Our Universe is Dying

Brace yourselves: winter is coming. And by winter I mean the slow heat-death of the Universe, and by brace yourselves I mean don’t get terribly concerned because the process will take a very, very, very long time. (But still, it’s coming.)

vista-survey-telescope
Part of ESO’s VISTA telescope in Chile, one of seven telescopes used in the GAMA survey (ESO)

Based on findings from the Galaxy and Mass Assembly (GAMA) project, which used seven of the world’s most powerful telescopes to observe the sky in a wide array of electromagnetic wavelengths, the energy output of the nearby Universe (currently estimated to be ~13.82 billion years old) is currently half of what it was “only” 2 billion years ago — and it’s still decreasing.

“The Universe has basically plonked itself down on the sofa, pulled up a blanket and is about to nod off for an eternal doze,” said Professor Simon Driver from the International Centre for Radio Astronomy Research (ICRAR) in Western Australia, head of the nearly 100-member international research team.

As part of the GAMA survey 200,000 galaxies were observed in 21 different wavelengths, from ultraviolet to far-infrared, from both the ground and in space. It’s the largest multi-wavelength galaxy survey ever made.

Of course this is something scientists have known about for decades but what the survey shows is that the reduction in output is occurring across a wide range of wavelengths. The cooling is, on the whole, epidemic.

Watch a video below showing a fly-through 3D simulation of the GAMA survey:

“Just as we become less active in our old age, the same is happening with the Universe, and it’s well past its prime,” says Dr. Luke Davies, a member of the ICRAR research team, in the video.

But, unlike living carbon-based bags of mostly water like us, the Universe won’t ever actually die. And for a long time still galaxies will evolve, stars and planets will form, and life – wherever it may be found – will go on. But around it all the trend will be an inevitable dissipation of energy.

“It will just grow old forever, slowly converting less and less mass into energy as billions of years pass by,” Davies says, “until eventually it will become a cold, dark, and desolate place where all of the lights go out.”

Our own Solar System will be a quite different place by then, the Sun having cast off its outer layers – roasting Earth and the inner planets in the process – and spending its permanent retirement cooling off as a white dwarf. What will remain of Earthly organisms by then, including us? Will we have spread throughout the galaxy, bringing our planet’s evolutionary heritage with us to thrive elsewhere? Or will our cradle also be our grave? That’s entirely up to us. But one thing is certain: the Universe isn’t waiting around for us to decide what to do.

The findings were presented by Professor Driver on Aug. 10, 2015, at the IAU XXIX General Assembly in Honolulu, and have been submitted for publication in the Monthly Notices of the Royal Astronomical Society.

Read more/sources: ESO and ICRAR

Is There a Mirror Universe?

Could there be a mirror universe, where everything is backwards – and everybody has goatees? How badly do you need to bend the laws of physics to make this happen?

One of the great mysteries in cosmology is why the Universe is mostly matter and not antimatter. If you want to learn more about that specific subject, you can click here and watch an episode all about that.

During the Big Bang, nearly equal amounts of matter and antimatter were created, and subsequently annihilated. Nearly equal. And so we’re left with a Universe made of matter.

But could there be antimatter stars out there? With antimatter planets in orbit. Could there be a backwards Universe that operates just like our regular Universe, but everything’s made of antimatter? And if it’s out there, does it have to be evil? Do they only know how to conquer? Does everyone, even the antimatter babies and ladies, have handsome goatees? How about sashes? I hear they’re big on sashes. OOH and daggers. Gold daggers with little teensy antimatter emeralds and rubies.

Antimatter, without the goatee, was theorized in 1928 by Paul Dirac, who realized that one implication of quantum physics was that you could get electrons that had a positive charge instead of a negative charge. They were discovered by Carl D. Anderson just 4 years later, which he named “positron” for positive electron.

We believe he was clearly snubbing Dirac, by not naming them the “Diracitron”, alternately they were saving that name for a giant Japanese robot.

These antiparticles are created through high energy particle collisions happening naturally in the Universe, or unnaturally inside our “laugh in the face of God and nature” particle accelerators. We can even detect the annihilation out there in the Universe where matter and antimatter crash into each other.

Physicists have discovered a range of anti-particles. Anti-protons, anti-neutrons, anti-hydrogen, anti-helium. To date, there’s been no evidence of any goatees or sashes. Naturally, they wondered what might happen if the balance of the Universe was flipped. What if we had a Universe made out of mostly antimatter? Would it still… you know, work? Could you have antimatter stars, antimatter planets, and even those antimatter people we mentioned?

The Large Hadron Collider (CERN/LHC)
The Large Hadron Collider (CERN/LHC)

When physics swap out matter for anti-matter in their equations, they call it charge conjugation. It turns out, no. If you reversed the charge of all the particles in the Universe, it wouldn’t evolve in the same way as our “plain old non-sashed” Universe.

To fix this problem, physicists considered the implications if you had an actual mirror Universe, where all the particles behaved as if they were mirror images of themselves. This sounds a little more in line with our “Through a mirror, darkly” goatee and sash every day festival universe. This is all the bits backwards. Spin, charge, velocity, the works. They called this parity inversion. So, would this work?

