In one of the seminal works of Isaac Newton, he showed that the acceleration due to gravity is the same on all objects falling in a gravitational field irrespective of their mass. 

In English - irrespective of the weight of the object, the rate at which an object falls to Earth when dropped from a height is the same. 

Here is the video of astronauts conducting the experiment on the moon to demonstrate this.

 But.. and there is always a but…

If you went to the top of the Empire State Building and dropped a feather and a bowling ball, intuition will tell you that both of them are not going to hit the ground at the same time. In all likelihood, your brain will tell you that the feather would fall more slowly. In reality, the feather would probably fly up as the ball hurtles down because tall buildings create an upward draft of air, which would be powerful enough to push the feather up but not the ball. It may slow down the ball a little.

The theory that Newton posits and most of science for that matter is reductionist. 

Scientists find it hard to create theories if they must take all of the various interactions into consideration. But the interactions do not disappear just because you choose not to take them into consideration. The feather will not fall at the same speed as the ball.

Sure, it may on the moon, but we are not living on the moon.

This kind of reductionism delivers us the climate catastrophe that we are dealing with. When you choose to ignore the interacting pieces and behave as if there is only one phenomenon at work, you tend to create consequences that you are not prepared to deal with.