Wednesday, 10 June 2009

Hummingbirds are the fastest animals on Earth

Relative to their body size. Which completely changes everything. According to the Guardian

They can cover more body lengths per second than any other vertebrate and for their size can even outpace fighter jets and the space shuttle

Which is nice, and the high speed photo is beautiful. But it's not really the same is it? In fact the space shuttle statistic sort of makes it seem silly. All the other important numbers, apart from velocity, don't scale with the animal size. The friction, reaction time, not least the speed of sound. It doesn't help me imagine what it feels like to be a hummingbird.

It's somewhat similar to all those statistics you see about insects. Fleas jumping hundreds of times their height and ants carrying many times their body weight. If you had a giant ant I doubt this strength thing continue, the strength of skeletons and legs just don't scale with height.

The dive tops out at 60mph which is pretty impressive, I'd love to know it in perspective with the reaction times of the birds. How does 60mph feel to them? Apparently at the bottom of the dive

the hummingbirds experienced an acceleration force nearly nine times that of gravity, the highest recorded for any vertebrate undergoing a voluntary aerial manoeuvre, with the exception of jet fighter pilots. At 7g, most pilots experience blackouts.

That's definitely cool. So long as by g they don't mean in units of bird length again. Anyway, don't want to be too grouchy, the photo is excellent - enjoy.

Photo by Christopher J. Clark and Teresa Feo/UC Berkeley

Saturday, 6 June 2009

Daisy world

A bit lazy linkage here. I went to a talk a while ago by Graeme Ackland from Edinburgh about Daisy World. It's not new, I think it's been around since the 80s, but it is quite cool. It's a really simple model of a planet where the climate conditions (here just the temperature) and the living organisms on the planet feed back to one another.

On Daisy World there are only daisies, there are a million extensions where they have forests and animals and all sorts. I think the simplest model gives the nicest story. This page gives a nice explanation and it has a java applet that you can play with - this is the best bit.

My extremely brief explanation is that there are white daisies and black daisies. White daisies cool down their environment, black daisies heat it up. If they get too hot or cold they die. Then there's a bunch of other parameters: how fast does temperature defuse, rate of daisy mutation, rates for birth and death etc. It's about as simple as it can be, and crucially is simple enough for mathematicians to come up with solutions.

The nice thing is that for reasonable parameters the system pretty much always self regulates. When things are slow to react, mutation rates are low, you get these big mass extinctions followed by regrowth. Really the best way to get a feel for it is to play with the simulations, it's very fun.