Finished reading the final book in Greg Egan’s “Orthogonal” trilogy this week.

There are spoilers here. If you actually intend to read it you might not wanna read the rest of this.

Egan is awesome, often jaw-droppingly so. Usually taking current physics understanding to it’s conclusions, setting his stories in the actual world as the best of our maths understands it.

Not so in the Orthogonal books though.

Here he flips one of the signs in physics so that a - becomes a +. Reverses the polarity, so to speak.

Which means that instead of there being 3 space dimensions and one of time, they’re even MORE mixed up than in our reality. Time doesn’t slow down as you go faster like in our universe, it speeds up. You head fast enough in the right direction, and you’re travelling in time.

His heroes are from a world that is doomed, with mere years to live, and nothing like the kind of technology needed to save it. But, in that orthogonal universe there’s a solution. You blast a space-ship so quickly in the right direction that time speeds up for them. They spend generations figuring out how to save the world, come back, then fix it.

The final book that I just finished deals with some of the consequences of inventing a machine that can tell the future. Actually accurately.

Do you want such a machine to exist? The inhabitants of the generation-ship charged with saving the world have differing opinions, and a democracy, and terrorism when things don’t go the minority’s way.

They invented the machine. It was a bad thing. He reckoned that if you can receive messages from future-you, telling you about all the ideas you are going to have, then that necessarily means you already have all the ideas you’re ever going to have.

Instant breakdown and halt to the progress of all science.

Ha!

Brilliant.

And then what do you do if your infallible messages from the future just STOP? Do you assume you’re going to be wiped out?

As usual, I enjoyed his equation-heavy story with liberal application of difficult-to-understand graphs of 4-dimentional topology slightly confusing but also enlightening. And very entertaining.

Hope he’ll be back to real physics for his next book though.