Existing Absurd Technologies

When attempting to introduce non-rationalists to the ideas of cryonics or Strong AI, it appears that their primary objections tend to be rooted in the absurdity heuristic. They don’t believe they inhabit a universe where such weird technologies could actually work. To deal with this, I thought it would be useful to have a cache of examples of technologies that have actually been implemented that did, or ideally, still do, challenge our intuitions about the way the universe works.

The first example that comes to my mind is computers in general; imagine what Ernest Rutherford, let alone Benjamin Franklin, would have thought of a machine that uses electricity to calculate, and do those calculations so fast that they can express nearly anything as calculations. Nothing we know about how the universe works says it shouldn’t be possible, indeed it obviously is knowing what we do now, but imagine how weird this would have seemed back when we were just coming to grips with how electricity actually worked.

I suspect there may be better examples to challenge the intuitions of people who’ve grown up in an age where computers are commonplace though. So does anyone have any to volunteer?