Monday, 2 July 2012

Physics stuff from the week 25/6 - 1/7/12

[video] 'Mysterious noctilucent clouds as seen from the international space station'
"They used to be considered rare, but now the clouds are growing brighter, are seen more frequently, are visible at lower and lower latitudes than ever before, and sometimes they are even appearing during the day."
Noctilucent clouds are also called mesospheric clouds, because they occur in the mesospheric layer of the Earth's atmosphere (above the stratosphere and the troposphere, which we're in)
In the picture, you can see the stratosphere, which is seen as a kind of blurry orange band.
Corinne Mills has some lovely pictures on her Flickr:

By modelling the way that pollutants disperse into the environment, an algorithm can be formulated to work out the source of the pollution.
This can be used to hold businesses to account, for the pollutants that they produce.
'Maths formula leads researchers to source of pollution'

[video] Kasparov, playing the original Turing chess engine, that Turing designed algorithms for, before computers even existed!
Because he wrote it all out on paper, Turing's chess engine only calculates two moves ahead, whereas Kasparov can deal with ten, so it was an easy win for him, but designing the game at all was an incredible achievement.

Mars rocks dated to 3.5 billion years ago, have revealed that, for the first billion years of Mars' existence, there was liquid water on the surface, much like Earth, with most of it presumably coming from comet impacts, like Earth's did.
Because Mars is smaller, its thinner atmosphere meant the water was lost via the solar wind. And that is why the only remaining water is in  the form of ice, at the poles.

'Marine energy doubled by predicting wave power'
Good news, i suppose... but the trouble with wave power is that there isn't much 'free energy' in it. Waves are powered by wind, which is powered by convection currents in the atmosphere, which is powered by heating from the sun's light.
Most of the 'free energy' that we can access is going to come from solar, and then wind -- we should concentrate on them.
There're bigger problems with other sources of renewable power, though -- hydro power, for example, displaces communities and potentially damages ecosystems

The Earth's oldest asteroid impact crater on record, has been discovered in Greenland. The crater was left ~3 billion years ago.
There are plenty of craters older than 4 billion years on the moon, but Earth's atmospheric weathering, and geological activity, means there are no other known craters older than 2 billion years, because their marks have been wiped off the geological records.

[video] 'Acoustic tweezers capture tiny creatures with ultrasound'
Acoustic tweezers can trap objects from the size of a solitary cell, to tens of thousands of cells, by using nothing more than sound.
To understand how this works, you have to know that sound is made of longitudinal pressure waves - air (or whatever medium the sounds is passing through) moving back and forth, due to pressure fluctuations.
When a wavefront hits an air particle, it gets pushed forwards, and then pulled backwards, so that the region around the particle is temporarily at a higher pressure than the surrounding air.
When we hear sounds, we hear these pressure waves hitting our eardrums - all the air in between can stay almost exactly where it is, but the sound can propagate for miles, for us to hear it.
When two sources of sound are used, a standing wave can form, where high-pressure regions overlap, and can appear static, or be moved around, as the direction of the waves are changed.
The waves can be used as a kind of acoustic wall, forcing objects to stay on one side of them.
Acoustic tweezers work by using sound waves as acoustic versions of the physical edges of real tweezers, and can be used to push small objects around.
Light tweezers precede this technology, but are far more energy intensive, and so have a tendency to fry the object! But the small wavelength of light makes it possible to use LASER tweezers to push even tinier particles around

[video] 'Gecko-like tape holds up 42-inch TV'
By mimicking the technique that geckos use to grip onto surfaces (a vast surface area on each pad, utilising Van Der Waal's forces), these researchers have managed to produce a tape with immense holding strength, but leaves no residue whatsoever!

'Shaking metallic grains turns them into tunable laser'
"Putting a jar full of metal beads on a subwoofer makes more than just a rattle. Add light and it can become a laser that changes frequency when the beads are shaken harder. Such a tunable laser could lead to crisper projected images and help unlock the mysterious behaviour of granular materials, seen in sand castles, dunes and avalanches."

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