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The elements that make up the bulk of the Earth were part of the presolar nebula. A similar (though not identical) mixture of elements is found in meteoritic material, which is thought to more accurately represent the mean abundances of that nebula (minus the volatiles) and indeed also agrees with the abundance patterns in the Sun. There are grains of ...

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The spatial resolution of a telescope is going to be limited in what it can resolve by something called the diffraction limit. Basically, light can only be focused so much by a lens given its initial starting size and the focal length of the lens. Its useful to think about this in terms of angular resolution for the case of telescopes, and the minimum ...

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There is another big problem with ultra-small luminosities: due to the small initial light + 1/r² decrease, it might be that only a few photons per hour sent by your target planet reach the diameter of Earth (better be in your telescope ! ). At very small luminosity you have to remind that light is not continuous and made of photons. And way before the ...

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All of your questions have no good answer at this point in time. All of them are being researched by physicists, cosmologists, and theorists. We don't even know whether our universe is the only universe or whether what lies beyond the visible universe is just more space like the kind we can see. Our best theories of space and time (Einstein's General ...

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My answer to How does the Hubble parameter change with the age of the universe? (which is itself adapted from Equation for Hubble Value as a function of time) explains how to calculate the scale factor. In fact we calculate the time as a function of the scale factor rather than the other way around. The equation we use is:  t(a) = \frac{1}{H_0}\int_0^a ...

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Your question assumes that the universe started out as a point at the Big Bang and then expanded outwards, however this is not the case. Have a look at my answer to Did the Big Bang happen at a point? for more on this. However your main point remains, that is shouldn't gravity be slowing the expansion, and indeed it did until a few billion years ago. The ...

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