# Tag Info

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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 incomplete [see below]). So here's the answer: As you mention, when light enters our atmosphere, it goes through several parcels of gas with varying density, ...

63

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 predominantly blue and similar. So the color we might expect to see from the Moon is going to be adjusted by the color properties of the Moon's surface. As it ...

42

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 as sunlight. Any phenomenology (which appears disputed) as per the claim in the question is purely down to the nuances of our colour perception. Figure 8: ...

28

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 1/2 of 1 degree of the sky, the entire sky being 180 degrees, give or take, so the full moon fills less than 1 part in 100,000 of the night sky, so there ...

25

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 little atmospheric influence as possible) the landscape around us appears blueish, because of the Purkinje effect: at low illumination levels our red color ...

22

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 polluted sites, this can easily reach one magnitude of extinction, which means that 60 per cent of the light is scattered. These numbers are per airmass - which ...

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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 advantage of the transparency at these wavelengths. If we had evolved in an atmosphere with a very different mix of gases. One in which visible light was ...

19

The easiest way to determine the magnitude of a given star is probably to use the Pogson relation. The idea is to determine the magnitude of a star knowing the magnitude of a reference star; it is thus quite easy, using a well-known reference as Vega or Sirius. The Pogson relation is given by: $$m_1-m_2=-2.5\ log\ \left({\frac{E_1}{E_2}}\right)$$ where $... 13 It does actually, but the human eye can't see it. But long exposure photography can see it easily. Or this photo, taken about three hours after sunset and lit by a nearly-full moon. 13 The Sun doesn't substantially impact radio observations during the day, because radio telescopes operate at long wavelengths. In general, light at longer wavelengths scatters less than light at shorter wavelengths, and so visible light from the Sun scatters much more than radio waves from the Sun.$^{\dagger}$The former effectively fills the daytime sky, ... 12 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 Earth's atmosphere refracts light. One notable effect is that objects near horizon appear higher than they should be. Therefore, the Sun (or any other object) ... 9 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 plenty of sun in Mars, but no rain, and only very rare clouds. It rains on Titan: methane rain. Methane has a lower refractive index than water (1.27 instead of 1.... 9 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). He asserted that the space above the mercury in his tube was a vacuum, a totally anti-Aristotlean concept at that time. To test this he enlisted the help of ... 8 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, very) thin atmospheres, and these are obviously "clear". If you regard that argument as tricksy, then we can turn to Mars. Yes Mars has occasional dust storms. In ... 8 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 will shrink a few degrees, close to the size of that on Earth. Source for methane: https://refractiveindex.info/?shelf=organic&book=methane&page=... 8 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 reason that a red dwarf is red, is not just that it is cool, but that there are great chunks of the spectrum that are absorbed by molecules in the photosphere ... 8 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", including both classical and literary claims (e.g., in stories by Dickens and Kipling) and actual experiments. It appears that the Aristotle reference (&... 7 It is possible but unlikely. Here is a really good 'Science 2.0' article about the possibility (http://www.science20.com/robert_inventor/could_you_see_moon_city_lights_or_a_greenhouse_from_earth_just_for_fun-157480). Essentially, you likely wouldn't see the light on Moon settlements because there would need to have many thousands of bright lights and windows-... 6 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 Earth is composed of parts of differing density...this property produces the effects of waving and dancing of Bodies; and of the twinkling of the Stars 6 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 planets and Luna are close enough to have a resolvable diameter while being visible, which means that their light is not coherent like a point source's might be. ... 6 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 were obtained), by Marco Ciocca and Jing Wang, they explain: Page 365: "The rods are effectively colour blind. Scotopic vision has a higher sensitivity to ... 6 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 light and shadow. What you are seeing here is essentially the same as the twinkle that you see from stars. 6 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}$as a measure for turbulence: density$\rho\$ drops due to the reduced pressure (about 1/100 earth pressure), additionally the gravity is smaller than on earth ...

6

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. Objectively, moonlight is not blue. In fact, it is even more yellow than sunlight! (comparing the same elevation, because obviously the true color can be distorted ...

5

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 that the scatterers are much smaller than the wavelength of light (water droplets etc). Mie scattering is roughly wavelength independent and much stronger in ...

5

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 depending on the Sun position. Other readers can refer to https://en.m.wikipedia.org/wiki/Rayleigh_scattering. We are used to our atmosphere and as such often ...

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I would argue the famous Michelson-Morley experiment. Luminiferous Aether A bit of background first before getting into the experiment itself. It is quite easy to surmise, via Newton's laws of motion, that Earth should be in a vacuum, otherwise the constant drag of traveling through some medium must eventually cause us to crash into the Sun. Despite this ...

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The guide star laser is used to adapt the optics at a specific time and location, for specific atmospheric conditions. It is not, as your question implies, used to calibrate the optics for long-term use. Therefor, if order to calibrate the satellite with a laser fired from Earth, the reconnaissance target would have to provide the laser. This is useless for ...

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It depends on the composition of the atmosphere. In a helium (or other light gas) atmosphere, your voice would have a higher pitch. If the gasses are heavier, your voice drops. The density is also a factor: on Mars, sounds can't be as loud as on Earth. Sound is transmitted as pressure differences, and the largest pressure difference you can get is that ...

4

Depending on your eyesight, the faintest stars you can see in a perfect environment have an apparent magnitude (brightness) of 6-6.5 (though some people have managed to see magnitude-7). According to this site, that translates into about 10,000 stars. As for how it would look, I have seen the sky from the stratosphere (about 3 miles up, in a plane, where ...

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