Weight and Altitude

Posted on February 27, 2021 by justinboreskyvanderbiltedu

Most people know that if you were to take your weight on the earth and then the moon, you would weigh a lot less on the moon. But what about your weight with different altitudes on the earth? Surprisingly your weight also changes with varying altitudes. If you were to take your weight at sea level and you weighed 150 pounds and then you weighed yourself at 10,000 feet above sea level you would find your weight to be 149.92. This is due to the gravitational force being less as the distance to earth increases. Although this might not seem like a big deal it is quite significant because it helps reconfirm the idea that as distance increases for an object the gravitational force between the two decreases.

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The Tides of Mont-Saint-Michel

Posted on February 27, 2021 by connorrobbwilcox
Mont-Saint Michel at Low Tide

As many know, the Moon causes the tides to occur all over our planet. But those same people may not know the place that has the largest change in high and low tides. Said place is an islet and commune called Mont-Saint-Michel. Off the coast of Normandy, France, it has an accessible walkway to its village, with the low tide being about nine miles from the shore, except for some hours where the walkway becomes swallowed up. During the spring months, the sea level rises nearly 50 feet from the low tide. Over twenty times a year this dance between high and low tide occurs at the abbey. The sanctuary has the highest spring tides in Europe and the difference is visible to the public, creating a huge tourist attraction.

The Moon’s pull obviously has something to do with this, but so does the Sun’s. Since the Sun also has a gravitational pull on the Earth’s oceans, when the Sun and Moon align, their pulls combine and have an immense effect, creating a spring or “flood” tide at Mont-Saint-Michel. To see this incredible phenomenon in action check out these videos at Mont Saint Michel – Tide in Time-Lapse HD and The Magical Mont-Saint-Michel: an Island once more at high tide. Would you want to see this one day in person? Does this make you think about the Moon’s effect on other parts of the planet? Let me know!

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Vanderbilt Dyer Observatory

Posted on February 27, 2021 by laineroberts
Vanderbilt Dyer Observatory

Looking for a place to up your stargazing? Vanderbilt University has an observatory just 20 minutes away from campus! The Dyer Observatory has a 24 inch reflecting telescope. This means that the telescope uses one or more mirrors to reflect light from space to form an image for the viewer. One of the advantages of using a reflecting telescope is that it will allow the viewer to see more than other types of telescopes. This is because the types of glass used in other types of telescopes, as opposed to the mirrors used in a reflector, absorb some of the wavelengths of light coming from space before they can get to the viewer. The three main types of reflecting telescopes are Newtonian, Cassegrain, and Gregorian. Each type shares a similar model in that they use mirrors to capture the image but differ in how many mirrors and how those mirrors are arranged within the telescope. Another example of a reflecting telescope that you might be more familiar with is the Hubble Telescope!

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Newgrange

Posted on February 27, 2021 by bellagoodnight

When reading up on archaeoastronomy, I was immediately fascinated by Newgrange, a structure located in Ireland. This fascination was not only due to my slight obsession with Ireland, but also because of its age. It was built roughly around 3200 BC, meaning it is actually older than the Egyptian pyramids and Stonehenge! On the outside, Newgrange looks like a mound surrounded by a stone wall, and on the inside, there are passages and tombs.

Newgrange was first perceived as just a passage tomb, but after more inspection by archaeologist Michael O’Kelly, it was shown to have some sort of astronomical, and possibly religious, purpose. Not only was it a burial site, but also a monument. On the winter solstice, sunlight shines through an opening as the Sun rises and illuminates the passage along which people are buried. Here is a video showing the phenomenon, along with more explanation of the difference in light shining in when it was built compared to today. The exact purpose of this feature and the structure itself is largely unknown, though it has roots to the mythology of the area. There are debates whether the original purpose was from a religion that worshipped the dead or a religion more astronomically based, possibly trying to capture the Sun’s light on the shortest day of the year.

It is truly an amazing feat of architecture for people in 3200 BC, considering they would have lacked many tools that would aid in the building. Many of the stones in the structure are massive, and the wall surrounding it would have taken many many years to complete. It also shows a strong understanding of the Winter Solstice being the shortest day of the year, and a remarkable precision in allowing the light in as the Sun rises that day.

Photo of Newgrange by Joshua J. Mark

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Spectroscopy and Stars

Posted on February 27, 2021 by christianc3
Spectroscopy Light Prism

While it may seem impossible to be able to identify the types of elements that stars billions of light years away are made of, scientists discovered a way to do exactly that. In the 1850s, Kirchhoff and Bunsen managed to identify what the black lines in light spectra meant, and it allowed them to identify elements that make up the light being shown through their invention, the spectroscope. The spectroscope shows dark lines within a spectrum of colors, these black lines show which wavelengths are being absorbed and therefore which elements are present because each element’s wavelengths are absorbed by a different areas on the spectrum.

