by Robert Metzger
Copyright © 1998 by Robert A. Metzger. First published in the Summer 1998 issue of the Bulletin of Science Fiction and Fantasy Writers of America.
Interstellar space travel. We dream about it. We write about it. Science fiction writers have come up with all manners of interstellar travel, ranging from multigenerational arks, to wormhole generating warp drives that can spit you across the galaxy in a blink of an eye. As wondrous and amazing as all these approaches may be, most suffer from a very fundamental problem.
Traveling for long distances, over long periods of time, can be a colossal pain in the butt. You can never pack all your stuff. You always forget something. Did you lock the door? Did you turn off the iron? You forgot to say good-bye to Aunt Mildred, who will be dead by some 12,000 years when you return due to relativistic effects. And then there is that library book you forgot to return.
What to do?
The answer should be obvious. Just take it all with you.
I’ve got a solution, one that I consider very practical. My method does not require any magic physics – the ability to go faster than the speed of light, or jump about the galaxy by way of Star Gates. No. I am going to use good old fashion basic rocket science. Metzger’s Rocket Science Law #1 says that momentum must be conserved (some of you with a historical fetish and knowledge of obscure ancient scientists might recognize this as Newton’s Third Law of Motion – for every action there is an equal and opposite reaction). If you throw something out of the back of your rocket ship with mass m1 at a velocity v1, then the momentum of this exhaust is just the product of these two components – m1v1. As a result, your rocket ship will be propelled in the opposite direction of the exhaust, and with the exact same momentum. This means that if your rocket ship weighs m2, then the velocity of your rocket will be v2 = m1v1/m2. It’s as simple as that. If the mass of what you threw out is the same as your rocket, then you will move at the same speed as the rocket fuel (but in the opposite direction). The heavier the rocket, the slower you go.
You now know everything you need to know about rocket science.
Now back to my discussion about taking it all with you.
Forget all this business about building really big spaceships, or hallowing out asteroids and strapping on big fusion engines. No. The ideal solution is to simply move the entire planet. If you want to travel the 4 light years to Alpha Centauri, then just move the Earth those 4 light years. That way you don’t have to pack your bags.
It all goes with you.
Now there is one little problem with this plan. We depend on the Sun to keep everything running on this planet. Without the Sun we’d all be popsicles by the time we moved Earth out past the orbit of Mars. Well, the answer to that problem is obvious. We’ll need to take the Sun with us.
What the heck, let’s just move the entire solar system.
And here is the really beautiful part of this plan. You don’t have to do a single thing to planet Earth. Unlike the case in which you try to move the Earth, you don’t have to drain the oceans to get enough hydrogen to run the big fusion reactors needed to move the planet (which would probably occupy all of Australia and a sizable chunk of Europe). If you move the Sun, the Earth, along with all the other planets, just come along for the ride by way of gravitational attraction.
So all we have to do is move the Sun.
First, we need some sort of engine, something to heat up our fuel so it is moving really fast when we blow it out of the back of the engine (remember Metzger’s First Law). Well, we are in luck. The sun is the perfect engine. In fact that’s all it is. It’s one big fusion reactor. And the really amazing part is that it is almost all fuel. There is very little overhead. If and when we ever build a fusion reactor on Earth, the thing will probably weigh in at several thousand tons and be able to fuse a few micrograms of hydrogen. Not a very efficient use of mass. The sun is 78% hydrogen by weight, all of which can be used for fusion to generate energy.
What else does the sun have? It is in possession of some really intense magnetic fields. And that is a good thing, because we can take advantage of those fields. Here is where I wave my future technology wand. I will speculate that in the not too distant future (100 to 1000 years) that we can perturb the magnetic fields in the sun. And why would we want to do that? The reason is that if you take a hydrogen atom (which consists of a proton and an electron) and ionize it (remove the electron from the proton), what you are left with is a positively charged proton and a negatively charged electron. Forget about the electron (it weighs some 1835 times less than the proton), and use the proton as the mass which you are going to shoot out of the Sun. It will be no problem. If you shape those magnetic fields right, the positively charged proton can be shot out of the Sun moving at nearly the speed of light. It’s just like a particle accelerator.
We’ll need a lot of protons.