Again, it turns out that the answer is no. It would almost work out, but there’s a tendency for the weak nuclear force, the one the governs nuclear decay to violate this idea of parity inversion. Even in a mirror Universe, the weak nuclear force is left-handed. Dammit, weak nuclear force, get your act together, if not just for the sake of the costumes and cooler bridge lighting.

What matter and antimatter might look like annihilating one another. Credit: NASA/CXC/M. Weiss
What matter and antimatter might look like annihilating one another. Credit: NASA/CXC/M. Weiss

What if you reversed both the charge and the parity at the same time? What if you had antimatter in a mirror Universe? Physicists called this charge-parity symmetry, or CP symmetry.

In a dazzling experiment and absolute “what if” one-upmanship exercise by James Cronin and Val Fitch in 1964. They demonstrated that no, you can’t have a mirror-antimatter Universe evolve with our physical laws. This experiment won the Nobel Prize in 1980.

Physicists had one last trick up their sleeves. It turns out that if you reverse time itself as well as making everything out of antimatter and holding it up to a mirror, you get true symmetry. All the physical lays are preserved, and you’d get a Universe that would look exactly like our own.

It turns out we could live in a mirror Universe, as long as you were willing to reverse the charge of every particle and run time backwards. And if you did, it would be indistinguishable from the Universe we actually live in. Now, if you’ll excuse me, I think I need to call my tailor, I hear sashes are going to be huge this year.

So what do you think, do we live in the real Universe or the mirror Universe? Tell us in the comments below.

Is the Universe Finite or Infinite?

Two possiblities exist: either the Universe is finite and has a size, or it’s infinite and goes on forever. Both possibilities have mind-bending implications.

In another episode of Guide to Space, we talked: “how big is our Universe”. Then I said it all depends on whether the Universe is finite or infinite. I mumbled, did some hand waving, glossed over the mind-bending implications of both possibilities and moved on to whatever snarky sci-cult reference was next because I’m a bad host. I acted like nothing happened and immediately got off the elevator.

So, in the spirit of he who smelled it, dealt it. I’m back to shed my cone of shame and talk big universe. And if the Universe is finite, well, it’s finite. You could measure its size with a really long ruler. You could also follow up statements like that with all kinds of crass shenanigans. Sure, it might wrap back on itself in a mindbending shape, like a of monster donut or nerdecahedron, but if our Universe is infinite, all bets are off. It just goes on forever and ever and ever in all directions. And my brain has already begun to melt in anticipation of discussing the implications of an infinite Universe.

Haven’t astronomers tried to figure this out? Of course they have, you fragile mortal meat man/woman! They’ve obsessed over it, and ordered up some of the most powerful sensitive space satellites ever built to answer this question.Astronomers have looked deep at the Cosmic Microwave Background Radiation, the afterglow of the Big Bang. So, how would you test this idea just by watching the sky?

Here’s how smart they are. They’ve searched for evidence that features on one side of the sky are connected to features on the other side of the sky, sort of like how the sides of a Risk map connect to each other, or there’s wraparound on the PacMan board. And so far, there’s no evidence they’re connected.

In our hu-man words, this means 13.8 billion light-years in all directions, the Universe doesn’t repeat. Light has been travelling towards us for 13.8 billion years this way, and 13.8 billion years that way, and 13.8 billion years that way; and that’s just when the light left those regions. The expansion of the Universe has carried them from 47.5 billion light years away. Based on this, our Universe is 93 billion light-years across. That’s an “at least” figure. It could be 100 billion light-years, or it could be a trillion light-years. We don’t know. Possibly, we can’t know. And it just might be infinite.

If the Universe is truly infinite, well then we get a very interesting outcome; something that I guarantee will break your brain for the entire day. After moments like this, I prefer to douse it in some XKCD, Oatmeal and maybe some candy crush.

Artist's conception of Planck, a space observatory operated by the European Space Agency, and the cosmic microwave background. Credit: ESA and the Planck Collaboration - D. Ducros
Artist’s conception of Planck, a space observatory operated by the European Space Agency, and the cosmic microwave background. Credit: ESA and the Planck Collaboration – D. Ducros

Consider this. In a cubic meter (or yard) of space. Alright, in a box of space about yay big (show with hands), there’s a finite number of particles that can possibly exist in that region, and those particles can have a finite number of configurations considering their spin, charge, position, velocity and so on.

Tony Padilla from Numberphile has estimated that number to be 10 to the power of 10 to the power of 70. That’s a number so big that you can’t actually write it out with all the pencils in the Universe. Assuming of course, that other lifeforms haven’t discovered infinite pencil technology, or there’s a pocket dimension containing only pencils. Actually, it’s probably still not enough pencils.

There are only 10 ^ 80 particles in the observable Universe, so that’s much less than the possible configurations of matter in a cubic meter. If the Universe is truly infinite, if you travel outwards from Earth, eventually you will reach a place where there’s a duplicate cubic meter of space. The further you go, the more duplicates you’ll find.

Ooh, big deal, you think. One hydrogen pile looks the same as the next to me. Except, you hydromattecist, you’ll pass through places where the configuration of particles will begin to appear familiar, and if you proceed long enough you’ll find larger and larger identical regions of space, and eventually you’ll find an identical you. And finding a copy of yourself is just the start of the bananas crazy things you can do in an infinite Universe.

