What Really Happens to the Human Body at Near Lightspeed?
In the realm of science fiction, spacecraft capable of reaching or surpassing the speed of light allow for extensive journeys across the universe. However, within our earthly confines, propelling even a heavy rocket up to the velocity of light—which is approximately 299,792,458 meters per second or about 670,616,629 miles per hour in a vacuum—is physically unattainable. "The speed of light is reserved only for objects without mass," explains Gerd […]
In the realm of science fiction, spacecraft capable of reaching or surpassing the speed of light allow for extensive voyages across the universe. However, within our earthly confines, hurtling through space at the velocity of light—299,792,458 meters per second or about 670,616,629 miles per hour in a vacuum—in an unwieldy rocket remains firmly in the domain of fantasy. physical impossibility “It’s how fast massless objects move,” he explains. Gerd Kortemeyer , an associate professor emeritus of physics at Michigan State University, explains that anything possessing mass can’t attain that velocity. Even particles without mass are constrained by the speed of light. "This is frequently referred to as the cosmic speed limit since nothing surpasses this speed," Kortemeyer states.
Twice as unlucky for those of us who are keen to explore distant galaxies—even when traveling at near Traveling close to lightspeed isn't an option. "Going near the speed of light compared to our home planet wouldn't be feasible or safe," explains the physicist.
Apart from complex theoretical explanations, using enough fuel and energy to accelerate any manned spacecraft to such speeds would be impractical. According to Kortemeyer’s computations, accelerating a craft weighing 10 metric tons (considerably light and small) to 99% of the speed of light would require an enormous amount of resources. than most spacecraft ), while increasing at an acceptable g-force would require over 200 times the annual energy consumption on Earth. This calculation assumes a completely efficient fuel, wherein mass transforms into propulsion energy without any heat loss—a scenario that defies known physics. second law of thermodynamics .
The nearest we've gotten to achieving light speed is propelling minuscule individual atoms to incredibly high velocities. approximately 99.99999896 percent the speed of light at the Large HadronCollider.
However, let's set aside these considerations momentarily and envision what approaching light speed might entail. Assuming we possessed an ideal, highly efficient energy supply, ample amounts of it, a spacecraft designed to endure such conditions, along with the boldness—what kind of experience would near-light-speed travel offer us?
Surely enough, things took an odd turn.
Why is lightspeed considered something remarkable?
First, it's crucial to grasp some of the peculiarities of traveling at light speed. It doesn't just At this velocity, it's also "one of the basic constants of nature," as Kortemeyer points out. Ever since the 1600s, astronomers' observations of planetary motions have been instrumental. suggested the velocity of light And in 1865, James Clerk Maxwell inferred that light is an electromagnetic wave and determined its velocity, which closely matches the currently accepted value we know today. landmark physics paper , “ A dynamic theory of the electromagnetic field .”
Next, Einstein revolutionized our grasp of physics. In 1905, his theory of special relativity introduced the concept of spacetime as an integrated cosmic sheet, linked through the constant "c," which delineates the connection between energy and mass. When he computed this value, coincidentally, it matched perfectly with what was expected. equivalent to the velocity of light This is the renowned E=mc^2 equation.
At its core, special relativity asserts that the speed of light remains constant, whereas time—the fourth dimension—adjusts according to an object’s movement. Consequently, moving objects perceive time differently compared to stationary ones. On everyday Earth velocities, these effects aren't detectable. However, approaching the speed of light brings about significant differences due to what we call time dilation; more on this later.
Moreover, due to the special connection between lightspeed and spacetime, this velocity stays consistent regardless of the observer's own speed. Think about being inside a vehicle on a highway for a second. Suppose you're cruising along at a steady pace of 30 miles per hour and another car zooms past you going 60 miles per hour; relatively speaking, that quicker car moves away from you at a rate of 30 mph compared to your movement. Yet, if you tried to chase after a photon reaching speeds as high as half the speed of light, that photon would still recede from you at exactly the speed of light itself. "This constancy—it's always the speed of light—regardless of motion sets it apart," explains Kortemeyer.
