Thank you very much, Steve, for this kind introduction and also explaining that this is not my day job.
And there and I does the health warning.
I am not a historian. All right. But what I want to do today is tell you a little bit, first of all,
about the firm of Howard Grubb in Dublin and then tie that in with the measurements that were made in 1919.
And you'll see some of the equipment from Rob's time that that proved to be very important for these particular measurements.
So I need to set the whole thing in context and.
That's it. That's it. So around the 1840s, 1850s in Ireland was a sort of golden era in astronomy.
What probably a lot of people don't realise is that actually Ireland, up to about the 1870s or so,
had not only the largest reflecting telescope in the world, that was the six foot, the so-called Avison of Parsons Town.
It was the the biggest reflector in the world, but it also had the largest refractor in the world in a place called Marguerite Castle in Sligo.
Now, of course, Ireland is not the best place when it comes to optical observing night.
Neither is Oxford. But you know, this was pre jetting off to La Palma or Hawaii,
etc. So it's understandable that they had to they had to based them at home, so to speak.
So this golden era of astronomy in Ireland then gave rise to an actual industry building telescopes.
And this man here, Thomas Grubb, was the first was the founder of the firm.
He initially started off believing not his business was making billiard tables.
And at that time, by the way, the billiard tables weren't slate billiard tables.
They were actually metal that were fashioned into as flat as a tabletop as possible.
But he started in that, but he had an interest in scientific instrumentation,
and so he started building telescopes and microscopes, etc. But although he he made telescopes,
for example, for the US Naval Observatory, a number of small telescopes around Europe,
he realised that telescope making was not a very steady business.
But you would get an order for a large telescope.
The firm would be going for a few months working on that and then the mightn't be in order for quite some time.
So he decided to go into another business which was actually making money or more precisely printing money.
He got the post in the bank of the Bank of Ireland, produced its own notes, rather like the Bank of England does at that time.
And he got the post with the recommendation of William Rowan Hamilton, noted mathematician and not sure you know,
that letter of reference from mathematician today would get you a job in the Bank of England, for example.
But maybe, maybe. But anyway, so that's how he got the job.
And he essentially passed on the business to his son, Howard Groep and Howard started actually doing a degree in Trinity College.
We actually never finished it, but he became very, very well known in instrument making circles and he made telescopes.
And I'll just show you few examples in the next few minutes for for institutions all around the world, including Vienna, for Melbourne, etc.
As I said, I'll show you some examples. But he also was involved with some telescopes in the states.
For example, if any of you ever go to the Lick Observatory, you'll see there's a rising floor in the observatory,
which was the solution for the problem of when you make a bigger and bigger refractor, of course.
And if you're looking at something which is low down on the horizon or even in 30 degrees or whatever,
then it gets very difficult for the observer to look through the eyepiece.
So he came up with the idea of the rising floor.
So hydraulically moving floor. And he also later in life, he was the person who developed the Marine periscope.
So it's difficult to kind of realise it now.
The inventor, by the way, of the modern submarine was a guy called Holland, John Holland, who was also from County Clare.
But he Holland tried to get the the British Army interested in submarines and they weren't particularly interested.
So he actually ended up over in the US.
Where his first source of funding was the Fenian Brotherhood.
Now I can imagine what what they intend to do with the first submarine,
but they actually ran out of money and he eventually sold the idea to the US Navy
and started building submarines and at which point British he got interested.
But the first submarines actually went around blind.
They had no periscope. They simply just went underwater, went a certain distance, hoping for the best, the particular direction.
But then Grupp invented the periscope in particular for a submarine, and that was extremely challenging business at the time to do that.
Anyway, at one point in his his firm, which is in a place called Rat Mines in Dublin, it had 400 people working on optics.
Here's an actual picture of his firm in rat minds.
This is with the opening of the new building. And you note the clear.
Health and safety. Cognisance, right?
Yes. And. Here's one of his famous telescopes, the great Melbourne Telescope.
