Tag Archives: Day

Saturn Illustration.

Perturbations in Saturn’s rings reveal how long a day is on the gas giant

Saturn’s days are 10 hours, 33 minutes, and 38 seconds long — and we know this by looking at wave patterns in its rings.

Saturn Illustration.

Illustration showing NASA’s Cassini spacecraft in orbit around Saturn.
Image credits NASA / JPL-Caltech.

New observations from NASA’s Cassini spacecraft allowed researchers at the University of California Santa Cruz to calculate Saturn’s rate of rotation. This measurement — the most precise determination of its rotation rate — was based on observations of wave patterns created within the planet’s rings.

Timekeeping rings

“Particles in the rings feel this oscillation in the gravitational field. At places where this oscillation resonates with ring orbits, energy builds up and gets carried away as a wave,” explained Christopher Mankovich, a graduate student in astronomy and astrophysics at UC Santa Cruz, and lead author of the study.

Just like our own planet, Saturn vibrates in response to perturbations (large-scale movement of matter). Unlike our planet, these perturbations come not from the movement of tectonic plates, but likely from heat-driven convection in the planet’s gassy bulk. Such internal oscillations move about massive quantities of gas, which has a noticeable impact on local densities within Saturn’s atmosphere. Such changes, in turn, cause noticeable changes in the planet’s localized gravitational pull. And, even better, the frequency of oscillation within Saturn carries over to the gravitational effects — in short, they share the same ‘fingerprint’, so these internal events can be linked to their external, gravitational effects.

Saturn rings.

Image of Saturn’s rings taken by NASA’s Cassini spacecraft on Sept. 13, 2017.
Image credits NASA / JPL-Caltech / Space Science Institute.

Naturally, we’d need satellites or other sorts of equipment in orbit across the planet to pick up on such gravitational fluctuations. Which we haven’t really brought over yet. Rather conveniently, however, Saturn has a sprawling ring system surrounding it. They do react to the planet’s gravitational pull, its fluctuations causing certain wave patterns to form inside the rings. Not all patterns seen inside the rings are caused by gravitational effects — but most are.

In effect, this makes the rings act similarly to seismographs, devices that we use to measure earthquakes.

“Some of the features in the rings are due to the oscillations of the planet itself, and we can use those to understand the planet’s internal oscillations and internal structure,” says Jonathan Fortney, professor of astronomy and astrophysics at UC Santa Cruz and paper coauthor.

NASA’s Cassini spacecraft allowed researchers to observe Saturn’s rings in unprecedented detail. Mankovich’s team developed a series of models of the planet’s internal structure and used them to predict the frequency spectrum of Saturn’s internal vibrations. Then they compared their predictions to waves observed by Cassini in Saturn’s C ring.

One of the main results of this study is an estimation of Saturn’s speed of rotation — which has been notoriously difficult to accurately pin down. Saturn is basically a huge clump of gas and, as such, its surface doesn’t have any fixed, distinctive features we could track as it rotates. The planet is also unusual in that its magnetic poles are nearly perfectly aligned to its axis of rotation — so we can’t track those either. On Earth, for example, the magnetic poles aren’t aligned with this axis.

Mankovich’s team determined that a day on Saturn lasts for 10 hours, 33 minutes, and 38 seconds — several minutes shorter than previous estimates (which were based on radiometry readings from the Voyager and Cassini spacecraft).

“We now have the length of Saturn’s day, when we thought we wouldn’t be able to find it,” said Cassini Project Scientist Linda Spilker.

“They used the rings to peer into Saturn’s interior, and out popped this long-sought, fundamental quality of the planet. And it’s a really solid result. The rings held the answer.”

The paper “Measurement and implications of Saturn’s gravity field and ring mass” has been published in the journal Science.

Sleeping bear.

Wildlife is shifting activity to nighttime because they don’t want to run into humans

Humans are bugging wild animals — so the critters are staying hidden during the day.

Sleeping bear.

Image via Pixabay.

Animals are finding that the best way to deal with those pesky humans isn’t to go live someplace else, but to start living during the night. The findings, published by researchers from the University of California–Berkeley and Boise State University, show that previously-diurnal animals are shifting activity during night hours to avoid humans.

Under the cover of darkness

The team analyzed 76 studies involving 62 species of mammals on six continents, from opossums to elephants. These studies looked at how individual species changed their behavioral patterns in response to human activity such as hunting, farming, or development. Each study used some sort of technique to follow animals, from GPS trackers to motion-activated cameras.

The team then compared how much time those creatures spent actively at night under different types of human disturbance. One common feature all the surveyed animals shared was that they became far more active at night after humans arrived, the team reports. On average, they found that human presence triggered an increase of about 20 percent in nighttime activity, even in animals that aren’t normally night owls. Strikingly, the animals even delegated critical tasks such as hunting and foraging for nighttime activity. The team further reports that mammals which used to split activity roughly even between the day and night also shift more strongly towards darker hours — on average, these species increased nighttime activity to 68%.

