
BACKWARD RESEARCH GOES FORWARD
by Alan Boyle
Posted: Tuesday, July 17, 2007
University of Washington physicist (and science-fiction author) John Cramer is moving forward with his experiment in backward causality,
thanks in part to tens of thousands of dollars in contributions sent in
by his fans. Although Cramer emphasizes that his lab is looking at
“nonlocal quantum communication” rather than backward time travel per
se, the gadgetry he’s assembling could settle a controversy surrounding
a seemingly faster-than-light effect that Albert Einstein thought was downright spooky.
Boiled down to its basics, the experiment
involves splitting laser light into two beams, so that characteristics
of one beam are reflected in the other beam as well. That's an example
of what physicists call quantum entanglement. Specifically,
Cramer has been planning to fiddle with one of the entangled
laser beams such that it takes on the property of waves or particles.
If one beam behaves like particles, the entangled photons of light in
the other beam should behave like particles, too.
So what happens when the beams go their
separate ways, and you conduct a wave-vs.-particle measurement on one
beam? When someone else checks the other beam, the same measurement
should yield the same result. In fact, you could visualize using the
wave-vs.-particle toggle as a means for communicating information, sort
of like Morse code. Theoretically, you could check one beam to
receive a message instantaneously from whoever is fiddling with the
other beam – even if you're separated from the receiver by millions
of light-years.
That's what Einstein considered “spooky action
at a distance.” Such an effect could send information faster than light
beams could travel, running counter to special relativity – and thus
Einstein thought the effect was impossible to achieve. However, the evidence is mounting that quantum entanglement actually happens.
Cramer planned to start out by testing this
kind of communication through quantum entanglement – that's the
“nonlocal communication” part of the experiment. If that worked, Cramer
would go even further: He would send one of the entangled beams (call
it Signal A) through a circuitous detour – say, a few miles of
fiber-optic cable – then fiddle with it when it came out of the cable.
If the principles behind nonlocal communication held true, the evidence
of that fiddling should be detected at a corresponding place in the
other entangled beam (call it Signal B).
Now brace yourself for the backward-causality
part: Because Signal B followed a shorter route to its detector, the
fiddling in Signal A could theoretically show up in Signal B before Cramer actually fiddles with Signal A. It would be as if Cramer's actions had an effect that worked backward in time.
If Cramer detected that effect, the findings would raise the kinds of paradoxes you might see in science-fiction novels or “The Twilight Zone.” What if you detected a signal from the future, but then decided not to send the signal? (That's called the “bilking paradox”).
What if you received the text of a best-selling manuscript from
yourself in the future, had it published, then saved a copy so you
could send it to yourself in the past? (Cramer calls that the
“immaculate conception paradox.”)
“Perhaps the fact that there are such paradoxes
is nature's way of telling us that our experiment isn't going to work,”
Cramer said.
Nevertheless, Cramer is anxious to find out whether it might work – and if not, why not. He suggested the framework for the experiment a year ago, and no one could come up with a reason why it should fail. Except for the money problem. …
For months, Cramer struggled to find the funding he needed to buy the equipment for the experiment, to no avail. Then an article about his plight came out in the Seattle Post-Intelligencer – and within weeks, thousands of dollars flowed in
from foundations and private donors who, for one reason or another,
wanted to find out what kind of answers Cramer could come up with.
Cramer said the fund now amounts to $40,000, and now that he's back from a tour of duty at the Relativistic Heavy Ion Collider,
he's moving forward with the laser experiment. “If that laser holds
out, then I think we're in pretty good shape,” he told me today.
He's hoping to complete the experiment by
September, when the equipment he's using will have to be
moved someplace else to make room for remodeling. “It would be very
nice if we could finish up by the 15th of September, but I don't know
if we'll be able to do that or not,” he said.
Cramer is grateful for all the donations, but
he admitted that he's “a little uncomfortable” about the way things
have gone so far. Usually, physicists work in obscurity, get some
funding, conduct an experiment, publish the results – and only then
does the publicity come, if the results are spectacular enough. The way
Cramer sees it, there's been a heck of a lot of publicity already about
an experiment that has yet to be done.
“We seem to be doing it sort of backwards, in a
sense,” he said. Then, realizing that he's been talking about backward
causality, he added with a chuckle that “it may be relevant to the
experiment we're trying to do.”
Cramer, who is the author of two science-fiction novels and a regular columnist
for Analog magazine, said the experiment represents “a rare opportunity
to push the envelope of quantum mechanics.” No matter how it turns out,
the results will be put to good use, he said.
“If this experiment we're doing works, then I
will follow up and push it as hard as possible. And if it doesn't work,
I will write a science-fiction novel where it does work,” he said. “It's a win-win situation.”
Feel free to add your thoughts about backward causality and time travel in the comments section below, or visit our discussion board. And if you've already come up with a solution for backward time travel, fill me in on the secret … yesterday.









