I remember reading a SF book in the 1960s which included a means of weather control. The theory given was that in an arid region, a length of tough flexible plastic tube was prepared. One end of the tube was anchored down, allowing a flow of air to enter the base, and then air was pumped into the end anchored. The tube was inflated and gradually stood up with the column of air extending the vertical tube. At a critical height the warmer air at the base of the column would begin to be sucked in to replace the cooler air rising to the top. The pump could be switched off and when fully extended at a predetermined height column of cooler air at the top would condense into clouds and result in rain. This would be self sustaining with the cool air being drawn in at the base and escaping at the top. The technology and materials were obviously not available when the book was published,  but is this still true today?

How much water, World wide, is in the atmosphere. If there were no rain clouds or humidity across the planet, how much deeper would the oceans be?

If the sun was extinguished or there was a permanent worldwide eclipse, how long would it take for us all to freeze to death, and what could we do to try to avoid it?

Darren Darby, London, UK

(Image: Lucien Rudaux, Wikimedia Commons)

James Scowen, London, UK

I have just read the label on my shampoo bottle. The list of ingredients is mind-boggling. How on earth did anyone come up with such a complex concoction and what exactly are chemicals such as sodium diethylene-triamine pentamethylene phosphonate and hydroxyisohexyl 3-cyclohexene carboxaldehyde doing to my hair?

Haydn Ford, Hexham, Northumberland, UK

(Image: LotusHead, stock.xchng)

The Last Word has told us why garlic makes your breath and body smell, but I want to know why the spice methi, or fresh fenugreek, has a similar, possibly stronger, effect.

Nikki Bedi, BBC Radio Asian Network, UK

(Image: Wikimedia Commons)

A number of athletics and cycling world records have been set at high-altitude venues, for example during the 1968 Olympic Games in Mexico City.

Presumably the air is thinner so there is less resistance, enabling them to run or cycle faster. But surely oxygen uptake at altitude is more difficult, so there must be a point at which altitude no longer favours athletes.

What is this point and why? And which tracks or velodromes come nearest to it?

Carlos Loeb, Madrid, Spain

(Image: Wikimedia Commons)

At breakfast one day, my 4-year-old son was peeling his boiled egg when he noticed something unusual. On the side of the egg was an almost perfect white square with sides about 1 centimetre long. This was enclosed in an oval patch of yellow matter (see photo, left).

Although the yellow patch looked like egg yolk, the egg appeared normal when I cut it in half, and I could not see any connection between the egg yolk in the centre and the yellow patch on the outside.

Does anyone know how this formation was created?

Johan Forsberg, Linköping, Sweden