# Does any light reach the Sun from Earth? How far does it make it? **URL:** \ **Category:** Factual Questions\ **Created:** [August 27, 2004, 5:39pm UTC](https://boards.straightdope.com/t/does-any-light-reach-the-sun-from-earth-how-far-does-it-make-it/261821 "2004-08-27T17:39:35Z")\ **Posts on this page:** 18\ **Page:** 1
**Author:** ![alterego](https://avatars.discourse-cdn.com/v4/letter/a/6bbea6/32.png) [@alterego](https://boards.straightdope.com/u/alterego)\ **Post date:** [August 27, 2004, 5:39pm UTC](https://boards.straightdope.com/t/does-any-light-reach-the-sun-from-earth-how-far-does-it-make-it/261821/1 "2004-08-27T17:39:35Z")
I know it takes something like 8 seconds for light to reach the Earth from Sun. I was thinking about from the Earth to the Sun though, and I don’t think it would make it all the way (overpowered). So, for the sake of enjoyment, let’s pretend we had a space shuttle that was capable of sustaining temperatures from the sun at say, 100km away from it. It also had a window, which was pointing away from the Sun and towards Earth. How far away from the Sun, or how close to Earth, would you have to get before you could see any light from it with the human eye? I am also curious of the probability of a single photon making the entire trip from the surface of the Earth to the Sun, if any of our maths/physics wizards think they can calculate that 🙂 ---
**Author:** ![Angua](https://avatars.discourse-cdn.com/v4/letter/a/8baadc/32.png) [@Angua](https://boards.straightdope.com/u/Angua)\ **Post date:** [August 27, 2004, 5:42pm UTC](https://boards.straightdope.com/t/does-any-light-reach-the-sun-from-earth-how-far-does-it-make-it/261821/2 "2004-08-27T17:42:39Z")
> [@alterego](#): > > I know it takes something like 8 seconds for light to reach the Earth from Sun. Actually, its 8 _minutes_. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [August 27, 2004, 5:45pm UTC](https://boards.straightdope.com/t/does-any-light-reach-the-sun-from-earth-how-far-does-it-make-it/261821/3 "2004-08-27T17:45:48Z")
Sure light from Earth reaches the sun. Most of it will be light that came from the Sun in the first place and was reflected back, but surely at least some is from artifical sources. Photons don’t interact with each other, so the light radiating _from_ the Sun doesn’t interfere with light heading _to_ the Sun. ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [August 27, 2004, 6:14pm UTC](https://boards.straightdope.com/t/does-any-light-reach-the-sun-from-earth-how-far-does-it-make-it/261821/4 "2004-08-27T18:14:22Z")
> [@QED](#): > > Photons don’t interact with each other, so the light radiating FROM the Sun doesn’t interfere with light heading TO the Sun. Actually, at 100 km from the “surface” (photosphere) you are deep inside the chromosphere of the sun. There will be a lot of light scattered and radiated by the chromosphere and corona. The chromosphere is optically thin, but I think there’d be enough scattered light to wash out even the brightest stars and planets. If you go above the chromosphere, the earth should be easily visible to the naked eye. It’s as bright as Mars as seen from the earth. (Mars can get closer to earth than earth does to the sun, but Mars is smaller and dimmer than the earth.) ---
**Author:** ![Futile\_Gesture](https://avatars.discourse-cdn.com/v4/letter/f/f05b48/32.png) [@Futile\_Gesture](https://boards.straightdope.com/u/Futile_Gesture)\ **Post date:** [August 27, 2004, 6:17pm UTC](https://boards.straightdope.com/t/does-any-light-reach-the-sun-from-earth-how-far-does-it-make-it/261821/5 "2004-08-27T18:17:08Z")
> [@alterego](#): > > I know it takes something like 8 seconds for light to reach the Earth from Sun. I was thinking about from the Earth to the Sun though, and I don’t think it would make it all the way (overpowered). 