I forgot to mention that, at the end of my talk on Monday evening, a gentleman in the audience who is apparently a regular reader of this blog asked if I was aware of that composer György Ligeti had written a piece of music called Volumina inspired by the Big Bang. I was indeed aware of this piece, and have a recording of it, but his question gives me the excuse to post a version here. I’m sure at least some of you will have heard some of it before, in fact, as an excerpt featured in the original radio series of The Hitchhiker’s Guide to the Galaxy which I listened to on the wireless many moons ago.
You might find Volumina a bit perplexing, but I can tell you that in surround sound with the volume up it’s absolutely amazing. My neighbours clearly agree, and were banging on the wall last night to show their appreciation.
I was too tired last night to do anything but vegetate, and in the course of doing that I found a box of unsorted old photographs which made me all nostalgic. Here are some that reminded me of old friends. I don’t remember exactly when they were taken (probably in 1990), when I was visiting SISSA in Trieste. I don’t remember which particular trip it was or what paper resulted from it but I went there a number of times and had great fun. The first picture was taken in the office of Manolis Plionis, who is seated at the window facing the camera. In those days Manolis had a big motorbike, and I had a number of near-death experiences as his pillion passager on various high speed trips around Trieste, usually along the Strada Costiera…
To the right of Manolis is Francesco Lucchin (standing) with whom I co-authored a textbook on cosmology; Francesco sadly died in 2002. Seated in front of Francesco is Sabino Matarrese and at the computer is Lauro Moscardini.
I think these next two were taken over the nearby border in Slovenia at the end of a dinner but that is relying on my memory which, at my age, is not very reliable. Me and Lauro on the left with Sabino laughing at us. As usual.
And this was the same evening. On Francesco’s right is Paolo Catelan, with whom I also wrote a paper, but I have now completely lost touch with him…
Everyone looks very youthful in these pictures, but it was 20 years ago .. and we’ve all passed a lot of water since then.
Neither the time nor the energy to post anything other than a bit of music, so I’ve picked a track someone happens to have posted on Youtube. I have Laughin’ to Keep from Cryin’ the original vinyl LP on the Verve label, but it’s still waiting for me to transfer it to digital. I love this record so much because it’s so joyful and at the same time so tragic. There’s some wonderfully upbeat stuff from the two trumpeters, the great Harry “Sweets” Edison (whom I’ve had the privilege to hear play live), who opens the piece, and then the perhaps even greater Roy Eldridge, but it’s also one of the last recordings made by legendary saxophonist Lester Young who was terminally ill with cancer at the time of this session in February 1958; he died just a year later. His formerly smooth tenor tone now ragged, barely able to stand or hold the saxophone, and playing almost in slow motion, he nevertheless manages to cast his fading light over the latter part of this tune and conjure up something quite magical. The other members of the band are Herb Ellis (guitar), Hank Jones (piano), George Duvivier (bass) and Mickey Sheen (drums) and this track is called Romping.
It’s National Science and Engineering Week this week and as part of the programme of events in Cardiff we have an open evening at the School of Physics & Astronomy tonight. This will comprise a series of public talks followed by an observing session using the School’s Observatory. I’m actually giving a (short) talk myself, which means it will be a long day, so I’m going to save time by recycling the following from an old blog post on the subject of my talk.
As you probably know the Big Bang theory involves the assumption that the entire Universe – not only the matter and energy but also space-time itself – had its origins in a single event a finite time in the past and it has been expanding ever since. The earliest mathematical models of what we now call the Big Bang were derived independently by Alexander Friedman and George Lemaître in the 1920s. The term “Big Bang” was later coined by Fred Hoyle as a derogatory description of an idea he couldn’t stomach, but the phrase caught on. Strictly speaking, though, the Big Bang was a misnomer.
Friedman and Lemaître had made mathematical models of universes that obeyed the Cosmological Principle, i.e. in which the matter was distributed in a completely uniform manner throughout space. Sound consists of oscillating fluctuations in the pressure and density of the medium through which it travels. These are longitudinal “acoustic” waves that involve successive compressions and rarefactions of matter, in other words departures from the purely homogeneous state required by the Cosmological Principle. The Friedman-Lemaitre models contained no sound waves so they did not really describe a Big Bang at all, let alone how loud it was.
