Anyone here got a PHD in Physics or even a MS?

Does anybody know where the center of the universe is?  Does it have a center.  Do we think we are the center?  If there was a big bang would that be the center?

Noel

21 minutes ago, FBW737 said:

Anyone here got a PHD in Physics or even a MS?

 

Go back a few posts. The man you want is from Nova Scotia. 👍 Probably the most qualified on the forum.

20 minutes ago, FBW737 said:

Anyone here got a PHD in Physics or even a MS?

Good question. 

I believe that qqwertzde is a physicist if I recall correctly.  He's the most qualified person with whom to discuss these types of subjects. 

The fact is, the Big Bang is a *theory*.   No one really knows how the universe came into existence.  Scientists can make educated guesses regarding the mechanisms involved in the creation of stars, galaxies, and planets, but no one really knows for certain.

It's fun to speculate, though.

Dave

It's "True Confession Time"!  It was me!  A long time ago I had chorizo chili for lunch and I was playing around with a Bic lighter!  'Nuff said 😳💥

4 minutes ago, charliearon said:

and I was playing around with a Bic lighter!

I don't think they had Bic lighters 13.8 billion years ago.

1 hour ago, sightseer said:

Do galaxies further away from us in all directions appear to be moving away faster than those closer?  How is it logical that we would be at the center of anything?

Yes, they fly away from us in all directions, but we are not the center of that motion. Think of our galaxy, and all the other galaxies, as a dot on a balloon. As you inflate the balloon, those dots will all move away from each other, but none of them is at the center. The balloon itself would correspond to space itself expanding. Everything in space is dragged along with that motion.

3 minutes ago, qqwertzde said:

Think of our galaxy, and all the other galaxies, as a dot on a balloon. As you inflate the balloon, those dots will all move away from each other,

This would imply that all galaxies are accelerating from each other at the same rate, would it not?

13 minutes ago, qqwertzde said:

As you inflate the balloon, those dots will all move away from each other, but none of them is at the center.

The center of the balloon is just empty air and the dots on the surface keep moving further away from each other.  Exactly where is the center of the universe or does anybody know?  Is the universe finite or infinite?  If infinite there wouldn't be a center would there?  If it's infinite there would be no boundaries to measure the center from.

Noel

1 hour ago, birdguy said:

If it's infinite there would be no boundaries to measure the center from.

Also, if it really is infinite, then it can't be expanding because then it would be expanding beyond infinity which, strictly speaking, is impossible,

1 hour ago, dmwalker said:

This would imply that all galaxies are accelerating from each other at the same rate, would it not?

This is getting more laborious as I anticipated. In other words: good questions 🙂

Galaxies (and anything in it) do not feel an actual acceleration: you won't feel a force pulling you. What we observe is that galaxies further away are moving away from us faster than galaxies that are nearby. Yes, that looks like they are accelerated (the move away from us, so a little later they are farther away, so they are moving faster), but that is just apparent. Locally, at the position of each galaxy, everything looks quite normal. From a distance, things look different. It is a little bit like if you have a small person standing nearby, and a tall person farther away: the small person may appear taller to you, but if you get closer, you can see that it was only your perspective that caused this.

 

1 hour ago, birdguy said:

The center of the balloon is just empty air and the dots on the surface keep moving further away from each other.  Exactly where is the center of the universe or does anybody know?  Is the universe finite or infinite?  If infinite there wouldn't be a center would there?  If it's infinite there would be no boundaries to measure the center from.

Noel

More good questions. There is no known center of the universe (we can define it to be wherever Noel is right now, but since Peter's position would work equally well, who knows 🙂 ). The balloon, which is a 2D rubber sheet curved in 3D space, is only an analogy. The real universe is a 3D volume curved in 4D space-time. What? You cannot visualize this? Neither can I 😉

But the point is that it is only the expansion of the rubber sheet that matters to explain Big Bang observations. Cut the balloon into a flat rubber sheet and stretch that: the dots will still move away from each other. The spherical shape is unimportant for this analogy.

Is the universe flat or more like a balloon? Both models exist, but nobody knows for sure which model is correct. There are also models that look more like the inside of a balloon. But none of these models actually assumes that there is a center of the universe. In fact, it is a key assumption behind physical cosmology that the universe is homogeneous (there is no preferred point, i.e., no center) and isotropic (it looks the same in all directions).

The universe could be finite or infinite. Most models assume an infinite universe, but that is more because they are mathematically easier to handle. From a practical perspective, the difference is less important than you may think. If your car's mileage (aka our observations) only allow you to travel 1000km or less, it really doesn't matter what happens 10000km from you present position. What matters for physical cosmology is what we can observe, and that's just the visible universe. There may be much more further away, but there is no way we could tell, and no way how this could affect our lives on planet Earth.

Peter

16 minutes ago, dmwalker said:

Also, if it really is infinite, then it can't be expanding because then it would be expanding beyond infinity which, strictly speaking, is impossible,

Yes it can. Imagine an infinite rubber sheet: you can still stretch it and make the dots move away from each other.

8 minutes ago, qqwertzde said:

Imagine an infinite rubber sheet: you can still stretch it

So, infinity is not as limiting as implied by "one divided by zero"?

Edited August 26, 20223 yr by dmwalker

2 hours ago, qqwertzde said:

This is getting more laborious as I anticipated. In other words: good questions

Well...since you don't mind (and are definitely smart and patient):

Is space expanding? yes or no

If (yes):  Is our galaxy getting bigger? (aka is all literal space getting 'bigger'?)

and also; if galaxies are moving away from us at faster and faster rates, wouldn't it be likely that galaxies we used to be able to see, we now can't?

and as a crazy question (yeah...) - how do we know that space is what is changing and not time?  maybe time = 0 at the Bing Bang and the frame keeps expanding (like maybe we're falling into a giant black hole or something 🤐)

Edited August 27, 20223 yr by sightseer

OK, Let's see if I can throw a spanner in the works here.

Is the subject mater of Physics the objects of experience or things in themselves?