Supermoon was a term that turned up in various social media
news items in the recent past. While obviously sparking an interest among the
general public, it drew some criticism from prominent figures in astronomy like
Neil deGrass Tyson (http://time.com/5046984/neil-degrasse-tyson-goes-on-epic-rant-about-tonights-supermoon-calls-it-an-embarrassment/)
on how the term is a major exaggeration of reality.
What does supermoon mean? The term supermoon has turned out to mean that Moon appears bigger than usual. This happens because the orbit of the Moon around the Earth is not a circle, it is infact an ellipse. At its closest point to Earth, the Moon is about 360,000km away where as at its furthest, it is about 405,000km away. For comparison, the Earth it self is about 12,600km across (diameter). It looks like the Moon swings at least four Earths towards and away, and that is clearly a big swing. So why do the astronomers claim that it is not a big deal?
While the difference in the distances is big when absolute numbers are considered, the Moon is already quite far away. The change of the distance from the furthest to the nearest is about 11%. Compared to the average distance of 384,400km, the closest approach is just 4% closer and the furthest is just above 5% further. This doesn't mean that the change of the size of the moon is insignificant, it just means that it is not as big as it sounds.
What does supermoon mean? The term supermoon has turned out to mean that Moon appears bigger than usual. This happens because the orbit of the Moon around the Earth is not a circle, it is infact an ellipse. At its closest point to Earth, the Moon is about 360,000km away where as at its furthest, it is about 405,000km away. For comparison, the Earth it self is about 12,600km across (diameter). It looks like the Moon swings at least four Earths towards and away, and that is clearly a big swing. So why do the astronomers claim that it is not a big deal?
While the difference in the distances is big when absolute numbers are considered, the Moon is already quite far away. The change of the distance from the furthest to the nearest is about 11%. Compared to the average distance of 384,400km, the closest approach is just 4% closer and the furthest is just above 5% further. This doesn't mean that the change of the size of the moon is insignificant, it just means that it is not as big as it sounds.
The year 2018 was an interesting year in the sense of this
phenomenon because the year started off with a “supermoon” and also an eclipse.
It gave a good opportunity to photographically compare the sizes of the moon.
 |
| Supermoon - 01st Jan 2018 compared to other full moons |
If you compare the photos over three full moons, you could
see that the size of the moon has changed, but not really significantly. Since
I could not take the photos exactly on the full moons, I have demarcated the
circumference of the moon on the photos of 30th January and 03rd
March.
The rightmost photo of the series, is a photo of the Sun taken on 03rd March 2018. The comparison is important because the apparent size of the Moon and the Sun is what makes solar eclipses possible. When the apparent size of the Moon is same size as that of the Sun or slightly larger, you have the possibility of having a total solar eclipse. When the apparent size of the Moon is lower, then you get an annular solar eclipse. That however, is a different topic altogether.
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