What If an Asteroid Bigger Than Mars Hit Earth?

You stand on a street in Chicago at night while rocks fall on it one after another, each ten times wider than the last. First comes a 1 cm pebble that burns out 40 km up, then a 10 cm stone that hits the road 5 m from you, then airbursts that set off every car alarm and blow in the shop windows. A 100 m rock flattens the street from downtown, a 1 km asteroid erases the city, and after that the rungs outgrow your street, then the planet, until the last one is a world wider than Mars, aimed straight at you. Every rock is stony (3,000 kg per cubic metre) and hits at 20 km/s on a 45-degree path, so each one carries 1,000 times the energy of the one before, from 75.1 g of TNT to 75.1 quadrillion megatons. Chelyabinsk's rock was about 20 m wide and burst 29.7 km up with about 500 kilotons; Tunguska was 10-15 megatons; Chicxulub's crater is about 180 km wide. Ceres is 939 km across and Mars 6,780 km. The entry, crater, fireball, heat, ejecta and blast numbers follow the Collins, Melosh & Marcus (2005) impact model, the small meteors fly through the U.S. Standard Atmosphere 1976, and run on Chelyabinsk the same model gives about 1.6 kPa under the burst, against 1.6-3.2 kPa measured in the city. What isn't real: the rocks arrive one after another on the same street, which is rebuilt between rungs, and long waits are squeezed into time-lapses (the 10 km rung's blast really takes 25.6 minutes to reach you). The biggest rungs are still shown from your street even where it would already be gone, and the falling rocks in space are drawn far larger and brighter than they would look so you can see them. Above 10,000 megatons the blast is halved, as Collins advise. The ocean-boiling and crust-melting figures are energy comparisons, not a climate model. The last world's hit-and-run, the ring and the young Moon are a simplified sketch of what giant-impact studies find. Ten steps from a grain you could lose in your palm to a hit that leaves a new Moon in the sky. 0:00 A pebble 0:33 A fist of rock 1:08 A boulder 1:43 Chelyabinsk class 2:28 Tunguska class 3:18 A 1 km asteroid 4:00 Chicxulub class 4:54 A 100 km asteroid 5:39 Bigger than Ceres 6:24 Wider than Mars 7:16 Where you stood 7:46 A new Moon #whatif #science #space #simulation