finding center of universe

phinds

Nicely done video but I am at a complete loss to see how it has ANY bearing on this thread. What am I missing?

FreeMitya

Admittedly, I was responding less to the original post and more to the first post (your post) about how wherever one is in space, one is always at the centre of the universe, and I thought a visual example of the Cosmological principle would be helpful to laymen like myself. Did you skip to 8:20?

phinds

I watched the whole thing, thought the emphasis on black holes made it irrelevant to this thread even though there was some discussion about the center.

FreeMitya

No worries, it's completely understandable.

Thermate

There is a set of non-intersecting world lines, each one at rest relative to the the observable universe. In an expanding universe these world lines move farther apart. Relative rest with respect to the observable universe can be determined by measuring the Doppler shift of the most distant radiation sources.

If an observer is moving relative to the center of mass of the observable universe he will observe a blue shift in the direction toward which he is moving, and a red shift in the opposite direction.

I originally stated this with respect to the cosmic background radiation. That statement is probably still valid, but there's a little catch, that I'm not certain of.

Thermate

Isn't the center of mass the sum of the moments divided by the sum of the masses? Surely that location is not following me around. If I step on the gas, the center of mass of the observable universe is not accelerating with me.

phinds

Do you really think your mass, or the distance you can travel, makes anything other than an infinitesimal difference, compared to the mass of the observable universe and the distance from you to its edge? I stand by my statement.

Thermate

So are you, or are you not moving relative the the center of mass of the observable universe?

Drakkith

Of course you are moving with respect to the center of mass of the OBSERVABLE universe. Just keep in mind that your observable universe changes as you move.

phinds

As Drakkith said, yes you are, but I would add that

1) Your observable universe is being constantly redefined due to motion
2) this is far more due to the movement of the earth/sun/galaxy than to anything you personally can do here on Earth
3) the distance to the edge of your observable universe is about 47 billion light years and all of the motion in #1 is trivial by comparison.
4) Even a much faster motion would not change the fact that the center of mass of your observable universe, due to homogeniety, pretty much follows along with you (the light-cone center is always exactly where you are, by definition)

Thermate

Please provide the sound and valid reasoning that concludes that my observable universe is about 47 billion light years. Does that mean I can see back before the big bang?

Drakkith

That is the radius of the observable universe. The universe has expanded over the last 13.7 billion years and is now the observable universe is much bigger than the 13.7 billion light years one might expect.

Thermate

This may be some kind of gravitational lensing effect. I will grant that the entire concept of time becomes a bit nebulous in this context; nonetheless, one would expect that the observable universe is no larger than the distance light could travel in the age of the universe.

I am aware that there are three 3-planes of simultaneity with respect to the local universal rest frame. Perhaps one of them will account for your ~47 billion year observable scale. I would like to see your sources on this.

phinds

HUH? I'd say you don't understand gravitational lensing. Certainly it has nothing to do with this discussion.

If the universe were totally static, you would be rigth, but it isn't, so you are wrong. It's expanding.

I have no idea what you mean by this. As for a reference of the 47 billion years, get any Cosmology 101 text.

Thermate

Please provide a specific reference. ISBN and page number.

Thermate

OK. I see cosmology has finally caught up with what I was saying decades ago. You are talking about the Universe as treated as simultaneous with the local center of mass of the observable universe. Congratulations to the scientific community! You finally caught up with a high school dropout. As I said, this is a "lensing" effect. One plane of simultaneity is the time that all observers will agree upon when they look at their watches and measure their own time lines relative to the big bang.

Thermate

Really? Has the global curvature of the universe changed in the past 13 billion years?

Another second plane of simultaneity is what actually hit's our eyes. The further back in space you look. the further back in time you see.


Those are the easy ones. Sorry. I can't give you a reference on this, because I only have it as an immediate thought. I don't know that it is written down anywhere.