In science fiction narratives, spacecraft capable of reaching or surpassing the speed of light open up endless possibilities for exploring the universe. However, within our earthly confines, achieving such velocity—specifically, traveling at 299,792,458 meters per second or approximately 670,616,629 miles per hour through space—is physically unattainable with current technology. "The speed of light is only attainable by objects without mass," explains Gerd […]
In science fiction, spacecraft capable of reaching or surpassing the speed of light allow for extensive journeys across the universe. However, in our earthly world, 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 a physical impossibility “It’s how quickly thing without mass move,” he states. Gerd Kortemeyer , an associate professor emeritus of physics at Michigan State University. Therefore, any object with mass can never 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," explains Kortemeyer.
Twice as unlucky for those of us who are keen to explore distant galaxies—even traveling at near Traveling close to the speed of light compared to our regular old Earth is not an option. "It's both unachievable and extremely dangerous," according to the physicist.
Apart from complex theoretical explanations, using enough fuel and energy to accelerate any crewed spaceship to such high speeds would be impractical. According to Kortemeyer’s computations, a vehicle with a mass of 10 metric tons (considerably light and compact) would require an enormous amount of resources just to attain 99% of the speed of light. than most spacecraft ), while accelerating at a manageable g-force would require over 200 times the annual global energy consumption on Earth. This assumes an ideal fuel with perfect efficiency, converting mass into propulsion without any heat loss—a scenario that defies known physics. second law of thermodynamics .
The nearest we've gotten to light speed is propelling minuscule individual atoms to incredibly high velocities. approximately 99.99999896 percent the speed of light at the Large Hadron Collider.
However, let's set aside everything else and consider for a brief moment what it might be like if we could approach the speed of light. Assuming we possessed an ideal, highly efficient power supply with ample reserves, along with a spacecraft built to endure such speeds and the determination—what sort of experience would near-light-speed travel offer us?
Surely enough, things took an unusual 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 a velocity, it is also "one of the basic constants of nature," as explained by Kortemeyer. Since the 1600s, astronomical observations of planetary motions have been made. suggested the velocity of light And in 1865, James Clerk Maxwell inferred that light is an electromagnetic wave and determined its velocity, which closely matched the currently accepted value. 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 idea of spacetime as an integrated cosmic sheet, linked through the constant "c," which outlines the connection between energy and mass. When he computed this value, coincidentally, it aligned perfectly with expectations. 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 than stationary ones. On typical earthly velocities, these differences go unnoticed. However, approaching the speed of light makes this discrepancy evident through what is called time dilation (this concept will be revisited later).
Moreover, due to the distinctive connection between lightspeed and spacetime, this velocity stays consistent regardless of the observer's speed. Think about being inside a vehicle on a freeway for a second. Should you travel at a steady pace of 30 miles per hour and another car ahead zips past you going 60 miles per hour, that quicker car moves away from you at 30 mph compared to your own speed. Nonetheless, if you tried to chase down a photon reaching half the speed of light, that photon would continue receding from you at exactly the speed of light itself. "The speed of light is perpetually unchanged irrespective of one's motion—a trait not shared by anything else," explains Kortemeyer.
Combined, these ideas result in encountering near-light speed being an exhilarating journey.
How might traveling at speeds close to light feel?
Hues and luminosity would appear altered and significantly distinct, as demonstrated in this 2012 simulation developed by Kortemeyer and collaborators at MIT. The simple game is meant to illustrate the relativistic effects of moving near light speed and is premised around a universe where light moves much more slowly, and constantly slows as you navigate the world. In that universe, though one still wouldn’t be able to reach or exceed lightspeed, you would be able to approach it at a brisk walking pace.
As you did, you’d experience a visual doppler effect–similar to how an ambulance speeding by with its siren blazing seems to change its tune as it moves. Moving towards an object would make it appear bluer, as its wavelength visually shortens. Moving away from an object would do the opposite, shifting its appearance redder.
Approaching something rapidly enhances how vividly you perceive it due to what’s known as the spotlight effect. According to Kortemeyer, this can be likened to sprinting through heavy rainfall. When moving swiftly through such conditions, most of the raindrops impact your body from the front, causing your clothing to become drenched faster. Similarly, within the virtual environment of the game, these metaphorical "raindrops" represent photons. So when traversing a shaft of light nearly at the speed of light, an increased number of light particles would strike your eyes simultaneously.
If that isn’t bizarre enough, think about how this might affect our perception of time. Recall the theory of time dilation? Due to the curvature of spacetime required to maintain the speed of light as a constant, someone journeying through space close to the speed of light would experience aging at a much slower rate compared to those remaining stationary on Earth. The phenomenon is highlighted by twin paradox Thought experiment. The effect of time dilation, along with the difference between time at rest versus time experienced 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 notion of distorted time is employed to elucidate the mechanics of traveling faster than light. "I'm quite a devoted admirer of Star Trek "I don't want to criticize," states Kortemeyer. Nonetheless, the program’s science fiction concept of "warp speed" presents escape faster than light travels It's purely fictional with no scientific basis, he states. "The distortion of space is indeed physically real," however, there is currently no method to induce or regulate the bending of space to alter velocity. "In the realm of physics, a warp drive does not exist. I can't fathom which law of physics could enable something like that," he explains.
And to bring things back to reality even further, reaching 299,782,450 meters per second presents a challenge all by itself. The primary obstacle when dealing with such high velocities isn't maintaining a steady pace, but rather achieving the 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 relative to Earth would tell quite another tale though. "You cannot simply accelerate up to the speed of light. It would flatten you," 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 endure 1 g, which is equivalent to Earth’s gravity. Typically, individuals can cope with 4-6 g over brief intervals lasting several seconds to minutes. However, sustaining this level of g-force for extended durations or under greater intensities could be problematic. becomes fatal As our body’s internal fluid movements become obstructed.
According to Kortemeyer’s computations, it would require approximately one year 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. It could be that continuously experiencing this level of acceleration force over 12 months might challenge both the boundaries of physics and human physiological endurance.
This tale is part of Popular Science’s Ask Us Anything series , where we answer your most outlandish, mind-burning questions, from the ordinary to the off-the-wall. Got a question you've always been curious about? Ask us .
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