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The Notion Of A Flat Universe

Aben_Zin said:
Ok so we know the Earth isn't flat. Unless all the people who have sailed around the world etc. are lying.
But is the Universe flat?

Of course we might not know until we've sailed around it...

AZ
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I've always thought this to be a fascinating question!

Obviously our Earth is round - bit wobbly here-and-there, but round - because we're now able to see it all in the round.

Is the Universe round or could it be flat?
Fact is it probably could be any shape whatsoever because we're peering out from the inside!
I think it is our mind-thoughts that are preconditioned to accept that our 'thoughts' and everything we accumulate as knowledge, is round.

When you think about it, each thought or imagining has a boundary - a limitation to thought, and that limitation seems to form a sphere of any, and all possible forms of knowledge. If someone is particularly focused in certain skills in their thoughts or abilities in life, then their horizons might be spherically shaped overall, but with a wavy circumference around their personal sphere. i.e. a lot of variable or general held thoughts would form an imaginary sphere, but maybe with someone who say studies in a particular field, or speciality, might well have a differently shaped imaginary sphere, or boundary - as to what might lay beyond that boundary is anyone's guess.

As to weather the Universe is round, or flat - with all the knowledge that is gained from this 'known' Universe, I guess you could say it may well be round, but it would only be limited to the way we try to make sense of the things that surround us including space itself?
 
Sid said:
... Is the Universe round or could it be flat?
Fact is it probably could be any shape whatsoever because we're peering out from the inside! ...

When you think about it, each thought or imagining has a boundary - a limitation to thought, and that limitation seems to form a sphere of any, and all possible forms of knowledge. ...
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Who's to say our current conceptualization of the cosmos represents an accurate and final account? More simply stated - we're still looking around and thinking about it all.

I'm attaching an image I coincidentally discovered just today and which strikes me as relevant here.

It's a composite of some paradigmatic images associated with the new documentary series Ancient Skies, which premieres tonight on PBS. It shows 4 representative human models of the cosmos and our earth's relationship with it - at least 3 of which are clearly anachronistic.

AncientSkiesPS1.jpg
 
Apparently, the Universe is flat, as opposed to being curved. This implies that it probably goes on forever.

If I ever find the documentary that explained this I'll post a link.

INT21.
 
INT21 said:
Apparently, the Universe is flat, as opposed to being curved. This implies that it probably goes on forever.

If I ever find the documentary that explained this I'll post a link.

INT21.
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Makes me think of a circle - but in reality it's not, it's made up of tiny little flat lines - or quite possibly tiny dots?
 
If I remember it was something to do with the forming of a triangle using two very distant stars as a base line.

The internal angles of this triangle came out as 180 Degree.

If the Universe had not been flat then the curvature would have resulted in either more then 180 or less.
 
Thanks Sid, I'll check that out later today.

By flat I understand it to mean that the Universe is not a self-contained 'spherical entity, but goes on forever in every direction.

INT21.
 
INT21 said:
Thanks Sid, I'll check that out later today.

By flat I understand it to mean that the Universe is not a self-contained 'spherical entity, but goes on forever in every direction.

INT21.
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I wonder 'INT21,' if it would be correct to say that the Universe is a self-contained spherical entity, in that it is an ever expanding self-contained spherical entity that has always increased in every direction, just like an enormous bubble with the initial expanding force lying at it's centre? (In fact, does the Universe have a known centre?)
 
That's a valid point.

Because suggesting that there was a big Bang in which everything that is was once in a super-compressed point would seem to imply an explosion of everything in all directions as the BB unfolded. This would suggest a centre.
I have always been a pit puzzled by what the universe was (and presumably still is) expanding into if there was nothing there to begin with.
Some seem to be suggesting that there was an infinate field of sub-microscopic 'thingies' that suddenly caused the BB to happen.
But this implies that the 'thingy' field as 'somewhere'

All very confusing.

For your further confusion I would recommend Lisa Randall's 'Knocking on Heavens's door'.

INT21.
 
No center has been attributed to the observable universe, and from a theoretical perspective there is no central point in space as we perceive it from which the Big Bang emanated.

