WELCOME ONBOARD1
One thing that the classic TV showStar Trek (mostly) got right is that starships don’t land on planets. It’s easy to underestimate just how difficult it is to get a massive object off the surface of a planet and into outer space. The problem lies in escaping the gravity well. An object as big and heavy as the Earth – which has a mass of around 6x1024 kilograms (13x1024 pounds) – holds on to objects on its surface with an iron grip. Even when birds or planes do make it into the sky, they soon have to return to the surface. What goes up really does usually come down.
Units and stuff
Occasionally we will be using scientific notation like the 6x1024 above. This is just a convenient way of representing large numbers. Here, 6x1024 is shorthand for ‘6 multiplied by 10, 24 times over’ – or to put it another way, 6 followed by 24 zeroes. You could also say that it’s 6 trillion trillion.
Science makes use of the metric system for all measurements, and, by the time theEndurance was commissioned, no one on Earth was still using the traditional units such as feet or pounds. They had gone the same way as rods, poles, perches, bushels and chains as units of measurement. However, for old times’ sake, we will show both metric and traditional ‘Imperial’ units, except for restricting weights to metric tonnes, as these are close enough to traditional tons to make the distinction unnecessary.
We are used to measuring long distances in kilometres or miles, but in space, a kilometre is a pathetically small unit. The most useful measure for us will be the light year – the distance that light travels through space in a year. A light year is 9.46 x 1012 kilometres or 5.88 x 1012 miles. To put that in context, the distance from the Earth to the Sun is about 8.3 light minutes or 0.000016 light years. Astronomers often prefer to use distance units called parsecs (which are around 3.26 light years). These work particularly well with the mechanics of telescopic observations, but we will stick to light years as they are easier to envisage.
Are you massive?
Because we are going to spend our time during the journey out in space, it’s worth quickly clearing up the distinction between mass and weight, because the difference matters very much when you are away from the surface of the Earth. These terms tend to be used interchangeably back home, but they are very different things, and in space this will become obvious.
Mass is an intrinsic property of an object, which is measured in kilograms (officially, the traditional mass unit is called a slug (14.59 kilograms), although the pound tends to be used more often). It doesn’t matter where an object is, it will always have the same mass, unless bits are removed from it or added to it. You could see mass (a concept introduced to the world by Isaac Newton back in 1687) as a measure of the amount of stuff in an object – whether that object is you, a starship or something as large as the Earth.
Weight, by contrast, is the force that is felt by an object under the gravitational pull of a body such as a planet. When we talk about the weight of something, we really mean ‘its weight when it is on the surface of the Earth’, though we tend to omit the last bit. Your weight would be totally different if you were on the surface of the Moon, for example – about a sixth of what it is on Earth. In space, your weight could be zero, though, as we will discover, it certainly doesn’t have to be, and it will
