If all humans died, when would the last light go out?

When Would the Last Light Go Out?

Most lights would fail shortly after humans disappear due to power grid failures. Fossil fuel plants need a constant fuel supply and would shut down quickly. Nuclear reactors can run in low-power mode indefinitely but will shut down without human oversight. Diesel generators in remote areas could last days to months until fuel runs out.

Off-grid geothermal plants can operate for a few years but will eventually corrode. Wind turbines can generate power for decades without maintenance but will fail due to gearbox issues. Hydroelectric generators can run on autopilot for years, but the power grid's failure means no electricity distribution.

Battery-powered lights will turn off within a few dozen years due to self-discharge. Solar power sources can last longer, providing illumination for extended periods if well-maintained. Solar panels can last a century if kept clean and have robust electronics. Solar-powered lights in remote areas could be the last human light source.

Spent nuclear fuel can emit light due to Cherenkov radiation. Radioactive materials can produce light when particles travel through substances like water or glass. Cesium-137 glows blue when mixed with glass and can emit light for centuries.

Centuries from now, deep in concrete vaults, the light from our most toxic waste will still be shining.

Power Grids and Alternative Energy Sources

Fossil fuel plants would be the first to fail. They need a constant fuel supply, and "their supply chains do involve people doing things." Without humans, these plants would shut down within hours, causing a cascading failure across the power grids.

Nuclear reactors, despite having enough fuel to run indefinitely, wouldn't last long either. "The core would go into automatic shutdown" as soon as something went wrong, most likely due to the power grid failure.

Diesel generators, often used in remote areas, could keep running for "anywhere from days to months" until their fuel tanks run dry. Geothermal plants would fare better, potentially running for a few years, but "they'd all succumb to corrosion eventually" without regular maintenance.

Wind turbines, designed to operate with minimal servicing, could last even longer. Some "are typically rated to run for 3 years without servicing," and a few might continue generating power for decades. However, eventually, their gearboxes would seize up.

Hydroelectric generators, like those at the Hoover Dam, could "continue to run on autopilot for several years." But without a functioning power grid, the electricity they generate would have nowhere to go, and mechanical failures would eventually stop them.

Solar Panels and Nuclear Waste

Solar panels could last for a long time, especially in dry places with occasional rain or breezes to keep them clean. If the electronics are well-built and the panels are kept free of dust, they could continue providing power for up to a century. However, the wires and circuits would eventually corrode.

But there's another, stranger contender for the last light source: spent nuclear fuel. Radioactivity itself isn't visible, but when radioactive particles travel through materials like water or glass, they can emit light through a phenomenon called Cherenkov radiation. This is the blue glow seen in nuclear reactor cores.

Some radioactive waste, like cesium-137, is mixed with glass and stored in solid blocks. These blocks glow blue in the dark due to Cherenkov radiation. Cesium-137 has a half-life of 30 years, meaning that even two centuries later, the blocks will still glow, though with only 1% of their original radioactivity. The light will fade over time, but the blue color will remain.

In the end, centuries from now, deep in concrete vaults, the light from our most toxic waste will still be shining.

Conclusion

Solar-powered lights in remote areas could be the last human light source, with some radioactive materials glowing for extended periods.