Total Supermoon eclipse
Lessons in the Bible, science, and sound thinking
On the night of 20 January to the morning of 21 January 2019, many in the Americas, western Europe, and north Africa had a chance to see a spectacular sight: a total eclipse of the moon—and the only one of the year. As a bonus, it was a ‘supermoon’, a ‘wolf moon’, and a ‘blood moon’, all at the same time. Lunar and solar eclipses have fascinated people for thousands of years, and they have enabled us to learn real science.
In medieval Europe, science started to flourish because of the belief in a divine Lawmaker who is a God of order. Much of the early science was involved with working out the rules He used in astronomy, and this led to great advances in physics. The fact that astronomers accurately predicted the timing of the recent lunar eclipse years in advance is a great example of the best operational science in action.
This latest eclipse was indeed worth watching. My wife and I used the occasion to take our first ever astronomical photographs, with a cellphone camera through our small (90-mm aperture) Newtonian reflecting telescope. And there are good lessons for all of us. But first we should define terms.
An eclipse is where one astronomical body is either obscured by or falls into the shadow of another astronomical body. An eclipse can be a partial obscuring, called a transit, or a total obscuring, called an occultation. But normally the term ‘eclipse’ is defined more narrowly to refer to a solar eclipse or a lunar eclipse.
On 21 August 2017, many in the USA saw a total solar eclipse, an occultation of the sun by the moon. On 15 January 1991, I witnessed an annular (ring-shaped) eclipse in Wellington, the capital of New Zealand, which could be called a transit of the sun by the moon. The reason for these different types of solar eclipses is that the moon’s orbit is not perfectly circular, but rather elliptical, as per the orbital theories of the great creationist scientists Kepler and Newton. Sometimes it is just a little bit closer to earth, allowing it to perfectly block out the sun. At other times it is just a little bit farther away, thus appearing just a little bit smaller and allowing the sun to ‘peep’ out from behind the slightly smaller moon.
But what about a ‘supermoon’? This just means a moon that looks bigger than usual, again because of its elliptical orbit. Because of normal laws of perspective, the observed angular size will be inversely proportional to its distance. So its greatest apparent size will be at its closest point, the perigee, and its smallest will be when it is furthest, the apogee. When the moon is full at its perigee, it is called a supermoon, and sometimes the moon at apogee is called a ‘micromoon’.
However, the difference is quite hard for most people to notice. A supermoon is only about 12% larger than a micromoon. But because brightness is proportional to the surface area, which is proportional to the square of the diameter, a supermoon is about 25% brighter. Yet apart from an unusually bright moon, a supermoon has hardly any practical effect on earth. The tides will be stronger, called perigean spring tides, but still the variation is only about 5 cm (2.5 inches) larger than normal in some places.
The term ‘wolf moon’ is North American in origin, and simply means the first full moon of the year, i.e. in January. There is nothing special about the moon in January, neither is the term ‘wolf’ always used. It is sometimes called the ‘old’ moon, and other full moons in other months have a diversity of names as well. Wolves are most active at dawn and dusk (i.e. crepuscular animals), and howl more after nightfall when it’s brighter, which often means when the moon is full. But they don’t howl at the moon as such; rather, they howl upwards, so the sound carries further, and the moon is also ‘upwards’. So, for some reason, Native Americans associated the moon in January with wolves. It is about as significant as the reason why our ancestors associated the first day of the week with the sun.
The term ‘blood moon’ refers to the redness that often appears in lunar eclipses. Despite some sensationalist false prophecies that float around from time to time, the redness is a natural phenomenon. It has been happening ever since there have been lunar eclipses and there was nothing more ‘bloody’ with this one than most others. In fact, it is basically a ‘sunset’ reflected off the moon—that is, if you were on the moon, the earth would be blocking the sun, but you would see a narrow ring of ‘sunrise’ and ‘sunset’ in the earth’s atmosphere.
The reason for the colours is that light scattering intensity is much stronger with the short wavelengths of colour—in the blue region.1 This is why the sky is blue: we see the strongly scattered blue light. But when the sun is low in the sky, the blue is scattered away from us so we don’t see it, and instead we see the longer wavelengths left behind: the red, orange, and yellow of sunrise and sunset. So the ‘blood moon’ is reflecting back the colours of our sunrise and sunset. However, sometimes a very narrow light blue band is visible on the edge of the moon, thanks to earth’s ozone layer allowing some blue light through.
