Archive for October, 2017

Prize Port

Posted in Biographical, Crosswords with tags , , on October 20, 2017 by telescoper

Way back in July I went to the Third Day’s Play of the Test Match between England and South Africa. On the way to the ground I bought a copy of Money Week, a publication I have never read before, as requested by my old friend and regular commenter on this blog, Anton, who got the tickets for the match. During a lull in the play we did the crossword in the magazine, which was a not-too-difficult thematic puzzle. When I got back to Cardiff I posted off the solution, as a prize of a bottle of vintage port was on offer. Not hearing any more, forgot about it.

When I got back from India this week there was a card waiting for me saying that ParcelForce had attempted to deliver a package while I was away. This morning I went to the main post office to sign for it and pick it up. This is what I got:

I don’t know why it took so long to deliver the prize but it makes a nice change from the usual dictionaries!

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Determining the Hubble Constant the Bernard Schutz way

Posted in The Universe and Stuff with tags , , , , , on October 19, 2017 by telescoper

In my short post about Monday’s announcement of the detection of a pair of coalescing neutron stars (GW170817), I mentioned that one of the results that caught my eye in particular was the paper about using such objects to determine the Hubble constant.

Here is the key result from that paper, i.e. the posterior distribution of the Hubble constant H0 given the data from GW170817:

You can also see latest determinations from other methods, which appear to be in (slight) tension; you can read more about this here. Clearly the new result from GW170817 yields a fairly broad range for H0 but, as I said in my earlier post, it’s very impressive to be straddling the target with the first salvo.

Anyway, I just thought I’d mention here that the method of measuring the Hubble constant using coalescing binary neutron stars was invented by none other than Bernard Schutz of Cardiff University, who works in the Data Innovation Institute (as I do). The idea was first published in September 1986 in a Letter to Nature. Here is the first paragraph:

I report here how gravitational wave observations can be used to determine the Hubble constant, H 0. The nearly monochromatic gravitational waves emitted by the decaying orbit of an ultra–compact, two–neutron–star binary system just before the stars coalesce are very likely to be detected by the kilometre–sized interferometric gravitational wave antennas now being designed1–4. The signal is easily identified and contains enough information to determine the absolute distance to the binary, independently of any assumptions about the masses of the stars. Ten events out to 100 Mpc may suffice to measure the Hubble constant to 3% accuracy.

In in the paper, Bernard points out that a binary coalescence — such as the merger of two neutron stars — is a self calibrating `standard candle’, which means that it is possible to infer directly the distance without using the cosmic distance ladder. The key insight is that the rate at which the binary’s frequency changes is directly related to the amplitude of the gravitational waves it produces, i.e. how `loud’ the GW signal is. Just as the observed brightness of a star depends on both its intrinsic luminosity and how far away it is, the strength of the gravitational waves received at LIGO depends on both the intrinsic loudness of the source and how far away it is. By observing the waves with detectors like LIGO and Virgo, we can determine both the intrinsic loudness of the gravitational waves as well as their loudness at the Earth. This allows us to directly determine distance to the source.

It may have taken 31 years to get a measurement, but hopefully it won’t be long before there are enough detections to provide greater precision – and hopefully accuracy! – than the current methods can manage!

Above all, congratulations to Bernard for inventing a method which has now been shown to work very well!

Back to Blighty

Posted in Biographical, The Universe and Stuff with tags , , on October 18, 2017 by telescoper

Just a brief post today to say that I got back safe and sound last night. I was up at 4am Tuesday Pune time (which was 11.30pm Monday UK time) and finally got to bed at about 11.30pm UK time last night, so apart from about 45 minutes doze on the flight I had been awake for 24 hours. Not surprisingly, I slept in this morning!

After another white-knuckle taxi ride (with the added complication of thick fog) I got Mumbai airport in good time. The flight itself was almost empty. Not only did I get a row of seats to myself in economy class, but the two rows in front in and the two rows behind were also unoccupied. I’m not entirely sure why the flight was so underbooked – as the outbound flight was absolutely crammed – but it may be that the festival of Diwali takes place this week (on Thursday or even today in some regions). Relatively few people are probably leaving India at this time compared with the many coming home to celebrate with friends and family. It’s a nice coincidence that Monday’s announcement of simultaneous detection of gravitational waves and electromagnetic radiation came so close to the Festival of Light, traditionally celebrated with fireworks and gifts of gold!