However, as I have blogged about before, newer versions of the Big Bang theory do contain a mechanism for generating sound waves in the early Universe and, even more importantly, these waves have now been detected and their properties measured.
The above image shows the variations in temperature of the cosmic microwave background as charted by the Wilkinson Microwave Anisotropy Probe about a decade years ago. The average temperature of the sky is about 2.73 K but there are variations across the sky that have an rms value of about 0.08 milliKelvin. This corresponds to a fractional variation of a few parts in a hundred thousand relative to the mean temperature. It doesn’t sound like much, but this is evidence for the existence of primordial acoustic waves and therefore of a Big Bang with a genuine “Bang” to it.
A full description of what causes these temperature fluctuations would be very complicated but, roughly speaking, the variation in temperature you see in the CMB corresponds directly to variations in density and pressure arising from sound waves.
So how loud was it?
The waves we are dealing with have wavelengths up to about 200,000 light years and the human ear can only actually hear sound waves with wavelengths up to about 17 metres. In any case the Universe was far too hot and dense for there to have been anyone around listening to the cacophony at the time. In some sense, therefore, it wouldn’t have been loud at all because our ears can’t have heard anything.
Setting aside these rather pedantic objections – I’m never one to allow dull realism to get in the way of a good story- we can get a reasonable value for the loudness in terms of the familiar language of decibels. This defines the level of sound (L) logarithmically in terms of the rms pressure level of the sound wave Prms relative to some reference pressure level Pref
L=20 log10[Prms/Pref]
(the 20 appears because of the fact that the energy carried goes as the square of the amplitude of the wave; in terms of energy there would be a factor 10).
There is no absolute scale for loudness because this expression involves the specification of the reference pressure. We have to set this level by analogy with everyday experience. For sound waves in air this is taken to be about 20 microPascals, or about 2×10-10 times the ambient atmospheric air pressure which is about 100,000 Pa. This reference is chosen because the limit of audibility for most people corresponds to pressure variations of this order and these consequently have L=0 dB. It seems reasonable to set the reference pressure of the early Universe to be about the same fraction of the ambient pressure then, i.e.
Pref~2×10-10 Pamb
The physics of how primordial variations in pressure translate into observed fluctuations in the CMB temperature is quite complicated, and the actual sound of the Big Bang contains a mixture of wavelengths with slightly different amplitudes so it all gets a bit messy if you want to do it exactly, but it’s quite easy to get a rough estimate. We simply take the rms pressure variation to be the same fraction of ambient pressure as the averaged temperature variation are compared to the average CMB temperature, i.e.
Prms~ a few ×10-5Pamb
If we do this, scaling both pressures in logarithm in the equation in proportion to the ambient pressure, the ambient pressure cancels out in the ratio, which turns out to be a few times 10-5
With our definition of the decibel level we find that waves corresponding to variations of one part in a hundred thousand of the reference level give roughly L=100dB while part in ten thousand gives about L=120dB. The sound of the Big Bang therefore peaks at levels just a bit less than 120 dB. As you can see in the Figure to the left, this is close to the threshold of pain, but it’s perhaps not as loud as you might have guessed in response to the initial question. Many rock concerts are actually louder than the Big Bang, so I suspect any metalheads in the audience will be distinctly unimpressed.
A useful yardstick is the amplitude at which the fluctuations in pressure are comparable to the mean pressure. This would give a factor of about 1010 in the logarithm and is pretty much the limit that sound waves can propagate without distortion. These would have L≈190 dB. It is estimated that the 1883 Krakatoa eruption produced a sound level of about 180 dB at a range of 100 miles. By comparison the Big Bang was little more than a whimper.
PS. If you would like to read more about the actual sound of the Big Bang, have a look at John Cramer’s webpages. You can also download simulations of the actual sound. If you listen to them you will hear that it’s more of a “Roar” than a “Bang” because the sound waves don’t actually originate at a single well-defined event but are excited incoherently all over the Universe.
PPS. If you would like to hear a series of increasingly sophisticated computer simulations showing how our idea of the sounds accompanying the start of the Universe has evolved over the past few years, please take a look at the following video. It’s amazing how crude the 1995 version seems, compared with that describing the new era of precision cosmology.
