“So, you have a choice. We’ve ten minutes of class left. I can either finish early, or…. I can show you that there’s actually a wormhole living in this picture, or can I tell you about Hawking radiation.”
That was the choice I presented the students with after we’d spent some time together exploring the Kruskal-Szekeres extension the the basic black hole solution, in my General Relativity class today. You probably don’t know what all that is, and that’s ok. Suffice to say that you end up with a pretty diagram which looks like two everlasting black holes put together as in a sort of elegant trading card. Or perhaps a neat knot where one black hole is sort of upside down and neatly slots into the other one so that they hug each other into eternity, acting as each others’ past and future. Look it up and see.
Anyway, they went for the wormhole, with a chant “Worm-Hole! Worm-Hole!”. So I constructed the wormhole for them… the Einstein-Rosen bridge, as it is known, ending with the sad news that it is not a real traversable wormhole that you can fly a spaceship through since it would require you to fly faster than light, which does not work… (and which, in part, would sort of defeat the purpose of having one in the first place). Boo. But then on an up note I talked a bit about why new research ideas (in the quantum gravity context) have brought them back into focus in research again and why the suggestion EPR=ER is sort of funny. See here for more.
They seemed to like their choice.
Anyway, I’m ending my long day by telling you about it and by doing a quick rough sketch (above) of the wormhole (as what’s called an embedding diagram) ot test out a nice new drawing tool I’ve added to my collection. Seems to work nicely.