The sun weighs 2×1030 kilograms (a 2 followed by thirty zeros), while a single proton weighs in at 0.167×10-26 kilograms (that is 26 zeros before the decimal place). However, that is for a proton which is sitting still. If you get it going near the speed of light (3×108 meter/sec) then its mass increases (special relativity). For this little example, let’s assume that we can use those magnetic fields to push the proton up to 99.9% of the speed of light. In that case, the proton’s mass has increased by a factor of 22 and now weighs in at 3.74×10-26 kg. Well, shooting one relativistic proton out of the sun is not going to move the sun very fast by Metzger’s First Law. In fact, its velocity is going to be 5.61×10-48 meter/sec. This is definitely not very fast. In fact, at this speed, if you wait 10 billion years, the sun would have moved some 10-30 meters, or roughly one-billion-millionth of the width of an atom.
This is not what I would exactly call interstellar travel distances.
Obviously, what we need are more protons being shot out of our proton propulsion system. Let’s make it easy on ourselves, and say that we would like to get the Sun moving at 20% of the speed or light – .20c (that’s a good value – fast, but not so fast that the Sun’s mass increases very much due to relativistic effects). So by Metzger’s First Law, to get the Sun moving at .20c we would need to shoot out a mass moving at the speed of light which weighs .20 times the weight of the sun. That sounds bad. If we threw away 20% of the sun’s mass some bad things might happen on Earth. The gravitational tug on Earth would lessen, and our orbit would slip further out. Also, the energy output of the sun would lessen (it’s now got less fuel burning). Both these effects would really cool down the planet (perhaps that would be a good thing if we hadn’t yet addressed global warming). But fortunately, since our protons are now so heavy (because they’re moving at 99.9% c, and their mass has increased by a factor of 22), we need to roughly throw out only 1% of the Sun’s mass as long as it is in the form of these heavy protons.
Not so bad.
So here is the plan.
We turn on our proton rocket engine, and keep the exhaust pointed in the opposite direction from Alpha Centauri (you need to remember that the sun is rotating on its axis once every 25 days at the equator, so we need to keep shifting the location of our proton exhaust to take this into account). Let’s accelerate at a very gentle 0.01 g – that is only 1/100 of the gravitational force that we feel on Earth (by contrast astronauts may pull any where from 3 to 10 gees when launching from Earth). After one day of accelerating at that low rate, the Sun is already moving at 18,000 miles per hour. What we need to do is keep accelerating until we cover 2 light years distance (the half way point), and then turn the direction of our proton exhaust by 180°, so that we can then decelerate back to zero velocity over the next 2 light years (quite some braking distance). So the question is, how long does it take to cover those 2 light years, and what is your velocity when you reach that point? The equations are really easy:
D = .5AT2
V = AT
Where D is the distance covered (in this case 2 light years which is 1.86×1016 meters), V is the velocity of the sun when you reach 2 light year mark, A is the acceleration (which for 1/100 of a g is 0.098 m/s2) and T is the time in seconds. Performing those calculations (I will leave that as an exercise for the reader), it turns out that the 2 light year distance is covered in 19.5 years, at which point the velocity of the solar system will be just .2c. Isn’t that handy, since I have already showed you that by Metzger’s First Law we can get the solar system moving to .2c by throwing out 1% of the sun’s mass, just as long as the proton exhaust is moving at 99.9% of c. During our 19.5 year outbound acceleration we are tossing protons out of the sun at a rate of 6.6×1020 kg/sec. That is a lot of protons (actually 1.77×1046 protons/sec). Once we reach the halfway point and turn the direction of the proton engine, it takes another 19.5 years to bring the sun to a stop right in the neighborhood of Alpha Ceauri. Total trip time is 39 years, and you’ve used up 2% of the Sun’s mass.
39 years is nothing – half of a human lifetime. And remember that you never even had to leave home. Once you get to Alpha Centauri you can explore, take pictures, visit the locals, colonize, do whatever you’d like. You can refuel the sun by gobbling up whatever gas giants you might find there, or by siphoning off a bit of the local Sun’s mass. And then you can be on your way to the next solar system that you’d like to explore.
Make it a 3 million year trip – the scale of time during which proto-humans evolved into us. If you arrive at a new solar system every 50 years, then the human race will have explored some 60,000 solar systems and traveled 240,000 light years during those scant 3 million years.
240,000 light years!
The diameter of our galaxy is only 100,000 light years. During those 3 million years you could travel from one end of the galaxy and back again. And after all that exploring, perhaps the human race would be ready to make the big jump to neighboring galaxies. Andromeda is only 2.2 million light years away. So what if it takes us some 11 million years to get there. That is just a blink in geological time.
