Archive for November, 2015

Away Days

Posted in Biographical, Brighton on November 30, 2015 by telescoper

No time to blog today as I am at yet another Awayday. In fact I will be Away for Two Days.

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Can anyone name my location (in the photograph above)?

Einstein’s Legacy

Posted in The Universe and Stuff with tags , , , , , , , on November 29, 2015 by telescoper

Yesterday I braved the inclement weather and the perils of weekend travel on Southern Trains to visit Queen Mary College, in the East End of London, for the following event:

GR100

I used to work at  Queen Mary, but haven’t been back for a while. The college and environs have been smartened up quite a lot since I used to be there, as seems to be the case for the East End generally. I doubt if I could afford to live there now!

Owing to a little local difficulty which I won’t go into, I was running a bit late so I missed the morning session. I did, however, arrive in time to see my former colleague Bangalore Sathyaprakash from Cardiff talking about gravitational waves, Jim Hough from Glasgow talking about experimental gravity – including gravitational waves but also talking about the puzzling state of affairs over “Big G” – and Pedro Ferreira from Oxford whose talk on “Cosmology for the 21st Century” gave an enjoyable historical perspective on recent developments.

The talks were held in the Great Hall in the People’s Palace on Mile End Road, a large venue that was pretty full all afternoon. I’m not sure whether it was the District/Hammersmith & City Line or the Central Line (or both) that provided the atmospheric sound effects, especially when Jim Hough described the problems of dealing with seismic noise in gravitational experiments and a train rumbled underneath right on cue.

UPDATE: Thanks to Bryn’s comment (below) I looked at a map: the Central Line goes well to the North whereas the District and Hammersmith & City Line go directly under the main buildings adjacent to Mile End Road.

Under-QM

Anyway, the venue was even fuller for the evening session, kicked off by my former PhD supervisor, John Barrow:

Einstein's Legacy

This session was aimed at a more popular audience and was attended by more than a few A-level students. John’s talk was very nice, taking us through all the various cosmological models that have been developed based on Einstein’s theory of General Relativity.

Finally, topping the bill, was Sir Roger Penrose whose talk was engagingly lo-tech in terms of visual aids but aimed at quite a high level. His use of hand-drawn transparencies was very old-school, but a useful side-effect was that he conveyed very effectively how entropy always increases with time.

Penrose covered some really interesting material related to black holes and cosmology, especially to do with gravitational entropy, but my heart sank when he tried at the end to resurrect his discredited “Circles in the Sky” idea. I’m not sure how much the A-level students took from his talk, but I found it very entertaining.

The conference carries on today, but I couldn’t attend the Sunday session owing to pressure of work. Which I should be doing now!

P.S. I’ll say it before anyone else does: yes, all the speakers I heard were male, as indeed were the two I missed in the morning. I gather there was one cancellation  of a female speaker (Alessandra Buonanno), for whom Sathya stood in.  But still.

 

Browser Speeds

Posted in Uncategorized on November 27, 2015 by telescoper

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Why is General Relativity so difficult?

Posted in The Universe and Stuff with tags , , on November 26, 2015 by telescoper

Just a brief post following yesterday’s centenary of General Relativity, after which somebody asked me what is so difficult about the theory. I had two answers to that, one mathematical and one conceptual.

einstein-equation1

The Field Equations of General Relativity are written above. In the notation used they don’t look all that scary, but they are more complicated than they look. For a start it looks like there is only one equation, but the subscripts μ and ν can each take four values (usually 0, 1, 2 or 3), each value standing for one of the dimensions of four-dimensional space time. It therefore looks likes there are actually 16 equations. However, the equations are the same if you swap μ  and ν around. This means that there are “only” ten independent equations. The terms on the left hand side are the components of the Einstein Tensor which expresses the effect of gravity through the curvature of space time and the right hand side describes the energy and momentum of “stuff”, prefaced by some familiar constants.

The Einstein Tensor is made up of lots of partial derivatives of another tensor called the metric tensor (which describes the geometry of space time), which relates, through the Field Equations, to how matter and energy are distributed and how these components move and interact. The ten equations that need to be solved simultaneously are second-order non-linear partial different equations. This is to be compared with the case of Newtonian gravity in which only ordinary different equations are involved.

Problems in Newtonian mechanics can be difficult enough to solve but the much greater mathematical complexity in General Relativity means that problems in GR can only be solved in cases of very special symmetry, in which the number of independent equations can be reduced dramatically.

So that’s why it’s difficult mathematically. As for the conceptual problem it’s that most people (I think) consider “space” to be “what’s in between the matter” which seems like it must be “nothing”. But how can “nothing” possess an attribute like curvature? This leads you to conclude that space is much more than nothing. But it’s not a form of matter. So what is it? This chain of thought often leads people to think of space as being like the Ether, but that’s not right either. Hmm.

