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.
Safety: Please remember to never observe the Sun without proper eye protection. Solar glasses are needed to observe naked eye and proper objective mounted filters or projection should be used to observe it in binoculars or telescope.
Stargazing is winding down for the year in the far north of Scotland. Today is the last day with official ‘night’ this far north at 57 degrees latitude (Inverness). Between 1.00am and 1.27am tonight you can experience just over 20 mins of night. By tomorrow this will be gone, replaced by astronomical twilight. And by mid May we’ll have lost our astronomical twilight as well.
Orkney and Shetland have already lost all night and are rapidly running out of astronomical twilight.
The further south you live, however, the more darkness you still hold on to. Around Glasgow and Edinburgh you still have 2 hours 30 mins of night (currently from midnight until 2.27am). And at London latitudes you still have a whopping 4 hours and 20 minutes. (from 10.50pm until 3.10am).
As we head into the summer days I’ll be shifting the focus of the page towards the Sun, Moon, bright planets, noctilucent clouds and the near midnight Sun phenomena we experience during the long days from May until August.
Here’s hoping for lots of clear and sunny skies.
Picture: Sunset over Ben Wyvis from the Bunchrew shoreline.
*Night is defied as the Sun sitting 18 degrees below the horizon (see accompanying picture from timeanddate)
I wanted to share some images with you that had me transfixed when I was a young boy (and still do to this day). I recall first seeing them in a hardback book of my father’s called Cosmos (which presumably accompanied the TV series that was being broadcast at the time).
The images depict the fate of our planet as the Sun transitions into a red giant star, at the very end of its life, some 4-5 billion years from now.
As the temperature of the Sun slowly increases, the oceans recede and our precious atmosphere is stripped away. Eventually the whole horizon is overwhelmed by the Sun in a bloated distended form, with the final image showing the Earth completely barren and parched.
I remember wondering at the time – where would all the people and animals be? Would we perish or find some new star to call our home? I think it was the first moment I glimpsed the immensity of stellar time scales and how tiny human lives and endeavours appeared to be next to these vast physical processes.
This is still what fascinates me most about astronomy and cosmology, and it’s amazing how something as natural and simple as looking up at the stars is a gateway into these incredible realms of the imagination.
Anyway here are the images, including their original captions. I was also pleased to find out that Adolf Shaller is still producing amazing art. Try an image search on Google with his name and enjoy.
Changing position of Sunrise from a fixed location over a year
The changing position of Sunrise throughout a year from a fixed location. The further north or south of the equator we live the more extreme our seasonal changes and the bigger shifts we perceive in the sunrise or sunset position during the year. In such harsh and changing seasons it would also have been the more important for ancient cultures to mark the seasons.
Using the landscape to mark the seasons like this is called a horizon calendar. But what if your horizons are flat and featureless, or you require more accuracy, or you’re a powerful priest and wish to theatricise important changes in time?
Then ‘perhaps’ you construct an artificial horizon by placing large stones to mark the progress of the Sun – a henge.
The northern lights looking over the Beauly firth towards the Black Isle, Inverness-shire
After reports of a KP6 geomagnetic storm predicted to strike Scotland over the weekend, and clear skies on Sunday evening, I headed out after sunset to try and catch the northern lights. This was a very early aurora excursion as nights have only just got dark enough for decent views of the night sky, let alone tracking down the faint and elusive northern lights.
My initial outing took my into the hills above Bunchrew where I bagged some lovely views of the summer Milky Way overhead. Turning my attention north I noticed a faint arc of light on the horizon, and sure enough some test shots picked up a vibrant band of purple and green auroral light. However little structure was evident until I moved to lower elevations, reaching the Bunchrew shoreline just after 10.30pm.
The Milky Way near Cygnus, framed between trees above Bunchrew.
From this new vantage, in the dark looking over the Beauly Firth, the northern lights stood out much more clearly as distant columns of white light, slowly morphing and scintillating above the horizon. Some of the images (attached) show nice structure and the suggestion of wave like movement.
As our nights get darker many more opportunities to view the aurora will present themselves. The best strategy is to simply get out there as often as you can when it’s clear, and try and escape the boundaries of light polluted towns and cities. Aurora forecasts should only be used as a guide as they’re seldom reliable. Remember to look north and where possible find some nice low horizons in this direction.
Good luck and clear skies.
The aurora is caused by the solar wind slamming into the earth’s atmosphere near the poles, ionising chemical elements which produce light at very specific quantised frequencies.