As we know, no one can move at a speed greater than twice the speed of light. In reality, no object that you or I possess can move faster than the speed of light in any direction. Einstein’s theory of relativity seems to suggest that this is impossible, but what if it could happen? Some unusual particles may move at speeds exceeding that of light – could this allow them to travel backward in time?
The Universal Speed Limit
Albert Einstein’s theory of relativity is one of the most useful physical theories we have at present. According to this theory, the speed of light serves as the universal speed limit for anything that has mass. Relativity states that no object with mass can move faster than the speed of light.
An object with mass must be supplied with additional energy to accelerate. Therefore, the speed of an object is proportional to the energy provided to it. Einstein’s relativistic equation indicates that an infinite amount of energy is required to accelerate any object with mass to the speed of light, regardless of how much mass it has.
The speed of light in a vacuum is 299,792,458 meters/second, denoted as c. This is an important fundamental physical constant in many fields of physics. So, how was the speed of light determined, and is there anything that can actually exceed it? In fact, according to Einstein’s special relativity, light travels in a vacuum so quickly that nothing in the universe can move faster than it.
However, all energy sources that we are aware of are limited in some way. Indeed, it can be imagined that the universe has a finite amount of energy to begin with. This means that the universe lacks the necessary energy to accelerate anything with mass to the speed of light. As long as we have mass, we will not be able to move at twice the speed of light.
Tachyons
Anything with “normal mass” must adhere to this universal speed limit. However, tachyons, a hypothetical subatomic particle, could potentially move faster than the speed of light. Although a type of hypothetical particle, we cannot prove that it does not exist, and relativity cannot rule out the possibility of such occurrences.
The German physicist Arnold Sommerfeld is credited with being the first to describe tachyons. However, George Sudarshan, Olexa-Myron Bilaniuk, Vijay Deshpande, and Gerald Feinberg (who first named this particle in the 1960s) laid the theoretical foundation for tachyon research. Tachyon fields appear in many theoretical frameworks, such as Bosonic string theory.
In 1676, by observing the motion of Jupiter’s moons, Danish astronomer Ole Romer calculated that light travels at a finite speed. According to the American Museum of Natural History in New York City, by 1678, based on Ole Romer’s data, Dutch mathematician and scientist Christiaan Huygens became the first to attempt to determine the actual speed of light.
If tachyons exist, they must always move faster than the speed of light. Tachyons cannot slow down to below the speed of light, just as objects with normal mass cannot accelerate beyond the speed of light. Some physicists hypothesize that if tachyons exist, they would continuously travel backward in time. Therefore, tachyons are often used to describe time travel in science fiction.
There is speculation that one day we might be able to create a time machine using tachyons. However, since we currently lack the ability to confirm the existence of tachyons, this remains a distant dream at this time.
A Shortcut?
The fact that we cannot move faster than the speed of light is disappointing. 4.35 light-years is the distance between us and the closest star to the Sun. It would take over four years to reach it if you were traveling at the speed of light. The farthest star we have ever discovered lies 28 billion light-years away from Earth. Therefore, even if you spent your entire life traveling, you would never reach that star.
However, relativity allows for the existence of “wormholes.” A wormhole is a shortcut between two locations in space. Under normal conditions, a star might be 4.5 light-years away from us, but passing through a wormhole could bring it just hours away.
But in 1905, Einstein’s Special Theory of Relativity forever changed the way physicists view the universe by tying mass and energy into a simple yet profoundly important equation, E=mc². Essentially, this equation predicts that nothing with mass can reach the speed of light, let alone exceed it. Humanity’s most successful efforts to approach the speed of light lie in powerful particle accelerators such as the Large Hadron Collider (LHC) at CERN or the Tevatron in the United States. These massive machines (the LHC even has a circumference crossing the Alps, located in both France and Switzerland) can accelerate subatomic particles to 99.99% of the speed of light; however, according to Nobel laureate physicist David Gross, these particles will never reach the cosmic speed limit.
For all we know, it may be possible to reach the farthest points of the universe in a lifetime if there are actual wormholes somewhere in our universe. However, wormholes, like tachyons, are only theoretical at this point.
We can try to imagine what it would feel like to move faster than light, even though the reality is that we cannot actually do so.
