The tail of a comet is primarily caused by
A) radiation pressure.
B) electromagnetic induction.
C) Coulomb repulsion.
D) eddy currents.
E) nuclear magnetism.
Question 2
Approximately how soon might we expect an immediate response from a civilization that received the signal we sent to the globular cluster M13 (21,000 light-years away) in 1974?
A) 84,000 years
B) 21,000 years
C) 10,500 years
D) 42,000 years