Seeing through the fog

There's something a little unsettling about the idea that when you're looking outward in space, you're looking backward in time.

If it seems like we're seeing things as they actually are, right now, it's only because (1) the speed of light is so fast, and (2) most of the objects we look at and interact with are relatively close by.  Even the Sun, though, which in astronomical terms is right on top of us, is eight light-minutes away, meaning that the light leaving its surface takes eight minutes to cross the 150 million kilometers between it and us.  If the Sun were suddenly to go dark -- not, mind you, a very likely occurrence -- we would have no way of knowing it for eight minutes.

The farther out you go, the worse it gets.  The nearest star to the Solar System, Proxima Centauri, is about 4.2 light years away.  So the awe-inspiring panorama of stars in a clear night sky is a snapshot of the past.  Some of the stars you're looking at (especially the red supergiants like Antares and Betelgeuse) might actually already have gone supernova, and that information simply hasn't gotten here yet.  None of the stars we see are in exactly the same positions relative to us as they appear to be to us right now.  

Worst of all is when you look way out, as the James Webb Space Telescope is currently doing, because then, you have to account not only for distance, but for the fact that the universe is expanding.  And it hasn't expanded at a uniform rate.  Current models support the inflationary model, which says that between 10^-36 and 10^-32 seconds after the Big Bang the universe expanded by a factor of around 10^26.  This seems like a crazy conjecture, but it immediately solves two perplexing problems in observational astronomy.

The Carina Nebula, as photographed by the James Webb Space Telescope [Image is in the Public Domain courtesy of NASA/JPL]

The first one, the horizon problem, has to do with the homogeneity of space.  Look as far out into space as you can in one direction, then do the same thing in the opposite direction, and what you'll see is essentially the same -- the same distribution of matter and energy.  The difficulty is that those two points are causally disconnected; they're far enough apart that light hasn't had time to travel from one to the other, and therefore no mechanism of communication can exist between them.  By our current understanding of information transfer, once causally disconnected, always causally disconnected.  So if something set the initial conditions in point A, how did point B end up with identical conditions if they've never been in contact with each other?  It seems like a ridiculous coincidence.

The other one is the flatness problem, which has to do with the geometry of space-time.  This subject gets complicated fast, and I'm a layperson myself, but as far as I understand it, the gist is this.  The presence of matter warps the fabric of space locally (as per the General Theory of Relativity), but what is its overall geometry?  From studies of such phenomenal as the cosmic microwave background radiation, it seems like the basic geometry of the universe as a whole is perfectly flat.  Once again, there seems to be no particular reason to expect that could occur by accident.

Both these problems are taken care of simultaneously by the inflationary model.  The horizon problem disappears if you assume that in the first tiny fraction of a second after the Big Bang, the entire universe was small enough to be causally connected, but during inflation the space itself expanded so fast that it carried pieces of it away faster than light can travel.  (This is not forbidden by the Theories of Relativity; matter and energy can't exceed the speed of light, but space-time itself is under no such stricture.)  The flatness problem is solved because the inflationary stretching smoothed out any wrinkles and folds that were in space-time at the moment of the Big Bang, just as taking a bunched-up bedsheet and pulling on all four corners flattens it out.

All of this will be facing some serious tests over the next few years as we get better and better at looking out into the far reaches.  Just last week a team at the University of Cambridge published a paper in Nature Astronomy about a new technique to look out so far that what you're seeing is only 378,000 years after the Big Bang.  (I know that may seem like a long time, but it's only 0.003% of the current age of the universe.)  The problem is that prior to this, the universe was filled with a fog of glowing hydrogen atoms, so it was close to opaque.  The new technique involves filtering out the "white noise" from the hydrogen haze, much the way as you can still see the shadows and contours of the landscape on a foggy day.  It's not going to be easy; the signal emitted by the actual objects that were there in the early universe is estimated to be a hundred thousand times weaker than the interference from the glowing fog.

It's mind-blowing.  I've been learning about this stuff for years, but I'm still boggled by it.  If I think about it too hard I'm a little like the poor woman in a video with science vlogger Hank Green, who is trying to wrap her brain around the idea that anywhere you look, if you go out far enough, you're seeing the same point in space (i.e. all spots currently 13.8 billion light years from us were condensed into a single location at the moment of the Big Bang), and seems to be about to have a nervous breakdown from the implications.  (Hat tip to my friend, the amazing author Robert Chazz Chute, for throwing the video my way.)

So think about all this next time you're looking up into a clear night sky.  It's not a bad thing to be reminded periodically how small we are.  The universe is a grand, beautiful, amazing, weird place, and how fortunate we are to be living in at time where we are finally beginning to understand how it works.

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Condensation and inflation

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I still recall my astonishment when one of my physics professors in college said, "We understand the physics of the universe fairly well back to about one-trillionth of a second after the Big Bang.  Before that, though, things are a little dicey."

To me, that sounded like having a pretty good handle on things, but that first one-trillionth of a second was pretty spectacular.  There were some extraordinary things going on very early along in that tiny time span -- from about 10⁻³⁶ to sometime between 10⁻³³ and 10⁻³² seconds after the initial singularity.  For those of you who are not mathematical types, this is the time between:

0.000000000000000000000000000000000001 seconds, and

0.0000000000000000000000000000001 seconds following the Big Bang.

This era is called the "inflationary period," a term that was coined by Alan Guth (then at Cornell) and Andrei Linde of Stanford, way back in 1979, who were investigating the question of why there are no magnetic monopoles (magnetic particles with only a north or south pole, but not both) and stumbled upon a phenomenon called a false vacuum that accounted for the known properties of matter and the universe.  The problem was, the mathematics of the false vacuum required a period extremely early on in the universe's history when it underwent exponential expansion.  If you thought the time duration of inflation defied the imagination, the size expansion is worse -- in that minuscule fraction of a second, the universe increased in volume by a factor of 10⁷⁸ -- one followed by 78 zeroes.

(Regular readers of Skeptophilia may remember that a while back, I wrote about a rather hysterical article that was making the rounds, speculating about the likelihood of our false vacuum state being superseded by a true vacuum -- which would rapidly destroy the entire universe.  The general conclusion of the physicists is that the risk of this is close enough to zero that you shouldn't be losing any sleep over it.)

[Image licensed under the Creative Commons Original: Drbogdan Vector: Yinweichen, History of the Universe, CC BY-SA 3.0]

As crazy as this sounds, it's been borne up by the evidence.  The vast majority of the research done on this topic is far beyond me even considering my B.S. in physics, but suffice it to say that most physicists accept inflation as a reality.  It accounts for a number of interesting phenomena, including isotropy -- that the universe looks homogeneous no matter what direction you look, which begs an explanation unless you think that the Earth is located in the dead center of the universe, a possibility that is even less than our risk of being destroyed by a true vacuum.  So it may sound hard to believe, but apparently, this enormous expansion in an unimaginably tiny fraction of a second actually happened.

Just last week there was another piece of evidence added to all of this, wherein scientists at the University of Maryland created a peculiar form of matter called a Bose-Einstein condensate that exhibited the properties of cosmic inflation, albeit (and fortunately) on a much smaller scale.  Emily Conover, over at Science News, describes the experiment as follows:

Shaped into a tiny, rapidly expanding ring, the condensate grew from about 23 micrometers in diameter to about four times that size in just 15 milliseconds.  The behavior of that widening condensate re-created some of the physics of inflation, a brief period just after the Big Bang during which the universe rapidly ballooned in size (SN Online: 12/11/13) before settling into a more moderate expansion rate. 

In physics, seemingly unrelated systems can have similarities under the hood. Scientists have previously used Bose-Einstein condensates to simulate other mysteries of the cosmos, such as black holes (SN: 11/15/14, p. 14).  And the comparison between Bose-Einstein condensates and inflation is particularly apt: A hypothetical substance called the inflaton field is thought to drive the universe’s extreme expansion, and particles associated with that field, known as inflatons, all take on the same quantum state, just as atoms do in the condensate.

Another point in favor of this research having recreated on some level the early expansion of the universe is that sound waves sent through the condensate increased in wavelength -- just as light has been red-shifted by the expansion of the space it's traveling through.

I'd be lying if I said I understood last week's paper on anything but the most rudimentary level, but it still gives me a sense of wonder that we can peer into the distant past -- into a time that lasted almost no time at all -- and use that information to draw conclusions about why the universe has the properties it does.   The progress we've made in expanding scientific understanding, in just the last twenty years, is mind-boggling.

All of which makes me wonder what the next twenty years will bring.  I'm hoping it's a warp drive, but that might be a forlorn hope, given that the General Theory of Relativity is strictly enforced in most jurisdictions.

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