# Explaining Cosmic Inflation using analogies

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• Paolo 2008

#### Paolo 2008

TL;DR Summary
Cosmic Inflation might be explained to the average person using simpler analogies.
An analogy to understand Cosmic Inflation: If the universe grew in size from a subatomic size to the size of a tennis ball (or softball) in a tiny fraction of a second, then a football inflated at the same rate will grow to an approximate size of our solar system. Is this a correct analogy? Wouldn't the football grow to several billion times our solar system? Or just one solar system is more approximate to a plausible analogy?

Here is another analogy I found on Space.com "During this period, the universe doubled in size at least 90 times, going from subatomic-sized to golf-ball-sized almost instantaneously". So, I was wondering if we double a football 90 times, would it grow to be the size of the solar system? Or way larger, I calculated it to be something in the vicinity of 10^25 meters in diameter. Anybody agrees or am I miscalculating?

Without even doing any calculation I can see that it is definitely in the right ballpark in terms of orders of magnitude, which means it is MANY orders of magnitude larger than the milky way, to say nothing of being a bit larger than the solar system.

The magnitude of inflation is, to my mind, literally incomprehensible. It's just numbers. I don't mean to suggest that it's not correct, just that it is WAY far outside of human understanding as anything other than numbers.

Summary: Cosmic Inflation might be explained to the average person using simpler analogies.

An analogy to understand Cosmic Inflation: If the universe grew in size from a subatomic size to the size of a tennis ball (or softball) in a tiny fraction of a second, then a football inflated at the same rate will grow to an approximate size of our solar system. Is this a correct analogy? Wouldn't the football grow to several billion times our solar system? Or just one solar system is more approximate to a plausible analogy?
Some caution. Would it not be better to rather say that the observable universe grew exponentially from subatomic size to a softball size in a tiny fraction of a second. There were probably many, even infinitely many such regions, making up the Universe. Then, without specifying times for simplicity, one can say that a phase transition happened, dumping some of that kinetic energy into particles of matter, bringing the inflation period to an end. From there on it was just decelerating expansion, until dark energy lately again started pushing the observable universe towards exponential expansion again.

Ibix and PeroK