Where Grey Matter meets Dark Matter

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Episode 15 - 4 July 2009
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"Johnny, please sit down! No, don't pull her hair. And put those books down...don't throw them out the window! That's it, I'm calling the principal - and my therapist."

Attention Deficit Hyperactivity Disorder (ADHD) kids, often boys, can be the bane of a teacher's existence. Their distracting, and sometimes violent, behaviour can destroy any sort of learning environment. Although it is somewhat of a nebulous diagnosis, there is no doubt that some kids just cannot concentrate for any length of time.

For a while, we've known that ADHD has something to do with dopamine, which is a neurotransmitter and neurotransmitter, with chemical formula C6H3(OH)2-CH2-CH2-NH2. Dopamine plays a role in a lot of your bodily functions, among them motivation, pleasure, mood, attention and learning. (It's also the chemical involved in bruising fruit.) A lot of the commonly addictive drugs like cocaine, nicotine and amphetamines give a boost to the dopamine level in the user's brain, possibly leading to dependence. This often eventually leads to tolerance (requiring more to get the same effect) and withdrawal when an addict can't get a hit.


Dopamine molecule. Source: Wikipedia.

In fact, the most famous treatment for ADHD, methylphenidate (of which Ritalin is a particular brand) is derived from amphetamines. The theory is that by stimulating the production of dopamine, the student won't need to be bad to get the same thrill.


Methylphenidate molecule. Source: Wikipedia.

The latest in the ADHD story is that it might be related to how the person perceives time. Some studies have shown that sufferers might feel like time is dragging so slooowwllly, and so they get bored. In order to alleviate the boredom, they do things to stimulate dopamine production, like destroy their textbooks, which is probably pretty fun.

But it looks more complicated than just that - it seems that dopamine (or at least methylphenidate) is also playing a part in the time perception. Kids with ADHD seemed to have abnormal brain activity in the area that controls the feeling of time, but when medicated with Ritalin, their brain activity and time perception were no different to other kids.

This ties in with what most people already know - time flies when you're having fun. The feeling of time dragging only seems to occur when you've got nothing to do, or when you hate what you are doing. So abnormal dopamine levels might lead to ADHD kids feeling completely unstimulated for what feels like ages.

But all this typing is getting boring. Let's watch some YouTube. This one might not be ADHD, but these kids have certainly got something else going on upstairs.

Refs:

  • The Onion is doing its best to help.
  • Time perception and ADHD in New Scientist.
  • Here's the research that the New Scientist article was talking about: Rubia K., Halari R., Christakou A. & Taylor E. 2009. Impulsiveness as a timing disturbance: neurocognitive abnormalities in attention-deficit hyperactivity disorder during temporal processes and normalization with methylphenidate. Philosophical Transactions of the Royal Society B 364, 1919-1931.
  • Time perception may also have a role in schizophrenia: Lee K.-H., Bhaker R. S., Mysore A., Parks R. W., Birkett P. B. L. & Woodruff P. W. R. 2009. Time perception and its neuropsychological correlates in patients with schizophrenia and in healthy volunteers. Psychiatry Research 166, 174183.


BETA:

Surely humans have always wondered about aliens. Ever since we had the ability to guess and make predictions, people must have been looking at the night sky and imagining other civilizations, more or less like ours, somewhere out there.


The Milky Way, looking awesome. This is a patch of sky near the Southern Cross.
Credit: Greg Bock. Source: www.nasaimages.org.

This must have been what Frank Drake was thinking when he began scanning the sky for signals that would indicate intelligent life in 1960, kicking off the Search for Extraterrestrial Intelligence (SETI) project.


This is the telescope at Green Bank, West Virginia, USA that Drake used in 1960.
Source: Harvard-Smithsonian Center for Astrophysics

And it's not just listening: Drake and his friend Carl Sagan used the giant Arecibo telescope to send a message out into space in 1974, towards the M13 globular cluster, a short 25,000 light years away.


The Arecibo message. This is the message that Drake and Sagan
sent out on its long journey in 1974. Source: Wikipedia.

The guiding principle for SETI is the Drake Equation: an equation that tells you the number of intelligent civilizations out there that we might possibly detect, and maybe even communicate with. This is what it looks like:

N = R x Fp x ne x Fl x Fi x Fc x L

(This version is taken from Wikipedia, but they're all just variations on the same theme)

This is what all the factors mean:

  • N is the number that we are really interested in. It's the number of civilisations that we can detect, or maybe even communicate with. It's probably restricted to only our own galaxy, since civilizations in other galaxies are 'probably' too far away to ever meet us.
  • R is the (average) rate at which stars are formed. You gotta have stars to generate energy for life to exist.
  • Fp is the proportion of those stars that have planets. This assumes that life can't exist in the sun, or just floating free in space.
  • If a star has planets, then ne tells you the number of planets it will have (on average) that can support life. More nice planets means more chances for life to get going.
  • But even if a planet is the best place in the universe for life, it still might not have any. Fl tells you the fraction of those nice planets that actually get life. This is probably the single biggest error bar in the calculation.
  • Fi is the proportion of planets with life that get intelligent life.
  • Fc is that proportion of planets with intelligent life that get technologically-advanced civilizations - the sort that we might be able to get signals from.
  • L is the (average) lifespan of these technical civilizations. The longer they stick around, the more chance we have of spotting them.
(For those of you into dimensional analysis, notice that the units all work out.)

Now it's a simple matter of plugging in the numbers on the right hand side to find out how many civilizations there are out there. What's that you say, you don't know the numbers to plug in? And that, of course, is the big problem. Nobody knows.

Sure we can make good guesses about some of them, like the rate of star formation, and the number of stars that have planets, and how many planets. But when it comes to putting down values for the things that relate to life - well we have a sample size of roughly 1 planet. Well not quite, since according to most definitions of life, we can say that there are probably only 2 or 3 planets that could have sustained life in out solar system. But what about moons? Titan, Callisto, Enceladus, Triton - these and others have been suggested as places we might look for existing (or extinct) life. And who knows, maybe gas giants could support some weird form of life.

And this is the crux of the problems with the Drake equation - it's all based on seemingly baseless assumptions. We know so little about the necessary conditions for life, or for that matter, what even constitutes life, that the equation is little more than a guide for future research. In fact, (according to Wikipedia) that's exactly what Drake himself said: the Drake Equation "is just a way of organizing our ignorance on the subject".

But hey, it gives you something to talk about. And just imagine all those hot alien babes.

Refs:

  • The Kepler mission is trying to find other earths 'out there'.
  • Here's Seth Shostak telling us that detection of ET is right around the corner.
  • Dean, T. (2007), "Are we alone?" Cosmos Magazine, 14, Apr/May 2007.
  • This xkcd comic raises the discussion out of the gutter.

Quiz:

Here's a Youtube vid about the moonwalking bird (the Pipra mentalis).

And in case you think this might be YouTube hoaxterism, here's some more from the Journal of Experimental Biology (but don't groan if you might need a subscription, get a better library)


Mistakes we shouldn't have made but did anyway:

  • The Wow! signal was received on 15 August 1977. As you can see by the picture, they were pretty excited about it. Although official CTP explanation is that the signal was a divine response to the birth of our saviour Anthony a few days before.

  • Here it is. Woah! Source: Wikipedia.

  • Ok, so Anthony might have over-reached when he said Bubbles could moonwalk; this is as close as he seems to get.


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