I hear a lot about the “theory” of evolution or the “theory” of global climate change. Well, gravity is also a “theory” we really don’t understand how one object can attract another without a strong magnetic or electrical field to pull them together. The most sophisticated measurements of Earth’s gravity are recorded indirectly, by measuring the distance between two satellites as they orbit the Earth. GRACE. It gives us very precise measurements, but it measures distance, not gravity. We infer the strength of the local gravity field instead of measuring it.
We can directly measure temperature because we’ve discovered materials that change their properties as the temperature changes. Gravity affects everything equally, and isn’t affected by material properties. A hammer reacts the same to a gravity field as a feather. Apollo 15 Galileo experiment. The theory of gravity is very solid. We got our spaceships and astronauts back after shooting them into space, which means we’re on the right track. The implications of understanding gravity are enormous. Once we understood temperature, we gained an amount of control over it. Being able to control gravity fields would revolutionize space travel. Instead of powering our launch vehicles with large, heavy, chemical rockets, we could negate gravity around the vehicle until it drifted into orbit. By varying the gravity field around the spaceship, it could maneuver anywhere within the gravitational influence of our sun. The engine for this spaceship wouldn’t even have to be on the spaceship. A ground based station could project an “antigravity” field into space, providing propulsion at a distance. The change from chemical to gravity propulsion will be as significant as the change from horses to cars a century ago.