Question What are we expanding into?

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IG2007

"Don't criticize what you can't understand..."
Apr 5, 2020
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IG, I believe we are in agreement on this. The only point I see is that different levels of comprehension can give different levels of understanding.

Cat :)
The point is that, even if you take this analogically, a person in a universe with different number of dimensions from ours (and vice versa too), cannot imagine how the Laws of Physics of another universe be.
 
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Catastrophe

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The point is that, even if you take this analogically, a person in a universe with different number of dimensions from ours (and vice versa too), cannot imagine how the Laws of Physics of another universe be.
I agree completely. And, we are living with it now imho.
 
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Jun 1, 2020
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So, do you mean to say that reality is unscientific? :)
[I missed this post earlier]
More the opposite, since we associate things that are real with real things (a little tautology for fun, but you get the point :)) then science has purview over them. This assumes, of course, that we can measure things that are "real", either directly, indirectly, and sometimes in principle.

More formally, when we talk of things like the meaning of reality, truth, etc. we are more in the realm of philosophy and religion. They even have fancy words like metaphysics - the study of the nature of reality. Whereas science is more about the study of nature. Some physicists like to say that science is an on-going conversation with Nature, and I like that expression.
 
IG, this is getting into semantic difficulties, isn't it? Are you not including space as part of the Universe?
Also "something devoid of space" surely be non-existant, and therefore cannot be expanded into?

Cat :)
A volume of hypothetical pure solidnesss would be existant and also devoid of space, so can't be expanded into.

To confuse matters more I think there are 2 kinds of space:

1. Geometric space, which is not real but just imaginary

2. Real-world tangible space, which allegedly consists of quantum fields and quantum foam.
 
Actually, the Universe is not expanding, it is the space that is. So, a better one would be "space is expanding into something devoid of space."
What do you mean by space? Can I suggest its real-world space that's expanding? as I've just defined above. This means something tangible is expanding. Geometric space is not expanding because it's not real.

The only place devoid of space would be a volume of pure solidness, which I think is impossible since all of matter is mostly space anyway. So in other words I don't think there could be anywhere in the Universe where there's no space. If there's somewhere with no 'real world space' then it would be a void, just geometric space.

Who first said space was expanding, rather than things moving through space? Maybe Helio or rod knows.
 
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It's indeed hard to semantically describe something that doen't exist. Isn't it? :)

I guess, I am still semantically correct. Imagine the way we breathe, when our lungs are devoid of oxygen, oxygen gets into it because of the process of diffusion. In the same way, something that does not exist, has "no thing" and nor space, and thus space tries to fill it up. I guess I am happy with that analogy. I would love to hear comments on that.
It's indeed hard to semantically describe something that doen't exist. Isn't it?
I think it's actually a paradox, or a sentence with no meaning.
 
IG, to me the question is simple. The Universe is said to be expanding. Go back to my flatlander analogy. The expansion is seen by the flatlander (n) as he perceives the area of his world is increasing. To the observer (n + 1) the expansion of the radius is noted. The radius is beyond the comprehension of (n). Thus the expansion cannot be perceived in that dimension by (n) but is perdectly understandable by (n + 1).

Cat :)
I think an intelligent ant on the flatland balloon would realise the curvature of their universe from things such as the angles of a triangle adding up to less than 180 degrees. We also have means to measure the curvature of our universe, which happens to be flat as far as is measurable currently. If our space was curved or even closed we might see the same galaxy by looking in opposite directions. From this it would be possible to deduce, but not perceive, that our universe was embedded in a 4D space.
 

Catastrophe

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This is only an analogy. I have pointed out that it cannot make predictions about the imagined system, other than covered by existing 2D geometry e.g., the flatlander cannot perceive beyond two space dimensions

Cat :)
 
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Catastrophe

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"Real-world space is a tangible 'something' whereas IMO there's no such thing as time, there's only motion. (keeps things simple)"

I have purposely omitted time from the analogy. It is only a simple analogy and is not meant to "work" from our 3-dimensional point of view. I am not claiming anything - only that it provides me with an idea about perception in "higher" dimensions.

