The Science of Sci-Fi: Getting around in space.

Now for part two of my epic sci-fi saga: getting around in space (I realise that that isn’t really a good name for a sci-fi movie… well maybe if it was on REALLY late at night). Or on the internet.

Anyway, moving on. 

A spaceship. Yup. Can't really think of a funny caption. Sorry. © innovari - Fotolia.com

Continuing the science of sci-fi series, I’m going to talk about interstellar travel. The ability to travel the vast distances between stars is a staple of most sci-fi universes, but what about our own? The concept of traveling to another solar system brings with it a lot of obstacles which need to be overcome.

The problem with interstellar travel is distance (who’da thunk it?). The distance between Earth and our closest star system, Alpha Centauri is about 25.6 trillion miles away, or 4.3 light years - that is to say it would take a beam of light 4.3 years to travel there from our sun.  So, y’know, It’s a long way. The human race has done some unmanned interplanetary travel within our own solar system and even technically outside its edges, but no human being has ever set foot on another planet – just our moon.

Science has been sending unmanned probes out into space since the launching of the first earth satellite, Sputnik-1, in 1957 which orbited earth for three months, sending radio pulses back to earth. I’m not going to get into the whole cold war space race thing because it’s not relevant here and when science wins, everyone wins (I know you can’t see it, but I just gave a thumbs up with a huge grin and one of my teeth twinkled with a PING). 

The Mariner 10 probe, brought to you by the high-tech 3D redering of the 1970s (source)

Since then there have been numerous probes sent throughout the solar system by various countries.  The Mariner 10 probe was launched by NASA in 1973 with the mission of investigating Venus and Mercury which are 38 million kilometers and 77 kilometers from Earth (at their closest orbits to Earth) respectively. The probe took several thousand photos of the surface of both planets along with collecting data about the atmosphere and magnetic field of both planets. The Mariner 10 finished its mission in 1975 and is thought to be currently orbiting the sun.

The infamous 'accidental' tracks left by the Spirit rover. You might say they made something of a boner

(source)

Perhaps better known are the Spirit and Opportunity rovers that were sent to Mars by NASA in 2003. Landing in 2004, the rovers surveyed the surface of Mars to look for signs of water activities. The Spirit rover became unresponsive in 2010 (maybe it became… SELF AWARE!! …no actually, they just lost contact with it), but the Opportunity rover is still rolling along the surface of Mars, nine years on from the start of the mission – not bad for a piece of equipment designed to last three months. Pros of this mission: it gave us insight into the geological history of mars. Cons: the spirit rover accidentally drew an *ahem* interesting shape on the surface of the red planet shortly after landing in 2004 – probably what it’s most famous for (welcome to the internet).

This blue dot is the first radio transmission from the first man-made object to leave our solar system. Or maybe its just something someone knocked up in Photoshop - who knows? (source)

So, it seems we have become quite adept at shooting robots into space – but what about beyond the limits of the solar system? Well, the closest we have come was when the Voyager 1 probe crossed over the outer limits of the solar system in August 2012 after 36 years in space and 11 billion miles traveled. In February 2013 a radio signal was received from the Voyager from beyond the orbit of our sun – the first signal to be broadcast from interstellar space. The signal was picked up by radio telescopes on earth as a tiny blue dot.

So why haven’t we gone outside our solar system? Traveling at the top speed of Earth’s current space shuttles (about 28,300 km/h) it would take 165,000 years to get to the Alpha Centauri system – several times longer than the written history of the human race - which makes for something of an inconvenient flight (Are we there yet?). And that’s only our closest star. Of course, one way we could go all over our galaxy (and beyond) would be travel very very very fast. Unfortunately this is never going to happen based on conventional jet propulsion systems as it takes 3,000,000 lbs of rocket fuel to send a shuttle just into Eath’s orbit, which is more than 15 times the mass of the shuttle itself, so you can imagine the amount of fuel required to take an interstellar star ship to Alpha Centuri. Engineers and scientists are working on this problem and there are several theoretical and proposed alternatives to conventional methods, but I will talk about those later – first we have to address perhaps the biggest obstacle to deep space travel.

The Speed Limit of the Universe

Much like the motorway/freeway/highway, everything in the universe has a speed limit but, unlike the speed limit on the roads, it is the speed of light and it cannot be broken. Well breaking the speed limit on the road is illegal but it is POSSIBLE – an act that I in no way endorse. Neither do I endorse breaking the laws of physics on the highway – that’s neither funny nor clever. Anyway, you guessed it folks – it’s time for the maths stick once again. In order to explain why nothing in the universe that has mass can travel faster in the speed of light we have to take a look at the most famous mathematical equation in history. You’ve guessed it:

E=mc² 

This is the equation for Albert Einstein’s famous theory of special relativity. In this equation E stands for energy, m stands for mass and c² stands for the speed of light (300, 000, 000 meters per second ) squared. The c in this case stands for constant, as the speed of light in a vacuum which is always the same. Now – if you read my last article you might have guessed that I am not great at mathematics. In fact I suck at it (no – this is not an appropriate place to say ‘that’s what she said’) – so hopefully this explanation is satisfactory. 

