Physicists just found a link between dark energy and the arrow of time

I am in the middle of writing  long piece about this. The following article is courtesy of Science Alert

For years, physicists have attempted to explain dark energy – a mysterious influence that pushes space apart faster than gravity can pull the things in it together. But physics isn’t always about figuring out what things are. A lot of it is figuring out what things cause.

And in a recent paper, a group of physicists asked this very question about dark energy, and found that in some cases, it might cause time to go forward.

When you throw a ball into the air, it starts with some initial speed-up, but then it slows as Earth’s gravity pulls it down. If you throw it fast enough (about 11 km per second, for those who want to try), it’ll never slow down enough to turn around and start falling back towards you, but it’ll still move more slowly as it moves away from you, because of Earth’s gravity.

Physicists and astronomers in the 1990s expected something similar to have occured after the big bang – an event that threw matter out in all directions. The collective gravity from all that matter should have slowed it all down, just like the Earth slows down the ball. But that’s not what they found.

Instead, everything seems to have sped up. There’s something pervading the Universe that physically spreads space apart faster than gravity can pull things together. The effect is small – it’s only noticeable when you look at far-away galaxies – but it’s there. It’s become known as dark energy – “dark”, because no one knows what it is.

Science is nothing if not the process of humans looking for things they can’t explain, so this isn’t the first time the Universe has stumped us. For centuries, one of those stumpers has been time itself: Why does time have an arrow pointing from the past to the present to the future?

It might seem like a silly question – I mean, if time didn’t go forward, then effects would precede causes, and that seems like it should be impossible – but it’s less of one than you might think.

The Universe, as far as we can tell, only operates according to laws of physics. And just about all of the laws of physics that we know are completely time-reversible, meaning that the things they cause look exactly the same whether time runs forward or backward.



 Featured image courtesy of  Paul Fleet/


Blue “Little Lion” Galaxy Could Reveal the Conditions at the Start of the Big Bang

Original article via The Science Explorer

Blue “Little Lion” Galaxy Could Reveal the Conditions at the Start of the Big Bang | The Science Explorer


It is the most metal-poor galaxy ever discovered.

About 30 million light-years from Earth lies a unique, faint blue galaxy located in the constellation Leo Minor. Why is it to special? It could shed new light on the conditions at the birth of the universe.

The galaxy Leoncino, or “little lion,” contains the lowest level of heavy chemical elements, or “metals,” ever observed in a system of stars. In astronomy, any element other than hydrogen or helium is referred to as a metal, and metal-poor galaxies closely resemble the early universe.

“Finding the most metal-poor galaxy ever is exciting since it could help contribute to a quantitative test of the Big Bang,” said co-author John J. Salzer, professor at IU Bloomington College of Arts and Sciences’ Department of Astronomy, in an IU news release. “There are relatively few ways to explore conditions at the birth of the universe, but low-metal galaxies are among the most promising.”


Photo credit: NASA; A. Hirschauer & J. Salzer, Indiana University; J. Cannon, Macalester College; and K. McQuinn, University of Texas. Image has been cropped

Going Beyond the Standard Model

“The Totally Unthinkable” –In 2016 CERN’s LHC Could Unveil Unknown Dimensions of the Universe – The Daily Galaxy –Great Discoveries Channel

Going beyond the Standard Model would “mean that there is yet another unbelievable idea out there. Something that is totally unthinkable,” said CERN senior physicist Paris Sphicas.  In 2016, the Large Hadron Collider (LHC)  could unveil whole new dimensions, help explain dark matter and dark energy, of which we have no understanding but which together make up 95 percent of the universe.

Late last year, before CERN shut down its LHC for a technical break, two separate teams of scientists said they had discovered anomalies that could possibly hint at the existence of a mysterious new particle that could prove the existence of extra space-time dimensions, or explain the enigma of dark matter, scientists say.

The high-energy frontier has traditionally had one primary goal, to probe directly any uncharted physics waters. This has translated into the gigantic effort to complete the unobserved elements of the Standard Model of particle physics as well as to search for for signs of physics beyond.These measurements form a solid base from which searches for physics beyond the standard model have been launched. Since the discovery of the Higgs Boson in 2012, searches for supersymmetry and several signatures of possible new exotic physics phenomena have been developed, and new parameter space is being explored.


READ MORE HERE  (via Daily Galaxy)

Why the Universe Ended Up With Three Dimensions

New paper explains why the Universe ended up with three dimensions

It’s probably not news to you that as residents of this fine Universe we call home, we can only move left or right, up or down, backwards or forwards. That’s it. There aren’t any other possible directions that aren’t some combination of those three.

These are our Universe’s three spatial dimensions, and why we have exactly three of them (not just one or two, five or 80) is still something of a mystery.

Not that physicists haven’t been searching for an answer – explaining the fundamental nature of reality is just a really hard nut to crack. But a new paper has shown that a universe with our laws of thermodynamics (which describe how energy moves around) will always get stuck with exactly three spatial dimensions. So basically, this paper just explained the Universe.

The researchers, from the University of Salamanca in Spain and the National Polytechnic Institute of Mexico, explained it with the first and second laws of thermodynamics.

