, the outward diffusion of combustion gases can limit the inward diffusion of oxygen to an extent that the zero gravity flame will die a short time after ignition.

You might have also noticed from the pictures in this article that fire has a different color in microgravity. When a candle burns, it’s being consumed molecule by molecule. Sometimes, the fuel — long strings of carbon — gets pushed upwards where it burns like charcoal, glowing yellow. Without gravity, the carbon strings don’t get burned, and the flame is blue, cooler, and much much dimmer.

Studying fire in microgravity can render some important practical insight. For decades engineers have been trying to build internal combustion engines that run on a lean mixture of fuel and oxygen, which should produce something like a flame ball in space.  If you could burn a leaner fuel mixture in engines, you could get higher fuel efficiency and lower pollutant formation, says Paul Ronney, a combustion researcher at the University of Southern California who conceived and helped design the shuttle flame experiments. Because the chemical reaction rates involved in combustion are very sensitive to temperature, if you increase the temperature by 10 percent, the rate more than doubles — and the rate at which some pollutants form increases thirteenfold, particularly the oxides of nitrogen that make our skies brown.

Then, of course, there’s the issue of safety. Because fire behaves considerably different in microgravity than in Earth’s gravity, studying fireballs is very important to designing safety measures and systems. For instance, if a candle is burning on Earth you might think about stomping it to put down the flame. If you were to do that in a spacecraft, you might accelerate combustion, at least temporarily, because you are creating an airflow that did not exist before. Flames in low-gravity tend to spread slowly, so stomping might cause a flame to jump to something else when it wouldn’t have otherwise. Furthermore, flame balls are stealthy: they give off no smoke and little or no visible light. It’s very hard to extinguish something you can’t find.

A new gravity model gives us the clearest picture of the world's seabed up to now.

Most detailed Map of the Seafloor yet exposes Thousands of New Mountains

The Scripps Institution of Oceanography at UC San Diego has released a new map of the world’s seafloor – the first in nearly 20 years – which exposes new terrain, including thousands of mountains. The unprecedented detail was attained using radar satellites that captures gravity measurements of the ocean seafloor. Armed with this more precise understanding of what lies beneath the world’s oceans, scientists can now establish more sophisticated and accurate climate models, as well as gain new clues on how the continents as they stand today formed past the eons.

The map of a watery world

A new gravity model gives us the clearest picture of the world's seabed up to now.

A new gravity model gives us the clearest picture of the world’s seabed up to now.

Mapping the surface of our planet’s seabed is a very important job, but also a highly challenging one. Scientists can not perform this job using the same tools for mapping mountains, hills and other terrain above sea level, since seawater is opaque to these methods. A really accurate reading can be achieved by ships carrying echosounders which bounce off sounds from the watery depths below, but it would take too much time and money to do this for the whole world’s seabed. Many features are also hidden by sediments, which renders sonar ineffective in this case. Generally, researchers turn to this technique when they really want to have a fine grained picture of the ocean’s bottoms, for a given area for different purposes. On a planetary scale, radar satellites are much more effective, though.

[ALSO READ] 39 unbelievable underwater pictures that will blow your mind

Dietmar Müller from the University of Sydney said: “You may generally think that the great age of exploration is truly over; we’ve been to all the remotest corners of continents, and perhaps one might think also of the ocean basins. But sadly this is not true – we know much more about the topography of Mars than we know about the seafloor.”

Mapping gravity

gravity_map

A new seafloor map reveals fracture zones which tell scientists about the movement of the continents.

Satellites fitted with radar altimeters can infer the surface of the ocean bottom from the surface of the water high above. Because water follows gravity, it is pulled into highs above the mass of tall seamounts, and slumps into depressions over deep trenches. Key insight such as this made the gross maps we now have at our disposal, but advances in satellite technology  have brought a two-fold improvement in the gravity model used to describe the ocean floor. This was possible thanks to data sets from the European Space Agency’s (ESA) CryoSat-2 satellite, which primarily captures polar ice data but also operates continuously over the oceans, and Jason-1, NASA’s satellite that was redirected to map the gravity field during the last year of its 12-year mission.

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Already, despite the work is far from finished, we can see an exponential growth in the detail available to us.

“In the previous radar dataset we could see everything taller than 2km, and there were 5,000 seamounts,” Prof Dave Sandwell, a Scripps Institution of Oceanography researcher.

“With our new dataset – and we haven’t fully done the work yet – I’m guessing we can see things that are 1.5km tall.

