eshaya
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How do you determine which star, between two, is more luminous?
1 votes

One way to determine the luminosity of a star is to first determine its distance, d. Then one can use the formula, Luminosity = Flux * 4 * Pi * d$^2$. Flux is related to the apparent brightness that ...

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How Are Radioactive Decay Rates Influenced by Neutrinos - On Earth and Other Dense Planets
1 votes

In the paper that this report is based on, 1, they simply see an annual period in the $\beta$ decay rates of radioactive isotope samples in the lab. Basically, the rate is a fraction of a percent ...

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What's the difference between grism and grating?
1 votes

Transmission gratings on their own introduce chromatic aberration. This is because they change the effective focal length and do so as a function of wavelength. The chromatic aberration can be ...

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Tide on the Moon
1 votes

The tide would be locked in place, roughly, because the Moon always shows the same side to the Earth (tidally locked). But the height of the water at the location facing the Earth and the opposite ...

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Did cosmological inflation occur at speeds greater than $c$?
1 votes

Yes, although we usually do not say the "expansion occurs faster than light." In General Relativity space can be created between all points and that can result in points that were in causal contact (...

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Orbiting supermassive black hole or galactic center of mass?
Accepted answer
1 votes

1) It is the mass internal to the orbit that determines the orbital speeds. These stars are so close to the center that the amount of bulge star mass contained within the orbit would be insignificant ...

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Can astronomical radio sources be used as a verifiable randomness beacon?
1 votes

I see two problems. 1) Any particular source in the sky is above the horizon for a limited region of the Earth at a given time, so one would need to relay the signal around the globe. 2) It is hard ...

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How can cosmological bubble universes "collide" with each other?
0 votes

There is a bit of a semantic mess in multiverse talk. The eternal inflation theory claims that, on the largest scales, inflation (exceptionally rapid expansion) continues for a long time, perhaps ...

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Does gravity repel when dark energy is involved?
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We do not yet know the answer to this question. We observe the universal expansion, which should be slowing down from mutual gravitational attraction, is not slowing down as much as it should and ...

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How did the Ancients understand the ecliptic using the Ptolemaic system
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They saw the stars, planets, Moon and the sun (the Celestial Sphere) rotate around the Earth each day. The Sun however, moved about 1 degree each day across the Celestial Sphere, so by the end of a ...

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In a finite universe, what happens when light reaches the boundary?
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This is one of the most essential questions in cosmology. The first gedankenexperiment probably. If the universe were finite what could be at the boundary? If there were some sort of wall, what would ...

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Calculate time when star is above altitude 30°
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The answer is there on the stjarnhimlen.se site and also stargazing.net. Now we can compute the Sun's altitude above the horizon: sin(h) = sin(lat) * sin(Decl) + cos(lat) * cos(Decl) * cos(LHA) ...

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