The Sun is an almost perfectly symmetric yellow dwarf star [spectral class G2V] which is at the center of our Solar System.
Questions tagged [sun]
806 questions
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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 the result that the position of the light source…
user56903
107
votes
8 answers
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 like a nuclear bomb will complete all the reaction…
user.3898215
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84
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3 answers
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 Rayleigh scattering goes like $\omega^4$, why is the…
Warrick
- 9,870
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3 answers
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 a still image? Can one tell them apart?
AlonMln
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65
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5 answers
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 physicist, but this sounds to me like a huge leap.
I would…
janusz
- 1,013
65
votes
3 answers
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 and narrow diameters would be much less than the…
user81619
63
votes
4 answers
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. This holds for indoor scenes (like my hall) and for…
Kartick Vaddadi
- 807
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8 answers
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 this? For example, solar winds?
Mubin Icyer
- 679
55
votes
5 answers
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 energetically.
My understanding is that field lines are just a visualization…
Robert
- 1,111
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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?
Lior
- 3,490
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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 about being able to see things clearly, but just…
Jeff
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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.)
Phira
- 2,102
45
votes
4 answers
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 answers: one saying "nothing much happens" and…
Allure
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5 answers
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 (or partial eclipse) is happening?
What, then, is…
JYelton
- 1,339
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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 question is, so why is the Sun's core so hot (15.7…
Peter4075
- 3,109