We have had a week of involved debates on The Last Word. markct1989 caused a storm with his question: how do you define temperature? Check out the various definitions suggested by the Last Worders: http://bit.ly/dYJwIi

Another debate, which has been raging for over a week, stems from translatrix's observations that the amount of water in a sealed plastic bottle seems to decrease over time. Can water evaporate through plastic? http://bit.ly/g2SOWv

petethebloke asked us: how long have humans been as intelligent as they are now http://bit.ly/exZyaD? The question got our Facebook followers ever so excited: http://on.fb.me/dL0IK0

Another of this week's questions was similarly popular on Facebook: why do flames make a noise when you blow them out? See if you think Last Worders http://bit.ly/dWU3me? or Facebookers http://on.fb.me/h9Dzfh have got to the bottom of it.

Our very own Feedback editor joined the fray this week when tbrucenyc wanted a bit more explanation of one of the week's Feedback items. What's so funny about computer algorithms? Find out here: http://bit.ly/gN5KyS

If you want to test your mettle, why not see whether you can provide an explanation as to why fingernails grow faster than toenails? http://bit.ly/hohXCg

Hope you have a great weekend,

Kat

Letters and comments editor, New Scientist

Image: www.shutterstock.com

Georg raised an interesting point when pointing out that Wikipedea is not the best or most reliable sorce for science research. I now realize that my science education is from a lot of sources; very few of them primary.I think I get the best stuff mostly from text books but also from popular science books, television, radio, periodicals, encyclopedea's, newspapers and, of course, the "Internet". Which of these do Last Worders prefer?

What is the diameter of a weather balloon (in meters) filled with He at 15,000 m? On the ground the balloon was filled with He at 18 °C at 0.96 atm to a volume of 7.3 L. At 15,000 m the atmospheric pressure is 10.8 kPa and the temperature is -79 °C. Recall the volume of a sphere equals (4/3)πr 3 and that one liter is 1 dm3. What is the volume and the diameter?

Welcome to another round-up of the week's excitement on The Last Word, and what a collection of questions and answers I have for you this week!

Ever been out camping and found you've forgotten to bring matches? In the daytime you can always whip out a mirror and use sunlight to spark your fire… but can you light a fire with starlight? The Last Worders have a crack at quantifying the likelihood here: http://bit.ly/dMB0Fc. That's not the only option though, you could employ the method that caused a spontaneous fire in Paul_Pedant's briefcase: http://bit.ly/fpzgV7

Suppose you desperately need to cook a turkey and you still can't light a fire. Well, maybe there's a more unconventional solution. This week, doedfisk asked us: what's the optimum altitude from which to drop a turkey so that it cooks on re-entry to the Earth's atmosphere? http://bit.ly/emIFmC

Now for something a little different. How do you relate bones to Greek legends? Last week Apqad asked us whether, if you didn't know what an elephant looked like, you could tell from looking at its skeleton that it had a trunk and large ears. LokiNight has just come up with a very interesting answer relating prehistoric dwarf elephant skulls to the Cyclops legend of ancient Greece. You can find out more here: http://bit.ly/dTnVTz

Keeping on the theme of bones, is cracking your knuckles bad? http://bit.ly/h6rG3z? In my opinion, yes, if I have to hear it. I get grossed out by my own ankle clicking.

To finish off we have something completely different. John Chapman asks: how do anti-static sprays work? Where do the electrons go to or come from to neutralise a charged surface? http://bit.ly/glpe6h

Just to remind you, if you answer any of the questions that appeared in New Scientist magazine – like John Chapman's question above – and we print your answer on The Last Word page of the magazine, you will win a cheque for £25 (or the US$ equivalent). But we can only send it to you if you provide us with your address in your online profile!

Have a great weekend,

Kat

Letters and comments editor, New Scientist

Say there was a tunnel that went through the centre of the Earth that came out on the exact opposite side to the entrance. If you jumped down it, would you have the momentum to fly out of the other side, or would you be pulled towards the Earth's centre of mass and be crushed? This is assuming of course that the person will not burn :P

I've been dropping squash balls at different temperatures from a constant height of 1m, and measuring the height they bounce up to. I understand that as you heat the squash balls, air molecules inside the ball (which has negligible increases in mass and volume) bounce again each other and the inside of the ball more often and harder, leading to more air pressure in the ball, and thus a higher bounce. Is there any equation that links pressure or temperature with a drop height and bounce height? I've been using Boyle's law, Charles law and the pressure law to find pressure, and there are existing formulae for volumes, of course, but how can I link pressure with bounce? I assume it will involve the coefficient of restitution somewhere, but I'm unsure. Thanks a lot! :)

Eg: N2(colourless gas)+O2(colourless gas)=NO2(brown coloured gas)

Hello Last Word folks, are you looking forward to the weekend?

If you are going to watch some kind of sports this weekend – say the Aston Villa v Arsenal match tomorrow that is likely to split my family down the middle – why not spend half-time pondering how many goals would be scored if you played football with two balls? http://bit.ly/etUcCq?

Or perhaps you'll be seeing the in-laws? In which case this question might be more pertinent: why is it that so many people can't keep their noses out of other people's lives? http://bit.ly/eeqhjf Do you think there could be an evolutionary advantage to interfering?

Last weekend saw some animal experimentation, in the form of gummy bear-icide by Last Worder ln64z3. On trying to melt one of these cute candies over a campfire, he was most surprised to see it bubble instead of melt. Can you help explain why it frothed instead of dripping as you might expect? http://bit.ly/9dqkn2?

While ln64z3 was having fun toasting gummy bears, I was flying back from a diving trip in Egypt. So I was thrilled to see a timely question on The Last Word to greet my return. dendurrant has been wondering why the Red Sea is so much warmer at depth than other seas and oceans. It seems I have the thermal vents in the seabed to thank for keeping me warm: http://bit.ly/gPiDaA

Finally, here is a question still in need of a complete answer. Can you tell us why some hairs are thicker than others? We have had some amusing and informative answers, but are still in need of an expert to solve the query: http://bit.ly/i8BM8r?

Hope you have a fantastic weekend,

Kat

Letters and comments editor, New Scientist