3rd Law
It is now time to state Newton’s 3rd law properly.
For every action force, there is a reaction force that is equal in magnitude but opposite in direction.
In Newton’s words, when you push on a stone, the stone pushes equally back on your finger.
It is possible to show the third law more accurately. Set up a situation where two people pull on the same spring scale, their scales will always agree.
What if you ask your partner to pull with 20N and you only pull with 10 N. This is impossible to achieve, but the result will be that they will move in the direction of the person pulling harder.
Newton did discuss the tides and the motions of the planets, especially Jupiter, how it would perturb the sun, causing it to wobble. But he did not know about Pluto, which is a great way to illustrate the third law in terms of gravitation.
There is also Newton’s own example, the cart and the horse. In the Principia, Isaac Newton discussed how his 3rd Law can best be understood in the context of a horse pulling on a cart. Paul Hewitt immortalized this example still further by using it as the basis of a cartoon in his masterpiece book called Conceptual Physics.