They are massively distributed in space and time.

They are both human-made and non-human.

They are difficult to observe and have only recently impinged on human awareness.

They outscale us and/or outlast us in disturbing ways, disrupting our notions of “world,” “horizon” and “environment.”

For instance: Plutonium 239 has a half-life of 24 100 years. 7% of global warming effects will still be around 100 000 years from now.

I talk about them here and here. And I write about them here and here.

And Robert Jackson writes about them here. And here.