Today marks the start of a new lunar year! There are several key differences between a solar new year and a lunar new year. The most common calendar system in the West, the Gregorian calendar, is based on the Earth’s orbit around the sun. Every New Year, the Earth is more or less in the same position around the sun as one year prior. The lunar new year, however, is based on the cycles of the moon.
There are two types of calendars that use the moon to track time. Purely lunar calendars, such as the Islamic Hijri calendar, do not rely on the sun at all. In the Hijri calendar, the new moon determines the start of the month. As a result, lunar years are shorter than solar years, taking only 354 days. As centuries have passed, the Hijri calendar has deviated from the Gregorian calendar by about 40 years. Also, because the Lunar calendar does not depend on the Earth’s orbit around the sun, the months of the year have no correlation to the seasons. This year, the Hijri calendar starts in July, but years from now it will start in January, the complete opposite season.
The other type of lunar calendar, such as the Chinese calendar, is the lunisolar calendar. Lunisolar calendars, as you might be able to guess, are a combination of solar and lunar calendars. The Chinese calendar starts each month on the new moon, and begins each year at the beginning of the second month after the winter solstice. In order to keep the calendar in check relative to the solar year, occasional leap months are implemented. There are 7 leap months across a cyclical period of 19 years, and they are inserted before the new year.
As I was researching this blog post, I got curious to see how the Western and Chinese zodiacs differ. Since Western zodiac signs are based on the Earth’s orbit around the sun, and the Gregorian calendar is also based on the Earth’s relationship to the sun, I wondered if the Chinese zodiac is somehow related to the moon. As it turns out, Chinese astrology is based on the planets which are visible to the naked eye; Mercury, Venus, Mars, Jupiter, and Saturn. Each of these represent an element, and combining those with your zodiac sign (which is determined by the 7 year cycle) will give you some insight into your personality, apparently.
There are 2 solstices: the June and December Solstice.
The June Solstice is the point on the celestial sphere where the ecliptic is farthest north of the celestial equator. Similarly, the December solstice is the point on the celestial sphere where the ecliptic is farthest south of the celestial equator. The June and December Solstice occur around June and December 21st, respectively. During the June and December Solstices, the sun appears directly over the Tropic of Cancer and Tropic of Capricorn, respectively.
There are 2 equinoxes: the March and September Equinox. During both equinoxes, each of Earth’s hemispheres receive equal sunlight. The March and September Equinox occur around March and September 21st, respectively. The equinoxes occur when the celestial equator intersects the elliptic.
Eclipses are awesome, beautiful, and rare celestial event.As we talked in the class, there are four types of solar eclipse, including total solar eclipse, annular solar eclipse, partial solar eclipse and total annular eclipse. Because of my interest, I started looking for relevant information on the Internet. In the process, I found a website published by NASA that predicts solar eclipses.
Earth’s Moon is in a synchronous orbit, meaning that people on Earth can only see the near side of the Moon. But what keeps the Moon locked in this synchronous orbit? The answer is tidal locking.
Early in the history of the Solar System, a Mars-sized object collided with prehistoric Earth, and the debris from both objects formed a ring around the Earth and eventually formed a molten object. The molten Moon was much closer to the Earth and spinning much faster than it is now, and gravity from the Earth pulled our Moon into a space football. The part of the Moon closest to the Earth would have bulged as the Moon rotates, but it took time for so much material to shift around, meaning that the bulge of the Moon was always pulled towards alignment but never perfectly aligned. As the Moon changed its shape, energy dissipated into space as heat, and with less rotational energy, the Moon gradually slowed into a synchronous orbit.
In its synchronous orbit, the bulge of the Moon would no longer need to be aligned, since the point of the bulge would always be facing the Earth. No more energy was lost through the shifting of its shape, and the Moon’s rotation rate remained steady ever since.
Tidal locking is not uncommon, not even in the Solar System. Phobos is tidally locked to Mars. All four Galilean moons (Io, Europa, Callisto & Ganymede) are in synchronous orbit around Jupiter. Pluto and its moon Charon are tidally locked to each other as they orbit a common point in space.
There are GIFs in this article that demonstrate the process of tidal locking!
(Eclipse over Jackson, Wyoming by Ronan Donovan via NatGeo)
In August 2017 a total solar eclipse was witnessed by many, cutting across the United States. My family, here in Nashville, TN, was able to see it! Even though it was a Monday, and I should have had classes, my school was cancelled for the day and they even provided us with glasses to protect our eyes while we watched the eclipse. 13 year old me was ecstatic.
(My family and a couple friends on August 21, 2017, ready to see the eclipse.)
Seeing a solar eclipse is one of the coolest, weirdest experiences ever. Once in a lifetime for many. I’m hoping to make it more than that, though. One of the women in the picture with me and my parents lives in Texas. Not even a minute after the total eclipse ended, we started making plans to travel to Texas to see the next North American Total eclipse on April 8th, 2024. I’ll be turning 20 that month.
Did you get to see the eclipse in 2017? Do you plan to see the one in 2024? You should if you can manage!
The image above shows the position of the Moon, the Sun, and the Earth during each phase. The whole process( the Moon orbiting the Earth) takes about 29.5 days; and this time period makes Moon Phases.
The cause of Moon Phases is the Moon’s orbiting motion and the sun light. Like Earth, the Sun always illuminates half of the Moon while the other half remains dark, and the rotation of the Moon will change this dark side and bright side. But, the illuminated part that we can see depends on the Moon’s orbiting motion. As the position of the moon relative to the earth and the sun changes, the side illuminated by the sun sometimes faces the earth, and sometimes faces away from the earth; sometimes the bright side facing the earth is larger and sometimes smaller, thus appearing different moon phases.
