Ethan is a nerd, to put it bluntly. His hero is Stephen Hawking and his pet rabbit is called Quark.

Ethan is more interested in physics, specifically astronomy, than anything else, and accepts that the other boys at school don’t like him.

His friend Will is okay, but seems to have gone off him. Will is making friends with the other boys, and it seems the only way he’s going to be accepted by them is if he publicly distances himself from Ethan.

“Ethan’s such a freak, even his dad left him right after he was born,” Will blurts out. Ethan is aghast: that was a secret Will had promised never to share.

And then Ethan hits him, giving him a black eye and knocking out a tooth. Now Ethan is in big trouble.

Ethan has never known his dad. His mom, Claire, a former ballerina, brought him up in Sydney alone. She is protective and yet tolerant of his curious interests, but when it comes to his dad she is uncharacteristically unforthcoming.

Ethan would really like to know him –he’s a theoretical physicist and Ethan is sure they would have a lot in common.

But what Ethan doesn’t know is that when Ethan was just months old, his father was jailed after being found guilty of shaking him so hard that he almost died. The baby had needed surgery because he bled into his brain, and there were fears he would never be normal.

Although Mark denied harming his son, the conviction carried. Claire herself was riven by guilt – she had been away on a dancing audition, but maybe if she had not put her career first, Ethan would not have been hurt.

Then, when Ethan is 12, Mark’s elderly father begins to fail, and Mark, now out of prison, returns to Sydney to see him. The old man has granddaughters, but has never met his grandson. Can he meet Ethan before he dies?

Mark contacts Claire but she wants nothing to do with him. He writes her a letter and slips it under her door – where it is found by a curious Ethan. Mark has left a telephone number, and Ethan phones him.

A chain of events begins to unravel explosively, turning the lives of Mark, Claire and Ethan upside down.

The novel opens with Ethan and Claire in a park at 2am, lying on their backs and waiting, with some reluctance on Claire’s part, for a meteor shower.

Ethan tells her that in about two billion years Andromeda will be so close to the Milky Way that the galaxies will spin closer and then spectacularly collide.

He asks: “Mum, do you ever think about the future?”

Chilly and bored she answers: “Right now I’m thinking about what we’re going to have to eat for dinner tomorrow night.”

I was a single parent with a boy like Ethan, and that was the sort of frustrating answer I tended to give. I loved this book; my boy’s grown up now, but I suspect he might find stuff in here to identify with.

Desperate, compassionate and often funny, this is a great read.

* Relativity by Antonia Hayes is published by Corsair