Reflecting light off satellite backs up Wheeler's quantum theory thought experiment
A team of researchers with Università degli Studi di Padova and the Matera Laser Ranging Observatory in Italy has conducted experiments that add credence to John Wheeler's quantum theory thought experiment. In their paper published on the open access site Science Advances, the group describes their experiment and what they believe it showed.
The nature of light has proven to be one of the more difficult problems facing physicists. Nearly a century ago, experiments showed that light behaved like both a particle and a wave, but subsequent experiments seemed to show that light behaved differently depending on how it was tested, and weirdly, seemed to know how the researchers were testing it, changing its behavior as a result.
Back in the late
1970s, physicist Johan Wheeler tossed around a thought experiment in
which he asked what would happen if tests allowed researchers to change
parameters after a photon was fired, but before it had reached a sensor
for testing—would it somehow alter its behavior mid-course? He also
considered the possibilities as light from a distant quasar made its way
through space, being lensed by gravity. Was it possible that the light
could somehow choose to behave as a wave or a particle depending on what
scientists here on Earth did in trying to measure it? In this new
effort, the team in Italy set out to demonstrate the ideas that Wheeler
had proposed—but instead of measuring light from a quasar, they measured
light bounced from a satellite back to Earth.
The experiment consisted of shooting a laser beam at a beam
splitter, which aimed the beam at a satellite traveling in low Earth
orbit, which reflected it back to Earth. But as the light traveled back
to Earth, the researchers had time to make a choice whether or not to
activate a second beam splitter
as the light was en route. Thus, they could test whether the light was
able to sense what they were doing and respond accordingly. The team
reports that the light behaved just as Wheeler had
predicted—demonstrating either particle-like or wave-like behavior,
depending on the behavior of those studying it.