WILL WE EVER REALLY TRAVEL TO THE STARS?

Interstellar space travel is one of the most common themes of science fiction, but the question is, will it ever become reality?

With our current understanding of physics, propulsion methods and the limits of our technology, there is currently no practical way to travel to other stars and solar systems. NASA terminated its Breakthrough Propulsion Physics Program in 2003, stating that no further breakthroughs appeared to be imminent. What this ultimately means is that we should not be expecting to see travel to other stars become reality any time soon, if ever. NASA did recently announce that they will begin work on a Warp Drive…whether anything will come of that, only time will tell. I personally would like to see this happen in the private-sector but that’s certainly unlikely for the immediate future.

In most sci-fi stories, starships zip around the galaxy at speeds far exceeding that of light, the universal speed limit of roughly 186,000 miles per second. The problem however is that the laws of physics state that absolutely nothing in the universe can travel faster than this (even though folks are trying to prove otherwise).

The Primary Issue – Distance

We know our own star simply as the Sun. The Sun is a star no different to billions of others in the Milky Way galaxy. To provide some important figures for reference, the Sun lies 93 million miles from away from Earth and it takes light eight minutes and twenty seconds to reach us.

Source: NASA
Source: R. Mewaldt & P. Liewer, JPL

The nearest star to Earth, other than the Sun, is Proxima Centauri of the Alpha Centauri triple-star system. It lies 4.24 light-years away, meaning that it takes 4.24 years for the star’s light to reach us.

The fastest launch speed achieved by mankind was that of the New Horizons robotic spacecraft which was launched at 36,373 miles per hour on its mission to the dwarf planet Pluto. The fastest man-made object is currently the Helios 2 solar space probe, travelling at 157,100 miles per hour. This speed was achieved by using gravitational assistance from the Sun. If the Helios 2 solar probe were to be sent directly towards Proxima Centauri, it would reach the star in approximately 18,000 years.

How Fast Can We Go?

There are technologies that exist which can achieve far greater speeds than those of space probes like Helios 2 or New Horizons.

One of these is nuclear pulse propulsion which basically uses nuclear explosions to power a rocket to incredibly high speeds. It seems plausible that such a spacecraft could reach speeds of around 5 percent of the speed of light, yet this would still take about 85 years to reach the nearest star. As demonstrated by the Project Orion effort of the mid-twentieth century, it is possible using only currently available technology. Of course, this speed is still too low, making it highly impractical. It is generally considered that, if a journey cannot be completed in considerably less than a human lifetime, it should not be started at all.

The only thing that is possible is to send out radio waves, traveling at the speed of light, to the stars. This allows us to send a message to Proxima Centauri for example, which would arrive in 4.24 years. Perhaps some day we will be able to send physical objects there at this rate.

Faster-than-Light (FTL)

Image Source: Nextbigfuture
Image Source: Nextbigfuture

Nothing can travel faster than light, as dictated by Einstein’s theories on relativity. Roughly 186,000 miles per second is the absolute speed limit. If practical interstellar travel is ever to become a possibility, we need to find a way around this speed limit.

To get around the FTL issue, sci-fi shows/movies/books often use things like warp drives that are capable of warping spacetime in such a way that it folds space. If this were possible, it would effectively enable FTL travel between two points. The Alcubierre drive, proposed in 1994, is the only serious attempt at theorizing a starship which travels faster than light. It does this by expanding space behind it and contracting space before it. The spacecraft travels in its own bubble at speeds slower than light. To put this in perspective, imagine a piece of paper with a point marked at each end. The shortest distance between these two points is a straight line, unless you fold the paper in half so that the two points meet each other directly.

The Alcubierre drive is highly theoretical and has one deal-breaking flaw – it requires something called exotic matter with negative mass, and this isn’t even known to exist.

The Bottom Line

Space Travel ConceptIf you could go back in time to the mid-nineteenth century and tell people that humanity was going to land on the moon in 1969, they would probably laugh at you. Since then, we have launched probes all over the Solar System and landed robotic spacecraft on the surfaces of Venus, Mars and Saturn’s moon, Titan. One thing is clear: Humanity’s potential is immense and science and technology are full of surprises. Interstellar travel may seem like a very long way off, but it will never become a reality if we don’t try.

One thing that is preventing many scientists from taking interstellar travel seriously is also the fact that we don’t really know where to start. There are countless stars out there, but until something truly interesting and worth visiting shows up, interstellar travel will remain a thing of science fiction. That being said, more than 850 planets have been discovered orbiting other stars and more are being confirmed every week. We are now learning that every star “up there” likely has a number of planets rotating around them (the same thing that happens in our neck of the universe). That’s a very, very large number of planets. It is likely just a matter of time before we find an Earth-like world out there in the lonely depths of space. Perhaps that will truly give humanity something to aim for resulting in a renewed interest in reaching the stars.

Reference:

Ford, L., & Roman, T. (2000). Negative Energy, Wormholes and Warp Drive Scientific American, 282 (1), 46-53 DOI: 10.1038/scientificamerican0100-46

Hill, J., & Cox, B. (2012). Einstein’s special relativity beyond the speed of light Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 468 (2148), 4174-4192 DOI: 10.1098/rspa.2012.0340

González-Díaz, P. (2000). Warp drive space-time Physical Review D, 62 (4) DOI: 10.1103/PhysRevD.62.044005

Hansson, A. (2003). Project Orion: The Atomic Spaceship 1957–1965 Space Policy, 19 (2), 149-150 DOI: 10.1016/S0265-9646(03)00011-0

Endl, M., & Kürster, M. (2008). Toward detection of terrestrial planets in the habitable zone of our closest neighbor: proxima Centauri Astronomy and Astrophysics, 488 (3), 1149-1153 DOI: 10.1051/0004-6361:200810058