The scale, and “end points” to our universe, is widely unknown. Because as humans have not ventured or seen any type of universe ending barrier, the question of infinity comes into play. One common assumption that a human naïve to the theories of astronomy would have is that the universe is never ending. This, however, provides no insight nor bounds to the volume of our universe. Instead, astronomers track the end of the universe based on the farthest light we can see. The image above comes from the Hubble telescope and pictures remote galaxy’s billions of light years away. As of right now, the edge of the observable universe is 47 billion light years away. There is absolutely no evidence that this, however, the edge of the universe. It is odd how the length is depicted in this way, because this by no means is the size of the universe.
The universe is so massive that it can be difficult for humans to comprehend its scale, so I will break it down using something that we can easily understand. Earth is 1 AU (astronomical unit) from the sun or 150 million KM. If a human were travelling this distance in a car at 100 miles per hour, it would take approximately 41,166 days or 112 years. Now this doesn’t seem too crazy; however, the distance from the earth to the sun pales in comparison to the size of the entire universe. The distance from the sun to the edge of the solar system is roughly 145 billion KM. When travelling from the sun to the edge of our solar system at the same pace it would take 3.7 million days or roughly 10,000 years. This is substantially longer than a human lifetime, but let’s go even further out. From the center of the Milky Way (our galaxy) to its edge it is 500 quadrillion KM. At 100 miles per hour, it would take 350 billion years to reach the edge of the Milky Way. But the universe can’t be much bigger than that right? Wrong. There are billions of galaxies in the observable universe and the Milky Way is just one. From the center of the observable universe to its edge is 4.4 x 10^23 KM. To travel this distance at 100 miles per hour would take approximately 3.1 x 10^17 years or 310 quintillion years. While our solar system and even our planet appear to be giant from a human perspective, they are merely a speck in the grandiose universe we inhabit.
By far one the most interesting aspect of understanding the cosmos for me revolved around the cosmic calendar. Essentially, The Cosmic Calendar takes the time span of the entire universe and condenses it into single year based on the calendar. Just like any other calendar year, time starts on January first and ends at 11:59 on December 31st. Now at the surface this may not seem very interesting, but when you take a closer look, there are many shocking facts and aspects of it. With the universe being around 13.8 billion years old all condensed in one calendar year, it is crazy to see how many things can occur in even one day of the year. For reference, one day can equate to roughly 40 million years, so of course many things can occur. Another particularly shocking revelation made apparent by The Cosmic Calendar is that dinosaurs survived roughly a week relative to the calendar while humans only appear on the last day of the year and fairly late in the day as well. This just shows in grand fashion the extremely long period of time the dinosaurs ruled the earth and how late and short period of time in which our ancestors came into fruition. The picture shown below helps give a visual on these timelines.
Based on this calendar it is so fascinating to see just how short a period of time humans have existed in the grand scheme of things, just one of the reasons why I am eager to learn more about universe around us.
Our universe is composed of two: the observable and entire. There is a distinction between the two because light takes time to travel through space. From what we know, the observable universe is 13.8 billion years old. Already, that’s an intimidating age, but the thought of the entire universe makes it even more intimidating. There is so much to learn about the universe.
How could there possibly be so much that exists that I simply cannot see?
It is hard to realize how small we actually are. The world is already so big compared to us. The circumference of Earth is roughly 40,075 kilometers. The sun is roughly 4.366 kilometers across. The Milky Way galaxy is roughly 102,000 light years thick. The thought of how large the universe is daunting, but it’s important to realize this. It’s comforting to know that so much around us has been around for so long that we can’t wrap our minds around. I used to not like the feeling of awareness around my small existence, but it’s freeing to know that there are so much bigger things that will outlive me and anyone else I know. It goes to show that my worries don’t hold as much as I think they do.
Hello everyone, my name is Jadon Roy. This is a picture of me and my best friend who visited me in Nashville last semester. We are from Louisiana so it is always fun when he visits!
On August 21, 2017, my family and I drove from Atlanta, Georgia to Clemson University in South Carolina to witness the solar eclipse in totality. Atlanta reached 97% totality, but Clemson reached complete totality:
At about 2:37 PM, the moon completely covered the sun, positioning itself perfectly between earth and the sun and casting a shadow directly over Clemson. The sky darkened considerably, cheers erupted from all who attended, and the sun’s corona became visible around the dark disk of the moon. Below are two images I captured of the event, the first of the sun’s corona peeking around the moon, and the second of the sky and landscape to give an idea of how much light the moon truly blocked. As you look at this image, remember that this was taken at about 2:37 PM, when the sky should be almost as bright as ever.
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!
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.
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.
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.
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.
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.
