The Speed of Light/Light Travel Time – Cameron Klein

Posted on January 21, 2024 by Cameron Klein
LinkedIn Article: How Long Does It Take Sunlight to Reach Earth?

Before beginning this course, I was familiar with the term light-year, but not in the way that it is truly meant to be used. When talking to members of my family, it is a common expression for us to say, “It’s going to take me lightyears to clean my room!” or “Doing my laundry is going to take me lightyears!” However, after our first few classes together, I came to realize that this is not at all what the true definition of a lightyear is. As a matter of fact, a light-year is a measure of distance and NOT an amount of time. One light-year is the distance that light can travel in one year: 10 trillion kilometers.

Before enrolling in this course, I had absolutely no idea how fast that light could travel. It takes light about 1 second to reach Earth from the Moon. How crazy is that? Not only that, but it takes light about 8 minutes to reach Earth from the Sun. Now, I’m not going to lie…that takes a little longer than I previously expected. However, that is due to the immense size of our solar system itself. Our solar system, galaxy, and universe are so enormous that when we see a planet or a far-off galaxy, we are looking back in time. This is another way to employ the term of a light-year.

The farther away an object in space is that we are looking at, the further back in time we are looking. That is a totally crazy statement. For example, according to The Cosmic Perspective by Jeffrey O. Bennett, Megan O. Donahue, Nicholas Schneider, and Mark Voit, Sirius, a bright star, is 8 light-years away. This means that as we are looking at it, we are seeing it as it appeared 8 years ago. To give more examples, the Orion Nebula (a cloud where stars and planets form) is 1350 light-years away from us and the Andromeda Galaxy (the closest complete galaxy to the Milky Way) is 2.5 million light-years away. When I found out that looking at far away objects meant that I was looking backwards in time, I was completely flabbergasted. I had so much fun learning about this topic, and I cannot wait to continue my learning as the semester continues! How fast did you all think that light moved before this class?

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Night Sky App

Posted on January 21, 2024 by Maddy Pollard
iDB

I downloaded the Night Sky app at the beginning of this semester, before I even knew I would be taking this class. On a late night walk back from the library, my friend and I noticed an unusually bright star in the sky. Interested to find out what it was, I downloaded this app and discovered we were looking at Jupiter. The app sat unused on my home screen for quite some time until this class prompted me to reopen it. 

Inside of the app you can set your location and it will show you the night sky from wherever you are. Point the phone in different directions and the screen will display everything in the sky; planets, stars, the Moon and the Sun, rocket bodies, constellations, and more. The app also shows you the horizon line, so you are able to differentiate what is in your local sky versus what is in the sky on the opposite side of Earth. The search function is useful to pinpoint the location of any specific object you want to see in the sky. Furthermore, the app features articles and timelines all having to do with space that are interesting to look at. You can pay to unlock even more features, but I think the free version is just as fun to play around with. This app has been a really fun way to further interact with the material we’ve learned in class, I highly recommend it!

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Blog 1: Our Expanding Universe

Posted on January 21, 2024 by Charles Knoll

Our expanding universe is a captivating cosmic phenomenon that continues to unfold in the vastness of space. Galaxies throughout the cosmos are in a state of expansion, distancing themselves from one another as space itself expands between them. From our vantage point on Earth, nearly every galaxy beyond our Local Cluster is gradually moving away and it appears the farther away the galaxy, the faster the rate at which it expands. Scientists call the source of this acceleration and movement dark energy, however, they still aren’t completely sure how dark energy works. While these cosmic shifts are invisible to the naked eye, astronomers utilize Doppler shifts to measure them and the rate at which they are expanding accurately. 

More specifically, researchers use the wavelength of light to determine whether an object is approaching or receding from Earth. A shorter wavelength, denoted as a “blue shift,” signifies the object is moving towards Earth. Conversely, a longer wavelength, identified as a “redshift,” indicates the object is moving away from Earth. Moreover, the greater the speed of the object in its trajectory, the more drastic the shift in wavelength becomes.

