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My rating: 4 of 5 stars

We get to know Jessie Lamb against the background of a slow apocalypse, one which despite the death knell it may be sounding for the human race allows people to get on with the trivia of their lives for the time being.

This sounds like a familiar concept but this is not the climate armageddon we’re sleepwalking into. Jessie has been born into a time where Maternal Death Syndrome (MDS) kills anyone who becomes pregnant long before they can give birth. Within a generation the human race will be extinct.

Jessie is an ordinary teenage with all this entails which makes for a compelling read. She is idealistic in the face of the way the world has been screwed up by the older generation. In a country where rival factions of varying degrees of sanity are springing up in response to the looming crisis, Jessie seems to keep her head and see things for how she believes they really are.

The only problem is that the one thing she feels she really can do to make a difference is the one her parents cannot countenance.

A thoughtful and melancholic read this is all the more effective for being set on such a small scale. Despite the world shaking events this is a story of a teenage girl in Manchester, her friends, her family. At the heart of the book is the fact that both Jessie and her parents are behaving in the only way they can. The fact that they want different things is unavoidable.

Children will always rebel and leave home, whatever form that rebellion takes.

Despite not being marketed as such - this novel was long listed for the Booker and won the Arthur C Clarke award - this feels very much like a YA novel (not a criticism).

The Testament of Jessie Lamb by Jane Rogers

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Time dilation when travelling at speeds approaching the speed of light is derived from what mathematically should happen given that the speed of light is a constant. As such, they start to sound nonsensical if the speed of the vehicle in the thought experiment in question approaches that of light - however these effects have been experimentally measured and as such are very real. Like quantum effects they are effectively undetectable and very counterintuitive in the real macro- and brady- worlds we are used to…

The usual analogy starts with throwing a ball along a train carriage.

If a train is travelling at 100mph and a ball is thrown along the carriage in the direction of travel at 5mph, then observed from a field beside the railway track the ball travels at 105mph, adding together the speeds of the train and the ball.

However if instead of a ball our experimenter switches a laser pointer on at one end of the carriage and shines it in the direction of travel, it’s a very different matter.

In classical physics you would expect that when observed from a field beside the railway track the photons in the beam of light from the laser would be measured to be travelling at the speed of light + the speed of the train.

But this is not so. Nothing can travel faster than the speed of light. To fix this discrepancy, we have to change the rate at which time passes inside the train.

From the outside it appears that the photons have to travel a greater distance than the length of the carriage because the carriage is moving. For the purpose of demonstration let’s say that the carriage is 9 metres long but that the distance the photons need to travel when the carriage is moving is 10 metres.

At a fixed speed it will take light a fixed amount of time to travel 10 metres. Lets call this 10 timebits.

However inside the train carriage, measured relative to the carriage interior, the length the beam of light has to travel is only 9 metres. At a fixed speed it will take light a fixed amount of time to travel 9 metres. Let’s call this 9 timebits.

However, viewed as a whole, the beginning and the end of the experiment are at the same points in time. Somehow people on board the train have only experienced 9 timebits whilst their colleagues observing from within the field have experienced 10.

Time on board the train has therefore slowed down.

The faster the vehicle is travelling, the slower time inside passes. At 0.9 of the speed of light it would take a starship approximately five years to travel to Alpha Centauri but only two and a half years would pass on board.

Travelling at the speed of light (which is considered impossible for a macroscopic object) time would stop on the ship and the crew would have no experiences. Time spent at c is non-existent which means that it would be impossible for a ship to function whilst travelling at c.

Travelling just below the speed of light means that in theory we could reach Alpha Centauri in what seemed to us like hours, but over four years would always have passed on Earth.

The whole concept of things “working” whilst at the speed of light is meaningless. The words “happening” and “working” imply the existence of a temporal axis which disappears at the speed of light.

Proof of time dilation online here.

Originally written as a comment on the Sulci Collective blog in January 2012.