Let me not to the marriage of true minds Admit impediments. Love is not love Which alters when it alteration finds, Or bends with the remover to remove: O no! it is an ever-fixed mark That looks on tempests and is never shaken; It is the star to every wandering bark, Whose worth’s unknown, although his height be taken. Love’s not Time’s fool, though rosy lips and cheeks Within his bending sickle’s compass come: Love alters not with his brief hours and weeks, But bears it out even to the edge of doom. If this be error and upon me proved, I never writ, nor no man ever loved.
P.S. This is one of over a hundred love sonnets written by Shakespeare to a young man to whom he was deeply devoted. If you think we shouldn’t admit impediments to people in similar relationships nowadays then perhaps you would consider signing the petition organized by the coalition for equal marriage…
And now for something completely different. I was listening to CD Review on Radio 3 yesterday morning and in the course of a fascinating section about new modern classical works, I heard some wonderful music by a Danish composer called Per Nørgård, whose name (pronounced in Danish something like nur-gaw) was quite new to me until then. I’ve spent most of this morning downloading various collections of his music and am now in danger of becoming a Nørgård bore.
Much of Nørgård’s music is based on ideas inspired by fractal geometry and exploits the so-called infinity series, representing a kind of extension of the serial techniques pioneered by such composers as Arnold Schoenberg. One of the great things about Nørgård, however, is that you really don’t need to know about that, or indeed that the following piece was inspired by the Aurora Borealis, in order to enjoy it. This is Nørgård’s Violin Concerto No. 1 Helle Nacht.
I recently received the following email letter, concerning the state of science funding in Spain. As well as passing it on to colleagues I thought I would post it on this blog where it might have wider impact:
Dear colleague,
You probably know very well how the global crisis is affecting southern Europe, and in particular Spain. Some of us are promoting a campaign among the worlwide scientific community to prevent our conservative government from straining even more the science system in Spain, that so many successes has obtained in the last decade, but whose future is now at stake.
In the next few weeks, and contravening recommendation from the European Commission stating that public deficit control measures should not affect Research and Development (R&D) and innovation, the Spanish Government and Parliament could approve a State Budget for 2012 that would cause considerable long-term damage to the already weakened Spanish research system, contributing to its collapse.
There is an open letter that we are sending to distinguished scientists all over the world, including many Nobel Prize Winners and Members of Academies of Science, asking them to sign, support the motion and spread the word:
The “open letter” you can read by clicking on the link contains some interesting – and alarming – information that has serious implications for our colleagues not only in Spain but elsewhere in Europe. Take a look, for example, at the following picture that shows the fraction of GDP being invested in science:
This isn’t just about Spain, although the situation is clearly especially serious for Spanish Science. It’s a timely reminder that the UK is also well below the EU average in terms of science spend. Is it a coincidence that the EU’s worst-performing economies are all on the right of this figure? Is that where we want the UK to be too?
It will be well known to the regular readers of the blog (Sid and Doris Bonkers) that I am not the sort of chap who’s likely to get involved in the PC versus Mac controversy. Except occasionally. And with great reluctance. It doesn’t do any good to take sides in such conflicts. I couldn’t resist passing on this little picture I found in internetland, however, which I know will not upset any Mac users….
P.S. I still think the LHC control room looks like the inside of a betting shop.
Here’s a video, produced by Nature magazine, showing the continuing efforts to clean up.
I’ve been teaching Nuclear Physics this term and while I was talking about chain reactions, neutron capture, control rods and the like, the other day I suddenly realised that the class of twenty-somethings in front of me had all been born after Chernobyl and were probably unaware of just how scary it was at the time. The current generation of students, and those following it, will be among those who are going to have to grapple with a very serious problem as oil and gas supplies dwindle over the next decades. People can make their own mind up about what’s the best way to tackle this crisis, but my view is that at least in the short term we’re stuck with nuclear fission reactors for at least some of our energy needs – with improved energy efficiency and appropriate use of renewable sources helping – until fusion power comes to the rescue.
An interesting email exchange yesterday evening led me to write this post in the hope of generating a bit of crowd sourcing.
The issue at hand concerns the vexed question of the etymology and original meaning of the word “research” (specifically in the context of scholarly enquiry). The point is that the latin prefix re- usually seems to imply repetition whereas the meaning we have for research nowadays is that something new is being sought.
