Why do we See what we See?

The western highlands of Scotland, bathed in the visible light of our home star.

When we think about the vast array of electromagnetic radiation all around us – from Gamma rays, X-rays , UV, Microwaves and Radio waves – a natural question to ask is why do human eyes see in a very narrow band we call ‘visible light’?

The answer is undoubtably tied to the energy output of our nearest star – the Sun. Its peak radiation just happens to be at this ‘visible’ band of radiation. I’ve illustrated this below with a black body radiation profile of our Sun.

Our eyes have therefore evolved to ‘see’ this particular narrow range of otherwise insignificant wavelengths. There’s nothing inherently important about visible light – in fact it makes up a tiny 0.0035 percent of the entire electromagnetic spectrum!

Understanding this makes me wonder about the potential sensory apparatus of life that might have evolved elsewhere in the universe. Other stars with different stellar classifications to our Sun have markedly different peak radiation profiles.

If we had evolved next to a source of intense gamma rays for instance, we would very likely be completely blind to visible light but adept at observing small granular differences in the intensity of gamma radiation.

M13 The Great Hercules Globular Cluster

The Great Hercules Globular Cluster – M13

I hope you enjoy this conversational deep dive into the great globular cluster in Hercules. Joining me once again is Steve Owens, astronomer at Glasgow Science Centre and author of Stargazing For Dummies.

In this video podcast we discuss:

1. Finding M13 and what to expect when observing.
2. The physical scale and composition of this vast cluster.
3. What the night sky might look like from within M13.
4. Could life emerge and survive within these ancient and densely packed stellar environments.
5. What can globular clusters tell us about our position within our own Milky Way.

Music by Rising Galaxy, Cosmicleaf Records , Spain.