June 20 – Georges Lemaître

The Belgian priest and astronomer luxuriating in the just-about-tweetable name of  Monseigneur Georges Henri Joseph Édouard Lemaître died on June 20th 1966.

A ripple of controversy surrounded our subject in 2011, when it was suggested that the Hubble constant should more properly be attributed to Lemaître, rather than the eponymous Edwin.  It had been said by some that Hubble, or someone in his circle, edited a paper by Lemaître in an inventive way, so as to make it less than obvious that Lemaître had got to the discovery of an expanding universe before Hubble.  It later turned out, however, that it was Lemaître himself who had omitted vital elements of the paper, possibly due to a linguistic misunderstanding.

Lemaître was an early pioneer of using Einstein’s equations to solve cosmological problems (Einstein himself wasn’t so sure they ought to be).  He was the first to estimate the Hubble constant, as already mentioned, and to  derive Hubble’s Law.   And just in case you thought that was enough, he was also the first person to propose a Big Bang type theory to describe the birth of the universe.

Monseigneur Lemaître

Monseigneur Lemaître

I won’t try to explain Hubble’s law here (because I probably can’t).  It can be expressed as a very simple equation to explain a very complicated situation, and if I start I might not be able to finish.  Let’s just settle for saying that the rate of movement of galaxies away from the Earth is proportional to their distance from the Earth and from each other, and it’s the Hubble constant that gives us the magic number that let’s us prove the proportionality.

Lemaître was extremely important for someone most of us have never heard of, and was honored all over the place while alive.  He was voted 61st in a survey of the 100 greatest Belgians in 2005.


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