Blog #1: Why is our neighborhood special?

Posted on January 30, 2022 by nadiamcglynn

Over the course of the past two weeks, we have learned about our cosmic address (ch 1.1). Earth is a planet in the solar system in the Milky Way Galaxy. If I were going to send a letter to a different planet, I would probably make the return address on the envelope look something like this:

Nadia M.

Vanderbilt University,

Nashville, TN, USA, Earth, the Solar System,

the Milky Way Galaxy, the Local Group, Laniakea, the Universe

(Though these aliens would probably have different names for our part of the universe and might be a bit confused.)

But what about our place in the solar system makes life so conducive to earth? Why don’t we have cousins on Mars that we spend Thanksgiving with? Why doesn’t my uncle live on Venus?

This is probably because we exist in the Circumstellar Habitable Zone (CMZ), also known as the Goldilocks Zone. This is a region around a star in which planetary objects with atmospheres can support life and liquid water. Our terrestrial energy source, the Sun, is what defines the area that encompasses the CHZ.

Circumstellar Habitable Zone (wikipedia), includes Solar System planets and significant exoplanets and Proxima Centauri B

The photo above shows the Conservative Habitable Zone vs the Optimistic Habitable Zone for stars of different sizes. The Optimistic Habitable Zone accounts for planets that may have atmospheres that allow for a stronger greenhouse effect, like Venus, to maintain a temperature that supports liquid water. Venus, however, is too hot for liquid water and only supports water vapor.

The bounds of the CHZ are based on Earth’s distance from the sun (1 AU) and the radiation we receive from our star. When scientists are looking for other life in the Universe, narrowing down the possible locations to specific orbits around a star as well as certain planetary characteristics (surface pressure, temperature, atmospheric chemistry) certainly helps. In a course I took called Earth Systems Through Time, we even talked about the possibility of there being a Galactic Habitable Zone, or a distance from the center of the galaxy in which the development of a planet/solar system is possible, this would include thinking about the accumulation of heavy metals, enough time to evolve life, clemency, and more.

So it really seems that our cosmic address and our location in the solar system are pretty important for allowing life to flourish on Earth! If I want to send a letter to some aliens after all I will be sure to address it to the Goldilocks Zones of other solar systems!

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Blog 1:What Causes Seasons?

Posted on January 30, 2022 by Charles Littleton

It is commonly believed that the Earth’s distance from the Sun determines the seasons. The Earth’s orbit is lopsided and we are closer to the sun at different times in the year. In the northern hemisphere, we are closest to the sun when we have winter debunking the misconception that the distance to the sun affects the seasons.

Image From Earth Sky

The change in seasons is caused by the Earth’s tilt. The Earth’s tilt is with respect to the orbital plane of the Earth. When the Earth has one hemisphere tilted toward the sun, that hemisphere has summer. The opposite hemisphere it is winter. When the hemispheres are both 90 degrees away, we have an equinox. The entire world has 12 hours of daylight and 12 hours of night.

Image From Britanica
Image from Britannica
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Total Solar Eclipse

Posted on January 30, 2022 by brendanehle

On August 21st, 2017, the citizens of Oregon to South Carolina got to see a total Solar Eclipse. Although there is a total solar eclipse approximately every 18 months visible somewhere on Earth, the odds of the eclipse’s path passing over head where you can see it is much lower. Many mathematicians and scientist have tried to calculate the odds that a total solar eclipse will be visible to a specific spot on Earth and the consensus is about once every 375 years. Assuming one generation is 25 years, that means that 15 generations of your family could have come and gone without seeing what we saw in 2017. This is of course not a perfect calculation and there are places on Earth that are more likely to see a total solar eclipse but that does not take away from the magnitude of what we saw. The next total solar eclipse will be on April 8th, 2024, and pass through Mexico, the United States, and Canada. If you somehow missed the last solar eclipse, I would suggest you mark your calendar to see the next one.

This is a picture from the total solar eclipse in 1999.
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Blog#1 Cosmic Calendar

Posted on January 30, 2022 by Irene

I found the idea “Cosmic Calendar” particularly intriguing. Cosmic Calendar is a method to visualize the universe’s chronolUniverseling its currently understood age of 13.8 billion years to a single year (Therese). At this scale, there are 437.5 years per cosmic second, 1.575 million years per cosmic hour, and 37.8 million years per cosmic day (Therese). At this scale, on 12/25, dinosaurs were still the dominant species on Earth; on 12/31, human beings transited from the late bronze age to the early iron age; only on the very last second, on 12/31 23:59:58, Columbus voyaged to America and Renaissance happened in Europe. However, in this very last second, the previous 430 years before the present, human beings developed modern science, and science enabled us to humbly understand and explore our world non-stop.

The Cosmic Calendar from Wikipedia

According to Wikipedia, the Cosmic Calendar concept was popularized by Carl Sagan in his 1977 book The Dragons of Eden and his 1980 television series Cosmos (Click on the hyperlink to check Youtube video of cosmos). This reminds me of his famous “pale blue dot” quote:

“Look again at that dot. That’s here. That’s home. That’s us. On it, everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor, and explorer, every teacher of morals, every corrupt politician, every “superstar,” every “supreme leader,” every saint and sinner in the history of our species lived there–on a mote of dust suspended in a sunbeam.”

