The Sun is an almost perfectly symmetric yellow dwarf star [spectral class G2V] which is at the center of our Solar System.

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How is SUN rotating? [on hold]

Is Sun rotating anti clockwise similar to planet Venus or is it continuously changing it rotation ?
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3answers
277 views

Why is there less UV light on earth in winter

So I have often read that, at least in e.g. northern Europe, in the colder seasons, there is not enough UV (-B) light arriving from the sun, so many people have not enough vitamin-D from that. At ...
4
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2answers
47 views

Do radio waves from the Sun reach Earth?

Do radio waves from the Sun come into contact with Earth? If so, do they penetrate the atmosphere or are they reflected, absorbed, or scattered?
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0answers
52 views

How to correctly calculate the colour of the sky?

It is well-known that the sky is blue due to Rayleigh-scattering. What bothers me though is the question how to actually calculate the spectrum of the scattered sunlight. Yes, use one of the ...
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1answer
65 views

is the sun going to make an electromagnetic pulse in the next 50 years?

EMP is very damaging and can cause blackouts and other bad results specially on electronic devices , so i heard that our sun is going to make an electromagnetic pulse during the next 50 years ..is ...
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1answer
28 views

What changes in the moon light (spectrum, intensity, etc…) after the spring equinox? [closed]

There must be a correlation between the earth moon system and the sun during spring, just after the spring equinox.
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1answer
63 views

How Long Did It Take For The Sun To Form?

I realise this may be a difficult question to answer because, AFAIK, we don't have an accurate estimate of the size of the protostellar cloud, or whether our sun formed from a subsection of a much ...
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1answer
55 views

What is the angular divergence of sun-rays? [on hold]

I just want to find a number and I could not. Does anyone has it or can calculate it easily? Just in geometric optics, without diffraction, atmospheric effects and etc. Update: I think for me will be ...
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0answers
60 views

How do you calculate the heat build-up inside a building or container as a result of the sun?

I need to calculate how much heat builds up in a closed environment eg a building or a Chromadek container. One of the factors I need to take into account is the sun. I know there are various ...
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0answers
39 views

What is the difference between the light coming from Moon and the Sun? [duplicate]

The moon surface is reflective so, we should have the same light spectrum. And yet there is a difference in the quality of these two lights.
3
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1answer
73 views

Gravitational force between Earth and Sun is decreasing

According to one of the most famous equations in physics, i.e. $E=mc^2$, the mass of the Sun is decreasing as it emits energy. So there must be some kind of disturbance in planetary orbits, and if ...
2
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3answers
104 views

Flat-Earthers Claim: Crepuscular Rays $\implies$ the Sun is Close [closed]

I have been trying for a couple of days to come up with a nice illustration of why crepuscular rays are not suggesting that the sun must be close to the earth, as flat-earthers claim. I made the ...
5
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0answers
58 views

Path of photon from Sun to earth unaltered? [duplicate]

I got into a discussion regarding the light from the Sun that reaches the Earth and whether it maintains the same path from the moment it was emitted to the point it is processed by our eyes. My ...
52
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4answers
5k views

Why does the sun have to be nearly fully covered to notice any darkening in an eclipse?

I was looking at eclipse footage and I noticed that it doesn't get any noticeably darker until the very end when it suddenly all the light is gone. As the moon blocks out the Sun, I would expect that ...
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5answers
4k 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 ...
3
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3answers
49 views

Can we observe solar p-p fusion reaction somehow on Earth?

What are the properties of proton+proton fusion reaction $p + p → 2H + e^+ + ν_e + 0.42 MeV$ making it hard to replicate on Earth? If we aim beam of protons to a can of water, won't we observe ...
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0answers
16 views

Generic Rayleigh effect experiment - nothing happens for water

On youtube, a bunch of Rayleigh scattering experiments (e.g this one are set up with some compound being added to water in order to invoke the effect. Why is there no Rayleigh effect for "pure" water?...
3
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2answers
54 views

Possible Safe Areas In a Solar Flare

Which part of the earth would be the safest in case of the major solar flare? Will it be near equator or something like that?
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5answers
4k 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 ...
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2answers
50 views

Does the solar wind correspond to a net electrical current?

The solar wind is a stream of ions emitted from the sun. Are there more positive than negative charges released? That is, is there any imbalance in the charge emitted from the sun in the solar wind?
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1answer
87 views

As planets orbit around the Sun, does the force of gravity due to the Sun remain constant?

I know that the force of gravity is: $$F = GMm/R^2$$ Where $G$ is gravitational constant, $M$ is mass of sun, $m$ is mass of the orbiting planet and $R$ is the distance between the center of their ...
1
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1answer
67 views

The sun glows bright white, but what color of light does it reflect?

Basically if you take a gray iron bar, and heat it red hot, it would still reflect a dullish white light, even though all you could see is the red light it emits as radiation. In fact if you watch ...
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1answer
64 views

Gravity Sun Earth Moon [duplicate]

The gravitational pull the Sun has on the Moon is roughly two times greater than the pull the Earth has on the Moon. If this is the case, why does the Sun's gravity not pull the Moon away from the ...
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2answers
112 views

Why doesn't sunlight flicker like candle or flame torch?

Why sunlight appears constant and stable like sun is a bulb? If the surface of the sun and processes going in it are not completely uniform why don't we notice any flickering or non- uniformity in ...
4
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1answer
45 views

Measuring the size of the core of the sun with multiple neutrino detectors

Back in 1998, researchers at the Super-Kamiokande neutrino detector released this image: of the sun using their neutrino detector using approximately 500 days of data. This picture covered 90x90 ...
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3answers
84 views

Why doesn't the earth collide with the sun in 64 years?

