Secrets of the cosmos: the answers to all the biggest questions in the universe

How are stars made? Where did life begin? How do you relieve yourself in space?

1) How to make a star

At the Culham Science Centre in Oxfordshire they make stars every day – one every 15 minutes, when everything is going to plan. Star-makers on Earth generally use two heavy forms of hydrogen called deuterium and tritium. On Earth, they need hydrogen plasma. We are used to seeing, say, water as either a solid (ice), a liquid (water) or a gas (steam). But there is also a fourth state of matter – plasma. It forms under extreme conditions, such as those that occur inside a bolt of lightning, or inside stars. At millions of degrees, atoms are stripped of their electrons and separate into a sort of electrically charged cloud.

Magnets can be used to manipulate this electrically charged plasma. The Culham star-making machine squeezes it tightly into a sort of magnetic bottle. As the power is cranked up, and the plasma squeezed more tightly, it eventually does a remarkable thing: it ignites as a tiny star. The intense glow doesn't last long. Scientists film it in ultra-slow motion to see how it starts and, more importantly, why it breaks down after such a short time.

In the fiery furnace, hydrogen succumbs to the heat and pressure, and some of the hydrogen nuclei fuse to make a new element, helium. The energy that is released should, in theory, help to raise the temperature and keep the reaction going – something the Sun and the other stars manage to do for billions of years. At Culham, they are still working on it. But, with the turning of one element into another, the process that happens in stars has begun. In the lab, the nuclear fusion goes no further but, in stars, more and more fusion takes place, making heavier and heavier elements, all the way up to iron.

2) We're all being stretched, all the time

Although Isaac Newton's famous work told us what gravity does, he did not explain what it is. Particularly bothering was the implication that gravity acted instantly: if you could somehow conjure a second Sun in the sky, in Newton's world, the Earth would feel its pull immediately. But Albert Einstein didn't like the idea of something acting instantly at a distance, and instead thought of gravity as acting locally on space. He imagined massive objects making a "dent" in space into which others could fall. Although the "dent" would be deepest close to the object, it would reach across the universe so that Earth would be attracted even by distant stars. If a new large object were created, or an existing one moved, Einstein predicted, it would create ripples across the universe, travelling at the speed of light.

Unfortunately, he also predicted that, by the time they reached us, these ripples – called gravitational waves – would be far too faint to detect. Rather than a prediction of failure, some people have taken this as a challenge.

The site of the European Gravitational Observatory (EGO) near Pisa in Italy is a contrast to those selected for optical telescopes. It is on a flat plain, rather than a mountain; in a frequently cloudy area, and close to a town. The main requirement was to find a patch of flat ground measuring 1.8 miles square, because the Virgo detector is huge. The principle of detecting gravitational waves is very simple. As they pass through Earth, the waves slightly change the length of everything. Imagine a football pitch. As a gravitational wave goes through it is stretched first one way, so it gets shorter and fatter; then the other, so it gets longer and thinner, before returning to its original shape. So gravitational-wave detectors have two arms at right angles, with sensitive equipment measuring the length of the arms. If this sounds simple, it isn't. The expected change in length of each of the 1.8-mile arms will be the same as one-thousandth the diameter of a hydrogen atom's nucleus.

3) The zero-gravity lavatory

In the early days of space flight astronauts wore nappies ("intimate contact devices" in Nasa's euphemism), but these were not acceptable for flights of longer than a few hours. For Skylab there was a new system of waste management – the Waste Collection System (WCS) with a modesty curtain to shield the user from view. The WCS comprised a cylinder about 50in high and 12in across, like an old-fashioned spin dryer. From the front came a flexible plastic hose, as from a vacuum cleaner. This urine collector was intended for both men and women, and was fitted with a triangular rubber nozzle on the end. Unfortunately the sexes have different peeing systems, and as a result the nozzle never fitted anyone very well. What's more, the vacuum was never much good, so the nozzle was always a bit wet from the last user.

The alternative involved taking your trousers down and sitting on top of the cylinder, with your feet in stirrups, and then pulling a pair of spring-loaded restraints over your thighs. Remember, you were weightless, and you would not want to float off in the middle of the operation. Then you opened the sliding lid and...