The Hubble Ultra Deep Field seen in ultraviolet, visible, and infrared light. Image Credit: NASA, ESA, H. Teplitz and M. Rafelski (IPAC/Caltech), A. Koekemoer (STScI), R. Windhorst (Arizona State University), and Z. Levay (STScI)
The Hubble Ultra Deep Field seen in ultraviolet, visible, and infrared light. Image Credit: NASA, ESA, H. Teplitz and M. Rafelski (IPAC/Caltech), A. Koekemoer (STScI), R. Windhorst (Arizona State University), and Z. Levay (STScI)

In fact, hopefully you’ll absorb the powers of an immortal version of you, because if you keep going you’ll find an infinite number of yous. You’ll eventually find entire duplicate observable universes with more yous also collecting other yous. And at least one of them is going to have a beard.

So, what’s out there? Possibly an infinite number of duplicate observable universes. We don’t even need multiverses to find them. These are duplicate universes inside of our own infinite universe. That’s what you can get when you can travel in one direction and never, ever stop.

Whether the Universe is finite or infinite is an important question, and either outcome is mindblenderingly fun. So far, astronomers have no idea what the answer is, but they’re working towards it and maybe someday they’ll be able to tell us.

So what do you think? Do we live in a finite or infinite universe? Tell us in the comments below.

How Can Space Travel Faster Than The Speed Of Light?

Cosmologists are intellectual time travelers. Looking back over billions of years, these scientists are able to trace the evolution of our Universe in astonishing detail. 13.8 billion years ago, the Big Bang occurred. Fractions of a second later, the fledgling Universe expanded exponentially during an incredibly brief period of time called inflation. Over the ensuing eons, our cosmos has grown to such an enormous size that we can no longer see the other side of it.

But how can this be? If light’s velocity marks a cosmic speed limit, how can there possibly be regions of spacetime whose photons are forever out of our reach? And even if there are, how do we know that they exist at all?

The Expanding Universe

Like everything else in physics, our Universe strives to exist in the lowest possible energy state possible. But around 10-36 seconds after the Big Bang, inflationary cosmologists believe that the cosmos found itself resting instead at a “false vacuum energy” – a low-point that wasn’t really a low-point. Seeking the true nadir of vacuum energy, over a minute fraction of a moment, the Universe is thought to have ballooned by a factor of 1050.

Since that time, our Universe has continued to expand, but at a much slower pace. We see evidence of this expansion in the light from distant objects. As photons emitted by a star or galaxy propagate across the Universe, the stretching of space causes them to lose energy. Once the photons reach us, their wavelengths have been redshifted in accordance with the distance they have traveled.

Two sources of redshift: Doppler and cosmological expansion; modeled after Koupelis & Kuhn. Credit: Brews Ohare.
Two sources of redshift: Doppler and cosmological expansion; modeled after Koupelis & Kuhn. Bottom: Detectors catch the light that is emitted by a central star. This light is stretched, or redshifted, as space expands in between. Credit: Brews Ohare.

This is why cosmologists speak of redshift as a function of distance in both space and time. The light from these distant objects has been traveling for so long that, when we finally see it, we are seeing the objects as they were billions of years ago.

The Hubble Volume

Redshifted light allows us to see objects like galaxies as they existed in the distant past; but we cannot see all events that occurred in our Universe during its history. Because our cosmos is expanding, the light from some objects is simply too far away for us ever to see.

The physics of that boundary rely, in part, on a chunk of surrounding spacetime called the Hubble volume. Here on Earth, we define the Hubble volume by measuring something called the Hubble parameter (H0), a value that relates the apparent recession speed of distant objects to their redshift. It was first calculated in 1929, when Edwin Hubble discovered that faraway galaxies appeared to be moving away from us at a rate that was proportional to the redshift of their light.

Fit of redshift velocities to Hubble's law. Credit: Brews Ohare
Fit of redshift velocities to Hubble’s law. Credit: Brews Ohare

Dividing the speed of light by H0, we get the Hubble volume. This spherical bubble encloses a region where all objects move away from a central observer at speeds less than the speed of light. Correspondingly, all objects outside of the Hubble volume move away from the center faster than the speed of light.

Yes, “faster than the speed of light.” How is this possible?

The Magic of Relativity

The answer has to do with the difference between special relativity and general relativity. Special relativity requires what is called an “inertial reference frame” – more simply, a backdrop. According to this theory, the speed of light is the same when compared in all inertial reference frames. Whether an observer is sitting still on a park bench on planet Earth or zooming past Neptune in a futuristic high-velocity rocketship, the speed of light is always the same. A photon always travels away from the observer at 300,000,000 meters per second, and he or she will never catch up.

General relativity, however, describes the fabric of spacetime itself. In this theory, there is no inertial reference frame. Spacetime is not expanding with respect to anything outside of itself, so the the speed of light as a limit on its velocity doesn’t apply. Yes, galaxies outside of our Hubble sphere are receding from us faster than the speed of light. But the galaxies themselves aren’t breaking any cosmic speed limits. To an observer within one of those galaxies, nothing violates special relativity at all. It is the space in between us and those galaxies that is rapidly proliferating and stretching exponentially.

