Archive for the The Universe and Stuff Category

Dark Energy’s Day

Posted in The Universe and Stuff with tags , , , on October 4, 2011 by telescoper

Following hard on the heels of the announcement of a Nobel Prize for cosmology earlier this morning, the European Space Agency has this afternoon officially announced the two candidates which have been chosen for its next M-class missions from a shortlist of three.

One of the successful candidates, EUCLID, is directly relevant to the topic covered by the Nobel Prize announced this morning. “Euclid will address key questions relevant to fundamental physics and cosmology, namely the nature of the mysterious dark energy and dark matter. Astronomers are now convinced that these substances dominate ordinary matter. Euclid would map the distribution of galaxies to reveal the underlying ‘dark’ architecture of the Universe.”

Now that it’s definitely been selected, I hope to devote time in due course for a longer post about EUCLID’s capabilities and intentions, but in the meantime I’ll just say that it’s been a very good day for Dark Energy.

P.S. The other successful candidate is called Solar Orbiter. Commiserations to advocates of the third mission on the shortlist of three, PLATO. Close, but no cigar…

Another Nobel Prize for Cosmology!

Posted in The Universe and Stuff with tags , , , , , , , on October 4, 2011 by telescoper

Just time in between teaching and meetings for a quick post on today’s announcement that the 2011 Nobel Prize for Physics has gone to Saul Perlmutter, Brian P. Schmidt and Adam G. Riess “for the discovery of the accelerating expansion of the Universe through observations of distant supernovae.”

I’ve taken the liberty of copying the following text from the press release on the Nobel Foundation website

In 1998, cosmology was shaken at its foundations as two research teams presented their findings. Headed by Saul Perlmutter, one of the teams had set to work in 1988. Brian Schmidt headed another team, launched at the end of 1994, where Adam Riess was to play a crucial role.

The research teams raced to map the Universe by locating the most distant supernovae. More sophisticated telescopes on the ground and in space, as well as more powerful computers and new digital imaging sensors (CCD, Nobel Prize in Physics in 2009), opened the possibility in the 1990s to add more pieces to the cosmological puzzle.

The teams used a particular kind of supernova, called type Ia supernova. It is an explosion of an old compact star that is as heavy as the Sun but as small as the Earth. A single such supernova can emit as much light as a whole galaxy. All in all, the two research teams found over 50 distant supernovae whose light was weaker than expected – this was a sign that the expansion of the Universe was accelerating. The potential pitfalls had been numerous, and the scientists found reassurance in the fact that both groups had reached the same astonishing conclusion.

For almost a century, the Universe has been known to be expanding as a consequence of the Big Bang about 14 billion years ago. However, the discovery that this expansion is accelerating is astounding. If the expansion will continue to speed up the Universe will end in ice.

The acceleration is thought to be driven by dark energy, but what that dark energy is remains an enigma – perhaps the greatest in physics today. What is known is that dark energy constitutes about three quarters of the Universe. Therefore the findings of the 2011 Nobel Laureates in Physics have helped to unveil a Universe that to a large extent is unknown to science. And everything is possible again.

I’m definitely among the skeptics when it comes to the standard interpretation of the supernova measurements, and more recent complementary data, in terms of dark energy. However this doesn’t diminish in any way my delight that these three scientists have been rewarded for their sterling observational efforts. The two groups involved in the Supernova Cosmology Project on the one hand, and the High Z Supernova Search, on the other, are both supreme examples of excellence in observational astronomy, taking on and overcoming what were previously thought to be insurmountable observational challenges. This award has been in the air for a few years now, and I’m delighted for all three scientists that their time has come at last. To my mind their discovery is all the more exciting because nobody really knows precisely what it is that they have discovered!

I know that Brian Schmidt is an occasional reader and commenter on this blog. I suspect he might be a little busy right now with the rest of the world’s media right to read this, let alone comment on here, but that won’t stop me congratulating him and the other winners on their achievement. I’m sure they’ll enjoy their visit to Stockholm!

Meanwhile the rest of us can bask in their reflected glory. There’s also been a huge amount of press interest in this announcement which has kept my phone ringing this morning. It’s only been five years since a Nobel Prize in physics went to cosmology, which says something for how exciting a field this is to work in!

UPDATE: There’s an interesting collection of quotes and reactions on the Guardian website, updated live.

UPDATE on the UPDATE: Yours truly gets a quote on the Nature News article about this!

Galaxies con Alma

Posted in The Universe and Stuff with tags , , , , on October 3, 2011 by telescoper

It’s back to School with a vengeance today, so not much time for the blog. However, I couldn’t resist mentioning the fact that the European Southern Observatory’s Atacama Large Millimetre Array, known to its friends as ALMA, has at last opened its eyes. Or at least some of them. ALMA in fact is an interferometer which eventually will comprise 66 dishes,   working together to with baselines as long 16km to synthesize a single huge aperture. The preliminary results that have just been released were obtained using just 16 dishes so they only offer a taste of what the full ALMA will do when it’s completed in 2013.