So Melbourne, after the Gold Rush, had a lot of money.
This is back in sort of 1840 748, and they decided they were going to do the local government decided on a prestige
project which was to build the largest telescope in the Southern Hemisphere.
They had virtually no astronomers, by the way, but they decided to build the telescope anyway.
So Hargrove was commissioned it making the telescope.
And that was actually the last one.
Major telescope using Speculum Mirror. So you built using glass mirror after that, people started using glass and parks, etcetera.
And but that telescope, actually, there had been a number of reincarnations of that telescope.
And it was used up to about, I think about 15 years ago for the Metro Project, you know,
for searching for massive objects in the halo of our galaxy, which were causing gravitational deflection.
Gravitational lensing. So and then of course, there was the fire of Mount Stromlo and that telescope was destroyed.
But in fact, the Museum of Victoria is now in the process of restoring it.
Here's another one of his telescopes. This is the the largest refractor on mainland in Europe and Vienna.
And this was built also by Howard Grubb. And he built sort of half of the telescopes for the car to see.
The car to see was, in fact, the first survey.
I mean, we were talking about surveys last night, astronomical surveys.
And so this the car to see you from around the 1890s and it ran for quite a number of years was actually the first survey of the sky.
Obviously, it was a photographic survey and it involved a number of universities and observatories around the world,
including the Vatican Observatory. So that's why over here you see a group of nuns.
So back in 1895, 1900, they were actually doing the measurements on on plates.
Now, take that into consideration during your next survey and this telescope,
which maybe some of you might know because it was an Oxford at one point,
the Ratcliff telescope, some grubby construct that had ended up, of course, in Pretoria.
But it was initially in Oxford, and this was constructed by Hart Group.
Anyway, so let's start with the dust to give you some background about Hargrove himself.
But he was very not only an instrument maker, but he was very interested in astronomy itself.
Back in the 1900s, he organised an expedition to Spain to observe the kips there.
And this was an expedition that involved the Royal Irish Academy and the Royal Dublin Society.
So they they they duly headed off to Spain, initially was told an enormous number of people were going to go.
But then just around that period, there was problems with the Boer War, etc. and the net result of that was not so many people wanted to travel.
So anyway, they headed off to Spain. As you can see here, you have a 10th of a point.
Oh, there is one. I have one just here for.
I've got one. Steve Yeah, no problem, sir. You should have taken this out right at the beginning.
Yeah. So that's decided to die.
This one. Oh, this one?
Yeah. Okay, so let's see. Okay.
So it works very well. Alright. So here is actually the group in the senior in in in Spain, the travelled there for the 1900s of clips.
This is actually Hargrove himself.
This is a guy called Charles Jasper Jolly who was director of Dun Cinque Observatory, which is actually part of my own institute.
Now, this guy is his name is Wilson.
He did a lot of work on the sun and some of you may have heard of Wilson.
He was also made the first temperature measurement of the sun, and he came from a place near Dublin.
And what I thought was very interesting about this picture is that clearly Wilson,
W.E. Wilson thought, you know, he was going off to Spain and he would require his helmet.
All right. The deepest, darkest Spain. So whereas this is Rupert.
This is Rupert Grove, the son of Howard Grove.
And he has the more the modern idea of what going to Spain involves, but with the sort of straw hat, etc.
So you can see the cultural transition of the current man. So here you see them setting up the equipment for the 1900s eclipse.
You can see Wilson there in the background. And but this is the particular instrument that I want to draw your attention to.
So this is Jolie with the 24th photographic camera.
So here you see where the photographic plate would have gone. And you can just about see it peering over the edge here.
There was a see the start, which, of course, just takes the light from the sun.
It turns as the sun moves, essentially. Or is half of the race because of the law of law of reflection.
And so it then sends the light into this stationary tube, which has a lens at the front.
And the image is produced back here. So, of course, what they were trying to do was image the corona of the sun and which they duly did.
