What is the speed of light, and will humanity ever be able to surpass it?

The speed of light traveling through a vacuum is precisely 299,792,458 meters per second. According to Albert Einstein's special theory of relativity, which underpins much of modern physics, nothing in the universe can move faster than light.

As early as the 5th century BC, Greek philosophers such as Empedocles and Aristotle had differing views on the nature of the speed of light. Empedocles proposed that light, regardless of its composition, must travel and therefore have a speed. In contrast, Aristotle, in his treatise "On Sensory Perception," refuted this hypothesis by claiming that light, unlike sound and smell, travels instantaneously and thus cannot possess speed. Aristotle was certainly mistaken, but it took centuries to prove him wrong.

In the mid-1600s, Italian astronomer Galileo Galilei conducted an experiment with a colleague. The scientists stood on hills less than a mile apart, each holding a lantern. The experiment involved one scientist turning on his lantern while the other was to do the same only after seeing the light from the first lantern. Unfortunately, in Galileo's experiment, the distance between the hills was not large enough to measure the speed of light; however, he concluded that light travels at least ten times faster than sound.

In the 1670s, Danish astronomer Ole Rømer attempted to create a reliable timetable for sailors at sea but inadvertently devised a new method to estimate the speed of light. To create astronomical clocks, he recorded the precise times of eclipses of Jupiter's moon Io, visible from Earth. Over time, Rømer noticed that the eclipses of Io often differed from his calculations. He observed that the eclipses seemed to lag at moments when Earth and Jupiter were moving apart. In modern terms, this phenomenon is known as the Doppler effect, which refers to the change in frequency and wavelength of radiation due to the motion of the source relative to the observer. You can learn more about the effect from this article by "TechInsider."

In witnessing this intriguing phenomenon, Rømer intuitively suggested that he sometimes miscalculated due to the increasing distance between Io and Earth, indicating that light indeed takes some time to travel from point A to point B. Based on his assumptions, Rømer tried to use his observations to estimate the speed of light. Since the dimensions of the solar system and Earth's orbit were not yet precisely known, the calculations were quite challenging, but eventually, the scientist managed to present the first estimates of the speed of light at 200,000,000 m/s.

In 1728, English physicist James Bradley devised a new calculation method for the speed of light based on the changing visible positions of stars. According to the American Physical Society, through his research, he estimated the speed of light to be 301,000,000 m/s.

In the mid-1800s, two more attempts were made to find a more accurate value for the speed of light. French physicist Hippolyte Fizeau directed a beam of light at a rapidly spinning cogwheel with a mirror positioned 8 kilometers away. The idea of the experiment was to measure the time it took for the reflected beam to return. Around the same time, another French physicist, Léon Foucault, conducted a nearly identical experiment, but instead of a wheel, he used a rotating mirror. Both experiments yielded very similar results—about 1,000 miles per second or 1,609,000 m/s.

According to the University of Virginia (USA), another scientist who sought to unravel the mystery of the speed of light was Polish-born Albert A. Michelson, who grew up in California during the Gold Rush. He developed an interest in physics while studying at the United States Naval Academy. In 1879, he attempted to replicate Foucault's experiment to determine the speed of light, but Michelson made some adjustments—he increased the distance between the mirrors and used extremely high-quality mirrors and lenses.

As a result, the researcher obtained a value of 299,910,000 km/s, which was considered the most accurate measurement of the speed of light for the next 40 years until Michelson revised it himself. During his second attempt to measure the speed of light, the scientist sought to determine the time it took for light to traverse a precisely measured distance between two hills. Shortly before his death in 1931, he undertook a third attempt, during which he constructed a one-mile-long tube made of corrugated steel. The conditions inside this tube were very close to a vacuum to prevent any factors, including air, from affecting the final result. Ultimately, the scientist achieved his goal—he obtained a number that was very close to the modern value of the speed of light.

Modern science fiction embraces the idea of traveling through space at speeds exceeding that of light. Such journeys make countless sci-fi franchises realistic—by having some sort of warp core, heroes can traverse vast cosmic distances in mere seconds. For instance, characters in "Star Trek" possess this capability.

However, while traveling faster than light cannot be deemed absolutely impossible, humanity would need to employ rather exotic physics to achieve it. The problem is that the special theory of relativity guarantees that the human body would be destroyed long before we reached a sufficiently high speed. Therefore, to travel faster than light, a special ship might be necessary to create a space-time bubble around itself. Admittedly, that sounds exciting!