If Stephen Hawking time-traveled to whisper his final warning to Albert Einstein, the 20th-century genius would probably not have had a clue what the 21st-century physicist was talking about. Expectations can change with new information. After the Chelyabinsk asteroid hit Russia in 2013 — a little over a century after a larger impact struck Tunguska — it reopened the question of how often the earth was actually struck by such nuclear bomb-class objects. Chelyabinsk exceeded 470 kilotons of TNT and Tunguska had an estimated energy of 3 to 5 megatons.
Until recently, nobody knew the frequency. The earth is so large and until recently so sparsely populated that asteroids of this size may have been falling for some time, especially at sea, every few decades without being recorded. Only in the first decade of the 21st century did people start collecting hard data for purposes of Planetary Defense. What the B612 Foundation, a U.S.-based non-profit made up of former astronauts and scientists found was the threat relative to our tracking capability means we will likely never see one coming.
Chelyabinsk changed our perception of what the asteroid problem was. Those who feel humanity should make a multi-decade $93 trillion commitment to a Green New Deal a top priority should ask themselves how our threat perceptions would change if one Tunguska-class object strikes near a major city sometime this century. Just how quickly priorities can shift is shown by the rise and fall of China's One Child Policy.
https://pjmedia.com/richardfernandez/that-vision-thing/
Until recently, nobody knew the frequency. The earth is so large and until recently so sparsely populated that asteroids of this size may have been falling for some time, especially at sea, every few decades without being recorded. Only in the first decade of the 21st century did people start collecting hard data for purposes of Planetary Defense. What the B612 Foundation, a U.S.-based non-profit made up of former astronauts and scientists found was the threat relative to our tracking capability means we will likely never see one coming.
Chelyabinsk changed our perception of what the asteroid problem was. Those who feel humanity should make a multi-decade $93 trillion commitment to a Green New Deal a top priority should ask themselves how our threat perceptions would change if one Tunguska-class object strikes near a major city sometime this century. Just how quickly priorities can shift is shown by the rise and fall of China's One Child Policy.
https://pjmedia.com/richardfernandez/that-vision-thing/