The Observable Universe

Now for the next bombshell: The Hubble volume is not the same thing as the observable Universe.

To understand this, consider that as the Universe gets older, distant light has more time to reach our detectors here on Earth. We can see objects that have accelerated beyond our current Hubble volume because the light we see today was emitted when they were within it.

Strictly speaking, our observable Universe coincides with something called the particle horizon. The particle horizon marks the distance to the farthest light that we can possibly see at this moment in time – photons that have had enough time to either remain within, or catch up to, our gently expanding Hubble sphere.

And just what is this distance? A little more than 46 billion light years in every direction – giving our observable Universe a diameter of approximately 93 billion light years, or more than 500 billion trillion miles.

The observable - or inferrable universe. This may just be a small component of the whole ball game.
The observable universe, more technically known as the particle horizon.

(A quick note: the particle horizon is not the same thing as the cosmological event horizon. The particle horizon encompasses all the events in the past that we can currently see. The cosmological event horizon, on the other hand, defines a distance within which a future observer will be able to see the then-ancient light our little corner of spacetime is emitting today.

In other words, the particle horizon deals with the distance to past objects whose ancient light that we can see today; the cosmological event horizon deals with the distance that our present-day light that will be able to travel as faraway regions of the Universe accelerate away from us.)

Dark Energy

Thanks to the expansion of the Universe, there are regions of the cosmos that we will never see, even if we could wait an infinite amount of time for their light to reach us. But what about those areas just beyond the reaches of our present-day Hubble volume? If that sphere is also expanding, will we ever be able to see those boundary objects?

This depends on which region is expanding faster – the Hubble volume or the parts of the Universe just outside of it. And the answer to that question depends on two things: 1) whether H0 is increasing or decreasing, and 2) whether the Universe is accelerating or decelerating. These two rates are intimately related, but they are not the same.

In fact, cosmologists believe that we are actually living at a time when His decreasing; but because of dark energy, the velocity of the Universe’s expansion is increasing.

That may sound counterintuitive, but as long as Hdecreases at a slower rate than that at which the Universe’s expansion velocity is increasing, the overall movement of galaxies away from us still occurs at an accelerated pace. And at this moment in time, cosmologists believe that the Universe’s expansion will outpace the more modest growth of the Hubble volume.

So even though our Hubble volume is expanding, the influence of dark energy appears to provide a hard limit to the ever-increasing observable Universe.

Our Earthly Limitations

cosmology tapestry

Cosmologists seem to have a good handle on deep questions like what our observable Universe will someday look like and how the expansion of the cosmos will change. But ultimately, scientists can only theorize the answers to questions about the future based on their present-day understanding of the Universe. Cosmological timescales are so unimaginably long that it is impossible to say much of anything concrete about how the Universe will behave in the future. Today’s models fit the current data remarkably well, but the truth is that none of us will live long enough to see whether the predictions truly match all of the outcomes.

Disappointing? Sure. But totally worth the effort to help our puny brains consider such mind-bloggling science – a reality that, as usual, is just plain stranger than fiction.

Where Did the Big Bang Happen?

Imagine the Big Bang, and you’re imagining an explosion. There must be come place we could travel in the Universe and see the wreckage left over from the Big Bang. So, where is it?

Close your eyes and imagine the Big Bang. That first moment, where all the energy, matter and light came into existence. It’s an explosion right? Fire, debris, sinks, marmots and anvils flying past the camera in an ever expanding cloud of hot gas.

And like any explosion, there must be an aftermath, right? Some place we could travel in the Universe and see the exact spot that everything began; the exact location where the Big Bang happened and ideally a huge crater in spacetime where the Universe began.

I expect you’re imagining our little scene in your mind. Complete with space-time indentations and orbital detritus. I hope you’re also getting the unsettling feeling of dread that I’m about to smash up beloved sci-fi tropes for my own amusement. And here it is…

There’s no exact spot that the Big Bang happened. In fact, the Big Bang happened everywhere in the Universe. The problem generally comes from the term “Big Bang”. It brings to mind explosions, detonations, balloons being popped, and everything being blown out to chickenbasket hades. It’s too bad for us regular folk, this isn’t a good descriptive term for what the Big Bang was.

So I’m going to propose a new term, and just use it from here on out, and pretend like it was always this way. So, from here on out, I’m going to call it the Big Stretch, and by that I mean I’ve always called it the Big Stretch, and for those of you familiar with this type of retconning, the chocolate ration is being increased from 40 grams to 25 grams.

Imagine a balloon covered in dots, then inflate the balloon. Also, for the purposes of this illustration, you’re a 2-dimensional creature living at one of those dots and watching all the other dots. From your perspective, everything will smell like that weird damp spit and rubber balloon scent.

You’ll also see all other other dots moving away from you. You might even think you’re at the center of the expansion of the balloon. And then if you jumped to any other dot, you’d see the same thing. Just smelly dots, all racing away from you.

Expansion of the Universe. Image credit: Eugenio Bianchi, Carlo Rovelli & Rocky Kolb.
Expansion of the Universe. Image credit: Eugenio Bianchi, Carlo Rovelli & Rocky Kolb.

