(somewhat off-topic, for a smile in these dark times)
What would happen if a neutron star the size of the moon smacked into the earth at the speed of light?
Inputs:
Projectile Diameter: 10000 km
Projectile Density: 80000 kg/m3 (iron x 10, probably an underestimate)
Impact Velocity: 300000.00 km/s
Impact Angle: 45 degrees
Output:
Energy: 1.88 x 1042 Joules = 4.50 x 1026 MegaTons TNT
Transient Crater Diameter: 2.9 million km
Final Crater Diameter: 20 million km
We might not make it.
http://www.lpl.arizona.edu/impacteffects/