Fire a squirt-gun skywards and the liquid stream will start to break up into smaller droplets due to surface tension. Intriguingly, this same behaviour is also observed in flows of sand even though granular matter is thought to be collection of grains that exert no forces on each other. Now — with the help of their $80,000 video camera — physicists in the US have developed an explanation for this puzzling similarity.John Royer and colleagues at the University of Chicago attribute this behaviour to the roughness of individual grains of sand. They propose that coarse surfaces lead to a combination of van der Waals interactions and capillary forces, causing grains to become attracted. Although 100, 000 times weaker than surface tension in liquid, these interactions closely resemble droplet formation in water jets, say the researchers.Recent studies have revealed instabilities in the flow of granular materials but the minuteness of the forces involved have rendered the clusters too short-lived to observe. Royer and his team avoided this problem by combining high-speed photography with sensitive measuring of forces. By “dropping” the camera alongside a stream of sand, they were able to capture high-quality images at 1000 frames per second and record the sand dynamics as it fell a metre in less than a second. “We now have a magnetic release, though at first I literally held it up by and then let go,” John Royer told physics theoryworld.com.

I’ve recently been listening to Bill Bryson’s ‘A Short History of Nearly Everything‘ on audiobook. Superb. It’s simultaneously an overview of the various scientific disciplines and a entertaining history of science, with its many colourful personalities.

I love science and finding out about the world, uncovering mysteries which lead to deeper mysteries. There are so many wonders out there – from the glories of space to the complexity of cells and the magic of quantum particles. As a Christian I love having my brain and imagination stretched, to celebrate and be thankful. There are so many bits of this book where I just went ‘wow’ – and others where I couldn’t wait to ask God what he was up to there!

What comes across in the book most distinctively is Bryson’s wonder – at the universe, our planet and most of all, at life. He seems almost overwhelmed at times by the sheer quantity and adaptability of life, it’s fruitfulness and diversity. Life is everywhere – at least on planet Earth! One of his repeating themes is the fragility of life and the unlikelihood of us being here.  He explains the anthropic principle early in the book (which states that the (or our) universe is necessarily ‘fine-tuned’ to us, else we wouldn’t be here to observe it were so) and he clearly wants to be convinced, but I was surprised how often he emphasises what an amazing number of remarkable coincidences have led to our existence here and now. Again and again he keeps coming across reasons why we shouldn’t be here!

The last chapter of the book is all about the extinctions that mankind has caused and he concludes like this:

I mention all this to make the point that if you were designing an organism to look after life in our lonely cosmos, to monitor where it is going and keep a record of where it has been, you wouldn’t choose human beings for the job.

But here’s an extremely salient point: we have been chosen, by fate or providence or whatever you wish to call it. As far as we can tell, we are the best there is. We may be all there is. It’s an unnerving thought that we may be the living universe’s supreme achievement and its worst nightmare simultaneously.

…If this book has a lesson, it is that we are awfully lucky to be here – and by ‘we’ I mean every living thing. To attain any kind of life at all in this universe of ours appears to be quite an achievement. As humans we are doubly lucky, of course. We enjoy not only the privilege of existence, but also the singular ability to appreciate it and even, in a multitude of ways, to make it better. It is a trick we have only just begun to grasp.

We have arrived at this position of eminence in a stunningly short time. Behaviourally modern humans have been around for no more than about 0.0001 per cent of Earth’s history – almost nothing, really – but even existing for that little while has required a nearly endless string of good fortune.

We really are at the beginning of it all. The trick, of course, is to make sure we never find the end. And that, almost certainly, will require a lot more than lucky breaks.

Bill Bryson in ‘A Short History of Nearly Everything’.

Brookhaven’s National Synchrotron Light Source, we would discover, is just that — a light source. And despite the differences in scale and the methods of production, it isn’t so different from the studio lights used by photographers. In each case, the way to get the best image is to shine a really bright light on the subject and take a picture of it. Indeed, the only respect in which the light source’s name can be misleading is that it does not confine itself to the visible light spectrum, but uses everything between infrared and x-rays.

A view of the workspaces surrounding the smaller ring at Brookhaven's National Synchrotron Light Source

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I’m not sure what to do with time
that odd fluid thing
that floats by,

that tempts and stretches
Distorts and reminds.

Is it possible?
I die,
I’ll meet my uncle there.
and he’ll say,
he just arrived!

Or is it some strange
physical ruler
a Planck’s length
I can’t divide,

Invented on purpose,
to keep our brains from bursting?

27 June 09

Scientists are coming ever closer to understanding the cellular navigation tools that guide birds in their unerring, globe-spanning migrations.

The latest piece of the puzzle is superoxide, an oxygen molecule that may combine with light-sensitive proteins to form an in-eye compass, allowing birds to see Earth’s magnetic field.

“It connects from the subatomic world to a whole bird flying,” said Michael Edidin, an editor of Biphysical Journal, which published the study last week. “That’s exciting!”

The superoxide theory is proposed by Biophysicist Klaus Schulten of the University of Illinois at Urbana-Champaign, lead author of the study and a pioneer in avian magnetoreception. Schulten first hypothesized in 1978 that some sort of biochemical reaction took place in birds’ eyes, most likely producing electrons whose spin was affected by subtle magnetic gradients.

In 2000, Schulten refined this model, suggesting that the compass contained a photoreceptor protein called cryptochrome, which reacted with an as-yet-unidentified molecule to produce pairs of electrons that existed in a state of quantum entanglement — spatially separated, but each still able to affect the other.

According to this model, when a photon hits the compass, entangled electrons are scattered to different parts of the molecule. Variations in Earth’s magnetic field cause them to spin in different ways, each of which leaves the compass in a slightly different chemical state. The state alters the flow of cellular signals through a bird’s visual pathways, ultimately resulting in a perception of magnetism.

Far-fetched as it sounds, subsequent research from multiple groups has found cellular evidence of such a system. Molecular experiments suggest that it’s indeed sensitive to Earth’s geomagnetics, and computational models suggest a level of quantum entanglement only dreamed of by physicists, who hope to use entangled electrons to store information in quantum computers.

But though cryptochrome is likely part of the compass, the other part is still unknown. In April, another group of magnetoreception researchers showed that oxygen could interact with cryptochrome to produce the necessary electron entanglements. Schulten’s latest proposed role for superoxide, an oxygen anion found in bird eyes, fits with their findings.

Edidin cautioned that “this is still not an experimental demonstration. It’s a possibility.”

As for the perceptual result of the compass, it remains a mystery. Some researchers think birds might see a dot at the edge of their vision, swiveling according to the direction they’re facing. Others think it might produce effects of color or hue. Perhaps migrating birds fly towards the light.

via Reverse-Engineering the Quantum Compass of Birds | Wired Science | Wired.com.

I’ve always been impressed when my companions manage to swat mosquitoes and other annoying flying creatures around them. I’m especially impressed when the move I coin the “gungfu claw grab” is employed — one hand to grab and crush the flying abomination in the palm. In a midst of a very serious interview with CNBC, Obama was accosted by a fly and with a combination of quick reflexes and strategy, the commander-in-chief managed to send the fly plummeting to its death on the studio floor.

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