Post by Catsmate on Jun 8, 2021 10:07:19 GMT
The Eddington Expedition.
Oh leave the Wise our measures to collate
One thing at least is certain, light has weight
One thing is certain and the rest debate
Light rays, when near the Sun, do not go straight.
I've been musing recently on the various experimental proofs of Relativity that have been carried out. Today the necessity for daily corrections to the various satellite positioning networks1 demonstrate this well, but over they years various experiments (such as the Pound-Rebka which I helped repeat as an undergrad)
But the original, and most celebrated, proof was the Eddington-Dyson2 experiment in 1919.
The basis for the experiment is pretty simple, if one omits most of the details of Relativity. Einstein predicted that passage by a massive object would deflect light. Now this wasn't new, Newton had made a similar prediction centuries earlier, but because of the differences in their respective models of gravity the amount of deflection was greatly different; it would be twice as large if Relativity, as theorised by Einstein, was correct.
It was possible to see and measure this deflection of light from a distant star passing by the Sun. However it would need a solar eclipse to take photographs for measurement as otherwise the solar glare would obscure the vastly dimmer stars. Unfortunately total solar eclipses are fairly rare and generally best visible form locations near the equator. Hence the twin expeditions in 1919 to Brazil (the town of Sobral) and Príncipe (an island then in French West Africa) to take photographs.
Organised on a limited budget the expeditions each has two members.
Eddington and Edwin Cottingham (an instrument maker and technician from the Cambridge Observatory) went to Príncipe and two staff from the Greenwich Observatory (Andrew Crommelin and a 'computer', Charles Davidson) went to Sobral.
The expeditions were organised in a hurry, given that the war ended not long before. While Crommelin and Davidson had few problems in Brazil (though some of the photographic plates were blurred due to technical issues with equipment) and the measurements were excellent (showing values far closer to the Einstein prediction than to the Newtonian), the same was not true for Eddington and Cottingham.
Their trip was beset by problems carrying the delicate cameras, telescopes and chronometers, poor weather conditions and a steamship strike.
Nevertheless their data demonstrated the validity of Relativity and garnered newspaper headlines across the world, catapulting Einstein to fame.
The definitive book on the experiments is Kennefick's No Shadow of a Doubt: The 1919 Eclipse That Confirmed Einstein’s Theory of Relativity. It's well worth a read. The BBC programme Einstein and Eddington is also a good account of the experiment and it's background. With David Tennant as Eddington...
Game use.
I see three main ways to inject this little element of science history into an AITAS game.
1. A mostly historical encounter.
The party arrives in one of the two observation locations and meets the teams, perhaps helping Eddington with his observations? Or at least to carry stuff. This strikes me as the perfect opportunity for Sixie to drag Peri along to witness Science being done.
2. There's something weird up there.
For a more fantastic theme, perhaps the pictures showed something weird. The stars photographed were the Hyades (because they were a notably a bright group of stars) which have been associated by Lovecraft with Hastur and Carcosa.
3. Meddling
Or is someone attempting to prevent the observations, for some reason? While this might delay the acceptance of Relativity it probably wouldn't have much long-term effect. Or is Eddington himself the target?
Comments? Suggestions? Ideas?
1. Without corrections for both Special Relativity (time flowing more slowing for objects in motion under angular acceleration) and General relativity (spacetime is less curved by the mass of the Earth at their orbital heights) the system with become inaccurate by around ten kilometres per day.
2. Frank Watson Dyson tends to be forgotten about in relation to the experiment, perhaps because his part was organisational and theoretical. He was Astronomer Royal and also originated the 'pips' time signal broadcast by the BBC in 1925.
Oh leave the Wise our measures to collate
One thing at least is certain, light has weight
One thing is certain and the rest debate
Light rays, when near the Sun, do not go straight.
I've been musing recently on the various experimental proofs of Relativity that have been carried out. Today the necessity for daily corrections to the various satellite positioning networks1 demonstrate this well, but over they years various experiments (such as the Pound-Rebka which I helped repeat as an undergrad)
But the original, and most celebrated, proof was the Eddington-Dyson2 experiment in 1919.
The basis for the experiment is pretty simple, if one omits most of the details of Relativity. Einstein predicted that passage by a massive object would deflect light. Now this wasn't new, Newton had made a similar prediction centuries earlier, but because of the differences in their respective models of gravity the amount of deflection was greatly different; it would be twice as large if Relativity, as theorised by Einstein, was correct.
It was possible to see and measure this deflection of light from a distant star passing by the Sun. However it would need a solar eclipse to take photographs for measurement as otherwise the solar glare would obscure the vastly dimmer stars. Unfortunately total solar eclipses are fairly rare and generally best visible form locations near the equator. Hence the twin expeditions in 1919 to Brazil (the town of Sobral) and Príncipe (an island then in French West Africa) to take photographs.
Organised on a limited budget the expeditions each has two members.
Eddington and Edwin Cottingham (an instrument maker and technician from the Cambridge Observatory) went to Príncipe and two staff from the Greenwich Observatory (Andrew Crommelin and a 'computer', Charles Davidson) went to Sobral.
- The 1919expedition wasn't actually the first attempt. The eclipse visible from the Russian Crimea in 1914 has been attempted. Unfortunately the start of the Great War in July meant that the German scientists were either unable to enter Russia or were arrested, and heavy cloud made useful photography impossible.
The expeditions were organised in a hurry, given that the war ended not long before. While Crommelin and Davidson had few problems in Brazil (though some of the photographic plates were blurred due to technical issues with equipment) and the measurements were excellent (showing values far closer to the Einstein prediction than to the Newtonian), the same was not true for Eddington and Cottingham.
Their trip was beset by problems carrying the delicate cameras, telescopes and chronometers, poor weather conditions and a steamship strike.
Nevertheless their data demonstrated the validity of Relativity and garnered newspaper headlines across the world, catapulting Einstein to fame.
The definitive book on the experiments is Kennefick's No Shadow of a Doubt: The 1919 Eclipse That Confirmed Einstein’s Theory of Relativity. It's well worth a read. The BBC programme Einstein and Eddington is also a good account of the experiment and it's background. With David Tennant as Eddington...
Game use.
I see three main ways to inject this little element of science history into an AITAS game.
1. A mostly historical encounter.
The party arrives in one of the two observation locations and meets the teams, perhaps helping Eddington with his observations? Or at least to carry stuff. This strikes me as the perfect opportunity for Sixie to drag Peri along to witness Science being done.
2. There's something weird up there.
For a more fantastic theme, perhaps the pictures showed something weird. The stars photographed were the Hyades (because they were a notably a bright group of stars) which have been associated by Lovecraft with Hastur and Carcosa.
3. Meddling
Or is someone attempting to prevent the observations, for some reason? While this might delay the acceptance of Relativity it probably wouldn't have much long-term effect. Or is Eddington himself the target?
Comments? Suggestions? Ideas?
1. Without corrections for both Special Relativity (time flowing more slowing for objects in motion under angular acceleration) and General relativity (spacetime is less curved by the mass of the Earth at their orbital heights) the system with become inaccurate by around ten kilometres per day.
2. Frank Watson Dyson tends to be forgotten about in relation to the experiment, perhaps because his part was organisational and theoretical. He was Astronomer Royal and also originated the 'pips' time signal broadcast by the BBC in 1925.