How Spherical is the Sun?

Posted on March 5, 2020 by Phillip Yoon
Nasa Footage of the Sun

From what we know about planets like the Earth and its properties, we may expect the Sun to also experience a bulge, causing its shape to deviate from a perfect sphere. It turns out that the Sun isn’t a perfect sphere, but it’s pretty close to one. If fact, with the help of instruments on Nasa’s Solar Dynamics Observatory, scientists have identified the Sun as the most perfect sphere in nature.

Let’s dive a little deeper into this matter. Because the Sun spins on its axis, we would expect centrifugal force to cause its equator to bulge slightly. It turns out that there is a bulge, but it is almost negligible compared to those that other planets experience. When “scaled to the size of a beach ball, say scientists, the sun’s equatorial bulge would be less than the width of a human hair” (The Guardian). Although the exact reasons as to why the Sun experiences a very small equatorial bulge have not been confirmed, there are a few possible explanations for this phenomenon.

One possible explanation is the Sun’s complicated magnetic field. The magnetic fields inside the Sun could be the force that holds the Sun together, keeping it from bulging out as much as other planets do. Another explanation is the fact that the Sun is a ball of gas, meaning that different parts of the Sun rotate at different speeds, which could also have an effect on the Sun’s shape. These explanations have not been confirmed yet to have a cause-and-effect relationship with the Sun’s shape, but it would be cool to see scientists run tests and simulations in the future to figure out what causes the Sun to be so spherical.

Sources used: The Guardian, Discover Magazine

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What is retrograde motion?

Posted on February 14, 2020 by swarnasakshi

Retrograde. It’s a word you hear tossed around quite a bit lately. Mercury always seems to be in retrograde, which, apparently, is not a good thing. But what is retrograde motion really? Retrograde is an apparent motion. An objects appears to be in retrograde when it is lapped by another object that is the point of view. For example, when Earth laps Mars in its orbit, Mars is in retrograde motion and looks like it is moving backwards. Retrograde occurs when one object approaches “opposition” with respect to another object. So retrograde really has no effect on relationships.

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Source: Nasa

 

 

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The Visible Doppler Effect

Posted on February 12, 2020 by Lily
Video explaining light within the universe, covering topics from the spectrum of both visible and invisible light to the Doppler Effect. The Doppler Effect is discussed around time stamp 8:30.

            Ever wonder why the siren of a police car or a firetruck seems to change in pitch after it passes by? Well, the phenomenon is known as the Doppler Effect. The Doppler Effect explains how sound, like in the example above, or light waves are manipulated by the movement of an object in relation to a stationary object.

            The Doppler Effect has confused and fascinated me since first learning about it in my junior year physics class. Admittingly, I was absent for most of the days of that particular lesson, so I left that class stumped by how the Doppler Effect truly worked and the science behind it but putting it in terms of light turned everything around.

            Now the question is raised, how is my perception of light manipulated by movement? Well, turns out it all has to do with the wavelength of light waves. The visible light spectrum is composed of many different wavelengths that each dictate a different color that becomes visible, with blue and violet being the shortest wavelengths and red and orange being the longest. These wavelengths, however, can be manipulated by movement. When an object in space is traveling towards the Earth, the wavelengths of the light being emitted from that object are manipulated to be shorter than they actually are. As a result, the object appears to be bluer than it really is or known as being blueshifted. On the other side, when an object is traveling away from the Earth, the wavelengths are artificially stretched, causing the object to be redder in appearance, or known as being redshifted.

            Although our perceptions of sound and light appear rigid, the manipulation that travel causes to wavelengths is a reality that, thankfully, has become far less confusing to me over time.

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Spring and Neap Tides

Posted on February 11, 2020 by Rehan John
Spring Tides
Neap Tides

Many are familiar with the concept that the Moon creates high and low tides on Earth, but few know that the Sun also plays a role in the process. Tides are formed from the gravitational forces of the Sun and Moon pulling on the Earth differently in different places due to variations in distance. The closest part of the Earth to the Sun/Moon is tugged more so than the center of the Earth. This causes the Earth to bulge slightly, in the same way a rubber band does when tugged on one side. The Moon is the much more dominant party in tidal affairs, despite its inferior gravitational force. This is because it is much closer to the Earth, so the differences created in its gravitational fields are much more pronounced compared to the Sun. Nonetheless, the Sun’s tidal force is still felt, especially when it directly contrasts or works alongside that of the Moon.