It also became apparent that human activity doesn’t need to directly impact these species to determine a change in behavior. The team notes that all species responded similarly to human encroachment in their habitats. A deer, for example, will shift activity towards nighttime regardless if the humans it sees are hunters or hikers.

“It suggests that animals might be playing it safe around people,” Kaitlyn Gaynor, an ecologist at the University of California, Berkeley, who led the study, told PBS. “We may think that we leave no trace when we’re just hiking in the woods, but our mere presence can have lasting consequences.”

This shift in activity does help humans and animals coexist with less friction, the team notes. The findings might also help us design better conservation strategies that take into account species’ patterns of activity.

However, there’s also cause for concern. A nocturnal lifestyle can impact an animal’s ability to get food or mate, impacting the short- and long-term stability of whole species. This, ironically, also defeats the purpose of shifting activity in the first place. If animals are becoming more active at night to avoid us, but that only makes life harder for them, have they really escaped the impact of human activity?

The paper “The influence of human disturbance on wildlife nocturnality” has been published in the journal Science.

Nightshift.

Just two days of night-shift alter the activity of more than 100 blood proteins

Sleeping during the day and staying up all night will impact the concentration and activity of over 100 proteins in the blood — even if you only do it for short while.

Nightshift.

Image credits picsessionarts / Flickr.

Staying awake and eating during the night throws a wrench in the activity of blood-borne proteins, according to new research from the University of Colorado Boulder. The proteins identified by the team impact processes involved in a wide array of metabolic functions, from blood sugar levels to immune function. The study is the first to examine how protein levels in human blood, also known as the plasma proteome, vary over a 24-hour period and how altered sleep and meal timing affects them.

Protein shift

“This tells us that when we experience things like jet lag or a couple of nights of shift work, we very rapidly alter our normal physiology in a way that if sustained can be detrimental to our health,” said senior author Kenneth Wright, director of the Sleep and Chronobiology Laboratory and Professor in the Department of Integrative Physiology.

The team enlisted the help of six healthy male subjects in their 20s for the study. The participants were asked to spend six days at the university’s clinical translational research center. While here, their meals, sleeping hours, active periods and the hours they were exposed to light were tightly controlled and recorded.

On the first two days, the men were kept on a normal schedule: active hours and light exposure during the day, sleeping hours at night. They were then gradually transitioned to a night-shift work pattern —  they could get an eight-hour sleep if they wanted, but only during the day, and stayed up and ate at night. The team collected blood samples every four hours, which they analyzed for the concentrations and time-of-day-patterns of 1,129 proteins.

They report that 129 of these proteins’ patterns were thrown off by the simulated night shift. The effect was already noticeable by the second day of night-shift waking patterns, Depner adds.

One of the affected proteins was glucagon — which tells the liver to inject sugar into the bloodstream. Glucagon levels in the blood peaked during waking hours, the team found, meaning they shifted to night-hours as the participants started staying awake at night. But it also peaked in higher concentrations, the team adds. They think that this effect could, in the long-term, form the root cause of the higher diabetes rates seen in night-shift workers.

Night-shift wakefulness patterns also decreased blood levels of fibroblast growth factor 19. Previous research with animal models has shown this protein to boost calorie-burning and energy expenditure, the team adds. The participants in this study burned 10% fewer calories per minute when their schedule was misaligned.

Overall, thirty proteins showed a clear 24-hour-cycle, most showing a peak between 2 p.m. and 9 p.m.

“The takeaway: When it comes to diagnostic blood tests—which are relied upon more often in the age of precision medicine—timing matters,” said senior author Kenneth Wright.

The authors note that all the participants were kept in dim light conditions, to eliminate the effect of light-exposure (which can also strongly affect the circadian system) on the results. Even without the glow of electronics at night, changes in protein patterns were rapid and widespread.

“This shows that the problem is not just light at night,” Wright said. “When people eat at the wrong time or are awake at the wrong time that can have consequences too.”

The findings could lead to new treatment options for night shift workers, who are at a higher risk for diabetes and cancer. It could also enable doctors to precisely time administration of drugs, vaccines and diagnostic tests around the circadian clock.

The paper “Mistimed food intake and sleep alters 24-hour time-of-day patterns of the human plasma proteome” has been published in the journal PNAS.

Out of order sign.

The 2017 Earth Overshoot day is here almost a week earlier than last year

Unplug the speakers and push the cork back in the champagne bottle, it’s Earth Overshoot day!

Out of order sign.

Image credits Gordon Joly / Flickr.

This year’s least expected festivity falls on the 2nd of August, the WWF and Global Footprint Network report. Is that earlier than last year? Yes. Is that a bad thing? Also yes!

That’s because the Overshoot marks the day humanity used up all the resources our Earth can (re)generate in a year; everything we eat, drink, burn, or otherwise consume past this day puts us in a kind of environmental overdraft. And I use ‘resources’ here in the broadest sense possible, ranging from food and water all the way to how much carbon plants can sequester in a year.

“By August 2 2017, we will have used more from Nature than our planet can renew in the whole year,” the groups said in a statement.

