Tag: Aristotle

What I really admire are people who, through their sheer brain power, can change our views of the world.  The first example that comes to mind is Newton’s insight that if the universe were infinite, the night sky would not be dark as everywhere there would be tiny pinpricks of starlight.  So, we don’t live in a infinite universe. Another one is Einstein’s thought experiment that proves that time is relative. But see below for a description of that. 

But now to Goodricke.

Yesterday in York, near the Minster, I saw the blue sign above, which I read and thought, what on earth are ‘variable stars’?  Behind me, I heard two women say something like. ‘Here it is,”variable stars”‘.  I turned around and asked them what was a variable star?

‘Donno’ they said, ‘we’ve ‘just doing this escape room walk around York.’  They showed me a booklet they had received on the internet, which was what I would call a treasure trail.  But no, they insisted, ‘this is an escape room adventure where we collect clues to decipher the code to escape’.

Such is the modern tourist!  Sadly, they showed no interest in finding out what a variable star is!

Aristotle and ancient philosophers held that the universe was unchanging and eternal. The first breach in that theory was the identification in 1638 of star Omicron Ceti by Johannes Holwarda who discovered that the start pulsed on an 11 month cycle.  This and the discovery, of supernovae (first observed in 1572), proved that the ‘The starry sky was not eternally invariable’.

John Goodricke was educated at Thomas Braidwood‘s Academy, school for deaf pupils in Edinburgh, and Warrington Academy. He returned to live with his parents who rented an apartment at the Treasurer’s Hall, near the Minister in York, and used a friend’s personal observatory to look for variable stars. He found two of the first 10, and was the first to propose a solution, which was that two stars orbited each other causing eclipses between them and the observer, and thus creating a variation in the light emitted. To be able to extrapolate from a simple observation and provide an explanation which necessitates a complete rethink about the nature of the universe seems, to me, to be awesome.

Back to Einstein, his thought experiment was something like this:

A train is travelling through a station. There is an observer on the train towards the front, another on the platform as the train goes through. There are two simultaneous lighting strikes at either end of the train. The observer on the platform sees the strikes as simultaneous as she is in the middle between the two lighting strkes and light travels at the same speed. The observer on the train who is near the front of the train will see the lighting strike at the front of the train before the light from the back of the train can reach him as it has further to go.

This is mind-boggling, and I’m never sure what to make of it but it means that time is not a constant it is relative to the observer. And yet, we see time as a constant, something that remorselessly ticks forward and which we cannot alter. But it isn’t.

For a better explanation, see https://en.m.wikipedia.org/wiki/Relativity_of_simultaneity