Traveling At The Speed Of Light: Falling Or Floating?

The speed of light is often touted as the ultimate speed limit in the universe. But what would happen if you were to travel at the speed of light? Would you still fall?

Acceleration to the speed of light

According to Einstein's theory of relativity, it is impossible to accelerate an object with mass to the speed of light. As an object with mass approaches the speed of light, its mass increases exponentially and would become infinite at 100% of the speed of light. This infinite mass would require an infinite amount of energy to propel and maintain that speed, which is impractical and breaks the laws of physics.

However, massless particles, such as photons, can travel at the speed of light. Photons are massless packets of electromagnetic energy that travel at a constant speed of light once emitted.

While it is impossible to accelerate an object with mass to the speed of light, it is possible to get arbitrarily close. Particle accelerators have propelled electrons to over 99.9% the speed of light.

If an object with mass could somehow reach the speed of light, it would experience several phenomena, including time dilation and altered vision. Time would move slower for them compared to a stationary observer, and they would only be able to see through a narrow, tunnel-like window in front of them. Additionally, the massive acceleration force required to reach the speed of light would be harmful and even fatal to humans.

Time dilation

Additionally, time dilation can also be influenced by gravitational fields. The closer an observer is to a large mass, the slower time will appear to pass for them. For instance, NASA has hypothesised that a clock placed in orbit 6 miles (10 kilometres) from a black hole with the same mass as the Sun would take around 1 hour and 10 minutes to show a 1-hour difference.

Mass increase

According to Einstein's theory of special relativity, as an object with mass gets closer to the speed of light, its observed mass starts to increase. This is because, as per the theory, mass and energy are interchangeable, and so can be converted from one to the other. As an object moves faster, its energy increases, and this increase in energy is what we refer to as 'the increase in mass'.

This increase in mass is incredibly small at everyday speeds, but as an object approaches the speed of light, its mass becomes infinitely large. This is because the speed of light is squared in Einstein's equation, so tiny amounts of mass contain huge amounts of energy. As a result, an infinite amount of energy would be required to make an object move at the speed of light, and so it is impossible for any matter to travel faster than light speed.

This increase in mass has been proven by experiments with particle accelerators, which have accelerated particles to speeds where their mass is thousands of times greater than their mass at rest.

Infinite energy

As an object with mass approaches the speed of light, its mass increases. At the speed of light, an object's mass becomes infinite. This is because, as Einstein's theory of relativity explains, the speed of light is constant and independent of the observer.

According to Einstein's mass-energy equivalence equation, E=mc^2, an object's mass and energy are interchangeable. This means that an object's energy also becomes infinite at the speed of light. Therefore, to reach and maintain the speed of light, an infinite amount of energy is required.

This is why no object with mass can move at or faster than the speed of light. The closer an object gets to the speed of light, the more energy is required to accelerate it further, creating a vicious cycle. As one source puts it, "the closer you get to lightspeed, the more utterly insane the energy requirements become".

However, massless particles, such as photons, can travel at the speed of light.

Light speed travel is impossible

Firstly, it is impossible to accelerate to the speed of light. Acceleration requires force, and the amount of force needed to accelerate an object is proportional to its mass. As an object approaches the speed of light, its mass increases exponentially. Eventually, the object's mass would become infinite, requiring an infinite amount of energy to continue accelerating.

Secondly, even if it were possible to reach the speed of light, it would be impossible to avoid colliding with particles and debris in space. While space is mostly empty, it is not entirely devoid of matter. At light speed, even a small particle would have the energy of a nuclear bomb.

Thirdly, the speed of light is a cosmic speed limit. According to Einstein's theory of special relativity, the speed of light is constant and independent of the observer. This means that it is impossible for an object with mass, such as a spacecraft or a human, to reach or exceed the speed of light.

Finally, light-speed travel would result in time dilation, where time appears to slow down for the traveller relative to someone stationary. At 90% of the speed of light, a traveller would experience time passing at half the rate of someone on Earth. As the speed of light is approached, the time dilation effect would become more pronounced, eventually resulting in time stopping altogether for the traveller.

While light speed travel may be a staple of science fiction, it remains a physical impossibility. The laws of physics, as we currently understand them, place firm constraints on the potential for superluminal travel.

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