THE PALE BLUE DOT OF EARTH
“That’s here. That’s Home. That’s us.”
Image: NASA

“The cosmic perspective enables us to grasp, in the same thought, the large and the small.” The Cosmic Calendar reminds us of how short human beings have lived, and the pale blue dot reminds us of how small we are. Compared with the term “progress,” human beings’ scientific development is more suitable to be described as “explosion” at the scale of the cosmic Calendar. During this Big Bang of Technology and the Great Leap of Civilization, our intelligence spans the entire time and space, from the moment of the Big Bang to the visible UniveUniversem, the nearest white dwarf to the furthest cosmic horizon, nothing can stop us from exploring. All of this comes from our belief in success, reliance on science, and never-ending curiosity about fantastic nature.

Works Cited:

Therese Puyau Blanchard, 1995. ”The Universe At Your Fingertips Activity: Cosmic Calendar”. Astronomical Society of the Pacific.

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Precession Visualized

Posted on January 30, 2022 by alexbawa

After reading the initial chapters of our textbook, I was captivated by the fact that the way Earth’s tilt changes can be dumbed down to the movement of a spinning top. It’s always fascinating seeing physics work on any scale, so I was eager to look into the subject. After a bit of searching, I found an awesome video that not only provides an explanation of how precession works, but how it changes what stars are visible in the night sky. Embedded is one of my favorite visualizations.

Demonstration of precession in action – youtube.com

As illustrated in the image, Earth’s axis precesses on a 26,000 year cycle. Notably, this means that North will not always point at the same part of the sky, and therefore Polaris has not always been and will not always be an effective North Star. It won’t change noticeably in our lifetimes, but it’s fascinating to think that ancient peoples navigated with entirely different bearings.

An insight that the video provided that wasn’t explicitly talked about in the book is that Earth’s lack of a perfectly spherical shape heightens the effect of precession. With the center of mass thrown off by the bulge around the equator, gravity from the Sun and Moon are able to have an effective pull on tilted Earth.

Additionally, the fact that spin is maintained by angular momentum, which is proportional to mass, makes me wonder how an increase in mass would affect Earth’s precession. My prediction is that a more massive Earth spinning at the same rate would have a longer period of precession. This assertion is based on the fact that a higher angular momentum leads to less deviation from the already established axis of tilt, as indicated in the book.

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Blog Post 1 Speed of Light and Light Time Travel

Posted on January 30, 2022 by isaachuggins
The time it takes for the sun’s light to reach the Earth. Credit: physics.benjamin Steemit

Ever since I was a kid I always thought about how time travel would work. However, no as an adult, I realize that the delay of light reaching our eyes is technically time travel. Every instance you see around you is actually one trillionth of a second in the past since it took light time to reach your eye. In the same sense, the sun is 8 and a half minutes in the past as it currently is. Stars are viewed currently years if not hundreds of years in the past compared to what they look like right now. It even had me wondering a while ago, if an alien looked at our planet to try and talk to us, they would be looking at dinosaurs instead of humans. They could view the earth as it was 100 million years ago instead of us today.

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Powers of Ten and the scale of the Universe

Posted on January 30, 2022 by Johann West
The Powers of Ten video starts off with showing the viewer a couple on a picnic, which is a relatable reference point for the viewer that sets the scale for the rest of the video. Every ten seconds the video zooms out so that the box on screen is one more power of 10 meters bigger in size. For example we start off seeing a box 10^0 meters wide, which then moves to 10^1 after ten seconds, and 10^2 after 20 seconds, and so on. Within 2 minutes the Earth is lost from view, as small as a molecule would be to us, and not long after that the solar system becomes just a speck on the screen as well. Personally, while working in scales of the solar system often in school, this was amazing to see on screen but not a new realization. What was really mind blowing was seeing the milky way galaxy disappear off screen along with the rest of the local group and the virgo cluster. It emphasizes how truly microscopic Earth and the human species are on a cosmic scale. My first impression was that we are like bacteria growing on a rock. At the same time, I feel as though our tininess makes our knowledge of this scale even more impressive. A single cell organism has no concept of the Earth and its existence, however us, just as small in comparison to the universe, do have a concept of our size and likewise the vastness of the universe. To me this video shows how powerful humans really are.

After reaching a scale of 10^24 meters, the camera zooms back in all the way to a single proton, which is visible and in frame at a scale of 10^-16 meters. 10^+16 meters is roughly 10 light years. With these two numbers, it also frames humans as obviously very large in comparison to a proton, one of the smallest objects measurable. This shows that however we still are extremely small in the scope of the universe, we still are nowhere near being the smallest things in existence.

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#space

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Solstices and Equinoxes

Posted on January 30, 2022 by solarelizabeth
Earth in orbit: all four seasons.