ALMA works in the millimetre wave region of the spectrum, operating at wavelengths between 0.3 and 9.6 mm. The overlap with the  wavelength range probed by the Herschel Space Observatory together with its much higher resolution than Herschel, which is a single telescope of only 3.5m diameter, makes the two very complementary: Herschel is good for surveying large parts of the sky, because it has a large field of view, whereas ALMA can do high-resolution follow-up of selected regions.

Anyway, here is ALMA’s view of the Antennae Galaxies (left) shown next to an optical image taken with the Very Large Telescope (VLT).

The system consists of two galaxies so close together that they interact strongly with each other via enormous tidal forces, hence the disturbed structure. The coloured regions in the ALMA image show radiation emanating from carbon monoxide present in huge clouds both in and between the galaxies. Altogether these clouds contain several billion solar masses worth of gas which has never been viewed before.

Telescoping

Posted in The Universe and Stuff with tags , , , , , on October 2, 2011 by telescoper

I stumbled upon the following cartoon on Youtube and, since it’s about a mad astronomer, I thought I’d post it here.

It strikes me how  comic depictions of astronomical observatories, such as the example on the left,  always seem to show the telescope pointing out of the dome like the barrel of a gun poking out of a turret, which they never do. I venture to suggest that a great many members of the general public think that’s how they work also. I wonder why?

Perhaps it’s connected with the origins of the verb form of telescope which the OED gives as

a. trans. To force or drive one into another (or into something else) after the manner of the sliding tubes of a hand-telescope: usually said in reference to railway carriages in a collision. Also fig. to combine, compress, or condense (a number of things) into a more compact or concise form; to combine or conflate (several things, or one thing with another); to shorten by compression.

b. intr. To slide, run, or be driven one into another (or into something else); to have its parts made to slide in this manner (see quot. 1882 for telescoping n. and adj. at Derivatives, s.v. telescoping below); to collapse so that its parts fall into one another (quot. 1905).

The inference being that large astronomical telescopes must extend in the same way as the much smaller hand-held variety. Anyway, this idea is taken to a ludicrious extreme in the cartoon, with hilarious consequences…

 

Euclid Alone Has looked On Beauty Bare

Posted in Euclid, Poetry, The Universe and Stuff with tags , , on September 25, 2011 by telescoper

Euclid alone has looked on Beauty bare.
Let all who prate of Beauty hold their peace,
And lay them prone upon the earth and cease
To ponder on themselves, the while they stare
At nothing, intricately drawn nowhere
In shapes of shifting lineage; let geese
Gabble and hiss, but heroes seek release
From dusty bondage into luminous air.
O blinding hour, O holy, terrible day,
When first the shaft into his vision shone
Of light anatomized! Euclid alone
Has looked on Beauty bare. Fortunate they
Who, though once only and then but far away,
Have heard her massive sandal set on stone.

by Edna St Vincent Millay (1892-1950)

Neutrinos on Speed

Posted in The Universe and Stuff with tags , , , on September 23, 2011 by telescoper

The internet, twitterdom, blogosphere, and even the mainstream media are all alive today with wild speculations about a curious claim that neutrinos might travel faster than light.

If you’re interested in finding the source of this story, look at the arXiv paper here. I haven’t got time to go through the paper in detail, but I think it must be an instrumental artefact or some other sort of systematic error.

One major reason for doubting the veracity of the claim that neutrinos travel faster than light is provided by astronomical observations. Neutrinos produced by the explosion of Supernova SN1987a were detected when it went boom in 1987, approximately three hours before the visible light from SN 1987A reached the Earth.

The few hours delay between neutrinos and photons is explained by the fact that neutrino emission occurs when the core of the progenitor star collapses, whereas visible light is released only when a shock wave reaches the surface of the imploding object. Three different experiments detected (anti)neutrinos: Kamiokande II found 11 , IMB 8 and Baksan 5, in a burst lasting less than 13 seconds.

If the time delay reported by the OPERA detector over the distance between CERN and Gran Sasso were extrapolated to the distance between Earth and SN1987a then the neutrinos should have arrived not a few hours early, but a few years, and there would not have been coincident arrivals at the different detectors on Earth.

Do neutrinos go faster than light?
Some physicists think that they might.
In the cold light of day,
I am sorry to say,
The story is probably shite

UPDATE: Now that I’ve read the paper let me point out that the OPERA result is essentially

δv/c = (2.48 ± 0.28(stat) ± 0.30(syst)) × 10-5,

whereas the constraints from Supernova 1987a work out to be   δv/c < 2 × 10-9 for  neutrino energies of 10 MeV. See the comments below for discussion.

