Questions tagged [sun]
The Sun is an almost perfectly symmetric yellow dwarf star [spectral class G2V] which is at the center of our Solar System.
755
questions
167
votes
2
answers
38k
views
Why do sunbeams diverge even though the sun is much more than a few kilometers away?
Consider this picture of sun beams streaming onto the valley through the clouds.
Given that the valley is only (at a guess) 3km wide, with simple trigonometry and the angles of the beams, this gives ...
user56903
107
votes
8
answers
21k
views
Why does the Sun's (or other stars') nuclear reaction not use up all its "fuel" immediately?
The temperature and pressure everywhere inside the Sun reach the critical point to start nuclear reactions - there is no reason for it to take such a long time to complete the reaction process.
Just ...
- 1,196
78
votes
3
answers
60k
views
Why is the sky not purple?
I realise the question of why this sky is blue is considered reasonably often here, one way or another. You can take that knowledge as given. What I'm wondering is, given that the spectrum of ...
- 9,435
65
votes
3
answers
8k
views
Do sunrises and sunsets look the same in a still image?
A question that popped into my head: if I see a picture of the sun close to the horizon, in an unknown place, can I know if it was taken at sunset or sunrise?
Do sunrises and sunsets look the same in ...
- 633
62
votes
3
answers
12k
views
Why is the Sun almost perfectly spherical?
Relatively recent measurements indicate that the Sun is nearly the roundest object ever measured. If scaled to the size of a beach ball, it would be so round that the difference between the widest ...
user81619
62
votes
4
answers
31k
views
Why does moonlight have a lower color temperature?
Moonlight has a color temperature of 4100K, while sunlight has a higher color temperature of more than 5000K.
But objects illuminated by moonlight don't look yellower to the eye. They look bluer. ...
- 799
59
votes
8
answers
13k
views
Is it possible to send all nuclear waste on Earth to the Sun?
If we neglect the danger of unsuccessful lift-off of the rocket and the cost, would it be physically possible to send all nuclear waste on Earth to the Sun?
Will there be an obstacle that prevents ...
- 679
56
votes
5
answers
12k
views
The Sun is giving us a low entropy, not energy
While I was watching a popular science lecture on YouTube, I came across this sentence
"Sun is giving us a low entropy, not energy"
which was said by Prof. Krzysztof Meissner.
I am not a ...
- 915
55
votes
5
answers
7k
views
What is happening when magnetic field lines snap or break?
In discussions of sun spots and auroras on Earth, magnetic field lines are often described as "snapping" or "breaking", with the result of releasing charged particles very ...
- 1,101
55
votes
1
answer
4k
views
What causes the Sun to appear to be in front of a building in this picture?
I took this photograph a few days ago, during sunrise, using my smartphone camera and digital zoom:
It seems that the sun is in front of the building. How is this explained?
- 3,219
48
votes
3
answers
26k
views
Why aren't 100% UV blocked sunglasses safe to view an eclipse with?
I am not planning on staring into the sun during an eclipse or any other time.
I have been reading about how no variety of regular sunglasses are safe enough to view the eclipse with. I'm not talking ...
- 453
47
votes
6
answers
22k
views
Can the apparent equal size of sun and moon be explained or is this a coincidence?
Is there a possible explanation for the apparent equal size of sun and moon or is this a coincidence?
(An explanation can involve something like tide-lock effects or the anthropic principle.)
- 2,052
44
votes
4
answers
14k
views
What would happen if Jupiter collided with the Sun?
This question is inspired by a similar one asked on Quora. Let's say a wizard magicked Jupiter into the Sun, with or without high velocity. What happens?
The Quora question has two completely opposed ...
- 18.7k
42
votes
4
answers
6k
views
How far out from the Sun is visible light still sufficient to read a book?
Recent pictures from the New Horizons spacecraft, shown below, seem to indicate that, at Pluto's distance, we are entering a twilight zone, with a distinct lack of colors, although that could be due ...
user81619
42
votes
5
answers
29k
views
Why is a new moon not the same as a solar eclipse?
Forgive the elementary nature of this question:
Because a new moon occurs when the moon is positioned between the earth and sun, doesn't this also mean that somewhere on the Earth, a solar eclipse (...
- 1,325
41
votes
7
answers
8k
views
Why does the full Moon appear?
I know that the full Moon appears when Sun, Moon and Earth are in a straight line, but if we consider that they are in straight line, why is the Moon illuminated?
I mean to say that Earth should ...
- 592
41
votes
2
answers
17k
views
Why is the sun brighter in Australia compared to parts of Asia?