Despite liberal helpings of wine from the drinks trolley and the ability to lie down across three seats I still didn’t really sleep. I just don’t have the knack for sleeping on planes. Still, I did get to watch the film The Imitation Game which I hadn’t seen before and thought was very good.

We arrived back on schedule without the (usually) obligatory air traffic delays around Heathrow and, the arrivals hall being empty, I was out of the airport less than half an hour after landing. That’s a bit of record for me!

Anyway, I’ve various things to catch up on now that I’m back so I’ll try to get on with them. I’ll just end by thanking my hosts at IUCAA again for their hospitality and, while I’m at it, send a Happy Diwali message in Marathi to them and anyone else celebrating at this special time:

 

GW News Day

Posted in The Universe and Stuff with tags , , on October 16, 2017 by telescoper

Well, it has certainly been an eventful last day in India!

Over a hundred people gathered at IUCAA to see this evening’s press conference, which basically confirmed most of the rumours that had been circulating that a Gamma Ray Burst had been detected in both GW and EM radiation. I won’t write in detail about today’s announcement because (a) a really useful page of resources has been prepared by the group at IUCAA. Check out the fact sheet and (b) I haven’t really had time to digest all the science yet.

I will mention a couple of things, however. One is that the signal-to-noise ratio of this detection is a whopping 32.4, a value that astronomers can usually only dream of! The other is that neutron star coalescence offer the possibility to bypass the traditional `distance ladder’ approaches to get an independent measurement of the Hubble constant. The value obtained is in the range 62 to 107 km s-1 Mpc-1, which is admittedly fairly broad, but is based on only one observation of this type. It is extremely impressive to be straddling the target with the very first salvo.

The LIGO collaboration is over a thousand people. Add to that the staff of no fewer than seventy observatories (including seven in space). With all that’s going in the world, it’s great to see what humans of different nations across the globe can do when they come together and work towards a common goal. Scientific results of this kind will remembered long after the silly ramblings of our politicians and other fools have been forgotten.

I took part in a panel discussion after the results were presented, but sadly I won’t be here to see tomorrow’s papers. I hope people will save cuttings or post weblinks if there are any articles!

UPDATE: Here is a selection of the local press coverage.

Indian LIGO

 

As if these thrilling science results weren’t enough I finally managed to meet my old friend and former collaborator Varun Sahni (who was away last week). An invitation to dinner at his house was not to be resisted on my last night here, which explains why I didn’t write a post immediately after the press conference. Still, of got plenty of papers to read on the plane tomorrow so maybe I’ll do something when I get back.

Tomorrow morning I get up early to return to Mumbai for the flight home, and am not likely to be online again until Wednesday UK time.

Thanks to all at IUCAA (and TIFR) for making my stay so pleasant and interesting. It’s been 23 years since I was last here. I hope it’s not so long before I’m back again!

Homes from Home in Pune

Posted in Biographical, History, The Universe and Stuff with tags , , , on October 16, 2017 by telescoper

Since I’m coming back tomorrow I thought I’d wander around this morning and take a few pictures of where I’ve been staying most of the last 10 days or so. First, this is a snap of the housing complex which contains my guest apartment.

I’m actually in the first building on the right. Here is the front door.

The faculty at both IUCAA (Pune) and TFIR (Mumbai) live in housing areas provided by their respective institutions, so they form quite a close-knit community. Some of the senior staff in IUCAA are housed just round the corner from my place.

IUCAA is on the Pune University Campus (except that it has its own entrance from the main road that runs along the Northern edge of the campus, where there is a security post. There are a few of these around the IUCAA site itself, so it is very secure and quite private. The campus is large with many tree-lined roads. At its heart, on a small hill, you can find this building:

This is (or was) the Raj Bhavan (`Government House’) and it was essentially the Governor of Maharashtra’s residence during the Monsoon season. Built in 1866, it was a sort of home-from-home when Bombay (the state capital) became too unbearable.

