Beginning/End of the World - Discussion

[Artander]

1. Do you accept the singularity of the Big Bang Theory and other ideas on the beginning of the world?

2. Do you think String Theory is valid? I've seen things that says it's invalid like this new study http://www.wired.com/2014/08/multiverse/

3. This world will end and time itself will end in the Big Rip correct? Accurate estimates on when this will occur yet?

4. You think that there can be another world once this one ceases to exist?

 

[Strange]

1. Do you accept the singularity of the Big Bang Theory and other ideas on the beginning of the world?

 

There is no evidence for any such singularity.

 

2. Do you think String Theory is valid?

 

No idea. As far as I know it hasn't yet made any testable predictions. But I don't think any of the other routes to quantum gravity have either.

 

3. This world will end and time itself will end in the Big Rip correct? Accurate estimates on when this will occur yet?

4. You think that there can be another world once this one ceases to exist?

 

Unknown and unknown.

[IM Egdall]

1. The so-called singularity is where the big bang theory breaks down. At time zero, we get infinite density and infinite spacetime curvature (gravity). When you get infinity for answers it means the equations no longer work. The big bang is the best current scientific theory on the evolution of the universe. Its many predictions have been verified by observations. But no one knows what happened at time zero or what caused the big bang in the first place.

 

2. String theory may or may not be "valid". So far there is no compelling evidence supporting or rejecting its predictions. The theory is notoriously difficult to test.

 

3. Predictions as to how the universe will end are speculation. For one thing, they are based on how dark energy will behave in the future -- but we don't know what dark energy is. If dark energy continues to behave the same way in the future as it does now, the most likely fate of the universe is that it will continue to expand until it consists of enormous black holes surrounded by dead stars. This is when the universe is about a billion billion years old. For details, check out page 266 of my book, Einstein Relatively Simple.

 

4. I think there are planets going around other stars which can and do contain life, some even intelligent life. I base this on the fact that planets seem to be common around stars, there are several hundred billions stars in our galaxy, and there are at least several hundred billion galaxies in the visible universe. And this doesn't take into account the presumably vast number of galaxies and stars out there beyond the part of the universe we can see. Plus the universe may be infinite in extent. We may not be very close to star systems where other life has formed, but it seems to me they are bound to exist.

[Airbrush]

"..... Plus the universe may be infinite in extent...."

 

If the universe began from a finite volume, how does that volume become infinite in a finite period of time?

Edited October 2, 2014 by Airbrush

[Strange]

 

If the universe began from a finite volume, how does that volume become infinite in a finite period of time?

 

If the universe is infinite, then it has always been infinite.

[Airbrush]

1. Do you accept the singularity of the Big Bang Theory and other ideas on the beginning of the world?

2. Do you think String Theory is valid? I've seen things that says it's invalid like this new study http://www.wired.com/2014/08/multiverse/

3. This world will end and time itself will end in the Big Rip correct? Accurate estimates on when this will occur yet?

4. You think that there can be another world once this one ceases to exist?

 

 

The Big Bang theory is currently the leading explanation.

 

String Theory is valid, just not proven.

 

Not a Big Rip. The current leading theory is a Big Freeze.

 

Sure there can be lots of other worlds after this one ceases.

 

If the universe is infinite, then it has always been infinite.

 

Then the Big Bang theory becomes meaningless because you are proposing that the universe was infinite in volume AT the moment of the bang, and most cosmologists believe the universe was smaller than an atom at the start.

[Strange]

 

Then the Big Bang theory becomes meaningless because you are proposing that the universe was infinite in volume AT the moment of the bang, and most cosmologists believe the universe was smaller than an atom at the start.

 

I assume that refers to the observable universe which is, of course, finite.

[Matronics]

 

I assume that refers to the observable universe which is, of course, finite.

The observable universe is finite by don't forget the dark matter, as well as the dark energy.

[Airbrush]

 

I assume that refers to the observable universe which is, of course, finite.

