Jewish World Review Jan. 24, 2003 / 21 Shevat 5763
An issue of great gravity moves forward
http://www.NewsAndOpinion.com | My guess is that the phrase "the speed of gravity," makes as much sense to most of as, say, "the color of music" or "the weight of timidity."
Which is to say that hardly any of us (except a few showoffs) knew gravity had - or even could have - a speed at all. That just shows how little attention we've paid to Albert Einstein for the last 100 years.
Einstein, by the way, is dead. I'm sorry if that's news to you, but you're better off facing the reality of his demise. And yet however dead Einstein is, his theories live on. And on.
Why, the more scientists discover, the smarter Einstein seems to have been - especially considering that he did all his calculations without a laptop, a cell phone or an electric blanket. (I threw in the blanket to get you used to thinking about oddities like gravity having speed.)
It pleases me that one of the scientists who figured out the speed of gravity is from my alma mater, the University of Missouri, the school that doesn't pay its football players enough. Sergei Kopeikin, an associate professor of physics there, did this work with Ed Fomalont of the National Radio Astronomy Observatory in Charlottesville, Va.
Their findings were described in the Jan. 9 issue of New Scientist magazine, which you can usually find on shelves next to Old Scientist and Really Old Scientist.
"Probably nobody expected that the speed of gravity can be measured so soon," Kopeikin wrote in an e-mail to me after I asked him about his work. Kopeikin gives too much credit to the average American, who probably never expected the speed of gravity could be measured at all, much less so soon.
Physics historically has been defined by two scientists with big brains. One was Isaac Newton, whose brother Huey once ran the Black Panthers, unless I'm thinking anachronistically outside the box.
Newton (Isaac, not Huey) thought the influence of gravity was instantaneous. Which is to say that the sun's pull on Earth is immediate. But Einstein thought gravity was like light in that it traveled at the speed of light. In fact, Einstein integrated this assumption into his 1915 general theory of relativity.
If Newton were right, the Earth would shoot out of orbit immediately upon the sudden disappearance (G-d forbid) of the sun. If Einstein were right, Earth would remain in orbit for eight-plus minutes after the sun went bye-bye because that's how long it would take gravity's pull to quit coming to Earth from the sun.
But for nearly a century, no one had measured the speed of gravity to know whether Newton or Einstein was right.
For one thing, no one has been able to detect gravitational waves, which New Scientist describes as "little ripples in space-time that propagate out from accelerating masses." Think of the woosh special teams kickoff returners on football teams feel when just missed by 345-pound defensive hulks. I don't know if that's a good analogy, but think about it anyway. It's scary.
That, however, is not the method Kopeikin and Fomalont used. They, uh, used something else. Look, I've read over the method they used but can't explain it. It has something to do with Jupiter passing in front of a quasar that sends out radio waves and then measuring the apparent change in the quasar's position as it was affected by Jupiter's gravity.
I once took a physics class from the very department where Kopeikin now works. But it has helped me zero in explaining this stuff. The important point is not whether I can explain it, however. The point, instead, is that their measurements showed that gravity moves at the speed of light.
Well, actually, they determined it moved at 95 percent the speed of light, plus or minus 25 percent. Which apparently is close enough for gravity work.
What difference does this make for average humans? The way I
figure it, if Kopeikin and Fomalont can have a 25 percent fudge
factor in the speed of gravity, the rest of us are allowed a similar
fudge factor in gravity's effect on us, namely our weight.
Theoretically, that means I just lost 47 pounds. Excellent.
Enjoy this writer's work? Why not sign-up for the daily JWR update. It's free. Just click here.