Physicists in Vienna Excitedly Recreate the Terrell-Penrose Effect from Einstein’s Relativity Using Lasers and Cameras
Scientists in Vienna have successfully recreated the Terrell-Penrose effect, an optical illusion based on Einstein’s relativity, using high-speed cameras and laser pulses to slow light to barely 2 meters per second. Physicists James Terrell and Roger Penrose established this conclusion, which shows that super-fast objects seem rotated, in 1959. The researchers utilized a cube and a sphere to imitate slow light speeds, with laser pulses and a high-speed camera recording laser flashes reflected from various spots on the objects at different times. The researchers discovered that while this effect is not obvious in ordinary life, it is plainly visible in a rocket traveling at close to the speed of light.
Physicists in Vienna Excitedly Recreate the Terrell-Penrose Effect from Einstein’s Relativity Using Lasers and Cameras
Through the integration of lasers and cameras to simulate slow light speeds, physicists in Vienna have recreated the Terrell-Penrose effect, a strange visual illusion from Einstein’s relativity. As predicted more than 60 years ago, a fast-moving cube appears twisted.
Introduction to the Terrell-Penrose Effect: Strange Things Happen in Relativity at Light Speed
Our common notions of space and time begin to distort when things move extremely quickly, almost at the speed of light. Einstein’s unique theory of relativity is centered on this. In reality, objects get shorter as they accelerate, and time moves differently for them than it does for an observer. Even though it sounds crazy, innumerable experiments have verified it.
However, there is one bizarre relativity prediction that has never been observed before. The Terrell-Penrose effect states that extremely fast objects should appear rotated rather than just shorter. The physicists Roger Penrose and James Terrell independently arrived at this result back in 1959. And now, for the first time, scientists in Vienna have used high-speed cameras and laser pulses to visually duplicate this bizarre effect by cleverly slowing down light to just 2 meters per second.
As you accelerate, you seem shorter
Consider a rocket that flies by us at 90% the speed of light. According to Prof. Peter Schattschneider of TU Wien, “it is 2.3 times shorter for us now than it was before it took off.” This is the Lorentz contraction, which is another name for the relativistic length contraction.
This contraction, however, is not photographable. Peter Schattschneider says, “You would have to consider that the light from different spots required different amounts of time to reach the camera if you wanted to take a photo of the rocket as it traveled past.” Complex optical effects are produced when light from various regions of the object does not emit simultaneously and arrives at the lens or our eye at the same moment.
The Terrell-Penrose Effect Explained: Rotated Cube
Consider a cube as the extremely fast object. Then, the side that is not facing us is farther away than the side that is. When a photon from the cube’s back corner and one from its front corner arrive at our eye simultaneously, the photon from the back corner has gone farther. Thus, it had possibly emerged earlier. Additionally, when the light was emitted from the front corner, the cube was not in the same place.
Peter Schattschneider explains, “This gives us the impression that the cube has been turned.” This combines the varied travel times of light from various sites with relativistic length contraction. As Terrell and Penrose predicted, this results in an apparent rotation.
Even when taking pictures of a really fast car, this is obviously meaningless in daily life. When comparing the light emitted by the side of the automobile facing away from us to the side facing us, even the quickest Formula One car will only travel a very small portion of the distance in the time difference. A rocket approaching the speed of light, however, would make this effect quite apparent.
Relativity Recreated in a Lab
As of right now, rockets cannot be accelerated to a point where a camera could capture this effect. But the team from USTEM at TU Wien, lead by Peter Schattschneider, came up with another artistically creative solution: they replicated the effect in the lab using incredibly brief laser pulses and a high-speed camera.
Victoria Helm and Dominik Hornof, the two students who conducted the experiment, noted, “We moved a cube and a sphere around the lab and used the high-speed camera to record the laser flashes reflected from different spots on these objects at different times.” “You can construct a condition that yields the same outcomes as if the speed of light were no more than two meters per second if you get the timing perfect.”
Moments in Time Show the Impossible
Combining photos of several landscape elements into a single, sizable image is simple. However, this is the first time that the time factor has been included, as the object was captured at multiple points in time. After then, a single still image is created by combining the regions that the laser flash lighted at the precise moment when light would have been released from that location if light had only traveled at a speed of 2 m/s.
The Terrell-Penrose effect becomes apparent as a result. We created little video snippets of the incredibly swift objects by combining the still photos. Peter Schattschneider explains, “The outcome was just what we expected.” “A sphere stays a sphere, a cube looks twisted, but the North Pole is somewhere else.”
When Art and Physics Work Together
In addition to being a scientific triumph, the Terrell-Penrose effect presentation is the product of a remarkable collaboration between art and science. Enar de Dios Rodriguez’s art-science project served as the foundation. A number of years ago, he investigated the potential of ultra-fast photography and the ensuing “slowness of light” in partnership with the University of Vienna and the Vienna University of Technology.
The findings, which have now been published in the journal Communications Physics, could provide us with a deeper understanding of the intuitively enigmatic realm of relativity.
Reference: “A snapshot of relativistic motion: visualizing the Terrell-Penrose effect” by Dominik Hornof, Victoria Helm, Enar de Dios Rodriguez, Thomas Juffmann, Philipp Haslinger and Peter Schattschneider, 31 April 2025, Communications Physics.