Sorry dear friends. Based on everything we know now, you can never hit a button and pierce "hyperspace" or warp. Traveling faster than the speed of light is almost certainly impossible. According to scientists, the only way for you to visit other stars is by deep and long sleep. The idea of cryogenic sleep, cryosleep, has always been one of the markers of "hard" science fiction. Instead of tricking Einstein, films like Alien and authors like Alastair Reynolds show people going to bed and waking up months, years, or even centuries later in another part of the universe.
In general, the idea of being frozen for months or years has always been greeted with considerable skepticism. Like other ways to slow down metabolic functions so that a person wakes up after a thousand years and is as fresh as when he went to bed. This is a very serious departure from what we know about the hibernation of mammals on Earth. But after io9 editor Charlie Jane Anders talked to a bunch of scientists and science fiction writers, including Reynolds himself, he was convinced that cryosleep is the only hope we have for interstellar travel in one lifetime.
The dream of traveling faster than light
Cryoson is fraught with gigantic problems, which we have no idea how to solve, but we already know that traveling faster than light is completely impossible.
“Based on what we now know, traveling faster than light is either impossible or requires energy that we will not even discuss. Maintaining the brain for a long period of time is just very, very difficult,”says Terry Johnson, professor of biology at the University of California, Berkeley.
“We can't even come up with a physically consistent theory of how faster-than-light travel should work, let alone a technical implementation of it,” says Karl Schroeder, author of Lockstep, a novel about a futuristic civilization that uses cryosleep to travel. “Traveling faster than light in our Universe as we know it at the moment is absolutely fantastic, and not at all a“not yet developed technology”.
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Even a curious idea like the Alcubierre engine, the concept of a superluminal engine that NASA has been developing for many years, “needs an impossible substance with negative mass to work,” says Schroeder.
Wait … what about wormholes? After all, these are, in fact, tunnels from one part of space-time to another, allowing us to overcome unthinkable distances.
But wormholes may not be possible either, according to Dave Goldberg, a physicist at Drexel University. The laws of the universe may not allow wormholes to exist at all, at least not in the form in which we could use them.
"For example, for a wormhole to be stable, it needs exotic matter to keep it open," Goldberg says. "But exotic matter requires negative energy density." Scientists have never seen "exotic energy" like this in the real world, Goldberg says, "and yet they don't know any natural way to produce it."
And even if we could keep the wormhole open after discovery, there is no theory on how to create one to begin with. The very essence of wormholes is to create a hole in spacetime. There are certain theories that on the smallest scales - 1020 smaller than an atomic nucleus - space creates natural structures like wormholes, but we have no way of knowing for sure yet. To find out, we need a working theory of quantum gravity, which doesn't exist either. And even if we open up a microscopic wormhole, we have no idea how to inflate it to fit a spacecraft.
Of course, you cannot prove otherwise - so we cannot know for sure that traveling through wormholes is impossible. Scientists admit that the wormholes themselves may be physically possible, but at the moment they are practically impossible, since they require colossal amounts of energy and technical ingenuity. In addition, even if you somehow open it, you have to go a long way to the star at the destination in order to set up the second end there.
So unless we invent a magical way to travel faster than light or build a giant wormhole, it will take a very, very long time to get to other star systems. It will take 81,000 years to reach our nearest star, Proxima Centauri, using the methods we know, to 1,000 years at best. There are several potentially faster methods, but they represent a logistical nightmare.
The needs of the tardigrades
“Even if faster-than-light travel is possible, there will almost certainly be the only way to do it, and that way may not be subject to human technology,” says Schroeder. But in the meantime, we can sketch out a ton of different engineering solutions for cold sleep.
Schroeder is optimistic that we will figure out how to sleep for the long periods of time required for space travel, but he doesn't know exactly what it will look like. “There are many paths to long term hibernation. We already know that living things can recover safe and sound after very long periods of time.” For example, microscopic tardigrades can sleep for up to 30 years, and then wake up without any harm.
“We already have several models of hibernation in animals, so we know it's at least roughly possible,” says Reynolds, another novelist who is working hard on the concept of cryosleep. At the same time, he is convinced that “it will be difficult to apply them to people. But work is underway in this direction”.
Reynolds notes that NASA spends a lot of time exploring the possibility of using hibernation, or torpor. But at the moment, all research has focused more on forced sleep than Ripley-style cryosleep. For fishlessness and cancer - fish, so all research in this area will go to the piggy bank cryosleep.
“I think a state of hibernation might be possible, but the question remains whether it would be possible under hypothermic conditions or not,” says Marina Blanco, a Duke University scientist who studies hibernation in lemurs. "If anything, some lemurs hibernate even in hot weather."
Space explorers can be like retired footballers
“We're currently working on how to cool people down for one to three days,” says Kelly Drew, a professor at the Institute of Arctic Biology at the University of Alaska at Fairbanks who studies the mechanisms that allow Arctic ground squirrels to hibernate. “If we figure out how to do this, the next step is to cool people down for a few days, maybe a month. But for hundreds or thousands of years - we still have to work on this.
What is the difficulty, according to Drew? Figure out how to freeze and thaw a human body without causing massive damage. “Even a ground squirrel that chills to near freezing doesn't stay that way for more than three weeks,” she says. "Mammalian tissue cannot freeze without rupture of cells." Basically, when mammalian cells freeze, ice crystals form in the cells, causing damage to cell membranes.”
And even if you manage to overcome the effects of freezing and thawing without cellular damage - and this is a very big "if" - there are other problems.
“If you freeze a person for 100,000 years, they will suffer serious damage,” Johnson says. “Chemical processes are slow at low temperatures, but they do not stop entirely, and after enough time will wreak havoc. Entropy on the march. This march takes place slowly, step by step, at low temperatures. But in 100,000 years, this march will go far.
One of the most likely outcomes of long-term cryogenic freezing will be brain damage, Johnson said. "Most likely, we need to plan for extensive surgery to rehabilitate the damaged brain on the colonists." Otherwise, the space colonists will have problems similar to the problems of retired football players, and the entire planet may be full of people with some "cryonic encephalopathy".
Another option is to make human-like consciousness stronger, with artificial consciousness, or cybernetic, or look for another way to create "neural networks that outlive our own," Johnson says.
Schroeder offers several different ways to deal with cell and brain damage. We could genetically alter space travelers - for example, give humans cell walls like those found in plants. It would also be possible to introduce sugar into the cells as an “anti-freeze”, antifreeze. Or we could replace cells altogether, using nanotechnology or artificial organs. And you can download the consciousness of people and store it in digital form, and then unload it into new bodies upon arrival.
All in all, getting people to sleep for centuries will take a lot of problems, and how we don't know yet. But this is at least possible from the point of view of physics.