In “Experiment shows time travel impossible” (ABC News, Monday, 25 July 2011), we learn:
Hong Kong physicists say they have proved that a single photon obeys Einstein’s theory that nothing can travel faster than the speed of light, demonstrating that time travel is impossible.
[ … ]
The possibility of time travel was raised 10 years ago when scientists discovered superluminal, or faster-than-light, propagation of optical pulses in some specific medium, the team says.
It was later found to be a visual effect, but researchers thought it might still be possible for a single photon to exceed light speed.
[Shengwang] Du, however, believes Einstein was right and determined to end the debate by measuring the ultimate speed of a single photon, which had not been done before.
“The study, which showed that single photons also obey the speed limit ‘c’, confirms Einstein’s causality; that is, an effect cannot occur before its cause,” according to the university’s press release.
In that case, some multiverse theories must be relegated to science fiction, and much science fiction becomes fantasy, no?
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