# The Barrier of Speed of Light

Every type of electromagnetic wave propagates at the speed of light, including visible light. In a vacuum, the speed of light is a universal constant, which is denoted by the symbol “c”. The speed of light is 299,792,458 m/s, approximately 186,000 miles per second. In 1676, Ole Rømer showed that light moves at a limited speed by examining the apparent movement of lo (Jupiter’s moon). Later, more precise calculations of its speed arose during the following centuries. James Clerk Maxwell put forward that visible light is a type of electromagnetic wave, so it moves at speed “c”. The speed at which visible light travels through transparent substances, such as air or glass, is much less than c. Likewise, the speed of electromagnetic radiation in cables is relatively slower than c.

## Universal Speed Limit

Albert Einstein proposed that the light speed relative to any inertial frame of reference is always constant. In fact, it does not depend on the light source’s motion. He studied the theoretical outcomes of that postulate by developing the theory of relativity. Then, he showed that quantity “c” has much more significance outside of the realm of electromagnetism and light.

As per the special theory of relativity, the speed of light in vacuum c is the upper threshold for the speed at which ordinary energy or matter can move through any physical medium. According to this theory, nothing in the Universe can move faster than the speed of light. The theory states that as an object approaches light speed, the object’s mass becomes limitless or infinite (not possible). This means that light speed functions as a speed threshold in the entire Universe. It acts as the only limiting speed in the Universe, an upper bound to the moving speed of signals and to the movement of all physical particles. Light is made of photons which have zero rest mass. This intrinsic property of a photon allows them to achieve such tremendous speed. However, despite the common concept of light as a universal speed limit, researchers have been looking for particles that travel faster than light.

## Theoretical Probabilities Beyond the Speed of Light

We cannot travel through the vacuum of space beyond the speed of light. But in terms of theoretical probabilities, this speed limit is not consistent (under the background of some specific conditions). Light shows both wave and particle characteristics, so it can be considered both a wave and a particle. This is called wave-particle duality. When light is examined as a wave, there are various reasons why particular waves can propagate faster than colourless light in a physical medium. However, these scenarios are just limited to certain mediums. As far as the speed of light (in a vacuum) is concerned, there are some probable contenders that could break the light speed “c” in a vacuum. Scientists at CERN have found subatomic neutrino particles that probably travelled at a speed faster than light. OPERA scientists launched thousands of neutrinos that began at CERN. They discovered that the neutrinos crossed 730 km, roughly 60 nanoseconds faster than previously assumed (here, the normal speed of neutrinos is considered to be the same as that of light).

Tachyons are another type of theoretical particle that is believed to exceed the speed of light. A tachyon or tachyonic particle is a theoretical particle that always moves faster than light. As per theoretical calculations, it could exhibit bizarre behaviour of increasing in speed as its energy reduces. It could also need infinite energy to slow down to light speed. No consistent experimental evidence for its existence has been found. If tachyons exist, then it would breach the law of causality and open the door for time non-linear time travel.