An interesting notion about inflation.

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Discussion Overview

The discussion revolves around the concept of inflation in the universe and its implications for the size of the universe. Participants explore the relationship between Hubble's parameter and the expansion of the universe, particularly at the moment of the Big Bang, and the challenges posed by mathematical infinities in this context.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant suggests that if the rate of expansion at the Big Bang was infinite, then the universe must now be infinite in size.
  • Another participant argues that if the universe became infinitely large in zero nanoseconds, it has continued to grow infinitely larger every zero nanoseconds since, highlighting the issues with dividing by zero in current mathematical models.
  • A third participant notes that infinities are often seen as mathematical artifacts, indicating a breakdown in theoretical models rather than reflecting reality.
  • A later reply challenges the idea of infinite expansion by using a graph paper analogy, suggesting that while the rate of expansion may be infinite at a specific point, the overall function can still be finite.
  • This participant also mentions the existence of different types of infinities, some of which can be managed mathematically while others complicate the understanding of the universe's expansion.

Areas of Agreement / Disagreement

Participants express differing views on the implications of infinite expansion and the nature of infinities in mathematical models. There is no consensus on whether the universe is infinite in size as a result of infinite expansion.

Contextual Notes

The discussion highlights limitations in current mathematical models when addressing the conditions at the Big Bang and the concept of infinity, particularly in relation to physical reality.

zeromodz
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I was thinking about how big the universe got after inflation occurred. Then I thought about Hubble's parameter.

Ho = V / d (At the big bang, the distance between the two edges of the universe were zero)
Ho = V / 0
Ho = ∞ km*mpc / s

Therefore, the rate of the expansion must have been infinite once the universe started to expand. Wouldn't that mean the universe now must be infinite in size?
 
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If the rate of expansion is infinite, then the universe became infinitely large in zero nanoseconds, and has become infinitely larger every zero nanoseconds since.

This is the problem when we try to divide by zero, which is why the current mathematical models can't take us to the first instant of the BB (or the center of a BlackHole).
 
Infinities are generally regarded as mathematical artifacts - where theory, not reality, has broken down.
 
zeromodz said:
Therefore, the rate of the expansion must have been infinite once the universe started to expand. Wouldn't that mean the universe now must be infinite in size?

No.

Take a piece of graph paper and draw a step function. The rate of expansion is infinite at the step, but the function is finite.

You see these sorts of infinities all the time, and there are a lot of mathematical tools for detailing with them. There are also infinities that "you can deal with" and infinities that really mess things up.
 

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