8 Minutes actually. But there’s nothing to stop reflected light from the Earth returning to the Sun. In fact, the sun is one of the best places to see the most light, as you would always see a ‘Full Earth’, never a crescent. I suspect that maybe you’re getting confused by the problems an observer might have determining the dim light from the Earth among all the light being pumped out from the sun. This could certainly be a problem. But just because you might have difficulty seeing the Earth’s light in the full glare of the sun, doesn’t mean its not there. > [@](#): > > I am also curious of the probability of a single photon making the entire trip from the surface of the Earth to the Sun, if any of our maths/physics wizards think they can calculate that 🙂 If it’s heading in the direction of the sun upon leaving the Earth, and nothing solid gets in the way along the route, then the probablity is 100%. (This explanation conveniently side-steps all quatum physics, which would make the question a whole other ball game.) ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [August 27, 2004, 6:18pm UTC](https://boards.straightdope.com/t/does-any-light-reach-the-sun-from-earth-how-far-does-it-make-it/261821/6 "2004-08-27T18:18:27Z")
> [@scr4](#): > > The chromosphere is optically thin, but I think there’d be enough scattered light to wash out even the brightest stars and planets. Well, yes, but that’s because there’s _gas_ there that scatters the light. But that wasn’t what I was saying there. ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [August 27, 2004, 6:32pm UTC](https://boards.straightdope.com/t/does-any-light-reach-the-sun-from-earth-how-far-does-it-make-it/261821/7 "2004-08-27T18:32:30Z")
[Viewed from the sun](http://space.jpl.nasa.gov/cgi-bin/wspace?tbody=3&vbody=0&month=8&day=27¢ury=20&decade=0&year=4&hour=00&minute=0&fovmul=1&rfov=10&bfov=30), Earth appears within a degree of Uranus today. ---
**Author:** ![Jammer](https://avatars.discourse-cdn.com/v4/letter/j/df705f/32.png) [@Jammer](https://boards.straightdope.com/u/Jammer)\ **Post date:** [August 27, 2004, 6:51pm UTC](https://boards.straightdope.com/t/does-any-light-reach-the-sun-from-earth-how-far-does-it-make-it/261821/8 "2004-08-27T18:51:32Z")
I enjoyed that website, Squink. Any way to specify anything other that planets and/or the sun in the parameters? I would love to check out the earth from the moon using that simulator. Sorry for the slight highjack. Jammer ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [August 27, 2004, 7:02pm UTC](https://boards.straightdope.com/t/does-any-light-reach-the-sun-from-earth-how-far-does-it-make-it/261821/9 "2004-08-27T19:02:00Z")
The menus [here](http://space.jpl.nasa.gov/) will let you view earth from the moon. I went to the site, thinking it’d supply a magnitude for earth, viewed from the sun, but it doesn’t do that. ☹ ---
**Author:** ![PigBoy](https://avatars.discourse-cdn.com/v4/letter/p/97f17d/32.png) [@PigBoy](https://boards.straightdope.com/u/PigBoy)\ **Post date:** [August 27, 2004, 10:23pm UTC](https://boards.straightdope.com/t/does-any-light-reach-the-sun-from-earth-how-far-does-it-make-it/261821/10 "2004-08-27T22:23:49Z")
The program Starry Night, which I have on my computer (it came with a textbook), gives a magnitude of -3.82 for Earth as viewed from the sun. ---
**Author:** ![umop\_ap\_sdn](https://avatars.discourse-cdn.com/v4/letter/u/dbc845/32.png) [@umop\_ap\_sdn](https://boards.straightdope.com/u/umop_ap_sdn)\ **Post date:** [August 28, 2004, 2:07am UTC](https://boards.straightdope.com/t/does-any-light-reach-the-sun-from-earth-how-far-does-it-make-it/261821/11 "2004-08-28T02:07:27Z")
> [@PigBoy](#): > > The program Starry Night, which I have on my computer (it came with a textbook), gives a magnitude of -3.82 for Earth as viewed from the sun. [This NASA fact sheet](http://nssdc.gsfc.nasa.gov/planetary/factsheet/earthfact.html) gives Earth’s absolute magnitude as -3.86, which agrees with that figure if one takes into account that the Earth recently passed aphelion and is still more than 1 AU from the Sun. > [@scr4](#): > > It’s as bright as Mars as seen from the earth. Mars only got up to magnitude -2.96 (or about 7/16 as bright) at opposition last year, according to my calculations. ---
