Mindful Thoughts for Stargazers by Mark Westmoquette

Author:Mark Westmoquette
Language: eng
Format: epub
Publisher: Leaping Hare Press
Published: 2019-11-15T00:00:00+00:00

Against a bright background we see dark bands in the rainbow, but when we look at light against a dark background we might see certain bright lines. Every atom absorbs or emits light at particular frequencies, just like the skin of every human finger has a different pattern of swirls. Using this knowledge, when we observe light from space split into its spectrum we can identify the make-up of the gas that we’re looking at. This technique is called spectroscopy and it is what turns astronomy from simple taxonomy into a true science.

There is more information we can get from a spectrum than just the composition of the source of the light. With a few equations we can work out the temperature, and we can also measure the source’s radial velocity via the Doppler effect. Think of the sound of an approaching car. As it gets nearer the sound appears to get higher in pitch, and after it passes it gets lower. In exactly the same way, the colour of light gets bluer when approaching, and redder when receding. This is exactly how Edwin Hubble discovered in the 1930s that the Universe is expanding.

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