Now a lesser being would get all caught up thinking about the fact that the balloon is a three-dimensional object, and the center of the expansion is actually at the middle of the balloon. But you’re a 2D creature. You can’t comprehend anything but the surface of the balloon. That and the funky smell.

Now take that concept and scale it up one more dimension. As a three-dimensional creature trapped within a three-dimensional Universe witnessing it stretching out three dimensions. Every galaxy is moving away from you. But if you travel to any other galaxy, it looks like all the other galaxies are moving away from them.

Could a four-dimensional being find the center of the expansion, the place where the Big Bang happened? Probably. 4D beings are cool like that. But then, a 5D being would probably laugh at their simplistic 4D view of the Universe, with their quaint Klein bottles and rustic hypercubes. Suck it 4D jerks, they’d say, and then they’d trap them in their 5D lockers for the entirety of recess until the janitor heard the banging and let them out.

And don’t get me started on those 11D jerks. Those guys are awful, and they really think they’re better than everyone else. They’re like Greg Marmand from Omega House but with 8 more dimensions of nose to look down at you across.

So, where did the Big Bang happen? It happened everywhere. All places formed in the Big Bang – I mean – Big Stretch, and they’ve been moving away from each other for 13.8 billion years. There’s no one place you can point to and say: the Big Bang happened there.But you can be totally obnoxious and point to anywhere, and say the Big Bang happened there. Since the Big Bang happened everywhere, it happened in your hometown. Tell us where you’re from in the comments below.

Is Everything Actually Shrinking?

Whoa, here’s something to think about. Maybe the Universe isn’t expanding at all. Maybe everything is actually just shrinking, so it looks like it’s expanding. Turns out, scientists have thought of this.

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Video Transcript

It’s tinfoil hat day again at The Guide To Space. There’s some people who would have you believe the Universe is expanding. They’re peddling this idea it all started with a bang, and that expansion is continuing and accelerating. Yet, they can’t tell us what force is causing this acceleration. Just “dark energy”, or some other JK Rowling-esque sounding thing. Otherwise known as the acceleration that shall not be named, and it shall be taught in the class which follows potions in 3rd period.

I propose to you, faithful viewer, an alternative to this expansionist conspiracy. What if distances are staying the same, and everything is in fact, shrinking? Are we destined to compress all the way down to the Microverse? Is it only a matter of time before our galaxy starts drinking its coffee from a thimble or perhaps sealed in a pendant hanging on Orion’s belt? So, could we tell if that’s actually what’s going on?

Representation of the timeline of the universe over 13.7 billion years, and the expansion in the universe that followed. Credit: NASA/WMAP Science Team.
Representation of the timeline of the universe over 13.7 billion years, and the expansion in the universe that followed. Credit: NASA/WMAP Science Team.

Better get some scotch tape for the hats, kids. This one gets pretty rocky right out of the gate.
The first horrible and critical assumption here is that shrinking objects and an expanding universe would look exactly the same, which without magic or handwaving just isn’t the case. But you don’t have to take my word for it, we have science to punch holes in our Shrink-truther conspiracy.

Let’s start with distances. If we assumed the Earth and everything on it was getting smaller, we’d also be shrinking things like meter sticks. In the past they would have been larger. If everything was larger in the past, including the length of a meter, this means the speed of light would have appeared slower in the past. So was the speed of light slower in the past? I’m afraid it wasn’t, which really hobbles the shrinky-dink universe plot. But how do we know that?

The diagram shows the electromagnetic spectrum, the absorption of light by the Earth's atmosphere and illustrates the astronomical assets that focus on specific wavelengths of light. ALMA at the Chilean site and with modern solid state electronics is able to overcome the limitations placed by the Earth's atmosphere. (Credit: Wikimedia, T.Reyes)
The diagram shows the electromagnetic spectrum, the absorption of light by the Earth’s atmosphere and illustrates the astronomical assets that focus on specific wavelengths of light. ALMA at the Chilean site and with modern solid state electronics is able to overcome the limitations placed by the Earth’s atmosphere. (Credit: Wikimedia, T.Reyes)

You’ve probably seen spectral lines before or at least heard them referenced. Scientists use them to determine the chemical composition of materials. A changing speed of light would affect the spectral lines of distant objects, and because some people are just super smart and were able to do the math on this, we know that when we look at distant gas clouds we find the speed of light has changed no more than one part in a billion over the past 7 billion years.

Shrinking objects would also become more dense over time. This means that the universal constant of gravity should appear smaller in the past. Some have actually studied this, to determine whether it has changed over time, and they’ve also seen no change.

Artists illustration of the expansion of the Universe (Credit: NASA, Goddard Space Flight Center)
Artists illustration of the expansion of the Universe (Credit: NASA, Goddard Space Flight Center)

If objects in the Universe were shrinking, the Universe would actually be collapsing. If galaxies weren’t moving away from each other, their gravity would cause them to start falling toward each other. If they were shrinking, assuming their mass doesn’t change, their gravity would be just as strong, so shrinking wouldn’t stop their mutual attraction. A Universe of shrinking objects would look exactly opposite to what we observe.

So, good news. We’re pretty sure that objects, and us, and all other things in the Universe are not shrinking. We’re still not sure why anyone would name a thing Shrinky Dinks. Especially a craft toy marketed at children.

