A Brief History of Precession

Wikipedia – Earth’s Axial Precession

The priests of ancient Babylonia and Egypt were pioneer astronomers – they studied the sky, mapped constellations, and noted movements in both the Sun and the Moon – but, it was a Greek astronomer, Hipparchus, who made the first major new discovery in astronomy: precession. Comparing observations more than a century apart (particularly those done by Greek astronomers Timocharis and Aristyllus) with that of his own, Hipparchus noticed that Spica, and other bright stars in the sky, appeared to be displaced by 2 degrees relative to the autumnal equinox. Hence, after a few calculations, it did not take long for Hipparchus to ultimately conclude that the sky was moving and that the rate of this movement was no less than 1 degree per century (completing a full cycle in no less than 36,000 years) – a relatively accurate result in a time where astronomers still believed in the Geocentric model of our Solar System.

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Blog #1: Solar Eclipse Calendar

A solar eclipse is when the moon comes between the sun and the Earth and completely or partially blocks the light from the sun. This can only occur when the moon is at the nodes of its orbit and when its precession allows it to be in this position while being between the sun and Earth. Angular eclipses are when the moon is at its apogee and thus never covers the sun completely. However, at the moon’s perigee it is 400 times closer than the sun but 400 times smaller in actual size and thus can perfectly cover it. I did not get to see the “great American eclipse” because of a prior commitment, so I am very interested in finding the next total solar eclipses that would be easy to go to. I am not particularly interested in the partial ones because they do not entail the full majestic experience of the total eclipses (darkness descending, stars becoming visible, crickets chirping), and so I didn’t include them in my proceeding list.

North American Solar Eclipses 2001-2050

Additionally, total solar eclipses in the world from 2019-2030:

NASA
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The most easily accessible one to me is the 2024 eclipse that goes through the United States. However, I also would love to travel to New Zealand at some point in my life so perhaps the 2028 eclipse would be a perfect opportunity to go there.

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The Cosmic Calendar

Wikipedia

The Cosmic Calendar is the life of the universe condensed into a calendar year. It begins on January 1st at midnight and ends on December 31st just before midnight. The noteworthy time on this calendar is 8pm on December 1st: the start of human life. The universe is approximately 14 billion years old, so humans have only been alive for an extremely small portion of this time. Neil deGrasse Tyson hosted a documentary, that describes the life of the universe in detail and I highly recommend that you watch the documentary if you want to learn more about the Cosmic Calendar!

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Life on the Moon!!…Kinda

Does extraterrestrial life exist? Can living things even survive on another world? These are questions that have been asked for a long time and continue to be asked today. China tried to address the latter recently by experimenting with cotton seeds along with 6 other organisms, including potato seeds and fruit fly eggs, on their Chang’e 4 lander. The seeds were placed in a protective environment designed to keep them alive and shield them from the extreme conditions on the moon. When the seeds started to sprout, many were ecstatic. However, not even two weeks later the plants fell victim to the frigid temperatures present in the immediate lunar environment.

By China National Space Administration. Source: China Xinhua News – Cotton plant sprouting in its container on the moon

One day on the moon lasts approximately 29.5 days on Earth, so both day and night on the moon take place for about 2 weeks on Earth. This is why the plants could not survive for more than 2 weeks. Solar power was used for the experiment, and when the sunlight ran out after nighttime began there was no way to power the resources needed to sustain the plants. Even though there was no definite conclusion reached, it’s interesting to see some sort of proof that living things can potentially be transported, with the right biological and supportive resources, to another world and survive (even if for a short amount of time). Nonetheless, the rapid sprouting of the seeds definitely provided noticeable results that will be studied more. Updates about the lander’s findings will be posted on China Xinhua News’ twitter if you want to know more! Also check out SpaceTV for more news and some live streams regarding the Chang’e 4 lander.

By CNSA. Source: NPR – Chang’e 4 lander
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The Cosmic Calendar: Humanities Brief Reign

Calendar

In the grand scheme of the Universe, mankind has been around for an almost unfathomably short amount of time. Condensing the span of the universe into one calendar year we see clearly how our mark on the universe has barely just happened. All of what what we consider “modern” history takes place on December 31st, at 11:59, the LAST minute of the entire year. Our entire solar system only formed in September which means our Solar System has only seen about the last fourth of the universes history. Looking at the picture above we see that a human life of 100 years only lasts for 0.23 cosmic seconds. This gives a mind blowing visual of just how fleeting each individuals life spans in comparison to the very beginning of time. Humanity for the longest time has been considered the rulers of the world, but we’ve only been rulers for less than one minute. The dinosaurs lasted for about five days on the cosmic calendar. Where will humanity be in 5 days of the cosmic calendar?

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The Moon & Human Behavior

moon and human behavior
Does the moon alter our behavior?

In Chapter 2 we learned about the phases of the moon and important astronomical events such as solar and lunar eclipses. After reading this chapter, I thought back to the solar eclipse my freshman year when my friend said that the eclipse altered the behavior of animals and people within its range. At the time, it seemed silly that the phases of the moon could impact the behavior of anyone except a werewolf. After googling the topic, I found a Wikipedia Page that explained this phenomenon as the “Lunar Effect” and reported that many studies have concluded that there is no correlation between the moon phases and human behavior.

