Archive for 1919 Eclipse Expeditions

The Eddington Eclipse Expeditions and Astronomy Ireland

Posted in History, Talks and Reviews, The Universe and Stuff with tags , , , , , , on December 10, 2019 by telescoper

After a full shift during the day at Maynooth University, yesterday evening I made my way into Dublin to give a talk to a very large audience in the famous Schrödinger Lecture Theatre in Trinity College, Dublin, an event organized by Astronomy Ireland. I have given a number of talks on the topic of the 1919 Eclipse Expeditions during this centenary year, but I think this one had the biggest audience! We adjourned to a local pub for a drink afterwards before I dashed off to get the last train back to Maynooth.

Here are the slides I used during the talk:

This time there was an important addition to my usual talk, courtesy of Professor Peter Gallagher of DIAS. He brought along the actual 4″ object glass used in the expedition to Sobral (Brazil) in 1919. I have previously only shown a picture of it. The appearance of the actual lens drew a spontaneous round of applause from the audience, and I have to admit it was a remarkable feeling to hold a little piece of history in my hand!

Obviously I was careful not to drop this item. It is on permanent display in Dunsink Observatory, by the way, if you want to see it yourself. I hope it made its way back here safely!

After the talk was over I was chatting to a couple of members of the audience when Peter Gallagher took this nice picture actually through the lens:

Picture Credit: Peter Gallagher

I look rather old in this picture. Obviously a trick of the lens.

How Ireland Made Einstein Famous

Posted in History, Talks and Reviews, The Universe and Stuff with tags , on December 6, 2019 by telescoper

Before I depart for the weekend I thought I’d mention that I’m giving a talk on Monday evening (9th December) at 8pm in the Physics Building at Trinity College Dublin. The talk is followed by a reception in the Lombard Inn. Part of the advert is shown above but you can read more details at the Astronomy Ireland website.

If you’re around in Dublin on Monday then maybe I’ll see you there!

Astronomical Archaeology and the 1919 Eclipse Expeditions

Posted in History with tags , , , on November 21, 2019 by telescoper

Regular readers of this blog (Sid and Doris Bonkers) will know that in the past year I’ve written some articles and given some talks this year about the total solar eclipse on May 29 1919 at which an experiment was performed to test Einstein’s theory of general relativity.

I recently found out about another artefact of that expedition which has turned up in Denmark. More specifically it was discovered in the basement under the Niels Bohr Institute building on Juliane Maries Vej in Copenhagen. In the archive that is situated there they found records of astronomical observations that go more than 120 years back in time recorded on thin glass photographic plates. You can read more about these discoveries here.

Anyway, one of the plates that turned up in Copenhagen shows this image:

A copy of one of the Sobral Eclipse plates

This image is a low-resolution version from a high-resolution scan of the plate (kindly sent to me by Johan Fynbo) concerned which I believe to be a contact copy (rather than an original) of one of the plates made by Andrew Crommelin’s team in Sobral in 1919. I know that a number of such copies were made in the aftermath of the experiment and similar plates have turned up in several locations.

If you look carefully you can see a number of dark rings (one of them quite clear because of the contrast with the solar corona).  These rings surround the stars used to measure the gravitational deflection of light by the sun; you can see the others more clearly if you click on the image to make it larger.

I think this plate illustrates one of the difficulties of this measurement: the gravitational deflection is larger for lines of sight close to the Sun, but the corona is likely to be in the way precisely for those same stars.

 

The Danger to Science from Hype

Posted in The Universe and Stuff with tags , , , , , , , on October 5, 2019 by telescoper

I came across an article in the Irish Times this morning entitled `Hyping research runs risk of devaluing science‘. That piece is directly aimed at medical science and the distressing tendency of some researchers in that field to make extravagant claims about `miracle cures’ that turn out to be a very long way from being scientifically tested. The combination of that article, yesterday’s blog post, and the fact that this year I’ve been speaking and writing a lot about the 1919 Eclipse expedition reminded me that I ended a book I wrote in 1998 with a discussion of the dangers to science of researchers being far too certain  and giving the impression that they are members of some sort priesthood that thinks it deals in absolute truths.

I decided to post the last few paragraphs of that book here because they talk about the responsibility scientists have to be honest about the limitations of their research and the uncertainties that surround any new discovery. Science has done great things for humanity, but it is fallible. Too many scientists are too certain about things that are far from proven. This can be damaging to science itself, as well as to the public perception of it. Bandwagons proliferate, stifling original ideas and leading to the construction of self-serving cartels. This is a fertile environment for conspiracy theories to flourish.

To my mind the thing  that really separates science from religion is that science is an investigative process, not a collection of truths. Each answer simply opens up more questions.  The public tends to see science as a collection of “facts” rather than a process of investigation. The scientific method has taught us a great deal about the way our Universe works, not through the exercise of blind faith but through the painstaking interplay of theory, experiment and observation.

This is what I wrote in 1998:

Science does not deal with ‘rights’ and ‘wrongs’. It deals instead with descriptions of reality that are either ‘useful’ or ‘not useful’. Newton’s theory of gravity was not shown to be ‘wrong’ by the eclipse expedition. It was merely shown that there were some phenomena it could not describe, and for which a more sophisticated theory was required. But Newton’s theory still yields perfectly reliable predictions in many situations, including, for example, the timing of total solar eclipses. When a theory is shown to be useful in a wide range of situations, it becomes part of our standard model of the world. But this doesn’t make it true, because we will never know whether future experiments may supersede it. It may well be the case that physical situations will be found where general relativity is supplanted by another theory of gravity. Indeed, physicists already know that Einstein’s theory breaks down when matter is so dense that quantum effects become important. Einstein himself realised that this would probably happen to his theory.

