Light is the fastest moving thing in the universe. So what would happen if the speed of light were much, much slower?
In a vacuum, the speed of light is about 186,000 miles per second (300,000 kilometers per second). If it were orders of magnitude slower, people would immediately take notice.
Any gamer can experience this hypothetical scenario in a computer game created by Gerd Kortemeyer, Director of Educational Development and Technology at ETH Zurich, a University of Science, Technology, Engineering and Mathematics in Switzerland, and his colleagues. In the game you can see the bizarre effects of changing colors and brightness, and even changes in the perceived lengths of objects that would be the result of a much slower speed of light.
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Man’s slow speeds
Even at our fastest speeds, humans are slow compared to light.
“The fastest a human has traveled is about 0.0037% of the speed of light, and you have to be in some sort of spacecraft to reach those speeds,” Philip Tan, a researcher at MIT Game Lab, told WordsSideKick.com.
But by doing thought experiments, physicists have determined that unusual things would happen if humans could travel at near light speeds, said Kortemeyer, who is also an associate professor of physics at Michigan State University. According to Albert Einsteins theory of special relativity – which explains how speed affects mass, time and space – time would be slower, we would measure objects as being shorter when we whizzed past them and Doppler effect would become visible to light, among other changes.
The same changes would occur if the light slowed down instead of people speeding up. In either case, we would be moving at almost the speed of light.
A slower speed of light
While Kortemeyer worked as a visiting professor at MIT, he, Tan, and colleagues at MIT Game Lab created a computer game to illustrate what the world would look like if the speed of light were slow enough for the particular theory of relativity to be noticeable in everyday life. In the game, released in 2012 and called “A slower speed of light, “the player controls a character that collects beach ball-like balls. Each time the character collects one of the 100 balls, the speed of light is lowered.
In fact, the speed of light would not slow down as it does in the game. The speed of light in a vacuum never changes and is constant for each observer. But the speed of light changes depending on the materials it passes through, but it does not change the effects of special relativity or how we perceive them, Kortemeyer said.
However, if we could witness special relativity theory, we would notice changes in color, time, distance, and brightness, and the team incorporated these effects into the game.
As the speed of human motion approaches the speed of light, something called the relativistic Doppler effect becomes noticeable. To understand this, remember the light acts as both a particle and a wave. As a wave, it is characterized by its wavelength or the distance from peak to peak, which determines its color and its frequency, or how many peaks pass in a given time.
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Similar to the way that, according to the Doppler effect, when approaching a sound source, it causes its frequency or pitch to increase, as the wave crests reach your ear faster and faster, making its wavelength appear shorter by moving towards a light source. apparently color of the light against the blue and violet end of the color spectrum, Kortemeyer said. Moving away from an object, on the other hand, shifts its apparent color toward the red end of the spectrum. In short, “the thing that comes towards you looks more blue, or the thing that moves away from you looks redder,” Kortemeyer said.
Changes in time and distance
Perhaps one of the most famous effects of special theory of relativity is that for a human being moving near the speed of light, time becomes slower. In this scenario, a person moving at almost light speed would age more slowly. This effect is called time extension.
In the game, “technically, you experience time expansion, but without having anything to compare it to, it doesn’t really matter,” Tan said. Time extension may not be noticeable during the game, but at the end, players see a screen informing them that less time has passed for them than has gone for a stationary clock, Tan said. Time expansion, like the other effects of special relativity, happens during the game because the character of the game moves close to the speed of light.
Another effect of special relativity is that the lengths of objects that move near the speed of light – or stationary objects when you whiz past them at almost light speed – are shortened. This is called longitudinal contraction. But the effect is complicated, Kortemeyer said. Objects that zoom close to the speed of light may experience longitudinal contraction and may be shorter according to measurements from a stationary observer, but they would actually appear longer in front of that person’s eyes due to another effect of special relativity called the runtime effect, Kortemeyer said.
Say, for example, that a bicycle is coming towards you. The light from the front of the bike has a shorter distance to travel to your eyes than the light from the back of the bike. As a result, you see the front of the bike as it was recently, and the back of the bike as it was longer in the past, where the bike was further away. “Overall, it makes the bike look longer,” Kortemeyer said. Sometimes the same effect can make objects appear skewed.
In other words, if the speed of light was much slower, objects moving close to that speed may look longer and / or become skewed for stationary observers.
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Changes in brightness
When you walk in the rain, you may notice that you get wetter in the front than in the back. When you go into the rain, you encounter more raindrops than you would stand still, but the front of you protects the back of you from the extra raindrops. Something similar would happen if you moved close to the speed of light, Kortemeyer said.
This is because light sometimes behaves like a collection of particles, called photons, which are like tiny light droplets. When you move towards an object in the computer game, it looks brighter than it does when you stand still because you go into its photons. This is called the spotlight effect.
Mr. Tompkins and Wonderland
Kortemeyer and Tan were not the first to imagine a world at a slower speed of light. In 1939, physicist George Gamow published a picture book called “Mr. Tompkins in Wonderland,” in which the title character cycles through a city at a slower speed of light and experiences relativistic effects. Einstein “really loved the little booklet,” Kortemeyer said.
What could the great physicist think of “A Slower Speed of Light”? “Curiosity could have made him play in the first place, because if you are to believe historians, he already asked at the age of 16 what you would see if you rode on a beam of light – which of course you can not, but in the game you can almost reach the speed of light, “Kortemeyer said. “But then I think he just wanted to play the video game until he became hopelessly motion sick – most physicists remain playful.”
Originally published on Live Science.