Tuesday, March 27, 2012

The case of the drowning crickets

A firebelly toad waiting for a cricket
Our aquatic tank contains many firebelly toads, and each one of them is a voracious cricket eater. A few large rocks in the tank create an island, surrounded by open water. When we place crickets on the rocks, a significant portion of them fall into the water staying there until they drown (or until we rescue them and put them back on solid ground). Are cricket brains so tiny that they don’t realize they can’t breathe, and so don’t pull themselves out of the water, or is something else going on?

I found a nice explanation in an essay by J.B.S. Haldane (1892-1964) ‘On Being the Right Size’:

There is a force which is as formidable to an insect as gravitation to a mammal. This is surface tension. A man coming out of the bath carries with him a film of water of about one-fiftieth of an inch in thickness. This weighs roughly a pound. A wet mouse has to carry about its own weight in water. A wet fly has to lift many times its own weight and, as everyone knows, a fly once wetted by water or any other liquid is in a very serious position indeed. An insect going for a drink is in as great danger as a man leaning out over a precipice in search of food. If it once falls into the grip of the surface tension of the water - that is to say, gets wet - it is likely to remain so until it drowns.

I often swim at lunch. When I’m done I haul myself out of the water and head to the showers without a second thought for the amount of pool water I’m carrying around with me. It’s lucky for me that my size makes me immune to the same surface tension that drowns the unfortunate crickets.

As a tangent: I found an online copy of Haldane's essay here - it's worth reading and not too long.

Thursday, March 1, 2012

Floating Trees

A tree in the forest near my home
Years ago I read C.S. Lewis’s Space Trilogy since I had enjoyed his The Lion, The Witch and The Wardrobe series as a kid. The Space Trilogy books were too weird for me and I can’t remember if I finished all three. What does stick in my memory is one of the settings (on Venus I think, but I could be wrong). The main character ran across surreal floating islands coated in trees and surrounded by water. The movie ‘Avatar’ also brought us tree covered floating islands (this time floating in the air due to a ‘flux vortex’), but the strangest trees I’ve come across are floating on glaciers and they’re real.

A while back, I went to a talk by Hig about his trek with his wife, toddler and baby across Malaspina Glacier (find their blog here). They lived in the wild for two months. Clearly they are somewhat crazy - in a fantastic way, I wish more people took their kids into nature that way. From the video and photos clearly the kids had an awesome time.

Malaspina Glacier sits by the ocean on the southern reaches of Alaska reaching 600m thick in places and covering an area of 3,900 square km. Like many glaciers, this one is shrinking however the most striking feature to my mind is that in places trees grow on it. Trees growing on top of ice - how fabulous is that! Even assuming there is some sort of soil layer buffering the roots from the ice.

Are there other glaciers out there with trees growing on them?