Redshift 10 Territory
April 6, 2005 7:38 AM   Subscribe


That's auroras, dfowler, you jerk you.
posted by dfowler at 7:44 AM on April 6, 2005

Hey, I like astronomy a lot - but this FPP makes no sense. Auras? Summa? BFD? :? b?

posted by wfrgms at 7:48 AM on April 6, 2005

I don't know much about astronomy, but I find it interesting. I wonder though, how they can tell these stars are some of the first. Doesn't that depend on assumptions such as limits or a "center" of the universe? I'm sure there is an explanation of it, but I am genuinely curious.

If light travels at X speed, couldn't there much older stars that are just so far away the light hasn't reached here yet?
posted by dios at 8:13 AM on April 6, 2005

no posty when drinky
posted by quonsar at 8:20 AM on April 6, 2005

Ah, that typo sucked me right in. "Auras? Earth has an aura? Or even two?"
posted by dabitch at 8:30 AM on April 6, 2005


I think it has to do with the amount of blue-shift. The faster the object is moving away from us, the farther away it is. That's as close as anyone can come to an idea of location on the grand scale in the universe, as I understand.

Everywhere in the universe is equidistant from the origin of the universe. Not really possible to visualize.

And yes, I, too am confused by this FPP.
posted by argybarg at 8:42 AM on April 6, 2005

dios: It's been years since I studied cosmology, but my understanding of it goes something like this:

The expansion of the universe is not a question of everything moving away from some center point in space where the Big Bang occured. Rather, it is space itself is expanding in all directions at once. The term "Big Bang" is in fact kind of a misnomer in this regard because it leads people to believe that there was originally some kind of empty space in which a primeval "egg" came into being and exploded, scattering all matter in the universe from some central point.

In actual fact there was no space or time either. It is space-time itself that is expanding, making everything in the universe that is not bound strongly enough by the four fundamental forces (Strong, Weak, Electromagnetism, and Gravity) move apart. It's a really difficult thing to wrap one's mind around in natural language -- it's better understood in terms of mathematical formula. Professor Edward Wright at UCLA has a pretty good tutorial on the subject.

As to the second question: theoretically, there is an absolute limit to how old stars can be -- basically, no star can be older than the universe. What you do is you look as far into space as possible to find objects, date them based on their Hubble Shift, and then compare that to the presumed age of the universe. That these stars are pretty close to that limit means that we are looking at some of the oldest stars we will ever see (unless, of course, our theories are wrong, which is always possible).
posted by moonbiter at 9:01 AM on April 6, 2005

Thanks for the explanations, moonbiter and argybarg.

moonbiter: so if the age of a star is limited by how old we think the universe is, is it possible that we could discover a light from a star that would force to recalculate the age of the universe? I guess, what I am asking is, if our understanding of age of a star is based on a complex forumla that is based on a set speed of light, time and distance, could we find a star tomorrow which would suggest that it is older than we thought possible (given how far and long it took the light to travel to us)?
posted by dios at 9:24 AM on April 6, 2005

oh, and thanks for the link, moonbiter. I know what I am doing during my lunchbreak now! Trying to understand that!
posted by dios at 9:25 AM on April 6, 2005

As I understand it, all the space is expanding, things farther away are moving faster away, with red shift, not blue.
So quickly are the farthest things moving away at the "limit" of the universe that they are nearly moving the speed of light away in realation to us, which, once they reach that reletive speed, their light can't reach us anymore, and they blink out.

Is this a correct way to state it?

Would that mean that there are stars farther/older that we can't see, therefore there is no way to judge the age of the universe?
posted by Balisong at 9:34 AM on April 6, 2005

I talked to one of my old astro-editing pals yesterday, and he said that he read a paper about someone who's working on a scale map of the universe, where everything is in proportion to things near it, but the scale changes the further out you go. So Earth and suchlike are in scale, but then there's a scale shift to show you the Milky Way, and then another scale shift to show you nearby galaxies, an on to the edge of the universe. It will show how far any radio signals generated by us have traveled, how far away our current telescope technology will allow us to see, etc. It sounds pretty awesome.
posted by goatdog at 10:04 AM on April 6, 2005

Sounds like a great future FPP, goatdog!

And thanks for that link, moonbiter.
posted by gwint at 11:28 AM on April 6, 2005

dios: As I understand it, yes, but it's highly unlikely.

The process goes something like this:
  1. Astronomers find a distant object.
  2. They derive it's redshift by comparing it's observed spectral profile with what they know the spectral values should be.
  3. They plug this redshift into a distance formula to get it's recession velocity.
  4. Then they plug the recession velocity into Hubble's Law to get the distance, and thus how long ago the object they are seeing existed.
So when an object is found with a higher redshift than previously observed objects, it is assumed to be farther away and therefore older. I believe the highest redshift found yet for an object is around 10.

