Einstein's relativity theory hits a speed bump

Phantasm66 · Aug 8, 2002

Einstein's relativity theory hits a speed bump
August 8 2002

Australian scientists have discovered that light isn't quite as fast as it used to be. But it doesn't mean E=mc2 will be consigned to the dustbin, writes David Wroe.

In October, 1971, American physicists took four super-accurate atomic clocks, kept two on the ground and put two on commercial jets flying at 1000 kmh in opposite directions around Earth.

When the planes landed, the scientists found what they were hoping for: The clocks on the high-speed journeys were ticking a few billionths of a second behind their stationary friends.

Motion, it turns out, slows time - one of the funny effects of the law of relativity. At low speeds, the effect is slight and makes no difference to our daily lives.

We had no idea to look for such effects until the 26-year-old Albert Einstein walked into the office of Annalen der Physik journal in Bern, Switzerland, in 1905, gave the editor his paper on the special theory of relativity and asked that it be printed "if you can find room for it".

That paper, and the general theory of relativity that followed it, revolutionised the way scientists understood the universe, and history has remembered it ever since as a shift from Newtonian physics - where space, time, motion and gravity are separate and proceed with rigid, clockwork elegance - to Einsteinian physics, where things bend, stretch and pull on each another in most unusual ways.

In between these paradigm shifts, there are leaps in understanding. Today's announcement by Australian physicists in the leading scientific journal Nature may turn out to be one of those moments.

Incorporating some of the most intriguing aspects of cosmology and theoretical physics - distant quasars, black holes, event horizons and, probably, quantum theory - they have concluded that the speed of light has slowed down over time.

The discovery means faster-than-light travel, which is prohibited by the law of relativity, may one day be possible. It also changes our understanding of the beginnings of the universe. But lead author and award-winning physicist and writer Professor Paul Davies emphasises that Einstein's famous equation, E=mc2, is not about to be consigned to the dustbin.

Energy, Einstein discovered, was equal to mass times the speed of light squared, with the speed of light as a constant in a vacuum such as space. News that the speed of light may not be constant after all does not mean the old theory falls apart altogether, Davies says. The theory of relativity remains good for most situations, just as Newton's laws remained more or less correct after Einstein, except at high speeds or under intense gravity.

"It's not going change the way we build cyclotrons or microchips or anything of that sort," Davies says. "It's just that the theory of relativity will be seen not to be the last word."

If the speed of light was close to infinity, immediately after the Big Bang, as Davies believes it may have been, our theories about the way energy cooled to form matter, giving rise to stars, planets and people, could be completely wrong.

Still, correcting Einstein is no small feat and is likely to attract controversy, perhaps even animosity from scientific colleagues.

"When I first heard about these observations . . . I was, frankly, not only sceptical about it, I was appalled," Davies says. "I thought it was horrible. The last thing we wanted in theoretical physics was to have something like this."

Einstein, who died in 1955, is still regarded as perhaps the greatest mind ever. The remarkable thing about his discoveries was that he literally sat in his flat in Bern during his spare time while working as a clerk at the patent office and thought it all up using sheer brain power. Only later were his theories proved, repeatedly, through experiment and observation.

Dr Charley Lineweaver, one of Davies' co-authors, along with graduate student Tamara Davis, explains that their paper works the other way around. They have taken observations and plugged the data into known mathematical formulas to determine that the speed of light has slowed.

"Theorists always play with all kinds of crazy things," Lineweaver says. "The important thing here is we have experimental evidence . . . that's what's new here."

The theory is based on observations made at the University of New South Wales by Dr John Webb in 1999 and further observations by one of his PhD students, Michael Murphy.

It is hair-curling science. They looked at light from the most distant objects in the universe, quasars up to a billion times the size of our sun, which are 10 billion or 12 billion light years away.

"The light that comes to you from a quasar has been travelling for most of the age of the universe - several billion years - and it carries with it information about what happened to it along the way," Murphy says.

On its long journey, the light from those quasars has passed through gas clouds full of metals. The photons in the light - little packets of energy that make up the light itself - interact with the electrons in the gas clouds, charged particles that orbit the nuclei of the metal atoms. This leaves a fingerprint on the light as it arrives on Earth, called the fine structure constant, Murphy explains.

When they measured the fine structure constant of this 12 billion-year-old light, Webb and Murphy found it was slightly higher than it would be today. Mathematically, there were two possible reasons for this - either the electric charge of the electrons had increased, or the speed of light had fallen.

Using Stephen Hawking's formula for black hole thermodynamics, Davies, Davis and Lineweaver ruled out the electric charge possibility. By adapting Hawking's formula, they determined that an increase in electric charge would break the second law of thermodynamics, which says energy can only flow from hot spots to cold spots.

"That's illegal. It would be like a cup of coffee sitting on your desk getting hotter," Lineweaver says.

But while he is still cautious about the quasar observations, he says the implications are revolutionary if they hold true. "Supposing we do take it seriously, then we have some very profound things to worry about. One is, why is it doing this?"

The next question is what physical processes are at work to slow light speed? Lineweaver says that's "the subject for a thousand other papers."

One possibility, though, is that the structure of the vacuum in space has changed. This is where we get into the rather spooky world of quantum physics. When light travels through a medium other than a vacuum, such as glass or water, it slows down. A vacuum, far from being empty, is teeming with quantum "virtual" particles that flit in and out of existence.

Sometimes those particles become real, such as under a strong electric charge, Lineweaver says. If the vacuum of space is changing uniformly across the universe, just as the universe is expanding uniformly, it could affect the speed of light.

For now, Murphy and Webb's observations of quasars will continue to be scrutinised and be regarded with scepticism. "If they're right, this makes theoretical physicists very uncomfortable," Davies says. "These are cherished laws and they don't really want to have to ditch them, because all of the favoured frontier stuff these days, with people working on string theory, M-theory and all these other sexy topics, would have to down tools and start with a completely different conceptual scheme."

"On the other hand, science is made out of iconoclasm. If old theories never got overthrown, we'd all be out of work. So it's always nice to have something that challenges the basic paradigm and this does so with a vengeance."

David Wroe is The Age science reporter.

source: http://theage.com.au/articles/2002/08/07/1028157961167.html

TS | Thomas · Aug 8, 2002

As long as it's not about time travel. I hate time travel.

Phantasm66 · Aug 8, 2002

Its more about that the speed of light has changed in value during the life of the universe.

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Einstein's relativity theory hits a speed bump

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