Traveling to distant stars will require a lot more than conventional rockets, and warp drives could break the universe's speed limit.
Space may be the final frontier, but humanity will need lots of new technology – and perhaps all new fields of science – before we can start exploring its depths. As of right now, the only proven method of traversing outer space is with more powerful rockets. While that might be marginally acceptable for manned flights within our solar system, it would still require astronauts to be crammed into a tiny spacecraft for years at a time before reaching a destination that’s inhospitable to human life.
To put things into perspective, it takes a mere three days to reach the moon, which is 240,000 miles (386,400 kilometers) away. But things become more complicated the further you head out. A two-way trip to Mars (which is millions of miles away) could take three years or more with our current technology, depending on the planet’s position in relation to Earth when the ship launches. But our nearest neighboring star system Alpha Centauri is roughly 4.3 light years away. It would take years to get there traveling at the speed of light; decades at more conventional speeds.
So, it’s clear that if humans want to adventure through space like in sci-fi, we’re going to need ships that go much faster, preferably as close to the speed of light as possible. Even then, we’d need to either consider a generational ship with a completely enclosed self-sustaining environment, or develop deep stasis technology like in the classic movie Alien for manned trips to distant stars. Otherwise, scientists will need to figure out a way to go faster than the speed of light.
To do that, scientists must imagine ways to achieve the impossible, and that’s where sci-fi often comes into play. Although shows, movies, and video games usually rely on completely made-up technology for the sake of storytelling convenience – with Star Wars, Star Trek, and Mass Effect being a few major examples – some ideas could lead to real-world breakthroughs.
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The Light Speed Limit
The good news is that our current understanding of physics suggests that it is possible for an object to travel faster than the speed of light. However, there’s a long list of challenges, with the first being the energy needed to reach this speed.
We already know through Einstein’s equation (E=mc^2) that energy and mass are proportional to each other. Meaning that the faster something goes the more energy it will need as the object’s mass increases. Ultimately, reaching the speed of light would require infinite energy.
But that’s just the start. Even if we set aside basic considerations such as fuel and life support, we would need a way to accelerate the ship without crushing the crew. According to The Science of Star Trek, it would take about 2.5 months to safely accelerate a crew of humans to half the speed of light (150,000 km/sec), which is fine for patient astronauts who don’t want to be flattened, but it wouldn’t make for a quick tour of the solar system.
Then there’s the time dilation effect illustrated in movies like Interstellar. The crew inside of a spaceship traveling at near the speed of light will experience time differently than people on Earth. What may seem like a short time on the ship could be days, years, or decades on Earth. So, achieving light speed through conventional acceleration seems impractical unless you have a crew that’s willing to leave everything they know and love behind to return to a much older Earth. That future civilization might have even figured out how to overcome the time dilation problem, making the astronauts’ sacrifice worthless.
So, there clearly needs to be a better way to get around in outer space.
Taking it to Warp Speed
Of the various forms of sci-fi space travel, Star Trek’s warp technology is among the most plausible. The theoretical method of travel involves contracting the space in front of the ship while expanding the space behind it to travel at high speeds. The ship might look like it’s traveling faster than the speed of light to an outside observer, but the ship isn’t actually moving at all. It’s just inside a bubble of spacetime that’s riding a wave while a deflector dish would be used to prevent particles from colliding with the ship.
With warp technology, the problems of lightspeed travel may be overcome, including g-forces and time dilation. However, they’re replaced with a whole new set of problems. Manipulating space in such a way will require an immense amount of exotic matter called negative energy. It’s the opposite of the energy that we know, and it could bend the universe in the opposite direction. But even though scientists have indirectly observed trace amounts of negative energy, it would require more than all the positive energy in the visible universe to create a warp bubble around a small ship.
Physicists such as Dr. Richard Obousy believe that dark energy, which accelerates the expansion of the universe, could be a substitute for negative energy. In that case, we would need the mass energy contained in Jupiter to create a warp bubble, which is a substantial upgrade from all the energy in the universe. But before anyone can even consider generating dark energy, even in tiny amounts, scientists first need to figure out what the stuff is.
Warp travel could also have significant downsides, especially since no one knows what the consequences of manipulating space are. There’s no guarantee that a crew could survive inside the bubble. Particles could build up during travel, then shoot forward when the ship stops with enough power to destroy a planet. Or the ship might not be able to stop at all. Being stuck inside of a bubble surrounded by warped space could prevent a stop signal from transmitting.
Suddenly, rockets don’t sound so bad...
The Physics of Star Trek by Lawrence M. Krauss