Furthermore, this observational technique has allowed scientists and astronomers to estimate that our universe is approximately 14 billion years old. It is exciting to think how different our universe will look in the billions of years to come. 

The expansion of the universe from the Big Bang to the present. Digital illustration.

Sources: Photo, Dark Energy, Doppler Shift

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THE COSMIC CALENDAR

Posted on January 21, 2024 by katie shapiro

The Evolution of the Universe from the Big Bang to Modern Day Humans

The Evolution of the Universe from the Big Bang to Modern Day. By Pablo Carlos Budassi

    When I first started this course, I knew that our universe was very old, however, I didn’t understand the depth to how long it really was. Our universe has evolved significantly from the original Big Bang that occurred approximately 14 billion years ago to modern day Homo sapiens that inhabit Earth today. In the span of time, 14 billion years is an astronomically long time. In fact, with the human mind, it is difficult to put this amount of time into perspective. Therefore, astronomers have created a type of calendar, called the Cosmic Calendar, to condense these 14 billion years into the span of a singular year. For example, the beginning of the universe is said to have began on January 1st, according to the Cosmic Calendar. Moreover, it is said that the hominids have evolved at around 10:30PM on December 31st and modern day humans evolved in the first second of New Years.
    This way of thinking about the universe was complicated at first because it is hard to understand that modern day humans have only been around for a second, in relation to the rest of the universe. However, condensing the universe to a singular year is a valuable tool because it allows us to understand the true length of how long the universe has been around. Prior to this course, I believed that dinosaurs had been around for less time than humans, however, according to the cosmic calendar, dinosaurs have been around for approximately 4 days, while the evolution of humans have only been a few seconds. This was fascinating because it not only demonstrates that humans have been around for such a short time in relation to the rest of the universe, it also emphasizes the fact that our species have become significantly advanced. Specifically, the significant amount of technology advancements that has come about from our generations, especially space exploration technology. It makes me think about the fact that in the next second, what other advancements are humans going to make? Additionally, at what point in the comic calendar will new species come about? This calendar is such a great way to not only put time into perspective, but it also allows humans to try to infer what may happen in the next second of the cosmic calendar.

The Cosmic Timeline: The Big Bang- Modern Day. By Carl Sagan

astro2110 blog1 me time

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Celestial Navigation – Blog 1

Posted on January 20, 2024 by Owen Purcell
https://timeandnavigation.si.edu/multimedia-asset/sextant

People have used the stars to navigate for millennia, with expert sailors learning the geography of the sky above and using it as a very powerful tool. Though much less necessary in the modern day, given our access to GPS, people still take an interest to learn how to navigate using celestial bodies. These people often can navigate with the use a sextant, a watch, some paper, a calculator, and a map, using some version of techniques that are hundreds of years old. 

Firstly, almost all of the math used in celestial navigation is based in trigonometry, meaning anyone who graduated high school could learn how to do it, and the math has been the same for many hundreds of years, despite the enormous advances made in mathematics. The stars are basically assumed to be fixed on a dome surrounding the earth, which rotates inside, and the star’s position is used to discern what is directly beneath it. Thus, the sailor calculates his distance from the star, or rather, the point on earth directly beneath the star. Using three separate points can give a high degree of accuracy as to where the sailor is on earth. 

The most interesting tidbit of information to me, is how celestial navigators account for “dip” and refraction. Dip is the difference between the real horizon and the apparent horizon caused by the hight of the observer. The formula used for dip is Dip=1.76√Height. This is, of course, an estimation, but I found it so interesting that theoretical accuracy is not the primary concern, but rather, simplicity of usage, and this is mirrored in refraction as well (Refraction=0.96/tan(Altitude)). There are also all kinds of tips and tricks for corrections due to temperature, pressure, and high altitude.

I think learning how to use the sky like a tradesman, as well as an enthusiast or an academic, can greatly expand your appreciation for its relationship with our lives down on earth.

