Tag Archives: expansion

Environmental concerns stop expansion of British airport

In what has been hailed as a pivotal victory for environmental protection, city councilors in Bristol, UK, have voted against plans to expand the city’s airport, citing environmental concerns.

Expansion work is already underway at the Bristol airport — but even further expansion was rejected.

Environment vs Expansion

Bristol is a fairly large city, with a population of around half a million people. It’s serviced by an airport seven miles away, with a capacity of 7 million people / year. For many, that’s not enough.

The airport was given permission to expand from 7 to 10 million passengers, something which is expected to be completed by 2021. But there were plans to further increase the airport to 12 million passengers — and here, things took an unexpected turn.

Thousands of people publicly objected to the expansion, with environmental activists organizing several symbolic protests against this move. The opposition to expansion plans also included Bristol’s vibrant artistic scene, which includes the likes of Massive Attack and Banksy.

The arguments supporting this expansion are straightforward: some people would like to travel from Bristol to destinations that aren’t currently served. They need to drive to other airports. Building an expansion would reduce this problem and provide jobs and profits to the municipality.

The arguments against the expansion are also clear. The expansion would cause more people to fly, contributing to the climate emergency, and causing localized pollution (leading to an increase in people suffering from conditions such as asthma). Furthermore, the expansion would harm local wildlife — in particular, colonies of bats and birds located in the area. The negative environmental impact, many argued, outweighs the economic one.

Will Bristol set an important precedent? Image credits: Robert Cutts.

It’s already an old tale: on one hand, you have those who want economic growth and increased comfort, and on the other hand, the people fighting for the environment.

Except, this time, the environment won.

After a four-hour meeting, Bristol city council voted against the airport expansion, 18-7. Don Davies, the leader of the council, said:

“What the committee has considered is that the detrimental effect of the expansion of the airport on this area and the wider impact on the environment outweighs the narrower benefits to airport expansion.”

Councillor John Ley-Morgan emphasized that climate change played a major role in this decision:

“How can we achieve our ambition for carbon neutrality by 2030 if we approve this decision?”

Spokespeople for the airport expressed their disappointment with the result of the vote, but for scientists and most of the city’s population, this was a victory for civil society.

Adrian Gibbs, an environmental consultant, told The Guardian that we would need to plant 4 million trees every single year to offset the expansion. Sarah Warren, cabinet member for the climate emergency in the municipality, also added that the expansion is incompatible with the global environmental crisis. For environmental activists, the vote was vindication after months of protests.

This is not the end of the process. The decision can be appealed or the expansion can be modified, after which it might be approved. But it could represent an important turning point.

Air travel is one of the areas for which we don’t really have a sustainable plan — and it’s growing at an impressive rate. Many cities all around the world are considering airport expansions, and the environmental impact of these expansions is significant.

Bristol Airport will still have a capacity of 10 million passengers — which is remarkable for a city of 0.5 million people. However, airport officials say they have responded to the climate emergency and revealed a plan to make the airport “carbon neutral” by 2025. They’ve already taken some steps, such as increasing the use of electric vehicles, shifting to renewable energy and increasing the cost of its drop-off parking as this is the “least sustainable way” to get to the airport.

But when it comes to the planes themselves (and the local environmental impact of the airport), there is still little leverage to offset the damage.

It remains to be seen whether Bristol has set a landmark precedent or this will just be an exception — for now, at least, there is a moment to rejoice for environmentalists.

The universe’s rate of expansion is in dispute – and we may need new physics to solve it


File 20180730 106514 bm50kc.jpg?ixlib=rb 1.1
Colorful view of the universe as seen by Hubble in 2014.
NASA, ESA, H. Teplitz and M. Rafelski (IPAC/Caltech), A. Koekemoer (STScI), R. Windhorst (Arizona State University), and Z. Levay (STScI)


Next time you eat a blueberry (or chocolate chip) muffin consider what happened to the blueberries in the batter as it was baked. The blueberries started off all squished together, but as the muffin expanded they started to move away from each other. If you could sit on one blueberry you would see all the others moving away from you, but the same would be true for any blueberry you chose. In this sense galaxies are a lot like blueberries.

