Archive for Square Kilometre Array

Post-Planck Cosmology: Day 3

Posted in The Universe and Stuff with tags , , , , on October 11, 2017 by telescoper

Before carrying on with my daily updates from this meeting on Post-Planck Cosmology I’ll just remark that this is a great venue: it has all the facilities necessary to keep a group of cosmologists happy…


At the tea break this morning I managed to find a shot that included all four of the statues in the main quadrangle too:

This morning kicked off with Roy Maartens discussing the cosmological potential of the Square Kilometre Array and other future galaxy surveys, one of his main points being the benefit of using multiple tracers to beat down some of the problems with single surveys.  The first phase of this project, SKA1,  will deliver 10 million redshifts with z<0.6. With SKA2 that will go up to 1 billion galaxies out to z<2, but many things can be done without redshifts using intensity mapping. SKA1 is some way off, but the precursor `Meerkat' consisting of 64 × 13.5 metre dishes will be hopefully starting next year in South Africa.

We then had a series of talks about reionization and the formation of the first stars, an epoch usually referred to as `Cosmic Dawn' or `First Light', taking us into lunch.

In the afternoon we had talks loosely grouped around the theme of `classical cosmology' – using geometric or other probes to study the expansion history of the Universe. This session included a talk by Chris Messenger of the LIGO collaboration about the beginnings of gravitational wave cosmology, though as the current generation of detectors is only sensitive to relatively nearby sources for the time being the main effort will be devoted to distance scale measurements, attempting to measure the Hubble constant directly without the need for the traditional distance ladder.

The last part of the day was devoted to a panel discussion, chaired by Francois Bouchet that was interesting and wide-ranging but largely motivated by responses to Paul Steinhardt's talk last night.

Now, no conference dinner to tear me away tonight – but I do have to finish my talk, which is at 9am tomorrow – so that will have to do for now. Toodle-pip!

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What does “Big Data” mean to you?

Posted in The Universe and Stuff with tags , , , , on April 7, 2016 by telescoper

On several occasions recently I’ve had to talk about Big Data for one reason or another. I’m always at a disadvantage when I do that because I really dislike the term.Clearly I’m not the only one who feels this way:

say-big-data-one-more-time

For one thing the term “Big Data” seems to me like describing the Ocean as “Big Water”. For another it’s not really just the how big the data set is that matters. Size isn’t everything, after all. There is much truth in Stalin’s comment that “Quantity has a quality all its own” in that very large data sets allow you to do things you wouldn’t even try with smaller ones, but it can be complexity rather than sheer size that also requires new methods of analysis.

Planck_CMB_large

The biggest event in my own field of cosmology in the last few years has been the Planck mission. The data set is indeed huge: the above map of the temperature pattern in the cosmic microwave background has no fewer than 167 million pixels. That certainly caused some headaches in the analysis pipeline, but I think I would argue that this wasn’t really a Big Data project. I don’t mean that to be insulting to anyone, just that the main analysis of the Planck data was aimed at doing something very similar to what had been done (by WMAP), i.e. extracting the power spectrum of temperature fluctuations:

Planck_power_spectrum_origIt’s a wonderful result of course that extends the measurements that WMAP made up to much higher frequencies, but Planck’s goals were phrased in similar terms to those of WMAP – to pin down the parameters of the standard model to as high accuracy as possible. For me, a real “Big Data” approach to cosmic microwave background studies would involve doing something that couldn’t have been done at all with a smaller data set. An example that springs to mind is looking for indications of effects beyond the standard model.

Moreover what passes for Big Data in some fields would be just called “data” in others. For example, the Atlas Detector on the  Large Hadron Collider  represents about 150 million sensors delivering data 40 million times per second. There are about 600 million collisions per second, out of which perhaps one hundred per second are useful. The issue here is then one of dealing with an enormous rate of data in such a way as to be able to discard most of it very quickly. The same will be true of the Square Kilometre Array which will acquire exabytes of data every day out of which perhaps one petabyte will need to be stored. Both these projects involve data sets much bigger and more difficult to handle that what might pass for Big Data in other arenas.

Books you can buy at airports about Big Data generally list the following four or five characteristics:

  1. Volume
  2. Velocity
  3. Variety
  4. Veracity
  5. Variability

The first two are about the size and acquisition rate of the data mentioned above but the others are more about qualitatively different matters. For example, in cosmology nowadays we have to deal with data sets which are indeed quite large, but also very different in form.  We need to be able to do efficient joint analyses of heterogeneous data structures with very different sampling properties and systematic errors in such a way that we get the best science results we can. Now that’s a Big Data challenge!

