Why is it Hot Underground?

The video discusses Lord Kelvin's theory that Earth started hot and has been cooling like a baked potato. Kelvin attempted to calculate Earth's age using temperature measurements, but his estimate was incorrect due to a lack of knowledge about radioactivity. The video explains that Earth's mantle is not rigid, allowing heat to spread through convection currents, which Kelvin did not account for. This process helps distribute heat from the core to the crust, influencing geological phenomena like volcanoes and plate tectonics.

Explain how heat from radioactive decay affects the Earth's temperature.

Describe the process of convection currents in the Earth's mantle.