physics's history...
" Galilean relativity states that the laws of motion are the same in all inertial frames. Galileo Galilei first described this principle in 1632 in his Dialogue Concerning the Two Chief World Systems using the example of a ship travelling at constant velocity, without rocking, on a smooth sea; any observer doing experiments below the deck would not be able to tell whether the ship was moving or "

Ok ok Galileo told it is impossible?
I found nice problem

physics's history...
"please confirm below facts in book

We are able use pressure and solve famous boat problem
Tensions inside rope it is pressure inside rope!!!

Ok please measure tension inside
Each arm!!!
Mass m is is moving or boat M is moving?

How big tension feel that rope??
Tension is relative?

Please ask yourself about atom
Relation electron - - - - center