**Author:** ![alterego](https://avatars.discourse-cdn.com/v4/letter/a/6bbea6/32.png) [@alterego](https://boards.straightdope.com/u/alterego)\ **Post date:** [August 29, 2004, 12:59pm UTC](https://boards.straightdope.com/t/does-any-light-reach-the-sun-from-earth-how-far-does-it-make-it/261821/12 "2004-08-29T12:59:07Z")
> [@Angua](#): > > Actually, its 8 _minutes_. Whoops. I seem to have gotten a little ahead of myself there. ((( 🙂 ))) Thanks for all the information guys. ---
**Author:** ![Fuji\_Kitakyusho](https://avatars.discourse-cdn.com/v4/letter/f/f0a364/32.png) [@Fuji\_Kitakyusho](https://boards.straightdope.com/u/Fuji_Kitakyusho)\ **Post date:** [August 29, 2004, 6:33pm UTC](https://boards.straightdope.com/t/does-any-light-reach-the-sun-from-earth-how-far-does-it-make-it/261821/13 "2004-08-29T18:33:56Z")
> [@Q.E.D.](#): > > “Photons don’t interact with each other…” I was under the impression that photons exhibit both wave and particle properties, and are subject to reflection, refraction, diffraction, polarization and constructive and destructive interference. Is this not interaction? Perhaps it would be more correct to say that photons will not annihilate each other? ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [August 29, 2004, 7:26pm UTC](https://boards.straightdope.com/t/does-any-light-reach-the-sun-from-earth-how-far-does-it-make-it/261821/14 "2004-08-29T19:26:59Z")
> [@Fuji Kitakyusho](#): > > Perhaps it would be more correct to say that photons will not annihilate each other? Well, they _might_. But since a photon is it’s own antiparticle, and the result of annihilation is _photons_, who could tell? ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [August 29, 2004, 10:58pm UTC](https://boards.straightdope.com/t/does-any-light-reach-the-sun-from-earth-how-far-does-it-make-it/261821/15 "2004-08-29T22:58:09Z")
> [@Fuji Kitakyusho](#): > > I was under the impression that photons exhibit both wave and particle properties, and are subject to reflection, refraction, diffraction, polarization and constructive and destructive interference. Is this not interaction? It’s not interaction, because interference doesn’t change the photon’s momentum (i.e. wavelength and direction). Interference means when waves intersect, they superimpose upon each other. If you put a screen where they intersect, it may appear that the waves are cancelling each other at certain points and reinforcing at others. But if you remove the screen, each beam will continue on as if the other didn’t exist. Diffraction and polarization are both wave-like behaviors, but can happen with a single beam of light and has nothing to do with interaction. ---
**Author:** ![Bryan\_Ekers](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bryan_ekers/32/183_2.png) [@Bryan\_Ekers](https://boards.straightdope.com/u/Bryan_Ekers)\ **Post date:** [August 29, 2004, 11:07pm UTC](https://boards.straightdope.com/t/does-any-light-reach-the-sun-from-earth-how-far-does-it-make-it/261821/16 "2004-08-29T23:07:17Z")
Not only does the Earth reflect a lot of light, the light twinkles. Just ask Leonard Nimoy. ---
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [August 30, 2004, 5:15am UTC](https://boards.straightdope.com/t/does-any-light-reach-the-sun-from-earth-how-far-does-it-make-it/261821/17 "2004-08-30T05:15:04Z")
> [@Squink](#): > > Well, they _might_. But since a photon is it’s own antiparticle, and the result of annihilation is _photons_, who could tell? As I understand it, particle interactions are reversible. That means that two photons could meet and form an electron/positron pair. Or possibly some other particle/antiparticle pair. In order for this to happen, the energies of the photons would have to add up to the energy equivalent of the rest masses of the particles. Sunlight and reflected sunlight are no where near energenic enough for this to happen, so it’s not a significant factor to the OP. ---
**Author:** ![t-keela](https://avatars.discourse-cdn.com/v4/letter/t/a3d4f5/32.png) [@t-keela](https://boards.straightdope.com/u/t-keela)\ **Post date:** [August 30, 2004, 5:22am UTC](https://boards.straightdope.com/t/does-any-light-reach-the-sun-from-earth-how-far-does-it-make-it/261821/18 "2004-08-30T05:22:36Z")
8 seconds? damn I knew it was hot lately but shee-it. 😃