“That might not sound like a huge improvement but the number of seamounts goes up exponentially with decreasing size.

“So, we may be able to detect another 25,000 on top of the 5,000 already known,” he went on to explain.

The new map also gives geophysicists new tools to investigate ocean spreading centers and little-studied remote ocean basins.

“The kinds of things you can see very clearly now are abyssal hills, which are the most common land form on the planet,” said David Sandwell, lead scientist of the paper and a geophysics professor in the Cecil H. and Ida M. Green Institute of Geophysics and Planetary Physics (IGPP) at Scripps.

The newly released map now comes as a great tool for geophysicists looking to investigate remote ocean basins or ocean spreading centers. Abyssal hills – the most common land form on Earth – can now be more clearly discerned. These structures significantly influence oceans currents, and thus the climate. They’re also important to conservation efforts and fishery research since it’s around these kind of terrain that marine life tends to congregate.

The research also offers new insights into the tectonics of the deep oceans. For instance, the map has exposed a previously uncharted continental connection across South American and Africa – a different type of ridge feature that became separated roughly 85 million years ago .

What’s amazing is that one of the satellites used for the mapping, ESA’s Cryosat, was actually tasked with the primary mission of tracing the shape and thickness of polar ice fields – not the seabed. The technology onboard the satellite, however, proved to be invaluable for marine floor probing – something that became clear as soon as it took orbit.

“The team has developed and proved a powerful new tool for high-resolution exploration of regional seafloor structure and geophysical processes,” says Don Rice, program director in the National Science Foundation’s (NSF) Division of Ocean Sciences. “This capability will allow us to revisit unsolved questions and to pinpoint where to focus future exploratory work.”

“The use of satellite altimeter data and Sandwell’s improved data processing technique provides improved estimates of marine gravity and bathymetry world-wide, including in remote areas,” said Joan Cleveland, Office of Naval Research (ONR) deputy director, Ocean Sensing and Systems Division. “Accurate bathymetry and identifying the location of seamounts are important to safe navigation for the U.S. Navy.”

The paper was reported in Science.

 

 

 

 

BICEP2 (in the foreground) and the South Pole Telescope (in the background). Credit: Steffen Richter, Harvard University

Gravity waves laid to dust: when scientists get way ahead of themselves

BICEP2 (in the foreground) and the South Pole Telescope (in the background). Credit: Steffen Richter, Harvard University

BICEP2 (in the foreground) and the South Pole Telescope (in the background). Credit: Steffen Richter, Harvard University

Nobel prizes, international press coverage, awards – these were all promises and cheers thrown about all over the web after a team of physicists trumpeted during a conference at Harvard that they’ve made one of the biggest discoveries in science: gravity waves. Some theories claim that these waves were generated brief moments following the Big Bang, and a team of researchers based at the  BICEP2 facility in Antarctica claimed during the aforementioned press conference in March that they’ve finally confirmed the models and have discovered evidence that support gravitational waves. A week ago, however, scientists from another team that works with the Planck satellite made its own measurements and came to an entirely difference conclusion. What BICEP2 detected weren’t gravity waves at all, but polarized light produced by specks of dust in the galaxy.

“Extraordinary claims require extraordinary evidence”

No problem, the BICEP2 was proven wrong. That’s how science works, fortunately – one scientist or group reports a result (revolutionary or not), then another group replicates the results to confirm or not the findings. Science prides itself on contradictions, because that’s how the veil of confusion is ultimately lift to reveal truth. The problem is that the BICEP2 team behaved unscientific by announcing their results before these were verified by anyone outside the group. I’m not out to criticize them personally, I’m just trying to signal that this very event is an example of what can go wrong (hint: everything) went scientists steer away from a basic pillar that’s been proven time and time again to work: peer review. It’s not like this is the first time something like this happens. Only a couple of years ago a team at CERN made a most audacious claim that neutrinos could travel faster than light. The claim was later refuted and the initial results were attributed to some bad wiring in the detection tech. Some scientists from the project resigned, lives may have been ruined. Once again, we return to the basics : extraordinary claims require extraordinary evidence.

Video showing one of BICEP2’s researchers at Andrei Linde’s doorstep to celebrate. Linde is one of the theorists whose work they claimed to have proved.

