This morning I woke up to a beautiful sunrise (pictured) and got to pondering how the colors came to be. Apparently, they result from a process called scattering, a process by which small particles in the the atmosphere change the direction of light rays, causing them to scatter.
Although scattering affects the color of light emitted in the sky, the details are determined by the wavelength of the light and size of the particle in that the long-wavelength red are scattered by molecules in the air much less than other colors of the spectrum.
We see sunsets and sunrises as a result of the sun being low on the horizon where sunlight passes through more air at those times of day.
The blue light seen throughout the day is scattered away from our eyes, leaving the more orange and red light to pass through.
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How did you first picture the universe? Before being taught in school or at home what the universe was like, we often start to wonder about the world around us. This phase in a child’s life often leads to parents being questioned about almost everything. Questions range from why the sky is blue, why is candy unhealthy, how hot is the sun, to even how far the stars are. These questions are often formed because our young minds are attempting to make sense of the mysteries surrounding us. Today we are surrounded by technology and are able to observe the universe around us with incredible accuracy, allowing us to use science and reasoning to piece together how things work. We weren’t always so well equipped to answer these questions, but not having the right tools didn’t stop ancient thinkers from asking or trying to answer questions about the universe.
Ancient Greece is given a large amount of credit for starting what we call modern science. Ancient Greece is renowned for its philosopher, who were among the first to publicly try to understand how things work without using supernatural or religious ideas. The origin of Greek science is attributed to Thales, who believed that the universe was mostly water, and the Earth was a flat disk floating in an infinite ocean. This idea didn’t catch on, but it suggested that the universe was comprehensible. This likely motivated others after him to continue theorizing our place in the universe. Thales did, however, theorize and predict that a solar eclipse would occur. He did not give a prediction date, but his grasp on the universe was ahead of many around him.
The Greeks largely believed in the geocentric model, which means they thought the Earth was the center of the universe. The Earth being the center of everything played an integral role in Aristotle’s physics. When explaining how elements work, he used their behavior in relation to the Earth to explain their “natural motions.” This lead him to saying that Fire moved away from the Earth, earth returned to Earth, water naturally goes towards Earth, and air rises away from Earth.
Aristotle’s physics and the geocentric model was widely accepted for a hundreds of years until the Copernican Revolution. Copernicus, Tycho, and Kepler would all contribute to a more modern understanding of the universe and a transition from the geocentric model to the heliocentric model. The heliocentric model is what we use today, and places the Sun in the center of the solar system.
We haven’t always had the answers to questions like what is our place in the universe, but that hasn’t stopped us from trying to reason and theorize answers. Even with all our modern day tools and techniques we still can’t answer every question we have. Topics like dark energy still puzzle us, leading to attempts to theorize and reason what it is or how it works. Maybe one day we’ll have the proper technology to observe it, and we will look back on contemporary theories the same way we look at Ancient Greek Philosophers today.
After completing the homework assignment on historical astronomers, I found myself diving into the internet to find out more on the astronomers we researched. This trip down the wormhole of the internet led me to an article about Isaac Newton, titled: “What if there was no Apple tree?” This article ponders what would have happened if Isaac Newton had not observed the apples falling from his tree and asking the question: what force causes this downward motion? As the picture above shows, Newton would have never generated some of the founding principles of physics and astronomy if his face had been locked in on an iPhone rather than looking up and pondering the great questions of life.
These thoughts beg the question: have we as a society lost out on possibly world-altering discoveries due to the loss of some of our greatest minds to technology? Newton’s discoveries and laws advanced science in a way unmatched by most in the history of our civilization. By how many years did Newton’s discoveries advance scientific knowledge? By how many years have we fallen behind as our family, friends, classmates and people around dive further into their phones and further from true thought encouraging the advancement of knowledge?
These questions must be asked as we truly are losing out on advancement. There are many great minds throughout the world making unbelievable advancements, but how much further could we as a collective society go if we spent less time looking at our iPhones and more time watching the apples fall?
Compiled by Reddit User u/Spiritgreen from Hall’s Harbour webcams (Right click on video and select “loop” while playing to continuously loop)
The above GIF shows the changing tides in a unique manner, by splicing together pictures taken throughout an entire day, at 20 minute intervals! The resulting effect is that it looks as if time is spiraling around the image. You can also see both pairs of high and low tides, one set during the day and one set during the night.
Unless you’ve lived by or frequently visited shores, you’ve probably never had to think about the tides much. Sure, the concept of tides is fairly well known by many, but how much of a difference does it make?
