GCN LAB IMPRESSIONS
NASA satellites prove Einstein right, again
Gravity probe confirms theories about gravitational effects on space-time
- By Greg Crowe
- May 06, 2011
NASA recently announced that it had managed, through the collection of finely tuned satellite data, to confirm some of Albert Einstein’s predictions about relativity. In 2004, NASA started the Gravity Probe B mission by launching four satellites with super-precise gyroscopes. Those devices could actually measure the effect the Earth has on surrounding space-time.
Before someone hits me with a sonic screwdriver, let me explain. Feel free to imagine Carl Sagan’s voice explaining this. Einstein theorized that all gravitational bodies had certain effects on space and time. Imagine some kind of taut elastic cloth stretched out in a horizontal plane. Now put a ball out there in the middle. See how the cloth distorts where the ball is resting? Well, that is something like the way gravitational bodies affect space-time.
Except the space-time disruption tends to make a cone that is a bit pointier than what our ball did. Also, the Earth’s rotation makes the local space-time sort of swirl, as if it were spinning around in some viscous mass that the Earth just half-drags along. The cone thingy is called the geodetic effect, while the syrup business is called frame dragging.
Still with me? Good.
Sure, at least the former effect could be observed by looking at stars behind the sun during a solar eclipse, as was done as far back as Einstein’s time, though cloud cover sometimes halted such efforts.
Only recently were scientists able to develop devices precise enough to actually measure both of those two effects made by our planet, which Einstein predicted would be pretty darn small. And he was right again.
If gravity did not affect space-time, then a satellite in a stable orbit would always be looking in the same direction forever. However, NASA measured that those four satellites actually moved an average of — now get this — 0.0018 degrees per year due to geodetic precession and all of 0.000011 degrees per year due to frame dragging.
Wow, no wonder it took almost 90 years for technology to get good enough to measure values that teeny.
Now, although these discoveries haven’t had any real-world applications, the research and development that made this project possible have led the way in several Global Positioning System applications and certain satellite design ones.
So I guess that just goes to show that “pure science” projects still have real, practical value beyond the betterment of mankind — one that doesn’t always appeal to governments and corporations.
And who knows, can some really cool stuff like time travel be that far behind?
Greg Crowe is a former GCN staff writer who covered mobile technology.