Check out this sweet, new, glorious map of the Earth!:
Yes, that is correct, you are seeing GRAVITY! When I go to explain my PhD to people, it usually results in them just saying 'So you're trying to find gravity, right?' Well, sort of. But in a wavy, gravy sort of form. This GOCE satellite from the European Space Agency has mapped out the gravitational field of the Earth. This is a little tricky of a map to figure out, especially as there are positive values on the scale. This does NOT mean that when you go to Papua New Guinea, this happens (copyright Bill Watterson):
Instead, the way they describe it on the satellite homepage is that GOCE acts like a spirit level, you know, those ones you have in your house that you played with as a kid to watch bubbles float around? You didn't do that? Oh, okay. Anyway, I am sure you have seen or used these before. The last time I used one properly was trying to install a dishwasher at my ex-boyfriend's house. Try installing a dishwasher without one. Just try it. And then... put it on SUPERWASH and see how many dishes you can break. I bet it makes one hell of a racket. Probably more impressive than my washing machine on hi-spin. Sounds like a rocket engine taking off.
Anecdotes aside, you know what I am talking about. This thing:
This satellite is basically a giant one of these. They have sensitive balls (tee hee) along the satellite that respond to gravitational pull, marking high points and low points. The satellite apparently was supersensitive to any moving parts, so the whole thing is a measuring device. The balls in the machine had to be in effective free-fall to get the readings as well, which is obtained by orbiting Earth (think about it... throw a ball really fast, straight away from you, now since the Earth curves, the ball falls to the ground like normal, but then the ground has fallen away so the ball just keeps falling as it keeps moving horizontally at that speed...crazy, I know) So...yeah, that is how this works.
I am not quite sure of the scientific uses for this. They say that it will be useful information for lots of geological sciences, which I can sort of see, precision is always nice. Plus, this epic map was only two months worth of data, so it is pretty impressive in it's efficiency. They also use the age-old academic reasoning that lots of people in the *ahem* gravitational world use and that is "but it's the TECHNOLOGY! Look at all the cool, supersensitive technology we have developed!" This is valid and widely used reasoning for high-precision science that may not have super-exciting applications just yet. Seriously, you never know when you will need the technology or when the data will be applicable. Pretty picture though, right? Yay, gravity.
Edit: As was pointed out by my esteemed friend, DAstronomer, where the bloody hell are the units on that thing? I assumed the 'level' plot was just a scaled factor, made-up unit thingy. Okay, but seriously, latitude and longitude people! Maybe geophysicists have their own secret unit language.