Check out these videos of Galileo’s infamous thought experiment in action.
Most people are taught about this experiment in school science lessons. Two objects, one heavier than the other, are connected by string and then dropped from a height. The assumption that heavier objects fall faster than lighter ones predicts the string should become tight as the heavier object tries to pull the lighter object downwards faster. Of course, the combined total weight is means the whole system should actually fall faster, leading to a contradiction. The assumption is proved false, meaning that heavy and light objects should fall at the same rate of acceleration, independent of their mass.
Trying the experiment on Earth, traditionally taking objects such as a bowling ball and feather for the obvious difference in mass, it appears that heavier objects fall faster than lighter ones. However, the shape and surface area of the feather means it encounters much more air resistance during the fall than the bowling ball, slowing its acceleration. To really see that objects accelerate independent of their mass, we need to perform the experiment in a vacuum (or near-vacuum where air resistance is negligible), as shown in the video below by Brian Cox in BBC 2’s Human Universe program.
Although the above video features an interesting way to demonstrate the experiment, and is deservedly doing the rounds on social media today, I still find the most beautiful and inspiring example to be taken from the last moon walk of the Apollo 15 mission, where Cmdr. David Scott simultaneously drops a feather and a hammer. Not only is it a nice demonstration of physics, the fact that people are walking on the moon is a great testament to the incredible achievements of scientists and engineers.
Makes me think: isn’t it about time already that we got ourselves to Mars?