It is space itself which is expanding - in equal measure in all directions.

One common misconception, Primack says, is "that the big bang is an explosion that occurred at some point in a preexisting static space--which is not a picture in accord with our modern theory of space-time and gravity." He explains why this image of the big bang as an explosion in space, like the detonation of a bomb, is incorrect:

"According to modern cosmological theory, based on Einstein's General Relativity (our modern theory of gravity), the big bang did not occur somewhere in space; it occupied the whole of space. Indeed, it created space. Distant galaxies are not traveling at a high speed through space; instead, just like our own galaxy, they are moving relatively slowly with respect to any of their neighboring galaxies. It is the expansion of space, between the time when the stars in these distant galaxies emitted light and our telescopes receive it, that causes the wavelength of the light to lengthen (redshift). Space is itself infinitely elastic; it is not expanding into anything."
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https://www.scientificamerican.com/article/according-to-the-big-bang-1999-10-21/

See Also:

http://math.ucr.edu/home/baez/physics/Relativity/GR/centre.html
https://www.loc.gov/rr/scitech/mysteries/universe.html
 
.." He explains why this image of the big bang as an explosion in space, like the detonation of a bomb, is incorrect: ..

I have read this also.

However, they can't have it both ways.

If the Universe started from a point source of any kind (not in a pre-existing space) then that would seem to be the centre of the Universe. And space was formed afterwards.

If it didn't, then the Big Bang theory would not appear to fit anything.

For the BB to have happened 'nowhere' , a nowhere that contained everything, is very difficult to imagine.

Maybe pages of obtuse equations can make it appear sensible.




INT21.
 
INT21 said:
... If the Universe started from a point source of any kind (not in a pre-existing space) then that would seem to be the centre of the Universe. And space was formed afterwards.
If it didn't, then the Big Bang theory would not appear to fit anything.
For the BB to have happened 'nowhere' , a nowhere that contained everything, is very difficult to imagine.
Maybe pages of obtuse equations can make it appear sensible.
Click to expand...

In general, the point (vis a vis abstract physics) is that space / spacetime itself was generated by the Big Bang, and there was no previous space within which the Big Bang's point of origin could be specified.
 
Maybe there is an analogy with the charging of a capacitor. As most of us know, a capacitor never quite reaches it's full charge. it just gets closer.

As the Big Bang can be blamed on Edwin Hubble's graph showing the expansion of the universe, is it possible that Hubble got it wrong. And that his two lines don't intersect at the BB point at all. Maybe they never did.

Just a thought.
 
INT21 said:
... As the Big Bang can be blamed on Edwin Hubble's graph showing the expansion of the universe, is it possible that Hubble got it wrong. And that his two lines don't intersect at the BB point at all. Maybe they never did. ...
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Hubble's basic point about expansion still stands. In terms of the formal models / abstractions, it's not accepted that there is / was a point from which all expansion emanated. The notion there was such a point continues as a popular misconception.

Off hand, I don't know whether Hubble's original description of the expansion effect included a claim such a point existed or could be determined. As such, I don't know whether there was an earlier / original presumption of such a point that could be blamed for the lingering misconception.
 
EnolaGaia said:
Hubble's basic point about expansion still stands. In terms of the formal models / abstractions, it's not accepted that there is / was a point from which all expansion emanated. The notion there was such a point continues as a popular misconception.

.
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So you don't accept the big Bang theory ?

Plus Hubble got it wrong in one respect. He assumed that the expanding Universe would eventually, due to gravity, contract back to it's original size.

But it isn't doing that. In fact it is expanding at an increasing rate.

But, of course, Hubble wasn't to know that at the time.
 
INT21 said:
We are getting a long way from 'Flat Earth'.
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Indeed, so ...

This new thread is being established to contain discussions concerning the universe's expansion per se.
 
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So do you accept the Big Bang theory?
 
INT21 said:
So do you accept the Big Bang theory?
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I don't know why you even ask this ... As a matter of fact I do, having shifted over from my original preference for steady-state hypotheses circa 50 years ago.
 