I’ll also mention at this point that the analysis done in the paper is entirely based on frequentist statistics. Somebody needs to do it properly.

What’s the Matter?

Posted in The Universe and Stuff with tags , , , , , on September 19, 2011 by telescoper

I couldn’t resist a quick comment today on a news article to which my attention was drawn at the weekend. The piece concerns the nature of the dark matter that is thought to pervade the Universe. Most cosmologists believe that this is cold, which means that it is made of slow-moving particles (the temperature of  a gas being related to the speed of its constituent particles).  They also believe that it is not the sort of stuff that atoms are made of, i.e. protons, neutrons and electrons. In particular, it isn’t charged and therefore can’t interact with electromagnetic radiation, thus it is not only dark in the sense that it doesn’t shine but also transparent.

Cold Dark Matter (CDM) particles could be very massive, which would make them much more sluggish than lighter ones such as neutrinos (which would be hot dark matter), but there are other, more complicated, ways in which some exotic particles can end up in a slow-motion state without being massive.

So why do so many of us think the dark matter is cold? The answer to that is threefold. First, this is by far the simplest hypothesis to work on. In other words, good old Occam’s Razor. It’s simple because if the dark matter is cold there is no relevant physical scale associated with the speed of the particles. Everything is just dominated by the gravity, which means there are fewer equations to solve. Not that it’s exactly easy even in this case: huge supercomputers are needed to crunch the numbers.

The second reason is that particle physics has suggested a number of plausible candidates for non-baryonic candidates which could be cold dark matter particles. A favourite theoretical idea is supersymmetry, which predicts that standard model particles have counterparts that could be interesting from a cosmological point of view, such as the fermionic counterparts of standard model bosons. Some of these candidates could even be produced experimentally by the Large Hadron Collider.

The final reason is that CDM seems to work, at least on large scales. The pattern of galaxy clustering on large scales as measured by galaxy redshift surveys seems to fit very well with predictions of the theory, as do the observed properties of the cosmic microwave background.

However, one place where CDM is known to have a problem is on small scales. By small of course I mean in cosmological terms; we’re still talking about many thousands of light-years! There’s been a niggling worry for some time that the internal structure of galaxies, especially in their central regions,  isn’t quite what we expect on the basis of the CDM theory. Neither do the properties of the small satellite galaxies (“dwarfs”) seen orbiting the Milky Way seem to match what what we’d expect theoretically.

The above picture is taken from the BBC website. I’ve included it partly for a bit of decoration, but also to point out that the pictures are both computer simulations, not actual astronomical observations.

Anyway, the mismatch between the properties of dwarf galaxies and the predictions of CDM theory, while not being exactly new, is certainly a potential Achilles’ Heel for the otherwise successful model. Calculating the matter distribution on small scales however is a fearsome computational challenge requiring enormously high resolution. The disagreement may therefore be simply because the simulations are not good enough; “sub-grid” physics may be confusing us.

On the other hand, one should certainly not dismiss the possibility that CDM might actually be wrong. If the dark matter were not cold, but warm (or perhaps merely tepid), then it would produce less small-scale structure whilst not messing up the good fit to large-scale structure that we get with CDM.

So is the Dark Matter Cold or Warm or something else altogether? The correct answer is that we don’t know for sure, and as a matter of fact I think CDM is still favourite. But if the LHC rules out supersymmetric CDM candidates and the astronomical measurements continue to defy the theoretical predictions then the case for cold dark matter would be very much weakened. That might annoy some of its advocates in the cosmological community, such as Carlos Frenk (who is extensively quoted in the article), but it would at least mean that the hunt for the true nature of dark matter would be getting warmer.

“Cosmic Anomalies” Talk, Copenhagen, August 2011

Posted in Art, Books, Talks and Reviews, Cosmic Anomalies, The Universe and Stuff with tags , , on August 31, 2011 by telescoper

I think I’m getting the hang of this slideshare malarky so I thought I’d try it out by posting the slides I used for my (short) talk at the workshop in Copenhagen I told you about two or three weeks ago. I’m not sure how useful they will be to anyone, as I suppose it will be quite hard to reconstruct the talk using only the small amount of information I bother to put on the slides..

If you’re wondering about the presence of various apparently random works of art then what can I say? I like paintings!

Back to the Drawing Board

Posted in Art, Education, The Universe and Stuff with tags , , , , , , , , , on August 30, 2011 by telescoper

I came across a press release this morning which contains the following

More should be done to encourage students to use their drawing skills in science education, researchers at The University of Nottingham say.

In a paper being published in Science this week, academics say that although producing visualisations is key to scientific thinking, pupils are often not encouraged to create their own drawings to develop and demonstrate their understanding.

