The distance between the stars is great, and any aliens trying to visit Earth would have to travel the great gulf that separates suns. The closest star to the Earth, Proxima Centauri, lies just 4.2 light years away. This means that if you shone a beam of light from your back garden, it would take just over 4 years for that light to reach the closest star.
What kind of technology would alien civilizations use if they wanted to visit us here on Earth? Firstly, they would have to figure out a way to travel really fast. By comparison, some of the fastest rockets ever launched would take over 70,000 years to reach Proxima Centauri. While it’s possible that aliens might travel between the stars slowly, and perhaps hibernate during the long trip, it’s far more likely that they’d try and figure out ways to travel extremely fast between the stars.
The trick needed to get from point A to point B is to simply travel faster. Easy, right? Well, scientists have calculated that to travel from Earth to Proxima Centauri in just 50 years would require a rocket ship bigger than our own Earth! This is because rockets are not a very good way to give spacecraft the speeds needed to get to the stars.
The fastest way to get between the stars is to travel faster than the speed of light. A ship travelling 100 times the speed of light could get from Earth to Proxima Centauri in a little over two weeks! Not much more time than it took us to send men to the Moon and get them home safely.
The problem with travelling faster than the speed of light is a frustrating little part of physics known as Einsteins Theory of Relativity that says that no object can travel faster than the speed of light. Einstein created a sort of cosmic speed limit that limits us to travelling slower than the speed of light.
How could you break that speed limit and travel much faster? Physicists believe that when the universe was first born from a big bang, that space itself traveled faster than the speed of light as it expanded creating the universe as we know it.
Some physicists have calculated what it would take to create this kind of effect around a space craft, and have called this type of travel a ‘warp drive’ taken directly off of the famous science fiction show Star Trek. In 1994, a Mexican physicist called Miguel Alcubierre wrote a paper called “The Warp Drive: Hyper Fast Travel within Relativity”. This paper was published in a famous scientific journal, and other scientists checked the physics in the paper to check that the maths and physics was correct.
This paper, now famous, showed that it’s possible to use physics to figure out how to travel faster than the speed of light. We don’t know how to turn this from a research paper into a working warp drive rocket, but perhaps aliens thousands of years more advanced than us have figured this out.
Given that the universe is over 13 billion years old, and that it contains trillions upon trillions of stars, it’s highly likely that there are many extraterrestrial civilizations out there who have technology far in advance of our own. If they’ve figured out the secrets of warp drive, then they have learned how to travel between the stars in a matter of days, or perhaps even hours.