Quick Advert:
Tomorrow (Wednesday 19th May), a free public physics lecture is being given in Lecture Theatre M at the University of Surrey at 7pm. It's being given by Prof David Sanderson of SUERC - the Scottish Universities Environmental Research Centre, and it's about how to detect irradiated food, a technique which the SUERC group developed and is now a European standard.
I picked up a delivery today of some equipment that the speaker wants to use in the talk - and am intrigued!
No booking is required - just turn up to Lecture Theatre M for a 7pm start
Tuesday, 18 May 2010
Sunday, 9 May 2010
What if everyone were a nucleus?
In a series of tweets this evening Jim Al-Khalili pointed out that there has been a small disagreement between him in his Atom series and Michael Mosley in the Story of Science. They each illustrated the ratio of occupied space to empty space in atoms by saying that if all the empty space were taken out of the entire human population then we would occupy a volume the size of an apple (Jim's calculation) or a sugarcube (Michael's calculation).
In either case, the analogy makes clear that atoms have a whole lot of empty space, but in terms of volume, there's a fair bit of difference between a sugarcube (around 1 cm3) and an apple (around 200 cm3). So who is right?
The population of the world is around 7 billion. The average mass of people is usually taken to be around 70kg so the mass of the human population is 7×109×70 kg = 490 000 000 000 kg. Let's call that 5×1011 kg. Now, if all the space were taken out of all these atoms, we would essentially be left with an enormous nucleus (as Jim says, a pulsar). The density of nuclear matter (i.e. of the inside of an enormous nucleus) is 0.16 nucleons per cubic femtometer. A nucleon weighs 1.7×10-27 kg.
So: The number of nucleons in total is 5×1011 / 1.7×10-27 = 3×1038 nucleons, giving a volume of 3×1038/0.16 = 2×1039 fm3 = 2 cm3.
Looks like I agree with Michael, more or less... unless I've guessed the size of a sugarcube wrongly. I mean, I haven't seen a sugarcube for years.
In either case, the analogy makes clear that atoms have a whole lot of empty space, but in terms of volume, there's a fair bit of difference between a sugarcube (around 1 cm3) and an apple (around 200 cm3). So who is right?
The population of the world is around 7 billion. The average mass of people is usually taken to be around 70kg so the mass of the human population is 7×109×70 kg = 490 000 000 000 kg. Let's call that 5×1011 kg. Now, if all the space were taken out of all these atoms, we would essentially be left with an enormous nucleus (as Jim says, a pulsar). The density of nuclear matter (i.e. of the inside of an enormous nucleus) is 0.16 nucleons per cubic femtometer. A nucleon weighs 1.7×10-27 kg.
So: The number of nucleons in total is 5×1011 / 1.7×10-27 = 3×1038 nucleons, giving a volume of 3×1038/0.16 = 2×1039 fm3 = 2 cm3.
Looks like I agree with Michael, more or less... unless I've guessed the size of a sugarcube wrongly. I mean, I haven't seen a sugarcube for years.
Wednesday, 5 May 2010
Nuclear Physics and the Election
I've not blogged at all about the forthcoming election. Nuclear physics is a pretty minor issue in the election, but not completely non-existent. The amount of overall science funding will be a factor in determining how much money will be spent on nuclear physics research, and the commitment to nuclear power (or otherwise) of the parties will be a factor in determining how much the UK is interested in keeping a knowledge base in nuclear science and engineering on a broader scale. These two facts are ironically approximately inversely correlated in the three main parties. I don't think I'd ever vote on a single issue alone, but there doesn't seem to be a completely obvious choice from a nuclear physics point of view. I think Martin Robbins' article in the Guardian sums things up pretty well, though, from an overall science perspective.
Tuesday, 20 April 2010
Edinburgh
Well, to follow up the last post, I did go to the hat shop, and now have a nice grey trilby and a black bowler. I also did attend Jim Al-Khalili's talk, where he pointed out some of the sexy things about nuclear physics - the things that excite people - like the fact that looking up at the night sky means looking at nuclear reactions. He also said that no matter what you do in nuclear physics, you should be able to talk passionately and with enthusiasm about what you do.
I think that's right. You don't have to be creating new elements or looking at stellar nuclear reactions - if you're doing it, it should have a purpose that you should be able to enthuse people about. And of course, this goes for all scientists, generally. I wonder how many scientists would be able to do that to any member of the public. I like to think that I'm a little more practiced at it, but my recent encounter on I'm a scientist reminds me that it's not always so easy. Must make more effort to try - otherwise, why am I doing it?