Spring tides occur when the Sun and Moon work in perfect harmony with each other to produce higher high tides and lower low tides. Such occurs when the Moon is in the new or full phase and the Sun and Moon are both tugging on Earth in the same directional axis. Their efforts become added and a conjuncted, more powerful force is created. If the spring tide occurs one of the equinoxes the tide becomes even more polarized as the Sun forms a straighter line than usual with Moon and Earth at the equator. Neap tides on the other hand refer to the weaker tides which occur when the Sun and Moon are working against each other. This happens when the Moon forms a ninety degree angle with the Sun relative to the Earth (first and third quarter phases). Neap tides occur about 7 days after a spring tide.

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Gravity’s Effect on Light

Posted on February 10, 2020 by ericlovesstars

Light appears almost instantaneous to the naked eye. This seems especially evident on the Fourth of July, watching a firework explode, only for the boom to hit you seconds after the colorful light hits your eyes. It does not seem like something so fast and instant could be affected by a force such as gravity. However, gravity actually has the ability to effect rays of light; not in the way you would expect. Light doesn’t have weight like matter does.

An illustration of gravitational lensing showcases how background galaxies — or any light path — is... [+] distorted by the presence of an intervening mass, but it also shows how space itself is bent and distorted by the presence of the foreground mass itself. Before Einstein put forth his theory of General Relativity, he understood that this bending must occur, even though many remained skeptical until (and even after) the solar eclipse of 1919 confirmed his predictions.
The Theory of General Relativity show how light is bent through space, read more about it here

According to the Theory of General Relativity, mass warps the space around it, creating the effect of gravity. This warp in space is what has the ability to bend light. Beams of light passing through this warp is moving in a straight path, yet is bending through this warp. Therefore, the light does not appear to be moving straight to an outside observer. It does not actually have an effect on the speed of light, just the path it follows.

The idea that the force of gravity effects more than just the mass that we see on a daily basis is pretty wild – its effect can bend the light which generates the image we see when we look up into the sky.

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What is celestial navigation?

Posted on February 10, 2020 by abbigailhughes
Photo Taken from Sail Away

Those who use the placement of stars in the night sky in order to determine where to go to are using a practice called celestial navigation. Ancient peoples noticed the patterns associated with stars in the night sky and were able to study and record them in order to teach the following generations how to read the sky for navigation. The celestial equator, seen in the image included, resides between the south celestial pole and the north celestial pole. The stars on this celestial equator are how we see the stars — rising in the east and setting in the west. In the Northern hemisphere where we live, our northern most point in the sky is Polaris, a star that never rises or sets due to how far north it is in the sky. Although it never rises or sets, it moves in the way that it makes a very small circle pattern around the north pole. Other stars in this hemisphere also circle around the north pole, yet depending on their latitude, their circular pattern may be much larger in order to insinuate the rising and setting effect that we see. Stars such as Polaris that do not adhere to the rising and setting phenomena are labelled as circumpolar. Celestial navigation in ancient times identified stars in the sky such as Polaris or the Big Dipper and used these patterns to guide them in the right direction.

Have you ever used celestial navigation or followed the North Star? Do you think that it is still important to know and understand celestial navigation even though we have more advanced technology today?

Source: A Celestial Navigation

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Gravity Waves

Posted on February 10, 2020 by khalilgreene
Source: (Space.com)

Gravity waves have been speculated to exist ever since Einstein set a speed limit to the universe, the speed of light. When Newton came up with the gravitational force equation, it only considered mass and distance when calculating the force. It did not take into account that if one mass disappeared, then that information of the force leaving would surpass the speed of light. Einstein said this was not possible and there had to be a speed at which the difference in gravity traveled. When LIGO detected the first gravity waves in 2015, the experiment was groundbreaking. It proved that Einstein was right and Newton was wrong.

