To the stars

Ken Tapping, July 31st, 2018

In the sky this week…

  • Venus lies low in the west after sunset, with Jupiter in the southwest and Saturn in the south after dark.
  • Mars, shining like a red lamp, rises around 10 pm.
  • The Moon will reach Last Quarter on the 4th.

Although at the moment we have no technologies that can get us to the stars in a human lifetime, our science fiction writers have been out there among the stars for decades. They have come up with various means of reaching the stars and exploring our galaxy. Let’s look at a few of them

The brute-force way to get to the stars is to accelerate as close to the speed of light as possible. This will bring the nearest star or two within reach. Some authors have written about “generation ships”, where generations of people live and die en-route on journeys of hundreds or thousands of years. One serious issue here is that we have not yet managed to sustain a stable artificial ecosystem for even years, let alone centuries or millennia. Moreover, travelling at a good fraction of the speed of light runs into another issue. Space is not empty; there are always at least a few atoms per cubic centimetre, sometimes many more, along with dust grains and so on. Our fast-moving astronauts would be hitting those atoms and dust grains so quickly the experience would be like exposure to high levels of radiation.

Wormholes are tunnels in space-time that connect one place in space and time to another. We have not yet found any of these, but there is no reason why they can’t exist. In the stories you fly your spaceship into one of these and almost instantly come out at some distant location, often at a different time. The problem is that the gravitational stresses needed to hold such things open are so strong that your spaceship, you, and even the atoms you are made of would be torn apart, back into the primordial “stuff” that existed just after the Big Bang. It would not be possible to put you back together again at the other end, or even identify what stuff was originally you.  Unless we can find or make some very special-purpose wormholes, with properties we cannot even imagine at the moment, the wormhole idea is a non-starter.

Many authors and film writers have come up with terms like “warp drive”, “hyperspace” and so on. The idea is that by moving in other than the four dimensions we live in (taking time as the fourth dimension) there could be a shorter route. Imagine a two-dimensional creature living on a rolled up map. Instead of a long journey it could go through the map to the layer underneath, a much shorter distance. This is mathematically possible, but at the moment we have no idea how to do it.

There was a period just after the beginning of the universe where everything expanded at a speed faster than light. This was not breaking any rules. Einstein showed we cannot go through space-time faster than light, but in this case all of space-time was expanding, carrying everything with it. Imagine our ship sitting on the fabric of space-time. By some method or other we pull in more of the fabric in front, stretching it, while the stern of our ship is firmly anchored. Then we let go of the fabric at the stern, and as it unstretches, it carries us forward. It would be best if we could do this as a continuous process rather than going forward in jerks. Since we are always travelling with space-time, our relative speed is zero, but we could actually be moving at almost any speed. All the dust and atoms near the ship would all be travelling along with us, so there should be no high-speed impact or radiation issue. Once again, we can see how the physics works, but as yet we have no idea how to do this in practice.

The ideas are out there, and more are coming. Looking back at the achievements our species has made throughout a few thousands of years of history, especially over the last century, if we really want to reach the stars, we will find a way to make it happen. There is a lot out there to explore.

Ken Tapping is an astronomer with the National Research Council's Dominion Radio Astrophysical Observatory.

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