Question - the Size of the Universe

[Augustus Windsock]

A simple mind asking a question here
If the universe is 40-odd billion light years across, and expanding all the time, will there be a time when the point from which it all started will be empty and void of planets, stars, dust etc?
In other words will there be nothing at all where ‘the big bang’ came from?

[Grey_Area]

Augustus Windsock said:

A simple mind asking a question here
If the universe is 40-odd billion light years across, and expanding all the time, will there be a time when the point from which it all started will be empty and void of planets, stars, dust etc?
In other words will there be nothing at all where ‘the big bang’ came from?

Fermilab hypotheses suggest in future years, the stars you see now, will no longer be visible to us.

[Bill]

That's the mad thing. It's all pretty much empty...

[Ouroboros]

Humans with monkey brains will never be able to comprehend the universe size. I think only a computer built by a computer will get close.

[JonChalk]

Augustus Windsock said:

A simple mind asking a question here
If the universe is 40-odd billion light years across, and expanding all the time, will there be a time when the point from which it all started will be empty and void of planets, stars, dust etc?
In other words will there be nothing at all where ‘the big bang’ came from?

It's not expanding "from a point" - it's just expanding everywhere in every direction.

Derek Muller's videos are always good:

https://www.youtube.com/watch?v=9DrBQg_n2Uo

[annodomini2]

JonChalk said:

Augustus Windsock said:

A simple mind asking a question here
If the universe is 40-odd billion light years across, and expanding all the time, will there be a time when the point from which it all started will be empty and void of planets, stars, dust etc?
In other words will there be nothing at all where ‘the big bang’ came from?

It's not expanding "from a point" - it's just expanding everywhere in every direction.

Derek Muller's videos are always good:

https://www.youtube.com/watch?v=9DrBQg_n2Uo

Think of it more like cellular mitosis, rather than an expanding balloon.

[Augustus Windsock]

annodomini2 said:

JonChalk said:

Augustus Windsock said:

A simple mind asking a question here
If the universe is 40-odd billion light years across, and expanding all the time, will there be a time when the point from which it all started will be empty and void of planets, stars, dust etc?
In other words will there be nothing at all where ‘the big bang’ came from?

It's not expanding "from a point" - it's just expanding everywhere in every direction.

Derek Muller's videos are always good:

https://www.youtube.com/watch?v=9DrBQg_n2Uo

Think of it more like cellular mitosis, rather than an expanding balloon.

That’s a very unfair reply, you’re asking me to think back 40 years to ‘A’ Level biology lol !

[zetec]

Always fascinates me, the enormity of the universe. 13bn light years away, IIRC if i was to travel at the speed of light, it would take me 13bn years to get there? How long would it take to drive at NSL?

[Derek Smith]

We are told that the light from Earendel took 12.8b years to get to us. The statistic is odd as it doesn't say anything about the distance it is away from us now. As I understand it, it's probably gone out of sight of us, and this little glimmer is a wave goodbye.

How far away from 'us' was it when it burst into its short life? Can we say the spot we exist in now was ever anywhere 12.8b years ago? If the light from this primeval relic of the birth of the universe has taken so long to reach us, how far away was it when it started?

Some used the term radius for a measurement of the universe. Is it possible to measure the diameter at any time? Can it be an absolute?

[annodomini2]

Something 13.4bn lightyears away is estimated to be around 20Bn ly in reality.

If you were traveling close to the speed of light and the expansion of the universe continues to accelerate you could never reach the edge, as while you cannot reach the speed of light, space-time has not such restriction as far as we understand.

[ATG]

JonChalk said:

It's not expanding "from a point" - it's just expanding everywhere in every direction.

It's expanding where there isn't much stuff, which is certainly most of the universe, and therefore a good approximation to everywhere.

[SpudLink]

annodomini2 said:

Something 13.4bn lightyears away is estimated to be around 20Bn ly in reality.

If you were traveling close to the speed of light and the expansion of the universe continues to accelerate you could never reach the edge, as while you cannot reach the speed of light, space-time has not such restriction as far as we understand.

Even the light from our galaxy will never reach the stars that are currently at the edge of the visible universe.

[GroundZero]

Ash_ said:

Ah OK, that helps a lot, so the observable universe is 40b LY (I thought it was 13b LY, or the same as the age of the universe as we understand it, which made sense to my brain). But yes, I now get the expansion idea, if they're travelling at .51c, and the expansion is 0.51c, then to us it's greater than c and we'll never see them?

Yes, age of the universe and size of the universe are not the same thing even though cosmic distances use time as part of the distance measurement.

"Inflation" is the key element to your original post question.
Inflation occurred in a fraction of a second (as the theory goes) and happened to all parts of the universe shortly after the 'big bang', and pushed space along with the matter within it (including light) to vast separation distances (in comparison to the scale and size to what it was before).

This initial inflation sets the 'start point' for which light then has to travel in order for it to be received by other parts of the universe, and from this new start point, it is vastly greater than the 13 billion light years which corresponds to the 'now' age of the universe.

On top of that, the universe is constantly expanding, and has been for 13 billion years. This means from the observable part of the universe, for which we can see over 46 billion light years in all directions, that light is red-shifted due to expanding wave lengths shifting the light in to the longer red wave lengths of the visible spectrum.

Outside of the visible universe, we will never see what is there, this light would have taken many times the age of the universe to reach us, and will now never have the opportunity to reach us after initial inflation due to ongoing expansion, which means at the edge of the observable universe, matter and space is expanding away from us faster than the speed of light.

