The universe is expanding. Into what ?

In summary, the conversation discusses the concept of the expanding universe and whether or not it requires a surrounding space to expand into. It is explained that the math model of expansion does not need a surrounding space and that the math tools exist to define and measure spatial curvature and expansion within the space itself. The conversation also highlights the fact that cosmology is a mathematical science and that the term "expands" is just an approximation for the underlying mathematical concept. While there could potentially be a surrounding space, there is no evidence or need to assume one in current cosmological theories.
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Nick666
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The universe is expanding. Into what ?
 
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The math model of expansion does not need any surround to expand "into".

BTW the math model of the cosmos can be curved without having to sit in some surrounding space to be curved "in".

In 1850 a young guy in Göttingen named Bernie discovered the math tools needed to define and measure both spatial curvature and expansion *internally* without the need for surroundings. You just work within the space itself. You do geometry intrinsically.

So the upshot is that cosmology is a mathematical science---you fit data to math models. It is not a verbal science. So when they say "expands", the word is only the best available English language approximation for the idea. You can't automatically go by words, you have to ask what is really meant. Dig down to the underlying mathematical meaning.

There could be a surround, but since there is no evidence of one, it is more a speculative fairytale fantasy. Cosmologists normally do not assume any surrounding space in which our universe is embedded because there is no indication that one exists, nor is there any conceptual need to assume one.
 
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1. What is the universe expanding into?

The universe is not expanding into anything. It is expanding within itself. This means that the space within the universe is expanding, but there is no external space that it is expanding into.

2. How can the universe be expanding if it is infinite?

The observable universe is expanding, but this does not necessarily mean that the entire universe is infinite. The observable universe is just the portion of the universe that we can see and measure. It is possible that the entire universe is actually finite.

3. Is the expansion of the universe constantly accelerating?

Yes, the expansion of the universe is currently accelerating. This is due to the presence of dark energy, which is a mysterious force that is causing the expansion to speed up. However, it is possible that the expansion could slow down or even reverse in the future.

4. Is the expansion of the universe causing galaxies to move away from each other?

Yes, the expansion of the universe is causing galaxies to move away from each other. This is known as the Hubble flow, named after astronomer Edwin Hubble who first discovered this phenomenon. However, within galaxies, other forces such as gravity can still cause objects to move towards each other.

5. Will the universe eventually stop expanding?

It is currently unknown if the expansion of the universe will ever stop. If dark energy continues to accelerate the expansion, it is possible that the universe will continue expanding forever. However, if the effects of dark energy decrease over time, the expansion could eventually slow down and stop. More research and observations are needed to determine the fate of the universe's expansion.

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