Preventing Asteroids Hitting Earth
For today's Isaac Arthur YouTube channel viewing I watched his video about defending Earth from asteroid strikes. Little grain-sized rocks strike Earth's atmosphere and almost instantly burn up frequently due to Earth's gravity well. Other larger asteroids such as the one hypothesized to have ended the reign of dinosaurs on Earth are less frequent but statistically will happen again someday. The best defense is early enough detection and the tools to avert the asteroid smashing into Earth.
Passive detection of asteroids involves trying to spot asteroids whose surface reflects light from the sun. Many images of the sky can be taken and computers can analyze the images to detect possible asteroids.
As the video points out changing an asteroid's velocity one meter per second for 70 days is equal to the Earth's radius; thus causing any asteroid to miss the Earth. The video covers several technical issues why using nuclear weapons to deal with an incoming asteroid doesn't work like it is portrayed in movies. One method covered that I find fascinating is using high power laser beams to vaporize part of the asteroid's surface and that evaporation would act as propellant to nudge the asteroid into a different path avoiding Earth. Hopefully as more technology develops and going into space becomes more common asteroids might be manipulated into more desirable orbits or Lagrange points for mining.