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1500 questions
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How bright is the full Earth during the lunar midnight?
At lunar midnight (i.e. the new moon as seen from Earth), the Earth is in its full phase with its entire disk in sunlight, and it is the brightest object in the lunar sky. How bright is it, and how variable is its brightness?
More precisely, I'm…
Emilio Pisanty
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How to determine scalar-to-tensor ratio r from CMB polarization spectrum?
CMB polarization spectrum can tell us about the primordial scalar and tensor perturbation. By analyze B and E mode angular spectrum power spectrum and temperature power spectrum we can determine the scalar-to-tensor ratio r, as many articles…
Ziang Yan
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Planets and Pluto? Neptune?
If one of the rules to be a planet is that it needs to clear ALL objects from their orbit, does this also make Neptune a non-planet? Since it has thus far failed to clear Pluto (and based on an answer from the physics board, the kuiper belt) from…
Lois Leis
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How old is our Sun in Galactic years?
A year is measured as the amount of time it takes Earth to orbit the Sun once, a Galactic year is the time it takes our sun to make one full orbit of the center of the Galaxy.
In Galactic years, how old is our Sun?
user96
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How Does Cosmology Constrain the Number of Neutrino Species?
I've asked this question already on the Physics SE, but I felt it would be worth posting here as well.
I know that based upon theories of structure formation cosmologists can constrain the sum of the masses of neutrinos - if neutrinos were too light…
astromax
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Will an observer falling into a black hole be able to witness any future events in the universe outside the black hole?
I know someone or something sucked into a black hole could not survive, but is the bending of light so immense that an observer falling into a black hole will be able to witness any future events in the universe? That would definitely be cool :D I…
Timtech
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Why does Titan's atmosphere not start to burn?
If Titan has a methane atmosphere and seas of methane, then why doesn't some meteoroid / chemical reaction ignite and blow the whole thing?
cowboysaif
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When will we be able to detect Earth-sized exoplanets?
I have heard that the only planets able to be seen outside the Solar system are Jovian-sized planets with the occasional detection of planets three times the Earth's size. But, as far as I know, we haven't seen any Earth-sized (due to the range of…
Sarah Szabo
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How does interstellar matter density vary?
Answer to my question partially answers this one, about density of intergalactic matter and matter within galaxy:
But it is mostly a hot, ionized void. How void? The density of the intergalactic medium is about 1 to 100 particles per cubic meter…
SF.
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How do we detect if a planet has a liquid core?
In case of Earth, we have many hints about the internal structure of our planet, from what I know, the most important of which is analyzing seismic waves.
Do we have any instruments to detect if other solid planets, such as Mars or Venus, have…
Danubian Sailor
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If we count Avogadro's Number of stars that are closest to Earth, how big that space would be?
I think that the answer to this question will be useful as a scale to appreciate the size of the universe.
So, If we count Avogadro's Number of stars that are closest to Earth, how big that space would be? And how many galaxies/clusters will be…
sampathsris
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Safest Place on Earth from Falling Meteorites
Where on Earth is statistically safer if an asteroid was to break up in the Roche limit and rain meteorites effectively resetting the Earth? I would imagine that a ring of falling meteors would form around the equator making the poles more safe?
Justintimeforfun
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Why is it impossible to infer the surface temperature of Venus by spectroscopy observation from earth?
It is well known that the surface temperature of the sun is determined by fitting the sunlight with the black-body spectrum.
Why is this inappropriate for Venus?
I have the question because of the History SE question When did we figure out that…
S. Kohn
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What's the reason for the hollow region in Oort cloud?
Can someone please tell what caused the hollow space (pointed by yellow arrow) in the Oort Cloud?
I understand that it is called cloud because the cluster of objects does not align with the major rotation axis of our Sun. But, I could not find…
Kevv Keka
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Why is Mercury's orbit so unusual?
Mercury's orbit has the most eccentricity, 0.2, of all the planets. And this orbit is also the most inclined relative to Earth, 7 degrees. Edit: And to the invariable plane, it is inclined 6.35 degrees which is much greater than any other…
DrZ214
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