It was extremely, very good conditions. And this is actually an image from the 1900s eclipse,
which is actually in the raw in our academy that use this for an inch lens, which was 20 foot focal length.
And you can see here a number of prominences coming out of the sun.
Now, this picture, by the way, several people have asked me, wow, I didn't realise they had colour photography in 1900.
They didn't. These this was coloured afterwards. Right.
So just in case you're wondering that. But nevertheless, I think for 1900, you can see there is, you know, a very good quality.
Actually what I did at one point. I mean, as I said, this this particular eclipse well, eclipse is normally visible over a very long track.
And in this case, it was visible all the way from the US through places like Georgia, South Georgia, North Carolina to Spain, Portugal, Spain, etc.
So there are quite a few records of this eclipse and here you see a little sort of prominences here.
They're the same, more or less the same ones there in Spain. This is a couple of hours difference because it took time for the for the solar for
for the track of the eclipse to move across the Atlantic from the US over to Europe.
But you can see here that this is actually from the Smithsonian Archive.
They had a station at North Carolina and a guy called Thomas Smiley, who is the photographer for the Smithsonian,
actually recorded what's probably the first photograph of you recorded CME because you can see suddenly this,
you know, the foot points here have developed into a major problems here, which has been injected into the corona.
So we then kind of fast forwards a number of years.
And as you know, and as Steve has already mentioned, towards the end of 1915,
Einstein came up with this prediction that for the deflection of starlight when an eclipse occurs.
And he predicted basically that, as you can see from here, the light of the of a star,
which, of course, passes close to the sun, is bent, is altered in such a fashion.
As you can see, I think from this diagram, the stars appear to move away from the sun itself compared to their normal position.
So in the absence of the sun, and this is purely an effect of gravitational deflection.
And he predicted the maximum amount will be 1.75 arcseconds and it scales with distance away from the sun so
that to be the value would get for a star just at the surface of the sun or appearing to be at the surface.
And of course, if you go to twice as far away, it's only half of that value.
So that was the prediction in 1915.
Now testing that prediction, there was there was a problem in trying to test the prediction, which is, of course, the First World War.
And so it wasn't feasible to mount an eclipse expedition.
So but back in 1917 then there was a this is a great title.
So the Royal Astronomical Society and the Royal Society came together to form what was called a joint permanent eclipse committee.
No, I still don't understand that title. No clips is permanent and hopefully no committee is permanent.
So although I have my doubts in some cases, but anyway, they came together.
They came up with this idea of an expedition, but they had a basic problem.
And the basic problem was this that most of the Royal Society's Instrumentation and Royal
Astronomical Society's instrumentation had been sent off to an eclipse in Russia in 1914.
And then what happened was, of course, the First World War broke out, so they didn't get the equipment back.
The astronomers got back, but the equipment was held up, of course, at the end of the war.
Then you had the Bolshevik Revolution and they still didn't get their equipment back.
In fact, they didn't get it back until the ninth, I think around 1925.
So they were stuck and they asked to the Royal Irish Academy if they could assist by
giving them some equipment from the Royal Irish Academy jus for previous eclipses.
So there was actually a particular priest whose name was Courtney.
Courtney. He was a stoney horse, which is in northern England, the school there.
But he had associations with the Royal Academy and realised the potential of the equipment that had already been there.
So they asked the Rowan Irish Academy for this equipment and that was duly of course a loan to them.
So the idea behind the Eclipse expeditions was that there were actually two expeditions because chances were that maybe one of the,
you know, might be cloudy. So the two sites that were chosen were kept off the west coast of Africa, but also a place called Sobral in Brazil.
So those are the two sites and they're in the diagram.
You can actually see the track of the eclipse itself.
And it was regarded as an extremely favourable eclipse for measuring the deflection of starlight.
Why? Because the sun was actually in a cluster behind each cluster, as you can see up here.
We have used this one. You have.
This is the tourist bowl. This is Aldebaran.
This to be here. And this is the Hyades all all these stars here and up here at Hyades cluster.