In my first post, I briefly mentioned the international dark sky association. This association advocates for the protection of the night sky by leading the fight against light pollution through their efforts at the grassroots up to the international level.
Although cultures around the world have looked up at the night sky for millennia, in the united states, over eighty percent of us live in places where artificial light renders the milky way (the diffuse band of light from one of the arms of the milky way galaxy) unobservable. Consider donating to IDA or getting involved in campaigns that promote the responsible use of artificial outdoor light to help protect our night skies.
In Enchanted Rock State Natural Area (ERSNA), one of America’s 80+ international dark sky parks, the local sky showcases spectacular milky way views. Because the state has taken concerted action to minimize light pollution, observers can look up at an almost entirely unobstructed view of the night sky on clear nights. At a latitude of about 30 degrees North, this location allows visitors to spot recognizable constellations like Cassiopeia, the big and little dipper (Ursa Major and Minor), and Orion, as well as fainter constellations such as Cancer. For help locating these constellations and other celestial objects, I use the free version of the Night Sky IOS app. (Be sure to use the app in red mode to preserve your night vision!)
One of my favorite day time photos of ERSNA. Taken by me!
The night sky belongs to everyone and should be protected for years to come as part of humanity’s collective cultural history. To all my fellow city folk, visit ERSNA or any other dark sky park in your area and see what you’ve been missing! I’m definitely partial to the ones in Texas because the stars are indeed big and bright in the high and wide prairie skies. I’d love to hear about other people’s experiences with night sky observation! Please let me know if y’all have suggestions for star-gazing locations; I am always looking for new places to see the sky!
The Image above is an artists rendition of a phenomena known as a Gamma Ray Burst (GRB), where a star can project massive amounts of dangerous high energy light across the Cosmos. GRB’s are bit outside the scope of our solar system, so I will hold off on them for a bit; however the light they emit fits right in, and is just as interesting too.
Throughout history many assumed that light speed was immeasurable thus effectively infinite. However, in the 17th century while observing Io’s orbit around Jupiter, Danish astronomer Ole Roemer noticed a time discrepancy with Io’s orbital period as Earth approached Jupiter. It came to the point that he measured a 22 minute period difference between the closest and farthest point from Jupiter, which Roemer concluded that light has a finite speed. Through dividing the diameter of Earths orbit by the time difference, he estimated the speed of light to be 200,000 km/s.
Over the years this number has been refined to approximately 300,000 km/s, however, the precedent still remained that light has a finite speed, and with respect to the size of the universe its actually pretty slow. The closest star to the Sun is Proxima Centauri, which is around 4.2 light years away, meaning that it takes light four years to reach the closest sun to the star. The time it takes light to travel places only goes up with scale, taking nearly 9 years to reach us from Sirius the brightest star in the sky, 100,000 years to cross the entire Milky Way, and 2.5 million years to reach us from Andromeda, our neighboring galaxy.
The fact light takes time to travel does lead to an interesting quirk about the night sky: we are actually peering into the past. Imagine light to be a pebble, and stars a slingshot; if a rock was fired at you it would not be noticeable until you got hit, after the pebble was shot. Replace getting hit with observing, and that is essentially how we can see into the past. This principle is utilized by the James Webb Space Telescope to peer into the early universe. With the power to look at stars billions of light years away, we actually can see what the universe looked like billions of years ago.
Now returning to GRBs, some have superstitions that we may be hit by one of these in our lifetime or near future. However the closest likely candidates for these events are thousands of light years from our solar system, meaning that even under the astronomically low chance that one of these is aimed directly towards us, it would take many lifetimes for it to even reach us. So it’s safe to conclude that Earth will be GRB free for quite some time.
The Cosmic Calendar is a visualization of the timeline of the Universe that was popularized by astrophysicist Carl Sagan. In this timeline, the entire history of the Universe is scaled down to the length of one Earth year. As you can see from the picture above, January 1st is marked by the Big Bang and the rest of history flows out from there.
There are a few points of interest that I’d like to highlight on this calendar. After the occurrence of the Big Bang in January, our solar system didn’t form until August and life didn’t form until September. After this first appearance of single celled organisms, it took until December 17th for the first animals to appear(based on fossil records). Dinosaurs appeared around the 25th of December and ruled Earth until the 30th. The most striking thing to me however, is that all of human history occurs on the last day of the year. The whole of human evolutionary history happened over the span of a few hours on this cosmic calendar, and the recorded history of our kind occurs in about 20 seconds.
When you look at the universe this way it is extremely humbling to see how very small we are in every sense. Usually we just compare the Earth and the Moon and the solar system to the size of other objects and structures in the Universe, but when we compare our time to the rest of the Universe it’s almost more astounding. In some ways it can be depressing, honestly, to think of the nonexistent blip that your 80ish year life span will leave on this timeline. You would be unnoticeable next to literally anything else on there.
On the flip side of that though, I feel like this perspective can be reassuring in several ways. First, it is a reminder that whatever problems you’re dealing with, no matter how big they seem at the moment, are ultimately insignificant and will fade away and be lost to time. Second, it lets you see the world in a much more positive light, as any prejudices or Earthly conflicts lose meaning when you look down from so high. Lastly, I find it empowering to think that creatures that are insignificantly small in the universe can learn enough to understand how small they are. It’s a level of knowledge and self-awareness that is hard to accept, but we, as a species, have been brave enough to accept that knowledge and go out searching for more. In this way, I find the Cosmic Calendar to be much more uplifting than depressing and I think it is a very useful way to look at the Universe.
