Bill Bryson - The Measure of Things

The measure of things:

Triangulation is a popular method for working out distance and dimensions based on the principles that interior angles of a triangle sum 180°. For example:  if there was one person in Paris and one person in  Moscow and you knew the distance between the two people and you could connect an imaginary line between the two people and then two more lines to the moon you have a triangle. From there you can work out all the angles and the distance to the moon.

In 1684 Dr Halley visits Isaac Newton, he asked him to produce a paper on an unrelated matter, Newton did that and much more. He ended up developing, over the period of two years, his three laws of motion, which states simply that that an object will keep moving in a straight line until something some other force acts to slow or deflected it, that every action has an opposite an equal reaction and his universal law of gravitation that states every object in the universe extracts a tug on every other.

In 1769 a large number of the scientific community had set off to remote places in the world to observe the transit of Venus, their reason, to be able to calculate the distance from Earth to the sun and there find earths position in the solar system. All of the scientists that set out to watch the transit of Venus failed.  But a little-known Yorkshire born sea captain named James Cook successfully charted the Venusian transit. He watched the transit from a sunny hilltop in Tahiti and then went on to chart and claim Australia. Upon Captain Cooks return the French astronomer Joseph Lalande had enough information to calculate that the mean distance from the earth to the sun was little over 150,000,000 km. Later transits in the 19^th century astronomers came up with a figure of 149.5,000,000 km which has remained ever since.

In 1669 after many others had attempted, astronomer Jean Picard was able to devise a method of triangulation, he used it to make the most accurate measurement of a degree of Arc at 110.46 km. Which is the information needed to work out the circumference of the earth. Isaac Newton had a theory that the earth wasn’t a complete sphere and that there was a slight flattening at the polls, his theory was proven correct by Jean Picard.

The mass of the Earth was calculated in the summer of 1774 by Maskelyne on a mountain in Scotland. That summer he was able to calculate the mass of the Earth at 5,000 million million tons. From that calculation we can now calculate the mass of all the other major bodies in the solar system. Like the Sun. So from this one experiment we learnt the mass of the Earth, the Sun, the moon, other planets and there moons. Contour lines were invented in the process. They are the lines that are used to judge the altitude on a map, which we still used today.

In in 1769 Cavendish conducted an experiment with equipment made from a deceased scientist. The aim was to discover the weight of the earth. After a year when he had finished his calculations and experiments he was able to establish that the earths weight was 6 billion trillion metric tons.

So in conclusion by the late 18^th century scientists knew very precisely the shape, dimensions and weight of earth and its distance from the Sun and planets. Even with all the modern-day technology we’ve only been able to confirm these discoveries.

Ryan Gardner