In other conference news, I chaired a session earlier today featuring talks by current PhD students, and I am happy to report that they all gave decent talks and were clearly interested in what they are doing. Probably the best was the talk about laser spectroscopy, in which some pretty clever experiments were described which used atomic transitions to understand the properties of nuclei. Electrons in atoms get slightly affected by the fact that different nuclei have different sizes and shapes, and one can actually measure nuclei by looking at atomic (electron) transitions. A very nice talk by Frances Charlwood of Manchester showed how her group have been figuring out the size and shape changes in manganese isotopes, and showing how the sizes show distinctive changes when you reach the N=28 (28 neutrons) magic (extra-stable) number, yet the nuclear mass does not. It's a bit of a puzzle, and must be telling us something about nuclear structure - just trying to think what it is...
I think that's right. You don't have to be creating new elements or looking at stellar nuclear reactions - if you're doing it, it should have a purpose that you should be able to enthuse people about. And of course, this goes for all scientists, generally. I wonder how many scientists would be able to do that to any member of the public. I like to think that I'm a little more practiced at it, but my recent encounter on I'm a scientist reminds me that it's not always so easy. Must make more effort to try - otherwise, why am I doing it?
In other conference news, I chaired a session earlier today featuring talks by current PhD students, and I am happy to report that they all gave decent talks and were clearly interested in what they are doing. Probably the best was the talk about laser spectroscopy, in which some pretty clever experiments were described which used atomic transitions to understand the properties of nuclei. Electrons in atoms get slightly affected by the fact that different nuclei have different sizes and shapes, and one can actually measure nuclei by looking at atomic (electron) transitions. A very nice talk by Frances Charlwood of Manchester showed how her group have been figuring out the size and shape changes in manganese isotopes, and showing how the sizes show distinctive changes when you reach the N=28 (28 neutrons) magic (extra-stable) number, yet the nuclear mass does not. It's a bit of a puzzle, and must be telling us something about nuclear structure - just trying to think what it is...
Sunday, 18 April 2010
In Edinburgh
I'm in Edinburgh for the annual Institute of Physics Nuclear Physics Conference. It's partly an excuse for everyone in the UK nuclear physics community to get together and chew the fat, to discuss latest research, to discuss funding issues and to drink wine. Or beer. I've mostly drunk beer so far. I made the excellent decision to book a seat on a train far in advance. In fact, three seats since my partner and daughter are here too. The train was completely packed, not helped by the lack of flights currently. I was impressed with how well my two-year-old coped with the long journey, though I have learnt that other passengers get somewhat irate when they see you use a nit-comb on your child in public, and tell you that you shouldn't be out spreading lice.
So, the conference has a fun-packed schedule of talks. I'm looking forward to Jim Al-Khalili's talk entitled Is Nuclear Physics Research Sexy? (presumably the answer is simply "yes") and a finding out what some of the students in groups around the country are up to in the parallel sessions. And everything else, of course. But I might find time during my stay to go to Fabhatrix, an excellent hat shop on Grassmarket. When I say might, I think I mean will.
So, the conference has a fun-packed schedule of talks. I'm looking forward to Jim Al-Khalili's talk entitled Is Nuclear Physics Research Sexy? (presumably the answer is simply "yes") and a finding out what some of the students in groups around the country are up to in the parallel sessions. And everything else, of course. But I might find time during my stay to go to Fabhatrix, an excellent hat shop on Grassmarket. When I say might, I think I mean will.
Friday, 16 April 2010
Nuclear Power Quiz
From CNN, a nuclear power quiz. I got 9 / 10 :-)
http://edition.cnn.com/2010/TECH/03/31/nuclear.power.quiz/index.html
http://edition.cnn.com/2010/TECH/03/31/nuclear.power.quiz/index.html
Wednesday, 14 April 2010
New element!
A paper, just published in Physical Review Letters, has announced the first observation of element 117. This element, which will only be named when confirmed by an independent experiment and ratified by IUPAC, has been observed in an collaborative experiment between groups in Russia and the USA. The experiment took an isotope of Calcium and an isotope of an already rather heavy synthetic nucleus Berkelium, and produced two different isotopes of element 117. These isotopes decayed by a combination of alpha decay and fission, with a chain of decays that left a trail from which element 117 could be deduced. The observation gives further evidence that there may be more long-lived elements in the region.
There is no element 117 on Earth, but it is possible that it is produced in supernovae. Better understanding of the superheavy elements created in the lab helps us understand element formation in the stars, as well as the way in which protons and neutrons interact to give stable nuclei.
There is no element 117 on Earth, but it is possible that it is produced in supernovae. Better understanding of the superheavy elements created in the lab helps us understand element formation in the stars, as well as the way in which protons and neutrons interact to give stable nuclei.
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