# Is the Universe infinite or not?

• B
• Robertphysics
In summary, the conversation discusses the idea of an infinite universe and the paradox of infinite energy within it. The possible scenarios are presented, including a universe that starts at a singularity and expands to infinity, a universe that begins with a finite amount of matter and expands but remains finite, and a universe that begins everywhere at once. The concept of energy and its conservation is also discussed in relation to these scenarios. The conversation ends with the acknowledgement that there is no definitive answer and that further research and understanding is needed.
- As some of you aleady pointed out; there is a big pitfall of assigning infinity to the universe(possibly);
infinity is a mathematical concept and does not exist in nature. This may seem childish but it isnt't;
if the universe corresponds to a physical version of inifinity I would call it phy-inifinite.
This reduces the effect of posting an absoluteness (concept) to the physical word.
What may help is that those of you who know mathematics know that there are different classes
of infinity. The infinity-class for the range of whole numbers is a different kind then the infinity-class for
the range of real numbers. If the universe would be phy-infinite, then for instance a set of phy-laws
must be developed leading to that result such as QM or GR.

The same pitfall arises,according to me, in string-therory where the most elementary building-block
is a one dimensional string. Same arguments apply; dimensions do not exist in nature, perhaps
phy-dimensions,subttle or isn't it ...?

M.

Hi,
may be another view could help: Is the size of the universe measurable?
If a method could be identified, which allows to determine the size of the universe, then the universe has a finite size.
(Any thinkable means for this kind of measurement would be allowed)

Gerhard Mueller said:
Is the size of the universe measurable?

It depends. The problem is light travel time; any measurement of the size of the universe has to involve light signals (or something equivalent) traveling across the universe. If the universe is spatially infinite, such a measurement could never complete; but it's also possible for it not to complete if the universe is spatially finite.

This topic has been discussed sufficiently. Thread closed.

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