Does the toddler winging his way across the grass need to know velocities? Does the 10-year old pumping the merri-go-round for his friend need to calculate the torque? Science is entirely irrelevant to learning about the natural world (there's a reason why it's reserved for schooling years).
They don't need to be able to do the calculations or know the terminology, but knowing something about the way the world works is a prerequisite for living in it, IMO.
I remember the most fascinating scientific experiment I ever witnessed: I was out in the garden with a friend's two-year-old son. He had a small flower that he had picked from the lawn. He proceeded to go over to the patio table, sit underneath, and push the flower through the hole in the middle of the table.
Then, he got me to lift him up so he could see. To his delight, the flower had passed through the hole and was sitting on the table. He grabbed the flower, had me put him down, sat under the table and repeated the experiment several times (getting me to hold him up each time).
After a while, he stopped. I could see him thinking. Eventually, he came over to me and had me hold him up so he could drop the flower in from the top. I put him down and he rushed under the table to see whether the flower was there. It was - he was ecstatically happy.
Without realizing it, Alex had engaged in science: he had made repeated observations (i.e. seeing that a flower can pass through a hole upward), and based on them, he came up with a prediction (i.e. that a flower can pass through a hole downward, too) and tested it.
Admittedly, testing how a hole works is a bit more basic than what we usually think of when we say "science", but it's definitely within science's scope.
Kids do this constantly. Usually not as systematically as Alex, but they're always coming up with predictions about the way the world works and testing them. That's science.