"Alle vil redde verden, men ingen vil hjelpe mamma med oppvasken"

Observing gravity

Yeah, what a big deal, you might say. We see gravity all around us every day. The fact that we’re not floating around in universe together with fish & stars is due to the fact of gravity. It is truly no big deal to observe gravity.

Gravity is weird. Its a theory that says all masses in the universe attracts each other. Although the phenomenon is well known, we do still know very little about it, and why it happens. Maybe some of the reasons for this ignorance is that we need so much mass in order to get a real force between two masses. However, yesterday I managed to observe forces between two tiny metal balls.

The experiment I did was first done by Henry Cavendish and the results was published in 1798. Cavendish task was to find the density of the earth. However, by doing so he also measured the gravity constant: The G in Newtons formula of universial gravitation. The way the experiment was conducted was that we measured the gravitational force between two sets of tiny small metall spheres (15g and 1.5kg) shown by torsion in a small wire (that will rotate to a certain degree when a force is applied to it). By sending a laster light in a mirror connected to the wire, we were able to measure this angle by reflecting it on a stationary ruler. When the two big balls were taken close to the small ones the laser light started to move, and hence I were able to see the gravitational forces the small balls were moved by. The forces are not big, a tenth of a million of a sugar pack’s force toward the earth. When Cavendish conducted the experiment for two hundred years ago, he managed to find the universial gravity constant within 1% uncertainty of todays measure of G. Today, the use of G is used wherever you turn. In nearly all technology it has been essential to calculate with the number G, and most people is maybe more familiar with the number when it is multiplied with the Mass of earth and divided by the square radius of the earth; namely 9.8 m/s^2.

This really mindblowing experiment is a good history lesson. Experiments such as  this one is maybe why I absolutely do not think that the world will go under due to global warming if we do not dramatically stop all consumption on earth, like some says. The technology that boosted out of scientists like Newton, Cavendish and Einstein was completely unimaginable at that time. Yet it is now seemed as one of the most common things. We will have one of those revolutions in the question about global warming as well – the human society is more creative than anyone can think.

By the way, my measurement of G was almost 20% off todays value.


6 november, 2008 - Posted by | Uncategorized | , ,

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