 

SKA Matters

Posted in Science Politics, The Universe and Stuff with tags , , , , on March 13, 2015 by telescoper

There’s been quite a lot going on recently to do with the Square Kilometre Array (SKA), some of it scientific and some of it political, some of it good and some of it bad. At least those seem to me to be the appropriate descriptions.

First the scientific good news is the the SKA Board has decided which of the planned components of SKA should be constructed during the first phase, which has a budget of around €650M. Details can be found here but, in a nutshell, it seems that the SKA Survey Telescope, which was to be built around the existing pathfinder project ASKAP located in Australia is not going to be built in the first phase. This implies the low-frequency bit of SKA will be in Australia while the higher-frequency activities will be concentrated in South Africa. That seems a pragmatic decision to me based on the budgetary constraints and should lead to a lot of good science being done. At the very least it’s a clear decision.

This positive news has however been overshadowed by an unseemly spat over the choice of headquarters over the location of the SKA Headquarters which has culminated in a rather unhelpful story in Nature. SKA HQ has been temporarily housed at Jodrell Bank Observatory (in the Midlands) since 2012 and there are clearly some who would like it to be located there permanently. There is however a rival bid, from the historic Italian city of Padova, at whose university Galileo Galilei once lectured, and which remains one of the top universities in Italy.

I should put my cards on the table and say that I’ve enjoyed many visits to Padova in my career, starting when I was a PhD student back in the 1980s and have many fond memories of the place. The late co-author of my cosmology textbook, Francesco Lucchin was Director of the Department of Astronomy in Padova at that time. For many years Padova has been home to a large concentration of astronomers and is undoubtedly a centre of excellence. Moreover it is a city that is very well served by transport links, just a short distance from Venice so easily reachable by air, and also on a major railway line offering fast national and international services. It’s also a considerably better place to dine out than Jodrell Bank!

Specola

Padova’s astronomers are housed in the Castello Carrese which adjoins the Specola (above), a tower which was once a working astronomical observatory but, being right in the city centre, has not been useful for such purposes for many moons. When I first started going to Padova the Department of Astronomy was located in the tower and in some nearby buildings but the rest of the Castello Carrese was used as a prison. Now it’s been renovated and all the astronomers have been located there. I remember the frequent walks across the little bridge over the canal to a coffee bar where we often did some of our best research!

Given its strategically important location, Padova was bombed by Allied planes on a number of occasions in 1944 and 1945. My Italian colleagues would regularly draw my attention to the plaque near the entrance to the Specola pointing out that it was hit and badly damaged by Allied bombs during one raid.

Anyway I can certainly see the merits of locating SKA HQ in Padova but it’s not my decision to make. Those responsible have not yet made a final decision, but what’s sad is that a number of stories have been flying around in the media that imply that the UK is trying to exert undue political interference to stop SKA HQ being moved to Italy. Whether this is true or not I don’t know. As far as I’m concerned the powers that be are following proper process and that process has not yet been brought to a conclusion. Whatever the outcome, though, there’s no question that the language being used in the press coverage is very damaging. Let’s hope it can all be resolved amicably.

Now for a spot of lunch and then up to the Royal Astronomical Society where the topic of the Discussion Meeting is, somewhat ironically, Building an Open UK SKA-Science Consortium…

E-ELT: The Big Picture

Posted in Science Politics, The Universe and Stuff with tags , , , on March 4, 2013 by telescoper

Some astronomy news that made a bit of a splash over the weekend was the announcement that the UK is to invest £88 million in the European Extremely Large Telescope. This amount is to be spread over 10 years, so isn’t quite as astronomical as it sounds, but in any case it is only the UK’s contribution to a project that involves large contributions from the other countries involved in the European Southern Observatory. The UK announcement isn’t the end of the story, in fact, as not all the money needed to make the project work is yet in place.

This is all good news, especially because not long ago it seemed quite likely that the UK would have to make a choice between the E-ELT and the Square Kilometre Array. Now it looks like we’re going to be involved in both of the world’s leading ground-based observational facilities. There is a price to be paid, of course. In order to accommodate these projects within the flat-cash budget of the Science and Technology Facilities Council, difficult choices had to be made, and some things have to go. Not everyone will be happy about the outcome, but Big Science requires Big Decisions.

Anyway, it was nice to see the Observer run a piece about this story, although I was a bit baffled by the implication of the caption going with the picture used to illustrate the story:

The European Extremely Large Telescope will study the Magellanic Cloud.

I’ll avoid asking “which Magellanic Cloud (Large or Small)?” and just point out that E-ELT will study a lot more than either or both! Still, people are more likely to read web articles if they include images, so I’ll end this piece with an appropriate one.

