It is difficult to truly grasp the size and scale of our universe. And while using units like light years might be helpful in some cases, it can also be helpful to put things in a scale that is more common in everyday life. This image helps me understand the scale of the universe in terms of units in meters. The smallest unit femtometers (fm) is equal to 10^-15m. Each subsequent photo is 1000x bigger than the last ending with Ym which is 10^24m. It is interesting to see that in terms of scale, the smallest picture, which is the nucleus of an oxygen atom, is to us, as we are to an Oort cloud. In other words, there is a 10^15x difference between an oxygen nucleus and us, and a 10^15x difference between us and an Oort cloud. Even with this aid, I still struggle to grasp the sheer size of it all. I am interested in what others think about this, and what ways you try to put everything into perspective to understand it.
By me – this is a photo of my sister and I at our favorite beach in Nantucket Island. This is where I first became fascinated with space; there is little light pollution here and for as far back as I can remember, I have stared at the night sky for hours at a time in awe of the complexity of the universe. While I have never been there, this is a link to an observatory on Nantucket that discusses the island’s beauty and amazing conditions for stargazing.
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In 1905, Albert Einstein took the first crack at the Newtonian foundational physics. In his paper on special relativity, Albert Einstein postulated that the speed of light, c, is constant in all inertial reference frames. Assume that a person on a bicycle is holding a flashlight and moving at a constant speed relative to someone who is standing still on the sidewalk. Then, both people measure the speed of light, c, to be approximately 300,000 km/s. Relative to the person standing still on the sidewalk, the light coming out the flashlight still moves at 300,000 km/s, not 300,000 km/s plus the velocity of the person holding a flashlight while cycling. This turns out to be extremely important consequences. By keeping the speed of light the same, the only two variables that can change are the distance and time that is traveled. The longer the distance, the longer the time it takes for the light to traverse the distance. The shorter the distance, the shorter the time it takes for light to travel. If there is any distance between you, the observer, and the object, then it will take some time for the immediately emitted light to travel from the object and in to your eyes. Essentially, there is a time lag between the observer and what you observe. Therefore, the light that reaches you is in fact light that was emitted some time ago. Therefore, you’re actually peering into the past! By observing different types of light that is radiated in the universe, we can learn about the origins of the universe. The oldest light that is observed is Cosmic Microwave Background (CMB).
The CMB, as it turns out, is a relic of the early universe. The CMB tells us how much baryonic matter and dark matter there was in the early universe. The CMB also helps us model how stars and galaxies formed, a crucial step in understanding our cosmic address.
The constancy of the speed of light has enabled us to peer back into the past to observe, analyze, and theorize about our ever elusive origins. Perhaps in another blog I might discuss the philosophical implications of light. But as it stands, a universal constant speed and its ability to shed light on the birth of our galaxy is mind-blowing enough for one blog post.
Imagine if the entire history of the universe could be squeezed into a single calendar year, providing a perspective of how much time has truly passed in this universe. Enter the cosmic calendar, a concept introduced by the astronomer Carl Sagan. Within the cosmic calendar, each month corresponds to over 1 billion years, allowing us to fully understand staggering age of the cosmos. To summarize and put things in simple terms, picture the Big Bang as the calendar’s January 1, and the emergence of Earth and life unfolding in the final moments of December 31. This detail, where life emerges in the final minutes of December 31st, emphasizes the recent appearance of humans relative to other events. As we move through the cosmic calendar, we witness the birth of stars, the formation of galaxies, and the unfolding drama of cosmic evolution over billions and billions of years.
Here are some more specifics, taken from the diagram below:
Modern humans evolved with 8 minutes left in the cosmic calendar.
The end of the last ice age came within the final minute of the cosmic calendar.
The cold war came with JUST .2 seconds left.
It’s a simple reminder that our presence is just a brief moment in the immense cosmic story.
The Universe is also used as a reference point to display somethings enormity. “I love you more than anything in the world” is massively trumped by “I love you more than anything in the Universe.” But what does this really mean? How much can the universe really hold? How big is it REALLY? The Observable1 Universe itself is over 92 billion light years across. 92 BILLION!! For a brief scaling reference, just our Milky Way Galaxy (huge, by the way) is merely 100,000 light years across. Our Observable Universe is 920,000 times bigger than The Milky Way. Observed light from this far away could predate even the Milky Way itself. It would be 92 billion years old after all. With how advanced our science and technology is, even now it is hard to comprehend the sheer vastness of the Universe but it is a fascinating topic that I hope to learn more about.
This is just obervable, who knows how much we do not know. ︎
The speed of light is a fascinating topic that has significance from everyday life to the vast expanse of the cosmos. The speed of light is the speed at which light travels through a medium, and for a vacuum, this speed has been defined as 299,792,458 m/s. This speed is almost incomprehensible to us due to its magnitude. For example, if you moved at the speed of light, you would circumnavigate the equator approximately 7.5 times in one second.
Because of this finite speed, everything we observe is a glimpse into the past. This is particularly applicable to astronomy due to the vast distance of objects observed. Astronomers are able to use this principle and look further back in time by studying more distant objects. Our nearest neighbor, the Andromeda Galaxy, is 2 million light years away, meaning we see what it looked like 2 million years ago. This allows astronomers to garner a better understanding of the universe’s history.
Along with visible light, all forms of electromagnetic radiation travel at the speed of light. Therefore, this speed governs both the light viewed from distant stars on Earth, as well as communications with distant space probes. NASA’s Voyager 1 probe, the most distant satellite in interstellar space which was launched in 1977, takes nearly a day (22.5) hours for a transmission to reach the spacecraft. This delay is due to the spacecraft being more than 15 billion miles away from Earth, and the speed of light, or electromagnetic radiation in this case, sets the ultimate limit of the speed of these communications. This is even applicable to the communication delay during the Apollo missions, where it took 1.255 seconds for communications to reach the moon from Earth, as seen in the graphic below.