And what does it matter, because we will have never left home.
And think about this. Why stop at merely moving the Sun. The same approach could be used to move entire galaxies. We all know that the universe about us is expanding, all these distant galaxies hurtling away from us, all this motion an artifact of the Big Bang. Perhaps not an artifact of the Big Bang. Maybe the resident big brains of our universe have converted the galaxies into massive spacecraft, and they are just going on a little outing to visit the neighbors.
NEWS YOU CAN USE
Fusion reactors in science fiction are as common place as Star Trek novelizations – all pretty much the same thing, based on the same premise, using the same old tired technology. Fusion reactors come in two flavors – get a big plasma chamber, add monster superconducting magnets to hold that plasma in, and then push the temperatures and pressures high enough (trying to build a little sun) and atoms fuse together, throwing off some energy. The other approach is to bombard a small pellet of fuel with some mighty laser/ion beams, and as the pellet implodes due to the shockwave generated, the atoms in the pellet fuse together, throwing off some energy.
That’s how it’s typically done in science fiction.
And that’s also how it’s typically done in the real world. No, at the moment there are no actual fusion reactors producing more energy than they consume, but things are getting close. In the next ten years a monster called ITER (International Thermonuclear Experimental Reactor) which will cost $10 billion may be built, and may just produce more energy than it consumes. ITER follows the old tried and true approach of building a little sun by getting a plasma as hot and dense as possible. Other folks at Lawrence Livermore Laboratory are about to break ground on the NIF (National Ignition Facility) and will give the laser implosion approach a go around.
Those are the two politically correct approaches.
Those are the two which fill our science fiction futures.
But those futures may not come to pass. A few new things are on the fusion horizon. I’m not talking about cold fusion in test tubes, or someone selling snake oil and fusion reactors from the back of a van. This is real.
The Z Machine (1). Forget all those liquid helium cooled superconducting magnets to hold your plasma in. There are other ways to generate a magnetic field. Any time electric current flows through a wire, it generates a magnetic field. What researchers have done at Sandia National Laboratories is to send an enormous blast of electricity through an array of parallel wires – enough electricity to vaporize the wires, transforming them into a plasma, which in turn gets compressed by the magnetic fields generated by the current flow. Compressed plasma gets hot – in this case 1.5 million degrees. Right now the experimental Z machine can produce about 20% of the energy, 40% of the power, and 33 to 50% of the temperature required for nuclear fusion to produce more energy than it consumes. As a bonus, this machine produces X-rays in the 200 terrawatt range (that is million-million watt), more than enough to X-ray every set of teeth on the planet.
Xenon droplets (2). You might think that 1.5 million degrees is hot, but compared to what physicists at Imperial College in London have heated up, the Z-machine might as well be spitting out ice-cubes. By hitting a microscopic droplet of xenon atoms (with about 2500 atoms) with a laser beam, the electrons are torn from the xenon atoms forming an electron cloud which then absorbs energy from the laser. This energy is then transferred to the xenon ions (a xenon atom which is missing some electrons), heating them up to temperatures as high as a reported 940 million degrees, which is 30 times hotter than the core of the sun.
There is more than one way to fuse a cat. Let’s see some creative fusion reactors.
A strange sighting which I’ve recently heard about is that of flying frogs (3). These frogs are not flying about by way of some mutant flapping wings. It’s nothing that complicated. These frogs use diamagnetism to perform this feat. When a diamagnetic material is placed in a magnetic field, the electrons orbiting the atoms within the material have a tendency to line up, generating a magnetic field which opposes the field that it’s been placed in. And just what materials are diamagnetic? Almost anything if a large enough external magnetic field is applied.
This includes frogs.
A consortium of researchers from such prestigious institutions as The University of Nijmegen in the Netherlands, the University of Sao Carlos in Brazil, and the University of Nottingham in England used a powerful solenoid magnet (think wires wrapped around a pipe), and placed a frog inside the center of the magnet.
The magnet turns on, and the frog floats.
They’ve also reported success with grasshoppers, plants and water droplets.
The race has begun. I’m certain that it is only a matter of time before monstrous solenoid magnets are installed in Disneyland or Las Vegas (the line between those two continues to blur) so guests may float about. If those two locations are a bit too alien for you, then consider some distant planet with a magnetic field so powerful that the resident aliens can float within it.
