Earth (Foundation Universe) - Radioactivity and Fading Memories

Radioactivity and Fading Memories

• In The Stars Like Dust, the Earth is radioactive, apparently from a war. No one doubts its status as the planet of origin: indeed the exact order of settlement is remembered on Rhodia.
• In The Currents of Space, thousands of years later, and not far from the start of the Trantorian Empire, Earth's progenitor-status and legacy is no longer remembered by most of the galaxy.
• In Pebble In The Sky, the status of Earth is even more uncertain. Some experts believe that humans originated separately on many worlds.
• In Foundation, 12,000 years later during the fall of the Galactic Empire, "Sol" is just one among several candidates for the original home of humanity.

But why is Earth radioactive? In the Afterword to "Grow Old Along With Me" in The Alternate Asimovs, Asimov explains:

I gave the Earth of the future a radioactive crust, at least in spots, yet it had a remnant of life and humanity clinging to it. Clearly, I meant this to be taken by the reader as the result of a nuclear war in our future; and the story's past... It is of crucial importance to the plot.

This was retained when "Grow Old Along With Me" became Pebble In The Sky, published in 1950. When Asimov returned to his future history with Foundation's Edge (1982), he no longer thought a nuclear war could make the crust radioactive without destroying all life. Instead, he assumed that the crust of the planet was deliberately made increasingly radioactive.

In Robots and Empire, he establishes how the Earth was deliberately made radioactive, by a Levular Mandamus, a Spacer attempting to cripple Earthborn and Settler attempts at colonization. Instead, the net result, as is hinted in various books, is that the Settlers, unattached to their "holy" homeworld of Earth, are further driven to colonize and thus go on to establish the Galactic Empire, all but crowding Spacer culture out of the Galaxy.