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Another point here: there was a fairly widespread belief that the moon, stars and planets were not affected by gravity in the same way as “an apple”. The concept of spherical (as in heavenly) material being fundamentally different was still considered roughly accurate. What Newton did using the new calculus (not getting into who came up with calculus in the first place) was provide a physical and mathematical model that would allow for an apple falling, and a moon stating in orbit, without positing that the moon behaved fundamentally differently.

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> Again, my understanding is fairly limited and largely from popular press like a brief history of time and such. So any errors here are all me.

In that case please refrain from commenting, especially on very technical topic such as this one. A good rule of thumb is that if you can't provide peer reviewed sources if asked you probably do not have the required expertise to answer the question to the standards of r/askscience.

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Play with the distances between the two until the image is clear and now you have a telescope. An important discovery as a single lens of the same power would be difficult to make and heavy to carry.

There’s more thorough explanations here already, but quite simply- one bullet would not perceive the other hitting its wall at the same time as itself. Remember that to see the bullet hit the wall, the light from the event has to travel to your eyes. You are equidistant. If the bullet had eyes, that light has to travel that extra distance- wall to wall. It would hit the wall, and slightly later would see it’s companion hit it’s wall.

A more mind bending “paradox” is the ladder paradox in which a ladder contracts to fit in a barn too small for it. I can’t explain it better than wiki here.

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>then how do you find the absolute speed at which the earth moves forward in space?

You don't. You can't. Because there's no such thing. All speed is relative.

IIRC the Aristotle viewpoint was something like, all things are pulled towards the center of the universe, with different elements floating on top of others in the order: earth < water < air < fire (sun) < aether (cosmos).

If you're a video gamer, I highly recommend checking out Odyssey - The Story of Science, an educational game which goes into detail about the "what"s and "why"s of what people believed about the cosmos before modern times, and how each of those theories was disproven.

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Wikipedia says variable speed of light hypothesis is an alternative to the cosmic inflation theory, not a feature of it! I agree with the other commenters, saying something like:

> in the first very very tiny fraction of a second at the birth of the universe, during which the universe expanded faster than the speed of light

makes you look very suspect, since the Hubble parameter is completely separate from the speed of light. It is measured in units of "per second" (though for convenience usually expressed as (km/s)/Mpc). If you check far enough in our present-time universe, you'll find parts of it that are moving away from us faster than the speed of light even now. The first 10^-32 seconds of the inflationary era is not special in that respect.

If the purpose of proposing cosmic inflation (not to be confused with cosmic expansion itself!) is to explain the smoothness of cosmic microwave background (matter could have reached thermal equilibrium before the inflation happened), then it makes sense that proposing a higher speed of light would be an alternative explanation to that!

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Note that that is not the question that you actually asked--in fact, it is much different, because even if "bats have the virus" that wouldn't tell us which bats were the original source ... surely the answer you're looking for as to "which animal" isn't simply "bats".

Precision is important in science. Speaking of which: COVID-19 is a disease. You presumably want to know about the origin of the virus, SARS-CoV-2. This distinction is particularly relevant to your question because an animal might well harbor the virus without having any disease symptoms, or it could have disease symptoms different from those that present in humans.

As for the origin: note that it took 14 years from the first case of SARS-1 until the originating bat population was stumbled upon. For numerous reasons, such a discovery may well never happen for SARS-CoV-2. (One of those possible reasons is something I dare not mention here, but you're likely to run across it if you google "Alina Chan".)

I'm pretty sure "relativity of simultaneity" describes what you're talking about.

The CMB rest frame is the frame in which we calculate the age of the universe, so it's definitely an interesting idea to think about how our elapsed time might differ. However, for 370 km/s motion, the effect of relativistic time dilation is about one part in a million, and the gravitational time dilation (due to the Milky Way's gravitational potential) is of similar order.