Lightspeed: Edited by John Joseph Adams




Is There Anyone Out There Who Wants To Go Fast?

That’s the question posed in the movie Talladega Nights: The Ballad of Ricky Bobby. Ricky Bobby wants to go fast and thinks that driving NASCAR fits the bill. Now that is a comedy for the general public, and to the general public, NASCAR is fast. For scientists, and science fiction fans, however, that’s a ridiculous position.

So, what is fast, then? And how fast can we go?

Well, let’s start with cars.

NASCAR racers average under 200 mph on the fastest tracks. World record cars—more rockets with wheels than cars—top out at over 700 mph, nearly the speed of sound. (That’s cool, but Buckaroo Banzai was able to drive his test car through a mountain.)

Aircraft, of course, can go much faster than that. Several times the speed of sound, in fact. For instance, the SR-71 Blackbird, which I first learned about reading X-Men, can fly at nearly 2200 mph. That’s St. Louis to Cincinnati in 8 minutes. Now that’s pretty fast.

But not fast enough to get you off the surface of the earth. For that, you need escape velocity and that’s some 11 miles per second.

Now, when talking about spacecraft speeds, or the speeds of planets or stars moving in their gravitational dance, kilometers per second are the units of choice. The Earth moves at 30 kilometers per second around the Sun. The Sun moves at just over 220 kilometers per second around the Milky Way. The Milky Way is falling through space at some 1000 kilometers per second relative to the microwave background radiation.

But, still, this is not really all that fast.

Jets from quasars, cosmic rays, neutrinos spewed forth from supernovas…ok, now we’re moving fast. 300,000 kilometers per second fast. Lightspeed. The ultimate speed limit.

Over a century ago, Einstein tried to imagine what it would be like to travel at the speed of light, and basically what he determined was that it would be pretty damn weird. The energy to accelerate to lightspeed approaches infinity, or you can look at it as your mass going to infinity. (I’m heavy enough, so I’ll choose the former perspective.) Time stretches out to infinity, too, which is a handy feature of relativistic travel. Back to this in a moment.

Our fastest spacecraft to date, Voyager 1, now pushing into interstellar space, is only moving away at about 17 kilometers per second, and it used a bunch of gravitational tricks to help get it going that fast.

Now, in principle, it’s possible to imagine traveling at close to lightspeed, but there are many practical problems. At lightspeed, specks of gravel hit like mountains, so those must be cleared out of the way one way or another. Rockets of various forms seem to fall short, requiring ratios of fuel-to-payload too outrageous to actually work. Spacecraft that don’t carry their own fuel work better: solar sails, laser or particle beam propulsion, or variations of ramjets that scoop up interstellar hydrogen as fuel on the fly. The energy and engineering both are daunting, but it may be possible, although unlikely given current understanding.

But when you talk about technology beyond the above imaginings…now that’s truly entering the realm of science fiction. Maybe dark matter particles, much more plentiful than hydrogen gas, could be made to serve as fuel. Maybe zero point (aka vacuum) energy can be exploited. Who knows? Breakthroughs are always possible.

In science fiction, of course, there are many ways to go faster than light. There’s the hyperspace of Star Wars, the warp speed of Star Trek, the space folding of Dune. And that’s just for starters. Faster than light travel is probably the most often used fantasy element in science fiction, and many of the consequences of this fantasy are not held to realistic treatments.

While it may cause a lot of science fiction fans to grumble when you say it, in the face of science today, lightspeed is a hard limit…maybe there are ways to cheat on Professor Einstein’s test, but not even Captain Kirk could do it with today’s understanding (short of reprogramming the entire universe, of course, and he would try).

This reality leaves many fans and visionaries depressed and in denial. It makes the universe look too big, they say, and our solar system the only pond we humans will ever get to swim in.

Except…there is another way of looking at the situation. With enough energy, enough speed, there is no practical speed limit in principle for the traveler.

The time dilation effects of relativity mean that time passes twice more slowly at 87% lightspeed, seven times more slowly at 99% lightspeed, a hundred times more slowly at 99.995% lightspeed, and infinitely slowly as lightspeed itself is approached infinitely closely. And a person moving at lightspeed, perhaps transformed into photons by an unknown technology, could travel everywhere in no time.

Now that would be fast.

NASA may be or may not be the future of manned spaceflight, but they’re one of the main players today and may be tomorrow, too. So, can you imagine it? An overlap of fans of car racing and science fiction, sitting down together to cheer on NASACAR? Astronauts racing to the stars? Eventually approaching lightspeed itself? Who knows what the future holds?

So, is there anyone out there who wants to go fast?

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Mike Brotherton

Mike-BrothertonMike Brotherton is the author of the science fiction novels Star Dragon (2003) and Spider Star (2008), both from Tor books.  He’s also a professor of astronomy at the University of Wyoming and investigates active galaxies using the Hubble Space Telescope and nearly every observatory that will give him time on their facilities. He is the founder of the NASA and National Science Foundation funded Launch Pad Astronomy Workshop for Writers, which brings a dozen award-winning professional writers to Wyoming every summer. He blogs about science and science fiction at