Both the Planck satellite and the South Polar BICEP2 telescope are designed to study what’s called the cosmic microwave background (CMB). First discovered in 1964 in a groundbreaking paper, CMB can be liken to fossil light waves that are rippling through space to this day after being emitted some 300,000 years following the Big Bang. Since their discovery 50 years ago, the CMB has been the go to source for studying cosmological phenomena. Like CMB, gravity waves are also relics from a time long past, only these are theorized to have been emitted only fractions of a second after the Big Bang. By probing gravity waves, physics would be able to tell a great deal about what was going on in those critical moments that spurred the cosmic inflation. Most notably, it would help scientists differentiate between the so many cosmic inflation theories proposed until today.

After carefully analyzing their own observations for the cosmic microwave background, the Planck team concluded that the supposed signal for gravity waves was, more likely, just emission from dust. To analyze cosmic background radiation, scientists need to first subtract the glow of our own galaxy in the same wavelengths as the CMB microwaves. Apparently, the BICEP2 experiment missed to include maps of the dust polarisation from the Milky Way in their calculations (they didn’t have them at their disposal, granted). In the end, the researchers underestimated the foreground emission from dust, and therefore over-estimated the significance of any claimed gravitational wave detection.

Some people said this event gives science a bad rep. We’re all flooded with misinterpreted, out of context news that herald all sorts of scientific developments that turn out to be otherwise in reality. This time, it wasn’t the press that blew it; it was the scientists.

 

Still hot inside the Moon? Earth gravity creating a hot layer

A new study has shown that there is still an extremely hot layer deep inside the moon, with heat generated by the gravity from the Earth. If this is indeed the case, then the inside of the Moon has not yet entirely solidified, providing an insight on to how the Earth-Moon system evolved.

Credit: Image courtesy of National Astronomical Observatory of Japan

There is still a lot of debate regarding the Moon’s nature – is it a true satellite, or is it in fact a planet of its own, trapped by the Earth’s gravity system? When discussing the nature of such a celestial planet, you must understand how it was born and how it evolved. But studying the early stages and evolution of the Moon is no easy feat, and that’s why researchers were thrilled to find this hot layer. But how do you “find” a hot layer in the depths of the Moon? The key here is gravity.

We can get a good indication of what’s happening inside a celestial body by studying slight modifications in its shape. The shape of a celestial body being changes by the gravitational force of another body is called tide; we see this on Earth, in the oceans. High and low tides occur mostly due to the Moon’s gravity (the Sun also plays a smaller role), because water is so deformable that its desplacement can be easily observed. But even the solid parts can be displaced, though to a much smaller extent. Observing the degree of deformation enables us to infer several things about the interior.

But there are more ways to study the internal structure. When the Apollo program landed people on the Moon, they also left seismological sensors on the surface – because the Moon also has earthquakes (perhaps moonquakes would be more accurate though). Through these sensors, they showed that the satellite has two main parts: the “core,” the inner portion made up of metal, and the “mantle,” the outer portion made up of rock. Based on this data, and previous shape deformation observations, Dr. Yuji Harada and his team managed to show that there is also an intermediate, hot layer, wrapping and warming the core. But this study, while it may very well revolutionize what we know about the moon, it actually poses more questions than it answers, researchers say:

“I believe that our research results have brought about new questions. For example, how can the bottom of the lunar mantle maintain its softer state for a long time? To answer this question, we would like to further investigate the internal structure and heat-generating mechanism inside the Moon in detail. In addition, another question has come up: how has the conversion from the tidal energy to the heat energy in the soft layer affected the motion of the Moon relative to the Earth, and also the cooling of the Moon? We would like to resolve those problems as well so that we can thoroughly understand how the Moon was born and has evolved.”

Another investigator, Prof. Junichi Haruyama of Institute of Space and Aeronautical Science, Japan Aerospace Exploration Agency also emphasizes the significance of this study:

“A smaller celestial body like the Moon cools faster than a larger one like the Earth does. In fact, we had thought that volcanic activities on the Moon had already come to a halt. Therefore, the Moon had been believed to be cool and hard, even in its deeper parts. However, this research tells us that the Moon has not yet cooled and hardened, but is still warm. It even implies that we have to reconsider the question as follows: How have the Earth and the Moon influenced each other since their births? That means this research not only shows us the actual state of the deep interior of the Moon, but also gives us a clue for learning about the history of the system including both the Earth and the Moon.”

Scientific Reference: Yuji Harada, Sander Goossens, Koji Matsumoto, Jianguo Yan, Jinsong Ping, Hirotomo Noda, Junichi Haruyama. Strong tidal heating in an ultralow-viscosity zone at the core–mantle boundary of the Moon. Nature Geoscience, 2014; 7 (8): 569 DOI: 10.1038/ngeo2211