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Okay thank you we discussed this in physics class, but the teacher couldn't really answer the question :))

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If time travel were possible, would you end up in the same place on Earth, or would you end up in the same place in the universe, and the earth no longer be there because of it's orbit and the fact that the universe is always expanding?

Yes, this could be a form of phenotypic matching - this individual smells/looks/sounds like me (which also likely involves associative learning)

Excellent list, I've also seen research indicating that in many mammals it seems to be scent that allows the animal to make the identification.

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What if pi was exactly 3?

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That's a bit different because that idea refers to the curvature of space, not spacetime. Space is a 3D surface in 4D spacetime. There are lots of possible choices of spatial surface, but there is a unique choice that makes the universe homogeneous (statistically the same everywhere on the surface). The curvature of this particular choice of spatial surface can indeed inform us as to whether the universe will eventually collapse.

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> The typical answer (summarized) is that "local mass interaction totally overcomes spatial expansion, so only the gravitional effect exists in local systems", but it still seems that there would still have to be some accounting that some of the gravitional "pull" is having to be "used up" to counteract the expansion.

This is indeed the typical answer but it's not correct. Expansion of space doesn't affect particle dynamics at all. It's just a mathematical convention.

See for example this entry of the askscience FAQ

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Not quite because as I noted, dark energy supplies gravitational repulsion. In the big rip, the energy density of dark energy increases over time, and so does the repulsive force. That is what rips everything apart.

(Observations currently do not support that the energy density of dark energy is increasing.)

I am really asking about the trough of the wave. Is this a case where the answer is "it's also a particle Ramen"?

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Yes dogs have unique scents that they can recognize. Whether or not they would remember after years is another question. It would depend on how long they were together before splitting up, what age they were when they split up, and how long they were apart.

No...

https://www.reddit.com/r/cosmology/comments/xr0wlq/i_keep_hearing_all_this_stuff_about_the_james_web/iqcjc2o/

> Is Gravity just a by product of Electromagnetic Force

No, they are completely different things.

If you make something float then you exert an electromagnetic force upwards that's as strong as the gravitational force downwards, leading to a net force of zero. The same applies for e.g. things resting on a table, it's just easier to get it balanced there.

> Everything emits electromagnetic waves

Uncharged particles do not, and very cold objects have negligible emissions.

> everything is impacted by Gravity

... even uncharged particles, and it's essentially independent of temperature.

> If both forces protrude "forever" and become their strongest at a certain "break point"

There is no "break point".

An 1/R^2 law is the natural relation in 3 dimensions as the surface area of a sphere scales with R^(2). Deviations from that relation are special (they need massive exchange particles, for the weak interaction, or strong self-interaction, for gluons).

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