Most people would naturally agree that space (outer space, the black, the void between worlds, whatever you call it) is pretty dang cool. (Physics pun, of course, since the "emptiness" of space is pretty much as "cool" as it gets)
But seriously, there is some neat stuff out there beyond our atmosphere. There are earth-like planets to be explored, (and I highly recommend checking out that wikipedia link), nebulae and supernovae and new stars and the frickin hexagon on Saturn, planets and planetoids in our own solar system, etc etc.
So
Much
Cool
Stuff.
I actually just watched The Europa Report yesterday, and while it wasn't exactly the sci-fi romp I was hoping for, it was actually really good. Basically a team is sent to Europa, one of the moons of Jupiter, and the most likely candidate in the solar system (except for Earth, of course) to have evidence of extraterrestrial life. Europa is covered in ice and possibly liquid water, which makes it really interesting. I'm not going to go into details of the film, of course, but it was a fun look at what an expedition to Europa might be like, using more or less current technology.
And that brings me to my point: current technology. Humanity has done some pretty impressive things, of course. We sent men to the moon using less computing power than most teenagers carry around in their pockets. Obviously most teenagers wouldn't know how to even start using their smartphones to control an Apollo rocket, but that's besides the point. We've sent a probe out beyond what is generally accepted to be the border between our solar system and interstellar space. Took us 35 years to get there, but we made some stops on the way, ok? We also have astronauts living in a space station 230 miles above the surface of the earth, and a fleet of satellites surrounding our little planet that do everything from give us internet to tell us where we are. We live in a really cool age. We can do some REALLY cool things.
But the problem is Space. We're hesitant about sending people to Mars, much less Europa, and much MUCH less Tau Ceti E, and with good reason. To quote the good doctor "Space is disease and danger wrapped in darkness and silence." Outside of the protective region afforded to us by our home planet, space is a dangerous and lonely place. Similar to the explorers of old, setting off into space means abandoning all thought of help or rescue from home. However, to make it more difficult, space explorers can't catch space fish for food, or evaporate sea water for drinking water, or even find a convenient island to restock the supplies. The vehicles we make that seem so mighty, so powerful, here on earth, are egg-like in their fragility in space. One little speck of space dust, the size of a grain of sand, can punch through the hull of a spacecraft like a needle through a bubble, with similar results. A solar flare kicks up and shoots high-energy particles through the radiation shielding, cooking the crew. Even mechanical failures that would be minor in an Earth-going vessel can prove catastrophic in the vastness of space.
Additionally, ships in space can't rely on natural forces like wind and tide for propulsion. Yes, we are working on things like solar sails to harness thrust from photons from the sun or laser arrays on earth, but those things will barely provide enough thrust for tiny sensor packages. We're not anywhere close to seeing solar sails being implemented on a manned vessel. This means that, with current technology, we're limited to vehicles that can carry their own fuel with them. For rocket-type vehicles, this generally means doing one large burn to get going and another to slow down once the destination is reached. With some new types of thruster technology, such as ion thrusters, the force per unit of fuel is much higher, and the engine can be run for longer, achieving much higher speeds, though at very low acceleration. Now, when I say higher speeds, I mean compared to chemical rockets. According to NASA, chemical rockets can achieve speeds of around 8.05 km/s, where the ion-powered rockets could get up to 90 km/s, or over 10 times faster. This sounds pretty fantastic, until you actually get a sense of scale. The distance from the Earth to the Sun, known as an Astronomical Unit, or AU, is approximately 150,000,000 km. This means that our ion rocket would take 20 days to travel 1 AU, and that's if it's at top speed the entire time. In reality, the amount of time it takes to speed up and slow down an ion-powered rocket would make that trip on the order of months.
There are more esoteric concepts being explored, such as nuclear pulse propulsion, which, in a nutshell, involves detonating smallish nuclear devices behind the ship and using a shielded plate to catch the shockwave and ride it off towards the stars, or matter-antimatter reactions, which is limited by the difficulty of generating antimatter. These methods could produce conservatively estimated speeds of up to 50,000 km/s, or nearly 1/4 the speed of light. Compared to the 90 km/s from an ion engine or the 8 km/s of a chemical rocket, that's a pretty big increase.
But it's not enough.
