What would happen to humans if they could travel at speed of light?

In the realm of science fiction, individuals often contemplate the possibility of achieving the speed of light. However, a critical question arises: could the human body withstand such incredible speeds, and what would be the consequences?

Let's hypothetically assume, although it's not feasible, that a human could move at the speed of light, which is approximately 299,792,458 meters per second (983,571,056 feet per second) or about 186,000 miles per second. Moving at a constant high speed itself wouldn't pose a problem since humans can't feel constant velocity, making it almost imperceptible.

The primary challenge arises during acceleration to reach such speeds. Excessive acceleration force can be detrimental, even fatal. According to Michael Pravica, a physics professor at the University of Nevada, Las Vegas, at high accelerations, "your blood will have a hard time pumping to your extremities." Most humans can tolerate acceleration forces of about four to six times that of gravity (4 to 6 g) for a short duration. Beyond this, blood circulation becomes constrained, leading to loss of consciousness and, if unabated, eventual death due to oxygen deprivation.

Certain individuals, like fighter pilots, undergo training to endure high g-forces, using techniques such as muscle tensing and specialized suits to withstand up to 9 g briefly. However, if acceleration to light speed occurred rapidly, as depicted in "Star Wars," the impact of over 6,000 g would result in a person being flattened, according to Omni Calculator's g-force calculator.

Attempting a more gradual acceleration, such as 2 g, to reach light speed would take over five months in a straight line with no air resistance. At 1 g, the acceleration of free fall, it would require over 11 months. Nevertheless, reaching light speed proves impossible due to the finite mass of objects. Einstein's theory of special relativity explains that as an object approaches the speed of light, its mass increases, requiring infinite energy to maintain that speed.

While particle accelerators can propel subatomic particles close to light speed, the vast energy required for a human makes achieving such speeds extremely improbable and likely to violate the laws of physics. If near light speed were attainable, the effects of relativity on time would come into play, causing time to pass more slowly for the individual moving at that speed.

Einstein's theory also suggests that everything is relative, and our planet's motion within the universe might already bring us close to the speed of light, depending on our motion relative to other celestial bodies. As Pravica notes, "Everything is relative," as demonstrated by Einstein's groundbreaking work.