So there was a lot of stars. The sun was in a sort of perfect position because you could use a lot of these stars for reference purposes.
And in particular, what I just want to point out is this star capital, which was the it's a double.
It's a real double. It's not just an optical double. And capital was, you know, essentially the nearest star to the sun or nearest double star.
So the idea was to use the sun, other stars in the hyades to make measurements of the gravitational deflection of stars.
Normally, the sun isn't in such a such a good position from the point of view of getting bright stars.
So the eclipse. The Eclipse parties went out at two sets of instrumentation, by the way, and that actually involved Oxford as well.
It was a 13 inch crop lens fed by a 16 inch sealer start from Oxford, and that was the actual instrument used and kept.
And it's so proud to use something very, very similar.
A 13 inch crop lens as well, said by a six inch seedless tart from Greenwich.
And in addition, the four inch lens that I mentioned earlier on from the 1900s are clips and an eight inch
steel stuffed so that but the latter were essentially just the backup instrumentation.
So this is the instrumentation they got from the Royal Arch Patent.
The intention really was to make the, shall we say, the serious measurements using the 13 inch lenses and 16 inch sealed stones.
And this particular man Andrew Crumlin was the leader of the expedition to so bravely was from County County Antrim.
So he actually led the expedition out to Sobral and then Arthur Eddington led the one to.
So that was fine. They actually went took them about a month.
By the way, if you ever get a chance to read one of these papers about the Eclipse expeditions of the past to read more like travelogues,
they describe the boats that they got the the how, you know, the local natives not necessarily in wonderful tone sometimes, by the way.
But it is really worth reading just to see how how things have changed.
So this is actually the so brown eclipse equipment. And in fact, the equipment over here, this is the the 16 inch seals.
This is the 13 inch group lens. But this is the backup equipment.
This is a four inch lens. And the agency to start.
So just in case anything went wrong. And of course it did.
Right. So that was Brazil.
And the results from this World Cup is they got a few images, but unfortunately it was cloudy and so they didn't get an awful lot.
So brown, the large scene was not suffered from sole reason because the sun was had been shining for a couple of days.
So that was the downside of the beautiful weather that they had in Brazil.
And as a result of that, the 16 and see the start produced distorted images.
But the four inch lens. And the agency.
The start actually produced the best results of the law, and in fact, were the results chosen by Addington in the end as the definitive answers.
Right. And what they found was that affection for the limit of son.
Because obviously they had to extrapolate it to, you know, using the one overall law of 1.98 plus or -0.18 arcseconds.
And in fact, these plates were remeasured in 1979 by Harvey, and he got 1.9 plus or -0.11.
So pretty much the same result, confirming that Eddington and Dyson had done their had done the proper job.
And of course that's with more modern instrumentation at the time.
And this is actually I literally did not have this up until about two days ago.
Right. There's a there's a problem, which was that the 1919 eclipse plates from the Royal Greenwich Observatory went missing.
All of them. Right. And this is actually from the clandestine border, the State Observatory in Heidelberg.
Max Wolff was the director, Dan, at the time, and he was sent by Eddington a copy of one of the printed images.
Right. So if you go on the Web and look for the 1919 eclipse and look for images of the eclipse, they're pretty lousy.
And the reason is to just scans from old books. At the time, there are no proper scanned 19, 19 plates.
Right. So we did come across this one.
But in turn recently, it turns out that the The Greenwich Observer, while the Royal Greenwich Observatory at the Royal Observatory at Greenwich,
which is now run by the Maritime Institute, apparently they held on to three plates,
which hopefully now we'll be able to get in the next few weeks and get them scanned as well.
But otherwise, the the the Royal Greenwich Observatory, the main set of Royal Greenwich Observatory plates, should now be in the Bodleian.
But they're not. They're missing. And this is known by its that they're missing.
But anyway, this is just to show you one of the print cap plates and these very faint stars here, very difficult to make measurements on.
This is capital. Just to give you an idea of the quality of the plates from the time and this is, of course, the name of the sun.
