Strange Special Relativity Effect Observed For The First Time

In his classical science-fiction communicative “The New Accelerator,” published successful 1901, H. G. Wells describes a supplier that speeds up a person’s metabolism by a facet of 1,000. For nan 2 protagonists who valiantly trial nan potion, nan world appears strangely slowed down, almost stiff successful movement. The communicative sewage 1 of america (Schattschneider) thinking: If we could slow down time, could we spot azygous photons alert done space? Could we observe relativistic phenomena? In particular, could we ever glimpse a unusual prediction called nan Terrell-Penrose effect?

The Terrell-Penrose effect would make objects moving astatine astir nan velocity of ray look oddly rotated. The conception seems to spell against different prediction of Einstein’s typical mentation of relativity known arsenic Lorentz contraction, which holds that arsenic things spell faster they will shrink. Although nan Terrell-Penrose effect had been tested successful thought experiments and simulated connected computers, it had ne'er been demonstrated successful existent life.

The imaginable of real-world testing laic dormant until recently, erstwhile 1 of Schattschneider’s colleagues, quantum intelligence Philipp Haslinger of nan Vienna University of Technology, mentioned to him an research called nan SEEC project, which intends to visualize nan measurement ray moves crossed surfaces. He shared a video successful which a laser beat seems to move astatine a velocity of meters per second, only astir 1 billionth of nan velocity of light. There it was again: nan thought of slowing down time—Wells’s New Accelerator, this clip successful nan shape of not a magic potion but ultrafast photography.

On supporting subject journalism

If you're enjoying this article, see supporting our award-winning publicity by subscribing. By purchasing a subscription you are helping to guarantee nan early of impactful stories astir nan discoveries and ideas shaping our world today.

But nan scenes successful nan task were stills; nan entity didn’t move. What if we accelerated nan taxable being photographed to a velocity adjacent to that of nan laser? Would we past spot Lorentz contraction? Or would we alternatively spot nan moreover alien Terrell-Penrose effect? Almost instantly we hatched a scheme for an experiment. When 2 of america (Schattschneider and Juffmann) met up successful Juffmann’s laboratory, we recovered that we were some inspired by nan Wells story.

Schattschneider teamed pinch nan SEEC task (Haslinger, Juffmann and creator Enar de Dios Rodríguez) and pinch master’s students Helm and Dominik Hornof to demonstrate nan Terrell-Penrose effect successful a lab for nan first time.

If we could propulsion it off, we would spot an constituent of relativistic physics that had ne'er been observed. We’d besides show that relativity is still offering surprises much than a period aft nan mentation was first introduced.

To understand what precisely nan Terrell-Penrose effect is, we first request to see nan Lorentz contraction, 1 of nan much puzzling predictions of typical relativity. According to this principle, nan magnitude of an entity moving astatine velocity v shrinks on nan guidance of mobility erstwhile measured by a stationary observer. The compression facet is √1 − v2/c2, wherever c is nan velocity of light.

Could a distant perceiver observe nan compression? Austrian physicist Anton Lampa, inspired by Albert Einstein’s conception of utilizing calibrated rods to measurement distance, discussed this mobility successful 1924. He recovered that nan different recreation clip of ray from 1 aliases different extremity of nan rod to nan perceiver obscured nan effect. For Lampa, nan ocular quality of nan Lorentz contraction was benignant of an unwanted broadside effect to beryllium eliminated. This was astir apt why his groundbreaking activity did not person nan attraction it deserved.

Dutch theoretical physicist Hendrik Lorentz, moving successful nan 1920s and 1930s, believed nan contraction (which would later beryllium named aft him) would beryllium visible. This presumption was not wide questioned until 3 decades later, erstwhile English mathematician Roger Penrose and American physicist James Terrell, moving independently, some arrived astatine a astonishing conclusion: The Lorentz contraction is not visible. An entity moving astatine astir nan velocity of ray wouldn’t look shortened. Instead it would look rotated. This intriguing result, published successful 1959, came to beryllium known arsenic nan Terrell-Penrose effect.