Why Is Andromeda Coming Towards Us?

I don’t want to freak you out, but you should be aware that there’s a gigantic galaxy with twice our mass headed right for us. Naw, I’m just kidding. I totally want to freak you out. The Andromeda galaxy is going to slam head first into the Milky Way like it doesn’t even have its eyes on the road.

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Transcript

I don’t want to freak you out, but you should be aware that there’s a gigantic galaxy with twice our mass headed right for us. Naw, I’m just kidding. I totally want to freak you out. The Andromeda galaxy is going to slam head first into the Milky Way like it doesn’t even have its eyes on the road.

This collision will tear the structure of our galaxy apart. The two galaxies will coalesce into a new, larger elliptical galaxy, and nothing will ever be the same again, including your insurance premiums. There’s absolutely nothing we can do about it. It’s like those “don’t text and drive commercials” where they stop time and people get out and have a conversation about their babies and make it clear that selfish murderous teenagers are really ruining everything for all of us all the time.

The Andromeda Galaxy will collide with the Milky Way in the future. Credit: Adam Evans
The Andromeda Galaxy will collide with the Milky Way in the future. Credit: Adam Evans

And now that we know disaster is inbound, all we can do is ask WHY? Why this is even happening? Isn’t the Universe expanding, with galaxies speeding away from us in all directions? Shouldn’t Andromeda be getting further away, and not closer? What the hay, man!

Here’s the thing, the vast majority of galaxies are travelling away from us at tremendous speed. This was the big discovery by Edwin Hubble in 1929. The further away a galaxy is, the faster it’s moving away from us. The most recent calculation by NASA in 2013 put this amount at 70.4 kilometers per second per megaparsec. At a billion light-years away, the expansion of the Universe is carrying galaxies away from us at 22,000 km/s, or about 7% of the speed of light. At 100 million light-years away, that speed is only 2,200 km/s.

Which actually doesn’t seem like all that much. Is that like Millenium Falcon fast or starship Enterprise Warp 10 fast? Andromeda is only 2.5 million light-years away. Which means that the expansion of the Universe is carrying it away at only 60 kilometers per second. This is clearly not fast enough for our purposes of not getting our living room stirred into the backyard pool. As the strength of gravity between the Milky Way and Andromeda is strong enough to overcome this expansive force. It’s like there’s an invisible gravity rope connecting the two galaxies together. Dragging us to our doom. Curse you, gravity doom rope!

The Hubble Space Telescope's extreme close-up of M31, the Andromeda Galaxy. Picture released in January 2015. Credit: NASA, ESA, J. Dalcanton, B.F. Williams, and L.C. Johnson (University of Washington), the PHAT team, and R. Gendler
The Hubble Space Telescope’s extreme close-up of M31, the Andromeda Galaxy. Picture released in January 2015. Credit: NASA, ESA, J. Dalcanton, B.F. Williams, and L.C. Johnson (University of Washington), the PHAT team, and R. Gendler

Andromeda is speeding towards us at 110 kilometers per second. Without the expansion of the Universe, I’m sure it would be faster and even more horrifying! It’s the same reason why the Solar System doesn’t get torn apart. The expansion rate of the Universe is infinitesimally small at a local level. It’s only when you reach hundreds of millions of light-years does the expansion take over from gravity.

You can imagine some sweet spot, where a galaxy is falling towards us exactly as fast as it’s being carried away by the expansion of the Universe. It would remain at roughly the same distance and then we can just be friends, and they don’t have to get all up in our biz. If Andromeda starts complaining about being friend-zoned, we’ll give them what-for and begin to re-evaluate our friendship with them, because seriously, no one has time for that.

The discovery of dark energy in 1998 has made this even more complicated. Not only is the Universe expanding, but the speed of expansion is accelerating. Eventually distant galaxies will be moving faster away from us than the speed of light. Only the local galaxies, tied together by gravity will remain visible in the sky, eventually all merging together. Everything else will fall over the cosmic horizon and be lost to us forever.

This annotated artist's conception illustrates our current understanding of the structure of the Milky Way galaxy. Image Credit: NASA
This annotated artist’s conception illustrates our current understanding of the structure of the Milky Way galaxy. Image Credit: NASA

All things in the Universe are speeding away from us, it’s just that gravity is a much stronger force at local levels. This is why the Solar System holds together, and why Andromeda is moving towards us and in about 4 billion years or so, the Andromeda galaxy is going to slam into the Milky Way.

So, if by chance you only watched the first part of this video, freaked out, sold your possessions and joined some crazy silver jumpsuit doomsday cult, and are now, years later watching the conclusion… you may feel a bit foolish. However, I hope that you at least made some lifelong friendships and got to keep the jumpsuit.

Really, there’s nothing to worry about. Stars are spread so far apart that individual stars won’t actually collide with each other. Even if humanity is still around in another 4 billion years or so, which is when this will all go down. This definitely isn’t something we’ll be concerned with. It’s just like climate change. Best of luck future generations!

What do you think, will humans still be around in 4 billion years to enjoy watching the spectacle of the Milky Way and Andromeda collide?