Note that the redness of the moon during a lunar eclipse is sometimes hard to see with the naked eye, because at low light, we have weak colour vision. This was true in our case. But with the telescope gathering far more light than our eyeball can, the redness (or orangeness) was clear.2
Ancient knowledge of eclipses
The Bible’s first reference to the moon refers to its creation on Day 4: “the lesser light to rule the night” (Genesis 1:16). However, it left open the question of how it produces the light. A proper ministerial use of science shows that it has no light of its own, but shines by reflected light. Johannes Sacrobosco’s astronomy textbook The Sphere (AD 1230) explains that during a lunar eclipse “the moon has no light except from the sun, it actually is deprived of light” when the earth blocks the sun.3 The fact that the moon has no light of its own is so obvious as to never have been doubted throughout history. As science historian James Hannam states, “…no less a churchman than Pope Innocent III (c. 1160–1216) was perfectly aware that the moon’s light is reflected from the sun, and seemed to assume that this was widely known.”4
Proof of a spherical earth
Lunar eclipses are also of great historic importance, as they provided us with probably the first known proof that we live on a globe. The reason is that the shadow of the earth on the moon always has a circular outline, no matter where in the sky the moon was at the time. The only object that will always cast a circular shadow from all directions is a sphere. For example, the famous philosopher Aristotle (384–322 BC) explained:
How else would eclipses of the moon show segments shaped as we see them? As it is, the shapes which the moon itself each month shows are of every kind—straight, gibbous, and concave—but in eclipses the outline is always curved: and, since it is the interposition of the earth that makes the eclipse, the form of this line will be caused by the form of the earth’s surface, which is therefore spherical.5
Indeed, the moon was almost straight above us at our house. But UK viewers had the best view of the eclipse 4:41am–5:43am, when the moon was lower in the sky. Yet they saw the same circular shadow.
While there might be a few modern people who believe the fringe idea that the earth is flat, the lunar eclipse disproves a flat earth in an even more obvious way: that it was visible from only one hemisphere. On a flat earth, the eclipse should have been visible from anywhere, and no amount of ‘refraction’, ‘lensing’, or ‘perspective’ will change this fact.
Calculating the moon’s size
Aristarchus of Samos (310–230 BC) made some careful observations, without the benefit of telescopes (they were not invented until 1608 by Hans Lippershey). And from those, he used ingenious mathematics to work out the relative size of the earth and moon.6
By measuring the position of the moon at the start and finish of the eclipse, he worked out the angular size of the earth’s shadow (Rem). He already knew the angular size of the moon (Rm), and from both combined, he found that the earth’s shadow at the moon is about 2.7 times the angular size of the moon itself (this is also why a lunar eclipse lasts longer than a total solar eclipse). He then showed that the radius of the earth’s shadow at the moon was about the difference between the earth’s radius (Re) and the moon’s (Rm).
So combine Rem = 2.7 Rm and Rem = Re – Rm, he showed that Re = 3.7 Rm.7
Modern astronomers agree with this (to one decimal place)! Thus any modern chronological snob who thinks ancient people were stupid really has no clue of how smart our forefathers really were.
Why don’t we see an eclipse every time the sun, earth, and moon are more or less in a straight line (or, in syzygy), in that order, i.e. every full moon? Because the plane of the moon’s orbit around the earth is tilted with respect to the plane of the earth’s orbit around the sun (the ecliptic). It takes careful analysis to predict when the three will line up in just the right way.
To do this, you will need to use the three laws of planetary motion, discovered and published by Johannes Kepler from 1609–1619:
- The first law pertains to the shape of orbits: planets move in elliptical, not circular, orbits with the sun at one of the two foci of the ellipse.
- The second law has to do with speed: the planets didn’t move at constant speed. They move faster when they are closest to the sun; specifically, with every planet, the line from planet to sun sweeps out equal areas in equal times.
- The third law deals with the relationships between all planetary orbits in the solar system: the square of the orbital period is proportional to the cube of the semi-major axis of the orbit.
These laws won the day, not because of any conspiracy, whether by Freemasons, Jesuits, Illuminati, Rothschilds, or [name conspiracy group du jour here]. Rather, the reason is very simple: they were far better at prediction than any previous solar system model. Further, they enabled Sir Isaac Newton to develop his laws of motion and the Law of Gravity, which are incredibly important in the world of science today. He also showed that the laws of motion and gravity predicted Kepler’s laws. In other words, Kepler described an effect and Newton explained why it happened. Newton was also able to extend them to orbits around other massive bodies. Kepler had observed that the Galilean moons orbiting Jupiter also obeyed his third law, and Newton showed why. Newton also invented the eponymous Newtonian telescope we used to observe and photograph the lunar eclipse that is the focus of this article.
