Monday, July 14, 2008

6 Billion Year Old Particles Maintain Weight

In the case of subatomic particles, the phrase "still the same after all these years" should be taken literally. As German astrophysicists recently discovered, the mass ratio of the proton and the electron is the same as it was 6 billion years ago.

Specifically, protons weighed 1,836 times more than electrons back then, and they still do!The researchers who performed the study had originally detected ammonia in a very far off galaxy, by observing its absorption of radio waves from a powerful bundle of energy called a quasar, located behind the galaxy.

Because light from such a distant object takes time to travel to us here on earth, the farther away scientists probe the universe, the farther back into the past they see. Therefore, they actually viewed ammonia as it was millions and millions of years ago.

Because of its pyramid-like structure, ammonia behaves differently than other molecules when absorbing the energy from radio waves. In a feat of subatomic gymnastics, an ammonia molecule actually flips inside out, its three hydrogens moving from the bottom of the pyramid to the top, while its nitrogen resumes the base position.

As researchers knew, the key to the flip lies in the ratio between the mass of the proton and the electron. They compared the ammonia absorption data to other molecules within the same galaxy and found that absorption was basically the same, indicating that the proton/electron mass ratio had not changed.

We all know subatomic particles are really, really tiny, so who cares what they weigh? Turns out that question is a loaded one. Many scientists believe that changes in particle masses provide evidence that universal constants like the speed of light, are well, not so constant after all. This idea might provide explanations for dark energy, and hidden extra dimensions proposed by string theory.

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