Propelling a 10-ton spacecraft to 99% of the speed of light would require more than 200 times the energy consumed by the entire planet in a year.
The idea of zipping through the universe at lightspeed has fueled countless science fiction stories. Yet, as exciting as it sounds, traveling at or near the speed of light—around 300,000 kilometers per second—is far beyond the realm of current science, explains Popular Mechanics. For one, the laws of physics declare it impossible for anything with mass to reach this speed. “It’s the speed at which massless particles, like photons, travel,” explains Dr. Gerd Kortemeyer, associate professor emeritus of physics at Michigan State University. “For objects with mass, it’s simply not possible.”
Even reaching speeds close to this cosmic limit presents challenges that go far beyond energy consumption. The effects on the human body and the distortions in time and space are concepts that stretch our imagination—and our understanding of reality.
One of the most significant barriers to near-lightspeed travel is energy. Propelling a 10-ton spacecraft to 99% of the speed of light would require more than 200 times the energy consumed by the entire planet in a year. And that’s assuming a perfectly efficient fuel source—something that doesn’t exist. “Even if we had a fuel that converted mass into energy without waste, it still wouldn’t be feasible,” says Dr. Kortemeyer.
While we can accelerate individual atomic particles to near-lightspeed in laboratories like the Large Hadron Collider, doing the same for a spacecraft—or a human—remains a distant dream.
What Would Happen at Near-Lightspeed?
Let’s imagine, for a moment, that we overcome the energy hurdles. What would it feel like to travel at near-lightspeed? The experience would be nothing short of mind-bending.
Colors Would Shift and Light Would Intensify
Traveling near lightspeed would drastically alter your perception of the world, reveals Popular Mechanics. The Doppler effect, which changes how sound or light waves are perceived, would make objects ahead of you appear bluer, while those behind you would appear redder. This visual distortion is similar to how a speeding ambulance sounds different as it approaches and passes.
Another bizarre effect would be the brightness of objects. As you move closer to lightspeed, more photons—particles of light—would hit your eyes at once, amplifying the light’s intensity. “It’s like running through a rainstorm,” Dr. Kortemeyer explains. “The faster you go, the more raindrops hit you, soaking you faster.”
Time Would Warp
One of the most fascinating effects of near-lightspeed travel is time dilation, a phenomenon predicted by Einstein’s theory of special relativity. Time would slow down for the traveler compared to those remaining stationary. For example, if you traveled at near-lightspeed for just two minutes, several days might pass on Earth. This concept, often illustrated by the “twin paradox,” is not just theoretical—it’s a proven aspect of our universe.
The Physical Toll on the Human Body
Even if we solve the technological and energy issues, the human body will face immense challenges during near-lightspeed travel. Accelerating too quickly would create dangerous g-forces, the forces exerted on the body during rapid acceleration. Most humans can only tolerate short bursts of 4-6 g before losing consciousness. Prolonged exposure, even at 3 g, could cause fatal complications, as our bodies are not designed to handle such forces over extended periods.
To safely accelerate to near-lightspeed, reaching the necessary velocity would take at least a year without exceeding safe g-forces. However, scientists are unsure how long-term exposure to even low levels of acceleration might affect the body.
Science fiction often imagines ways to sidestep these limitations, such as the iconic “warp drive” from Star Trek. However Dr. Kortemeyer points out that these concepts are purely fictional. “Warping space itself is a physical reality,” he says, “but we have no way to control it to achieve faster-than-light travel.”
For now, lightspeed remains the ultimate boundary of our universe. While it may spark dreams of interstellar exploration, it also serves as a reminder of the incredible mysteries still waiting to be unraveled.
