Does gravity change with the seasons?
Posted by Xeno on April 18, 2009
EVERYONE has heard of Newton’s apple. He watched it drop to the ground in the autumn of 1666, prompting him to ask a series of questions. “Why should that apple always descend perpendicularly to the ground?” Newton wondered. “Why should it not go sideways or upwards, but constantly to the Earth’s centre?”
One question Newton didn’t ask is whether apples or oranges fall differently. Or whether an apple would fall differently in the spring. They might seem peculiar concerns, but Alan Kostelecký, a physicist based at Indiana University in Bloomington, thinks they are important. He and his graduate student Jay Tasson have found that such flagrant violations of our best theory of gravity could easily have evaded detection for centuries.
What’s more, in a paper published in Physical Review Letters (vol 102, p 10402), the pair have shown that investigating such unlikely-seeming possibilities could help us work out what makes the universe tick. “We have made a surprising and delightful discovery,” Kostelecký says. “We might just catch a glimpse of the ultimate theory that underpins our universe.”
At the moment, relativity and the standard model are incomplete. General relativity breaks down when gravity is very strong – when describing the big bang, for example, or the heart of a black hole. And the standard model has to be stretched to breaking point to account for the masses of the universe’s fundamental particles. The two theories are also incompatible, having entirely different notions of time, for instance. This has made it impossible to unite the two in a single “theory of everything”.
The trouble is, despite their faults, relativity and the standard model are very good theories. Taken separately, they describe perfectly almost all physical phenomena known to science. If we want to know what the theory that unites them is going to look like, we have to find things that they cannot explain.
“The challenge is to find those phenomena,” says Kostelecký. This is what he and Tasson think they might now be able to do.
lecký. This is what he and Tasson think they might now be able to do.
They have begun by launching an attack on an almost sacred premise of physics, known as Lorentz symmetry. This says that the laws of physics appear the same for anyone moving at uniform speed relative to you, whatever their orientation in space.
One consequence of Lorentz symmetry is that the universe should be isotropic: whichever way you look or travel, everything seems pretty much the same and behaves in the same way. There is no “up” or “down”, and there is no direction in which light, people or planets can travel more easily.
So, if they can find effects of the as yet undiscovered X-field, these researchers may finally have a single theory which explains everything. And then they could use that discovery to reverse grey hair and all other signs of aging with a single swish of a pleasing berry flavored mouth rinse?