Email feels weightless. You type a few lines, hit send, and the message vanishes into thin air. Nothing is printed, nothing is shipped, nothing is thrown away. It is easy to assume the whole thing costs the planet nothing at all.

It doesn't. Behind that weightless feeling sits a very physical machine: the device in your hand, the wireless and fibre networks that carry the message, and the data centres that route, process, and store it, often for years.