Putting together the material for this book, I was struck by the many parallels between the events of 1919 and coverage of similar topics in the newspapers of 1999. One of the hot topics for the media in January 1999, for example, has been the discovery by an international team of astronomers that distant exploding stars called supernovae are much fainter than had been predicted. To cut a long story short, this means that these objects are thought to be much further away than expected. The inference then is that not only is the Universe expanding, but it is doing so at a faster and faster rate as time passes. In other words, the Universe is accelerating. The only way that modern theories can account for this acceleration is to suggest that there is an additional source of energy pervading the very vacuum of space. These observations therefore hold profound implications for fundamental physics.

As always seems to be the case, the press present these observations as bald facts. As an astrophysicist, I know very well that they are far from unchallenged by the astronomical community. Lively debates about these results occur regularly at scientific meetings, and their status is far from established. In fact, only a year or two ago, precisely the same team was arguing for exactly the opposite conclusion based on their earlier data. But the media don’t seem to like representing science the way it actually is, as an arena in which ideas are vigorously debated and each result is presented with caveats and careful analysis of possible error. They prefer instead to portray scientists as priests, laying down the law without equivocation. The more esoteric the theory, the further it is beyond the grasp of the non-specialist, the more exalted is the priest. It is not that the public want to know – they want not to know but to believe.

Things seem to have been the same in 1919. Although the results from Sobral and Principe had then not received independent confirmation from other experiments, just as the new supernova experiments have not, they were still presented to the public at large as being definitive proof of something very profound. That the eclipse measurements later received confirmation is not the point. This kind of reporting can elevate scientists, at least temporarily, to the priesthood, but does nothing to bridge the ever-widening gap between what scientists do and what the public think they do.

As we enter a new Millennium, science continues to expand into areas still further beyond the comprehension of the general public. Particle physicists want to understand the structure of matter on tinier and tinier scales of length and time. Astronomers want to know how stars, galaxies  and life itself came into being. But not only is the theoretical ambition of science getting bigger. Experimental tests of modern particle theories require methods capable of probing objects a tiny fraction of the size of the nucleus of an atom. With devices such as the Hubble Space Telescope, astronomers can gather light that comes from sources so distant that it has taken most of the age of the Universe to reach us from them. But extending these experimental methods still further will require yet more money to be spent. At the same time that science reaches further and further beyond the general public, the more it relies on their taxes.

Many modern scientists themselves play a dangerous game with the truth, pushing their results one-sidedly into the media as part of the cut-throat battle for a share of scarce research funding. There may be short-term rewards, in grants and TV appearances, but in the long run the impact on the relationship between science and society can only be bad. The public responded to Einstein with unqualified admiration, but Big Science later gave the world nuclear weapons. The distorted image of scientist-as-priest is likely to lead only to alienation and further loss of public respect. Science is not a religion, and should not pretend to be one.

PS. You will note that I was voicing doubts about the interpretation of the early results from supernovae  in 1998 that suggested the universe might be accelerating and that dark energy might be the reason for its behaviour. Although more evidence supporting this interpretation has since emerged from WMAP and other sources, I remain skeptical that we cosmologists are on the right track about this. Don’t get me wrong – I think the standard cosmological model is the best working hypothesis we have – I just think we’re probably missing some important pieces of the puzzle. I may of course be wrong in this but, then again, so might everyone.

 

 

 

Breakthroughs, Beermats and the Bending of Light

Posted in Biographical, The Universe and Stuff with tags , , , , on September 6, 2019 by telescoper

I found out on the way home from Armagh yesterday that this year’s Breakthrough Prize in Fundamental Physics (worth $3,000,000) has been awarded to the team behind the Event Horizon Telescope which was featured in newspaper and magazines around the world in April this year and which I blogged about here. There are 347 members of the team so it amounts to an average of less than $9000 per person, but let me offer them all my sincerest congratulations!

Coincidentally, just before my talk at INAM2019 yesterday I noticed that the Armagh Observatory and Planetarium stocks these items:

I’m not sure they are intended to be used as beer mats but that’s what they look like! Anyway, I picked one up and showed it at the end of my talk. I was talking about the 1919 eclipse expeditions, which I have done rather a lot these days, and finished up by mentioning that the events of a hundred years ago ushered in a century of developments in relativistic astrophysics, including gravitational lensing, gravitational waves and of course the Event Horizon Telescope.

If you’re interested here are the slides I used for this (short) talk:

Special 1919 Eclipse Centenary Offer!

Posted in History with tags , on June 13, 2019 by telescoper

A little later than planned, a paper what I wrote for Contemporary Physics to commemorate the centenary of the 1919 Eclipse Expeditions has now appeared online. The print edition will be available in due course.

Here is the abstract:

Unfortunately the paper is behind a paywall, but as a special dispensation I am to offer FIFTY free downloads of the paper to friends, colleagues and random people on the internet.

If you’d like to download a FREE copy of the PDF of the paper A revolution in science: the eclipse expeditions of 1919 then you may do so by clicking this link. How’s that for clickbait?

UPDATE: the free copies have now all gone so I removed the link.

To be honest I’m not sure what stops you sending the PDF to anyone else, but apparently those are the rules…

Lights all askew in the Heavens – the 1919 Eclipse Expeditions (Updated)

Posted in History, Talks and Reviews, The Universe and Stuff with tags , , , , , on June 3, 2019 by telescoper

Here is a video of my talk at the Open Meeting of the Royal Astronomical Society on April 12 2019. Was it really so long ago?

You can find the slides here: