Physicists have achieved a groundbreaking feat by capturing a rare optical illusion of an object seemingly moving at an astonishing 99.9% of the speed of light. This remarkable feat was accomplished using cutting-edge technology, including ultra-fast laser pulses and specialized cameras, which have allowed scientists to simulate a phenomenon known as the Terrell-Penrose effect. This effect, a consequence of special relativity, predicts that fast-moving objects should appear shortened in the direction of motion, a phenomenon known as Lorentz contraction. While this effect has been indirectly confirmed in particle accelerator experiments, this is the first time it has been successfully demonstrated in a controlled lab setting.
Dominik Hornof, a quantum physicist at the Vienna University of Technology and the lead author of the study, expressed his enthusiasm for the simplicity of the approach. He stated, 'With the right idea, you can recreate relativistic effects in a small lab. It shows that even century-old predictions can be brought to life in a really intuitive way.'
The study involved creating snapshots of a cube and a sphere 'moving' at nearly the speed of light using ultra-fast laser pulses and gated cameras. The results showcased rotated objects, providing strong evidence for the Terrell-Penrose effect. However, the researchers faced significant challenges due to the practical limitations of moving objects at such high speeds. Hornof explained, 'In Einstein's theory, the faster something moves, the more its effective mass increases. As you get closer to the speed of light, the energy required grows exponentially. We cannot generate the necessary energy to accelerate a cube, which is why we need massive particle accelerators, even for moving electrons at high speeds.'
To overcome these challenges, the team employed a clever technique. Hornof elaborated, 'We mimicked the visual effect by using a cube with a side length of approximately 3 feet (1 meter). We fired ultra-short laser pulses, each lasting only 300 picoseconds, at the object. A gated camera captured the reflected light for each pulse, producing thin slices of the object's motion. After each slice, the cube was moved forward by a distance equivalent to what it would have traveled at 80% the speed of light during the pulse delay.'
By combining these slices, the researchers created a snapshot of the cube in motion, making it appear to race incredibly fast, even though it never physically moved. The same technique was applied to a sphere, which was shifted by 2.4 inches (6 cm) per step to mimic 99.9% of the speed of light. When the slices were assembled, the cube appeared rotated, and the sphere seemed to have sides that could be peeked around, creating an optical illusion.
Hornof clarified that the rotation is not physical but an optical illusion caused by the geometry of light arrival times. This illusion does not contradict Einstein's special relativity. While fast-moving objects are physically shortened along their direction of travel, cameras do not directly capture this effect. The snapshot shifts due to the timing of light arrival from the front and back, creating the illusion of rotation.
The researchers were delighted with the results, as the geometry aligned beautifully with their calculations. Hornof expressed his excitement, saying, 'When we did the calculations, we were surprised how beautifully the geometry worked out. Seeing it appear in the images was really exciting.'
This groundbreaking study, published in the journal Communications Physics, has opened new avenues for exploring relativistic effects in a controlled environment. Larissa G. Capella, a science writer based in Washington state, who holds a B.S. in physics and a B.A. in English creative writing, has covered various scientific topics, including environmental, Earth, and physical sciences, as well as other areas that spark her curiosity.