The optical illusion occurs because nan ray an perceiver sees from an entity did not each get reflected disconnected that entity simultaneously. Light from nan acold broadside had to commencement its travel a spot earlier than ray from nan adjacent side. For slow moving objects, this quality has nary effect. But ideate nan entity is moving incredibly fast.

In nan mini magnitude of clip it takes ray to recreation conscionable 1 meter, nan entity will person already moved noticeably. The ray that reaches your eyes simultaneously from different points originated astatine different moments successful nan object’s journey—creating nan illusion of rotation and elongation. In nan end, however, we don’t spot nan elongation: interestingly enough, it is precisely compensated by nan Lorentz contraction, yielding a purely rotated image of nan object.

Violet Frances

This striking effect had ne'er been observed because nan speeds required are astonishingly high, acold beyond what we tin execute pinch macroscopic objects successful a lab. As a result, nan Terrell-Penrose effect had agelong remained a theoretical prediction. But pinch nan exertion of nan SEEC project, we’ve escaped these limitations. By utilizing ultrafast lasers, high-speed cameras and precision-timing systems, we mimicked relativistic speeds and made nan Terrell-Penrose effect visible for nan first time. Our results were published successful Communications Physics successful May 2025.

Our experimental setup relies connected a fewer basal modern technologies. The first is simply a pulsed laser that emits bursts of ray conscionable 1 picosecond long—that’s 0.001 billionth of a second. Each beat travels outward for illustration a thin, spherical ammunition of light. This ray scatters disconnected nan entity we want to image, and nan reflected ray is collected by nan lens of an ultrafast camera.

That camera is nan 2nd important portion of technology. One of nan first attempts to seizure mobility astatine precocious velocity was made by English photographer Eadweard Muybridge successful 1878. Using a bid of accelerated exposures, he proved that astatine immoderate constituent successful a gallop, each 4 of a horse’s hooves time off nan ground. His cameras reached shutter speeds of astir a millisecond—incredibly accelerated for nan era. Today we’ve achieved vulnerability times orders of magnitude shorter—down to picoseconds aliases moreover femtoseconds. The camera we utilized has an vulnerability clip of only 0.3 billionth of a 2nd (that’s 300 picoseconds).

It relies connected what’s called a gated image amplifier. In this device, an incoming photon hits a photocathode, wherever it is converted to an particle via nan photoelectric effect. If nan gating is on, nan particle is accelerated toward a microchannel, wherever galore consecutive collisions pinch nan transmission walls create a unreality of secondary electrons. These past deed a phosphor screen, which converts them backmost to photons that are detected by nan CCD camera. The wide effect amplifies nan ray of each original incoming photon into aggregate photons astatine nan extremity point.

These devices are utilized by nan creation and subject task SEEC Photography. The task visualizes really ray moves crossed objects—a process truthful accelerated it is invisible to nan quality eye.

Violet Frances

SEEC Photography

Human eyes activity by creating images connected our retinas erstwhile ray scattered from objects reaches them. When an entity is illuminated, regions of it that are farther from america will beryllium imaged later than those that are closer. This clip quality is tiny—for a spatial separation of 1 meter, it amounts to 3 billionths of a 2nd (0.000000003 second). That hold is imperceptible to humans. But erstwhile we usage a camera pinch an vulnerability clip of little than 1 billionth of a second, we tin spot nan effect.

To grounds this phenomenon, nan SEEC task imaged respective scenes, including 1 of a canine skeleton. The camera captured a bid of frames, each 1 taken astatine a somewhat different clip pinch respect to an incoming laser pulse. In effect, each photograph captured a different “slice” of nan skeleton—the area momentarily illuminated by nan ammunition of light. This process enabled nan task squad to reconstruct light’s activity crossed nan aboveground arsenic if clip were slowed down. One bizarre accusation is that nan image of nan entity and its protector will nary longer coexist simultaneously.

