Lesson 5.1 What is gravity?

What is gravity?

A natural phenomenon by which all things with mass are attracted to one another. It is the force of attraction between objects with mass. Gravitational forces are transmitted by gravity waves.

What was Aristotle's explanation for falling objects and why was it incorrect?

Aristotle (330 BCE) believed objects moved toward their "natural place" and heavier objects fell faster. This was disproved by Galileo in 1604 who showed acceleration due to gravity is independent of mass using balls rolling down inclines.

What were Kepler's and Newton's key contributions to understanding gravity?

Kepler (1609): Showed the Sun was at the centre of the solar system not Earth. Newton (1687): United Kepler's astronomy with Galileo's falling body laws and extended gravity to mean a force between ALL bodies with mass not just celestial objects.

How did Einstein's theory of gravity differ from Newton's?

Newton modelled gravity as a force between masses. Einstein's General Relativity (1915) described gravity as a distortion of "space-time" caused by massive objects. Einstein's theory could explain phenomena Newton's could not such as light bending around massive bodies.

What are gravitational waves and when were they detected?

Gravitational waves are ripples in space-time that transmit gravitational forces. They were predicted by Einstein's theory and first detected in 2015 by LIGO (Laser Interferometer Gravitational Wave Observatory) confirming Einstein's predictions.

Why is gravity described as an "attractive force only" and how does this differ from electrostatic and magnetic forces?

Gravity only attracts - masses always pull toward each other. Electrostatic forces can attract (opposite charges) OR repel (like charges). Magnetic forces can also attract or repel depending on pole orientation. Gravity has no repulsive equivalent.

Was gravity "invented" or "discovered" by Newton? Evaluate both claims.

Newton did not invent gravity - it existed before him. He discovered and mathematically described the relationship between mass distance and gravitational force. He unified existing observations into a coherent theory (Law of Universal Gravitation) allowing predictions and calculations