Another strange sighting has been reported by Marcus Chown (one of our fellow SFWA members) in a piece he wrote about the trouble when animals come into contact with the Tevatron particle accelerator at Fermilab (4). As expected, there are any number of roasted raccoons, rodents and reptiles which squirmed their way into the facility in search of warmth and then get toasted on megavoltage equipment. Nothing all that weird there. The real weirdness has to do with the 40 buffalo which live at Fermilab. They scamper about the grounds. Some of the locals believe that the buffaloes are very sensitive to radiation and that the labcoats at Fermilab use them as an early warning system. Other rumors deal with a mutant 4 meter tall buffalo which has taken a few too many protons to the chromosomes.
Hello, let me talk to Chris Carter of X-Files.
Look Ma, No Engine
Getting a person, or a piece of equipment into orbit is mighty inefficient. You either need to strap on some huge solid rocket boosters and fuel tanks onto the spacecraft, or put the payload on top hundreds of feet of fuel and engines which will be jettisoned on the way to orbit.
What you need to be really efficient is a rocket without an engine or fuel. Just make the whole thing payload. Well, a group of scientists at the USAF Research Laboratory’s Propulsion Directorate at Edwards AFB, and at NASA’s Marshall Space Flight Center at Huntsville, have succeeded in launching a vehicle which has no engine or fuel.
You haven’t heard about this breakthrough?
The craft weighs 50 grams and it has reached altitudes as high as 14 feet.
Well, the technology is not quite at the point where you can line up and buy a ticket to launch yourself into Earth orbit, but this still represents a breakthrough. How this little spacecraft works is that a 10 kW pulsed laser is aimed at an annular chamber at the bottom of the craft, where the laser beam is focused, and then bursts the air in that region into a plasma, which in turns explodes away from the rocket, creating thrust. Plans call for the laser-based projectile to reach an altitude in excess of 3000 feet in 18 months. Eventually, an orbital concept would use a ground based laser to heat air while the craft is still in the atmosphere, and then onboard gas when in space.
No engine required. (5)
Turbolution is my word, so please be sure to mention my name when you pick up your Hugo for the story which features this little technology gem. Evolution is a drag. It works so, so slow. Yes, if a species gets the crap knocked out of it for a few million years, and manages not to go extinct in the process, then said species may grow 25% larger and sport a new set of fangs to defend itself.
What we need is turbolution – something to allow a species to evolve in an afternoon. Well, thanks to group working at the Centre for Computational Neuroscience and Robotics at the University of Sussex, they may have opened the door to turbolution. Consider a typical species which can reproduce itself in five years. In one million years that means you’re looking at 200,000 generations. Not too bad – hopefully something new can evolve in that amount of time.
Now, consider if you are not operating in the organic world, but instead, in the inorganic world – in this case a world dominated by Silicon. These researchers are using a special type of Silicon chip to study turbolution – a field programmable gate array (FPGA). This is a piece of Silicon hardware which can be rewired by software into a nearly infinite number of different types of circuits. One moment the circuit is a modem, and the next it is an amplifier.
As an example, suppose you want to build a circuit in which its output is run into to a speaker, and you want the speaker to say “Hello Dave, this is Hal”. How would you design such a circuit? I don’t know, and with an FPGA and turbolution you don’t need to know. Just start off with a few thousand transistors randomly wired together, and use an audio comparator to check its output to your desired one. Try it 100 times. The ten which come closest you keep, and the other 90 you toss out. You then take the 10 close ones and have the computer randomly rewire some of the transistors. You try another 100 times and again pick out the ten best. You run this process as many times as needed until your circuit tells you what you want to hear.
How long would it take to run those 200,000 generations? The chip can be reconfigured in a matter of milliseconds. The real time is consumed with each version of the chip being allowed to babble for the 2 seconds it needs in its attempt to say “Hello Dave, this is Hal”. So if it takes 2 seconds for an attempt, how long does it take for 200,000 attempts (remember that for the organic it took 1 million years). I’ll do the math for you. It would take 4 days and 15 hours! This improves on organic evolution by a factor of nearly 80 million.
Think about what this means. Build a brain in hardware that can direct its own evolution, and you will find that if it was able to burp and recite Nursery rhymes on Monday morning, that come Friday afternoon, it will have ignited its own Big Bang and become the God of its own universe. (6)
Tabletop Black Holes
Here is a bit of Physics 101 for you. The word power is used all the time, and quite often used incorrectly. Power is defined as the time rate at which work is done, or the amount of energy consumed in a unit of time. A 100 Watt light bulb delivers 100 Watt of power, and in the process it burns up energy at a rate of 100 joules per second (that is how one defines the unit of energy measurement – joules). So who cares? If you burn this energy at twice the rate, then you would have a 200 Watt light bulb, but of course, if you had a fixed amount of energy, it would only burn for half as long before that energy was used up. The faster you use it, the greater the power, but of course that power lasts for a shorter amount of time. Energy is conserved.
