On the first night of heavy snow - tues 5th Jan - it was cloudy but the sky was  a very light sepia tone all night - enough to see clearly by. It was much more light than on the subsequent nights which have been partially cloudy with a visible moon. On these nights there was the same amount of snow cover, but less cloud. 

On the sepia night it was lighter than if there had been a full moon.

When looking at fairy lights of different colours without my glasses, different colours flare different amounts. Blue the most followed by green, yellow then red. Why?

For my 18th birthday I received a silver bracelet, with what I believed were amethyst or similar stones set into it.

However, the purple stones appeared blue under the flourescent lighting in the biology labs, and under another type of light seemed clear white. Once under sunlight the stones again appeared their normal purple colour. There was no gradual fade of colour - moving from one light to a window yielded instant change - and under normal lightbulbs the stones also appeared purple, and the same with any light mixed with sunshine.

Is this to do with how the stones were cut, how they reflect the light, or is the stone itself responsible?

Thanks,

Eleanor

My 9 yr old son asked me: if he installed a torch inside a sealed flask made of mirrors and illuminated it briefly, would the light remain in the flask to "flash" out if it were opened. I answered that the light would decay away as mirrors do not reflect all the light and that this would be to quick to measure the decay period - thus, when opened, there would be no light relecting around in the flask. Am I right?

Say you have two people holding either end of a very long (several light seconds), taut string. The first person gives the string a pull (supposing he is able to pull a string of that mass), and the second person holds the other end (whilst watching the first person through a powerful telescope). Does the second person feel the pull before, at the same time or after he sees the first person pulling?

Nothing is supposed to travel faster than light, so what happens to the string to allow the force to be transmitted slower than it?

As an amateur photographer I'm familiar with the idea of light having a colour temperature and having to adjust a camera for white balance e.g. early morning light is much warmer than midday. I've read in books on photography that light before dawn is always colder than the light after sunset.  I would have expected it to be the same.  Why should the direction of the light affect its temperature? Is this just a UK phenomenon or is it worldwide ?

Sitting recently in my school's gym, I noticed that the aging flourescant lights tinged the whole hall a slight orange colour. Looking towards the windows, I noticed that the light pouring in appeared to be blue, without the sky being visible. It struck me that perhaps - as you place a blue filter in front of a light - the sky, during the day, tinges everything we see a slight blue. Is this possible?

I have a Laser Detector for my Rotating Building Site Level. In a room with an Energy Saving bulb, if I only turn the detector on , it ‘Beeps’, advising it has received a signal. This doesn’t happen in a room fitted with an old fashioned tungsten bulb. Does an Energy Saving bulb give off Laser Light?