Relativity on the human scale


Updating Einstein’s Universe and Magic Universe

Relativity on the human scale

The most gratifying physics I’ve seen for a while comes in today’s Science magazine, from James Chin-Wen Chou and his colleagues in the Time and Frequency Division at the National Institute of Standards and Technology in Boulder, Colorado. They detect well-known effects of relativity on the rate of time passing, but now on the scale of ordinary human activities.

Standard atomic clocks employ microwaves to ensure their regularity, but Chou’s team used laser light in a pair of aluminium-27 optical clocks (invented in 2005), which gives about 100 times better accuracy. In one experiment, they used an electric field to jiggle the aluminium ion at the heart of a clock and showed that time passed more slowly in accordance Einstein’s Special Relativity theory, about the effect of motion on time. The effect of atomic motion as slow as 8 metres per second (about 30 km/h) was detectable.

Raising a clock makes it run a little faster. Credit: Chou et al., Science, 24 September 2010 – see reference.

Especially pleasing for me was another experiment, in which one clock was jacked up just 33 cm relative to the other. The clock gaining height ran faster because it was further from the Earth’s centre of gravity, and the gravitational field was slightly weaker, in accordance with General Relativity. As the change in clock rate was only about 40 parts in a billion billion (1018), its detection was a tour de force for the NIST team.

This effect of altitude on time was the key to the efforts by Martin Freeth of BBC-TV and me to make Einstein’s theory of gravity, General Relativity, comprehensible to the public, in our film “Einstein’s Universe” (1979).

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superatomic circus


Pick of the pics and Updating Einstein’s Universe & Magic Universe

Seeing the superatomic circus

When ultra-cold rubidium atoms club together in the superatoms called Bose-Einstein condensates, they usually make untidy crowds, as on the left. But a team led by Stefan Kuhr and Immanuel Bloch at the Max-Planck-Institut für Quantenoptik in Garching, Germany, brings them to order in a neater pattern, as seen in the middle picture. With more rubidium atoms the superatom grows wider (right). Criss-cross laser beams create a lattice-like pattern of pools of light where the atoms like to congregate. When the laser light’s electric field is relatively weak, the atoms jump (by quantum tunnelling) from one pool to another, creating the usual disorder. A stronger field, as in the central and right-hand images, fixes them in the novel state of matter called a Mott insulator. But atoms can be lost from the condensate, which explains the ring-like appearance on the right. Images from MPQ.

[You’re recommended to click on the images for a better view]

Single atoms are located at the sites indicated by circles. Fig. 3 in Nature paper, Sherson et al. see ref.

What’s new here, in an advance online publication in Nature,  is not the creation of these kinds of  superatoms but the German team’s success in imaging them, with a specially developed microscope that picks up fluorescence from the atoms caused by the cooling process. In the image on the right individual atoms are pinpointed.

It’s exciting stuff, because we’re probably seeing the dawn of a new technology – after electronics comes “atomics”. If individual atoms in a superatom can be manipulated, they might be used to carry “addressable” information in an atomic computer.

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What did Hawking discover?


Updating Einstein’s Universe and Magic Universe

What did Stephen Hawking discover?

Stephen Hawking. Photo: Channel 4

We’re so used to it, we’re not surprised to see an elderly gentleman immobile in a wheelchair, his lips hardly moving, performing for most of this week as the host presenter of Channel 4 TV’s five-part history-of-science series “Genius of Britain”. Like the footballer David Beckham or the actress Joanna Lumley, the theoretical physicist Stephen Hawking is now a national treasure. And with his voice synthesiser he can seem like a visitor from outer space, setting us earthlings right about this and that.

But I’m irritated by the implication in the last programme, which I’ve just watched, that Hawking himself was a primary advocate of the Big Bang, in opposition to the great Fred Hoyle’s Steady State Theory. No mention of the l’atome primitif of the Belgian cosmologist Georges Lemaître in 1927, but he was a Catholic priest and perhaps inadmissible to Hawking’s co-presenter Richard Dawkins. No mention either of Martin Ryle, the Cambridge radio astronomer who first showed observational evidence that confounded Hoyle’s expectations.

Three decades ago, the BBC’s Alec Nisbett and I were the first to put Hawking on international television, in a two-hour blockbuster on particle physics, “The Key to the Universe”. At that time, his dreadful disease of nerve and muscle left his mumbles intelligible only those most familiar with him. We added a voice over, as if he were speaking a foreign language.