 

Good answer. The popular scientists blunder by not making this point more often. They tend to omit the word "observable". So a universe that is infinite in size was also infinite in size at what moment after the big bang? That is hard to imagine.

Edited October 2, 2014 by Airbrush

[Strange]

 

That is hard to imagine.

 

Indeed. It may be easier to think of the universe becoming less dense, rather than "larger" - which can lead to thinking of it as a large sphere, which may not be accurate.

[Airbrush]

 

Indeed. It may be easier to think of the universe becoming less dense, rather than "larger" - which can lead to thinking of it as a large sphere, which may not be accurate.

 

The concept of a universe infinite in size is often evaded in the popular media, such as the Science Channel. The big bang model of the universe is based upon a universe emerging from a tiny point smaller than a proton. That could only result in a finite universe. If the universe was infinite in size, than "larger" is a meaningless concept. Only a trend towards less density can be detected. The universe is certainly much larger than what is observable. In the far distances, beyond our visual horizon, regions of the universe may be behaving differently. Regions may be growing more dense, just as other regions are becoming less dense, like an infinite foam.

Edited October 5, 2014 by Airbrush

[Strange]

I agree with everything you say. Except ...

 

The big bang model of the universe is based upon a universe emerging from a tiny point smaller than a proton.

 

Which, I think, should say: "The big bang model of the universe is popularly described as being based upon a universe emerging from a tiny point smaller than a proton."

 

Or: "The big bang model of the universe is based upon the observable universe emerging from a tiny point smaller than a proton."

[MigL]

What exactly would be happening at the boundary between a region that is expanding (becoming less dense ) and a region that is contracting ( becoming more dense ) ? Does this make any sense to you Airbrush ?

Finite or infinite, both can expand by simply expanding separation. .

 

As for the observable universe, the areas that are receding from us superluminally ( unobservable ) were once within our observable universe.

As a matter of fact, before the inflationary period, areas of the universe which have vanished beyond the horizon of the observable universe were in causal contact, i.e observable.

IIRC there are mathematical models for finite to become infinite, but it would take me a lot of searching as these were provided by Dr Rocket.

[Airbrush]

If you fill a bucket with soap bubbles, and each bubble is either a big bang or big crunch, some bubbles expand and others contract. On the border between expanding and contracting regions, the density remains relatively constant.

 

Nobody ever explains the mechanics for a big bang that results in a universe that is now infinite in size. They would have to say that before the inflationary period, the universe was already infinite in size, so any "expansion" is just a local trend towards less density.

 

It would be interesting to see the math that allows something finite to become infinite. That sounds impossible to me.

Edited October 6, 2014 by Airbrush

[Strange]

They would have to say that before the inflationary period, the universe was already infinite in size,

 

Yes.

 

 

so any "expansion" is just a local trend towards less density.

 

It doesn't have to be local. An infinite space can globally become less dense.

 

Imagine a ruler which is infinitely long and marked in centimetres (or inches) and over time, all the marks get further apart at every position on the ruler.

 

 

It would be interesting to see the math that allows something finite to become infinite.

 

Imagine that the size increase by a function such as tan(). In a finite time, the size would become infinite.

Edited October 6, 2014 by Strange

[Airbrush]

I don't understand "tan()". What do you mean? I took trigonometry in the 1970s.

 

Infinity is not arrived at by taking any number and divide it by zero. I am looking for something that is not infinite to multiply a finite number by to reach infinity. That is impossible.

 

The difference between a finite number and an infinite number is infinite.

 

If the universe is infinite in size, at what moment after the big bang did it become infinite? Or was the bang itself already infinite in 3 dimensions at time zero plus a Planck time?

 

An infinite universe seems too surreal. More realistically (I can't explain why) the universe is much larger than the observable universe, but not infinite. It should more likely be a finite distribution of matter that transitions to totally empty space. Then perhaps a few Trillion light years away, you may come across another big bang expanding out from a different direction.

 

Or does anyone argue that the universe is most likely infinite in size?