For example, the claim that a full moon causes increased crime or that fertility is influenced by the moon’s phases are all unsupported misconceptions. The article states that one possible cause for these misconceptions is that since the moon affects ocean tides it can likewise have an affect on the human body that is also made of mostly water. It is important to continue to look into various wives tales regarding astronomy so that our misconceptions don’t impact what we learn this semester. If any of you have heard any specific stories about the lunar cycle and human/animal behavior I would be interested to hear them!

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The Moon & Human Behavior

moon and human behavior
Does the moon alter our behavior?

In Chapter 2 we learned about the phases of the moon and important astronomical events such as solar and lunar eclipses. After reading this chapter, I thought back to the solar eclipse my freshman year when my friend said that the eclipse altered the behavior of animals and people within its range. At the time, it seemed silly that the phases of the moon could impact the behavior of anyone except a werewolf. After googling the topic, I found a Wikipedia Page that explained this phenomenon as the “Lunar Effect” and reported that many studies have concluded that there is no correlation between the moon phases and human behavior.

For example, the claim that a full moon causes increased crime or that fertility is influenced by the moon’s phases are all unsupported misconceptions. The article states that one possible cause for these misconceptions is that since the moon affects ocean tides it can likewise have an affect on the human body that is also made of mostly water. It is important to continue to look into various wives tales regarding astronomy so that our misconceptions don’t impact what we learn this semester. If any of you have heard any specific stories about the lunar cycle and human/animal behavior I would be interested to hear them!

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Power of Ten Reaction

I have a wall in my dorm room where I have started to post quotes that I love. After watching the Power of Ten video, I think I may have another quote that I will post to my wall collection. Philip Morrison, the narrator in the video, says: “This lonely scene, the galaxies like dust, is what most of space looks like. This emptiness is normal; the richness of our own neighborhood is the exception.”

I think this quote perfectly sums up the reaction I had when I watched the video. First off, I thought the video was brilliantly made for a video in 1977. When the video showed the line of how far light travels in one second, it really gave me a sense of how small we really are in the universe. The speed of light cannot even cover the length of the moon’s orbit in one second. In the grand scheme of things, the speed of light is nothing compared to the universe.

I was surprised that the Power of Ten would also show the scale of the universe at its most minuscule dimension. Although I am not pre-med and did not understand most of the diction used when describing objects sometimes smaller than even a cell, I was amazed that the technology was available back then to have even discovered all these amazing things. The video definitely does clarify some previous misconceptions that I had regarding scientific technology.

Morrison’s quote originally came from Charles and Ray Eames
Picture from here

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Milankovitch Cycle

Diagram detailing Earth’s precession, and the effect over time. Source

As we all know, the Earth experiences seasons each year. These are due to the tilt of Earth’s rotational axis, which causes certain areas of the earth to receive more direct sunlight during parts of the year, which has obvious effects on yearly climate.

Interestingly, the Earth’s seasons also shift around on the calendar year. Eventually, summer in the Northern Hemisphere will take place during December and January and the winter solstice will take place in July. This phenomenon is known as the Milankovitch Cycle.

Over a long period of time the Earth’s eccentric orbit around the Sun changes orientation due in part to the Apsidal precession of the Earth. In a normal orbit, the Earth is closest to the Sun during January but over time this will change. When the Earth is closer to the Sun, it receives a larger amount solar radiation. This small difference in solar radiation the Earth receives at the closest and furthest points creates a slight change in overall climate patterns. In a single year, this change is not terribly noticeable, but over the scale of 100,000 years, the changes in climate become more significant.

So what does solar radiation have to do with the Milankovitch cycle? As Earth’s eccentric orbit changes its orientation, different parts of the Earth receive the more direct solar radiation. This matters because it has a huge long term effect on global climate processes such as glaciation. Understanding that the position of Earth’s tilt will change over time can lead scientists to study periods of Earth’s history (such as the Ice Ages) in a different light, or make predictions about the long term climate future of the planet.

Source

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The Dark Side of the Moon

Source: Wikipedia

Besides a popular Pink Floyd album, what is “the dark side of the Moon”? Most people have not given much though to what it means or how it got its infamous name. For me the first image I get is of the moon I know and love turning over to the dark side of the force, much like Anakin from Star Wars when he becomes Darth Vader. In reality, however, there are no red lightsabers or Sith involved, just science…

The dark side of the Moon is a somewhat misleading name because it may lead a newbie astronomer to believe that the dark side of the Moon never actually has any sunlight touch it. It’s not a stretch to assume that the dark side would always be dark. What the dark side really is though, is the side of the moon that never reflects any light towards Earth. An observer from Earth can never see the dark side of the Moon, a more accurate name for the dark side of the Moon is “the far side of the Moon”. The far side of the Moon is the side of the Moon facing away from earth. The meaning of dark in the earlier name refers to the unseen or unknown nature of the side, rather than the absence of light on that side.

“But wait,” a newbie astronomer might ask, “since the Earth is constantly rotating, and the Moon is constantly orbiting the Earth, wouldn’t an observer from Earth eventually see all sides of the Moon?”

A person with this questions asks so rightly, but they are unaware that the moon is in synchronous rotation with the Earth. That means that the Moon spins on its axis at the same rate that is orbits the Earth. As the Moon orbits the Earth, it spins at just the right rate so that the same side of the Moon is always pointing towards Earth. It may seem like a phenomenal coincidence, but many moons that orbit close to their planet like ours are locked into synchronous orbits as well.

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