My first thought was to do what I always do in such situations, which is reach for the online edition of the Oxford English Dictionary wherein I found the following:
Etymology: Apparently < re- prefix + search n., after Middle French recerche (rare), Middle French, French recherche thorough investigation (1452; a1704 with spec. reference to investigation into intellectual or academic questions; 1815 in plural denoting scholarly research or the published results of this) … Compare Italian ricerca (1470). Compare slightly later research v.1
Interestingly, my latin dictionary gives a number of words for the verb form of research, such as “investigare”, most of which have recognisable English descendants, but there isn’t a word resembling “research”, or even “search”, so these must have been brought into French from some other source. The prefix re- was presumably added in line with the usual treatment of Latin words brought into French.
Most of the brain cells containing my knowledge of Latin died a long time ago, but I do recall from my school days that the prefix re- does not always mean “again” in that language, and alternative meanings have crept into other languages too. In particular, “re-” is sometimes used simply as an intensifier. I remember “resplendent” is derived from “resplendere” which means to shine (splendere) intensely, not to shine again. Likewise we have replete, which means extremely full, not full again.
This led me to my theory, henceforth named Theory A, that the French “recherche” and the italian “ricerca” originally meant “to search intensely, or with particular thoroughness” as in a scholar poring over documents (presumably including the Bible). Support for this idea can be found here where it says
1570s, “act of searching closely,” from M.Fr. recerche (1530s), from O.Fr. recercher “seek out, search closely,” from re-, intensive prefix, + cercher “to seek for” (see search). Meaning “scientific inquiry” is first attested 1630s…
Being a web source, one can’t attest to its reliability and the dates quoted to differ from the OED, but it shows that at least one other person in the world has the same interpretation as me! However, Iin the interest of balance I should also quote, for example, this dissenting opinion which is also slightly at odds with the OED:
As per the Merriam-Webster Online Dictionary, the word research is derived from the Middle French “recherche”, which means “to go about seeking”, the term itself being derived from the Old French term “recerchier” a compound word from “re-” + “cerchier”, or “sercher”, meaning ‘search’. The earliest recorded use of the term was in 1577.
My correspondent (and regular commenter on here), Anton, suggested an alternative theory which is based on an idea that can be traced back to Plato. This reminded me of the following explanation of the purpose of scholarship by the Venerable Jorgi in Umberto Eco’s novel The Name of the Rose:
..the preservation of knowledge. Preservation, I say. Not search for… because there is no progress in the history of knowledge … merely a continuous and sublime recapitulation.
Plato indeed argued that true novelty and originality are impossible to achieve. In the Dialogues, Plato has Meno ask Socrates:
“How will you look for it, Socrates, when you do not know at all what it is? How will you aim to search for something you do not know at all? If you should meet with it, how will you know that this is the thing that you did not know? “
And Socrates answers:
“I know what you want to say, Meno … that a man cannot search either for what he knows or for what he does not know. He cannot search for what he knows—since he knows it, there is no need to search—nor for what he does not know, for he does not know what to look for.”
Theory B then is that research has an original meaning derived from this strange (but apparently extremely influential) Platonic idea in which “re-” really does imply repetition.
We scientists think of the scientific method as a means of justifying and validating new ideas, not a method by which new ideas can be generated, but generating new ideas is essential if science can be really said to advance. As one article I read states puts it “We aim for new-search not re-search. It is new-search that advances our understanding of how the world works.”
My research suggests that it’s possible that research doesn’t really mean re-search anyway but I can’t say I have any evidence that convincingly favours Theory A over Theory B. Maybe this is where the blogosphere can help?
I know I have an eclectic bunch of readers so, although it’s unlikely that an expert in 16th Century French is among my subscribers, I wonder if anyone out there can think of any decisive evidence that might resolve this etymological conundrum? If so, please let me have your contributions through the comments box.
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With our definition of the decibel level we find that waves corresponding to variations of one part in a hundred thousand of the reference level give roughly L=100dB while part in ten thousand gives about L=120dB. The sound of the Big Bang therefore peaks at levels just a bit less than 120 dB. As you can see in the Figure to the left, this is close to the threshold of pain, but it’s perhaps not as loud as you might have guessed in response to the initial question. Many rock concerts are actually louder than the Big Bang, so I suspect any metalheads in the audience will be distinctly unimpressed.
