Does anyone remember the sonoluminescent Pistol shrimp? I found out about these for the first time when visiting a lab in Kosice. One swift, loud click of their claws blasts the water so fast that it creates a 60 mph cavitation bubble, collapsing rapidly to generate a temperature of around 5,000 K and emitting a burst of light in the process. Scientists (including those in Kosice) are still studying sonoluminescence in the lab by producing stable cavitation bubbles, which oscillate on an acoustic standing wave, and measuring the tiny pulses of light emitted each time the bubble collapses. The exact process by which the light is produced is still in question! Temperatures of up to 20,000 K have been reached in these bubbles. It’s no cold fusion (it was originally thought the temperatures could reach that required for thermonuclear fusion…not quite!) and it’s not quite the trillions of degrees that are seen at ALICE at the LHC in lead collisions…but it’s still impressive!
Well, last night I was watching QI and found out about Mantis shrimp (not actually shrimp). These creatures are the boxing-ring equivalent of the Pistol shrimp, in that their left hook can deliver a whack with the acceleration of a 0.22 calibre bullet, creating a cavitation bubble on impact (which then collapses, giving the victim a second blow from the shock wave).
They also have arguably the most complicated eyes of any creature on the planet, with more photoreceptors than any other eyes. They have hyperspectral vision – the ability to see from UV through visible to IR light all at once. They can distinguish between 100,000 different colours, 10 times more than a human eye can. Each eye can move independently on a strange alien-like stalk. And to top it all off, they are the only known animal to be able to see circularly polarised light, and can convert this into linearly polarised light and vice versa. Not only are they superior to other eyes in nature but they are giving current imaging technology a run for its money, and are inspiring new developments in cameras, CDs and DVDs and so on.
QI also enlightened me to the cleverness of the Venus Flytrap, using a technique that is crucial for particle physics – coincidence triggering. In order for the trap to close, two “signals” (stimulation of “trigger” hairs) must be seen within a time-frame of around 35 seconds. This time constraint increases the likelihood that the two stimulations came from the same source (hopefully something alive and juicy). This makes it more probable that the signal is coming from a lingering bug, rather than a falling bit of dirt or drop of water. What the plant is doing is “enhancing its sample” – selecting mostly on what is likely to be food, so that it is unlikely to waste most of its time with its jaws around a bit of sand while prey passes it by.
The “trigger” works in a very clever way – each stimulation produces an electrical signal of a certain amplitude. There is an internal threshold, above which a signal would cause the trap to close, but this single signal is not enough. The charge dissipates over time in such a way that if another signal is seen within 35 seconds, the threshold will be exceeded, but after that it won’t be enough.
The “trigger” is a crucial tool when looking for a needle in a haystack in science – if what you are looking for is rare, or if there is quite a lot of junk that you don’t want, then it helps to have some selections on what “events” to choose. This is because while your electronics is busy looking at an event, it isn’t generally able to look at any others, (although complex trigger systems like the one in ATLAS can hold onto multiple events while processing a decision on whether to keep them). You don’t want to be busy looking at something boring when what you really want comes along and you miss it. This is just like the Flytrap – it doesn’t want to waste time and energy with its mouth around something inedible, especially if it means possibly missing the opportunity for food.
The “coincidence” trigger – a trigger requiring two or more signals within a certain time period – is one of the most important kinds of trigger particle and nuclear physicists use in their experiments. Let’s take for example an experiment that uses accelerated beams of gold nuclei incident on a thin film of gold, where the objective is to identify events where two gold nuclei collided (this is what the ASYEOS experiment in May was doing!) Detectors surround the target and can measure particles that pass through them and deposit energy. How could one tell the difference between a gold-gold collision and, say, a cosmic event from space, or a noisy detector module? Using coincidence triggering, one can require that more than one detector saw a signal at the same time, or that, say, the near-side of the detector saw a signal and, very soon after, the far-side of it saw one in a similar longitudinal position. Of course, this means the timing of the detectors has to be synchronised, and this is affected by things like cable lengths as well as the positions and responses of the detectors.
Another notable part of QI, but one which made my head spin and my stomach churn, was the description of a Brazilian ant-zombifying fungus. Spores are released from the fungus and attach themselves to ants, find a way inside their bodies and then the fungus begins to grow. Chemicals released by it send the ant crazy and it wanders off, climbs a tree and clamps on desperately to vegetation perfect for the fungus to grow on, before dying. Here, the fungus can grow, living off the ant’s body and releasing spores again for the cycle to continue. How horrible. Apparently there is a whole family of mind-controlling fungi…I am amazed as to how this can work, and how something might have evolved to do this. On the off-chance anyone with some neurological or mycological expertise is reading this, I’d love to know more!