Again, so what?
If you take a modest amount of energy, but use it up extremely fast, then for that brief moment, you can generate some fantastically large powers. This is how a new generation of extremely high power lasers are being built, lasers which fire their pulse of energy in times which are measured in femtoseconds (which is one million-billionth of a second – 10-15 seconds). These lasers are now capable of producing power of 1015 Watt, which is a fantastic power level, even though the total energy dissipated is comparable to that burned by a 1 Watt light bulb in 1 second. But in this case that modest amount of energy was burned so incredibly fast. Again, and for the last time, so what? Well, during that femtosecond time interval, so much energy is packed into so short a time and in such a small volume of space, that any charged particles trapped in that region would experience the accelerations, and the electric/magnetic fields that, a particle would experience close to the horizon of a black hole.
Think about that the next time you flip on a light bulb.
Remember to turn off the black hole when you leave the room. (7)
BITS AND PIECES
- Still outlining that 27 volume Mars epic, and want to make sure that you have the latest data before you start terraforming? Then I suggest you check out a special issue of Science which has every detail of the recent Pathfinder mission. (8)
- The University of Tokyo has developed the first biomechatronic robot, by interfacing a cockroach with a robot, in such a manner that the cockroach’s nerve impulses run the robot. Great – a robot which tries to burrow under the refrigerator when the kitchen lights come on (9).
- Another vermin tale. Having trouble routing the latest high speed cable through your business or home? No problem, just call up Rattie. Wearing a harness to pull a nylon string and computer cable behind her, this rat can get the job done. She doesn’t even mind working around asbestos. (10)
- How many elements are there? In the prenuclear days the periodic table ended at element 92 – uranium. Today, atom smashers have pushed the number of elements up to 112. But most of these superheavy atoms are extremely unstable, decaying into lighter weight elements within a few milliseconds. However, theory predicts that element 114 may be quite stable. And what might one make with a stable superheavy element which has never before existed? How should I know? You guys are members of the SFWA – you figure it out. Oh yes, element 126 might be even more stable than 114. (11)
- Ivars Peterson, “The Z Machine,” Science News, Vol 153, January 17, 1998, pg. 46.
- Jeffrey Winters, “Cluster Bombs,” Discover, January 1998, pg. 52.
- Corinna Wu, “Floating Frogs,” Science News, Vol 152, December 6, 1997, pg. 362.
- Marcus Chown, “Reckless Raccoon’s Big Day,” New Scientist, December 20/27, 1997, pg. 56.
- Paul Proctor, “Laser Thrust Flies,” Aviation Week and Space Technology, September 29, 1997, pg. 15, and Aviation Week and Space Technology, November 3, 1997, pg. 19.
- Clive Davidson, “Creatures from Primordial Silicon,” New Scientist, 15 November 1997, pg. 30.
- Gerard A. Mourou et al, “Ultrahigh-Intensity Lasers: Physics of the Extreme on a Tabletop,” Physics Today, January 1998, pg. 22.
- M.P. Golombek et al, “Overview of the Mars Pathfinder Mission and Assessment of Landing Site Predictions,” Science, Vol. 278, 5 December 1997, pg. 1743.
- Philip Yam, “Roaches at the Wheel,” Scientific American, January 1998, pg. 45.
- Toni Feder, “Rat Wires Schools for the Internet,” Physics Today, January 1998, pg. 51.
- Richard Stone, “An Element of Stability,” Science, Vol 278, 24 October 1997, pg. 571.
Bob Metzger received his PhD in electrical engineering from UCLA in 1983. He spent 10 years at the Hughes Research Labs in Malibu, California, building high-speed electronic devices and trying to beat obnoxious atoms into submission. He is currently on the faculty of the Georgia Institute of Technology in Atlanta GA, where he now attempts to beat both obnoxious atoms and students into submission. He writes a science column for Aboriginal SF, and his fiction has appeared in Aboriginal, Weird Tales, Fantasy and Science Fiction, Amazing, and Science Fiction Age. His novel Quad World was published in 1991 by Roc. His e-mail address is [email protected]