Since the Big Bang, the universe has been expanding. The strange fact is that there is no single place from which the universe is expanding, but rather all galaxies are (on average) moving away from all the others. From our perspective in the Milky Way galaxy, it seems as though most galaxies are moving away from us – as if we are the centre of our muffin-like universe. But it would look exactly the same from any other galaxy – everything is moving away from everything else.

To make matters even more confusing, new observations suggest that the rate of this expansion in the universe may be different depending on how far away you look back in time. This new data, published in the Astrophysical Journal, indicates that it may time to revise our understanding of the cosmos.

Hubble’s challenge

Cosmologists characterise the universe’s expansion in a simple law known as Hubble’s Law (named after Edwin Hubble – although in fact many other people preempted Hubble’s discovery). Hubble’s Law is the observation that more distant galaxies are moving away at a faster rate. This means that galaxies that are close by are moving away relatively slowly by comparison.

The relationship between the speed and the distance of a galaxy is set by “Hubble’s Constant”, which is about 44 miles (70km) per second per Mega Parsec (a unit of length in astronomy). What this means is that a galaxy gains about 50,000 miles per hour for every million light years it is away from us. In the time it takes you to read this sentence a galaxy at one million light years’ distance moves away by about an extra 100 miles.

The Hubble Space Telescope as seen from the departing Space Shuttle Atlantis, flying STS-125, HST Servicing Mission 4.

This expansion of the universe, with nearby galaxies moving away more slowly than distant galaxies, is what one expects for a uniformly expanding cosmos with dark energy (an invisible force that causes the universe’s expansion to accelerate ) and dark matter (an unknown and invisible form of matter that is five times more common than normal matter). This is what one would also observe of blueberries in an expanding muffin.

The history of the measurement of Hubble’s Constant has been fraught with difficulty and unexpected revelations. In 1929, Hubble himself thought the value must be about 342,000 miles per hour per million light years – about ten times larger than what we measure now. Precision measurements of Hubble’s Constant over the years is actually what led to the inadvertent discovery of dark energy. The quest to find out more about this mysterious type of energy, which makes up 70% of the energy of the universe, has inspired the launch of the world’s (currently) best space telescope, named after Hubble.

Cosmic showstopper

Now it seems that this difficulty may be continuing as a result of two highly precise measurements that don’t agree with each other. Just as cosmological measurements have became so precise that the value of the Hubble constant was expected to be known once and for all, it has been found instead that things don’t make sense. Instead of one we now have two showstopping results.

On the one side we have the new very precise measurements of the Cosmic Microwave Background – the afterglow of the Big Bang – from the Planck mission, that has measured the Hubble Constant to be about 46,200 miles per hour per million light years (or using cosmologists’ units 67.4 km/s/Mpc).

On the other side we have new measurements of pulsating stars in local galaxies, also extremely precise, that has measured the Hubble Constant to be 50,400 miles per hour per million light years (or using cosmologists units 73.4 km/s/Mpc). These are closer to us in time.

Both these measurements claim their result is correct and very precise. The measurements’ uncertainties are only about 300 miles per hour per million light years, so it really seems like there is a significant difference in movement. Cosmologists refer to this disagreement as “tension” between the two measurements – they are both statistically pulling results in different directions, and something has to snap.

New physics?

So what’s going to snap? At the moment the jury is out. It could be that our cosmological model is wrong. What is being seen is that the universe is expanding faster nearby than we would expect based on more distant measurements. The Cosmic Microwave Background measurements don’t measure the local expansion directly, but rather infer this via a model – our cosmological model. This has been tremendously successful at predicting and describing many observational data in the universe.

So while this model could be wrong, nobody has come up with a simple convincing model that can explain this and, at the same time, explain everything else we observe. For example we could try and explain this with a new theory of gravity, but then other observations don’t fit. Or we could try and explain it with a new theory of dark matter or dark energy, but then further observations don’t fit – and so on. So if the tension is due to new physics, it must be complex and unknown.

A less exciting explanation could be that there are “unknown unknowns” in the data caused by systematic effects, and that a more careful analysis may one day reveal a subtle effect that has been overlooked. Or it could just be statistical fluke, that will go away when more data is gathered.

It is presently unclear what combination of new physics, systematic effects or new data will resolve this tension, but something has to give. The expanding muffin picture of the universe may not work anymore, and cosmologists are in a race to win a “great cosmic bake-off” to explain this result. If new physics is required to explain these new measurements, then the result will be a showstopping change of our picture of the cosmos.