Random Astronomical Image

Random Astronomical Image

SKA Site Duel ends in Dual Site for SKA

Posted in Science Politics, The Universe and Stuff with tags , , , , , on May 26, 2012 by telescoper

I wasn’t going to post about this but then I realised nobody seemed to have used the obvious headline so thought I might as well knock out a quickie.

Yesterday, after much to-ing and fro-ing an announcement was finally made  concerning the site of the Square Kilometre Array.  The two contenders for the honour of hosting this superb project were South Africa and Australasia (both Australia and New Zealand get a bit, actually).

So who won?

Well, formally the decision was to split the project between both. At first sight this looks like a political compromise, but wiser heads than me disagree and say that this an excellent outcome on science grounds. I’d be interested to hear  opinions on that, in fact.

In any case, a quick skim through the STFC announcement makes it clear that South Africa actually gets the lion’s share of the actual dishes, which will be operated alongside the  Meerkat facility, and will do what I think is the more exciting science.  Having been to Cape Town just recently I know how much the SKA project means for astronomy in South Africa so I’m delighted for them that the outcome is so positive.

It does, however, remain to be seen what the implications of this decision are for the overall cost and scientific value-for-money, but for the time being the thing I’m most pleased about is that a decision has been reached.  I think the SKA project is by far the most exciting ground-based astronomy project around, and it will be very exciting to watch it grow.

The SKA Propaganda Machine

Posted in Astrohype, Science Politics, The Universe and Stuff with tags , , , , on February 14, 2012 by telescoper

I’m a big fan of the Square Kilometre Array, a proposed new radio telescope that will revolutionize our understanding of many aspects of astrophysics.

I’m somewhat less keen on the intense lobbying being carried out on behalf of Australian astronomers in advance of the decision whether to site it in Australia or South Africa. The campaign is being orchestrated by a PR organization called Ogilvy and Mather who are making full use of social media to promote the Australian case.

Last week I was invited by email to attend a “webinar” (whatever that is) about the SKA, an invitation that I quietly ignored. Today I got a follow-up email from a person described as a “Digital Analyst” offering me the chance to “interview Dr Brian Boyle or Dr Lisa Harvey Smith”. They also sent me the following “infographic” (i.e. a picture) showing the case for siting the SKA in Australia, which they thought would be of interest to “my blog readers”.

Well, you can call me old-fashioned but I think there’s something a bit distasteful about engaging a glorified ad agency to lobby on behalf of one party in a discussion that should be resolved on purely scientific grounds. I wonder how much it cost, for a start, but I’d also have hoped scientists would be above that sort of thing anyway. Sign of the times, I suppose.

Anyway, even if the digital analysts at Ogilvy will be happy that I’ve shown their infographic, perhaps they might now realize that spin can work in two different ways…

On My Radio (Telescope) …

Posted in Science Politics, The Universe and Stuff with tags , , , , , , on April 7, 2011 by telescoper

A piece of news I should have passed on sooner than this is the announcement that the  Headquarters for the Square Kilometre Array will be based at the Jodrell Bank Observatory which, as you all know, is situated in the English Midlands.

The Square Kilometre Array (known to the astronomical community as SKA) will be, when it’s built, the largest radio telescope, and in fact the largest telescope of any kind, ever constructed.  Building it will be a huge technical challenge, and it involves teams from all around the world. Although it hasn’t yet been decided where the actual kit will be sited – Australia and South Africa are two strong contenders – it’s definitely a coup for the UK to be hosting the Project Office. So congratulations to Jodrell Bank and to John Womersley, Director of Science Programmes at the Science and Technology Facilities Council who will be heading up the operation.

I think  that the SKA is by far the most exciting project in ground-based astronomy on the STFC books: it has a significantly stronger science case than its competitor in the optical part of the spectrum, the European Extremely Large Telescope (E-ELT), although it is admittedly more of a challenge to build it from a technological point of view. Over the last few years I’ve feared on many occasions that STFC would have to pull out of one of these two very expensive projects and that E-ELT would be the one that survived because it is within the remit of the European Southern Observatory (ESO) to which we pay a hefty subscription. Fortunately the clouds seem to have lifted a bit and it looks like we’re going to remain in both, which is excellent news for UK astronomy.

I was thinking of putting up a bit of music to celebrate the good news. Hmmm….Ska….radio. No brainer really. I wonder who was The Selecter for the  location of the SKA Project Office?

P.S. I just looked at the date when On My Radio was in the charts. October 1979, when I was 16.  I have to confess that in those days I had a massive crush on lead singer Pauline Black


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