So as you can see, this is Dyson's paper and Edison's paper measuring the deflection of starlight.
They give the value here. I gave you the error is wrong.
1.94.
But as you can see in summarising the results of the two expedition, the greatest weight must be awarded to those obtained by the four inch lenses.
So brown and observations seem to stop. So that's.
So that was actually the source of the measurements. I like this bit from the newspaper at the time.
I think it's really good. Right.
So this is they had Dyson and Eddington made the announcement that Einstein was correct at the Royal Society in November 1919.
And I like this bit. The subject was a lively topic of conversation in the House of Commons yesterday.
This is Joseph L'Amour for Cambridge University.
On arriving at the lecture before the Royal Astronomical Society last evening said he he'd been
besieged by inquiries as to whether Newton had been cast down and Cambridge done in Cambridge,
a clearly being done in on this occasion.
So, of course, Eddington became very famous on the front of Time magazine at the time and spent quite a bit of time with Einstein as well.
And so that was fine. But there was the kind of rumour that this equipment had actually gone back to Ireland at some point.
So I decided to follow up on this because I'd become interested in her brother and I was trying to trace where this equipment had gone.
Anyway, long story short, through the archives in the Royal Society and in the Royal Astronomical Society,
I basically and the Royal Lodge Academy basically found out that the equipment had been sent back to Ireland in 1947.
At the foundation of my own institution. But the Institute found a way to prevent studies.
Was well, the first section of it, which was theoretical physics, was opened up during the Second World War.
And so people like Erwin Schrödinger ended up in Ireland.
And because the President of Ireland's at the time realised there was a lot of scholars and
fleeing the Nazis and he decided to set up the institute for them to come to during the war.
Anyway, so I actually found and in turn the sea Lestat and the 20 foot lens buried.
Well, in one case the instrument was buried in the basement amongst many other items in the observatory.
Quite, quite a lot of stuff in empty territory. But in addition to see, the Star turned out to be in the garage of an X technician.
And at some point it been sent off for him to do a bit of restoration work on it, you know.
But anyway, we found it. It has.
The nice thing about Grub equipment was that grub equipment has numbers on sort of boiler plate numbers.
And fortunately, a well, grub grub, by the way, moved.
After the First World War they moved to Newcastle and became persons who of course built telescopes.
Up until the, up until the seventies persons when it closed,
then they a lot of a lot of old stuff was being dumped and they had of the optics
unit actually rescued some books from Dublin that were actually in a skip.
And these were passed on to me because some retired.
I was interested in Graham and turned out one of his books actually had Graham's numbers and where the instruments had been.
So from the the number. Then I realised this was the actual seal of state and the lands had been used.
And so brown, apart from the fact it was known the lens was 1946 inches focal length and you know, etc.
So it was pretty, pretty definitive. Now hopefully that's the work.
Okay. So this is the restored scene to start.
So Madonna Observatory with the CAA in Clay did did a job on that.
University College London restored the the Einstein hands to four inch lens.
When I got this video from from the CAA a couple of weeks ago, I thought there was something wrong with my hard drive.
And it turned out it was actually the noise of the governors and the see the stuff working for the first time in 37 years.
So. So that's restored. It's now back in Dublin and in fact, we're kind of going to unveil is next week because we're celebrating,
as Steve said, 100 years since Einstein before the general theory of relativity.
So just to just to recap, it's this instrument here, which was the backup equipment which is now being found.
So that was great and wonderful.
But then that turned out to be a kind of twist to the story, which turned out to be very interesting.
Because I realised something about the eclipses.
So as a coastal thing you all know earth goes round the sun in 365 and a quarter days, more or less.
Right. This is why we have the the leap year.
And it means, for example, the solstice.
The winter solstice. The summer solstice actually shifts over over time.
And then, of course, you insert a leap year and then it brings it back.
For example, in my the classic example I like Steve mentioned, I work a volt on some work in our view astronomy.
And there's a site near Ireland called Newgrange which is actually aligned.