Combined, these ideas result in an exhilarating journey when nearing the speed of light.
How might traveling at speeds close to light feel?
Hues and luminosity would become altered and appear quite distinct, as demonstrated in this 2012 simulation Created by Kortemeyer and colleagues at MIT, this straightforward game aims to demonstrate the impacts of traveling close to the speed of light through relativity. It takes place in an alternate reality where light travels significantly slower than usual and continues to decelerate as you move within the environment. Within this scenario, even though you can't quite attain or surpass the slowed-down speed of light, you could comfortably walk at speeds approaching it.
Just like when an ambulance races past you with its sirens wailing, causing the sound to seem higher-pitched as it approaches and lower-pitched as it recedes, so too would your vision be affected. If you moved toward something, it would look more blue because the light waves compress and shorten. Conversely, moving away from something would cause it to appear redshifted due to the elongation of those same light waves.
Approaching something rapidly enhances how brightly you perceive it due to what’s known as the spotlight effect. Kortemeyer likens this occurrence to sprinting through rainfall. When moving swiftly during heavy precipitation, more droplets strike your body from ahead, causing your clothing to become drenched faster. Within the simulated environment of the game, these metaphorical water droplets equate to photons. Traveling within a ray of light nearly at the speed of light implies that many additional light particles will simultaneously reach your eyes.
If that isn’t bizarre enough, think about how this might affect our perception of time. Recall the principle of time dilation? Due to the curvature of spacetime needed to maintain the universal speed limit of light, someone hurtling through space close to the speed of light would experience aging much slower compared to those staying behind on Earth. A classic illustration of this phenomenon can be seen in twin paradox thought experiment. The effect of time dilation, along with the difference between time experienced at rest versus time encountered when moving at a specific speed, demonstrates be precisely calculated .
If you reached 299,792,458 meters per second (just below light speed), traveling for two minutes at that velocity would equate to approximately six Earth days passing back home.
Frequently, this idea of distorted time is employed to elucidate the mechanics of traveling faster than light speed. "I'm quite a devoted admirer of Star Trek "Even though I don’t intend to criticize," states Kortemeyer. Nonetheless, the program’s science fiction concept of ‘warp speed’ presents an issue. escape faster than light travels It's purely fictional with no scientific basis, according to him. "Bending space is indeed a real concept," however, there isn't currently a method to induce or regulate the distortion of space for altering velocity. He states, "The idea of having a warp drive doesn't align with our understanding of physics. I can't identify which law of physics could facilitate something like that."
And to bring things back to reality even further, reaching 299,782,450 meters per second represents an immense challenge on its own. The primary hurdle when dealing with such high velocities isn't maintaining a steady pace, but rather achieving acceleration. We're already traveling much quicker than one might think; everything on our planet moves around the Sun at approximately 67,000 miles per hour. However, since this speed remains consistent, we do not perceive it. Reaching the speed of light from Earth’s perspective would tell quite another tale though. "It's impossible to simply accelerate up to the speed of light. You'd get compressed," explains Kortemeyer.
The acceleration required to reach near-light speed would result in immense g-forces, unless done with extreme care. Human bodies are designed to handle 1g, which is the gravitational pull we experience on Earth. Typically, individuals can endure 4-6g over brief intervals lasting several seconds to minutes without issue. However, sustaining these levels of g-force for extended durations or under greater intensities could pose significant challenges. becomes fatal As our body’s internal fluid dynamics become obstructed.
According to Kortemeyer’s computations, it would require approximately one year for someone to reach light speed at an acceleration force kept below 3 g. However, as he points out, the effects of prolonged exposure to such forces remain uncertain. Continuous acceleration surpassing our physiological design for up to twelve months could potentially challenge both the boundaries of physics and human endurance.
This tale is part of Popular Science’s Ask Us Anything series , where we tackle your wildest, thought-provoking questions ranging from the commonplace to the bizarre. Got a question you've always been curious about? Ask us .