However two things:
  1. There is a whole lot of observed evidence for setting the age of the universe at 12-14 billion years. Astronomers have basically mapped the whole sky, and all the rest is just filling in the details.
  2. There are also, I believe, a couple of other clues to how old the universe is based on things like the radioactive decay of elements, where the oldest "nearby" stars are in their lifecycles, and in observations based on the cosmic background radiation of the universe. Whatever age estimates you want to make have jive with these figures, or at least be in the same ballpark, to be credible.
Balisong: No, I don't think that is correct. I believe the absolute limit of the observable universe is the noise caused by the cosmic background radiation. Anything that happened before the time when the stuff of the universe cooled below about 3,000 Kelvin is not visible because at that point the universe formed of opaque plasma.
posted by moonbiter at 11:28 AM on April 6, 2005

At least I learned today that "unsymmetrical" is a perfectly cromulent word.
posted by clevershark at 11:33 AM on April 6, 2005

er, the universe was filled with opaque plasma.

odinsdream: No, galaxys are held together by gravitational force and are not subject to Hubble-scale redshifts. But yes, distant, receding objects can often only be seen with long-wave telescopes or other similar recievers like radios (thus the "radio" part of "radio telescopes").
posted by moonbiter at 11:42 AM on April 6, 2005

That answered my questions, thanks moonbiter.

By the way, anyone know of an image on the internet like a 3-d model or map or something that shows the known universe? Thanks!
posted by dios at 11:43 AM on April 6, 2005

dios: Celestia might be able to scratch (a small portion) of that itch.
posted by gwint at 11:49 AM on April 6, 2005

By the way, I should add that I am looking for one that doesn't require downloading anything. I'd just like some nice web-based map that kind of gives a perspective of "Here is the known universe. You are here." Bonus points if the maps is zoomable or rotatable, etc.
posted by dios at 11:50 AM on April 6, 2005

That looks neat gwint. I'll check it out when I get home and can download it. Thanks!
posted by dios at 11:52 AM on April 6, 2005

dios: It's not quite what you're asking for, but this Atlas of the Universe sure is a neat little resource.
posted by moonbiter at 1:07 PM on April 6, 2005

I can’t decide which of these spacesuits that I've created will best prepare me for travel to the ends of the universe. Any idea which one?
posted by dfowler at 1:31 PM on April 6, 2005

What I find really cool is that it's entirely possible that there's a universe beyond ours... in that our universe is defined by that which can be seen or travelled-to by us.

Which is to say that there are possibly parts of the universe which are travelling away from us at such a speed that the light from those stars will never reach us.

Imagine a snail crawling along the surface of a huge balloon that is rapidly expanding: for as long as that expansion continues, it will never, ever reach the other side of the balloon. For all intents and purposes, the far side of the balloon is beyond its universe.
posted by five fresh fish at 2:18 PM on April 6, 2005

Black holes 'do not exist'
These mysterious objects are dark-energy stars, physicist claims.
posted by thomcatspike at 3:46 PM on April 6, 2005

Which is to say that there are possibly parts of the universe which are travelling away from us at such a speed that the light from those stars will never reach us.

As I understand it that is not the case (although again, I must stress that I am no cosmologist). No matter how fast an object is moving away from us (or, in this case, receding from us due to expansion, which is different) light from it will reach us at the speed of light. So sayeth the theory of relativity. The light from the object may be stretched way into the long-wave spectrum, but it's still going to reach us.

I believe the fact that we can see the 3k cosmic background radiation is another clue here. That 3k radiation that we see is the universe as it was when it was merely 300,000 years old, before stars stars, galaxies, and so on were formed. If we can see that, then we should be able to see everything younger than that -- i.e., all the physical objects in the universe.

Of course, if you mean another space-time beyond ours (i.e., parallel universes seperated from ours by some fifth dimension al la the many-worlds theory), then okay, but that's a whole different ball of wax.
posted by moonbiter at 6:03 AM on April 7, 2005

No, I'm pretty sure I'm right. There was a MeFi thread about this sort of thing within the past four months or so, linking to a website that had a very nice Talking To Slow People sort of approach to explaining it all, with pretty pictures to boot.
posted by five fresh fish at 10:39 AM on April 7, 2005

Well, I wish I could find that link. I think you certainly might be right. I think it depends on the brand of cosmology you are following. If you assume an infinite (de Sitter or other) universe, then I believe this is possible. However, if you assume a finite universe then this is not the case (although, if the Hubble constant is really accelerating, then it will be the case at some point in the future).

In the latter theory, I think the key here again is the cosmic background radiation. If the universe were expanding at a rate faster than the speed of light, then we wouldn't see this radiation at all. But since we can see it, and since this radiation represents about as far back in time that you can look, and looking far into space is the same as looking back into time, then there really isn't any room for anything else beyond that radiation.

But then, of course, my understanding of that could be all screwed up. Looks like I've got some reading to do this weekend!
posted by moonbiter at 12:45 PM on April 7, 2005

No, it works for a finite universe. It's just that the "observable universe" for Earth in the Milky Way is different than the universe observed from a distant galaxy. Much of what we see is shared between the universes, but there are places we can see that they can not, and vice versa.

At least, I think that was the gist of it.

Oh - but this might be dependent on the theory that the Hubble constant isn't constant. Or that the speed of light has been changing over time. Or some esoteric idea such as that.
posted by five fresh fish at 1:07 PM on April 7, 2005

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