# All Questions

6,952 questions
90 views

### Jupiter-Venus conjunction is vertically aligned. I'm at 49° N. How is this possible?

The very beautiful Jupiter Venus conjunction of ~ 2019-01-20 (practically something out of "2001 A Space Odyssey") is seen as "vertically aligned" in the dawn sky, Venus "above" Jupiter. See this ...
25 views

### Do clouds on earth have an affect on a blood moon to the naked eye? [closed]

I was watching the blood moon with a perfectly clear night- using only my naked eyes. At such a micro level, is it possible that all the shimmer I saw was an artefact of our atmosphere or just my poor ...
46 views

### Do integer multiples occur in astronomy data?

I'm a statistics student, currently working on "quantum inference", which is the statistical problem of inference in the quantum model: $y_i = \alpha + \beta x_i + \epsilon_i$ which is similar to a ...
157 views

### Is this a coincidence?

The smallest distance probed in any experiment so far conducted is $10^{-18}$m and the largest distance we can have is the radius of the universe, nearly $10^{26}$m. The ratio is $10^{44}$. In ...
84 views

### What color is the Sky on other Planets?

On Earth, the sky is blue. What color would the sky be on other planets in our solar system? What about outside the solar system? Are there planets with purple skies, or green skies? Or are the all ...
111 views

### When will the last total solar eclipse occur?

Because the moon distance from earth grows, how long will it take, that it is no longer possible to see a total eclipse but only circular eclipses? And does it make a difference if you are on the ...
86 views

### What was the process of calculating how much darkmatter/matter/dark energy the observable universe consists of and how did it come at this conclusion

In 2015 the Planck satellite consortium released an analysis of data collected by the Planck satellite that showed this percentage break down of the universe’s mass/energy. Ordinary matter: 4.9% ...
38 views

### Looking for a 3D animation showing the motion of the sun relative to other stars and the Milky Way, any one seen anything like that?

I am looking for an animation that not only shows the inclination of the solar system respective to the plane of the galaxy, but also shows the motion of the sun relative to and in conjunction with (i....
65 views

### Why do most of the myths behind constellations originate from Greek? [closed]

Why do most of the myths regarding constellations happen to have begun from Greek civilization? Why not other civilizations? Most people who lived in the past era probably observed star patterns in ...
137 views

### Why do we see galaxies with their actual spiral shapes?

Since the actual position of stars is relative, and we see the light they emitted long time ago, and one galaxy has thousands of millions of stars, and those stars can be separated by hundred of ...
88 views

### What are the white reflections on Ceres?

What are the white reflections on Ceres? https://solarsystem.nasa.gov/planets/dwarf-planets/ceres/overview/
114 views

### Is there really a blood wolf moon this month?

Just wondering so I can see it because I don't know if it is happening this month or not?
162 views

### How stable is our universe?

I've been reading and thinking about this subject for some time but i can't seem to find a clear answer. after reading : Aspects of the Higgs boson suggest that our universe is only “marginally ...
60 views

### If Earth suddenly stops rotating, will be thrown at 465 m/s? [duplicate]

If Earth suddenly stops rotating, will be thrown at 465 m/s ?
114 views

### Why doesn't a singularity spin infinitely fast?

A question for a random reader passing through: because of the nature of things spinning faster when it gets smaller, wouldn't a singularity spin infinitely fast as it's infinitely small, if it has a ...
150 views

### Universe isn't infinite theory

Forgive me if any of my terminology is off I am no physicist but I have wondered about this question for a while. I have read in various books that if the universe was infinite, and uniformly created ...
38 views

### Possibility of certain conditions on a planet [closed]

I want to know if there can be any planet that can fulfill the following conditions and if any planet has been observed with such characteristics: The planet must not be tidally locked. The day-night ...
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### Tidally locked, and yet spinning?

Reading about Uranus almost 90° tilt, I was wondering if some rocky planet with mass concentration at one pole could possibly spin around its own axis, while still being locked to its star? Which ...
88 views

### How fast would an object at cruising altitude(around 10,600 m) need to travel to stay on the opposite side of the Earth to the Moon?

I am trying to figure out how fast an object will have to travel (at a height around 10,600 m) to never be in the presence of the moon. Meaning the object will always be on the opposite side of the ...
171 views

### Why is Uranus able to support a regular satellite system?

Uranus has an obliquity of 98° which means that the mutual inclination between a satellite orbiting in its equatorial plane and the orbit of Uranus around the Sun would exceed the critical angle for ...
84 views

### How to Distinguish between Temperature and Doppler effect using Black-body radiation?

I understand that the radiation of a body can be described using the curve for black-body radiation. In the sense that a hotter body will be blue shifted and a cooler body will be red shifted. The ...
56 views

### Why is it that night has a almost a bluish tint to it instead of red?

From my understanding/been told, the color red has the ability to travel the farthest in our atmosphere, being the reason why we have red sunsets and such. But with this in mind, why is it that at ...
168 views

### Why haven't detected life in the universe?

It would seem that if life were relatively common in the universe that there would be a cacophony of noise somewhere in the electromagnetic spectrum. Is life so rare and distant that the waves haven't ...
39 views

### Pekin Chang'e 4 Mission, Shadow?

Hi there this my first post here! I'm wondering with is there shadow under the Yutu 2 rover, of Chang'e 4 mission, since it should be on the far/dark side of the moon. https://www.space.com/42981-...
95 views

### Are other planets' gravity measurable on Earth?

I understand that we can calculate the gravitational force other planets exert on Earth, but can it be measured?
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### What are the challenges for the building and data analysis of the CHIME telescope?

