Good, I can finally go home.



/ whaddya mean we haven't caught it yet? It's over 10 billion light-years away!
// yes, sir
/// (sob)

Hey science smrt farkers, I have a question.

In the Big Bang Theory, a singularity asplodes and keeps expanding. That is our universe today. I assume it asploded in all directions.

So, what if we (what would become earth) went to the "left" of the explosion but other matter went to the "right" of the explosion. Would we ever be able to see that whole "right" side of the universe?

I wonder because all the light would be traveling away from us since the Big Bang, not towards us.

It is hard to explain what I mean without a 3-D model, but I think you get the jib of my cut.

Earth side here Other side of universe we never see

Or, do universes not work like that?

Dammit, it edited my writing. Try again:

Earth stuff is here .................BOOM..............Other side of universe here

Could we ever see that "other" side, since the light is traveling in the opposite direction?

simple question: what constellation is GN-108036 behind?

MBA Whore: So, what if we (what would become earth) went to the "left" of the explosion but other matter went to the "right" of the explosion. Would we ever be able to see that whole "right" side of the universe?

You're kind of right, but for a reason you don't know about, evidently.

One rule of the universe (that can make some REALLY odd things happen, mind you) is that the speed of light is constant, no matter what. So whether I'm heading away from you at a brisk walking pace or from the rear window of a starship, you'll see that light -- and the light will be traveling at the same speed in either condition. So, even though the "right" half of the universe is moving away from us, that motion isn't keeping us from seeing it.

HOWEVA, there IS a reason why we might not be able to see the "right" half. Some time shortly after the Horrendous Space Kablooie, the universe expanded FASTER than the speed of light (believe it or not, this acutally works without violating the laws of physics). Since the universe expanded faster than any means we have of learning about it (because it kinda tops out at light speed), anything beyond our "Sphere of Ultimate LIght Speed" is lost to us forever (at least without FTL travel).

The weird thing is that this leads to a phenomenon not unlike black holes, in that everything beyond that might as well not exist. It could be as stupendous as a world of unicorn farts and it's as irrelevant to our existence as the planet Mercury to a worm at the bottom of the Pacific Ocean. We live in a bubble within a bubble. That said, our bubble is really, really, REALLY big. Can't exactly complain about not having the biggest house on the block.

They found the owner of the Hotel at the End of the Galaxy?

Relatively Obscure: The blob-shaped galaxy, called GN-108036, is about 12.9 billion light-years away and appears as it existed just 750 million years after the universe began. The universe, for comparison, is about 13.7 billion years old.

[tech4teacher.files.wordpress.com image 320x307]

Thanks, article!

...and they got the math wrong.
Metric Expansion of Space (new window)

TLDR; The edge of the observable universe is about 46 billion light years away.

gilgigamesh: But the sheer distance to the galaxy isn't the only thing to intrigue scientists. The galaxy is also creating stars at a furious pace, making it a rare cosmic find. NASA officials described the galaxy as shining from the "dawn of time," with star formation inside it occurring at a "shockingly high rate."

Does it ever bother anyone else when they talk about this stuff in the present tense? The image is 12.7 billion light years away, which means it is 12.7 billion years old. The galaxy they are looking at perished billions of years ago, and has since been reconstituted into who knows how many successor galaxies.

It may seem pedantic, but I think referring to it in the present tense without some kind of qualifier is confusing to people who don't know any better.

gilgigamesh, it's useless to worry about the present tense vs past tense on cosmic scales. No information can possibly travel faster than light (as far as we know, anyway). That means that not even causes and effects can travel faster than light. So if something is 12.7 billion light years away, by the time we receive the light from it, the activities going on in that galaxy might as well be considered to be happening now. Nothing from that galaxy can possibly affect us until 12.7 billion years later. In other words, our 'now' is different from that galaxy's 'now'.

In fact, objects sufficiently far away can't possibly affect us due to the expansion of the universe because the light, and therefore any information whatsoever, will never ever reach us. Light cones create an event horizon around us. Nothing outside that event horizon can ever affect you. So we're kind of in a gigantic black hole.

What confuses me (and maybe it was addressed upthread and I was just too slow to get it) is this: If we look at look at something 12 or 13 billion ly away, shouldn't that be near the center of the universe? AARRRGH but there's no center!

I get the feeling that when astronomers see these incredibly distant objects, they see them in all different directions in the sky. But how can that be when the universe was smaller back then and these objects were closer together?

Still don't get the "no center" thing. Even a loaf of raisin bread has a center.

How do they know it is forming stars at an alarming rate, when all it is is a faint red dot? Can they really tell that much with xrays and whatnot?

torusXL: the activities going on in that galaxy might as well be considered to be happening now. Nothing from that galaxy can possibly affect us until 12.7 billion years later. In other words, our 'now' is different from that galaxy's 'now'.



machoprogrammer: How do they know it is forming stars at an alarming rate, when all it is is a faint red dot? Can they really tell that much with xrays and whatnot?

