Thursday, October 12, 2006

The Force Is Strong, And It's Messing Up Our Calculations

Some people are way too smart. It's almost scary the things that these especially astute people can think through with their mighty Super Brains. How many of us really understand what Einstein's Theory of Relativity is, and why we should even care, let alone grasp the math required to prove it? Up front I'll say I certainly don't, and if you do, you had probably better go read somewhere else, because this post is waaaaay beneath your abilities. I like to skim the surface of science for fun. I am enough of a geek to get a kick out of scientific theory and technological development, and I even did the extra credit geometry problems for fun in school. (My teacher didn't give the extra credit, so I guess that tilts me a little farther into the geek category.) However, I went on to be a Lit major, not a Smart Person, so I just get floored with the things that some people are able to figure out.

I have been at the European Space Agency website this morning, and not only do these people understand Einstein's theory, they are heading out into space to test it and "lay the foundation" for further developing its concepts, also potentially enlarging their knowledge of gravitation and navigation in the process. By navigation I am, of course, referring to space navigation. I don't think the European Space Agency is worried about directing ocean liners and weather balloons. They're interested in directing space ships, and calculating the huge distances between heavenly bodies, and figuring out how much gravitational pull those planets, and stars, and black holes, etc., are going to have that could pull probes and ships off their intended course. The weather balloons will have to fend for themselves.

Since we're talking space and astronomical bodies, there is a basic question about how you account for the movement of these bodies when calculating distances and locations--of anything. If two items are both moving, there has to be a way to measure that motion. Apparently, this involves bringing another object into the mix:

A cornerstone of relativity is the concept of a frame of reference. This is a set of bodies relative to which any motion can be measured. Without a reference frame, no motion through space can be detected. Scientists call a frame of reference 'inertial' if unperturbed objects appear in that frame, either at rest or moving at a constant velocity. For a reference frame to be perfectly inertial, the bodies that are used to mark it must be completely free of any force.
If I'm reading this right, scientists can measure things accurately in space only if they have objects to which they can compare other item's motion--objects that are either completely still, or are moving at a completely constant rate, but without being affected by the pull or push of anything else. They then can measure the motion and distance of other bodies relative to these celestial touchstones. The problem the ESA is facing is that gravity from all those big celestial bodies out in the great beyond is always mucking up the works, and its very difficult for any frame of reference to be "free from any force," so the measurements get all out of whack.

So, what is the ESA doing to overcome these difficulties? They are working to create their own frames of reference, and compensate mathematically for the "warping" of the measurements of distance that happens when gravity is not properly taken into account:

To make this measurement, LISA Pathfinder uses two 'proof-masses'. Each is a small cube of a gold and platinum alloy, whose relative motion is measured by a laser beam. Once in space, the proof-masses will float freely within the spacecraft. When subtle forces act on the proof-masses, the laser beam will detect the way they change position to within a few thousandths of a billionth of a meter, and will be able to detect forces as small as the weight of a typical bacterium.
In layman's terms, or as close as I can come even to that low standard, they made these gold and platinum alloy cubes (only 5 centimeters wide) because they are as close to being impervious to magnetic fields as they could possibly get them, since that is another force which can act on objects out in space. They have made them this way so that the only force they will respond to is gravity, and they hope to send them out into space, free-floating in this vessel called LISA Pathfinder. Then the fancy extra-accurate laser measuring gismo will track their every motion. In this way, they hope to detect and calculate the gravitational forces that throw off the accuracy of space measurements, and then they'll do lots and lots of complicated math to work out how much distance is really between all those celestial bodies that are currently way beyond our reach, but we might get to once the Smart People figure out warp drives.

The date they're shooting for to send LISA Pathfinder into space is sometime in 2009. This mission is the forerunner to LISA, which is a bit more large-scale, in which, "three spacecraft...will work together to detect Einstein's predicted ripples, known as gravitational waves, in the fabric of spacetime." Okay, I'm barely getting my head around the concept that these people can do the math involved in compensating for gravity when calculating distances in space, now they want to start looking for ripples in the fabric of spacetime. I think I'll ignore this part. I can only handle one over-my-head topic at a time, thank you very much. All the same, the Super Brains are really amazing, don't you think? I wonder what they'll work on once they have all this space measuring and navigation stuff figured out? Probably those warp drives we're going to need once they have the navigation part down. Whatever it is, I'm sure most of us won't understand it. I think I'll go read some literature now.