The Banner of Heaven

This term, originally coined in the late nineteenth century, at least with its current connotation, began to speak to me in a unique way in high school. I took a backpacking trip in Northern California, and experienced a dry, warm, cloudless night with no shelter but a mosquito net. The sky was brilliant, and it felt like you could see the cosmos move around the Earth. It was here that I first saw the Banner of Heaven, the distinct and almost colorful band of what looks like nebulas that stretches across the night sky. It was not colorful language, it actually looks like a banner. 

Nearly all human beings, from the beginning of the species until the twentieth century, regularly slept and lived under it. But after the large-scale adoption of electric lightbulbs, light pollution began to float into our night skies. So, for all of our technological advancements, and all of our knowledge about the universe, modern people live their everyday more emotionally disconnected from the universe than any other people that have ever existed. This is why when I told my friends about the trip, they also seemed pitifully unfamiliar with how the night sky actually looked. 

Here is a map of light pollution in the United States:

While it may look a lot like a population density map, the ramifications are quite tragic: most Americans have never seen the night sky. One could certainly theorize about the impact the theft of this aspect of our natural habitat could have on our health, but you wouldn’t need to, the impacts are undeniable. 

The lack of true darkness has interrupted our circadian rhythms, in particular our ability to produce melatonin, which light prevents, resulting in difficulty sleeping, anxiety, headaches, and other health issues. Blue light, in particular, associated with screens and LEDs, stimulates our bodies in unnatural and unhealthy ways at night. But it isn’t just humans.

Animals also have been observed to disrupt migration patterns, disrupt their sleep schedules, and even to lose accuracy in their sense of direction due to light pollution.

Those most active and concerned about it, of course, are astronomers. Though it may seem crippling, strategically placed telescopes have become the main sources of data-driven observation for astronomy, so the ability for them to observe themselves is not an issue. What is an issue, however, is that if people themselves are not inspired to look at the sky, especially when they are young, they will not grow the curiosity that it necessary to maintain healthy astronomy communities.

NatGeo

Light Pollution Map

Celestial Navigation – Blog 1

People have used the stars to navigate for millennia, with expert sailors learning the geography of the sky above and using it as a very powerful tool. Though much less necessary in the modern day, given our access to GPS, people still take an interest to learn how to navigate using celestial bodies. These people often can navigate with the use a sextant, a watch, some paper, a calculator, and a map, using some version of techniques that are hundreds of years old. 

Firstly, almost all of the math used in celestial navigation is based in trigonometry, meaning anyone who graduated high school could learn how to do it, and the math has been the same for many hundreds of years, despite the enormous advances made in mathematics. The stars are basically assumed to be fixed on a dome surrounding the earth, which rotates inside, and the star’s position is used to discern what is directly beneath it. Thus, the sailor calculates his distance from the star, or rather, the point on earth directly beneath the star. Using three separate points can give a high degree of accuracy as to where the sailor is on earth. 

The most interesting tidbit of information to me, is how celestial navigators account for “dip” and refraction. Dip is the difference between the real horizon and the apparent horizon caused by the hight of the observer. The formula used for dip is Dip=1.76√Height. This is, of course, an estimation, but I found it so interesting that theoretical accuracy is not the primary concern, but rather, simplicity of usage, and this is mirrored in refraction as well (Refraction=0.96/tan(Altitude)). There are also all kinds of tips and tricks for corrections due to temperature, pressure, and high altitude.

I think learning how to use the sky like a tradesman, as well as an enthusiast or an academic, can greatly expand your appreciation for its relationship with our lives down on earth.