Cat :)
 
Feb 8, 2021
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To Spacedweller...Yes nothing really exists, the universes energy is supposed to equal 0, and here we are!
<<Inappropriate comment removed by moderator>>

What are we expanding into?...I am a philosopher scientist spiritualist and I find some of the questions posed here as mental constipation...good luck with that....
I do wonder about how it started and I think we are part of a multiverse, so each universe is expanding into something you could say, ....we came from a former universe that came from ....<<Inappropriate comment removed by moderator>>...
The visible universe is expanding into the inflating -faster than light speed- expansion, in my view, it is flat yet our visible universe is more like a bubble....my personally favorite method of space travel is remote viewing....
 
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Jun 1, 2020
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To confuse matters more I think there are 2 kinds of space:

1. Geometric space, which is not real but just imaginary

2. Real-world tangible space, which allegedly consists of quantum fields and quantum foam.
Yes, this reminds me of Einstein's response to both Friedman and Lemaitre. Einstein thought Friedman's math (your #1) was interesting but Friedman didn't attempt to apply it to physics (your #2). Lemaitre did both. Einstein respected Lemaitre's math but called his physics "abominable". :) [He later seems to have been the first to stand and applaud a speech by Lemaitre.]
 
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Who first said space was expanding, rather than things moving through space? Maybe Helio or rod knows.
Lemaitre likely gets that gold star. Slipher, with extrodinary efforts, was able to get the first real evidence for redshifting nebulae. [Recall that, back then, the view was that the MW was the extent of the Universe. Hubble was just beginning to establish that, as he called them, "extragalactic universes" were galaxies like the MW, at least the spirals.]

Lemaitre's exceptional understanding of GR allowed him to combine the evidence from Slipher and, with Hubble's new distance measurements, introduced his model -- he coined the Primeaval Atom, now known as the BBT. It broke the glass ceiling that was the Static model of the universe. [Hoyle, Gold and ???, failed to get the glass glued-back together in their Steady State model.]

Lemaitre even presented in his original paper an expansion rate for the universe, but he knew it was just a wild shot as more redshifts would be needed. These soon came from Hubble and Humason that established -- with far more accurate measurements -- many more redshifts.

But take note, following Hubble's new data, the revised expansion rate was horribly in error in spite of superior measurements. This was because Hubble, and astronomy, was not aware that Cepheids (used as a new distance measurement) came in two flavors and Hubble used the wrong one that he first found in Andromeda.
 
May 1, 2021
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What are we expanding into?
When you look at reality, which is everything in existence, you acquire a different perspective. The universe resides within the fabric of space-time and is apparently expanding into another fabric within reality that has different properties. We don't know how these different fabrics are related and can only guess what happens when the universe has reached its limit of expansion. I don't see it expanding forever - not if there is another fabric being squeezed. Perhaps when the expansion reaches a critical point, the universe makes another quantum leap into something entirely different with different laws of physics and perhaps more dimensions. Then again, it may reverse course and revert back to the state it was in before the Big Bang.

The law of conservation of energy states that energy can neither be created nor destroyed - only converted from one form of energy to another. in other words, reality is eternal and finite, not infinite. That means there is no infinite void into which the universe can keep expanding. It is puzzling that the expansion is still accelerating after almost 14 billion years. That makes me believe the universe is just a small percentage of a much more complicated reality.
 
Yes, this reminds me of Einstein's response to both Friedman and Lemaitre. Einstein thought Friedman's math (your #1) was interesting but Friedman didn't attempt to apply it to physics (your #2). Lemaitre did both. Einstein respected Lemaitre's math but called his physics "abominable". :) [He later seems to have been the first to stand and applaud a speech by Lemaitre.]
I'm bowled over that my statement reminded you of something that Einstein said. I must admit I'm making some of this stuff up as I go along, and that statement was one such occasion. It just shows the power of this forum, it causes one to think about things that you normally would not do. Not only that, it trains you how to put your thoughts into words. :)
 
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May 1, 2021
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If we assume the space is expanding as well, then we're expanding into nothing.

What is "nothing"?

