Helder Araujo

@hjaraujo

Joined June 2009

898 Following

52 Followers

246 Posts

hjaraujo retweeted

Mathematica

@mathemetica

about 1 month ago

In June 1798, Henry Cavendish achieved something extraordinary that no one had ever done before. Working alone in his quiet London home, he successfully weighed the entire Earth. He designed and built an incredibly sensitive torsion balance. It consisted of a wooden rod with two small lead balls suspended from a hair-thin wire inside a sealed wooden box to protect it from air currents. Then he carefully brought two enormous 350-pound lead spheres close to the small balls. The faint gravitational attraction between them caused the wire to twist by a tiny fraction of a degree. This minuscule movement was so delicate that it could only be observed through a telescope aimed at a scale placed several feet away. From that almost invisible twist, Cavendish applied Newton’s law of universal gravitation. He was able to calculate the density of the Earth and from that its total mass. His result was astonishingly accurate and remains very close to the value we use today. With just two lead spheres and a wire thinner than a human hair, one man had measured the weight of our entire planet. A simple yet brilliant setup that delivered a truly cosmic result.

$mathemetica's tweet photo. In June 1798, Henry Cavendish achieved something extraordinary that no one had ever done before. Working alone in his quiet London home, he successfully weighed the entire Earth. He designed and built an incredibly sensitive torsion balance. It consisted of a wooden rod with two small lead balls suspended from a hair-thin wire inside a sealed wooden box to protect it from air currents. Then he carefully brought two enormous 350-pound lead spheres close to the small balls. The faint gravitational attraction between them caused the wire to twist by a tiny fraction of a degree. This minuscule movement was so delicate that it could only be observed through a telescope aimed at a scale placed several feet away. From that almost invisible twist, Cavendish applied Newton’s law of universal gravitation. He was able to calculate the density of the Earth and from that its total mass. His result was astonishingly accurate and remains very close to the value we use today. With just two lead spheres and a wire thinner than a human hair, one man had measured the weight of our entire planet. A simple yet brilliant setup that delivered a truly cosmic result.$