I tend to avoid this problem by not trying to think about space or space-time at all, and instead think only in terms of particle trajectories or ligh rays and how matter and energy affect them. But that’s because I’m lazy and only have a small brain…

 

 

Autumn Statement – Summary for Science

Posted in Politics, Science Politics with tags , , , on November 25, 2015 by telescoper

I’ve been in meetings all afternoon so far so I missed the live broadcast of the Chancellor’s Autumn Statement.

Now that I’ve caught up a little it seems that there’s much to be relieved about. Yet again it seems the Government has deployed the tactic of allowing scare stories of dire cuts to spread in order that the actual announcement  appears much better than people feared, even if it is mediocre.

You can find the overall key results of the spending review and autumn statement here, but along with many colleagues who work in research and higher education I went straight to the outcome for the Department of Business, Innovation and Skills (BIS) which you can find here.

The main results for me – from the narrow perspective of a scientist working in a university –  are:

  1. The overall budget for BIS will be cut by 17% in cash terms between now and 2020.
  2. Most of the above cut will happens from 2018 onwards by, among other things, “asking universities to take more responsibility for student access”.
  3. In more detail (quoted from here) “In this context, the government will reduce the teaching grant by £120 million in cash terms by 2019 to 2020, but allow funding for high cost subjects to be protected in real terms. The government will work with the Director of Fair Access to ensure universities take more responsibility for widening access and social mobility, and ask the Higher Education Funding Council for England to retarget and reduce by up to half the student opportunity fund, focusing funding on institutions with the most effective outcomes. The government will also make savings in other areas of the teaching grant.”
  4. My current employer, the University of Sussex, has done extremely well on widening participation so this is good news locally. Many big universities have achieved nothing in this area so, frankly, deserve this funding to be withdrawn.
  5. It is also to be welcomed that the premium for high cost subjects (i.e. STEM disciplines) is to be protected in real terms, although it still does not affect the actual cost of teaching these subjects.
  6. Contrary to many expectations it seems that HEFCE will not be scrapped immediately. That is significant in itself.
  7. The level of science funding will increase from £4.6 billion to £4.7 billion next year, and will thereafter be protected in real terms over the Parliament.
  8. The real terms protection sounds good but of course we currently have a very low rate of inflation, so this is basically five more years of almost flat cash.
  9. There is supposed to be an additional £500m by 2020 which George Osborne didn’t mention in his speech. I don’t know whether this is extra money or just the cash increase estimated by inflation-proofing the £4.7bn.
  10. The above two points sound like good news….
  11. …but the total budget  will include a £1.5 billion new “Global Challenges Fund” which will build up over this period. This suggests that there may be a significant transfer of funds into this from existing programmes. There could be big losers in this process, as it amounts to a sizeable fraction of the total research expenditure.
  12. In any event the fraction of GDP the UK spends on science is not going to increase, leaving us well behind our main economic competitors.
  13. The Government is committed to implementing the Nurse Review, which will give it more direct leverage to reprioritise science spending.
  14. It isn’t clear to me how  “pure” science research will fare as a result of all this. We will have to wait and see….

The Autumn Statement includes only a very high level summary of allocations so we don’t know anything much about how these decisions will filter down to specific programmes at this stage. The Devil is indeed in the Detail. Having said that, the overall settlement for HE and Research looks much better than many of us had feared so I’d give it a cautious welcome. For now.

If anyone has spotted anything I’ve missed or wishes to comment in any other way please use the box below!

 

100 Years of General Relativity

Posted in History, The Universe and Stuff with tags , on November 25, 2015 by telescoper

Many people have been celebrating the centenary of the birth of Einstein’s Theory of General Relativity this year, but it’s not obvious precisely what date to select. I’ve decided to go for today, partly because the News on BBC Radio 3 did when I work up this morning, but also because there is a well-known publication that mentions that date:

einsteingr

The 25th November 1915 was the date on which Einstein presented the “final” form of his theory to the Prussian Academy of Sciences. You can find a full translation of the paper “The Field Equations of Gravitation” here. You will see that he refers to a couple of earlier papers in that work, but I think this one is the first presentation of the full theory. It fascinated me when I was looking at the history of GR for the textbook I was working on about 20 years ago that the main results (e.g. on cosmology, the bending of light and on the perihelion of mercury) are spread over a large number of rather short papers rather than all being in one big one. I guess that was the style of the times!

So there you are, General Relativity has been around for 100 years. At least according to one particular reference frame…

 

Oh, and here’s a cute little video – funded by the Science and Technology Facilities Council – celebrating the centenary:

 

Chancellor’s Autumn Statement Poll

Posted in Politics, Science Politics on November 24, 2015 by telescoper

There’s a not inconsiderable amount of anxiety around as tomorrow’s  Autumn Statement approaches. The likelihood is that we will see drastic cuts to everything, including science and education, and huge jobs losses and cuts to public services around the country.

In order to gauge public opinion, ahead of the announcement of the end of British Civil Society I have decided to conduct a poll.

And in case it’s all too depressing to think about, Dorothy has knitted a Soup Dragon to cheer you up.

Soup-Dragon