The universe is much bigger than big [View all]

[cthulu2016]

Last edited Fri Sep 28, 2012, 04:18 AM - Edit history (15)

Everyone reading this grew up knowing the universe was far too big for a human to really grasp. Hell, just the distance to the sun is already too much. (How can light take eight minutes to get somewhere?)

But some of us grew up with much smaller or larger unimaginably large universes. It was already too big to grasp in 1920, and our estimation of its size keeps growing. By 1980-1990 our estimation of the universe was so much larger than it had been that it has become, in my mind, a philosophical difference in kind, not merely degree.

Your grandfather's infinitely vast universe turned out to be just our neighborhood in a much larger universe. We went to the moon while thinking the universe was a fraction of itself.

The modern inflationary model of the universe is so big that not only could the universe not have sensibly been made for mankind, 90% of the universe is utterly unknowable to human beings. It is impossible for any information about most of the universe to ever reach a human mind, except by deduction.

How did the universe as we know it get so big? Well...

Einstein made us think some very weird and unfamiliar things about the universe (curved space, time running at different speeds, etc.) but at the same time provided a comforting sense of completeness. Einstein's universe was really pretty classical, with the universal speed limit of the speed of light providing an almost theological absolute. Nothing can travel faster than 186,000 miles a second.

And when we realized that the universe is all expanding from a central point then we know it started somewhere, as a point. That's comforting too... a real beginning. The big bang begs the question what preceded the big bang, but religion begs the question "who made God?" Either way there is a comfort to an, "In the beginning..."

And that starting point was not infinitely long ago. About 14 billion years. So we have a speed limit and finite time-line, and thus we had an absolute limit on the size of the universe.

If the big bang was 14 billion years ago and two photons came flying out of the big bang in opposite directions they can be no further apart than 28 billion light years today. That is a very long distance, and a scale beyond our real comprehension, but it is sensible. We can follow the reasoning.

Granted, we had to accept that there are things outside the "observable universe," things too far away for us to know about because they are more than 14 billion light years away. Since we are not at the very center a 14 billion light year radius from Earth is going to miss part of the universe.

But since we are not on the very edge then a 14 billion LY radius surely covered most of the universe. Our "observable universe" was most of what existed, and the invisible (to us) parts were known to be nestled over on the other side of a sphere of space no larger than 28 billion light year across and, for matter, considerably less. Two photons could be 28 billion light years apart by now but no two stars could be... stars cannot travel at the speed of light.

A big universe, yes, but with a beginning and a strictly limited size. Cozy enough.

And people readjusted and reintegrated ancient thinking into this vast but limited scientific universe and reached some psychological comfort zone.

But then science played a mean trick on us.

Nothing can move through space faster than the speed of light but we figured out from studying the thing that the space between things can expand faster than the speed of light... and it did.

D'oh!

The big bang didn't just spew stuff out into a thing called space. It created space. Space is a thing with properties, not mere nothingness.

And early in the whole process space inflated at a prodigious clip... considerably faster than the speed of light. Our two opposite-direction photons have each only carved their way through 14 billion light years of space, from their perspective, but all space, everywhere, was inflating like crazy around them and behind them so those two photons might be 50 billion light years apart... 100 billion... we don't know for sure.

And even though stars cannot move at the speed of light, or even close to it, there are (we believe today) stars much more than 28 billion light years apart! The stars (or mostly, the matter that later became stars) ended up with a lot of space in between, but they never crossed all that space.

A usual analogy is raisins in a rising cake. The cake in between the raisins is swelling up so the raisins get further apart from each other even though they are not moving through cake. (I don't pretend to really understand this, mind you. But it is our best hypothesis of how to account for observable facts.)

So though our universe is "only" about 14 billion years old, it has a radius much larger than 14 billion light years. And the part of the universe beyond our observable universe is... well, we don't know anymore. All that we can ever possibly see is just a sliver of an invisible (to us) universe of uncertain hugeness. And the whole mess seems to be accelerating... getting bigger and bigger faster and faster.

We can only see and measure with things that are limited to the speed of light so the bulk of the universe is lost to us. And the same goes for anyone someplace else in the universe. The thing is literally too big for anyone to see. (Fortunately, it isn't like the blind men and the elephant. We think the physical laws are the same throughout the universe so everyone just sees oodles of stars and galaxies. So more like the blind men and the garden hose... probably similar whichever part you're holding.)

The modern demotion of our observable universe to local news is a bit much to take because the size of our little observable corner of our universe is already a fricking joke! Beyond imagination.

We used to think our galaxy was the universe, and that the andromeda galaxy was a nebula within the Milky Way. Then we thought maybe there was us and a few other galaxies. Here's what we know today just from what we can see of our tiny visible part of the whole (mostly invisible) universe...


http://www.democraticunderground.com/10021420208

And that mess of galaxies in our observable universe isn't even all that is within our little visible bubble. There's more we can't see because there's stuff in the way, or it came into being later so the light couldn't have made it here.

Note the little square next to the moon. All those galaxies in the picture are seen in that little square. And right next to that little square is another tiny bit of sky with just as many galaxies. And so on. And we have every reason to think the whole invisible (to us) universe is just as jam-packed with galaxies as our little neighborhood.

Our galaxy, the Milky Way, has 300 billion stars in it. We now think there are hundreds of billions of galaxies, most invisible to us, each with hundreds of billions of stars. I think that is 60 Trillion Billions of stars.

What is that... like 9,000,000,000,000 stars for every person on Earth?

Even if we are the only intelligent life forms in our entire galaxy (unlikely) we are still like the old saying about New York. "If you're one in a million we've got fourteen people just like you." Except it's billions.

If physical laws throughout the universe are constant (we think so) then everything that has ever happened here has had a chance to happen an almost infinite number of other places.

Is there life out there? Yes. Is there intelligent life? Yes. Are there cats? Yes. Are there tabby cats. Yes. Are there tabby cats with blue collars and one white paw named Mister Wuggles? Sure... probably. Why not?

Since an alien tabby cat cannot travel faster than light we will probably never meet alien Mister Wuggles. The same incredible bigness that suggests that almost anything that can exist in our universe's natural laws probably does exist also means that it is possible, or perhaps even probable that those billions of other living worlds are all too far away for us to ever know anything of. (Because we do have to follow the Einstein speed limit, even if the fabric of space doesn't always do so.)

One of the few upsides of all this is that we probably don't have to worry that we humans can ever destroy the universe. If it was possible somebody out there would have already done it.