For Nisbett and me, Hawking was not only an up-and-coming physicist but an image of the frailty of Homo sapiens confronted by a confusing and often violent cosmos. After describing his then-recent suggestion that small black holes could explode, producing new particles, we incited Hawking to use stirring words to climax our show.

The Big Bang is like a black hole but on a much larger scale. By finding out how a black hole creates matter we may understand how the Big Bang created all the matter in the Universe. The singularity in the Big Bang seems to be a frontier beyond which we cannot go. Yet we can’t help asking what lies beyond the Big Bang. Why does the Universe exist at all?

My son Robert is always asking questions. Why this? Why that? Every child does. It is what raises us from being cavemen.

On one view, we are just weak, feeble creatures at the mercy of the forces of Nature. When we discover the laws that govern those forces we rise above them and become masters of the Universe.

Hawking then rose to stardom, taking up Newton’s chair as Lucasian Professor of Mathematics in Cambridge in 1979, and publishing the phenomenal best-seller A Brief History of Time in 1988. He has appeared frequently in “The Simpsons” as well as in scientific documentaries and docu-dramas. He made a sub-orbital spaceflight in 2007 at the age of 65 and during the weightless period he could move freely in his chair for the first time in four decades.

His courage, doggedness and success in the face of a crippling disease has been inspirational to paraplegics the world over. Concern for his predicament has also encouraged many people who might otherwise not have been interested in science to pay some attention to it.

In those respects I’m second to none in my admiration of Hawking. But we’re entitled to ask, as about any other scientist, what his enduring contribution to progress in research has been.

To try to get the tone right, I’ll begin by quoting an eminent but more reclusive theorist, Peter Higgs of Edinburgh, who saw the need for a particle that would give mass to matter, and how it might work. The race to find the Higgs particle, a.k.a the God particle, is now on, using the most powerful accelerators of our time.

But Higgs found himself in hot water during the Edinburgh Festival of 2002. He attended a dinner party celebrating a play based on the work of Paul Dirac, who predicted the existence of antimatter. It was not surprising that the conversation turned to why the public, who knew about Hawking, had never heard of the more important Dirac.

Thinking the dinner was private, Higgs commented about Hawking: “It is very difficult to engage him in discussion, and so he has got away with pronouncements that other people would not. His celebrity status gives him instant credibility that others do not have.”

Next morning Higgs found his remarks quoted in The Scotsman and repeated widely elsewhere. The shocked reaction confirmed Higgs’s point, that someone considered superlatively brilliant as well as handicapped was supposed to be exempt from the normal give and take with his fellow scientists.

Let’s check what I say about Hawking in Einstein’s Universe and Magic Universe and ask

  • Is it fair?
  • Does it need updating?

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About Einstein’s Universe


Occasional postings will comment on news relating to Einstein’s ideas. This introduction explains my interest.

About Einstein’s Universe

Let’s make relativity plain,” was my answer when BBC-TV in London and WGBH in Boston asked, in 1978, how we should celebrate the centenary of Albert Einstein’s birth in the following year. Not just Special Relativity, high-speed travel and E=mc2. Those are fairly easy to talk about. General Relativity (GR), Einstein’s theory of gravity, was the challenging task.

What spurred me were memories of struggling as a student with GR, taught at Cambridge as a branch of higher mathematics. Also irritation at being told again and again that GR was beyond the grasp of ordinary mortals, six decades after our Albert dreamed it up. He was an intuitive physicist and not a brilliant mathematician. Those fancy equations were supplied by other people. So what were the pictures in his head?

Filming for “Einstein's Universe”: Sidney Drell, John Archibald Wheeler and Peter Ustinov, with a younger Nigel Calder. Photo: Joan Williams, BBC/WGBH

Months of fun followed, in the course of which Martin Freeth, producer-director for the BBC, borrowed the McDonald Observatory in Texas and brought to it the eminent physicists and astronomers who were to explain Einstein’s ideas to a genuine layman. This was the actor Peter Ustinov, who also spoke Einstein’s own words and twice acted the part of a time traveller. Specially made for the programme and flown out from London was a billiard table configured so that a ball representing a planet could orbit in the warped space around the Sun, or fall into a black hole. Read the rest of this entry »