The noble Eötvös effect lets you outrun gravity

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It's not often that you get a physical effect named for a baron. It's also not often that physics demonstrations are made during naval maneuvers. That's what makes the Eötvös effect so notable. The effect shows that how much gravity you feel will depend on what direction you are traveling.

As many of you have noticed, maybe this morning, or maybe some other day, if you are standing on the western edge of a continent, away from the sun, the Earth will tug you eastward until you are under the sun. Not just once, either, but all the time. To be fair, it's lucky that that sort of thing happens on a planet as big as the Earth. If it were on some smaller rotating body, and you lost your grip, you would get hurled eastward off of it and plunge into the sun.


This is because all rotating bodies exert force pushing people - from their perspective - outwards. It's the same effective push that you feel when a turning bus pushes you against the outside wall. Something that's spinning as fast as the Earth is exerts a lot of it indeed. You're not thrown into the sun (or out into space) because the Earth exerts gravity to pull you inward. This more than compensates for the outward push. If the Earth were to get hollowed out a bit, and exert less gravity, you may not get thrown off, but you'd feel kind of a floating sensation, the way you do when an elevator moves down underneath you. You'd get the same sensation if the Earth were to retain its mass but spin faster, adding a little more kick to its attempts to throw you off. Although the gravity, in this case, would be the same you always felt, the increase in speed eastward would cause you to feel it less.

By why should the Earth do all the work? If you were to jump in a car, or a boat, and speed eastward, you would add your speed to the rotation of the Earth, and float. Your speed is generally miniscule, so you wouldn't notice it much, but you'd feel just a bit less of a downward pull. This is what the Hungarian baron, Loránd Eötvös, thought out when he noticed the odd data he got when comparing the results of gravity experiments done on ships at sea. When moving eastward, gravity seemed to fade away a little. When moving westward, it added a little extra force. He was a respected professor of physics, as well as a baron, and so he eventually prevailed upon two ships to do the same experiment, one while moving eastward and the other moving westward. Gravity either compounded or dissipated, all according to his calculations. Ever since then, this gravitational fluctuation has been dubbed the Eötvös effect. So if you're trying to convince yourself you're thinner, weigh yourself in a truck driving east. If you're trying to actually make yourself thinner, run west to get a better workout.


Image: US Navy

Via ELGI and The Hungarian National Cultural Fund.