Obviously the universe is not 2 dimensional. So therefore not flat in the sense of it being some kind of table like shape.
As I understand it, what cosmologists and astronomers mean by “flat” is that as far as we can “see” as limited by the speed of light and the age of it, the universe does not appear to curve back upon itself. Therefore appearing continue to expand in all directions “infinitely”.
 
There have been theories that the Universe is a holographic projection... so if that's true, we're on the surface of a flat plane.
 
Patrick30 said:
Obviously the universe is not 2 dimensional. So therefore not flat in the sense of it being some kind of table like shape.
As I understand it, what cosmologists and astronomers mean by “flat” is that as far as we can “see” as limited by the speed of light and the age of it, the universe does not appear to curve back upon itself. Therefore appearing continue to expand in all directions “infinitely”.
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That's pretty much what I said.
 
EnolaGaia said:
I don't know why you even ask this ... As a matter of fact I do, having shifted over from my original preference for steady-state hypotheses circa 50 years ago.
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I ask because in post #16 above you appear to give the impression you don't accept the Big Bang. Referring to it as a popular misconception.
 
INT21 said:
I ask because in post #16 above you appear to give the impression you don't accept the Big Bang. Referring to it as a popular misconception.
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The popular misconception to which I was referring was the notion there was an already-extant spatial framework into which the Big Bang erupted, leading to the follow-on presumption there would be a specifiable point within this pre-existing spatial framework that marked the point of this eruption.
 
Sid said:
I wonder 'INT21,' if it would be correct to say that the Universe is a self-contained spherical entity, in that it is an ever expanding self-contained spherical entity that has always increased in every direction, just like an enormous bubble with the initial expanding force lying at it's centre? (In fact, does the Universe have a known centre?)
Click to expand...

Yes. Cromer!
 
INT21 said:
That's a valid point.

Because suggesting that there was a big Bang in which everything that is was once in a super-compressed point would seem to imply an explosion of everything in all directions as the BB unfolded. This would suggest a centre.
I have always been a pit puzzled by what the universe was (and presumably still is) expanding into if there was nothing there to begin with.
Some seem to be suggesting that there was an infinate field of sub-microscopic 'thingies' that suddenly caused the BB to happen.
But this implies that the 'thingy' field as 'somewhere'

All very confusing.

For your further confusion I would recommend Lisa Randall's 'Knocking on Heavens's door'.

INT21.
Click to expand...
Another way to theoretically imagine what other kind of action may cause the Universe to expand the way that it has - may well be that it didn't take a 'Big Bang' to get it started, but that the vacuum (space) outside of 'the beginnings' forever pulls everything outwards towards some kind of unknown - bringing about gravity being the opposite product of action and reaction? (Just a thought that's all )
 
Sid,

Could be right.

It would need to be assumed that there was a vacuum there in the first place though. which would imply that there was some kind of 'forever' space that this vacuum was part of. And this 'forever' space was larger than the currently expanding Universe.

But it would make sense if one accepts that an explosion of any kind can only happen if the pressure of the surrounding area is less than the pressure caused by the explosion. Otherwise there would be an implosion.
And if the Big Bang was supposed to originate from a point of super-dense 'matter' it is hard to imagine there being a mechanism to make it any denser.

Probably we will never know.
 
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INT21 said:
Sid,

Could be right.

It would need to be assumed that there was a vacuum there in the first place though. which would imply that there was some kind of 'forever' space that this vacuum was part of. And this 'forever' space was larger than the currently expanding Universe.

But it would make sense if one accepts that an explosion of any kind can only happen if the pressure of the surrounding area is less than the pressure caused by the explosion. Otherwise there would be an implosion.
And if the Big Bang was supposed to originate from a point of super-dense 'matter' it is hard to imagine there being a mechanism to make it any denser.

Probably we will never know.
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The vacuum is there because space has expanded to such a huge size. The matter within is not enough to fill the space. Even so, space is not a complete vacuum.
In the early Universe, the matter created by the Big Bang was closer together, so space (at some point) would have had a dense atmosphere.
 
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