Albert Einstein circa 1921, photographed Ferdinand Schmutzer (source)

The equation explains the relationship between mass and energy. I’m not a physicist and trying to explain this in detail would confuse everyone, most of all me, so I will keep it simple. Einstein’s theory states that mass and energy are interchangeable and are just two different forms of the same thing. The faster an object is moving, the more energy it has and therefore more mass. The closer an object gets to the speed of light, the more energy it has pushing it along which equates to more mass. 

So why don’t we notice this in real life? If energy has mass then why don’t we get heavier while we run? Why doesn’t a car get heavier as it gets faster? The answer is that it does happen – we just don’t notice it because it is so small – at the slower speeds we are used to on Earth the percentage of mass increase is tiny. It’s a different story close to the speed of light where the increase in mass would be colossal; in fact if an object moved at the speed of light it would become infinitely massive and have infinite energy. Even if the starting object has tiny mass, like a single electron, the end result would be the same.

So based on Einstein’s equation it would require an infinite amount of energy to travel at the speed of light, making it effectively impossible. So how might we overcome this obstacle if we are ever to travel to other star systems? Both science and fiction have several ideas to get over it.

Cheating Physics – Getting to Other Stars

As I mentioned earlier, our current technologies wouldn’t allow us to make the massive journeys between stars – even if we could get up to a decent speed, the amount of fuel required to power a large star ship would be a *ahem* $@#%load (scientific term). So one way we could approach being able to travel between stars is to develop more efficient propulsion systems.

There are several theoretical and proposed alternatives to current jet propulsion technologies. One such idea is using an antimatter rocket – a rocket engine which generates its thrust with antimatter. Antimatter is basically the ‘evil twin’ of matter particles in our universe – they are particles with the exact opposite properties of matter. For example, the antimatter equivalent of an electron is a positron. Electrons are negatively charged particles which are found in all atoms – their antimatter opposites have the same mass but the opposite charge. When a particle of antimatter meets a particle of matter they annihilate – a reaction which destroys both particles, converting them into the energy equivalent of the mass of both particles. Antimatter annihilation can produce an insane amount of energy from a tiny amount of matter which makes it an ideal rocket engine. Unfortunately antimatter is very hard to make and so far only 38 atoms of anti-hydrogen have been created, lasting only 0.2 seconds before annihilation. Another candidate for getting us close to light speed is nuclear fusion engines, which generate energy and thrust through the process of nuclear fusion – this is when two atoms fuse together to form a heavier element – releasing energy in the process. This is much more efficient than rocket fuel and could take us to (relatively) nearby stars with much smaller rockets.

So assuming we could use one of the many theoretical propulsion systems to get our space ships close to the speed of light and we wanted to travel to a star system a little less than 200 light years away, how would we deal with the problems of making the 200-or-so-year journey there? Again, there are several speculated solutions to this problem. A few of them are actually kinda weird. One proposal is a generation ship – a huge starship where the descendants of the original crew would be the ones arriving at the destination. Of course this would require building a ship capable of sustaining a functioning human society for 200 years, which I don’t think anyone knows how to even begin trying to do. Then we have suspended animation – this would work too for shorter journeys of a few years as well. This one has been in a good few Sci-Fi movies and shows – probably most recently in James Cameron’s 2009 epic, Avatar and the brilliant 2012 prequel to the Alien films, Prometheus by Ridley Scott. This method would involve slowing or pausing the aging process by freezing the passengers of a mission or putting them in deep sleep and waking them up at their destination – again unfortunately no such technology currently exists, but could offer a method of getting people to distant star systems in the future. Another idea is to send frozen fertilised human embryos into space and have them ‘revived’ by a robot (unfortunately not like C3PO) when they are within some years of their objective. Those are probably three of the least weird ideas – there are many more you can look up.

An almost-universally recurring staple of science fiction is faster than light, or FTL, travel. There are also many proposed mechanisms for this one and they are even more theoretical than the stuff I’ve mentioned before. Perhaps one of the more popular ideas found in sci-fi is that of using a wormhole to travel. This is another thing we have to thank Einstein for – working with a student by the name of Rosen he came up with the idea of Einstein-Rosen bridges – what have become known as wormholes. Wormholes are basically shortcuts through the fabric of space and probably the best way to explain it is the analogy which gives it its name. Imagine that the universe is a giant apple and you are at point A and want to get to point B which is on the other side of the apple. You would have to walk from point A to B which would take a few hours (it’s a really big apple) but a worm could get through the apple much more quickly (in less than one hour) by munching its way through the tasty tasty universe – by creating a wormhole. Unfortunately they are just theory at the moment and Einstein speculated that they would be very unstable and collapse almost immediately after coming into existence.  If we could work out a good way to create and stabilize wormholes (like a Stargate?) then we could, in theory, travel to distant stars and even galaxies almost instantaneously.

Well, that about wraps it up for this week. I know what you are thinking: ‘Adam, you should stick to the biological sciences.’ – if you have any complaints about the length, content or nonsensical-ness of this article, please write to our complaints department at 123 Fake Str… oh, sorry – we don’t have one. My mistake.

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