1. Hi, I’m William Hershel. And I’m Johan Wilhelm Ritter And we are SCIENTISTS! And we are SCIENTISTS!

2. In 1800 was working with my sister in Bath observing the Sun. This is a hazardous business so I put a dark filter over the end of the telescope. To my surprise I could sill feel the heat of the Sun even though virtually no light was getting through. What was going on? I decided to look at the colours of the spectrum individually to assess the amount of heat they provided. Not much as it turned out, although the closer I move the thermometer towards the red end of the spectrum the greater the temperature increase, hmmmm. Curiouser and curiouser! What in the name of Sir Isaac Newton was going on?

3. Aha!, cracked it! I arranged my apparatus as shown in this fantastic portrait. Pretty much all light was excluded from the room and a spectrum of colour was projected on the table. If you look closely you will see that the red part of the spectrum does not fall on the thermometer (the other two are for repeats). To my amazement the temperature beyond the red end of the spectrum rose! I was so excited my hand came unglued from my chin and I fell on the floor! I called this new heat source Infra-red and linked heat and light for the first time!

4. I was very interested to hear that William Hershel had discovered heat beyond the red wavelength of the spectrum. I was intrigued enough to start investigating ‘invisible light’ and looked for a possible cooling effect at the violet end of the light spectrum. I had been doing some experiments with Silver Chloride (which blackens in sunlight) and decided to test it with different colours of the spectrum. There was no discolouration with red light but it massively increased towards the violet, hmmmm……what was going on? Silver Chloride exposed to light Silver Chloride not exposed to light

5. I then put some Silver Chloride in an area just beyond the violet part of the spectrum i.e. where it was dark! To my amazement the Silver Nitrate went completely black well beyond the violet edge of the visible spectrum. Wow! I was amazed, I called this new form of light ‘Chemical Rays’ catchy eh? I then went on to discover electroplating but sadly died in poverty five years later aged only 33!