I recently saw for sale (from China) cordless anti-static wrist straps.  Apparently you just slip the bracelet on - no grounding required - and any static charge you might have disappears.  How on earth do they work?

Recently a news report used the word 'thousand billion' and I wondered why they did not just say 'trillion'? But according to Wikipedia (http://en.wikipedia.org/wiki/Orders_of_magnitude_(numbers)#Smaller_than_10.E2.88.9230) a thousand billion is one above a trillion. 

Here's the problem:

A billion is 1 followed by 9 zeroes.

A trillion is 1 followed by 12 zeroes.

A thousand billion is 1 followed by 15 zeroes.

Is Wikipedia wrong? The difference between 12 and 9 is 3, which is a thousand in terms of zeroes. So, isn't a trillion and a thousand billion the same thing?

Not as you see it, but as a cross-section, I mean - how thick is the layer of graphite/carbon? How many atoms thick?

Prematurely overcome by the holiday spirit, we failed to send a round-up last week. Apologies for that. One of the most popular questions from that week – also with a holiday flavour – was what to do during a lightning storm at the beach. Are you safer on the beach or in the water? The discussion contains a fair bit of disagreement, but some great tips for optimum lightning-avoidance behaviour.

This week's questions started with whether the wind affects sound waves (it does, but not in the way you might expect), and whether the foods we crave are the ones our bodies actually need (let's hope so).

Here's one for the physics-minded: ever wondered why most rocket launch pads are sited near the equator? It's to make the most of the rotational velocity of the Earth's surface, which is greatest at the equator. But can you think of any other ways we exploit this tremendous energy source? So far, not many readers can.

If you've ever been caught by brambles while walking in the countryside, you might be curious why the thorns of roses and blackberries are designed to catch animals rather than repel them. Could it be that roses are actually carnivorous?

Finally, August is the month for… meteor-hunting. The Perseid meteor shower is at its height on 12 August. One of our readers reckons he can hear meteors. Is that possible?

Enjoy your weekend.

Michael (acting for Kat)

These photos were taken in my parent's garden, Gloucestershire, during the snowy weather in January earlier this year.

The first photo shows the footprints starting near to the back door of their house, the second shows them making their way past the side of the house in a very straight line and the final photo shows them simply stopping.

We're still all very puzzled and wondered if anyone had any theories or ideas?

i have this Physics question from my teacher that says:

'Dogs are pulling a sled on the snow. If the dogs have stopped pulling draw the force diagram'

Well apparently the question only had three forces - gravity (pulling down), reaction forces (arrow going up), and friction (pulling the opposite directiong of the sled).

Well we also learnt that forces come in pairs so can someone please explain how this is possible. And if it is not can you please give the correct answer as I also put the force inertia which is currently wrong...

Is there a mathematical description as to why 0 divided by 0 is 0. Also why 1 divided by infinity is also 0?

If the Moon lost orbit somehow for whatever reason, how would the timeline of the crash look like.

I'm thinking of these ingredients:

- slowly dropping free fall

- at some point it will enter atmosphere, what happens to the Moon?

- tidal waves, will the Moon break up and would cities be flooded during downfall

- say the Moon crashed into solid land, wat kind of crater would it leave, what would it do the the immediate surrounds (shockwave?)

- what happens to the atmosphere if anything at all, and what about the magnetic field?

- will humanity survive or perish, and by what cause?