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Blog 1

Posted on January 20, 2024 by Nicholas Fleisher

As someone who knew very little about anything astronomy related prior to this course, I was enamored by the first two chapters of the textbook. There were a few topics in particular that I had always been curious about but never got the chance to learn about, one of which being how seasons work. I knew that the early went through one full orbit around the sun and that earth goes through a full rotation once per every 24 hours, however, I fell victim to the common misconception outlined in the textbook that seasons happen because of the variations in the earth’s distance from the sun. It’s interested to me that seasons have nothing to do with the distance, but rather, it is the tilt on Earth’s axis that causes sunlight to fall differently on earth at different times of the year, but the sun remains pointed at Polaris throughout the year. For example, in June, the tilt causes sunlight to strike through the Northern hemisphere at a steeper angle and a shallower angle at the Southern hemisphere, causing summer in the north. The beginning of the summer is the maximum solstice, the steepest angle, so it has the most sunlight. 

Another concept I enjoyed learning about was the idea of the celestial sphere. In this sphere, Earth is at the center, the North celestial pole is directly above the earth’s north pole, the South celestial pole is directly over Earth’s south pole, the Celestial equator is the projection of Earth’s equator in space, and the Ecliptic is the path the sun follows. The celestial sphere gives us a good idea of stars that are visible depending on the location you are at on Earth. The stars north of the celestial pole ar circumpolar because they remain perpetually above the horizon, circling (counterclockwise) around the North celestial pole everyday. The altitude of the celestial pole in the sky is equivalent to the latitude, which measures north-south position.

Image source

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Blog 1: size of the universe

Posted on January 18, 2024 by matthewastro

The size and scale of our universe is nearly incomprehensible. While many comparisons have been formulated to describe certain cosmological distance (such as from the Earth to the Moon, and so on), I believe that only one can even claim to do justice to the size of the universe. To gain even a slight comprehension of our universe’s scale, we should examine the amount of time it take light to travel its “diameter.” Light is the fastest “thing” in the universe, usually. We know this from not only our experimental and practical observations, but also from our theoretical models. Einstein’s Theory of Special Relativity tells us that nothing can surpass the speed at which light travels through a vacuum.

With this said, our universe is estimated to be approximately 13.8 billion years old, which means that can observe light from up to 13.8 light-years away. This means that our observable universe is about 27.6 billion light-years in diameter. Light, which we understand to travel about 671 million miles per hour, cannot travel the hypothetical “end-to-end” distance of the observable universe, which is thought to be approximately 93 BILLION light-years. How is this possible? If light is the fastest type of matter/energy in our universe, then how could the radius (in light-years) be over three times the age of the universe? The answer is that the very fabric of the universe, spacetime, is expanding faster than light can travel and in all directions. (The fabric of the universe is not bound by the limitations of lightspeed, which is an upper limit on objects moving through space, but not space itself.) If the universe continues to expand at this rate, light will never travel the universe from end to end. There really is not way of doing justice to the universe’s incomprehensible massiveness. There is nothing to compare our rapidly expanding universe to.

A visual representation showing the approximated dimensions of our observable universe. By Andrew Z. Colvin on Wikimedia Commons.
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Intro post

Posted on January 18, 2024 by Ayden Harris

I am excited to learn about the solar system this semester! I have taken Astronomy which inspired me to become a physics major! You can learn more about the physics major at Vanderbilt here. The attached image is My buddy and I playing volleyball 

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The start of my Journey

Posted on January 18, 2024 by Muhammad Israr

Greetings,

My name is Muhammad Israr. I have a long-standing interest in night sky photography, which led me to take this class. Additionally, as someone who enjoys reading about history, I’m particularly fascinated by the ancient Muslim astronomers. Their legacy inspires me as I study astronomy at Vanderbilt University, exploring the universe and pursuing my passion, much like those historical figures once did. The pic bellow is one of my works. It is a picture of Falls Creek state park of Tennessee.

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First Astro Blog Post

Posted on January 18, 2024 by Justin Kim

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