# Does any light reach the Sun from Earth? How far does it make it?

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

Actually, its 8 minutes.

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.

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.)

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.

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.)

Well, yes, but that’s because there’s gas there that scatters the light. But that wasn’t what I was saying there.

Viewed from the sun, Earth appears within a degree of Uranus today.

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

The menus here 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.

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 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.

Mars only got up to magnitude -2.96 (or about 7/16 as bright) at opposition last year, according to my calculations.

Whoops. I seem to have gotten a little ahead of myself there. ((( )))
Thanks for all the information guys.

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?

Well, they might. But since a photon is it’s own antiparticle, and the result of annihilation is photons, who could tell?

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.

Not only does the Earth reflect a lot of light, the light twinkles.

Just ask Leonard Nimoy.

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.

8 seconds?

damn I knew it was hot lately but shee-it.