65 votes
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Why doesn't the moon twinkle?

The first handful of hits on Google actually return incomplete and even wrong answers (e.g. "Because the Moon is much brighter" which is plain wrong, and "Because the Moon is closer" which is ...
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63 votes

Why is moon light not the same color as sunlight?

The light from the moon is light being reflected from the sun. This is at least one reason you should not expect the Moon to have the same color. Sunlight hitting an e.g. blue object would appear ...
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42 votes

Why is moon light not the same color as sunlight?

Reflected moonlight is actually slightly reddened compared with the incident solar spectrum (Ciocca & Wang 2013). That same light is then transmitted through out atmosphere in exactly the same way ...
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34 votes
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Why are fewer stars seen next to the horizon?

When you look towards the horizon you are looking through a much greater thickness of air. The air does absorb some light. Dense air near surface absorbs more, and if you look towards the horizon ...
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29 votes

What it the outer part of the sun, that we see with our eyes, called?

I think you're talking about the effect of a "fluffy glowing ball" around the solar disk, shown on the right in this photo: This is called solar aureole, and it's caused by the aerosols in ...
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28 votes
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Why can't moon light (reflected sun light) turn the sky blue?

The simple answer is that it does, but it's not bright enough to be visible to the naked eye. Earth's atmosphere scatters the moon light just like sunlight. The full moon (like the sun) fills about ...
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25 votes

Why is moon light not the same color as sunlight?

Surprisingly, the moonlight is actually slightly warmer color than sunlight, as the moon reflectance is higher for longer wavelengths. Yet, on clear nights, with the full moon high in the sky (as ...
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22 votes
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How much clearer are stars in earths orbit?

It varies. The best astronomical sites have a visual band extinction of 0.1 mag, which means that only $\sim 10$ per cent of light is absorbed/scattered in the atmosphere. In dusty, smoggy or ...
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21 votes
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Is Earth unique in its fairly clear atmosphere?

Our atmosphere is only transparent to visible light, In most other wavelengths, some or all of the light is absorbed Image from Wikipedia, adapted from image by NASA Our eyes have evolved to take ...
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15 votes

What it the outer part of the sun, that we see with our eyes, called?

What it the outer part of the sun, that we see with our eyes, called? I am not sure there is a single word for this, since the effect is a little complicated. We might call it "the glare of the ...
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13 votes

Why can't moon light (reflected sun light) turn the sky blue?

It does actually, but the human eye can't see it. But long exposure photography can see it easily. Or this photo, taken about three hours after sunset and lit by a nearly-full moon.
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13 votes

Do radio telescopes see other stars better at night?

The Sun doesn't substantially impact radio observations during the day, because radio telescopes operate at long wavelengths. In general, light at longer wavelengths scatters less than light at ...
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12 votes
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Does the earth's atmosphere act as a spherical lens and refract light from space?

If so by how much does it "spoil" the view of stars and galaxies etc. There are several very different issues related to your question. Let's tackle them one by one. Atmospheric refraction Yes, the ...
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10 votes

What was the first astronomical measurement which demonstrated that "the Earth is surrounded by vacuum"?

Torricelli, the inventor of the Mercury Barometer (~1644) argued that the height of the column of mercury was governed by atmospheric pressure (the "weight of the atmosphere" as he would have put it). ...
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9 votes

How would rainbows appear on other planets?

Rainbows occur when sunlight shines through rain. This is rare in the solar system. Rain (of sulphuric acid) might be common enough under Venus's clouds, but there is no sun. Conversely, there is ...
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9 votes
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How would rainbows appear on other planets?

note 1: I've verified @JamesK's answer's index of refraction of 1.27 (since no source was cited), at least for a temperature of 111K, yay! On a colder day, say 90K, the index goes up and the rainbow ...
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8 votes

Is Earth unique in its fairly clear atmosphere?

No, the clarity of the Earth's atmosphere cannot be considered unique. We don't have to speculate about exoplanets. You could argue the answer is no, because both the Moon and Mercury have (very, ...
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8 votes
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Can you see city lights on the Moon from Earth?

It is possible but unlikely. Here is a really good 'Science 2.0' article about the possibility (http://www.science20.com/robert_inventor/...
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8 votes
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Would a red dwarf star resemble our own Sun at sunset to an observer on a nearby planet?

Your question may ulitmately be about the physiology of the eye, which is off-topic here. The spectrum of the Sun seen low on the horizon is quite different to the spectrum of an M-type red dwarf. The ...
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8 votes
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Can an average person see stars from the bottom of a well or through cardboard tubes? Definitive answer required!

This article (Hughes 1983, "On Seeing Stars (especially up chimneys") from the Quarterly Journal of the Royal Astronomical Society seems like a pretty good account of the "phenomenon&...
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7 votes

Why doesn't the moon twinkle?

The wikipedia page on twinkling, aka scintillation, covers it quite succinctly; it boils down to the fact that distant stars are sufficiently distant to be a point source of coherent light. Solar ...
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  • 171
7 votes

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

The blue tint is an illusion caused by the wavelength sensitivity shift when switching from rods to cones as the light intensity decreases below certain level. It is called the Purkinje effect. ...
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  • 475
7 votes

What it the outer part of the sun, that we see with our eyes, called?

None of the other responses seem to answer the question "What is the name of the thing the solar filter is eliminating?" In fact, the solar filter doesn't eliminate anything. It just makes ...
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6 votes
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Oldest Reference to Astronomical Seeing

Robert Hooke's Micrographia from 1664 has a detailed discussion of "seeing" The table [of contents], which is at the end of the book, explains that pages 230-232 discuss: that the Air near the ...
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6 votes

Why is moon light not the same color as sunlight?

I agree with Jack's comment, it's partly misconception and party due to the way rods and cones work. In "By the light of the silvery Moon: fact and fiction" (from where the illustration and quotes ...
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6 votes
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What is causing this strange shimmering pattern of light during a total solar eclipse?

These are called shadow bands. As the sunlight is reduced to a very narrow strip, in the last few moments before totality, turbulence and refraction in the atmosphere will cause shimmering bands of ...
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6 votes
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How would astronomical seeing on Mars differ from that on Earth?

As far as I know, "seeing" (or rather the effects influencing optical wave propagation) is caused by turbulence in the atmosphere. Using the Reynolds number Number $ Re = \dfrac{\rho L v}{\mu}$ as a ...
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5 votes

Why can't moon light (reflected sun light) turn the sky blue?

userLTK nailed it, but I'll add the answer to the last part of your question. Close to the Moon we often do see scattered light. This is a phenomenon called Mie scattering where it cannot be assumed ...
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5 votes
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How large does refraction become in radioastronomy?

The refractive deviations in position are very similar for both radio and optical astronomy, until you consider very low frequency radio waves ($<200$ MHz) when the effect becomes rapidly larger. ...
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5 votes
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Do the gases in the Earth's atmosphere affect the color of a lunar eclipse?

From the way you have formulated your question, it seems to me that you are aware of the light diffusive process named Rayleigh Scattering and why it explains the various tints and colours of the sky ...
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