It's a very long passage, but it was aligned with the winter solstice, but the winter solstice four or 5000 years ago,
I mean, the carving dating of the scientists, 3200 or so B.C. And it's perfectly aligned for the for the winter solstice.
And every winter solstice, you know, there's a small select party end up inside its main chamber to see the sun coming in.
And I'm sort of wheeled up there on the 21st of December for this event.
And, you know, there's some notable politicians or visiting dignitaries and whatever.
But once every four years, actually on the 22nd that I'm told to keep my mouth shut.
But then the following day, I really enjoy going up.
And then there's some members of the public are allowed in. And I'd say this is the real solstice, not yesterday.
Right. So you can see the pattern here.
So basically, this is the this is of course, this is just the summer solstice, but it's the same thing applies.
And what you have then is this oscillation, depending upon the leap year effect.
Right. But in addition, as you also know, 365 and a quarter isn't quite right in Julian calendar.
And there's another correction depending upon whether the first two digits of the century are divisible or not to be divisible by four.
And so depending upon that, you either insert and and make them leap year or not, as the case may be.
So that's why this particular pattern here. Okay, so that's fine.
So you get this kind of drift. But what I realised was one eclipse, the 1900s eclipse that occurred in 28th May 1900 and the second eclipse,
which was the one that was used in Sobral and and kept, was the 29th of May.
Right. But one was in the morning.
The other was in the afternoon. And one, you know, it was out of step as regards to be pure effect.
So it turns out if you put them both into a planetarium program, for example, you'll see this.
The top one is made of 28, 1900s eclipse.
There's capital. All right.
And that was the one in Spain that grob one looked at and reported.
This is so brown. Eclipse made 29th. There's capital.
Of course, it's upside down. Remember, Brazil is in the southern hemisphere, right?
That's why. Otherwise, within one arc minute, the sun is in exactly the same place.
It's just a coincidence. It's nothing to do, by the way, with Saracens, etc., during different serial cycles.
It was just pure coincidence. So what we're saying is that the same equipment had been used to observe the same eclipse.
Right. Essentially the same. The other advantage of 1900 clips, by the way, is, of course, the sun goes through cycles.
The 11 year the 11 year cycles are more probably 22 year, but 11 year cycles in terms of criminal activity.
And 1900 was less active than 1919.
So there were advantages to 1900 versus 1919.
So let's just sum it up. The sun was in exactly the same position.
The sky, within a minute or two of our solar activity was lower in 1900 than it was in 1919.
The same four inch lens and sills that was used to image the sun in the same part of the sky.
Just coincidences.
But it begs the obvious question why didn't anybody really think of doing using photography of historical data to try and measure this deflection?
And there was a very good reason why people were doing photography.
They were looking for a planet called Vulcan.
Right. So, Vulkan, let me explain that.
And I think many of you know, you know, the history of general relativity.
There is an effect through, for example, the advancement of the perihelion of mercury.
And the initial explanation for this, of course, we now know, of course, is just a general atavistic effect.
But the initial explanation was in terms of a possible planet that was inside the orbit of Mercury and was therefore very,
very difficult to see it even being given a name, Vulcan.
And people started to search for Vulcan. Right.
It's kind of ironic that the plates from the searching for Vulcan, which was purely erroneous due to the fans of the perihelion of Mercury,
turns out to be of interest in terms of measuring the fraction of starlight.
So that's the reason why they looked at it. And so then started looking at a number of plates from around the world from 1900.
This is, for example, the shabu observatory's Oakland near San Francisco.
And there's, as you can see, their capital 1900.
Almost identical position as the 1919 model. Okay.
But there are similar plates, Miller says, in Lake Observatory.
There's a set in the Royal Observatory in Edinburgh as well.
Okay. And so they all had gone off to observe this 1900s eclipse.
But there was a suggestion to use historical plates.
And the first person to suggest it was this man here on the left, Irwin Freundlich, or Irwin Finley Freundlich,
as he sometimes called because he had a Scottish mother and a German German father, and he was a friend of Einstein's.
And so back in around 1914, just before the war broke out, Einstein had predicted the deflection of starlight,
a sort of first approximation, which we now call a sort of Newtonian approximation.
It turns out, of course, to be wrong by a factor of two.
But Freundlich had suggested using historical material to do this deflection of starlight measurement.
Now, Freundlich had a couple of problems. One was he wasn't really a very practical observer.
He was more of a theoretician. The second thing was that Struve, who was director, didn't believe in Einstein at all.
I knew it. No, no comment. And so basically, he was not supported in this pursuit.
He did try and go off to the 1914 eclipse and make measurements for that in Russia,
not in the same science as the Royal Society and Royal Astronomical Society.
And he ended up being interned, I think, somewhere around Serbia on the way to the eclipse.
So anyway, he got out, but he he rose, in fact, to a number of observatories around the world, including Lech and the Royal Greenwich Observatory.
To Dyson. This man here on the right, Curtis, tried to measure some historical plates.
And then there was also an eclipse in 1917 in the US, and he actually did some work on that, but he was regarded as being well.
Wallace Campbell, who is director of Lick, taught Curtis was a bit sloppy, by the way.
Curtis. Some of you may have heard of the M 87 jet, so he was the guy who discovered the 87 jet.
Photographically, he had no idea what it was, of course, at the time in the Aegean connection, but he actually discovered the jet from 87.
So and the other complication then was that the U.S. entered the war around that time, and Curtis decided to go off the air with the U.S. military.
So his work wasn't really completed and it wasn't done very, very well.
Now, Dyson. As I said, Freundlich suggested to Dyson back in 1914 not to use historical material.
I only know that because letters that are in the Lake Observatory Archive, where Freundlich writes to Campbell and says,
I've contacted, you know, Dyson and suggested using historical material, but and that that he promised me help.
Now, of course, when the war broke out, maybe things were a bit different at that point.
Anyway, he never did. There's no correspondence in the audio corresponding to this.
Then Dyson in 1917.
Actually starts getting actively interested in measuring your general activity.
Deflection Starlight and he prints in the monthly notices of the Royal Astronomical Society, a two page paper.
Page one is measurements. Some historical measurements that he made on some plates from Tunisia that were in the audio archive.
Page two I'm page one, by the way. He says, Oh, this method will clearly work.
Right. You can see they're in black and white to page pages. This method will clearly work.
But unfortunately, I can only measure two stars on this plate.
So obviously that's not no good for measuring the reflections starlight.
But the astral graphs will, will, will do the job.
And then on page two. There is this eclipse coming up on the 29th of May 1919.
We have to mount an expedition to to to measure Dr. Einstein's effect.
And that's it. He shows a sort of diagram of where the stars will be in 1919 and nothing more.
Just the two pages. So that's actually the diagram where he's made the his initial measurements.
But then in the process of looking into this, I realised that.
Dyson. Only honey had three sets of plates to look at from the astronauts.
From eclipses. It ones from, as I mentioned here from Tunisia.
That's the one he actually measured, measured on this two page paper.
He had the plates from Sumatra, which wasn't very good in 1901.
And then, to my surprise, I discovered he'd been at the 1900s of kids in Portugal.
Right. So we had those sets of plates as well. And so he was at a place called over in Portugal that would have got the eclipse first as the
eclipse crossed the Atlantic before Rob and his party would have gotten the eclipse in Spain.
And here's the actually pictures of the party from the Bodleian Library, which was of course,
then it was the Royal Greenwich Observatory's Library, which has been moved recently to the Bodleian.
So this is the party in Portugal preparing for the eclipse.
This man here is Kristie, who is the Astronomer Royal at the time.
And his next in command was actually.
And then I looked at the bottles and plates and there's.
Capital is the limit to some here.
So you can see the. Capital there.
Now, these plates have only got a couple of stars on them,
so it may not have been possible for Dyson to have done it any better than perhaps the ones from S-max.