Thomas Kitching, Reader in Astrophysics, UCL

This article was originally published on The Conversation. Read the original article.

The Universe is expanding faster than we thought, new Hubble study finds

Astronomers working with the Hubble telescope have discovered that the Universe is expanding 5-9% faster than expected, and this is intriguing.

This illustration shows the three steps astronomers used to measure the universe’s expansion rate to an unprecedented accuracy, reducing the total uncertainty to 2.4 percent. Astronomers made the measurements by streamlining and strengthening the construction of the cosmic distance ladder, which is used to measure accurate distances to galaxies near and far from Earth. Credit: NASA, ESA, A. Feild (STScI), and A. Riess (STScI/JHU)

Even though it’s a well documented phenomenon, universal expansion is still baffling. The entire universe, every single thing that we know of is moving apart – and it’s accelerating! That’s just crazy when you think about it. The fact that we can measure how fast it’s expanding is even crazier.

In theory, you could measure the expansion of the universe could by taking a standard ruler and measuring the distance between two cosmologically distant points, waiting a certain time, and then measuring the distance again, but in practice, you’re never going to have a cosmological ruler, and time isn’t really on your side either. So astronomers are using other indirect methods, which of course come with an associated error. Such an error was corrected this time, and it came as quite a surprise.

“This surprising finding may be an important clue to understanding those mysterious parts of the universe that make up 95 percent of everything and don’t emit light, such as dark energy, dark matter, and dark radiation,” said study leader and Nobel Laureate Adam Riess of the Space Telescope Science Institute and The Johns Hopkins University, both in Baltimore, Maryland.

He an his team refined the measurement and managed to reduce the uncertainty to only 2.4 percent. They measured about 2,400 Cepheid stars (stars that pulsate radially) in 19 galaxies and compared the observed brightness of the stars. Cepheid stars pulsate at rates that correspond to their true brightness, which can be compared with their apparent brightness as seen from Earth to accurately determine their distance.

The new constant value they found 73.2 kilometers per second per megaparsec. (A megaparsec equals 3.26 million light-years.) This means that the distance between cosmic objects will double in another 9.8 billion years. We still don’t know what is the cause for the initial error, but one of the likely culprits is dark energy, already known to be accelerating the universe. Another possible explanation is an unexpected characteristic of dark matter. Dark matter is the backbone of the universe upon which galaxies built themselves up into the large-scale structures seen today.

“If we know the initial amounts of stuff in the universe, such as dark energy and dark matter, and we have the physics correct, then you can go from a measurement at the time shortly after the big bang and use that understanding to predict how fast the universe should be expanding today,” said Riess. “However, if this discrepancy holds up, it appears we may not have the right understanding, and it changes how big the Hubble constant should be today.”


The Universe expands much faster than we thought, and current models can’t explain why

Scientists have completed the most precise measurement of the Universe’s rate of expansion to date,  but the result just isn’t compatible with speed calculations from residual Big Bang radiation. Should the former results be confirmed by independent techniques, we might very well have to rewrite the laws of cosmology.

Data from galaxies such as M101, seen here, allow scientists to gauge the speed at which the universe is expanding.
Image credits X-ray: NASA/CXC/SAO; Optical: Detlef Hartmann; Infrared: NASA/JPL-Caltech

“I think that there is something in the standard cosmological model that we don’t understand,” says astrophysicist Adam Riess, a physicist at Johns Hopkins University in Baltimore, Maryland, who co-discovered dark energy in 1998 and led the latest study.

This discrepancy might even mean that dark energy — thought to be responsible for observed acceleration in the expansion of the Universe — has steadily been gaining in strength since the dawn of time. Should the results be confirmed, they have the potential of “becoming transformational in cosmology” said Kevork Abazajian, cosmologist at the University of California, Irvine.

In our current cosmological model, the Universe is the product of a tug of war of sorts between dark matter and dark energy. Dark matter uses its gravitational pull to slow down expansion, while dark energy is pushing everything apart, making it accelerate. Riess and others suggest that dark energy’s strength has been constant throughout the history of the Universe.