In the paper the authors, led by Dr Shaaron Ainsworth in the University’s School of Psychology and Learning Sciences Research Institute, said: “Scientists do not use words only but rely on diagrams, graphs, videos, photographs and other images to make discoveries, explain findings, and excite public interest.

In the light of this I thought it would be topical to post an updated version of an old piece I wrote on the theme of sketching. This is quite a strange subject for me to have picked pick because drawing is something I’m completely useless at, but I hope you’ll bear with me and hopefully it will make some sense in the end. I always thought that drawing was an important and neglected aspect of education, but I hadn’t until today any solid research to back it up!

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What  spurred me on to think about this subject was the exhibit I was  involved with for the  Architecture Biennale in Venice as part of a project called Beyond Entropy organized by the Architectural Association School of Architecture. In the course of researching this project I came across this image of the Moon as drawn by Galileo

This led to an interesting discussion about the role of drawings like this in science. Of course  the use of sketches for the scientific representation of images has been superseded by photographic techniques, initially using film and more recently by digital techniques. The advantage of these methods is that they are quicker and also more “objective”. However, there are still many amateur astronomers who make drawings of the Moon as well as objects such as Jupiter and Saturn (which Galileo also drew). Moreover there are other fields in which experienced practioners continue to use pencil drawings in preference to photographic techniques. Archaeology provides many good examples, e.g.

The reason sketching still has a role in such fields is not that it can compete with photography for accuracy or objectivity but that there’s something about the process of sketching that engages the sketcher’s brain in a  way that’s very different from taking a photograph. The connection between eye, brain and hand seems to involve a cognitive element that is extremely useful in interpreting notes at a later date. In fact it’s probably their very subjectivity that makes them useful.  A thicker stroke of the pencil, or deliberately enhanced shading, or leaving out seemingly irrelevant detail, can help pick out  features that seem to the observer to be of particular significance. Months later when you’re trying to write up what you saw from your notes, those deliberate interventions against objectivity will take you back to what you  saw with your mind, not just with your eyes.

It doesn’t even matter whether or not you can draw well. The point isn’t so much to explain to other people what you’ve seen, but to record your own interaction with the object you’ve sketched in a way that allows you to preserve something more than a surface recollection.

You might think this is an unscientific thing to do, but I don’t think it is. The scientific process involves an interplay between objective reality and theoretical interpretation and drawing can be a useful part of this discourse. It’s as if the pencil allows the observer to interact with what is observed, forming a closer bond and probably a deeper level of understanding patterns and textures. I’m not saying it replaces a purely passive recording method like photography, but it can definitely help it.

I have not a shred of psychological evidence to back this up, but I’d also assert that sketching is very good for the learning process too.  Nowadays we tend to give out handouts of diagrams involved in physics, whether they relate to the design of apparatus or the geometrical configuration of a physical system. There’s a reason for doing this – they take a long time to draw and there’s a likelihood students will make mistakes copying them down. However, I’ve always  found that the only way to really take in what a diagram is saying is to try to draw it again myself. Even if the level of draftsmanship is worse, the level of understanding is undoubtedly better.Merely looking at someone else’s representation of something won’t give your brain as a good a feeling for what it is trying to say  as you would get if you tried to draw it yourself.

Perhaps what happens is that simply looking at a diagram only involves the connection between eye and brain. Drawing a copy requires also the connection between brain and hand. Maybe  this additional connection brings in additional levels of brain functionality. Sketching iinvolves your brain in an interaction that is different from merely looking.

The problem with excessive use of handouts – and this applies not only to figures  but also to lecture notes – is that they turn teaching into a very passive process. Taking notes in your own hand, and supplementing them with your own sketches – however scribbly and incomprehensible they may appear to other people – is  a much more active way to learn than collecting a stack of printed notes and meticulously accurate diagrams. And if it was good enough for Galileo, it should good enough for most of us!

It’s not a planet. It’s a white dwarf. (via Matt Burleigh’s Blog)

Posted in Astrohype, The Universe and Stuff with tags , , , , on August 27, 2011 by telescoper

When is a planet made of diamond not a planet made of diamond?

Perhaps when it’s a White Dwarf?

Perhaps when there’s not a shred of evidence that it’s actually made of diamond?

Yesterday Science announced the amazing discovery of an incredibly dense object that appears to be made of a crystalline form of carbon: possibly, ultra-dense diamond (Bailes et al. 2011, Science, DOI: 10.1126/science.1208890). The object orbits a recently-discovered pulsar, PSR J1719-1438, every two hours and ten minutes. It has a slightly higher mass than Jupiter (technically, its minimum mass), but the lack of evidence for direct interaction w … Read More

via Matt Burleigh’s Blog