Next problem: zero gravity. The seat was fitted with 11 channels to blow air upwards from all around so as to cause faeces to fall. Unfortunately, the air was icy cold. Once inside the cylinder, the matter was spun to the outside and freeze-dried to keep it out of the way.

At least one astronaut ate nothing at all for an entire mission in order to avoid having to use the WCS. But, sadly, this stratagem does not work. The body produces solid waste even when it receives no food.

4) Gravitational wobble

When a massive planet, such as Jupiter, orbits the Sun it exerts a gravitational pull on the Sun, which by Newton's third law (action and reaction are equal and opposite) must be the same as the pull needed to keep Jupiter in orbit. This means that Jupiter does not revolve around a stationary Sun; rather the pair of them actually revolve around a common centre of gravity. Because the Sun is a thousand times more massive than Jupiter, this centre of gravity is below the surface of the Sun, but it is still well away from the Sun's core, and as Jupiter swings round to the "east" the Sun will be swinging "west" to balance the pair.

5) Did life come from outer space?

The idea that life might have started all over the universe by seeding from space is called panspermia. In 1996 a meteorite from Mars was found to contain what appeared to be fossilised bacteria. According to the idea of panspermia, biological seeding from space not only kick-started life on Earth, but continues, and may be responsible for some of our diseases and infections.

We now know that, even in the emptiness of space, there are many kinds of molecules floating about, and some of them are complex organic compounds. Organic compounds have also been found inside meteorites – chunks of metal and rock that fall to Earth.

Where did those organic compounds come from? One wild theory is they were left behind, either by mistake or on purpose, by alien creatures touring through the galaxy. Another possibility is that they were formed naturally from simple molecules under the influence of ultraviolet light from the Sun – and, presumably, from other stars, too.

If organic compounds are drifting about in "empty" space, then they might have floated down through our atmosphere – or fallen inside a meteorite – and started reacting in ponds and shallow seas when conditions were favourable. Alternatively, they could have been part of the original cloud of dust that was pulled together to create Earth 4,500 million years ago. In that case they must have survived millions of years of Earth's turbulent early history before the climate settled down into a favourable state.

Various fragments of evidence support the idea that living things could migrate through space: high-altitude balloons have detected bacteria 20-25 miles above Earth's surface, in concentrations apparently increasing with altitude, suggesting that the bacteria either came from space or that bacteria from Earth could drift into space. Also, sudden showers of red rain in the Indian state of Kerala in late summer 2001 contained red material that was originally thought to be dust, but appeared under electron microscopes to be living cells. Some scientists thought these were simple algal spores, but others claimed they contained no DNA, and must therefore be some form of extraterrestrial life.

The idea that bacteria could survive the vacuum of space may seem absurd, but in 1967 the unmanned American probe Surveyor 3 landed a television camera on the Moon; it was retrieved in 1969 by Apollo 12, and when examined was found to contain a little colony of a bacterium called Streptococcus mitis. These had survived on the Moon, in a vacuum and with extreme monthly temperature changes, for 31 months. So perhaps bacterial life could indeed have come from outer space.

6) Stars can create their own telescopes

In his famous paper on general relativity, Albert Einstein said that gravity does not really make two masses attract one another; instead it distorts space in such a way that the two are pulled together. One consequence of this is that a massive star distorts the space around it.

So the space around the star acts as a lens, attracting light rays towards its centre, and thus magnifying the image of a distant object on the far side. This happens when, by chance, a star passes in front of a distant planet, which then flashes bright for between a few minutes and an hour or so.

Using this method, a planet called OGLE-2005-BLG-390Lb was found on 25 January 2005; it orbits a red dwarf 21,500 light years away. It seems to have a mass only 5.5 times that of Earth, and is nearly three times as far from its own star as we are from the Sun.

The Cosmos: A Beginners Guide by Adam Hart-Davis, is published by BBC Books, an Ebury Publishing imprint. © Adam Hart-Davis and Paul Bader. To buy a copy at the special price of £13.50, including P&P, call Independent Books Direct on 08700 798897 or go to www.independentbooksdirect.co.uk