2.4 Physics Journal: Galileo Galilei: 16th-Century "New Scientist"

16th century scientist, Galileo Galilei challenged ancient philosophers teaching by doing experiments to test their theories, a radical new way to do science. 

• radical: complete, total, basic

He did an experiment where spheres roll down a ramp, disproving Aristotle's theory that things fall at constant speeds, but bigger things fall faster. Showing that an object's object in free fall doesn't rely on its mass.

Introduction

Early 1500s - "science" was dictated according to a ancient philosophers small group with teaching deemed as foolish and a threat to the "established order". 

1564 - Galileo was born near Pisa, Italy, very bright and ambition man who was supported by authorities. 

Aristotle thought that 2 kind of motions exist for inanimate matter: "natural" and "unnatural." 

• Natural motion, without acceleration, occurs when objects seek natural place. 

• Unnatural motion, when force is applied onto objects. 

Accordingly, a stone falls (natural motion) until it reaches its natural place on Earth and claimed that that bigger object fall faster.

1500s - was fatal to challenge his ideas and takes courage to do. 

It's said that Galileo began to question his views on falling object by seeing a hailstorm, seeing that big hailstones struck the ground at the same of smaller ones. If Aristotle was right, this only occur if big hailstones were created higher in the atosphere than smaller ones. Galileo found this hard to believe. A more reasonable explanatino was the stones wre all created at same heights and fall at same rates, regardless of mass, leading Galileo to attempt Aristotle's teachings.

Galileo's legendary experiment 

Galileo dropped a cannonball and a less big musketball from the top of the Tower of Pisa. Both ball struck the ground simultaneously. He may have never did this himself but an akin experiemnt had already been published by Benedetti Giambattista - 1553. 1971 - astronaut David Scott did this on the moon with a hammer and father by same heigh both struck ground simulltaenously. 1638 Galileo published a book "Discourses and Math Demonstrations Relating to Two New Sciences", talking about falling bodies and projectile motion which are keys of kinematics, by math reasonings and experimental observation to explain object's behaviors. 

This was a new way to do science. Phisolophers, like Aristotle and Plato relied on pure reasons and logic to make theories. Galileo's book coincied the start of a modern Science era where the world is based on experimental proof, not authority positions.

Do falling objects accelerate?

To prove that falling objects accelerated, he hypothesized, “We may picture to our mind a motion as uniformly and continuously accelerated when any equal intervals of time whatever, equal increments of speed are given to it.” Proving this was hard as the technology back then was basic. 

Galileo knew that free-falling objects increase speed too quickly to be measured accurately.

So he studied how balls rolled down inclined planes (ramps). In Two New Sciences, he concluded that: After the operation and assured its reliability, we now rolled the ball only 1/4 the the channel's length; and measured its descent's time, it's precisely 1/2 of the former. Next we tried other distances, compared the time for the whole length with that for the half, or with that for 2/3, or 3/4, or for any fraction; in such experiments, repeated a hundred times, it's always found that spaces traversed were to each other as the squares of the times like for all the plane's inclinations, i.e., of the channel, with which we rolled the ball. 

If the ball travelled at constant speed, the distance travelled would be directly proportional to time measured. 

• proportional: corresponding