Not X-rays per se, but yeah, they can analyze the colors (spectrum) and determine what's going on. For example, I can look at the colors of whatever's oozing out your mom's snatch to find out where she's been.

LDM90: What confuses me (and maybe it was addressed upthread and I was just too slow to get it) is this: If we look at look at something 12 or 13 billion ly away, shouldn't that be near the center of the universe? AARRRGH but there's no center!

Your assploding brain is on the right track, though. Because the universe is expanding, everywhere you look is more or less toward the "center", if there is one.

What complicates any analogy is that any distant observation is also looking back in time. So the simplest example I can think of is, imagine watching a YouTube clip of a smoke bomb going off. Where's the center of the cloud? The bomb itself, of course! But now I add a rule: If I ask you to compare the distance from one part of the cloud to the other (like the part that kinda looks like Jesus to the part that kinda looks like your mom's boobs), you HAVE to move the slider back to earlier in the clip. So as you do so, the cloud appears to shrink (duh). The farther back you go, you realize that ANY part of the cloud earlier in the clip is generally closer to the "center" than any part of the cloud in a later part of the clip. Makes sense, right? The cloud at 0:01 is probably only a foot wide; the cloud at 3:00 is huge. So the vast majority of the smoke particles at 3:00 are farther from the "center" than any particles at 0:01 even if the particle at 0:01 you're looking at is at the very edge of the cloud and the one you're comparing it to at 3:00 is only two feet from the "center". At 3:00 the "0:01 edge particle" may now be 50 feet away, but pointing that out breaks the rule. Given this rule that you can only compare one part of the cloud to parts earlier in the clip, you realize that where the "center" is is less relevant than WHEN it is.

That's the expansion of space-time, at a very very very rudimentary level. You can't just look at two points separated by a vast distance at the same time, because the speed of interactions is finite.

torusXL: t
gilgigamesh, it's useless to worry about the present tense vs past tense on cosmic scales. No information can possibly travel faster than light (as far as we know, anyway).

Except for bad news. Ships powered by that affect stuff before they even arrive.

LDM90: What confuses me (and maybe it was addressed upthread and I was just too slow to get it) is this: If we look at look at something 12 or 13 billion ly away, shouldn't that be near the center of the universe? AARRRGH but there's no center!

I get the feeling that when astronomers see these incredibly distant objects, they see them in all different directions in the sky. But how can that be when the universe was smaller back then and these objects were closer together?

Still don't get the "no center" thing. Even a loaf of raisin bread has a center.

What is believed is that our universe is curved in dimensions over and above the three (plus time) that we normally experience. We can't imagine what three-dimensions curved in a fourth or a fifth looks like, however it can be sort of visualized by an inflating balloon, if we imagine that the three dimensions of our universe are represented by the 2-d surface of the balloon. (This balloon analogy, by the way, represents a "closed" topology, which is only one of three -- or more -- possibilities.) If you live on the surface of a balloon, and you have no way of going "up" (off of the surface) or "down" (into the inside of the balloon), or even comprehending this other dimension, you effectively live in a two dimensional world. The nature of your existence would never be obvious unless you realized that things that didn't make sense with a simple cartesian grid were possible. If the curvature was sufficient, you could, for example, go straight for a ways, turn right 90 degrees and go a similar distance, then turn right and walk ahead again and wind up at the same spot you started at. That wouldn't make sense from a strictly 2-d perspective and you could puzzle out the nature of your "2-d" universe from that. (This would be exactly like traveling eastward along the equator a quarter of the way around the Earth, turning right and traveling to the south pole, and the turning right again and traveling to the point you started from.) But if the balloon were sufficiently large it might elude any attempt to measure any distortions, given limited technology.

To get to the original point, though: if you lived on the surface of a balloon that was being inflated, every point on the balloon would get further and further away from every other. But there is no center. Any point on the surface of the balloon is just like any other.

dragonchild, et al,

Wait, I am confused. So, even if the other half of the universe is moving in the opposite direction (i.e., earth moves left and other stuff moves right), you are saying I could still see it? Even if the light is moving in the opposite direction?

I don't understand. The center asplodes years ago. Light and matter go in all directions. Light and Earth go one way. Other light and matter go the complete opposite way. If the light is traveling in the complete opposite way, then it follows we should never be able to see that light and matter. Correct?

MBA Whore: dragonchild, et al,

Wait, I am confused. So, even if the other half of the universe is moving in the opposite direction (i.e., earth moves left and other stuff moves right), you are saying I could still see it? Even if the light is moving in the opposite direction?

I don't understand. The center asplodes years ago. Light and matter go in all directions. Light and Earth go one way. Other light and matter go the complete opposite way. If the light is traveling in the complete opposite way, then it follows we should never be able to see that light and matter. Correct?

only if it is traveling away at the speed of light. no wait, even then, you would still see it, just all at once, like a sonic boom.