According to another answer on this site, the time it takes for two bodies in space to collide can be computed with the following formula: $$\frac{\pi}{2\sqrt{2}}\frac{r_0^{3/2}}{\sqrt{G(M+m)}}$$ ...
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3answers
55 views

Does visible light heat things up?

During a sunny day the walls of my house warm up (no surprise). My question: how much of this warming up (if any) comes from visible light? I associate infrared with thermal energy. If my house was ...
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2answers
34 views

Diminishing solar temperature and its effects on earth

This is a hypothetical question; considering both the earth and the sun as black bodies. If the temperature of the sun decreased N times, what would be the effect on the radiation intensity received ...
4
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1answer
75 views

How far has Earth moved from its birth orbit?

It says earth is almost as old as 1/3 of the universe's age which would mean 4.5 billion years . So how far has earth moved towards or away from the sun in these 4.5 billion years? Now perfect ...
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3answers
124 views

Create a laser from sun light

I have read on wikipedia the basic theory behind laser. A photon passes through an excited electron which then produces the exact same photon. Light is bounced off mirrors to create more photons. Is ...
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0answers
96 views

How to derive equation for time it takes photons to diffuse through the Sun

I am wanting to use the Rosseland radiative heat flux equation to find the time it takes for photons to diffuse through the sun. The answer I am wanting to derive is: $$\tau_D~\frac{\rho \bar C_p R^...
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0answers
23 views

Color Temperature Variation of Sunlight

I want to know what is the Variation of the color temperature in Kelvin of Sunlight as viewed from the earth from Sunrise to Brightday to Noon to Sunset. Will there be any change in the color ...
0
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0answers
18 views

Experiments on the melting of snow?

When snow melts there are three main variables: the temperature of the air, the altitude of the sun, and the distance of the sun from the earth (which changes because the earth moves in an ellipse ...
3
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1answer
116 views

What causes the differential rotation of the Sun?

I have read the explanation in Wikipedia, but the problem is that because I'm a beginner in physics, I don't quite understand what more than half of the words mean! Here is the explanation from ...
4
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1answer
56 views

How much of Ultraviolet is cut out when Sun moves to the Horizon?

EDIT: Original question was whether or not we need to wear sunglasses when Sun is at the horizon. But it was confusing to many users whether it is on-topic or not. So the details are adjusted. From ...
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4answers
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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. ...
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1answer
52 views

Spacetime Mercury vs Earth

What is the time dilatation of the planet Mercury compared to Earth? Can a person survive on the dark side of Mercury in the In the L2 position to Mercury and the Sun?
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1answer
40 views

Lead shielding very close to the Sun

I understand that eventually lead would melt when it nears the sun. In a liquid state how effective would lead be in blocking radiation? Would it still be as effective as solid state of lead? What ...
1
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1answer
61 views

Does solar eclipse have impact over increase of earth's temperature?

Does a solar eclipse have an impact on global temperature? Wired theory : When I jump, does the Earth recoil? Yes, the Earth has to move in some way for momentum to be conserved. However, since ...
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0answers
26 views

Energy potential of a cold sink inside the sun

An answer in this question discusses using a fusion engine in a theoretical spaceship within a star. http://worldbuilding.stackexchange.com/questions/37589/what-are-the-consequences-of-literal-...
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2answers
61 views

Can solar flares affect gravity?

Can a large eruption of solar flares on our sun change the effects of its gravity ever so slightly, and is it possible to measure these changes with the equipment we have today.
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1answer
250 views

Why is my shadow deformed and not the shadow of the ceiling? [duplicate]

Look at these two photos of my shadow from sunlight. Case 1: My shadow is separated from the shadow of the ceiling and my head is round. Case 2: But when I walk a little more and the shadow of my ...
5
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1answer
83 views

Strength of moonlight

So I read this xkcd, and thought it was kind of cool. However, I showed it to my engineer father and physics undergrad brother and neither seem to find the explanation very convincing (though they ...
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1answer
79 views

What do sun spots look like under the surface of the Sun? [closed]

Do sun spots float like oil, float around like a lava lamp, is it more like the tip of an ice burg or what?
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0answers
30 views

How to calculate apex angle of sun shining on the Earth

I'm trying to compare the brightness of various LEDs to the average brightness of natural daylight. LEDs are rated in terms of candelas whereas the Sun is measured in terms of lumens, so I need to ...
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1answer
97 views

Is climate change caused by humans? [closed]

Some people argue it is not because it is caused by solar cycles (sometimes the sun brights more than others thus increasing the Earth's temperature) and that the energy that $CO_2$ traps isn't enough ...
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1answer
60 views

How the sun can burn that long? [duplicate]

I suddenly became curious that why the sun doesn't burn out at once? What makes the sun burn gradually?
3
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2answers
60 views

Why is there ice at the Earth's poles? [duplicate]

I beg your pardon for such a silly question, but I've never really understood the explanation they gave in the Geography textbooks. If the slanting Sun's rays due to the Earth's axial tilt can cause ...
1
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2answers
75 views

Why are Lunar Eclipse more common than Solar Eclipse?

Why are Lunar Eclipse more common than Solar Eclipse? Chapter from Light My thoughts; Eclipse can only occur at new moon and moon orbit is inclined at an angle of about 5 degrees to the earth's ...
2
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3answers
89 views

Measuring Rotation of Sun

If the sun had a uniform surface (i.e., if there were no sunspots to look at), is there a practical way to measure its rotation? In other words, if some external force flipped the sun's spin suddenly,...