“This means that in seven months, we emitted more carbon than the oceans and forests can absorb in a year, we caught more fish, felled more trees, harvested more, and consumed more water than the Earth was able to produce in the same period.”

The date comes down to the balance between what we use and throw out as trash — humanity’s global footprint — and what the Earth can produce and absorb — known as biocapacity. At present consumption patterns, humanity would need the equivalent of 1.7 Earths to supply all the natural resources we’ll use this year and deal with all the mess we’ll make without going into overdraft. But we only have one, meaning our activity from now on will place extra strain on environments, and eat into their ability to provide the things we need in the future.

Spending spree

Credit: Earth Overshoot Day.

Credit: Earth Overshoot Day.

Which isn’t good news. But then again, who hasn’t gone a few days with an overdraft card, right? It’s not ideal, but you get it fixed sooner or later and life moves on. Sure, as an isolated incident, but have you ever tried being in overdraft for 45 years? Because we as a species did just that.

And we’re getting into overdraft territory earlier each year. The Global Footprint Network has calculated the date of the Overshoot since 1986 based on data from thousand of economic sectors (fisheries, forestry, or energy production for example) from the UN. In the 1980s it fell in November. By 1993 it advanced to October, and by the 2000s it was well into September. Last year, it happened on the 8th of August, a full 6 days later than this year. One cause for hope is that the rate at which the Overshoot advances through the calendar seems to be slowing down, at least.

Nevertheless, the fact remains that we’re just two-thirds through this year and we’re already living on borrowed time. People in some countries consume way more than others on average — you can see when the date would fall for each country here — but finger-pointing won’t solve the issue here. We’re dealing with systemic issues that will require us to work together to solve, not split into blame-throwing camps. Most of us have a personal overshoot day. If you don’t believe me, you can calculate your own here.

The single biggest factor in our footprint, for example, is carbon emissions, gobbling up 60% of our allotted resources. We’re seeing a big drive behind clean energy recently, but there’s still a long way to go before we put a meaningful dent in that number. Food makes up 26% of our footprint, The Global Footprint Network reports. If we cut food waste in half, and swap protein-intensive foods for more fruit and vegetables, it could be reduced to 16%.

The easiest place to start, however, is with one’s own garden, so to speak. If you want to do your little part in helping humanity repair its credit rating to Bank Earth, you should consider eating less meat, driving less and always taking on passengers, and cutting down on trash by recycling and limiting food waste.

Sunrise

The Earth is spinning slower, making the days longer and longer

Days are getting longer as the Earth’s rotation suffers tiny alterations over time. But you’re probably not going to notice anything anytime soon — a day gets one extra minute every 6.7 million years, a new study estimates.

Sunrise

Image via Pexels.

Each “day” is the amount of time it takes for the planet to do a full rotation around its own axis. So any shift in the speed of Earth’s rotation will have an inverse and proportional effect on the length of a day — higher speeds shorten the day, slower rotation means longer days.

And the latter case seems to be true. A British team estimates that the average day has gained 1.8 milliseconds each century over the past 2700 years. The speed they calculated is “significantly less” than previous estimates which settled on a rate of 2.3 ms per century — which would translate to one minute every 5.2 million years. Still, retired Royal Greenwich Observatory astronomer and lead co-author Leslie Morrison admits that it remains “a very slow process.”

“These estimates are approximate, because the geophysical forces operating on the Earth’s rotation will not necessarily be constant over such a long period of time,” he added.

“Intervening Ice Ages etcetera will disrupt these simple extrapolations.”

The previous figure of 2.3 ms was estimated from calculations of the Moon’s effect on “Earth-braking” — its gravitational force pulls on the Earth’s water and land, effectively pulling against the force of rotation.

But Morrison and his team also factored in gravitational theories about the Earth’s movements around the Sun as well as the Moon-Earth interactions, to calculate the timing of solar eclipses over time as seen from our planet. They then calculated where on Earth they’d be visible from, and compared the results to records of eclipses from ancient Babylonians, Chinese, Greeks, Arabs and medieval Europeans.

“We obtained historical, relevant records from historians and translators of ancient texts,” explained Morrison for the AFP.

“For example, the Babylonian tablets, which are written in cuneiform script, are stored at the British Museum and have been decoded by experts there and elsewhere.”

They found discrepancies between the points eclipses should have been observable from and where they were actually seen. This discrepancy can only be caused by a rotational speed different from the one that the team used in their model (the present one.)

“This discrepancy is a measure of how the Earth’s rotation has been varying since 720 BC” when ancient civilisations started keeping eclipse records, they wrote.

Earth’s rotation speed can be influenced by the Moon’s breaking effect, electro-magnetic interaction inside the planet (between the solid core and the mantle that floats over it), as well as mass shifts on the planet — changes in sea level, shrinking polar caps since the last Ice Age, large reservoirs, and so on.

And while most of us probably won’t ever notice this increase, it’s vital that scientists know about it. This information can be used in adjusting high-precision clocks for example, which underpin our navigational systems.

The full paper “Measurement of the Earth’s rotation: 720 BC to AD 2015” has been published in the journal Proceedings of the Royal Society A.