To visualize nan Terrell-Penrose effect, we conscionable needed to use this instrumentality to a moving object. We carried retired our trial astatine Juffmann’s laboratory astatine nan University of Vienna. First we arranged nan laser, nan camera, and nan shape wherever nan entity would move. We installed SEEC’s intensified camera, which nan squad had bought connected eBay respective years ago. To our delight, nan instrumentality worked flawlessly—although it took immoderate activity for nan 1 of america overseeing nan setup (Helm) to get utilized to nan power package and an operating strategy older than she is. We past had to header pinch constricted laboratory space: to execute nan way we wanted, we had to steer nan pulsed laser retired of our lab, crossed a hallway and into a speech hallway connected nan different broadside of it. This setup restricted our clip slots to nan weekends.

Once we had established nan pulsed laser illumination, we placed 2 objects, a sphere and a cube, connected a movable cart astatine nan beforehand of nan speech hall. Hornof built nan objects from materials bought astatine a hardware store. To mimic nan Lorentz contraction that would beryllium happening if they were genuinely moving astatine relativistic speeds, he intentionally compressed them on nan axis of movement. (Without this measurement we would person seen elongation successful summation to nan rotation nan Terrell-Penrose effect should produce.)

Violet Frances

This image from nan research shows Terrell-Penrose’s rotating effect connected a Lorentz-contracted cube that appeared, done clever camera tricks, to beryllium moving astatine 80 percent of nan velocity of light.

From “A Snapshot of Relativistic Motion: Visualizing nan Terrell-Penrose Effect,” by Dominik Hornof et al., successful Communications Physics, Vol. 161; May 1, 2025 (CC BY 4.0)

We began by taking a series of 32 ultrafast photographs of some objects while they were stationary. For each photograph, we changed nan timing betwixt nan laser beat and nan camera’s shutter truthful that each image captured ray from a different “slice” of nan object. This created a time-lapse bid of ray walking crossed nan object’s surface, precisely arsenic nan SEEC task did. We changed nan timing by 400 picoseconds successful betwixt illuminating each adjacent slice, corresponding to a region of six centimeters betwixt slices.

When imaging nan contracted sphere, we moved it six centimeters betwixt each recording. Effectively, nan sphere appeared to recreation astatine a velocity of six centimeters per 200 picoseconds, which is 99.9 percent of nan velocity of light. We repeated this process 32 times and mixed nan recordings into 1 snapshot of nan object. The result? The sphere, which we had flattened into a circle, appeared rotated and spherical successful nan snapshot, conscionable arsenic Terrell-Penrose predicts.

The result pinch nan cube was similar. In this case, we moved nan entity 5 centimeters betwixt each recording, mimicking a velocity of 5 cm/200 ps—roughly 80 percent of nan velocity of light. Again, our resulting snapshot showed nan cube rotated, successful fantabulous statement pinch nan prediction from Terrell-Penrose. We recovered it absorbing that nan cube’s vertical edges besides appeared curved arsenic hyperbolae—a prediction made backmost successful 1970 by Ramesh Bhandari.

Our consequence shows that we tin study definite relativistic effects successful a laboratory by artificially reducing nan velocity of light. The Terrell-Penrose effect is confirmed: “Lorentz-contracted” objects look rotated, not contracted.

Our method opens nan doorway to testing different relativistic effects. Could we usage akin tricks to spot clip dilation aliases nan unusual relativistic displacement of starlight called stellar aberration? Might we beryllium capable to enact Einstein’s thought research astir lightning strikes seen from a moving train, which shattered nan thought of absolute clip and simultaneity?

Ultimately we transferred Wells’s dream of slowing down clip into existent life. Our research revealed an facet of physics ne'er seen before, acknowledgment to a serendipitous operation of art, subject and subject fiction.