Grazza

If the spots on the banana were to be a symptom of radiation poisoning, i would have thought that they would be more uniform over the banana's surface. After all, the potassium would be shared roughly equally around the banana's cells, so instead of getting brown patchy spots, i would expect the whole banana to just gradually darken. Also the flesh of the banana does not go brown (unless you drop it/mash it into a sandwich, great!) and a high proportion of the potassium is to be found here. So i don't think radiation has anything to do with the banana's ageing. Of course, in a few years time, there may not be bananas anymore, unless something is done to strengthen the poor clone's gene pool. So i think we should appreciate them whilst we can.

OK, so this is how i understand it... the speed of sound is dependant on the density of the medium it is traveling through, the denser the substance the FASTER the sound travels, this is because the individual molecules are in closer contact with eachother. The speed of sound in water is about 5 times faster than in air, and sound waves travel through the ground at much greater speeds. so helium is less dense than air (in g/cm3), but i think the real issue here is the concentration of the gases, i.e. the number of mols (or molecules) per volume of air (i think at 1 atm pressure the density of any gas is 1 mol per 24 litres). As, at atmospheric pressure the concentration of all gases is the same (be it halium, oxygen or a gas mixture like air), the speed of sound should be the same in all gases. Now if we change the pressure we can change the pitch of the sound, higher pressure will cause the sound to move faster and thus sound lower (lower frequency), lower pressure will have the opposite effect. So if i pressurised the air around my head and you talked to me i guess it could sound really deep, though i don't think i'm going to try (might get the bends!). I presume this is why, (if you've ever tried it) when you talk underwater (more dense) it sounds deeper, though that could just be an effect of being stupid! Hope this is right, and has been some help. g

hi there guys. hope everyone is pushing back those boundaries. g