Well, as the video shows, quite a lot! Before I had watched time-lapses of tidal behavior, I had assumed that the water level difference between high tide and low tide wasn’t more than a meter or so. The reality is that in some places, like at Hall’s Harbour in Nova Scotia, Canada, the difference can be up to 14 meters! The rate at which it rises is about 2.5 centimeters a minute, escapable unless you were wading far out at sea.
After realizing how much more water is present in one area at high tide, I got to thinking. Where does all the water go when it recedes? Surely it can’t just… disappear? Then, I realized that at any one point in time on Earth, if it is high tide somewhere, then it is low tide elsewhere. So, the water is pulled towards those continuously moving (at least, relative to the surface of the Earth) points at which high tide exists, and thus, low tide exists.
Thankfully, there aren’t mystical forces drinking up the ocean away from shores, or we’d have bigger problems to deal with.
Another thing about tides that I didn’t know about until just a few days ago was that yes, the moon causes tides, but in what way? It turns out that tides are caused by the magnitude of the difference in gravitational force felt on opposite sides of a body, not necessarily the magnitude of the forces themselves. I had always accepted that the Moon’s gravitational force somehow caused tides since that’s what I was told since I was very young, but I also figured that the gravitational force on the Earth from the Sun must be stronger than the Moon’s, or we’d probably crash into the Moon. I had never put two and two together, and wondered why it was the Moon that caused much larger tides, even though the Sun pulls the Earth with much greater force.
The secret is that gravitational force drops proportionally to the square of the distance from the object, so the difference between gravitational force felt at two points separated by a constant distance is higher when they are closer to the massive object than if they were farther away. In this case, the two points are opposite sides of Earth, and the objects causing a force to be felt are the Moon and the Sun.
It was thanks to a recent Astronomy homework assignment that it was made apparent to me! See, you really do learn things in school. I’m looking forward to the next astronomical epiphany, but until then, enjoy this spiraling tidal time-lapse!
Although Isaac Newton’s most famous contributions to astronomy are his laws of motion and gravitation, which he published in Principia, Newton also founded modern spectroscopy by publishing his second work, Opticks. Spectroscopy is an essential tool for astronomers because it allows them to not only analyze the presence of certain chemical elements, but also physical conditions such as density and temperature.
Three spectra produced simultaneously by the new efficient X-shooter instrument on ESO’s Very Large Telescope, found here.
Just as a fingerprint allows a forensic scientist to determine who was at a crime scene, unique pattern of colors, or spectra, for each type of atom can help us identify which element or elements are in a star. There are three types of spectra, continuous, absorption, and emission. A continuous spectrum is often a backdrop of radiation that gives off all wavelengths. Absorption spectra consist of dark line patterns – missing colors that represent elements that are absorbing certain wavelengths of light. An emission spectrum usually contains bright lines emitted due to an atom or molecule making a transition from a high energy state to a lower energy state.
One of the things I’ve always been most curious about on the topic of space is: is it possible for something that emits light (like a star) to emit light such as radio or gamma waves but not visible light? If such an object existed, it would be invisible to us, although it could still be detected. But it such an object existed and happened to be traveling on a course dangerously close to our solar system, we might not know to look for it with special instruments because we can’t see it.
Stars are primarily powered by fusion – fusing hydrogen atoms into helium (sometimes other elements are involved, but these are most common). This produces a wide range of light waves, from gamma to radio. Visible light is in between those extremes, so it’s expected to be emitted as well.
The closest thing to a star that doesn’t emit visible light is a black dwarf (pictured above), which has yet to be discovered. Once a white dwarf star runs out of fuel, it theoretically will turn into a black dwarf, emitting no heat and no light. The only way to observe it would be if another object’s emitted light bounced off of it. There are no known black dwarfs; the universe (we believe) has not been around long enough for any white dwarfs to burn through all of their fuel. So, the chances of a massive, invisible object speeding through space towards us (or a similarly invisible approaching alien fleet) are essentially zero.
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Artistic Depiction of a “Flat Earth” via New York Post
While believers in a Flat Earth have always existed (even after it became widely understood that the Earth is a sphere), the number of “Flat Earthers” has grown (and continues to grow) at alarming rates. So how is a fact that has been proven thousands of different ways over a few thousand years rejected by roughly 6% of the global population. This movement is a prominent example of how we need to better understand and communicate the “Nature of Science.” First, the goals of science must be understood. A huge part of the Flat Earth movement is the idea of a government conspiracy using lies and “fake science” to fool its citizens. In reality, science is an objective process meant to discover truth. The scientific laws used to show the Earth is round have no political agenda nor are they subjective thoughts of a few individuals. Second, we must look at how the Flat Earth movement has incorrectly employed the Scientific method. Scientific studies often give results different from what you expect, but these results are still valid and important. Many Flat Earthers who set out to prove the flat nature of the Earth, however, have already decided what the outcome of their experiments should look like, and pick and choose the data that best supports their hypothesis of a Flat Earth. In other words, rather than conducting an experiment and letting the data lead them to a conclusion, they conduct an experiment with a conclusion in mind, and ignore any evidence that might prove otherwise. The Nature of Science is admitting that we may be wrong when we discover a new, more comprehensive way of explaining our observations. Understanding this nature, and how to properly use science, is crucial for our society to reestablish our trust in the scientific process.