CHIME has discovered the second repeated fast fast burst recently. However, its structure is simple apparently. I wonder why we did not build a telescope before. What is the challenge? I just know its ...
46 views

### Simulating Noise in Astronomical Images

I want to add realistic noise to a simulated image but I am a little confused about the process. I want to have some Gaussian random noise representing the readout noise and to also add Poisson noise ...
235 views

### Why doesn't the vertical light beam get out of a black hole?

I'm asking this question as a follow-up to if light has no mass why is it affected by gravity? Imagine you’re standing on a gedanken planet, shining a laser beam straight up into space. The light ...
45 views

### How far away was the binary black hole that produced GW170729?

GW170729 was gravitational wave signal's detected by the Virgo and LIGO detectors. I read the following in a news report: Known as GW170729, in accordance with the date of its discovery (in US ...
92 views

### What object in the universe is most opaque to neutrinos?

I had this thought, and my first guess was "high density = lots of absorption, so I guess it's neutron stars" but this physics.se question about that has a great answer which covers why that's ...
31 views

### Computing the local orbital frame vector directions in a geocentric reference frame

In the context of the study of a cubesat (little satellite), I am asked to define the local orbital frame and compute the local orbital frame vector directions as a function of time : Here the ...
47 views

### Can radioactive decay rates be confirmed by looking at supernova?

Radiometric dating relies on accurate knowledge of the half-lives of radioactive elements. Skeptics have argued that since many elements' half-lives are too long for anyone to have observed them, we ...
46 views

### Earth rising and setting from moon's perspective

Why the earth is rising and setting seen from the moon, when the moon is tidally locked? Shouldn't the earth be always on the same spot because of the tidal lock, if observed from the moon?
52 views

### preserve information in a black hole

How is information preserved on the surface of a black hole? Is there an compression algorithm for storing the information? What if there is a uniformaly complex object dropped to the black hole? ...
77 views

### In planetary and astronomical science, what exactly is, or is not, a tidal force?

I'm wondering exactly in which situations forces between bodies are, and are not consider to be tidal forces in the context of planetary and astronomical science. If two rigid, non-deformable ...
20 views

### Estimate the number of pixels required to map the full primary beam of a Radio Telescope station

I am practising some exam questions for a radio interferometry exam, and I am struggling with this question: The physical size of a single LOFAR station, operating at 150MHz is about 50m. Estimate ...
111 views

### How does science knows what is the early universe?

I've read about Hubble seeing the brightest quasar in the early universe. Question is, how does science knows what is early and what is late? Please correct me if I'm wondering, but after the big ...
3k views

### Are we really star-stuff from the interior of collapsing stars?

Carl Sagan has said several times that we are "star-stuff". One instance can be found in Good Reads' Carl Sagan > Quotes > Quotable Quote: The nitrogen in our DNA, the calcium in our teeth, the ...
979 views

### Was Earth closer to Europa on 1983-11-25 or 1985-07-22?

xkcd #2003: gives a humorous line of succession to the United States presidency. The comic's title text, found by hovering over the comic, states that a tie is broken by whoever was closest to the ...
49 views

### Any pictures showing difference in moon between southern and northern observers?

Since observers in different parts of Earth will be observing the moon at slightly different angles relative to its (choose reference vector: north pole, origin of latitude longitude position, ...
23 views

### How tightly clustered are the CHIME-detected FRB repeats?

In the past few days, journalists have been playing the usual "X could be aliens" game. This time, X is repeating FRBs from a galaxy 1.5 billion light years away. (Or is it 1.5 billion years ago? The ...
44 views

### How to get ephemeris data for location?

How can I obtain ephemeris data which fits to a specific location? Differently phrased: I need ephemeris data of satellites which orbited a specific location. Is there a document where I can look up ...
13k views

### If light has no mass, why is it affected by gravity?

Light doesn’t accelerate in a gravitational field, which things with mass would do, because light has a universally constant velocity. Why is that exception?
45 views

### Is the structure of crystalized white dwarf related to nuclear pasta?

There is news of an analysis of a large number of nearby white dwarfs revealing a "pile-up" at a certain point in their cooling which has been predicted to happen due to a phase change where nuclear ...
52 views

### Why is the opening in the Anglo-Australian Telescope's dome so small?

Many older or "classic" telescope domes have a horizon-to-zenith opening in the dome, and this helps speed up the thermal equilibration between the inside and outside air, decreasing turbulence and ...
32 views

### Delete key does not always work in IRAF's xgterm on Mac

Sometimes it does not let me delete text in an xgterm terminal and outputs ^H instead. Example: Run IRAF: xgterm -e cl It opens the xgterm, there I type: <...
48 views

### What is the dimensions of the smallest object detectable by an optical fiber from a specific distance?

Optical fibers are well-known to observe astronomical objects, say, galaxies, to generate massive spectroscopic surveys. The galaxies are often very far from the optical fibers of a telescope. However,...
119 views

### Why do nebulae turn into accretion disks but planets do not?

What are the factors that prevent planets from also turning into disks, like the stellar dust in a nebula does? The Earth is not a perfect sphere, but rather it's squished at the poles and it bulges ...