Scientists used ultrafast laser pulses and a special camera to simulate an optical illusion that appears to contradict Einstein’s special theory of relativity.
One of the consequences of special relativity is that fast-moving objects appear shorter in the direction of their movement. This is a phenomenon known as Lorentz contraction. This effect has been indirectly confirmed in particle accelerator experiments.
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Although previous models have been able to exploit this illusion (now called the Terrell-Penrose effect), this is the first time it has been performed in a laboratory setting. The research team published their results in the journal Communications Physics.
“What I like most is its simplicity,” Dominik Hornoff, a quantum physicist at the Vienna University of Technology and lead author of the study, told Live Science. “With the right idea, we can reproduce relativistic effects in a small laboratory. This shows that even predictions made centuries ago can be realized in a very intuitive way.”
reproduction of fantasy
In the new study, physicists used ultrafast laser pulses and a gated camera to create snapshots of cubes and spheres “moving” at nearly the speed of light. The results showed a snapshot of the rotated object. This proved that the Terrell-Penrose effect is true.
However, like all research, this study had its challenges. It is currently impossible to move objects at or near the speed of light. “In Einstein’s theory, the faster something moves, the more its effective mass increases. As you approach the speed of light, the energy required increases significantly,” Hornoff said. You can’t generate enough energy to accelerate something like a cube, “so you’d need a huge particle accelerator just to get an electron close to that speed. That would require a huge amount of energy.”
So the team wisely appointed a substitute. “What we can do is mimic the visual effects,” Hornoff said. They started with a cube about 3 feet (1 meter) on each side. They then fired ultrashort laser pulses (each just 300 picoseconds long, or about a billionth of a second) at the object. They captured the reflected light with a gated camera that opened only at that moment, producing a thin “slice” each time.
After each slice, they moved the cube forward about 1.9 inches (4.8 cm). This is the distance you would travel if you traveled at 80% of the speed of light during the delay between pulses. The scientists then combined all these slices to create a snapshot of the cube in motion.
“When you put all the slices together, it looks like the object is moving incredibly fast, even though it’s not moving at all,” Hornoff said. “At the end of the day, it’s just geometry.”
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They repeated this process with a sphere, moving it 2.4 inches (6 cm) with each step, mimicking 99.9% of the speed of light. When you combine the slices, the cube appears to rotate and a sphere appears to be peeking out from the side.
“Rotation is not physical,” Hornoff said. “It’s an optical illusion. Geometric patterns where light hits us all at the same time trick our eyes.”
This is why the Terrell-Penrose effect is consistent with Einstein’s special theory of relativity. Objects moving at high speed physically become shorter in the direction of travel, but the camera does not directly capture this. Light from the back takes longer to reach than light from the front, so the snapshot appears as if the object is rotating.
“When we did the calculations, we were surprised at how beautiful the shape turned out to be,” Hornoff says. “It was really exciting to see it come out on film.”
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