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)

Can your voice really be "snatched" away by the wind, or is it just that the sound of the wind covers the sound of your voice. If wind does affect sound waves, can it also affect light?

How comes that, when the wind comes from the railway, I can hear the trains much better. I understand that it should reduce the effective distance of the railway, but the wind is usually not over 50 km/h, very small compared to the speed of sound (1200 km/h), so the effect should be tiny.

The standard answer to this question is that our brain picks up the tiny difference between the times at which a sound arrives at each ear, and from this figures out where the sound is coming from. But simply selecting points with a particular difference in their distances will yield an entire conical surface of possible origins. Distance, I suppose, can be judged from the softness of the noise, but how do we tell which of the possible directions the sound is actually coming from?

If you played the same note, in 500 versions of exactly the same speakers (so all the same frequencies) at the same distance from the receptor (ear or decibel meter), would it be the same volume? 

If it would increase, how much by and why? 

Would it be 500 times? Or would some be cancelled out?

Thanks!

As a young child, I used to love putting the shells like the ones in the picture, into my ear to listen to them. I remember being told that you hear the waves in them. I know that's not entirely true, but what exactly causes the sound we hear? And why don't we hear such sounds if we put other objects like it up to our ear?

I observed some years ago that if, having first stirred a mug of hot-chocolate one taps the bottom of the mug from within with a metal teaspoon the note given off rises quite distinctly with each tap. I have not reproduced the same effect with tea or coffee. However, any normal ceramic mug and brand of drinking chocolate seems to produce the effect. What, if any, are the special properties of hot-chocolate that produce this rising note effect?

I notice that at random times my stomach rumbles unexpectedly... what is actually going on down there and why is it happening?