MBA Whore: I don't understand. The center asplodes years ago. Light and matter go in all directions. Light and Earth go one way. Other light and matter go the complete opposite way. If the light is traveling in the complete opposite way, then it follows we should never be able to see that light and matter. Correct?

Well, we gotta keep things specific, here. Let's say there's a star on the other side of the universe. "Direction" is kind of irrelevant here because it emits light in all directions. OK, you're correct in that the light it's emitting AWAY from us won't be seen (at least unless the universe loops around in some trippy way), but considering most stars are round we're not missing much because the light we get looks the same, more or less. Being able to see it or not is about whether it's within the "observable universe" or not. Because of that whole "inflation" thing where the universe might've expanded faster than light, there's a kind of "reality barrier" in place (it's not an actual barrier, more analogous to sky visibility) where light from everything within has had enough time to reach us (that's the "observable universe"), so if it emits light we can see it. Anything beyond, we can't see and may as well not exist regardless of how it's pointing. It's just too far away.

Direction really only relevant in special cases, like gamma-ray bursts and pulsars. These things radiate most of their light in a specific direction, so even if it's a relatively short hop away if it's not pointed right at us we might never know it's there.

MBA Whore: dragonchild, et al,

Wait, I am confused. So, even if the other half of the universe is moving in the opposite direction (i.e., earth moves left and other stuff moves right), you are saying I could still see it? Even if the light is moving in the opposite direction?

I don't understand. The center asplodes years ago. Light and matter go in all directions. Light and Earth go one way. Other light and matter go the complete opposite way. If the light is traveling in the complete opposite way, then it follows we should never be able to see that light and matter. Correct?

And what always blows my mind is that because the light reaches us from the past, there are likely things in the night sky that actually no longer exist and it will take thousands, millions, or billions of years before we ever find out.

Universe is a subjective term.

ABQGOD:And what always blows my mind is that because the light reaches us from the past, there are likely things in the night sky that actually no longer exist and it will take thousands, millions, or billions of years before we ever find out.

Sorry if I'm being pedantic, here -- maybe I'm just misunderstanding you -- buuuut, the light isn't time traveling from the past. The light is an actual object that was created and it's just hanging out in space, chilling in the universe and traveling along, until it traveled far enough to reach our eyes. Think about it like this:

The galaxy began it's existence at some time and created light beams from the area in space occupied by the galaxy. At this same time, there's another area in space that Earth would eventually occupy. The light beam from the galaxy has always been traveling from the galaxy-area to the Earth-area, but meanwhile the space between these two places has constantly been expanding. These areas were originally far enough away from each other that by the time the light finally reached Earth, the expansion of space has caused the light to travel 12.7 billion light-years and therefore take 12.7 billion years. Which means that what we're seeing is information from 12.7 billion years ago. However, we're not magically seeing backwards in time, we're just simply seeing 12.7 billion year old light.

When you read a journal article that says stuff like "peering back in time" or that telescopes are time machines, that's just journalists trying to get people excited. You gotta read between the lines.

torusXL: Sorry if I'm being pedantic, here -- maybe I'm just misunderstanding you

I think it's both, but then again, maybe I'm misunderstanding you now... If you agree that the light that I'm seeing was created and began traveling in the past, why would you say that I'm not also in effect looking into the past? Light takes time to travel; when you look at a clock for instance you're not really seeing the actual time - you're seeing what the clock displayed within the few nanoseconds it took for it to reach your eyes. I'm not suggesting that there's a magical time machine, but it is true that the night sky is not necessarily what those objects currently look like.

All I meant from my original post is that some of the things in the sky burned out long ago and that light of that process will one day be visible.

Someday they are going to realize that the redshift they are seeing is not as simple as they think it is.

ABQGOD: torusXL: Sorry if I'm being pedantic, here -- maybe I'm just misunderstanding you

I think it's both, but then again, maybe I'm misunderstanding you now... If you agree that the light that I'm seeing was created and began traveling in the past, why would you say that I'm not also in effect looking into the past? Light takes time to travel; when you look at a clock for instance you're not really seeing the actual time - you're seeing what the clock displayed within the few nanoseconds it took for it to reach your eyes. I'm not suggesting that there's a magical time machine, but it is true that the night sky is not necessarily what those objects currently look like.

All I meant from my original post is that some of the things in the sky burned out long ago and that light of that process will one day be visible.

Basically, what I was getting at is that the light we see from the galaxy is just an object that exists here and now. There's nothing going on that is making us "see backwards in time". That phrase is just prettier way of saying that we are seeing light which was encoded with information by a process that happened in the past.

tinfoil-hat maggie: AthensBoy: torusXL: t
gilgigamesh, it's useless to worry about the present tense vs past tense on cosmic scales. No information can possibly travel faster than light (as far as we know, anyway).

Except for bad news. Ships powered by that affect stuff before they even arrive.

That's why I prefer bistro mathematics.

Yes, but you must never ask to look at the wine list.