why is it a ship sailing in a straight line at a fixed velocity creates waves on the shore, but dc current with a fixed value cannot create an EM wave?

Question

why is it a ship sailing in a straight line at a fixed velocity creates waves on the shore, but dc current with a fixed value cannot create an EM wave?

In: Physics

Answer 1

I would say the ship is like a rising edge, like turning on a DC supply. Would a long pipe sliding through the water make a wave?