When I was last here in 1994, this was the Main Building of the University and was quite busy. Now, however, it seems to be disused and is in a state of some disrepair, the gardens also need a bit of love and attention. There are many new buildings around the University of Pune campus (including a modern administration block nearby). Since this building is a relic of the old colonial days it may be that it will be demolished to make way for something that better suits modern India. By the way, there’s a stone slab just next to the site of this building that displays the preamble to the Constitution of India, as adopted in 1949.

Anyway, this afternoon and evening promise to be quite busy. There is a press conference at IUCAA at 6.30pm about the gravitational waves discovery I mentioned a few days ago. There will be presentations before a viewing of the live feed from Washington DC then there’ll be a panel answering questions from the press. They’ve asked me to be on the panel, so I might appear in the India media, but as I’m leaving first thing tomorrow morning I probably won’t see any of the coverage!

Before the Storm…

Posted in Biographical, History with tags , , , , on October 16, 2017 by telescoper

Nearly at the end of my short visit to India I find myself checking on the UK news. Home thoughts from abroad and all that. Anyway, it’s quite a coincidence that Hurricane Ophelia is arriving,  exactly on the thirtieth anniversary of the famous `Great Storm‘ that wrought destruction across the South-East of England in 1987. The path of Ophelia is rather different from that of the 1987 `Hurricane’, and it looks like Ireland will bear the brunt over the next day or two, as the storm will weaken as it encounters land, though there will be strong winds far outside the path denoted in this map:

 

I hope the damage from this storm  isn’t too bad and that people in its path stay safely out of harm’s way, especially in Ireland. It’s possible the winds may affect my current home in Wales too. I hope I don’t get back tomorrow evening to find the roof has blown off!

Thirty years ago today I was living in Brighton as a graduate student at the University of Sussex. On October 16th 1987 (a Friday) I woke up to find the electricity had been cut off. Without breakfast I struggled out to find the street lined with fallen trees, smashed cars and houses with broken windows. I got to the railway station to get the train to Falmer (where the University of Sussex is located) only to find that no trains were running. I walked home and went back to bed. It took several days for normal service to resume. When I did get up to campus the following week, I found that almost all the trees in Stanmer Park had come down and were combed flat on the top of the hill.

The Great Storm of 1987 , according to weather forecaster Michael Fish, was “not a hurricane” had nevertheless caused enormours destruction. And I had slept through the whole thing…

Here’s the infamous weather forecast broadcast on the Thursday evening:

and here is the BBC News from the following day:

 

Farewell to TIFR

Posted in Art, Biographical with tags , , , on October 15, 2017 by telescoper

I got up early again this morning to travel back to Pune for the final few days of this trip. Last night I had a pleasant dinner with my host Subha Majumdar at the Indigo Deli to round off my short stay in Mumbai. The food was nice, but it was a tad overpriced in my opinion. We passed by the Leopold Cafe on the way home; that was the scene of a terrorist atrocity in 2008 I remember having tea there in 1994, after returning from a boat trip to Elephant Island.

I went sightseeing yesterday morning but forgot to take my camera with me then. I left reasonably early so that I could wander around before it got too hot – the afternoon was sweltering on Friday – but when I arrived at my main destination (the National Gallery of Modern art) I found it didn’t open until 11am, so I had to find somewhere for a cup of tea (which wasn’t difficult). When it opened I found a pricing strategy that is common in India: 20 rupees for Indians and 500 rupees for foreigners! Still, 500 rupees is only about £6 and though small the gallery is well worth seeing.

When I returned to the TIFR `Colony’ I picked up my camera and took a few snaps of the Tata Institute for Fundamental Research before spending the afternoon in the office. As you can see, TIFR is set in lovely grounds with some gorgeous trees. It’s also right next to the sea, but the view wasn’t great yesterday as it was misty. Later on there were heavy thunderstorms.

Now I think I’ll take a short nap. It’s just after 10am, but I was up before 5am after just a few hours sleep. I hope I wake up in time for lunch!