Edited October 6, 2014 by Airbrush

[Strange]

I don't understand "tan()". What do you mean? I took trigonometry in the 1970s.

 

The tangent function. It goes to infinity at pi/2:

http://www.wolframalpha.com/input/?i=plot+y%3Dtan%28x%29+for+x+0+to+pi%2F2

 

 

If the universe is infinite in size, at what moment after the big bang did it become infinite? Or was the bang itself already infinite in 3 dimensions at time zero plus a Planck time?

 

If it is infinite then it was (probably) always infinite.

 

 

An infinite universe seems too surreal.

 

I don't suppose it cares.

 

A finite universe is odd too: why that size?

 

 

It should more likely be a finite distribution of matter that transitions to totally empty space.

 

I would assume there is matter in all of space, even if the universe is finite. If there is empty space then that is part of the universe - how far does that empty space go on?

 

And note that it us space that is expanding, not the matter in space.

 

 

Or does anyone argue that the universe is most likely infinite in size?

 

It is unknown. I'm sure some people prefer one over the other.

[MigL]

Soap bubbles expand and contract at different rates because of the soap film between them, otherwise they would tend toward equilibrium of the contained gases, i.e. equalized pressure.

What do you propose is separating these domains of the universe ?

 

Also separate domains arising because of differences in symmetry breaking lead to other issues. The creation of magnetic monopoles at the boundaries is one such,that I first read about in Guth's Inflation.

 

As far as I know, the consensus is either infinite and unbounded ( no explanation needed ) or finite and unbounded ( such as a sphere's surface ). Unbounded because there cannot be an "outside'.

[hoola]

1no, 2yes, 3no,4 yes...

[Airbrush]

Soap bubbles expand and contract at different rates because of the soap film between them, otherwise they would tend toward equilibrium of the contained gases, i.e. equalized pressure.

 

What do you propose is separating these domains of the universe ?

 

Yes, soap bubbles in not a very good example. Separating regions of expansion and contraction could be vast regions of neither expansion nor contraction? Or an infinite multiverse of occasional, random, big bangs separated by Trillions of light years. Maybe another big bang is about to make contact with our big bang, for a "big collision"?

[EWyatt]

 

If the universe is infinite, then it has always been infinite.

Anytime so-called scientists and wannabees use the word "infinite" when discussing PHYSICAL properties (infinite density, gravity, space, etc...) should make us run away from that discussion. "Infinite density" especially is so illogical, yet over overused. Come on!

[Strange]

Anytime so-called scientists and wannabees use the word "infinite" when discussing PHYSICAL properties (infinite density, gravity, space, etc...) should make us run away from that discussion. "Infinite density" especially is so illogical, yet over overused. Come on!

 

Well, the universe might be infinitely large. Run away from that if you want but there is no real reason to.

[StringJunky]

EWyatt, on 19 Oct 2014 - 4:10 PM, said:

Anytime so-called scientists and wannabees use the word "infinite" when discussing PHYSICAL properties (infinite density, gravity, space, etc...) should make us run away from that discussion. "Infinite density" especially is so illogical, yet over overused. Come on!

I don't think scientists like infinities, it's just what the models tell them and those models have probably gone beyond the limit of their application.

[EWyatt]

 

Well, the universe might be infinitely large. Run away from that if you want but there is no real reason to.

You have a point..... but I was thinking more in terms of matter than "space." But then there's the multiverse concept that points to other universes, thus rendering our "infinite" universe moot. We could go on and on about the size of "space" but without further knowledge of "what's out there" it would all be speculation.

But back to my "infinite" densities, "infinite" gravities as in black holes; I think that's all a crock.

[Strange]

You have a point..... but I was thinking more in terms of matter than "space."

 

Interesting point. I suppose an infinite universe containing a finite amount of amtter is a possib ility, but I don't really know.

 

 

But back to my "infinite" densities, "infinite" gravities as in black holes; I think that's all a crock.

 

I'm not aware of any scientists who think that represents physical reality. Just a limitation of the current model.