Light and Telescopes
Ibn al-Haytham (known as Alhazen) was a Muslim scientist living in Egypt in the early 11th Century. He was the first scientist in the world to do an experiment using what we now call ‘the scientific method’. Alhazen worked on the topic of optics. Optics is the study of light. Alhazen worked out that we see things when light coming from the Sun enters our eyes after bouncing off an object. He also proved that light travels in a straight line by carrying out an experiment with lanterns and a hole in a wall.
In 1608, German-Dutch spectacle maker, Hans Lipperhey (sometimes spelt Lippershey) was the first person to file a patent for a refracting telescope. He applied to the States General of the Netherlands for a patent for his instrument "for seeing things far away as if they were nearby". He did not receive a patent (because other lens makers seemed to be making similar devices) but the government paid him for his design. The first Dutch telescopes consisted of a convex and concave lens.
In the mid-17th Century, English astronomer Isaac Newton demonstrated that you could split light into a spectrum of colours using a prism. From this work he realised that light collected by a refracting telescope would spread out and wouldn’t give the best image. To solve this problem he invented the reflecting telescope. Almost all the major telescopes used in astronomy research today are reflectors, including the Liverpool Telescope.
For most of history, visible light was the only known part of the electromagnetic spectrum. In 1800, German-British astronomer William Herschel discovered infrared radiation. He was investigating the temperature of different colours of light and observed that the highest temperature was beyond the red light. He hypothesised that this was due to a type of light ray that couldn’t be seen by human eyes. Over the next 100 years the rest of the electromagnetic spectrum was discovered. There are now telescopes observing the Universe across the electromagnetic spectrum.