Interstellar travel: the technology we need to travel long distances


Space is really, really big, and aliens are not magic. In my previous article, I presented these two points as being critical for anyone inclined to believe that UFOs are spaceships from a distant star system. (I’m not that inclined.) These are also the most important points to consider if you want humanity to come out of the solar system. (I do.)

Last week we covered the first point on the distances between the stars. This week we take a look at the second point, which requires us to deal with the physical problems associated with crossing these vast distances even though we do not yet know what their solution might be.

Solutions to the problems of interstellar travel

Given the insane scale of interstellar distances, how could we extrapolate from the physics we understand to envision the possible ways in which aliens (or us in the future) might cross the cosmic void? There are a few possible solutions to the problem of interstellar travel.

Cryo-sleep. Based on their biology, the lifespans of our hypothetical aliens could be shorter than the centuries-long journey required for slow, slower-than-light travel between the stars. This is certainly the case for us. One obvious answer to this dilemma is to do the winter bear thing and hibernate throughout the trip. Cryosleep technology would essentially “freeze” the body’s metabolism (or at least slow it down) for the duration of the trip. While this is a staple of science fiction, no one has even managed to make it work for higher animals (like mammals). Still, it’s the kind of solution that doesn’t require the existence of some new magical physics – maybe just new magical biology. Also, if “post-biological” life is really a thing, then maybe some aliens are shifting to silicon-based machine forms, and so the issue of long timescales is no longer an issue.

Light sails. While no one has ever been swept off the street by a ray of sunlight, photons (light particles) exert a force – a push – on matter. If you could spread a sheet of material large enough and light enough in space, you could use the sun to propel you into space. The idea of ​​such solar sails has been around for a long time, but in 2016 Philip Lubin of UC-Santa Barbara proposed using giant, very powerful lasers, rather than the Sun, to provide light for interstellar navigation. With a sufficiently large laser positioned at the starting point, you could speed up a sail and the ship attached to it to almost the speed of light. This means that you could cross the distance between nearby stars in years or decades, not centuries or millennia (or more).

Billionaire astronomer philanthropist Yuri Milner was so won over by the idea that he spent $ 100 million on its development through a project called Revolutionary Starshot. The problem for UFOs using this technology is that you need another giant laser located in the target star system to slow you down if you wanted to stop for a visit.

Wormholes. If the speed of light limits the speed at which you can travel through space, then the best solution for interstellar travel may be to give up the “through”. This possibility was the gift that Einstein gave us with his theory of general relativity (GR). In relativity, space is not a vacuum. Merged over time into a single entity called space-time, it forms a flexible fabric that can be bent, stretched, and folded. Wormholes represent a kind of space-time tunnel that uses this folding to join two regions of the galaxy that only appear to be widely separated.

While such wormholes (aka Einstein-Rosen bridges) are definitely allowed in GR, they are unstable. This means that once formed (by whatever means, natural or otherwise), they would close almost instantly. So if aliens are going to use wormholes to build some sort of galactic transit system, they should find something physicists call “alien matter.” It’s something that has real anti-gravity properties. This could force the two “mouths” of a wormhole to remain open, thus connecting two distant parts of the galaxy. The big problem here is that the exotic material isn’t real. It’s just a term you can add to GR equations and change their behavior. But it is there, within the framework of known physics. If the exotic matter turns out to be more than a physicist’s chimera, it could serve as a medium for rapid interstellar travel.

Distortion drives (aka, hyperdrives). Ah, warp drives, the darling of sci-fi writers everywhere. If aliens could build warp drive, they would again use Einstein’s GR idea of ​​“space fabric”. The reader is not pushing you through space from one place in the galaxy to another. Instead, it creates a “chain bubble” that stretches and then relaxes the space-time around you. You do not travel in space faster than light; instead, you warp and warp space faster than the speed of light. This is the app’s killer flaw in GR: while nothing can travel faster than the speed of light in space, space-time itself can move at the speed it can. wants.

The good thing about warp bubbles is that they, like wormholes, are also theoretically possible, as Miguel Alcubierre showed in a famous 1994 article. The concept “Alcubierre drive” did the subject of considerable attention since then and can be extended in several ways. But there are, as you might expect, some really big issues with warp drives (or we would already have them). Again, you need this exotic material that probably doesn’t exist. What’s even more problematic is that the warp bubbles can generate huge “shock waves” of high-energy gamma rays as they move. Once you ditch the Warp, this burst of energy would scorch everything in your path and sterilize any planet you visited. If so, let’s hope the aliens equipped with an Alcubierre reader don’t show up for brunch anytime soon.

Quantum mechanics. Quantum physics, which is our ultra-powerful theory of the atomic and subatomic world, is notoriously strange. With quantum mechanics, physicists are forced to talk about particles in two places at the same time or two particles affecting each other instantly, even if they are on either side of the Universe. I could go on for a moment on the strangeness of quantum mechanics in relation to our “common sense” understanding of how space, time, matter and energy are. Assumed to behave. Even after 100 years of developing quantum mechanics into the most precise and powerful physical theory ever created – and having become the foundation upon which all of our electronic miracles are built – we always cannot say that we understand what it tells us about the nature of reality.

Personally, I think it’s pretty cool. What all of this means for interstellar travel is that there might be something hidden in quantum mechanics that allows you to bypass GR’s apparent restrictions on space-time. Some people who work on the fusion of quantum mechanics and GR in a theory of quantum gravity even believe that space-time is perhaps not fundamental. Instead, it could emerge from a deeper aspect of reality. Thus, quantum mechanics could have a few tricks up its sleeve that a sufficiently advanced alien species could know and exploit for interstellar travel. But be careful. There is no physics here other than noting a certain quirk.

All aboard the Interstellar Express?

So that’s it. That’s all we (or “they”) have in terms of solutions to the problems posed by interstellar travel. Now a good sci-fi writer might find other creative ways to imagine moving from star to star. The above list, however, pretty much exhausts what a scientist would suggest to be possible based on what we know from reality (which is a lot). The important thing to note is that once you get past the first two possibilities, then Elvis, in terms of experimentally validated physics, has definitely left the building.


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