Expert: Philip Stahl - 8/9/2006

Question
Hi,

Thanks. It is a new information to me. From what you say, if I am in space just above the moonless night sky, I can't even see the earth. Right?

If I look around, I will see a dark sky with many stars and a big starless round space (Earth is blocking my view to any stars/ sun/moon!)! Right?

The reason for asking the question. I am writing a book in which I want to write 'One can not see the light. One will know that there is light only with the help of objects which are illumined by the light. If there are no objects around, even if there is very bright light, one will see nothing'.  

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Followup To

Question -
Is the natural light from distant stars enough to see in space? How bright it will be? Suppose my wrist watch falls down (or up!),- when I shake my hand - how far I can follow it by my eyes. If it is very dark...can I see my own hand?

Thanks for your time and effort.
Raja Subramaniyan

Answer -
Hello.

Because the stars are so distant - their natural light - even in space, would be too faint to see by. Thus, any astronauts wold either have to use the Sun, or artificial illumination.

If you observed your hand or a watch in space, it would not be from star light - but more likely sunlight.

Answer
Hello.

If you are above the *night side* of Earth, there will be extremely faint illumination depending on where exactly you are situated. This isn't coming from distant stars but more likely from large cities on Earth. However, this will almost surely be inadequate light to see by. Far less tell time on a watch - unless it has radium dials!

It is also true that while you can't see the Earth in its entirety, you are likely to see at least its *outline* - because of the atmosphere which will scatter any light on its surface. Pollution effects will also add to this. Thus, you are most likely to see a faint 'rim' for the planet - as opposed to not seeing a planet at all.

On the other hand, if Earth had no cities, no massive energy use, and no atmosphere - then true you'd likely see nothing at all.

If you look toward the darkish Earth, yes - it will block any stars (as well as the Sun and Moon) in the line of sight. If you look in the opposite direction, you will see tens of thousands of stars of differing brightness -but definitely better than you'd see them on Earth (which has a shaky atmosphere and lots of light and other pollution)

Strictly speaking - as I pointed out - it's not truly accurate to say you will see "absolutely nothing". There will be faint light outlining Earth - as I noted -primarily because the planet already has lots of (artificial) light on its surface and the atmosphere increases its effect (light pollution, scattering).  So it's not as if you're looking at pitch blackness and no hint of *any illumination*.

Still I would not want to try to read by it!

Stars will also be visible, as I noted - but again their light is too faint to anything with.