The Earth of the past, and a mass extinction event killing off nine of every 10 species living on our planet 250 million years ago, were at the heart of the latest episode of Fox's "Cosmos: A Spacetime Odyssey."

The episode "The Lost Worlds of Planet Earth" was a biography of the Earth as expressed in its continents, oceans and life living on and in them, host Neil deGrasse Tyson explained, saying "the past is another planet."

In a world where wildly different plant and animals lived in an atmosphere significantly different to today's, under night skies filled with constellations that would be unrecognizable to modern humans, giant insects like dragonflies as large as eagles roamed in what is known as the Permian period.

Creatures grew outsized in an atmosphere much richer in oxygen -- until all that changed when volcanoes covering much of modern Siberia began a long period of eruptions that loaded the atmosphere with the greenhouse gases methane and carbon dioxide while flooding much of the Earth's surface with molten lava.

The changes were so drastic -- and so rapid -- that few species managed to evolve quickly enough to successfully adapt to a period now dubbed the Great Dying.

It was also began a period of continental drift, a phenomenon now so completely understood and agreed to its difficult to remember that those who first conceived the theory were considered scientific pariahs.

Geologist Alfred Wegener proposed his hypothesis in 1912 that the continents had once been a part of a single "supercontinent" land mass and have been splitting and wandering over the Earth ever since.

For that he was ridiculed and almost hounded out of the field.

The subsequent acceptance of the theory was largely down to another geologist, Marie Tharp, whose work on mapping ocean floor topology led her to discover a mountain range on the floor of the Atlantic, now called the Mid-Atlantic Ridge, where the surface of the Earth was indeed splitting apart and moving the continents slowly away from each other.

Tharp, voiced in the episode's animated sequences by actress Amanda Seyfried, was cautioned about throwing in with the "crazy" and discredited Wegener, but stuck to her guns until the theory of continental drift and plate tectonics was supported by so much evidence it could no longer be denied.

The motion has never stopped and the Earth is still moving, Tyson pointed out; it's just that our lifespans are too short to see the dance of the continents playing out over millions, even billions of years.

And as the familiar continents of today continue their stately march across the globe, the Earth of the far future will not match the look of our current home, he said.

In other words, he said, "Our future is also another planet."

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