READ MORE (via Science Alert)  Image: andrey_l/ 

NASA Unveil Giant Golden Mirrors of the James Webb Space Telescope

When launched, Hubble’s successor, NASA’s James Webb Space Telescope, will be the most powerful space telescope in the world (or, outside of it?). Though it’s still under construction and is expected to launch in 2018, officials have just now unveiled pictures of the telescope’s huge, golden mirrors. And boy, are they pretty.

These large, blinged-out mirrors are too large to fit onto a rocket, which means they have to fold up and unfurl in space where they will help researchers focus light from extremely faraway sources, hopefully capturing stars that formed shortly after the Universe was born.  READ MORE ON SCIENCE ALERT

Image courtesy of NASA.

The Amazing Hubble Image That Almost Wasn’t – Comet SL9 Just… — Scientiflix

The Amazing Hubble Image That Almost Wasn’t – Comet SL9 Just days before 21 fragments of periodic comet Shoemaker-Levy 9 slammed into the atmosphere of Jupiter, the Hubble Space Telescope developed two sets of problems. This is the nail-biting story of the engineering team’s trouble-shooting and problem-solving leading up to the July 16th 1994 series […]

via The Amazing Hubble Image That Almost Wasn’t – Comet SL9 Just… — Scientiflix

Physicists just debunked one of the most promising candidates for dark matter

Original article from the excellence Science Alert website.

From dark energy yesterday to dark matter today!

You probably know that just 15 percent of the known Universe is made up of matter that we can actually see. The majority of the Universe – some 85 percent of it – is made up of dark matter and dark energy – two phenomena that are currently 100 percent unknown to science, despite the best efforts of researchers worldwide.

But now, thanks to a paper authored by over 100 physicists… well, it’s still unknown, but it’s just a little less unknown than it was before, because one of the top candidates for dark matter has pretty much been debunked.

The kind of matter that makes up everything we’ve ever seen in the Universe, from tiny quarks to massive galaxies, is only 15 percent of the matter that’s actually out there. The rest is known enigmatically as dark matter, because we can’t see it and no one knows what it is, but we’re almost positive that it’s out there, unless we have to seriously rethink our understanding of the laws of gravity – the force that governs everything in the known Universe.

There are some scientists out there doing this kind of rethinking, but most agree that dark matter has to be something. They just disagree about what that something actually is. The leading contender is a class of Weakly Interacting Massive Particles, or WIMPs. But there are other possibilities with exciting names like axions, axion-like particles, and supersymmetric particles.

Now, thanks to the Fermi Large Area Telescope, the array of possibilities is starting to thin out.

Axions were first proposed in 1977 to resolve a problem in quantum chromodynamics – the theory of how quarks interact with one another. Later, when they were developing string theory over the next 10 or 20 years, they noticed some particles showing up in it that looked a lot like axions.

Physicists are famously good at naming things, so they called these exciting new particles axion-like particles, or ALPs.

It wasn’t long before they realised that axions and ALPs might also make good candidates for dark matter. When the Big Bang created all of the light and matter in the Universe, it should have also created a whole bunch of axions and ALPs – if they exist. But if they do, these particles probably would’ve congregated right where see evidence of dark matter.

Dark matter is hard to see – that’s what makes it dark matter – so to look for it, you need to think of something clever that no one has tried before. And scientists hadn’t really tried looking at gamma rays, so these researchers looked at gamma rays.

Every once in a while, you’d expect an axion or ALP to run into a bit of regular matter, which should send a gamma ray out into space with a specific energy. These gamma rays would then be visible to modern telescopes like the Fermi Large Area Telescope (LAT).

Different models of ALPs predict different numbers of them in the Universe: some models say that all of the dark matter could be ALPs, others say that they make up only a tiny fraction of it. These different models predict different amounts of gamma rays, so you can use the number and kind of gamma rays observed to test the different models of ALPs.

That’s a bunch of steps, but it’s exactly what a team of 102 scientists has done in a recent paper in Physical Review Letters.

They used six years of LAT data on the galaxy NGC 1275 (another very creative name), and checked to see if the observed gamma rays matched some popular models where ALPs make up about 5 percent of the dark matter in the Universe. If these ALP models were right, that would still leave 80 percent of the mass in the Universe unexplained. But you have to start somewhere with these things.

It looks like we’ll have to start somewhere else. The team simulated galaxies with and without the ALPs and then they checked the results of these simulations against those six years of observations. They found that the ALPs don’t seem to predict the observed gamma rays any better than the model without them.

And in science, if you have two hypotheses that perform equally well, you get rid of the one with more stuff in it. In this case, you get rid of the one with those ALPs.

There’s still a big range of possibilities to explore for LAT and for future gamma-ray telescopes. The most obvious one that the researchers mention is a model where ALPs make up all dark matter, not just 5 percent of it. But testing this model is going to take some time.

So it’s possible that in the next few years, we’ll discover what makes up all of the dark matter in the Universe. Or we’ll discover what doesn’t make it up. Either way, that’s pretty exciting.

Feature image: Artwork shows a black hole surrounded by axions (TU Wien)