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Stupid Astronomy Question

 
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The Hubble just took a ultra deep space, 1,000,000 second exposure. Astronomers are saying they might have captured images from light that has been traveling for 13 billion years! They are also saying this "old" light might have originated roughly 1 billion years after the big bang...
So I'm trying to imagine how this works, and here's all I can come up with...
The big bang happens and our galaxy heads off in one direction, and these galaxies we just took a picture of head off in the opposite direction. After about a billion years these distant galaxies emitted those particular photons that we just captured. Does that mean that the rate at which our galaxy is moving away from those galaxies is close to the speed of light? So, for instance, maybe from the point of origin of the big bang, we're moving away at .46 the speed of light, and those other galaxies are moving in the opposite direction, also at .46 the speed of light?
I know it's all relative, but I'm amazed to think we've been hauling butt that fast away from the big bang, wow!
I also heard that the rate of expansion is increasing. Does that mean that pretty soon we might be going .46 the speed of light? If so, I guess when we get to .51, we'll never "see" those other galaxies that are exiting at .51 in the other direction...
hmmm....
Did I get this right?
 
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First, Big Bang is out and branes are in. There was no Big Bang originating from a single point, just a couple of 3-D membranes floating in multidimensional space that slapped together and hence we have the Universe. There was no central point that everything expanded out from, but instead a gigantic fireball with hot spots where the two membranes were "closer". The expansion we are witnessing is basically space-time smoothing itself out.
It's wonderfully cyclical. Don't understand the mathematics behind it, but it's still a fun read!
Of course, this theory isn't widely accepted so I was just kidding about the Big Bang being "out" (for all those traditionalists out there), but it still makes for a fascinating read. For anyone out there even remotely interested in physics, if you haven't been reading about string theory, you're missing out on some weird, wacky stuff!
Second, I've seen calculations that say we are moving anywhere from 300 to 600 km/sec. Curious about this myself, seem to be differing opinions?
Third, I don't know if this actually helps you, but this
FAQ sort of talks about what you are asking. I have that site as a favorite and just read through it every now and then to see if I can finally get it all to sink in.... :roll:
 
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JA: FAQ sort of talks about what you are asking.
I've read the explanation from that FAQ, and it kinda makes sense, -- the matter of the Universe "runs away" from the source of light. Except for one thing... Einstein tells us that you can't run away from light. That is, no matter in which direction you are moving or how fast, the speed of light is constant relative to you or anything else. So I am still puzzled, along with Bert.
 
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the speed of light is constant, but if you're moving away from the source of the light and you don't take your own movement into account you perceive it as being slower because it takes longer to reach you.
Over short distances the differences are too small to mean much, but over intergalactic distances it can add up.
If that light has been underway for 13 billion years, something moving at 1 km/sec has travelled 4.1e8 billion kilometers or 410 million billion kilometers.
Of course the light has travelled a lot further, but it would still add up to a delay in reception.
That delay is seen as a frequency shift in the received radiation towards longer wavelengths (red, therefore redshift).
From the magnitude of the redshift we can calculate the relative speeds of ourselves and the body that transmitted the light (there's a known quantity in stellar spectra to be used as a reference which is the known frequency of the light emitted by each element when emitting light).
 
mister krabs
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Bert, the Universe itself is expanding. That means that the farther something is away from us, the faster it is moving away from us. This is the famous "red shift" that hubble (the astronomer) discovered.
Think of the Universe as a big baloon. Draw three dots on the baloon. Make two close to each other and one farther away from the other two. As you blow up the baloon, you will notice that the dots that are close togther get farther apart but the third dot gets much farther than the other two very quickly.
 
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This one still gets me, Bert.
I cannot go faster than the speed of light... relative to what? To you? But here's how it works, as far as I have been able to tell:
Ship A takes off from earth due "north" at c/2. Ship B takes off going due south at c/2. To an observer on the earth, the two ships are going the same speed, c/2. So Ship A must see Ship B going the speed of light, right? And vice versa? Nope.
You have to apply a form of the Lorentz transformation. As close as I can get, the two ships will appear to be going about .75c compared to one another. The kicker? Basically, as Ship A approaches c relative to Earth and Ship B approaches c relative to Earth, they will approach c relative to each other.
I think .
Joe
 
Bert Bates
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Ok -
I'm not thinking about a career change into astro-physics... so in rough terms, would it be fair to say that overall we're separating from these distant galaxies, whose 13 billion year old photons are just now arriving, at approximately .9c, and that maybe .1c or .2c of that .9c is because the universe is expanding? I'm just trying to get a rough "big picture" idea, I don't care about 3rd significant digits, probably not even about 2nd significant digits...
 
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What i would like to chip in at this point is that the light that hubble got was about 13billion years, so that would give you a very big distance away, can they tell what speed the light/star is travelling at away from our planet/solar system? if so add that speed to 13 billion years, and it is pretty far away.
I wonder if my local travel agent can book me on a holiday there, just for a break from work
Hubble took this picture for 1,000,000 secs, did they get a blurry picture???
Davy
 
Thomas Paul
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Originally posted by Bert Bates:
so in rough terms, would it be fair to say that overall we're separating from these distant galaxies, whose 13 billion year old photons are just now arriving, at approximately .9c, and that maybe .1c or .2c of that .9c is because the universe is expanding?

Actually, it's the other way around. Most (perhaps all) of the speed that it is heading away from us is because of the expansion of the Universe. To give you an idea, there are only a few galaxies that are getting closer to us, Andromeda and the Magellanic clouds, and they are all right next door to us so that the expansion of the universe isn't fast enough to push them away from us. Every other galaxy in the universe is getting further way from us because of the expansion of the universe.
 
Bert Bates
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Thomas -
Ok, so maybe a crude analogy... When a surfer catches a wave he does a little paddling at first, but by the time he's riding, most of his velocity is due to the wave, not his paddling.
So maybe we all (us galaxies), got shot out of the big bang at .05c and the other .8c that's separating us is due to the universe's expansion?
 
John Smith
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So maybe we all (us galaxies), got shot out of the big bang at .05c and the other .8c that's separating us is due to the universe's expansion?
Don't miss the other modern cosmological theory that attempts to resolve all the contradictions around the spatio-temporal structure of the Universe. The speed of light now is not what it was before, and the difference could be as high as an order of magnitute. So, whenever you reference c in the formulas, it should be c(t).
 
Bert Bates
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Yes, it's getting easier to understand now...
 
Thomas Paul
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You can safely ignore Eugene. The problem with the theories that Eugene is talking about is that none of them can create a stable universe. If c really was variable then the theories say that atoms shouldn't be stable.
 
John Smith
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Originally posted by Thomas Paul:
You can safely ignore Eugene. The problem with the theories that Eugene is talking about is that none of them can create a stable universe. If c really was variable then the theories say that atoms shouldn't be stable.


No so easy. See, for example, Faster Than the Speed of Light: The Story of a Scientific Speculation, written by a theoretical physicist at London's Imperial College. Admittedly, he is characterized by some of his fellow scientists as a "crackpot", but the science and the scientists are a fascinating subject, covered in the book, too.
 
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Bert Bates--
Good question kicking off this thread. I have posted on this topic in a number of forums before and I will reprint one of my posts below this message for your perusal.
The problem with your statement that kicked off this thread has to do with a misunderstanding of what "relative" means in the Special Theory of Relativity (I myself don't understand Einstein's theories well enough to claim I have an understanding of "relative" as it applies to the General Theory).
The best thing I can say that will help you along (which I refer to in my reprint below) is to think about two spatial dimensions and how they are related. If you picture a horizontal meterstick, how is its x-dimension "relative" to its y-dimension? The stick is 1 meter long, and if its exactly horizontal it makes a projection onto the x-axis of 1 meter (if you were a one-dimensional person who lived in the universe comprised of the x-axis, you would see a stick of one meter in length and not be confused at all). Now if a 2-D person, who lives in the x-y plane started rotating the meterstick, what would the 1-D x-axis person see? He'd see the meterstick start to shrink, and would be boggled if the 2-D guy explained that the stick is still 1 meter long.
Where's that extra distance going, asks the x-axis guy. The 2-D guy tries to explain that there's a trade-off...when he rotates it, it *does* shrink in the x-dimension but grows in some proportion in the y-dimension to account for the rest of the 1 meter that's disappeared (from the x-axis guy's point of view). Oh, ok, says the x-guy...so if I see 0.5 meters here in my world, that means there's 0.5 meters in the y-world, right?
Well, no. When 2-D guy rotates the stick to 45 degrees, that's when 1-D x-guy and 1-D y-guy would see the same lengths--but they wouldn't add up to 1, would they? Pythagoras tells us that the square root of the sum of their squares would, though. WHAT!? says the x-guy. Why should THAT be?
I'll let you take over explaining the meterstick to the x-guy because that's where he really starts to boggle.
However, now if you think of one axis being x (space), and the other being t (time), you'll get a great understanding of the relativity between the two dimensions--with a scaling factor thrown in, it's exactly the same relationship between x and y. (You have to have a scaling factor because in the 2-D space example both axes are in meters...with time and space, one is in seconds and the other is in meters, so it would be amazing coincidence if we had just happened to hit upon equality when we invented the second and the meter...and then there's another subtle difference besides that having to do with i, the square root of -1.)
The relevant part of this analogy, though, is that you and I are the 1-D guy, except we're in 3-D, and Einstein is the 4-D guy trying to explain what he's looking at on the other t-axis we don't physically see...and we're mostly boggling in response.
Anyway, here's my repost now which hopefully you'll find instructive.
sev
Repost:
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At a very basic level, the theory of relativity is based on the idea that no matter how fast you go towards or away from a light source (in a vacuum), the speed of light you measure will always be the same, c.
So if you are in a space ship, and you are not moving with respect to the sun, you can start a stop watch the instant a photon passes the nose of your ship, and stop it the instant it passed the tail of your ship. If you divide the length of your ship (d) by the time (t0) you measured, you'll get d/t0=c. If you head towards the sun and repeat the experiment, you would expect to measure the speed of light relative to your ship to be the distance of your ship (d) over the time you measure (t1) to be d/t1=c+v, where v is the velocity of your ship. You do not -- you get d/t1=c once again. Einstein says this happens because time runs slower for you. So the t1 you measure is greater than it "ought" to be by tDelta. You can figure out what this tDelta factor is simply by substituting the correction (t1-tDelta), the time you "should" have measured, for t1, the time you did measure. If you had measured the time you expected (t1-tDelta), then your guess about light's velocity relative to your ship, c+v, would have been correct:
d/(t1 - tDelta) = v + c
So now we can solve this equation for tDelta to figure out what this correction factor is:
=> d/(v + c) = t1 - tDelta
=> tDelta = t1 - d/(v + c)
So what this equation says is that you logically expect this correction factor to be 0. The time you measure, t1, should be equal to d/(v+c). But when you do the experiment, it's not. The time you measure is *greater* than what it ought to be -- in other words, time "dilates" for you. It takes longer for everything to happen than it should.
Let's say that, alongside the route of your spaceship, I've set up a looooong row of clocks. They all read the exact same time, to the nanosecond, and they're all going. As you rip past them, you note the time on one of them is, say, noon and you start your stopwatch at that instant. After your stopwatch reads 1 minute, if you look out at the clock you're passing at that moment, you will see that it hasn't reached 12:01 yet. It says it's still noon and some number of seconds, like 12:00:45. Your stopwatch got to 12:01 before the clocks outside did. Time runs slower for you -- where you ought to be measuring light's speed at c+v, you're measuring the lower speed of c. This is because time is running slower, therefore in the equation v=d/t, t is increased for you (by how much?), which makes v go down.
Outside, if there's an observer watching you perform this experiment, he might notice that your ship, when stationary, is of length d. However, at the instant you zip past him, the length of your ship appears to him to be contracted. The speed of light v is still c for him, so if he tries to figure out how quickly you zip past a sun's photon, it *would* have been c plus the speed your ship is travelling -- except that your ship appears shorter to him than it ought to be. So the photon and your ship pass each other, from his perspective, faster than c plus the speed of your ship (how much faster?).
If you notice, I asked two questions in parens in the last two paragraphs. Relativity is concerned with answering those questions. It lays out a means of calculating these answers by mathematically explaining what's going on.
If you'd like a conceptual viewpoint, then here ya go. Try not to think of space and time as independent things. Think of a single entity instead, called space-time. Think of holding a meter stick up to an x-y plane, at a 45-degree angle to the axes so that one end is at the origin (along the line y=x). Now, drop down a vertical line from the other end to the x-axis, and a horizontal line from the tip to the y-axis. The distance along the axis represents the "projection" of that meter stick onto that axis. Now give the meter stick a slight rotation, and see what happens to it's projections. If you rotate it 5 degrees in the clockwise direction, you've slightly increased the x-projection and decreased the y-projection.
Think of the x-axis as representing the motion of direction of your space ship, and the y-axis representing the rate that time flows. When you are going towards the sun at 0.5c, what you have essentially done is rotate the meter stick some number of degrees clockwise. In actuality, outside observers will tell you that you contracted your ship -- but you see it as being the same length as always. So you are seeing an elongated projection along the x-axis of our graph. The rate that time flows for you has slowed down as you can see by comparing notes with the outside world (in the same way you compared notes for distance), so your y-axis projection has been shortened.
A lot of people get confused keeping track of what's been seen from what perspective, yadda yadda. This meter stick way of thinking about it is a good thing to remember, because it keeps the perspective the same, and the process of comparing your notes with the outside world is the same, so it becomes clear what has happened. You have slowed time flow (diminished your y-projection) in exchange for elongating space (increased your x-projection). The confusing thing here is that you are likely to say, wait a minute, I did not elongate space -- from my perspective the ship didn't change at all! But you have to remember, you cannot tell anything from one perspective. You can only tell what's happening in your world by comparing it to another. From your perspective, time didn't slow either -- that is, until you compare, you don't realize it because all of your bodily processes, cognition, reasoning, etc, have slowed as part of the time slowdown too. Distance appear to have remained the same to you, though they have actually shortened.
sev
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[ March 20, 2004: Message edited by: sever oon ]
 
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