Maybe a bit better because there are two or three other stars.
But he could have used the eclipse planes from Central Observatory, Greenwich or Lake or whatever at the time.
Now. Why didn't he? I don't know. Well, to 100% accuracy, but I have my suspicions.
I think it's the best way of putting it. So the problem was World War One.
Eddington was a conscientious objector. He said he would go to prison first before serving in the army.
The British army. 1916,
conscription had been introduced and in the UK actually it was also one of the contributing factors to the revolution
in Ireland in 1916 was the fact that it looked like Britain was going to enforce conscription in Ireland.
So by 1917, Edington was in an awful lot of trouble in terms of defending himself from not going to the war and.
Dyson and Eddington went to Cambridge together.
In 1918. Eddington reached a stage where Eddington had to go in front of a military tribunal.
To explain why he was not serving in the Army. He said what he had to do.
And this was also it was the supporting letters from from Dyson that you would have to go off and observe the eclipse to test Einstein's
theory of relativity and that it was crucial that he go and that there would not be another eclipse like this for a thousand years.
No, I have checked. And yes, he actually was right, apart from I think to what there was one, which is just off the Falkland Islands.
In the 1930s where the hides were recovered.
Right. But that would have been at sea. So, yes, we will allow not one.
And in fact, yes, there's about a thousand years to the next one.
Now you have to believe he never looked back 17 years, or it didn't cross Dyson's mind to look back 17 years.
I just don't believe that. But, you know, that's so open to interpretation, right?
So anyway, Dyson insisted I don't and would have to lead this expedition, even though he was a theorist, by the way, in his first year in Cambridge.
If you read the stories about Eddington, he caused disaster in the first year lapse,
and they suggest that you go off and do theory, which was a good idea.
But then you have to ask yourself why? Okay.
So of course, he had a clear interest in general relativity. But, you know, Andrew Cromwell and who was an observer, was sent off for, you know, so.
BROWN Why didn't you pick somebody else from there or do you write?
Andrew comment and by the way, never put his name to the paper. I don't know why I'm so.
Anyway, Eddington went off to to observe the eclipse.
And of course the results were published.
And as I said, the results favoured Einstein's theory. So despite the fact that Dyson had these three sets of plates he picked.
The worst, really one of the worst ones of the three.
Well, you know, it was kind of cloudy, so not much you could do with that. Right.
And I still have no idea why, apart from the fact that I what I suggest was he realised from the 1900s eclipse.
Plates and the you know, the fact that he made measurements on that, that the technique would work.
And that may have also inspired them to realise about the 1919 eclipse.
In the whole sort of trying to sort out the problem with Eddington as well.
So there was always a claim, by the way, by Chandrasekhar that the only reason why Eddington was went to this eclipse was simply to avoid war.
And a lot of people thought, well, because this was a well known dispute between Chandrasekhar and Eddington,
that maybe it was a touch of sour grapes over all of this.
But that may well have been something in this. So okay.
So just to summarise, the actual equipment which had been used and proved crucial in the 1919 eclipse measurements has been found, has been restored.
That's quite timely with next week being 100 years since Einstein proposed his general theory of relativity.
The quip by a quirk of just a fluke chance.
It turns out that same equipment had been used to observe an identical eclipse.
19 years before us. And it does look like Dyson, I suppose to kind interpretation of this.
Dyson probably realised that he would muddy the waters.
If he'd had talked about an identical eclipse which had occurred.
You know, 19 years beforehand that would not have served Eddington's case.
Certainly he did not. Or he was extremely stupid.
Right. So we've actually I mean,
we've had a look at some of these plates to understand virtue and height in Heidelberg
now is gathering all these plates together from different parts of the world.
And we're going to remeasure them. And actually what our intention is that we make them available online for students of physics in 2016 to
actually measure the deflection of starlight from themselves with the 1900 plates and the 1919 plates,
hopefully the ones in the audio are still alive. Okay, so thank you very much.