Like a BOSS: How Astronomers are Getting Precise Measurements of the Universe’s Expansion Rate

Astrophysicists studying the expansion of the Universe with the largest galaxy catalogs ever assembled are ushering in an exciting era of precision cosmology. Last week, the Sloan Digital Sky Survey (SDSS) issued its final public data release, and scientists working in its largest program, the Baryon Oscillation Spectroscopic Survey (BOSS) also presented their final results at the American Astronomical Society meeting in Seattle, Washington.

By mapping over 10,000 square degrees — 25% of the sky — BOSS is “measuring our universe’s accelerated expansion with the world’s largest extragalactic redshift survey,” according to SDSS-III Director Daniel Eisenstein of the Harvard-Smithsonian Center for Astrophysics. The BOSS results include new and precise measurements of the universe’s expansion rate (called the “Hubble constant”) and matter density, which includes dark matter, stars, gas, and dust.

BOSS conducted its observations at 2.5-meter Sloan Foundation Telescope at Apache Point Observatory in New Mexico, producing spectra and spatial positions for 1.5 million galaxies and 300,000 quasars in a volume equivalent to a cube with length 8.5 billion light-years on a side (see image above). Astronomers used this rich dataset to map the objects’ distributions and to detect the characteristic scale imprinted by baryon acoustic oscillations in the early universe. Sound waves propagate outward with time, like ripples spreading in a pond, and are indicated by a large-scale clustering signal in the positions of galaxies relative to each other (see illustration below). By analyzing this signal at different times, it is possible to study the behavior of the mysterious “dark energy” causing the accelerating expansion of the universe.

An illustration of the concept of baryon acoustic oscillations, imprinted in the early universe and seen today in galaxy surveys. (courtesy:  Chris Blake and Sam Moorfield)
An illustration of the concept of baryon acoustic oscillations, imprinted in the early universe and seen today in galaxy surveys. (courtesy: Chris Blake and Sam Moorfield)

In BOSS’s final results, hundreds of scientists in the international collaboration measured this scale with unprecedented precision. In particular, Ashley Ross from Ohio State University presented results that demonstrated the power of combining an analysis of the transverse and line-of-sight distributions of galaxies. In a paper by Eric Aubourg and collaborators, BOSS astronomers measured the cosmic distance scale of galaxies in the “local” universe and of quasars in the distance universe with impressively small systematic errors—at less than the 1% level—when combined with cosmic microwave background constraints. Their cosmological analysis yields a measurement of the Hubble constant and of the matter density of the universe consistent with a “flat” cold dark matter cosmology with a cosmological constant (see below). Cosmological models including curvature, evolving dark energy, or massive neutrinos are not completely ruled out but are less supported by the data than before. Other results from the collaboration will be submitted for publication in the coming months.

Cosmological constraints on the Hubble parameter h, matter density Ωm, and curvature parameter Ωk from BOSS's baryon acoustic oscillations (BAO) combined with supernovae (SN) and Planck results. (Courtesy: Aubourg et al. 2014)
Cosmological constraints on the Hubble parameter h, matter density Ωm, and curvature parameter Ωk from BOSS’s baryon acoustic oscillations (BAO) combined with supernovae (SN) and Planck results. (Courtesy: Aubourg et al. 2014)

The BOSS dataset “represents the gold standard in mapping out the network of galaxies that comprises the large-scale structure of the Universe…The data enables us to trace, with greater precision than ever before, the presence of dark energy, the behaviour of gravity on cosmic scales, and the effect of massive neutrinos,” says Chris Blake of Swinburne University, not affiliated with the collaboration.

Where will the BOSS team go from here? The collaboration has begun work on SDSS-IV, whose six-year mission includes an ambitious extended BOSS (eBOSS) survey. According to eBOSS Targeting Coordinator Jeremy Tinker of New York University, eBOSS observations of over 700,000 quasars will precisely measure the distance scale “at a much higher redshift regime that is not covered by current large-scale surveys.”

You can read more about BOSS and updates about the three other componenets of the SDSS in our previous article here.
SDSS website

(Full disclosure: Ramin Skibba had been a member of the BOSS collaboration during 2010-2012.)

What Is This Empty Hole In Space?

What may appear at first glance to be an eerie, empty void in an otherwise star-filled scene is really a cloud of cold, dark dust and molecular gas, so dense and opaque that it obscures the distant stars that lie beyond it from our point of view.

Similar to the more well-known Barnard 68, “dark nebula” LDN 483 is seen above in an image taken by the MPG/ESO 2.2-meter telescope’s Wide Field Imager at the La Silla Observatory in Chile.

While it might seem like a cosmic no-man’s-land, no stars were harmed in the making of this image – on the contrary, dark nebulae like LDN 483 are veritable maternity wards for stars. As their cold gas and dust contracts and collapses new stars form inside them, remaining cool until they build up enough density and gravity to ignite fusion within their cores. Then, shining brightly, the young stars will gradually blast away the remaining material with their outpouring wind and radiation to reveal themselves to the galaxy.

The process may take several million years, but that’s just a brief flash in the age of the Universe. Until then, gestating stars within LDN 483 and many other clouds like it remain dim and hidden but keep growing strong.