The seasons change as Earth orbits the sun. Earth’s hemispheres receive different amounts of sunlight during each season because of the 23.5 degree tilt of Earth’s axis. When the Earth is at a point in its orbit that the northern hemisphere is tilted toward the sun, it is summer for the northern hemisphere. This is because the northern hemisphere receives the most direct sunlight and longer daylight hours, which allows it to heat up and stay warm. More sun rays cover a larger area, so the area is warmer.

The point in the year when the northern hemisphere is tilted most toward the sun and in turn receives the most sunlight is the June solstice. After that, the northern hemisphere is still tilted toward the sun, but less directly. As time passes, the northern hemisphere points less and less directly at the sun. The September equinox is when the northern hemisphere actually begins to be tilted away from the sun. The northern hemisphere receives less and less direct sunlight and begins to cool down. As the northern hemisphere cools down, it becomes fall and then winter, when the axis is pointed away from the sun.

The December solstice refers to the time of year when the northern hemisphere is pointed furthest away from the sun. It is winter because sun rays have to cover a larger area and thus do not heat it as much. After the December solstice, the season slowly becomes more moderate. Earth’s axis gradually becomes less pointed away from the sun, and the northern hemisphere slowly receives more and more direct sunlight. At the March equinox, the northern hemisphere actually becomes slightly tipped toward the sun and is no longer pointed away. The northern hemisphere gradually warms and receives more direct sunlight until the June solstice. 

The solstices are interesting because they refer to the moments when the Earth’s axis is tipped the furthest away or closest toward the sun. At both equinoxes, the northern and southern hemispheres are tilted neither away nor toward the sun. For instance, at the March equinox, the northern hemisphere changes from being tilted slightly away from the sun to slightly more tilted toward the sun and the southern hemisphere changes from being tilted slightly toward the sun to slightly tilted away from the sun. At the equinoxes, because of the Earth’s position in orbit and tilt neither away nor toward the sun, the sun rises directly due east and sets directly due west and the Earth receives equal amounts of daytime and nighttime. 

What do you think seasons would be like if Earth’s axis had no tilt? Do you think we would still have different seasons? Why?

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Nashville’s Partial Lunar Eclipse

Posted on January 30, 2022 by AndreaS
Near-total eclipse as seen on November 18 and 19

Last November, Nashville witnessed a near-total lunar eclipse. Many of you likely remember hearing about it on the news or even stayed up late to see it – but why the commotion? What made this particular event noteworthy? To understand this, we will first explore the phenomena of lunar eclipses in general.

Lunar eclipses occur when the sun, Earth, and moon align so that Earth’s shadow falls on the moon. If the moon is completely covered by Earth’s shadow, we refer to it as a total lunar eclipse. Any other scenario is referred to as a partial lunar eclipse. Given the specific conditions necessary, it is unsurprising that total lunar eclipses are less common than partial lunar eclipses.

Image of a partial lunar eclipse from NASA

The November, 2021 lunar eclipse was visible in Nashville from about 1:00 AM to 3:00 AM on the morning of the 19th. The entire duration of the eclipse was 3 hours and 28 minutes, the longest of the century. Additionally, although the eclipse was technically only a partial eclipse, Earth’s shadow enveloped up to 97% of the moon at the hight of the eclipse, so the view was still extraordinary and exhibited features of a total eclipse, namely the red coloration.

Interestingly enough, any given lunar eclipse is visible from anywhere on Earth experiencing night and where the moon has risen in the sky. On November 19th, I was in Nashville, but my family in Chicago could see the same event that I was seeing, despite being hundreds of miles away.

The November 19th, 2021 lunar eclipse. Photo by me

If you happened to miss the lunar eclipse last November, don’t worry! The next one visible from Nashville just so happens to be a total lunar eclipse, coming up on May 15, 2022. Happy viewing 🙂

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Can We Travel Faster Than the Speed of Light (like in Star Wars)?

Posted on January 30, 2022 by josephmaquino9
Figure 1. The Millenium Falcon traveling using a hyperspace jump.

One interesting question that has crossed many minds is, “Can humans travel at the speed of light?” Movies like Star Wars and Star Trek seem to believe that we can travel at, or even exceed, the speed of light (300,000,000 m/s) as they depict spaceships capable of jumping into hyperspace. In order to assess this question, Space.com takes the opportunity to analyze Albert Einstein’s most famous equation: E=mc<sup>2</sup>, where E is the energy of a particle, m is the particle’s mass, and c is the speed of light. What makes this equation interesting is that even the smallest of masses contain a large amount of energy.

Here is an interesting example. If you were in a car traveling at the same speed as an adjacent car on the interstate, you would say that the adjacent car is not moving relative to your own position. However, if your car traveled close to the speed of light, the light would seem as if it was traveling rapidly in the opposite direction. By this logic, Einstein makes the important statement that light travels at the same speed regardless of an observer’s motion and the time or place at which their measurement of the light’s speed is taken.

The combination of E=mc<sup>2</sup> and the example above indicates that humans-or really anything with mass-cannot attain or surpass the speed of light as this would imply that there is infinite mass. Additionally, something of infinite mass would require infinite energy to drive this mass forward. So, unfortunately for those longing for space vehicles capable of jumping into hyperspeed, they will have to live with the reality that reaching the speed of light is not a possibility.

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