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1500 questions
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Will just a glimpse (less than a second) of sun during partial solar eclipse damage eyes?
This question arose when I thought that on Normal Days, at least I have observed bright sun while going outside, going to office, in park etc. for less than a second. It happens almost daily. Not deliberately but that's how things work I guess.…
Vikas
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How is the Hubble constant determined from gravitational waves?
We know there is a discrepancy between measurements of the Hubble constant, $H_0$. On one side there is the method of the Planck mission, where they use the CMB and the $\Lambda$CDM model to determine the Hubble constant. On the other side, they use…
PrincepsMaximus
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Are there Earth rocks on Mars?
Certain meteorites found on Earth have been established to come from Mars: a giant impact ejected rocks from Mars, these rocks traveled through interplanetary space, and went through the Earth's atmosphere without completely burning up.
Might it be…
usernumber
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Why can't we see a solar eclipse every month?
In every lunar revolution around Earth, the Moon is at a point between the Earth and the Sun. Then why can't we see a solar eclipse once every lunar month?
Is it because of a tilted orbit of the Moon around the Earth? Is the orbit of the Moon some…
Akshat
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Are there any planets or moons denser than Earth?
Earth has the highest density out of all planets, planetoids and moons of our planetary system, and also has a higher density than the Sun. Do we know any exoplanets or moons denser than Earth?
user30007
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How do radio astronomers avoid having their receivers burned out by ground-imaging radar from satellites?
After about 34:00 in the 9th press conference of AAS 235, radio astronomer and NRAO's spectrum manager Harvey Liszt talks about Radio Astronomy in a New Era of Radio Communication and says:
This is a new development that we’re going to have to come…
uhoh
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14
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At Mars' equator how long does twilight last?
With Mars' thinner atmosphere I'm assuming twilight would not last as long compared to the duration on Earth. Has there been any determination of the length of twilight on Mars at the equator or any other latitude?
Bob516
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Any book on `How do they know it (in Astronomy)`?
I am reading my college/undergraduate level astronomy textbook. It has lots of ínfomation but every page raises a similar question in my mind: "How do they know it?". It starts from simple things like radius of Earth, other planets, masses,…
claws
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Why not send a Gaia-like mission to Mars?
This answer to the question why we didn't send Gaia to Neptune's orbit raises the question of why we don't send a Gaia-like mission to the orbit of Mars. It seems like it doesn't have the problems mentioned in the answers, and it would make it…
usernumber
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What are the minimum element requirements for a star?
What elements would be essential for a star to exist?
From what I understand our sun is made of mostly hydrogen and helium and most stars have small amounts of heavier elements like carbon, nitrogen, oxygen and iron.
But could a sun exist on a…
Jake Graham Arnold
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Is it possible that the shadow of The Moon is a single dot during solar eclipse?
During a solar eclipse The Moon covers The Sun on some places on the Earth. Now the focal point is a bit above the Earth so the shadow area is about 160 miles. In history The Moon was a bit closer to the Earth but could there have been a time that…
Marijn
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Why does Titan have an atmosphere while similar moons such as the Galilean moons don't?
The Galilean moons of Jupiter are similar in size to Titan and are also protected by their parent planet's magnetic field. How come only Titan is able to maintain an atmosphere?
Max0815
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How does the Moon's gravity affect Earth's oceans despite Earth's stronger gravitational pull?
Given that Earth has a much stronger gravitational pull than the Moon, how does the Moon have any influence on Earth's oceans?
Steve
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As matter approaches a black hole, does it speed up?
If so, how do we know it speeds up? Doesn't time slow down as gravity increases? If time slows down around a black hole, is it possible matter doesn't actually speed up?
DBWeinstein
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Are astronomers waiting to see something in an image from a gravitational lens that they've already seen in an adjacent image?
@RobJeffries' answer to the question Does gravitational lensing provide time evolution information? points out that there can be a substantial different in arrival times of light from a given source seen in different images from a gravitational…
uhoh
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