Mind your head and that falling Apple

[BertiWooster]

So , Professor Brian Cox was explaining to me on a programme on the box last night , that the great Sir Isaac Newton’s laws enabled man to go to the moon .

However , he was explaining that his laws or one of them is not quite correct – something to do with some measuremnts using a mirror left on the moon ?

I nodded off ( nothing to do with Brian Cox , mind – in fact I like watching him ) – however it was the second programme in a row I was watching and it was quite late .

Anyway , what exactly is wrong with the great man’s laws .

Please frame your explanations in a form that little ‘Johnny’ can understand

[jake-the-peg]

Newton's laws of Gravity are generally fine.

It's just when youi make very fine measurements in strong gravitational fields you find that they are not quite right.

In 1915 Einstein published General relativity. This did two spectacular things. Firstly it explained the orbit of Mercury which wasn't right by Newton, the numbers didn't add up to what was observed.

It also predicted that light could be bent by a strong gravitational field like the sun. So the next solar eclipse everybody headed off to observe. If Einstein was right light from stars should bend and the stars appear to be slightly the wrong position as they graze the sun and moon.

And they did - it was a spectacular proof and cemented Einstein's reputation

[jake-the-peg]

Oh as for the moon mirror, the Apollo astronauts left a special laser reflector on the moon and a laser can be bounced off of it allowing the distance to be meacured to pinpoint accuracy.

You'd have to use Einstein to correct for this too.

Likewise the GPS in your car would be off if Einsteins equations were not used