Why Don't We Feel the Universe's Expansion?

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In summary, the expansion of space is only noticeable at large distance scales and is not noticeable for small distances due to the small rate of expansion. Objects are held together by physical forces, such as gravity, which prevents the expansion from affecting their size. However, the expansion can affect smaller things like the wavelength of light over a long period of time. This is typically only seen at very large distances, such as between galaxies that are not part of a bound system. The current rate of expansion is only 1/140 of a percent every million years, making it negligible for small distances.
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Manicwhale
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I can think of two reasons:

1. Expansion is very small, and therefore not noticeable. That is, space expands by 0.00005% in a year (which does not rule out the universe expanding by say, a million light years in a year), so we don't feel it.
2. Everything expands, so we don't notice it. But then... how did we discover it?

Perhaps I'm partially right, but can someone give a thourough explanation?
 
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The first is true. It is only noticeable at large distance scales.
 
  • #3
Thanks.

Also, in terms of why we'd notice it at any scale, would it be right to say that while space expands, certain forces (e.g. EM, or gravity on larger scales) keep objects (e.g. the earth, or galaxies on larger scales) together, so that the distances (as measured by the length of a given object) between objects increase?
 
  • #4
Manicwhale said:
Thanks.

Also, in terms of why we'd notice it at any scale, would it be right to say that while space expands, certain forces (e.g. EM, or gravity on larger scales) keep objects (e.g. the earth, or galaxies on larger scales) together, so that the distances (as measured by the length of a given object) between objects [do not] increase?

did you mean to say "do not increase"?

In that case I would say that you are right. the expansion of space does not affect the size of ordinary objects, or even things as large as the solar system and our galaxy.

As long as they are held together by physical forces or form bound systems.

the expansion of distances can affect smallscale stuff like the wavelength of light, but the undulation track of a wave is not an object held together by forces like a steel rod. the undulations can get stretched out by expansion, over a long period of time

but typically I think of expansion of distances as affecting only really largescale distance like 100 million LY between galaxies that have nothing to do with each other (not part of some gravitationally bound assembly). Probably 10 million LY is far enough.

I think you have it right but just forgot to type in a couple of words
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To reinforce what Russ Watters said. the current rate of expansion is only 1/140 of a percent every million years
or one percent every 140 million years. So for small distances it would be neglible.
 
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FAQ: Why Don't We Feel the Universe's Expansion?

Why can't we feel the expansion of the universe?

The expansion of the universe is happening on a very large scale and is not directly perceivable by our senses. It is happening at a rate of approximately 70 kilometers per second per megaparsec, which is too small to be felt by humans.

How do we know that the universe is expanding if we can't feel it?

Scientists use a variety of methods to measure the expansion of the universe, such as observing the redshift of light from distant galaxies and studying the cosmic microwave background radiation. These measurements provide strong evidence for the expansion of the universe.

Is the expansion of the universe the same everywhere?

No, the expansion of the universe is not uniform. It is believed that the expansion is happening at a faster rate in regions with less matter, such as between galaxy clusters, and at a slower rate in regions with more matter, such as within galaxy clusters.

Will the expansion of the universe ever stop?

Current evidence suggests that the expansion of the universe will continue indefinitely. However, the rate of expansion may change in the future depending on the amount of matter and energy in the universe.

How does the expansion of the universe affect us?

On a day-to-day basis, the expansion of the universe does not have a noticeable impact on our lives. However, it has played a crucial role in the formation and evolution of the universe, and it will continue to shape the future of the universe.

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