In the documentary Behind the Curve, Tim Urban gives an excellent metaphor to understand the nature of science. I highly recommend this documentary to everyone, especially those interested in Flat Earth theories and the Flat Earth movement (it is available on Netflix).
(Urban’s metaphor, along with an actual experiment done by a Flat Earther occurs at 47:18 if you are interested in just that part).
While we discussed in class the importance of blackbody spectra continuous spectra, there is an important historical footnote in understanding where the famous blackbody curve arises from. Physics in the late 1800’s and early 1900’s predicted the wavelength-intensity relationship to be I α 1/λ^4, using a derivation based on classical statistical mechanics. This relationship closely matches the observed blackbody electromagnetic radiation for high wavelengths, but is not accurate for lower wavelengths, particularly diverging in the ultraviolet spectrum. This divergence, that intensity ought to be going to infinity as wavelength goes to zero, came to be known as the ultraviolet catastrophe. The solution to this catastrophe was formulated in the early 1900’s by Max Planck. He started from the assumption that there was a minimal amount that energy could change by while emitting blackbody radiation. With this assumption, he was able to match the observed data far more accurately, creating Planck’s law based on strictly empirical data.
This assumption of a minimal energy change became the foundation of quantum mechanics. Planck’s insight that energy was quantized was later justified by Einstein through his analysis of the photoelectric effect. This empirical guess that the relationship could match a quantized output level turned out to be a precursor of the existence of photons. The way the blackbody curve looks is fundamentally due to quantum mechanics, and the historical importance of it is hard to overstate.
The size and fluctuation of tides are directly related to geography and the physics of various places around Earth. The average size of tides, however, rises and falls each month in direct correlation to the angle of the Sun and Moon in relation to Earth. These extremes are called spring tides and neap tides, and they each occur two times each month. Spring tides occur during both full moons and new moons, when the gravity from both masses is pulling Earth in the same direction. Tides are on average at their highest during these times because there is no prominent force pulling Earth in any other direction. Conversely, two other times during each lunar cycle the Moon and Sun form a 90 degree angle with Earth. As we learned from previous activities, the Sun has a much stronger gravitational force on Earth due to its humungous mass. However, the moon still has an impactful effect on the directional pull of Earth because of its close proximity, specifically pertaining to tides on a daily basis. With the Sun and Moon pulling Earth in opposite directions, neap tides occur, and the average height of the tides is at its lowest. Other factors such as the the size of the basins that bring water to shore have more of an effect on the size of tides at specific locations, but in terms of averages, neap and spring tides are strong predictors.
How much impact do The Sun and The Moon have on Earth’s tides?
Also, what would happen to the Earth’s tides if there were no moon? These are questions that are covered in this blog post about tides.
The Earth’s tides are results of the gravitational pull from the Sun and the Moon on Earth’s water. For starters, gravity plays an important role with both the Sun and the Moon’s tidal forces. Since the strength of gravity decreases with distance, the gravitational attraction decreases as you go from the side of the Earth facing the Moon to the side facing away from it. There are two tidal bulges as a result as the tidal force or “stretching force,” and these include one that faces the moon and one that is the opposite of the moon.
When comparing the tidal effect of the Sun to the tidal effect of the Moon, a misconception is that the Sun’s tidal force is drastically greater than the Moon’s tidal force on Earth. One may assume this is true because the Sun is more than a million times bigger in mass than the moon. However, this person would not be taking into account the fact that distance is also a factor for the strength of the tidal force. Because the sun is much farther away to Earth than the Moon, the Sun’s pull on the sides of Earth is actually small.
If there were no Moon, there would be a significant change in Earth’s tides. Scientists have estimated that without the moon, tides on Earth would be one-third of their current size. Moreover, low tides would be lower and high tides would be higher. I think that it is fascinating that the Moon plays such a significant role in our tides!
I’m looking forward to the next astronomical epiphany, but until then, enjoy this spiraling tidal time-lapse! 
