It was an amazing discovery. The scientists were looking at soil from the Siberian permafrostAny ground that remains completely frozen for at least two years. Permafrost covers large regions of the Earth. . In it were two little roundworms - and when the soil thawedMelted after being frozen. , they came back to life.

The scientists then set about finding out how old the soil was. Using carbon datingA method of finding out how old an object is by examining the carbon inside it. , they arrived at the answer: 46,000 years.

For believers in cryonicsThe practice of freezing the bodies of people who have just died in the hope that future medical treatments will be able to save them. , this was hugely encouraging. If worms could be preserved for so long and then revived, surely humans could too.

But cryonics is far from simple. The process has to begin within 15 minutes of the heart stopping.

First the body is packed in ice and injected with chemicals to stop the blood from clotting. Then it is cooled to just above OC. Next, the blood is replaced with a solution to preserve the organs.

Another solution is injected to stop ice crystals forming. Then the body is cooled to -130C. Finally, it is stored in a tank of liquid nitrogen at -196C.

The idea is to keep it there until a cure is found for whatever the person died from - and also any damage done by the freezing process.

But there is a hot debate around cryonics. Writing in MIT Technology Review, Professor Michael Hendrick calls its promises "snake oilA term used to describe a product which claims to help your health, but for which there is no evidence. It roughly means "a scam". ".

Every brain is so complicated and so different, he explains, that getting one working again would be incredibly difficult.

Even if scientists succeeded, the person brought back to life might not actually be you. It might just be someone who thinks like you.

But some people who work on cryonics claim they are being treated unfairly.

"For scientists who would like to discuss it open-mindedly, it tends to significantly hurt their career," says one of them, Dr Ramon Risco.¹ He adds that it can even get them kicked out of scientific societies.

He believes that there are people who are afraid of what scientists like him might discover.  

Yes: Science has made advances in recent decades that earlier generations could not have dreamed of. Now that the cryonics process is established there is every chance that problems will be ironed out.

No: There is no evidence whatsoever that cryonics could work. Organs like the heart have never been successfully frozen and thawed. It is even less likely a whole body could be without serious damage.

Or... Even if people could be brought back to life, it would be a terrible experience. They would find themselves in a completely unfamiliar world without friends or family to support them.