Net velocity relative to center of universe?

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Discussion Overview

The discussion revolves around the concept of a "center of the universe" and the implications of relative motion in the context of the universe's expansion. Participants explore theoretical scenarios involving velocities and reference frames, particularly in relation to Einstein's equations and the implications of the Big Bang.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Exploratory

Main Points Raised

  • One participant proposes using Einstein's equation to compare time rates for a stationary observer relative to a presumed center of the universe.
  • Several participants assert that the universe has no center, likening it to the surface of an orange, and argue that the Big Bang occurred everywhere simultaneously rather than at a central point.
  • Another participant expresses confusion regarding the implications of Hubble's discovery of redshift and whether it indicates an expansion from a specific point.
  • Warren explains that while the universe is expanding, it does so without a specific center, using the analogy of raisins in rising bread to illustrate relative motion.
  • A participant questions the possibility of achieving a state of "absolute rest" in space, suggesting that all velocities are relative and dependent on chosen reference points.
  • Another participant challenges the idea of being able to stop completely in space, emphasizing that any state of rest is relative to other objects.
  • Some participants speculate on the implications of redshift, suggesting various interpretations, including the possibility of the Milky Way's location relative to the universe's center or the idea that redshift could be an optical illusion.

Areas of Agreement / Disagreement

Participants generally disagree on the existence of a center of the universe and the implications of relative motion. Multiple competing views remain regarding the interpretation of redshift and the concept of absolute rest.

Contextual Notes

The discussion includes various assumptions about motion and reference frames, with participants highlighting the complexity of defining rest in a dynamic universe. There are unresolved questions about the implications of the Big Bang and the nature of redshift.

munky99999
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Well subject says it all basically... I am assuming the center of the universe is stationary.. I just want to play around with this and punch this into that einstein equation
t1/t=root (1-(v/c)^2)

To see what would be the difference in time rates for a person in a stationary(relative to center of universe) spacestation compared to on earth.
 
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The universe has no center, just like the surface of an orange has no center.

- Warren
 
chroot said:
The universe has no center, just like the surface of an orange has no center.

- Warren

Wasn't the big bang at the center? I'm also pretty sure an orange has a center. Might be a silly analogy i think because I suppose it's possible that the center wouldn't really have anything at it.

Plus it doesn't have to be relative to the center. It could be relative to ANY point in the universe which has absolutely no movement of it's own.
 
The orange's surface, a two-dimensional manifold, has no center. Similarly, the universe has no center.

The big bang did not happen at the "center" of the universe -- it happened at every point in the universe at once, and the entire universe expanded from it. It happened "everywhere," and there is no center.

There is no such place in the universe that has "no movement," as the movement of one object can only defined with reference to other objects. Movement is relative.

- Warren
 
I'm confused now. I thought Hubble discovered the redshift-blueshift deal. Which had shown that there was an expansion of universe/space from a specific point aka big bang.

Has all that been disproven or something? Or am I extremely mistaken on what I'd learnt?
 
The universe is expanding, but not from some specific point. Everything is moving away from everything else.

Imagine a raisin bread as it rises in an oven. The distance between any two raisins is growing larger over time, but no single raisin is the "center" of the expansion. In fact, from the vantage point of any specific raisin, it looks like every other raisin is moving away from it.

- Warren
 
chroot said:
The universe is expanding, but not from some specific point. Everything is moving away from everything else.

Imagine a raisin bread as it rises in an oven. The distance between any two raisins is growing larger over time, but no single raisin is the "center" of the expansion. In fact, from the vantage point of any specific raisin, it looks like every other raisin is moving away from it.

- Warren

Alright how about this.

Alright at TIME=X we have 2 galaxies at positions P1 and P2. We pick any spot between those 2 galaxies. We park our spaceship there and come to an ALL stop. We have absolutely no movement of any kind. Might be an argument from my incredulity, but I can't see how that would be impossible. Even if movement is relative.

I just don't understand. We can figure out our speed spinning on Earth's axis. We can figure out our speed orbitting the sun. We can figure out the speed orbitting around the galaxy core(i think I haven't personally seen this one-I suspect it to be like 250 km/second or so) we can figure out the speed which our galaxy is moving toward (I can't think of the name of the thing. its a local group type thing) which is going towards virgo if I remember correctly. I also suspect the local group is also expanding at some speed outward into space.

All these #'s have to be relative to something which isn't moving at all? Even if it wasn't... we should be able to figure out our specific net velocity(with direction). Take our hypothetical spaceship to a point and come to a deadstop which would be affirmed when we determine that from our position the galaxy is indeed doing exactly that net velocity away from us.
 
munky99999 said:
We park our spaceship there and come to an ALL stop. We have absolutely no movement of any kind.

How can we tell that we have attained this condition?
 
munky99999 said:
All these #'s have to be relative to something which isn't moving at all?

You seem to be missing the point. All the velocities you listed, like our velocity relative to the Sun, are relative velocities. They all involved the movement between one object and another, and are all perfectly valid ways to measure velocities.

But then you come out of left field and expect to create an ALL STOP condition in a spacecraft . Sure, if the universe contains only two galaxies, and you have zero velocity with respect to both, then you can say you've achieved an ALL STOP, but you're still implicitly using those other two galaxies for reference. There's no such thing as ALL STOP without reference to some other object(s). The concept of absolute rest does not exist. There is no such thing as absolute rest.

Even if it wasn't... we should be able to figure out our specific net velocity(with direction). Take our hypothetical spaceship to a point and come to a deadstop which would be affirmed when we determine that from our position the galaxy is indeed doing exactly that net velocity away from us.

Indeed, you can bring your spacecraft into a state of zero velocity with respect to anything in the universe you desire. That doesn't mean that you're in some state of absolute rest; it just means you have zero velocity with respect to that arbitrary object you chose. Even if you have no relative velocity with some galaxy, who's to say that your chosen galaxy is at rest to all the others? What if I chose a different galaxy for my standard of rest? According to my standard, you're not at rest at all. There is no such thing as absolute rest.

- Warren
 
  • #10
Long story short story, nothing is actually stationary in the universe. There is no absolute refrence frame and there is certainly no middle of the universe. The middle of the universe is like saying pick the middle number between 1 and infinity.
 
  • #11
The red shift shows that all galaxies are getting farther apart?
That could mean the universe was expanding and the Milky Way could be located anywhere (except the outer edges).
Or it could mean that our galaxy was near the center of the universe, which could also imply that the Big Bang could have been close. Sounds like creation theory.
Or the red shift could be an optical illusion caused by unknown intergalactic phenomenon.
For example, is it theoretically possible for photons to orbit the sun?
 
  • #12
voltin said:
The red shift shows that all galaxies are getting farther apart?
That could mean the universe was expanding and the Milky Way could be located anywhere (except the outer edges).
Or it could mean that our galaxy was near the center of the universe, which could also imply that the Big Bang could have been close. Sounds like creation theory.
Or the red shift could be an optical illusion caused by unknown intergalactic phenomenon.
For example, is it theoretically possible for photons to orbit the sun?

Welcome to physicsforums voltin.

You are responding to a discussion that has been inactive now for over three years.

As has been explained in the thread, there is no "outer edge", and no "center" for the universe. You can't speak of the "Big Bang" being close. It was about 13.7 billion years away in time, but it was everywhere in space. There's no center to it.

No, it is not possible for photons to orbit the Sun. Photons can "orbit" a sufficiently dense mass, like a black hole, although the "orbit" is not stable. But that is a different subject entirely, not relevant to redshifts.

Cheers -- sylas
 

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