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1500 questions
10
votes
3 answers
The moon in the first phase visible in the sky is tilted
I never noticed it before that moon I see in the sky is tilted. Does the tilt of the moon in the sky indicate the direction of the Earth's axis and direction of Earth's rotation around the sun?
Wojciech Domalewski
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What is this, red, blue, white twinkling, star?
I am from Germany and at 11 PM I was outside and I saw a star, rapidly twinkling in blue, red and white. At first, I thought it was a plane, but it didn't move.
I took a picture of it, but you can only see a blue-ish dot on the photo.
I am from…
bratbruh
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Salinity of Martian water 3.5 Billion years ago
Was Mars' ocean 3.5 billion years ago salt water or fresh water?
On a related note: would we be able to drink the water that is on Europa?
Peter U
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Why is the L1 point (Lagrange) almost 1 million miles from Earth? Shouldn't it be closer to us?
Try to follow my simple logic:
The Sun is almost exactly 333,000 times as massive as Earth, and gravitational strength increases linearly with mass, so the Sun's gravity is about 333,000 times ours.
The distance from the Earth to L1 is about 932,000…
Kurt Hikes
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2 answers
Which is the closest exoplanet to Earth?
The closest star to Earth (after the Sun) is well-known: Alpha Centauri, 4.3 light years away. But what about the closest exoplanet to Earth, outside of the Solar System?
Zoltán Schmidt
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3 answers
Why is the composition of the sun so distinct from that of earth?
Given that the sun is – in astronomical distances – quite close to the earth, why are the two composed of such distinctly different substances?
Sun Composition
Hydrogen 74.9%
Helium 23.8%
Oxygen ~1%
Carbon 0.3%
Others <1%
Earth Composition
Iron…
Cory Klein
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10
votes
1 answer
Artificial radio waves masked by a star's natural radio waves?
Our civilisation emits radio waves into space. But insofar as the Sun can be modelled as a black body, it is also emitting radio waves into space! For an alien civilisation too far away from us to be able to spatially separate the Earth and Sun…
enigmaticPhysicist
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10
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3 answers
Why does a timelapse video of a stationary Milky Way make the horizon appear to move from horizontal to vertical?
In this video, with a rotating camera keeping the Milky Way 'stationary,' the horizon appears to transition form horizontal to nearly vertical.
I understand the Earth rotates and that it is tilted on its axis as it does so.
However, I can't…
99Gretzky99
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1 answer
Longest line of sight on Mars
It is said that the slope of Olympus Mons is so gradual that the peak cannot be seen from the plain; it is hidden by the planet's curvature. That provokes questions:
How steep is the steepest of the great volcanic peaks?
What is the longest line…
Anton Sherwood
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10
votes
4 answers
Why do satellites appear as streaks in telescope images?
Can you explain me in simple words why the satellite in this telescope image appears as a streak? The exposure time is 1 second.
Gargolla9
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2 answers
Can the gravitational redshift of our sun be measured?
How much of a wavelength change does our sun’s gravity cause in the light it emits? I imagine this could be measured by the shift in its spectral lines. And by extension, does the earth’s gravitational field cause a minuscule blue shift- or does…
aquagremlin
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1 answer
What is sin i in this graph and why is it there?
This is some data presented in a lecture on exoplanets that depicts the distribution of the sizes of super-Earths in comparison to the mass of Jupiter. I would like to know what the argument of the sine function i.e. 'i' implies and why it was…
Ambica Govind
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1 answer
Origin of the magnetic field of neutron stars
It seems a little counter intuitive that neutron stars possess such strong magnetic fields. Its electric charge is presumably zero, so however fast it spins, it shouldn't generate any magnetic field. Or is it due to the electric charges of quarks or…
ashpool
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1 answer
How many iridium layers do we know, besides the K-Pg one (the dinosaur killer "smoking gun")?
The hypothesis of a large asteroid impact playing a role in dinosaurs extinction was strengthened by the discovery of a global iridium anomaly in the geologic record, at the Cretaceous–Paleogene (K-Pg) boundary.
Given we still have several…
ksousa
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0 answers
How well conserved is etendue in extreme gravitational lensing scenarios?
This excellent answer to Could dark matter exist in the Universe in the form of sufficiently dense objects? includes the following image and description:
Light from the background galaxy circles a black hole an increasing number of times, the…
uhoh
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