As long as there’s someone or something trying to sleep there will be a blue LED shining directly into their eye.
Do satellites count? Seems like there could be a solar panel connected to a blinky thing up there that might outlast Cesium.
Depends, a lot of satellites are close enough to Earth that there’s still barely enough atmosphere to cause drag and deorbit the satellites given enough time, and they all need some flavor of orbital maintenance. Although there are the various probes we’ve sent out and the rovers too, possibly with some flavor of blinky light on them.
I’m really hoping the answer ends up being one of the Voyagers somehow. That would just be poetic.
Tdlw: Cherenkov radiation from buried nuclear waste will still glow a faint blue light for a couple of centuries.
Power grid within days. Batteries and renewables for a few years until parts break down.
Oh about 7 or 8 billion years