I don't believe in nothingness or in voids. I believe the conservation of energy law is correct and that we exist in an eternal, finite reality full of energy (no empty spaces or voids) and that things like space and time are properties of that energy. Without a space to occupy and time to move, energy cannot exist, and so it creates them by doing its complex maneuvers. Energy must always have an escape route, which means nothing can destroy or still it.

It's so hard to get our heads around the idea of a reality that had no beginning and will never end, but that's the 'reality' of it.

As far as the expansion of space is concerned, I believe it is expanding into another energetic fabric of reality that may have very different properties.
 
Lemaitre likely gets that gold star. Slipher, with extrodinary efforts, was able to get the first real evidence for redshifting nebulae. [Recall that, back then, the view was that the MW was the extent of the Universe. Hubble was just beginning to establish that, as he called them, "extragalactic universes" were galaxies like the MW, at least the spirals.]

Lemaitre's exceptional understanding of GR allowed him to combine the evidence from Slipher and, with Hubble's new distance measurements, introduced his model -- he coined the Primeaval Atom, now known as the BBT. It broke the glass ceiling that was the Static model of the universe. [Hoyle, Gold and ???, failed to get the glass glued-back together in their Steady State model.]

Lemaitre even presented in his original paper an expansion rate for the universe, but he knew it was just a wild shot as more redshifts would be needed. These soon came from Hubble and Humason that established -- with far more accurate measurements -- many more redshifts.

But take note, following Hubble's new data, the revised expansion rate was horribly in error in spite of superior measurements. This was because Hubble, and astronomy, was not aware that Cepheids (used as a new distance measurement) came in two flavors and Hubble used the wrong one that he first found in Andromeda.
Thanks for your as usual in-depth and clear response.

I'm guessing those people you mentioned thought the redshift might be due to a Doppler shift. Today we call it a cosmological redshift due to the expansion of space. What I really wanted to get at was who was the first too suggest that it was caused by expansion of space and not a Doppler shift, and also what lead to that thinking? Or maybe they came up with the expansion of space idea to start with :)
 
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What does nothing demonstrate? Nothing. Only something can demonstrate something. Imaginations can argue something about nothing, often amounting to nothing, but these arguments come without demonstration.
 
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Thanks for your as usual in-depth and clear response.

I'm guessing those people you mentioned thought the redshift might be due to a Doppler shift. Today we call it a cosmological redshift due to the expansion of space.
Yes, but they anticipated Doppler since stars demonstrate Doppler (ie proper motions). But Slipher found they were moving too fast to be in the MW. Hubble soon showed why.

What I really wanted to get at was who was the first too suggest that it was caused by expansion of space and not a Doppler shift, and also what lead to that thinking? Or maybe they came up with the expansion of space idea to start with :)
Freidman was first to solve GR in a way that revealed the Universe could be expanding or contracting; sitting still,IOW, was highly unlikely. This is why Einstein had to add his very elegant cosmological constant to keep the universe static, which was his bias and the consensus science until Lemaitre broke loose.

But that (Friedman) wasn’t physics, only math.

Einstein’s own cosmic model couldn’t explain known redshifts. DeSitrer’s model from GR demonstrated redshift but he had no matter in his universe! Lemaitre solved this dilemma with expansion .

clummsy iPhone
 
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When you look at reality, which is everything in existence, you acquire a different perspective. The universe resides within the fabric of space-time and is apparently expanding into another fabric within reality that has different properties. We don't know how these different fabrics are related and can only guess what happens when the universe has reached its limit of expansion. I don't see it expanding forever - not if there is another fabric being squeezed. Perhaps when the expansion reaches a critical point, the universe makes another quantum leap into something entirely different with different laws of physics and perhaps more dimensions. Then again, it may reverse course and revert back to the state it was in before the Big Bang.

The law of conservation of energy states that energy can neither be created nor destroyed - only converted from one form of energy to another. in other words, reality is eternal and finite, not infinite. That means there is no infinite void into which the universe can keep expanding. It is puzzling that the expansion is still accelerating after almost 14 billion years. That makes me believe the universe is just a small percentage of a much more complicated reality.
Most of what you say is interesting but you haven't given any ground for saying why reality is finite, you haven't given any reason as to why the other fabric you suggest we are expanding into is not infinite. :)
 

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