The concept of time travel has long been discussed by physicists, with the theory of general relativity suggesting that it is possible to travel back in time. One of the most intriguing entities in the theory of relativity is tachyons, the hypothetical particles that can beat the speed of light.
Time Travel and the Speed of Light
No object in the universe has demonstrated the ability to travel faster than the speed of light. Massless particles like light are the only entities capable of achieving this speed. This means that anything with even a tiny amount of mass will find it impossible to reach the speed of light. This is because the faster an object moves, the more massive it becomes. At light speed, an object's mass becomes infinite and would take infinite energy to accelerate.
The speed of light is not just an expression of how fast an object moves. It also demonstrates how fast things can influence each other. In other words, every interaction in the universe is limited to the speed of light.
Light is also the speed of causality, or the fastest way a cause can generate an effect. It also refers to the fastest way events can influence one another. It is going faster than light, which means going faster than causality. It also means that traveling faster than the speed of light means going faster than time itself. This can be interpreted as a faster-than-light travel, automatically allowing time travel into the past.
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Traveling in the Past With Tachyons
The universe comprises various types of particles that interact with each other and give off energies of different styles and spectrums. Among these particles, a tachyon is a quasiparticle capable of traveling faster than light. Although they are still not detected physically in any experiment, their existence has been mathematically hypothesized.
The idea of particles traveling faster than light was first conceptualized in 1904 by German physicist Arnold Sommerfeld. It was first called meta-particles by Sommerfeld until Gerald Feinberg coined the term tachyon in 1967 in his study about faster-than-light particles and their kinetics concerning special relativity.
Tachyons exhibit an unusual property where the increase in speed results in a decrease in energy. Like other subatomic particles, the power increases with every rate increase. Therefore, it would require infinite energy to slow down a tachyon to the speed of light.
As tachyons move at speeds greater than the speed of light, observing them in real time would be impossible. After they pass through a point in space, the observers would see two images of them. This is because the observer would witness an appearing and a departing image in the opposite direction. This is called the double image effect, a phenomenon normally observed in a superluminal object's light field.
If tachyons can move faster than light, then they would violate causality as explained by the theory of relativity and can give rise to situations such as the Grandfather's paradox. There would be disagreement on the simultaneity of two special events at two points in space, a phenomenon that cannot occur in different inertial frames of reference.
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