Postby gejyspa » Wed Jan 18, 2012 1:04 pm
Those talks about temperature reminded me of this rant of mine from Monday to my family:
I heard a very cool science story on the radio on the drive in to work about the new Webb space telescope, but the intro made me go gkk! gkk! gkkk! {sound of strangled scream}. It started like this (copied and pasted from their transcript):
"Think about the last time you were cold. As in, teeth-chattering, goosebump-raising, shivering-in-your-boots cold. You were probably outside, and the temperature very well could have been below zero. Washington, D.C.'s lowest recorded temperature is 15 degrees below zero. And in a slightly colder place - such as Alaska -- it's more like 80 below.
But if you take that last number - 80 degrees below zero - and multiply it by five, you'll get an idea of just how cold the James Webb Space Telescope will be after it's launched a million miles from Earth, in the year 2018"
No! No! No! You can't take a temperature number based on a completely arbitrary scale with an arbitrary zero point, and multiply it and have that make any kind of meaning! If you wanted to say, "Now go down another 320 degrees," then yes, that's fine., since everyone has a feel for how much one degree of Fahrenheit feels like (more or less). But multiplication??? Ridiculous. OF course, if you said "The lowest temperature recorded in DC was 444 Kelvin, and in Alaska, it's more like 379 Kelvin, now divide it by 10, and you'll get an idea...." that would be fine also, because here we are measuring an actual scale with some meaning.
On the cool side, the Webb telescope, according to one of the team working on it, can detect "the heat given off by a bumblebee at the distance of the moon". That's pretty darn cool (in more ways than one). Now, working that out, (making the completely absurd assumption that heat radiation from a bumblebee in terms of body mass can be scaled up linearly and applicable to other creatures (absurd, because of completely different chemical processes, and because surface area varies as a square of the cube root of mass, and that probably has more to do with it), and that the detectability of the heat source follows an inverse square law (probably true)) that means that Hank [our 165-lb dog --g] should be observable at the distance of a far asteroid, and a blue whale outside the heliopause. (warning -- false precision ahead) Now, when we get to the first star (Proxima Centauri), we need about 9.4 billion human beings to be seen (i.e about a third more than exist on Earth). And if we take the entire biomass of the planet Earth, that should be detectable at about a distance of 231 light years, about the distance of Alpha Cassiopeiae. Of course, anything that sensitive is perforce swamped by any heat source anywhere near there target, so unless there's an absolutely cold planet out there with no star to orbit about, I don't think we will be able to detect life directly by its heat....,