The invention of the telescope has dramatically impacted our understanding of the Universe. Since the instrument was invented about four hundred years ago, our knowledge of the cosmos and the things in it have undergone many revolutions.
The history of the telescope tells us a lot about how astronomy and science generally have developed over the last few centuries. From knowing the Universe’s age to understanding the electromagnetic spectrum, the telescope has been crucial to many vital scientific discoveries.
Historians have not yet been able to pinpoint precisely when the telescope first appeared. The earliest known example is the Dutch Hans Lippershey’s telescope, invented in 1608. Lippershey was an eyeglass maker, and his invention could make distant objects appear closer by using refraction.
Refraction happens when a light beam travels from one medium to another. As you can see, for example, when you place a straw in a glass of water, and it looks as though the straw is broken, light bends as it travels through a different medium (from air to water, in this case).
Lippershey’s refracting telescope redirected light and magnified objects using a convex objective lens and a concave eyepiece. His invention quickly spread across Europe, and the astronomer Galileo improved the design the following year. In 1611, the astronomer Johannes Kepler, who gave us Kepler’s laws, found an even better method that used convex lenses for both the objective and the eyepiece. This was the preferred type of telescope until the middle of the nineteenth century when reflecting telescopes became the norm.
Galileo was the first astronomer to systematically use a telescope to magnify objects in the night sky. His telescope was not much better than the cheapest telescopes on the market today. Yet, he was able to find solid proof of heliocentrism with his telescope.
For 1000 years, Aristotle’s idea of a stationary Earth at the center of the Universe with other planets orbiting it had dominated religion and the sciences. Copernicus was the first scientist who suggested that the Earth might be another planet, like Venus and Mars, orbiting the Sun.
Galileo found the first proof in support of Copernicus’ theory when he trained his telescope on the night sky in 1610 and saw that Jupiter had four moons orbiting it. If everything orbited the Earth, this could not be possible.
He found further evidence when he discovered the phases of Venus. Venus would have phases in a geocentric system, but it would only go up to a half-Venus at most. Galileo’s observations included a full Venus and showed that the planet must orbit the Sun. A full Venus could only be possible if the planet were on the opposite side of the Sun to the Earth.
The Newtonian telescope
As Isaac Newton discovered, white light is a mixture of all colors. Newton let white light shine through a prism and found that the prism dispersed the light into a spectrum of colors. The problem with refracting telescopes is that the colors in light get distorted similarly when they pass through the glass, much like a straw in a glass of water.
Newton found a way around this distortion when he developed the first reflecting telescope, or Newtonian telescope, after experimenting with mirrors in the late 1660s. His invention relies on a concave mirror as the objective and a diagonal mirror.
The use of mirrors solved the problems of refraction because light does not pass through mirrors, unlike glass. It bounces off, and this proved genius when it came to telescopes.
Newton did not discover anything new with his telescope, but it helped confirm the ideas of Galileo and Copernicus. Like Galileo, Newton was able to observe moons in orbit around Jupiter and the phases of Venus. It continues to advance astronomy today, several centuries later. The majority of astronomical observations are still based on observations from reflecting telescopes.
Since the earliest telescopes several centuries ago, the instruments have gotten bigger and, eventually, helped by computers for precision. Today, there are large-scale astronomical observatories all over the world.
There are also quite a few observatories located in space. These tend to see parts of the electromagnetic spectrum that do not penetrate through the Earth’s atmosphere, such as x-rays and gamma rays.
The most ambitious telescopes of the last few decades are the Hubble and James Webb telescopes. These observatories orbit the Sun. Since it launched in 1990, the Hubble Telescope has aided many crucial cosmological discoveries. It has helped us determine the Universe’s age and the rate at which it is expanding and discovered that almost every large galaxy has a black hole at its center.
The James Webb Telescope has already proved very promising. It will surely add to our understanding of the early Universe and will be exciting to follow in the coming years.
Luckily, no large-scale astronomical observatory is necessary to enjoy star-gazing. Try looking at the night sky at home with your own telescope.