Background:
I've lived in Philippines for several years, and visited other parts of Asia occasionally (Singapore, Indonesia, Hongkong).
I just moved to Western Australia a few months ago and I ...
- 863
40
votes
3
answers
9k
views
Why wouldn't the part of the Earth facing the Sun a half year before be facing away from it now at noon?
The Earth takes 24 hours to spin around its own axis and 365 days to spin around the Sun. So in approximately half a year the Earth will have spun around its axis 182.5 times.
Now take a look at the ...
- 555
40
votes
3
answers
11k
views
Sun's power density compared to a compost heap
According to Wikipedia the Sun's "power density" is "approximately 276.5 $W/m^3$, a value that more nearly approximates that of reptile metabolism or a compost pile than of a thermonuclear bomb." My ...
- 2,999
39
votes
4
answers
5k
views
Does the sun rotate?
As implied from the question, does the sun rotate? If so, do other stars not including the sun also rotate? Would there be any consequences if the sun and other stars didn't rotate? Me and my friends ...
- 1,638
36
votes
6
answers
12k
views
If the moon had a mirror surface, would the earth be equally illuminated as by the sun during full moon, or would it require a different mirror shape?
Suppose the apparent diameters of the sun and the moon are exactly the same (which in fact very close to the real situation). If the moon had a perfect mirror surface, would the reflected visible ...
35
votes
7
answers
33k
views
Is the light from the Sun the same as the light from a bulb?
I'm arguing with a friend of mine on whether the light emitted from the sun is of the same type of that emitted by a bulb. Her insistent ignorance is laughable, unless I'm wrong...
She's talking ...
- 1,809
34
votes
3
answers
6k
views
Do rainbows show spectral lines from the sun?
I'm aware of a similar question being asked in Do rainbow shows spectral lines?:
The response to this question is that the body producing the light is not the water droplet that merely diffracts it ...
- 781
32
votes
3
answers
3k
views
Can the Sun capture dark matter gravitationally?
I think my title sums it up. Given that we think the dark matter is pseudo-spherically distributed and orbits in the Galactic potential with everything else, then I assume that its speed with respect ...
- 122k
31
votes
5
answers
10k
views
Can the sun cast a shadow?
The sun's light can cast the shadow of another object, but does it ever cast its own shadow?
- 593
30
votes
5
answers
14k
views
Why is the Sun called an "average star"?
This is a statement (presumably in mass, longevity, energy output) many people that I've met have heard in school, and it is known in pop culture. However, according to Wikipedia, about 75% of the ...
- 2,839
30
votes
5
answers
17k
views
How do those T-shirts that change color in the sun work?
When I was a kid, I asked my dad about them and he said (not in so many words) that it was because sunlight and artificial light have different spectrums and they picked colors that reflect only the ...
- 1,353
29
votes
3
answers
3k
views
Parker Solar Probe passing extremely close to the Sun; what relativistic effects will it experience and how large will they be?
note: This is a question about relativistic effects. I've included some detail about the spacecraft and its orbit for background, but the question is about relativistic effects and their observability....
- 6,638
27
votes
1
answer
3k
views
As the sun expands, will its Roche limit also expand?
So my friend and I had a debate. He stated that we don't have to worry about the sun consuming the Earth ─ we'll already be broken apart by then. He states that as the sun expands, its Roche limit ...
- 1,066
27
votes
2
answers
10k
views
How long until we fall into the Sun?
As a planet moves through the solar system, a bow shock is formed as the solar wind is decelerated by the magnetic field of the planet. Presumably the creation of this shock wave would cause drag on ...
- 16.3k
27
votes
1
answer
512
views
The transit of Venus and solar neutrino rates
The following question was posed at the end of Maury Goodman's June 2012 long-baseline neutrino newsletter.
During the Venus transit of the sun, were more solar neutrinos
absorbed in Venus, or ...
26
votes
5
answers
7k
views
Why isn't the sunset/sunrise rainbow-colored
When the sun is rising/setting, it goes through a phase where the light is bending from the atmosphere. I believe this image will explain much better than I ever could.
Now, if light goes through a ...
- 1,063
25
votes
9
answers
5k
views
Are the physical structures in our sun of comparable complexity to those in the human brain? [closed]
The writings of Rupert Sheldrake tend to provoke strong emotions, be they ridicule, curiosity, outrage, sympathy, disgust, or otherwise. While Physics SE is not an appropriate forum in which either to ...
- 361
25
votes
4
answers
6k
views
Where will the Goldilocks zone be when the Sun becomes a red giant?
