On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs." --San Antonio Express-News
Using computer models based on the Moon’s crater record, scientists have developed a simulation of the great early bombardment of the Earth around 4 billion years ago.
The model suggests that the biggest asteroids to hit Earth would have been as large as 3,000 kilometres across. Between one and four would have been 1,000 kilometres wide or larger, it predicts, with a total of three to seven exceeding 500 kilometres in width. The most recent of these would have hit around 4.2–4.3 billion years ago.
In comparison with Earth’s mass, the amount of rock hitting the planet would have been tiny. But it would have had an enormous effect on Earth’s surface, says Marchi. A 10-kilometre-wide asteroid was enough to kill the dinosaurs, and studies4 show that one 500 kilometres across would vaporize all of the planet’s oceans. “At 1,000 kilometres, the effects would be so wide the planet would probably be completely resurfaced with material from the mantle,” he says.
More here, including animated gifs showing this bombardment unfold.
We are now in the third week of my annual July fund-raiser for Behind the Black. My deep thanks to everyone who has so far donated or subscribed. The response this year has been wonderful.
We are not done yet. This monthly fund-raiser is now half over, and I am hoping the second half will result in as many donations as the first half did. If it does, I will remain free to continue my writing as I see fit, unblemished by the efforts of others to squelch my perspective in this increasingly intolerant world.
This year's fund-raising drive is also significant in that it celebrates the 10th anniversary of this website's founding. It is hard to believe, but I have been doing this for a full decade, during which I have written more than 22,000 posts, of which more than 1,000 were essays and almost 2,600 were evening pauses.
Therefore, I hope you will please consider donating to Behind the Black, by giving either a one-time contribution or a regular subscription, as outlined in the tip jar below. Your support will allow me to continue covering science and culture as I have for the past twenty years, independent and free from any outside influence.
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