One minor difference is that Kepler taught that the sun was at the focus of the orbit; Newton showed that the focus was actually the centre of mass of the system, or barycentre. But as Kepler’s laws were such a good approximation to reality, Newton’s laws prove that the sun must be enormously more massive than the planets—and indeed it is. The sun has over 99.86% of the mass of the solar system.
Newton’s laws were the first dynamic model of the solar system, i.e. one that explained motion in terms of causes, or forces. This has been the most successfully predictive scientific model in history. After all, previous models were just kinematic models, i.e. just describing the motions. They did not know why the motions were the way they were, but they could describe them in exquisite detail. What if the orbit was not quite what was predicted? Well, since they were just describing things, they could just tweak the explanation. They could add an epicycle or an accessory explanation any time they liked. But this is not so with a dynamic model. Once you have a physical reason for the way things work, when you find a discrepancy you look for a cause for the difference. This is how Neptune was discovered: Uranus was discovered by analyzing the orbits of Jupiter and Saturn. But after it had gone only ¾ of the way around the sun, they noticed its orbit wasn’t quite as predicted, so they realized there must be another massive body perturbing the orbit. They worked out the mathematics, decided where a hidden planet must lie, pointed a telescope at that spot, and Neptune, which was otherwise invisible to the naked eye, was discovered that very night (see The Discovery of Neptune).
This same Kepler–Newton model predicted the timing of the eclipse, and that it would be both a total eclipse and a supermoon. If anyone wants to promote an alternative geocentric model, let alone a flat-earth model, it must have the same predictive power. Good luck with that.
Lunar eclipse and flat earth
Despite our best efforts, the recently formed flat-earth idea (the adherents of which operate in a very cult-like manner) is not quite dead. Yet, as explained before, a lunar eclipse was the earliest historical proof of a global earth, and this was known about 2,500 years ago! This latest eclipse was a chance to challenge some of the holdouts. We get to ask, if it’s not the earth causing the shadow, then what is?
The usual answer is a cop-out: the moon is “self-lit”. This, of course flies in the face of all observational evidence: the lit portions are always the ones facing the sun, and the phases of the moon track the position of the sun in the sky. Also, the shadows on the moon are clearly lit from above rather than from below, and clearly from the direction of the sun. This would require some incredibly good optical effects if it were self-lit.
Another answer we sometimes hear is that some unknown object is blocking the light from the sun. But the problem is, this ‘unknown object’ must still be a sphere to cast the shadow with a circular outline! Yet another problem is: why does this unknown object always block the moon at exactly the same time and place where astronomers predicted an eclipse from the Kepler–Newton model? And how can flat earthers predict future eclipses with their model, because how can we possibly know how when an unknown object will appear next?
In discussing this with someone online, this argument was one of the very few times when a flat-earther had to admit defeat, at least on this point! (Not that he had any remotely plausible responses on any other point either.)
The recent total eclipse was a spectacular event, displaying God’s creative glory and helping us learn about how He upholds his creation via what we call ‘natural laws’. Such studies helped some of the greatest scientists in history develop extremely powerful predictive models.
At CMI, we admire real operational science. We are also foundationally pro-Bible, not anti-establishment for the sake of it. Hence, we reject conspiratorial theorizing, including the recent flat earth nonsense. The only reason astronomers believe the Kepler–Newton barycentric model of the solar system is that it works far better than any previous model. In fact, over hundreds of years of observation, no one has ever found an exception. The fact that many people could enjoy this eclipse is just one of countless examples.
References and notes
- The scattering of light by air molecules is called Rayleigh scattering, and is proportional to the fourth power of frequency Return to text.
- Note that the point of a telescope is not magnification per se—forget cheap telescopes that brag about huge magnification. Magnification of what? Magnifying a dim and poorly focused image will just result in a large but dim and poorly focused image. Magnification is not an end in itself—the end is to resolve detail. So light collection and resolving power are the main points of a telescope. See The Stargazer’s Guide to the Night Sky. Return to text.
- Johannes Sacrobosco, The Sphere, AD 1230, esotericarchives.com, accessed 22 January 2019. Return to text.
- Hannam, J., God’s Philosophers: How the Medieval World Laid the Foundations of Modern Science, ch. 4, Icon Books, London, UK, 2009. Return to text.
- Works of Aristotle I: p. 389. Return to text.
- Aristarchus, On the Sizes and Distances, 3rd century BC. Return to text.
- Ladd, E., Astronomy 101 Specials: Aristarchus and the Size of the Moon, Bucknell University, eg.bucknell.edu, accessed 22 January 2019. Return to text.
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