In about 5 billion years, when our Sun expands into a red giant making our planet uninhabitable, where will the new Goldilocks zone be? Could life form on a new planet in the Goldilocks zone? ...
- 251
25
votes
3
answers
4k
views
What causes our Sun to oscillate around its mean Galactic orbit?
According to this answer on Astronomy.SE,
The Sun executes oscillations around its mean orbit in the Galaxy, periodically crossing the Galactic plane. I borrowed this illustration (not to scale!) ...
- 4,902
25
votes
2
answers
4k
views
How fast is the Earth-Sun distance changing
This is inspired by Evidence that the Solar System is expanding like the Universe?, which referenced an article by G. A. Krasinsky and V. A. Brumberg, "Secular Increase of Astronomical Unit from ...
user10851
23
votes
2
answers
16k
views
Why does sunset over a body of water cause a path of light stretching towards the horizon?
Have you ever notice the sunset's image in the sea? It's like long light path to the end of the horizon! I've attached a sample of this:
How can we explain this? I know that it can happen even in ...
- 327
22
votes
2
answers
3k
views
Are there Higgs bosons in the Sun?
To find the Higgs boson, we had to build the biggest machine mankind has ever built: the LHC with a collision energy of up to 14 TeV. Inside the sun there is a huge pressure and temperature, but is ...
- 1,458
22
votes
3
answers
15k
views
Looking at the sun through heavy fog, do invisible wavelengths get through?
This morning it was particularly foggy and my son was excitedly looking at the sun through the fog, since of course he normally can't look directly at it and see the disk. I told him to stop looking ...
- 323
21
votes
4
answers
13k
views
How come the Sun's gravity can hold distant planets in orbit, but cannot rip humans off Earth?
The sun is strong enough to keep gas giants close, but why not people?
- 414
21
votes
7
answers
4k
views
Finding how much time it takes for a complete Earth revolution around the Sun
Long story short, my brother made a joke about how stupid it is to celebrate the Earth making one "trip" around the Sun: New Year's Eve.
So I got curious and was wondering: how could the first ...
- 320
21
votes
7
answers
5k
views
What can we deduce by the fact that mirrors cannot get a ray hotter than Sun's surface?
I think it is quite counter-intuitive that some lenses or mirrors focusing sunlight to a single spot cannot produce a temperature higher than Sun's Surface.
What could a scientist deduce from that ...
- 729
21
votes
3
answers
12k
views
Why do materials change color when exposed to the sun for a long time?
I have a lot of solid objects that were exposed to the sun for many years and "obviously" they changed their color. I write obviously because I know it empirically and from other people, but what is ...
- 544
21
votes
4
answers
42k
views
How is Earth protected from the gamma rays generated by the Sun?
The Sun is generating energy by nuclear fusion. This nuclear fusion will emit energy in the form of gamma rays.
Normally, the earth's ozone layer filters the ultraviolet radiation while the earth's ...
- 694
20
votes
2
answers
4k
views
Why does the Sun appear white through clouds?
Why does the Sun appear white through clouds? It seems there should not be any absorption of, say, the reddish component, as this would not produce a white colour. So what is going on? Am I right that ...
- 1,785
20
votes
3
answers
602
views
What happens to the electron companions of cosmic ray protons?
If primary cosmic rays are made mostly of protons, where are the electrons lost, and does this mean that the Earth is positively charged?
Does the sun eject protons and electrons in equal number?
- 1,293
19
votes
3
answers
5k
views
How can a full moon be seen south of an observer's location?
I know this seems like a simple question, but I'm trying to debate with a flat earth theorist. I asked him to explain why can the ISS visibly be seen orbiting the Earth with the naked eye, and he put ...
- 215
19
votes
3
answers
7k
views
Do solar panels act as an electrical load on the sun?
We know that the sun uses nuclear fusion to generate sunlight and heat energy. If we are using solar panels to harvest solar energy, aren't we putting some electrical load(resistance) on the sun? If ...
- 307
19
votes
2
answers
5k
views
Sun light takes 1,000/30,000/100,000/170,000/1,000,000 years bouncing around inside to then reach the Earth
When light (photon particle) is generated inside the Sun, it takes a long time to bounce around inside to later escape and travel outwards.
Neutrinos escape immediately.
The numbers for the years ...
- 383
18
votes
1
answer
3k
views
Why is the Sun made of light elements only?
Since the entire solar system inherits its heavy elements from supernovae unrelated to our star, I fail to understand why, while capturing most of said system's matter, the sun only contain light ...
- 3,168