We’ve just been watching a Horizon programme about gravity.  Newton, apparently, got it wrong; if you calculate his formula the moon should be about 10m to the left.  As GP2 said “That’s like getting 99 1/2% in a test and being told you have to try harder”. 

How do they know all this?  Buzz & Neil & Co left an 18 inch mirror on the moon and scientists somewhere in America spend their nights – or is it days? – aiming a laser beam at this mirror – 18 inches square, remember – via a telescope and calulating how long it takes for the protons (I think it was protons) to come bouncing home.  The only thing is, it’s not quite as reliable as carrier pigeons – they have to send out tens of thousands of protons in the hope that half a dozen make it back.  I mean to say, how far away is the moon? 384,403 km according to Wikipedia.  I bet they couldn’t do the equivalent in the oceans; it would be like trying to pick out a specific sand grain on the seabed.

Einstein got a bit closer but didn’t get things quite right either.  He figured out that spacetime exists and that time and space are distorted by and bend around large objects.  Planets and such like, not cars and houses.  So time in space ticks by faster than time on earth which means that, if you want your GPS to get you to the right place, someone has to correct the time on those satellites up there in the cosmos.  There are people sitting on an Air Force base somewhere in the States whose job it is to send the right time to the satellites.  I guess they have to correct for the time it takes for the signal to get from Earth to the satellite – taking account of spacetime distortions, of course.

Moving on, quantum physicists reckon that the explanation of gravity exists in sub-atomic particles called gravitons and collision theory.  The trouble is, they haven’t found any yet and have only found an absence where they think a graviton or two might have been.  It’s here that we drift off into Philip Pullman territory and the realms of parallel universes; the scientists predict that there are other dimensions that we don’t yet know about where these gravitons spend most of their time. 

Well, I hope you understood all that.  If you did, perhaps you could explain it to me.  And if they repeat the programme, it’s definitely worth watching.  One thing though, that GP2 pointed out:  if there’s a mirror on the moon, the moon landing must have happened and all those conspiracy theories must be wrong.  Mustn’t they?