To get a bit more perspective, the solar system is around 40 AU in diameter, if we assume that the outermost orbit of Uranus is the end of the solar system. If we go to the edge of the heliosphere, which is the more commonly accepted definition of "edge of the solar system", we're talking about 180 AU, or, if you're too lazy to do the math, about 89 AU from earth to the edge of the solar system. The problem is that getting to the edge of the solar system isn't really our goal. Let's say we wanted to go to the nearest possibly inhabitable planet, Tau Ceti E. Tau Ceti E is almost 12 LIGHT YEARS from Earth, or almost 760,000 AU. Assuming that our little ion rocket is going its absolute fastest, it'll still take around 400 CENTURIES to travel that distance. Yes, that's right. 40,000 years, or 1000 times longer than Moses and the Israelites wandered the desert. A nuclear pulse ship would take about 180 years to make the trip, and an antimatter rocket ship would still need around 50 years, and that's not including the time it'll take to speed up and slow down.
IF, and that's a big if, we could outfit a ship with a crew that could actually survive a journey of 40,000 years or 180, or even 50 years, it's extremely probable that before the mission reached the half-way point we'd have new technology that would allow us to go pick them up and take them the rest of the way in much less time. This principle is featured in the wait calculation, which basically states that there is a threshold for sending manned missions to interstellar targets based on the idea that people who leave later would have the technology to get there sooner.
So what do we do? Even at speeds approaching 1/4 to 1/2 the speed of light, we're looking at really long times to get anywhere interesting. We've proved time and again that there is the big cosmic speed limit, just like Einstein said. If we could get a ship up to around 99% of the speed of light the crew wouldn't experience a very long trip, due to time dilation effects, but getting up to that sort of velocity is incredibly difficult. As the velocity of a vehicle increases, so does its mass, meaning that it takes more and more force to achieve higher and higher speeds. More force=more fuel=more mass, generally, so that's kind of a circular problem.
But what if we could get around that speed limit? What if there was a way for us to travel faster than the speed of light without breaking the laws of the universe? Faster-than-light common trope of science fiction, mostly because no one wants to watch a show where it takes 50 years to get anywhere and by the time they do the characters you care about are old or dead, but what if it were possible?
Enter Miguel Alcubierre, a theoretical physicist who came up with what's now known as the Alcubierre Drive. The Alcubierre drive is a method of stretching and squeezing space-time to move an object. We already know that space-time is expanding, and in some places that expansion is happening faster than the speed of light. Alcubierre postulated that by expanding and contracting space-time in a region localized around a ship, the ship could be moved at speeds faster than light without violating any laws of physics.
Basically the ship would be enclosed in a bubble of space-time and the bubble would move faster than we can achieve with current technology.
Of course, there are a series of catches. First and foremost, the math requires the existence of matter with negative density, normally called exotic matter, which is something that is postulated in several separate theories, but hasn't been confirmed to exist.
Second, there's the actual amount of exotic matter required. In some calculations it was shown that in order to move a ship across the galaxy you would need around 10^64 kg of exotic matter, which is several orders of magnitude greater than the estimated mass of the entire universe. Not exactly practical. However, several scientists have reworked the calculations by considering a thinner bubble shell and a different shape. Notably among these scientists is Harold White, a NASA scientist who is actively working on the warp drive problem. His calculations showed that an average-sized spaceship would only require around 700 kg of exotic matter for the Alcubierre Drive to function. That's obviously a significant difference, which brings us from the realm of "neat but impossible" to "this might actually work."
Harold White is important because, as mentioned, he's actually working on this idea. His department at NASA has an experiment they're performing to test whether or not space can actually be warped as postulated. It's been shown that gravity bends beams of light, but whether or not space itself can be warped by man-generated effects is still unproven. The initial results of the experiment were inconclusive, but the scale on which the experiment is being run is so small that vibrations from the Earth and the surrounding environment can affect the results.
Regardless, the fact that we even think that something like a Star Trek Warp Drive is possible and that there are people out there actively working towards making this sort of thing a reality is incredible.
And this brings me to the "why is this important" part of the post. I'm not going to spout nonsense about overpopulation and us needing to find a new home or building colonies or anything. I'm all for expanding humanity to other planets. I think that's an awesome idea. But I can't sell overpopulation and dwindling resources as a reason why we HAVE to do it. I think we all know that if we managed our resources (including space on earth) a little better, we'd be just fine.
No, I believe that space exploration is important because, deep down, the vast majority of humanity has a curiosity that needs to be sated. We need to know what's out there. We need to find new things, see new sights, experience new places. Obviously any individual person can spend their whole life on earth and never run out of new things to see or do, but humanity as a whole has nearly exhausted all the "new" our little planet has to offer. There's an entire universe out there, and I'd like to see it.
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