Most of what we know about dark matter-dark energy interaction and how each of them affects the Universe comes from studying remanent Big Bang radiation, known as the cosmic microwave background. The most exhaustive study on this subject was done by the European Space Agency’s Planck observatory. Those measurements essentially give researchers a picture of the Universe when it was really young — 400.000 years of age. Based on them, they can determine how the Universe evolved up to now, including the rate of expansion at any point in its history. Knowing where it was and where it is now, they can also predict those two parameters in the future.

But here’s the thing: they don’t add up to the observed rate of expansion. These predictions are invalidated by direct measurements of the current rate of cosmic expansion — also known as the Hubble constant. This constant is calculated by observing how rapidly nearby galaxies move away from the Milky Way using stars of known intrinsic brightness called ‘standard candles’. Until now the errors were small enough that the disagreement could be ignored, but Riess and his team warn that the discrepancy is too great to ignore any longer.

Riess’s team studied two types of standard candles in 18 galaxies using hundreds of hours of observing time on the Hubble Space Telescope.

“We’ve been going gangbusters with this,” says Riess.

They managed to measure constant with an uncertainty of 2.4%, down from a previous best result of 3.3%. Based on this value, they found that the actual rate of expansion is about 8% faster than what the Planck data predicts, Riess reports.

If both the new Hubble constant and the earlier Planck team measurements are accurate, then there’s a problem with our current model. Either we misunderstood dark energy, or we got it right but it just got stronger as time progressed. Planck researcher François Bouchet of the Institute of Astrophysics in Paris says he doubts that the problem is in his team’s measurement, but that the new findings are “exciting” regardless of what the solution turns out to be.

However, when working on such (forgive the pun) astronomical scales, a lot of things can go wrong. One last possibility is that standard candles aren’t that reliable when it comes to precision measurements, says Wendy Freedman, astronomer at the University of Chicago in Illinois. In 2001 she led the first precision measurement of the Hubble constant. She and her team are working on an alternative method based on a different class of stars. We’ll just have to wait and see.

The full paper, titled “A 2.4% Determination of the Local Value of the Hubble Constant” has been published on the arXiv online repository on and can be read here.

Einstein’s theory passes tough test

Two studies put Einstein’s theory, the General Theory of Relativity to a test unlike any other before. The two teams used extensive observations from NASA’s Chandra X-ray Observatory to analyze galaxy clusters, the biggest objects in the Universe that are bound together by gravity (at least, that we know of). The first team produced results that dramaticaly “weaken” a competitor theory, while ther shows that Einstein’s theory works over a vast range of times and distances. Two thumbs up.

“If General Relativity were the heavyweight boxing champion, this other theory [“f(R) gravity”] was hoping to be the upstart contender,” said Fabian Schmidt of the California Institute of Technology in Pasadena, who led the study. “Our work shows that the chances of its upsetting the champ are very slim”


Well if General Relativity were a heavyweight boxing champion, it would definitely be Cassius Clay. The point of the rival theory was to explaion why the Universe expands faster and faster. In the f(R) gravity theory, the cosmic expansion acceleration comes not from a form of energy, but rather from a modification of the gravitational force. The modification of the force also affects the rate at which small cosmic objects can grow over huge periods of time, thus opening the possibility of testing the theory with galaxy clusters observations.

What they found was that gravity is not different for distances of even 130 million light years.

“This is the strongest ever constraint set on an alternative to General Relativity on such large distance scales,” said Schmidt. “Our results show that we can probe gravity stringently on cosmological scales by using observations of galaxy clusters.”

The second study also tested the theory across cosmological periods and distances. The results fit General Relativity exactly.

“Einstein’s theory succeeds again, this time in calculating how many massive clusters have formed under gravity’s pull over the last five billion years,” said David Rapetti of the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC) at Stanford University and SLAC National Accelerator Laboratory, who led the new study. “Excitingly and reassuringly, our results are the most robust consistency test of General Relativity yet carried out on cosmological scales.”

However, this doesn’t solve the problem of the Universe expanding at an accelerated speed. It did eliminate an inaccurate theory, though. The matter, still, remains a mystery.

“Cosmic acceleration represents a great challenge to our modern understanding of physics,” said Rapetti’s co-author Adam Mantz of NASA’s Goddard Space Flight Center in Maryland. “Measurements of acceleration have highlighted how little we know about gravity at cosmic scales, but we’re now starting to push back our ignorance.”