What would happen if you moved at the speed of light?

In science fiction, people often find a way to move at the speed of light. But you might find yourself asking, could your body survive going so fast? What would happen to it?

First, let's assume that it is possible — though it is not — for a human to move at the speed of light, which is 299,792,458 meters per second (983,571,056 feet per second), or about 186,000 miles per second. There's no issue, per se, with a person moving at a very fast constant speed. Humans can't feel constant velocity, so you wouldn't even necessarily notice you were moving that fast.

Your biggest issue would be acceleration — actually reaching that speed. Too much acceleration force can hurt, and even kill, us. At high accelerations, "your blood will have a hard time pumping to your extremities," said Michael Pravica, a professor of physics at the University of Nevada, Las Vegas.

Most humans can handle acceleration forces of about four to six times that of gravity (4 to 6 g) for a short period of time. As the g-force increases, your body's ability to circulate your blood from your feet to your head becomes limited. As your blood begins to pool, you will pass out, and if the force doesn't lessen or stop, you will eventually die as your body is starved of the oxygen your blood transports throughout your body.

Fighter pilots and other people who experience high levels of g-force are taught techniques to keep from passing out, such as tensing muscles in their extremities, and they use special suits to withstand up to 9 g for short periods of time. But if you were to accelerate to light speed in a few seconds — like in the "Star Wars" movies — you would quickly become a human pancake as the force of over 6,000 g slammed into you, according to Omni Calculator's g-force calculator.

If you wanted to accelerate to light speed more safely — say, at 2 g — it would take over five months to accelerate to light speed, assuming you were moving in a straight line and there was no air resistance. At 1 g, the acceleration of free fall, it would take over 11 months.

Unfortunately, reaching this lofty speed turns out to be impossible. "You cannot go at the speed of light, given that you have a finite mass," Pravica said.

Einstein's theory of special relativity shows that as an object with mass gets closer to the speed of light, the mass starts to increase as it nears the speed of light, Pravica said. If an object could reach the speed of light, it would become infinitely massive and would require infinite energy to maintain that speed.

Still, humans have gotten some things to go very, very fast — if you can call subatomic particles "things." Particle accelerators can get particles like electrons to over 99.9% the speed of light, Pravica said. But there's a big difference between getting an electron to move that fast and launching a person at that speed, which would require so much energy as to be extremely improbable, even if it didn't break the laws of physics.

If you could move at near light speed, you would experience the effects of relativity on time, Pravica said. Time would move more slowly for you than for people moving at more everyday speeds, though your experience of time wouldn't change. If you could observe people moving at "normal" speed, Pravica said, they would appear to be moving in slow motion.

There is one sense in which we could move at close to the speed of light. Our planet and everything in the universe are constantly moving. Earth is rotating and revolving around the sun, and even our galaxy is in motion. It's possible that if we were moving away from a galaxy very quickly — and that galaxy were also moving away from us — we would be moving, relative to that galaxy, at near the speed of light. It's possible that we already are.

"That's what Einstein showed," Pravica said. "Everything is relative."

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• Omits
Well, the question seems to be a non starter!
• Classical Motion
Even if you had the where with all and 1 year to achieve c, I don't think one could survive it without very heavy and firm shielding. Even though there are only a few particles in a cubic of space, at that speed those particles become a flux. It would shred your body structure.....and craft structure.

Imagine the flux if going 100 or 1000 c. These would be c collisions. Producing a huge flux of disintegrating, ionizing charge fragments.

Like standing in front of a CERN stream.
• Atlan0001
What is explained is closed systematic! Open systemic, you at '0'kps never approach the speed of light 'c' ((+)300,000kps |0| (-)300,000kps) closer than (+/-)300,000kps. It is a "go with" constant.

Also, according to the Heisenberg uncertainty principle if you know your velocity in the universe (in this case to exactitude) you can never know your position (in this case you'd be all over the map (in the dead center of Stephen Hawking's "Grand Central Station" of the universe, aka where Einstein landed in his mind's eye trip to the speed of light))!
• Robert Lucien Howe
This is a question where we get a reverse Dunning Kruger effect - it is beyond the region of physics that science really knows or understands and everything said ends up being essentially speculation.

What everyone does know is that mass dilation increases the effective mass of objects near the speed of light until at light an object's mass becomes infinite. (making that impossible) Similarly time dilation may slow the speed of time at the speed of light to zero. From the objects perspective as it accelerates it becomes infinitely fast.

A fairly obvious point is that the speed of light is an intersection point between the STL and FTL realms of speed. Another obvious point is that light itself does have mass though zero rest mass.

If the mass of a massed object could somehow be balanced to zero then it could move at the speed of light. In fact it would immediately accelerate to the speed of light - for 'free'. There are two basic hypothetical approaches to balancing mass to zero - either adding something with negative mass or creating some kind of 'shield' that hides the mass. Curiously if we could create one a real Schrodinger box would be a possible way of achieving the second.

So maybe not completely absolutely impossible after all.
• Atlan0001
This is a question where we get a reverse Dunning Kruger effect - it is beyond the region of physics that science really knows or understands and everything said ends up being essentially speculation.

What everyone does know is that mass dilation increases the effective mass of objects near the speed of light until at light itself this in theory becomes infinite. Similarly time dilation may slow the speed of time at the speed of light to zero. From the objects perspective as it accelerates it becomes infinitely fast.

A fairly obvious point is that the speed of light is an intersection point between the STL and FTL realms of speed. Another obvious point is that light itself does have mass though zero rest mass.

If the mass of a massed object could somehow be balanced to zero then it could move at the speed of light. In fact it would immediately accelerate to the speed of light - for 'free'. There are two basic hypothetical approaches to balancing mass to zero - either adding something with negative mass or creating some kind of 'shield' that hides the mass. Curiously if we could create one a real Schrodinger box would be a possible way of achieving the second.

So maybe not completely absolutely impossible after all.
Some (not me except in picturing) have already been there, done that, in the math. The total mass matter and energy of the universe equals zero. Truly bothered those who came up with reduction to zero (0-point) until Stephen Hawking told them not to let it bother them. He told them the universe is always there (at the 0-point of infinity (the zeroing point of the infinities -- the infinities remaining though not locally, relatively, finitely)).
• Robert Lucien Howe
Some (not me except in picturing) have already been there, done that, in the math. The total mass matter and energy of the universe equals zero. ..
Worked that out myself once. Realized that with neg mass we could have a universe with a zero net mass. Never had or found a way to prove it or test it though.

Dark matter could be neg mass maybe - would be fascinating..
• DC8Captain
KillJoy
• Questioner
At the speed of light one's mass becomes infinite,
but is that mass symmetric or only in the direction of travel?
Otherwise one would turn into an actual black hole at the speed of light.
All light would be photon sized black holes.
• Preem
What would happen if you moved at the speed of light? Well, you can't. :grinning: