If you covered the surface of the moon with mirrors..

[Jon O'Neill]

Would it be daylight all the time on Earth?

[John Bosley]

No

[Andy Wilson]

That was a very bright thought though.

[Jon O'Neill]

If not, why not?

[Matt Morrison]

They would float off. You're not allowed to take sellotape or glue to the moon either.

[Rosemary Roberts]

If not, why not?

The moon isn't in the sky all the time. If you managed to really light up the moon you would be in a "Nightfall" situation.

[Mark James]

I think the moon is as mirror like as it can get anyway.

[Ryan Taylor]

I wish more exam questions lower down the school started with things like this:

Q. 'Jon says that "if you covered the moon with mirrors it would be daylight all of the time". Explain why Jon is wrong.' (8)

[Phil Reynolds]

If not, why not?

For starters, what happens when the moon is between the sun and the earth?

[Gavin Chipper]

If not, why not?

Start off by telling us why it should.

[Graeme Cole]

Would it be daylight all the time on Earth?

Nope. As Rosemary said the moon isn't always above the horizon. Also consider the phases of the moon: if it's a new moon then it's the far side of the moon that's illuminated, which is no use to an observer on earth even if the moon were a perfect mirror.

Incidentally, the moon's reflectivity (or albedo) is actually quite low, but it does have the property that it most of the light it reflects is reflected back in the direction it came from. This is why the moon looks disproportionately brighter when it's a full moon than when it's almost full.

(Alternatively, you could answer the question with "it is daylight all the time on earth, just not in the same place".)

[David Williams]

Surely what would be reflected to earth is a distorted reflection of the whole sky. All you'd see is a small dot of light from the one point on the moon that reflects the sun our way.

[Matthew Tassier]

By some quick and probably flawed calculations, if the moon were a spherical mirror the amount of light reflected to us even at full moon would be less than 1/40000 of the amount we receive directly from the sun in daylight. Due to angles and stuff. You'd do much better doing what the Russians tried and putting large mirrors in earth orbit.

[Jon O'Neill]

By some quick and probably flawed calculations, if the moon were a spherical mirror the amount of light reflected to us even at full moon would be less than 1/40000 of the amount we receive directly from the sun in daylight. Due to angles and stuff. You'd do much better doing what the Russians tried and putting large mirrors in earth orbit.

Cool.

Thanks everyone.