[Welshbeef]

jimPH said:

SpudLink said:

The Hitchhiker's Guide to the Galaxy said:

Space is big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space.

More stars in the universe, than there are grains of sand in the desert I think was touted on one video I watched.

More or less R4 stat show talked about there being more bees in the world than there are stars in our Galaxy.


The question expanded to then ask in the visible universe how many stars are there - the answer is at least 10 to the power 24 (which as the presenter confirmed is effectively infinite).

It’s shows like that that takes your mind to a different place to consider things - away from WW3 stock market crash covid etc a very welcome break.

[foxbody-87]

What if there have been multiple big bangs and in fact what we class as the universe is just one of many floating around?

[GroundZero]

foxbody-87 said:

What if there have been multiple big bangs and in fact what we class as the universe is just one of many floating around?

There are many theories about the universe origins that have been put forward as observations have been made over the decades. Some seem to fit well with observations whereas others have fallen by the wayside as observations and understandings have developed.

The multiverse theory that you may be eluding to is more in the realms of philosophy rather than science at the moment as there are no empirical measurements that we can conduct to attempt to prove it or to falsify it.

I've always been suspicious of any theory that involves the concept of infinity, one because I usually think its a limitation of the maths equations used in the theory, and two because my brain can't find a comfortable sitting with the concept of infinity. And this is because we are used to earth bound sizes and when we go vastly beyond that we just can't visualise nor properly compare them. Such vast scales only reside in the language of maths.


Edited due to noticing I had waffled off on to a tangent So chopped it down to relevance.

Edited by GroundZero on Saturday 2nd July 11:00

[scottyfocus]

Surely if the Universe is expanding we'd be able to see stars disappearing as they move beyond our 'horizon'. Do we?

Not saying for a minute it's not expanding btw.

My personal opinion is if you had a space ship that could travel fast enough (many many times the speed of light) you could break out our observable universe where you'd just find more universe. Keep going and going and you eventually reach 'the edge' where you can see no more galaxies or stars and it's just empty space. No barrier or anything like that just empty space. Maybe if you travelled through this for hundreds of billions/trillions of light years you may come across another clump of galaxies/stars which could be called another 'universe'.

EDIT: I say that's my opinion, it's not really. Just an idea.

Edited by scottyfocus on Wednesday 13th July 20:15

[GroundZero]

scottyfocus said:

Surely if the Universe is expanding we'd be able to see stars disappearing as they move beyond our 'horizon'. Do we?

Not saying for a minute it's not expanding btw.

My personal opinion is if you had a space ship that could travel fast enough (many many times the speed of light) you could break out our observable universe where you'd just find more universe. Keep going and going and you eventually reach 'the edge' where you can see no more galaxies or stars and it's just empty space. No barrier or anything like that just empty space. Maybe if you travelled through this for hundreds of billions/trillions of light years you may come across another clump of galaxies/stars which could be called another 'universe'.

EDIT: I say that's my opinion, it's not really. Just an idea.

Edited by scottyfocus on Wednesday 13th July 20:15

Yes, they do 'disappear', the way they do this is when the light transmitted from them has their wavelength shifted so much that they first disappear from the visible spectrum, then disappear from the microwave spectrum , then eventually disappear from the radio wave spectrum. By that time they are expanding away from us fast than light speed. The point at which we 'lose visibility' from the EM spectrum from the likes of radio telescopes is defined the extents of the "observable universe".

As the universe continues to expand it will 'push' more and more galaxies away from our 'central position' and as more space-time is positioned between us and other galaxies we'll notice more red-shifting until we lose visibility of them from the EM spectrum. So our night sky over billions of years will eventually go darker and darker.


The faster than light spaceship idea - yes, your theory/idea can't be be proved wrong, other than light speed is not attainable by anything with mass (or anything that interreacts with the Higgs field giving it 'mass'). So as I understand it, to frame it another way, if we received a communication from someone currently at the edge of our defined observable universe, I suspect they would say we are on the edge and they perceive themselves to be in the centre.
It is estimated, not quite sure how, that the entire universe is 250 times times bigger than the observable universe.
But the age old question remains, what is beyond the edge, is there even an edge?

Because as the big bang theory goes, the entire universe came in to existence everywhere at once, some describe this as a "singularity". But essentially as there was "nothing" beforehand, and this means there was nothing beyond the edge of nothing, which sounds obvious, but the theory then suggests everything suddenly appears everywhere, and it becomes a bit of a mind bend.

I think its just a case of our earth bound interpretations of reality do not give us the capacity to visualise removing edges and a necessity to have boundaries is something we have to have for it to make sense.

Once suggestion is, that if you curve space-time so that if the 'edge' is simply the 'left hand end' connected to the 'right hand end' so to speak, then you can remove an 'edge', and then attempt to say that if this can be done in one direction, for it to then be applied in all directions, it may be a "filler" explanation that solves a need for a spatial boundary.

The next step would be to introduce the concept that if you then curve time in a similar manner, so that the beginning of time is connected to the end of time, this will then go down the path of the "continual universes" idea, and also fits with how the eventual end of the universe is visualised.

In that after the death of the last black hole, leading on to much later the death of the last atom, then leading to the death of any form of heat, when every individual location within the dead universe is exactly the same as the other, with no noticeable content, then effectively you have empty space with nothing in it and when that occurs the concept of time dies with it.
With no time, no matter, nothing occurring, this is in effect no existence, which suggests the same sort of situation that could describe the origins of the big bang.

Edited by GroundZero on Thursday 14th July 09:36