Wide-field view of the LDN 483 region. (Credit: ESO and Digitized Sky Survey 2)
Wide-field view of the LDN 483 region. (Credit: ESO and Digitized Sky Survey 2)

Located fairly nearby, LDN 483 is about 700 light-years away from Earth in the constellation Serpens.

Source: ESO

Hearing the Early Universe’s Scream: Sloan Survey Announces New Findings

Imagine a single mission that would allow you to explore the Milky Way and beyond, investigating cosmic chemistry, hunting planets, mapping galactic structure, probing dark energy and analyzing the expansion of the wider Universe. Enter the Sloan Digital Sky Survey, a massive scientific collaboration that enables one thousand astronomers from 51 institutions around the world to do just that.

At Tuesday’s AAS briefing in Seattle, researchers announced the public release of data collected by the project’s latest incarnation, SDSS-III. This data release, termed “DR12,” represents the survey’s largest and most detailed collection of measurements yet: 2,000 nights’ worth of brand-new information about nearly 500 million stars and galaxies.

One component of SDSS is exploring dark energy by “listening” for acoustic oscillation signals from the the acceleration of the early Universe, and the team also shared a new animated “fly-through” of the Universe that was created using SDSS data.

The SDSS-III collaboration is based at the powerful 2.5-meter Sloan Foundation Telescope at the Apache Point Observatory in New Mexico. The project itself consists of four component surveys: BOSS, APOGEE, MARVELS, and SEGUE. Each of these surveys applies different trappings to the parent telescope in order to accomplish its own, unique goal.

BOSS (the Baryon Oscillation Spectroscopic Survey) visualizes the way that sound waves produced by interacting matter in the early Universe are reflected in the large-scale structure of our cosmos. These ancient imprints, which date back to the first 500,000 years after the Big Bang, are especially evident in high-redshift objects like luminous-red galaxies and quasars. Three-dimensional models created from BOSS observations will allow astronomers to track the expansion of the Universe over a span of 9 billion years, a feat that, later this year, will pave the way for rigorous assessment of current theories regarding dark energy.

At the press briefing, Daniel Eistenstein from the Harvard-Smithsonian Center for Astrophysics explained how BOSS requires huge volumes of data and that so far 1.4 million galaxies have been mapped. He indicated the data analyzed so far strongly confirm dark energy’s existence.

This tweet from the SDSS twitter account uses a bit of humor to explain how BOSS works:

APOGEE (the Apache Point Observatory Galactic Evolution Experiment) employs a sophisticated, near-infrared spectrograph to pierce through thick dust and gather light from 100,000 distant red giants. By analyzing the spectral lines that appear in this light, scientists can identify the signatures of 15 different chemical elements that make up the faraway stars – observations that will help researchers piece together the stellar history of our galaxy.

MARVELS (the Multi-Object APO Radial Velocity Exoplanet Large-Area Survey) identifies minuscule wobbles in the orbits of stars, movements that betray the gravitational influence of orbiting planets. The technology itself is unprecedented. “MARVELS is the first large-scale survey to measure these tiny motions for dozens of stars simultaneously,” explained the project’s principal investigator Jian Ge, “which means we can probe and characterize the full population of giant planets in ways that weren’t possible before.”

At the press briefing, Ge said that MARVELS observed 5,500 stars repeatedly, looking for giant exoplanets around these stars. So far, the data has revealed 51 giant planet candidates as well as 38 brown dwarf candidates. Ge added that more will be found with better data processing.

A still photo from an animated flythrough of the universe using SDSS data. This image shows a small part of the large-scale structure of the universe as seen by the SDSS -- just a few of many millions of galaxies. The galaxies are shown in their proper positions from SDSS data. Image credit: Dana Berry / SkyWorks Digital, Inc.
A still photo from an animated flythrough of the universe using SDSS data. This image shows a small part of the large-scale structure of the universe as seen by the SDSS — just a few of many millions of galaxies. The galaxies are shown in their proper positions from SDSS data. Image credit: Dana Berry / SkyWorks Digital, Inc.

SEGUE (the Sloan Extension for Galactic Understanding and Exploration) rounds out the quartet by analyzing visible light from 250,000 stars in the outer reaches of our galaxy. Coincidentally, this survey’s observations “segue” nicely into work being done by other projects within SDSS-III. Constance Rockosi, leader of the SDSS-III domain of SEGUE, recaps the importance of her project’s observations of our outer galaxy: “In combination with the much more detailed view of the inner galaxy from APOGEE, we’re getting a truly holistic picture of the Milky Way.”

One of the most exceptional attributes of SDSS-III is its universality; that is, every byte of juicy information contained in DR12 will be made freely available to professionals, amateurs, and lay public alike. This philosophy enables interested parties from all walks of life to contribute to the advancement of astronomy in whatever capacity they are able.

As momentous as the release of DR12 is for today’s astronomers, however, there is still much more work to be done. “Crossing the DR12 finish line is a huge accomplishment by hundreds of people,” said Daniel Eisenstein, director of the SDSS-III collaboration, “But it’s a big universe out there, so there is plenty more to observe.”

DR12 includes observations made by SDSS-III between July 2008 and June 2014. The project’s successor, SDSS-IV, began its run in July 2014 and will continue observing for six more years.

Here is the video animation of the fly-through of the Universe: