Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[Andir]

You would be at the center, always, because it is a global expansion.

But it's not radial, otherwise it cannot be radial everywhere because it would not retain it's same position in the night sky form every point.  It has to be cubic expansion or the galaxies would collide with each other trying to expand away from some other point (in which case it would actually be pushed toward another galaxy.)

We should be able to draw three lines through our galaxy and divide up the sky by measuring the amount of redshift for galaxies that we think are relatively the same distance, measure that again later and the quadrant of the sky that shifts less should be one of the major axises for the expansion.

[ECrownofFire]

You would be at the center, always, because it is a global expansion.

But it's not radial, otherwise it cannot be radial everywhere because it would not retain it's same position in the night sky form every point.  It has to be cubic expansion or the galaxies would collide with each other trying to expand away from some other point (in which case it would actually be pushed toward another galaxy.)

We should be able to draw three lines through our galaxy and divide up the sky by measuring the amount of redshift for galaxies that we think are relatively the same distance, measure that again later and the quadrant of the sky that shifts less should be one of the major axises for the expansion.

But you can't, because there is no point of origin. You are attempting to find something that isn't there.

By the way, it's not a constant velocity, it's a constant acceleration, it's exponential, because the distance between everything multiplies by X every Y years.

[Il Palazzo]

Man, but it always points exactly toward where you're standing, wherever you go to. You are the center of the universe! Unless you've got a really bad case of megalomania, you should see the ridiculousness of such a conclusion.

You just said the yellow galaxy and another galaxy opposite that are the two most red shifted galaxies and that gave me two points to draw a vector on (that goes through me or damn close.)   This gives me a line of our travel away from the origin of the big bang... and now you are going to tell me that you are taking that back?  (I thought I was getting somewhere...)

But I'm not. It's still the same.

It does go through you exactly. The one yellow galaxy is receeding from you, so the vector points from where you're standing towards it. The other galaxy does the same, but the vector has got the opposite direction. They begin where you are at. The big bang happened in your pants! Which is great, unless you meet another guy who measured the redshifts from his home, and he thinks that his balls are the origin of the universe. Instant fight guaranteed.

You would be at the center, always, because it is a global expansion.

But it's not radial, otherwise it cannot be radial everywhere because it would not retain it's same position in the night sky form every point.  It has to be cubic expansion or the galaxies would collide with each other trying to expand away from some other point (in which case it would actually be pushed toward another galaxy.)

We should be able to draw three lines through our galaxy and divide up the sky by measuring the amount of redshift for galaxies that we think are relatively the same distance, measure that again later and the quadrant of the sky that shifts less should be one of the major axises for the expansion.

Radial means along the radius of the(sky) sphere. What other meaning you had in mind, I don't know.

The same distance produces the same redshift. It's the observational data.

edit:

But you can't, because there is no point of origin. You are attempting to find something that isn't there.

I believe that we're trying to explain here why there isn't one.

[Phmcw]

And there I've been stupid. remember how I said that your experiment would be hard to put in place?
Well, that was retarded from me. Actually that the first thing that Hubble have done when he discovered the red shift, just not formulated the same way. I don't know how I got past this.

Edit:Ha yes, it's was because you spoke about relative position, which is a very hard information to get. But as it's not actually required I should have known better.

If it was an explosion, like you cannot help but think, we would only go away from galaxy that are not aligned with the center of the explosion, like you said, and those who are past the center.

But that is not the case, if you point a telescope on a distant galaxy, you'd find a shift of the colors of the stars toward the red.
This is only consistent with the hypothesis that they are going away from us. The speed calculated of these star is proportional with the distance (hubble's law). So A) we are ring at the center of the "big bang" (actually that  wouldn't work either, but let's keep it that way)
B) the space is inflating. The star doesn't move, they just stay where they are in a growing space.

[ECrownofFire]

But you can't, because there is no point of origin. You are attempting to find something that isn't there.

I believe that we're trying to explain here why there isn't one.

I know that. I'm saying that you can't do it, because we have done roughly the same experiment (same general idea of measuring redshift), and gotten these results.

[malimbar04]

Man, but it always points exactly toward where you're standing, wherever you go to. You are the center of the universe! Unless you've got a really bad case of megalomania, you should see the ridiculousness of such a conclusion.

You just said the yellow galaxy and another galaxy opposite that are the two most red shifted galaxies and that gave me two points to draw a vector on (that goes through me or damn close.)   This gives me a line of our travel away from the origin of the big bang... and now you are going to tell me that you are taking that back?  (I thought I was getting somewhere...)

Spinning in circles, which is what we all do if we are close to understanding something but not QUITE getting it. Keep at it, and when you figure it out it's like "holy... really?... that's cool"

Let's assume we were god for a moment, and we knew where all the stars were relative to ourself.

If there were 4  stars in the universe, it might look something like this:
. <- ourself
.  .  .  . <- the stars

Now, you cold say that the CENTER of the universe is between the middle 2 stars (excluding us of course, sense we're only hypothetical). That is a completely fair statement to make. However, if we contract the stars it would look like this to us:
. . . .
The center of the stars are still between stars 2 and 3, that's still fair. the center is not where it was before though, as you can see we're contracting onto the first star. Indeed, if we were to contract it further...
....
they would get even closer to the first star. The first star is thus the origin. if we contract it all the way to the beginning, we would get
.
and thus we prove that the first star i the origin. But relativity says that's meaningless, because we could have the EXACT SAME experience if we contracted on any of the stars. why not this model?
.  .  .  .
 . . . .
  ....
    .
or perhaps this one?
.  .  .  .
   . . . .
       ...
         .
They're all equally valid.
Now combine that with limit of the speed of light, and relativity, and you'll get the crazy world where they're not only equally valid, but the actual center is the same for each perspective. All things are traveling away from us at the speed of light, and have been doing so for the last however many billion years, relative to us.

[Phmcw]

All things are traveling away from us at the speed of light, and have been doing so for the last however many billion years, relative to us.

hu? Why at the speed of light? They have traveled away from us at the rate of the expansion plus their speed, not the speed of light.

Your earlier point is valid.

[ECrownofFire]

All things are traveling away from us at the speed of light, and have been doing so for the last however many billion years, relative to us.

hu? Why at the speed of light? They have traveled away from us at the rate of the expansion plus their speed, not the speed of light.

Your earlier point is valid.

Not speed, velocity

But they would get very close to the speed of light (and consequently get all sorts of relativity effects).

[malimbar04]

All things are traveling away from us at the speed of light, and have been doing so for the last however many billion years, relative to us.

hu? Why at the speed of light? They have traveled away from us at the rate of the expansion plus their speed, not the speed of light.

Your earlier point is valid.

Oh, sorry. I was a bit fuzzy on teh second point, but I thought it was accurate. Nothing, and especially not galaxies, can travel faster than the speed of light. This is true no matter how fast you are going. For example, imagine 2 people with light-speed rockets traveling away from each other:
A (woo!)<---                 --->(woo!)B
From the perspective of A, B is traveling at the speed of light. From teh perspective of B, A is traveling at the speed of light. Which is crazy, because from the perspective of lonely C as such:
A (woo!)<---         (lonely C)        --->(woo!)B
they're both traveling at the speed of light away from him.


So from A's perspective it looks like this:
A                 CB
But from B's perspective it looks like this:
AC                 B

[Shades]

it's a constant acceleration

I thought there was some disagreement over if it was constant acceleration or a reducing (or even increasing) acceleration. I don't really know enough about the numbers to comment directly but just from what I have discussed with people was that it falls within a fairly wide margin of error.

I realise this is a side issue and doesn't change your point at all.

[ECrownofFire]

Correction: Nothing can travel AT the speed of light either. That would require infinite acceleration, which means infinite thrust, or an infinite amount of time.

it's a constant acceleration

I thought there was some disagreement over if it was constant acceleration or a reducing (or even increasing) acceleration. I don't really know enough about the numbers to comment directly but just from what I have discussed with people was that it falls within a fairly wide margin of error.

I realise this is a side issue and doesn't change your point at all.

It's not including gravity. Huge margin of error, but like you said, it's a side issue.

[Phmcw]

All things are traveling away from us at the speed of light, and have been doing so for the last however many billion years, relative to us.

It's the "all things" that is wrong. Beside I'm not sure that we know hat happen when two bodies are so far away that they should most, relatively to each other, faster than the speed of light, as it's the space that expand, not the object that move by itself.
I didn't have any general relativity, so I don't know.

[Il Palazzo]

Nothing, and especially not galaxies, can travel faster than the speed of light.

Through space, certainly. But if the space itself is stretching, then the apparent velocity of the distant galaxies can exceed the speed of light, making them forever dissapear from our sight(and since no interaction can act faster than the speed of light, it's o.k. to say that they are dissapearing, or escaping, from our universe).
The speed limit(c) of the General Relativity applies only to the movement through space itself.

[malimbar04]

Just a side note...
this is really freaking interesting.

Oh, and you guys are right that I misspoke. they're not all traveling the same rate, and that rate isn't exactly the speed of light (slightly less), but the concept holds still, right?

Nothing, and especially not galaxies, can travel faster than the speed of light.

Through space, certainly. But if the space itself is stretching, then the apparent velocity of the distant galaxies can exceed the speed of light, making them forever dissapear from our sight(and since no interaction can act faster than the speed of light, it's o.k. to say that they are dissapearing, or escaping, from our universe).
The speed limit(c) of the General Relativity applies only to the movement through space itself.

And what is the difference?

[ECrownofFire]

Nothing, and especially not galaxies, can travel faster than the speed of light.

Through space, certainly. But if the space itself is stretching, then the apparent velocity of the distant galaxies can exceed the speed of light, making them forever dissapear from our sight(and since no interaction can act faster than the speed of light, it's o.k. to say that they are dissapearing, or escaping, from our universe).
The speed limit(c) of the General Relativity applies only to the movement through space itself.

And what is the difference?

It's basically the difference between how they appear to be moving, and they are actually moving. They're not actually moving, the space between them is stretching. At least not including gravity and other forces. It's essentially the basis for this entire argument.