The heart and soul of science is found in its toys. Each science has its own collection of toys--devices which allow the science to be done. The devices which make science go are clever. I would like to talk about some of the most fun ones,which everyone should know about.
In the sevententh century, the five most interesting toys were the telescope, the microscope, the camera lens,the spectroscope, and the clock..
A telescope made for visual use has a long focal length (long radius or low curcature) converging element combined with an eyepiece (usually a short focal length converging lens system). If the long focal length element is a lens the telescope is a refractor, if it is a mirror, the telscope is a reflector.
The long focal length divided by the short is the power of the telescope. The long focal length divided by the entrance diameter ( the "aperture") is the f-number or speed of the telescope.
The power and speed both help when looking through a telescope. The power magnifies the object, and the speed increases its brightness.
A microscope has a short focal length element combined with an eyepiece. Power and aperture are important here, too, but calculated in a more complex fashion.
The camera lens is a converging lens or lens system. Such a lens forms an image on a surface. The surface can be paper, film, glass ground on one side, a ccd array, or other useful structure. The focal length determines the width between parts of the image. A formula for this is s=.01744f, where s is the image distance between objects one degree apart ( in focal length units) and f is the focal length. The longer the focal length, the wider the distance on the image.
It is possible to use telescopes and microscope as camera lenses when they are adjusted to converge the light.
The Spectroscope breaks light into its component colors. Since elements radiate and absorb light at very precise characteristc colors, looking at the colors in light can identify the elements present.
Two effects can be used: Glass doesn't bend all colors equally, so a prism of glass will spread colors. Light also diffracts when coming out of a slit, causing interference which makes colors appear only in certain places.
. These four devices all derived from the techniques for making spectacle lenses.
The techniques are simple.
To make lenses, two pieces of glass are ground together with increasingly finer grit--which could be river sand graded by stirring it in water and letting the bigger pieces settle out--until a spherical shape comes about almost automatically. The early grinding is across the chord of the circle to wear down the center of one piece of glass and the edge of the other, creating a sphere quickly. Later fine grinding is done across the center. One piece is rotated in relationship to the other.
To make a flat surface or a prism, three pieces of glass are ground together until they all fit together. At that point, they are accurately flat.
After grinding, a "pitch lap" is molded from the accurately ground surface, charged with polish--iron rust powder will work--and the surface polished to invisibility. New surfaces are tested in various ways and worked with polish until they are as perfect as need be.
This simple process, along with simple tests, produces the most accurate surfaces known. The quality of optical devices is astounding. Accuracy to one wavelength of visible light (one hundred thousandth of an inch, or 500 billionths of a meter) is essential, while the best surfaces are accurate to 40 times that.
These surfaces can be huge, too. The Keck Telescope is ten meters, or 33 feet, in diameter!
The first accurate clocks made use of a pendulum which swings back and forth in largely equal periods no matter how hard it's swinging. The escapement transfers the pulse to the gears for the indicating hands, and gives a little push back to the pendulum to keep it running. A weight or a spring supplied the power to keep the whole thing going.
Clocks can be made with only a lathe and a gear milling machine. The number of steps is quite large and cover the whole range of machinig processes.
The first use of these toys is still the most dramatic story.
The early astronomer Aristarchus had advanced the theory that the Earth went around the sun, and the astronomer Ptolemy held that the Earth was in the center of the universe.
In Aristarchus' scheme, the sun is stationary, the planets revolve around the sun with Mercury and Venus inside Earths orbit, and Mars, Jupiter, and Saturn outside. The Moon rotates around the Earth.
In Ptolemy's scheme, the Earth is stationary.
In the middle ages, Christianity had accepted the doctrine that the Earth was in the center of the universe. This was remarkably convenient for advancing the belief that heaven was "up there" above the stars, and hell "down there" under the ground. God was as far away from people as it was possible to get, and getting to God required superhuman effort.
Copernicus expanded the view of Aristarchus, though he didn't publish it in his lifetime. One of the main objections to Copernicus was that the moon could never keep up with the Earth as the Earth went around the sun. As long as Copernicus could be marginalized, all was well for the church. The objection about the moon was one of the best objections to Copernicus.
Galileo built a telescope and began looking at the heavens. One of the first sights he saw was the four bright moons of Jupiter. These are still a wonderful sight today--swinging around Jupiter in a perfect straight line. Here was proof that a planet could move and retain moons. Here also was a miniature solar system to study. Galileo had applied a new instrument to the study of the old questions. I'm sure many Christians still wish the telescope had never been invented.
The wonderful story of getting the distance to the stars and galaxies is summarized here.