By Matt Williams | 3 April 2020
For countless generations, the idea of traveling to an extrasolar planet has been the stuff of dreams. In the current era of renewed space exploration, interest in interstellar travel has understandably been rekindled. However, beyond the realm of science fiction, interstellar space travel remains a largely theoretical matter.
Between the sheer expense involved, the need for technological developments to happen first, and the nature of spacetime itself, sending people to another star system is something that is not likely to happen for a long time – if ever. But in spite of the challenges, the hope remains.
So will humanity ever go interstellar? Let’s break it down categorically and see how hard it might be. First up, there are the laws of physics, which aren’t too accomodating on this front.
Relativity, Why Has Thou Forsaken Me?
In 1905, Einstein published his Special Theory of Relativity, which was an attempt to reconcile the laws of electromagnetism with the observed behavior of light. This theory is summarized with the equation E=mc2, where E is energy, m is mass, and c is the speed of light (squared).
Credit: NASA / Penn State University. pic.twitter.com/fDyH6SYrxK
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Not only does this equation acknowledge that the speed of light is an absolute limit, but it also has some serious consequences where motion and spacetime are concerned. For starters, Special Relativity essentially demonstrates that mass and energy are interchangeable.
Second, it shows that as an object gets closer to the speed of light (299,792,458 m/s), its mass effectively increases. As such, it takes more and more energy to accelerate the closer you get to the speed of light.
As for achieving “lightspeed”, an object’s mass would become infinite at this point, which means it would take an infinite amount of energy to push an object up to c. So from the standpoint of known physics, faster-than-light (FTL) travel is technically impossible.
Without that kind of technology or something that could push us to the edge of lightspeed, traveling to even the nearest stars would take a very long time. This is where the issue of cosmic distances comes into play.
A VERY Long Time!
Simply put, the Universe is REALLY big! Even the closest star to our Solar System, Proxima Centauri, is located over 40 trillion km (25 trillion mi), or 4.244 light-years, away. That means that it takes light from this star, moving at a constant velocity of almost 300,000 km/s (186,400 mi/s), about 4 years and 3 months to reach us.
Using conventional propulsion like chemical rockets or hall-effect thrusters (ion engines), it would take anywhere from 19,000 to 81,000 years for a spacecraft to make that same journey!
As we explored in a previous article, that is just fine if you can build a massive ship capable of supporting multiple generations of people (aka. a Generation Ship). But what about getting there within our lifetimes, or least while humanity is still likely to be around?
Technology to the Rescue?
When we say that FTL is technically impossible, it doesn’t mean it’s beyond the realm of possibility. For example, engineers at NASA’s Advanced Propulsion Physics Laboratory (aka. NASA Eagleworks) have been exploring the idea of the Alcubierre Warp Drive since 2011.
Named after Mexican physicist Miguel Alcubierre, this theoretical method of space travel involves stretching the fabric of space-time in a wave that would (in theory) cause the space ahead of an object to contract while the space behind it would expand. An object inside this wave (i.e. a spaceship) would be able to ride along without actually moving.
This idea is essentially a way of achieving FTL that doesn’t violate the laws of physics. However, the drive system remains theoretical right now and no known means exist to generate the kind of power that would be involved. Other theoretical methods of propulsion – like fusion engines (Project Daedalus and Icarus), antimatter, or nuclear rockets – are also being explored. But they are either still too slow or far from realization.
So What’s This Mean?
For now, it looks like our best bet for going interstellar is to rely on robotic spacecraft that are optimized for speed. This is where projects like Breakthrough Starshot come in, which plan to use laser arrays to accelerate light sails and tiny spacecraft to relativistic speeds (a fraction of the speed of light).
According to their proposal, their spacecraft would reach Proxima Centauri in just 20 years and send back info on the planets there. Just 25 years to learn what’s next door? Not bad, and a pretty good start to boot!
If human history has taught us anything, it’s that we love a challenge and will always find ways of exploring beyond the edge of what’s known.
Reprinted with permission from the author.
Matt Williams is a professional writer, lecturer, and science fiction author whose articles appear in Universe Today, Interesting Engineering, HeroX, Popular Mechanics, and other publications. His first collection of novels is available through Amazon, Audible, and Castrum Press. He lives in Esquimalt, BC, Canada. For more info, check out: https://storiesbywilliams.com, https://www.universetoday.com/author/mwill/ and https://interestingengineering.com/author/matthew-s-williams. Follow him at Twitter.
Finished “The Jovian Manifesto,” an absolute treasure trove of space science. https://t.co/fDYGDr89rJ It’s second in the #books series I recommended last year, so if you’re in the market for well-researched & believable-not-kitschy #SciFi #novels, check these out!
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