Galileo in 15th century, discovered that any object falling to earth, fall at the same time .

He mentioned that a cannonball and a feather, if dropped from the same height will touch the ground at the same time provided there is no air resistance.

He had difficulty explaining it for quite a long time .
4 centuries later with the current Technology it has been experimentally demonstrated.

Its a super visual treat to watch the video
Please show it to your children and those who will be interested.