I am excited to see the implementation of the new knowledge that we have about the universe in the future. Will this somehow open doors for someone to make new theories, or will we just go on about our days the same as before?

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Alphonso X

Posted on February 10, 2020 by clairesspacejam
This painting shows Alphonso X reading

Every time I pick up The Cosmic Perspective to do the assigned reading, I end up learning something new and exciting. This unit, while I was reading Chapter 3 “The Science of Astronomy” one particular part struck me. The textbook mentions a Spanish monarch named Alphonso X who lived from 1221 to 1284. Alphonso X had complied the most modern tables of planetary motion based on the Ptolemaic model until Copernicus’s revolution nearly 200 years later. Astronomers knew Alphonso’s tables were flawed but many people were unwilling to take on the arduous task of fixing the underlying theories. Alphonso was credited with saying “If I had been present at the creation, I would have recommended a simpler design for the universe (64).” This quote caught my interest because it highlights just how incredible it is that humanity knows even anything about space. We are so small in the universe but are able to use our brains and empirical information over ages and ages. Especially considering how challenging it must have been to understand the universe while lacking the modern technology we have now. This quote also inspires me to think about all that we will learn about space in the future.

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Time Warps- More Than Just Sci-Fi?

Posted on February 10, 2020 by abriannarhodes00

Space travel is a relatively new concept compared to the overall age of astronomy. From Armstrong to Koch, sending people into space is still an amazing feat with distances that don’t dare to go beyond our moon. But what if this could change? What if, like our telescopes, we could travel to Jupiter or Pluto or beyond the bounds or our Solar System or, dare I say, to the ends of the Universe?

While these are rather dramatic in terms of our modern technology, the idea behind the possibility of the revolution of space travel is not. This idea is the concept of time warps. Time warps, phenomenon that have been known to scientist for over 100 years, are places in the universe where time is either sped up or slowed down due to the presence of a very large mass. The knowledge of these phenomenon began with Einstein’s theory of general relativity asserting gravity as a “property of the curving of space and time,” meaning that anything with mass, no matter how small, can warp time. The larger the object, the more time is warped, which is why when something is near a black hole, everything occurs slower than it would to an outside observer.

Although Sci-Fi artist love to take this idea and generate new theories for travel, it is rather unlikely that their form of rocket ships will become a reality any time soon. This is primarily because these artist focus on a rather unlikely scenario for time-warp travel:wormholes and cosmic strings. While wormholes are likely to have existed in the early universe, these connections of matter and light would have been very unstable and thus collapsed relatively quickly. Furthermore, cosmic strings, if a reality, are rather small. In fact, they would be extremely tiny- too tiny for any ship to fit through.

Sci-Fi fanatics can dream, but it seems that traveling to the edge of the universe will have to wait until a new, unforeseen discovery is made.

https://www.livescience.com/65448-how-to-detect-time-warp.html

Image result for time warp
This is a theoretical image of a time warp from https://www.newsweek.com/time-warp-where-find-one-1423508. A time warp is a change in time caused by the presence of mass.
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Celestial Navigation throughout History

Posted on February 10, 2020 by dannydonofrio217
Image result for celestial navigation
An old drawing showing someone using a tool for celestial navigation. Taken from https://timeandnavigation.si.edu/navigating-at-sea/navigating-without-a-clock/celestial-navigation

Like many other technologies, one might assume that celestial navigation has only been truly developed efficiently in recent times with our technology. But you may be surprised to know that many of the techniques we use today were invented centuries ago, or even thousands of years!

Celestial navigation is the practice of using angles between celestial bodies and the earth’s horizon to determine one’s location, especially at sea. Tools like sextants are especially useful for this, and have been around for centuries- there have been documented usages of such a tool going as far back as the 1500s. It makes sense that such a simple yet effective tool has remained a consistently useful tool for navigation; in modern times, it provides a crucial backup if electronic navigation systems should encounter difficulties. In fact, the U.S. Naval Academy (among other institutions) has recently reimplemented celestial navigation courses, recognizing its longstanding usefulness.

Celestial navigation has been a mainstay of exploration for ages, and the main principles have largely stayed the same.

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