One thing I love about the nighttime is getting to see the different phases of the Moon in different times of its cycle. The Moon cycle consists of 8 phases as you can see in the picture below, and lasts 29.5 days, which is around one month! In this period, we see the Moon go from new moon (this is when the Moon is dark to us) as it waxes/increases up to full moon (a beautiful, completely round moon!), and then as the full moon wanes/decreases down to darkness. One side of the moon is always facing the Sun because sunlight hits Earth and Moon from the same direction. During different positions of the Moon’s orbit, we will see a different shape of light/dark on the moon. Although we see different phases, we always see the same face of the moon! This is because the Moon’s orbit around the Earth and its rotation around its axis take around the same time! We call this characteristic “synchronous rotation”, and it happens because of the Earth’s gravity affecting the moon.
A different perspective: if you were on the side of the moon facing Earth, you would see “phases” of the Earth that are the opposite of what Earth is seeing the Moon as! So if the Moon was in new moon phase, the view of the Earth from the Moon would be a “full Earth!”
One thing I learned from our textbook (“The Cosmic Perspective” ) that I didn’t realize before was that the phase of the Moon also determines what time of the day we get to see the moon. For example, a full moon rises at sunset and a first-quarter moon rises around noon. That also determines when it sets.
No matter what, our Moon will always be there with us. Even when you don’t see her! (did you ever wonder why the Moon’s following you? it’s because the Moon is a significant distance away from us, and we can relate this to our knowledge on angular distance!) ☾ So, if you’ve read all the way down here, I would love to know what your favorite moon phase is! Mine would definitely be the full moon, because it makes the night so bright!! ⋆⁺₊⋆ ☾⋆⁺₊⋆
The speed of light is around 300,000,000 meters per second. It’s so fast that it can circle the Earth 7.5 times in one second. I always wondered if humans can ever achieve speeds the same as light, but we’ve only managed to go 176,462 meters per second with the Nasa Parker Solar Probe. More on that can be read here. But then again, can a human even handle moving at light speed? If pilots can get unconscious moving in fighter jets going at 222 to 388 meters per second, then it seems unlikely we’ll be able to handle 300,000,000 meters per second.
We always see in sci-fi movies and tv shows ships moving at the speed of light or even past it with no issues. This would be amazing to accomplish in real life. Being able to travel to different stars and planets in only in a matter of minutes or hours instead of billions of years. However, if we look at the current growth rate of our technologies, we still have years to centuries worth of growth to cover.
We can dream and we can hope to one day achieve these speeds, however it is not likely we will see this in our lifetimes.
Earth-sun relationship on the Solstices/Equinoxes!!
Traditionally, the Solstices mark the beginning of the most treacherous seasons. Being from Miami, when the summer solstice came around everyone always knew that the days would only get hotter. Once the winter solstice hit, we always prayed that there would be some form of respite (news flash, rarely was). Arguably, this is the worst part about living in a city in the south. The distribution of sunlight that causes seasons in most other parts of the world, does not change nearly as much for the equator and the area immediately north and south of it. So while Miami does get more seasons than their Southern neighbors that lie much closer or on the equator, it still experiences intense sunlight during the summer months and still good amounts of sunshine in the winter.
The Solstices and equinoxes are interesting markers, because while I had always marked them as the gateway to the seasons, I did not realize that they were directly related to Earth’s tilt and its relationship to the Sun. Honestly, I believed that the dates were almost arbitrary, decided based on our calendar by people who just realized that it starts to get really hot in June and really cold in December. Learning that the solstices really mark the day in which the Earth is in the position to receive the most direct sunlight in the Northern Hemisphere (June) and Southern Hemisphere (December), made me ponder why these dates were not the most extreme of the year? Putting this question in the vast context of space easily answers it, as it takes time for the sun’s rays to warm up the earth over all those light years. The order of solstices and equinoxes soon began to click, as I was able to picture the Earth rotating around the sun with differing distributions of light year-round. In spring and fall, we mark the day that both hemispheres swap light distributions from the sun, which then results in the warming/cooling of their regions. However, it did not solve my frustration with my hometown being so hot. Guess I can’t move the earth huh?
For as long as I can remember, I have been fascinated by the vastness of the Universe and how everything around us has been untouched by humans. Everyone lives on Earth (unless you are an alien…). Yet, Earth is only one of eight planets in our solar system. Our solar system is centered around the Sun. The Sun is only one of 400 BILLION stars in our galaxy, which we call the Milky Way.
But how large is the Milky Way in actuality? For me to begin to explain the size of objects on a cosmic scale, let me first introduce the concept of the light-year. Despite its misleading name, a light-year is a measure of distance. It refers to the distance which light moves in one year. One light-year is roughly 6 trillion miles. Our Milky Way is huge. It has a diameter of 100,000 light-years, or 600 quadrillion miles! 2.14 x 10^14 continental United Sates could fit in the diameter of the Milky Way. Now imagine: our Milky Way represents merely one of BILLIONS of other galaxies in the universe! That’s crazy!
It is difficult not to be amazed by the incredible size of the universe. Personally, I find the large scale to be exciting. What exists outside of Earth? What can we learn from other planets, stars, and galaxies? However, I am also aware that the size of the universe can also be intimidating. It highlights how small and insignificant humans are on a galactic scale. How do you feel knowing the size of the universe? Does it make you excited or nervous?
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