Five Bizarre Plans for Interstellar Travel by Theoretical Physics

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Five Bizarre Plans for Interstellar Travel by Theoretical Physics

Regular space travel is complicated enough. And the Cold War-era suggestions for how mankind might one day achieve interstellar travel — flights by manned or unmanned spacecraft to other stars — ranged from the merely unlikely to the wildly implausible. Still, even the most optimistic of those, like microwave-powered sailing spaceships and antimatter-powered space trains, pales compared to some of the wilder schemes cooked up by theoretical physicists.

Science fiction literature and movies have already played out most of the more easily conceivable strategies, like developing some sort of “suspended hibernation,” “stasis” chamber, or cryogenic freezing through which passengers could blissfully sleep away the longer years of a journey to another star system. If manned passengers are going along for the ride (and this is a possibility that is increasingly ruled out), of course, such technology would be necessary because of the vast distances involved. Our three fastest spacecraft to date — the Voyager probes and the New Horizons probe to Pluto — would take 70 000 years to reach just the closest stars to us, the three stars in the Centauri system (Alpha, Beta, and Proxima).

Of course, those approaches are based on high speeds that human technology might one day achieve, but none of them are anywhere close to the speed of light, which itself takes four years to traverse the distance between Sol and Centauri. So, naturally, theoretical physicists have stepped forward to fill the gap with the most extraordinary of speculative ventures. (This is what theoretical physicists do, after all.)

1. A “Dark Matter” Spaceship

This is the most recent and currently the most speculative proposal for spacecraft propulsion. In two separate 2009 papers, American physicists and mathematicians Jia Liu, Louis Crane and Shawn Westmoreland suggested that the spacecraft of the future could be propelled by two of the most speculative objects in all of speculative physics, dark matter and black holes. According to present theoretical science, these authors insist, there is no reason not to believe such ships could be built. The only question (and it is a big question) is how.

Liu’s dark matter starship would make use of a form of matter which physicists and astronomers insist must exist, but which cannot be seen by human beings and has not yet been fully confirmed through experimentation. Instead, dark matter is more of a placeholder: vast areas of space seem to act as though they weigh far more than they do, and so physicists build this into their calculations by referring to the mysterious substance of “dark matter.” Once we manage to figure out what dark matter is and where to find it, Liu said, we’ll almost certainly be able to use it as an energy source. And since (according to physics) there’s likely so much of it, the dark matter spaceship will be able to refuel as it goes.

Of course, we’ll have to find the dark matter first. And then figure out how to get to it. And finally, how to use it.

2. A “Black Hole” Spaceship

In the meantime, Craning and Westmoreland claim that Liu’s idea is unrealistic, and offer one of their own. The famous British scientist Stephen Hawking, who devoted much of his life to the study of black holes, has proven that, contrary to popular (and scientific) imagination, they don’t just suck in everything around them: very, very slowly, they “evaporate” by letting off what scientists now call Hawking radiation.

To Crane, that radiation is an energy source just waiting to be used. (And there is some precedent for using radiation as a power source: the Voyager probes of the 1970s used special electrical power generators that operated by radioactive decay.) We will need to find a black hole first, according to Crane – but perhaps we could make one through what he admits would be “a huge, industrial effort”: using a 250-kilometre-wide solar panel to power a giant laser which would fire and create a very small black hole, which would then somehow be tethered to a spaceship and used to pull it along.

We haven’t yet found any solid candidates for black holes — certainly none anywhere near the Earth — and it would be pretty tough to put the solar panel array and giant laser into space, where we’d be a little safer if anything went wrong. (What would happen to the people on the black hole starship if anything went wrong is another question.) Liu and Crane say it’s possible, though, and that it’s even possible that we see so few aliens in this part of the galaxy because the amount of dark matter and black holes in this region aren’t high enough to make refuelling possible.

The simpler explanation, of course, is that there are no aliens cruising anywhere in such starships.

3. Warp Drive (Of Course)

Not the usual Star Trek version, mind you. In the 1990s, a Mexican physicist named Miguel Alcubierre theorized that it would be possible to build a “warp drive” by the rather abstract method of “stretching space in a wave which would… cause the fabric of space ahead of a spacecraft to contract and the space behind it to expand.” Effectively, Alcubierre was proposing surfing on a wave made up of the theoretical fabric of time and space. As long as the ship remained within this wave or “bubble,” it would effectively be able to bypass normal physical laws and accelerate to unbelievably high speeds.

So far, no one has actually found a “warp bubble.” More to the point, if one could be found (or manufactured), Alcubierre is not able to suggest how to get a spaceship into it — or, more to the point for those travelling inside the spacecraft, how to get out of it once it’s taken you as far as you want to go.

4. Let the Probe (Re-)build Itself

The most obvious problem, once you account for carrying enough fuel and guaranteeing enough patience to wait for results here on Earth, is that NASA’s recent history has taught us that human probes generally can’t even reach Mars without suffering at least some sort of potentially serious software glitch or mechanical breakdown. Travelling several light-years to another (uninhabited) star system makes for a long trip between pit stops.

The solution, according to some, is simply to let the spacecraft build themselves. Technically, these are referred to as “self-replicating spacecraft.” In its most basic form, put forward by Hungarian-American mathematician John von Neumann, is a spacecraft with three basic functions: to travel, to transmit information back to Earth, and, essentially, to reproduce. Von Neumann’s so-called “Universal Assemblers” would arrive at a resource-rich staging area, such as an isolated moon, and then build robotic factories to turn out new copies of themselves. Those new machines would then travel to other star systems, and repeat the process.

Occasionally, one of these probes would come across something interesting, and it would be programmed to then stop and monitor the event. Alternatively (which raises some concerns), they could be programmed to take a more active approach. They might, for example, begin manufacturing genetically identical copies of us on suitable worlds (Stargate SG-1 portrayed just such an alien seeder ship in the episode “Scorched Earth.”) Novelist Fred Saberhagen has envisioned an even more disturbing future in which humans are discovered by alien, von Neumann-style probes which have been programmed to find and destroy inhabited worlds. Fortunately, such fantasies seem unlikely, to say the least.

5. Make the Probe Alive

Even if we don’t make our probes “self-replicating,” they’ll still have to take care of themselves. In 1960, electrical engineer Ronald N. Bracewell pointed out in a paper that in the unlikely event a long-distance human probe ever finds an alien civilization, it will have to make first contact without referring to us here on Earth. In that case, he said, the probe would have to be given an advanced Artificial Intelligence in order to represent us properly. The result is what is now known as a “Bracewell probe.” The monoliths in the movies 2001 and 2010 are examples of Bracewell probes.

It will be a long time before humans can create a computer with actual artificial intelligence, let alone one that travels through space looking for alien races. But the same people who are interested in the Search for Extra-Terrestrial Intelligence are naturally interested in looking for Bracewell probes from other races, hiding out in our solar system. Some even claim to have found one in an apparent asteroid that orbits near Earth in a very irregular pattern, 1991 VG, although it seems more likely simply to have been material blown off the moon by a meteor impact.

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My fiance and I will be traveling to Disney World in about 2 weeks. I’m really concerned becuase I saw on the news that some of florida is starting to smell like oil. I get very bad migranes (mell sensitive) and I dont want the trip to be ruined.

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Answer by Drewbenski
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