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Newton and His Laws

Posted on February 27, 2021 by allyworthington

Isaac Newton is a household name for his invention of calculus, laws of motion, and realization that gravity exists in the heavens (contrary to Aristotle’s beliefs!). College students that have studied introductory physics or math may have been exposed to Newton’s three laws of motion, but how exactly are they relevant in the context of astronomy? Let’s restate them and provide some astronomical context:

            Newton’s First Law: an object moves at a constant velocity (or stays at rest) unless acted upon by an outside force. This law explains why the spaceships we launch do not need fuel after they are in space; without air resistance or friction in space, ships can simply move at a constant velocity without a need for thrusters (hint: a net force!). 

            Newton’s Second Law: mass multiplied by acceleration equals force. Large planets can exert a greater gravitational force on, say a comet, than a smaller planet would—mass is a direct factor in the determination of force (stay tuned for a future post on the Universal Law of Gravitation). 

            Newton’s Third Law: each force has an equal and opposite reaction force. Celestial objects, or any objects for that matter, exert forces on each other. You heard that right—that same gravitational force that keeps you grounded to Earth is also being exerted on Earth by you! 

From The Science Explorer

While this brief blog post is not an exhaustive astronomical explanation of Newton’s laws, I do hope it provided a little more context than simply F = m • a.  

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Tidal Friction: a 5 hour long day to a month long day

Posted on February 27, 2021 by brandonlipper
SlidePlayer

Due to the Universal law of gravitation, we know that objects of equal mass have a larger gravitation force between them when they are closer together. Because the near side of the Earth is closer to the Moon than the far side of the Earth, the force between the Moon and the near side of Earth is greater than the force between the Moon and the far side of Earth. This difference in forces causes the Earth to stretch along the Earth-Moon line, which causes a bulge on the near side of the Earth and a bulge on the far side of the Earth. This stretching is caused by a “tidal force” and causes the rising and falling of tides on Earth as the Moon continues its orbit.

George Darwin, Charles Darwin’s son, was the first to mathematically illustrate the theory of tidal friction. Tidal friction occurs because, as the Moon continues along its orbit, the Moon’s gravity attempts to pull the bulges right along with it, while the Earth attempts to pull the bulges along with it as it rotates. A torque is produced and a friction between Earth and the tides slows down the rotation of the Earth. Due to the conservation of angular momentum, the Earth’s loss of angular momentum becomes the Moon’s gain of angular momentum1.

This transfer of angular momentum results in the slowing of Earth’s rotation and the growing of the Moon’s orbit. These changes occur very slowly; the length of a day increases by about 1 second every 50,000 years1. However, these seconds add up and it is likely that early Earth had a day of only about five or six hours and the Moon was far closer to the Earth than it is now1. Tidal friction also explains the synchronous rotation of the Moon; as the tidal force from the Earth slowed the Moon down, it eventually rotated at the same rate as its bulges1. Eventually, the Earth could have a synchronous rotation toward the Moon and have days as long as its months. However, this likely would not last consistently due to the tidal forces of the Sun.

[1] Bennett, Jeffery, et al. The Cosmic Perspective: The Solar System. 9th ed., Pearson, 2020.

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Wanderers of Space

Posted on February 27, 2021 by 20harriganc

In this post we will talk about the concept of retrograde motion. If you watch the movement of planets, it is actually quite complex. The word planet comes from a greek term meaning “wandering star”. Planets typically move eastward throughout the constellations. When there is apparent retrograde motion the planets are moving westward throughout the constellations. The reason why it is apparent is because we aren’t always able to see it happen. These times of retrograde motion can last weeks to months depending on the planets. To explain the concept simply the planet is always is moving east, but as earth catches up to the planet, it appears to be moving backward as we pass it. This cycle repeats as we orbit the earth. The farther or closer away earth is from a planet determines how wide the range of retrograde motion is. What’s interesting is that people who used to believe earth was the center the universe, had a very difficult time trying to explain what was happening. Retrograde motion

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Stonehenge and Archeoastronomy

Posted on February 27, 2021 by hunterspiveyastr
Sunrise over Stonehenge on the Summer Solstice; Photo by: County Line Magazine

Stonehenge is one of the most easily recognizable sites across the globe. Often designated as one of the wonders of the ancient world, Stonehenge has both fascinated and confounded humanity for centuries. While some may still argue about how Stonehenge came to exist, whether it be aliens, magic, or old-fashioned hard work and sweat, one thing remains almost uncontestable: Stonehenge’s use and significance as an astronomical site. Perhaps the most striking display of Stonehenge’s relation to astronomy comes during the Summer and Winter solstices, when the sunrise and sunset align with the Heel stone, a significant monument in the site’s organization. It has been theorized that this alignment was used by ancient peoples to serve a variety of purposes, from tracking the seasons to ritual and cult practice. What is interesting about this alignment though is that it is not an exact alignment. While this could be an indication of humanity looking too deeply into the significance of the structure, William Stukeley, an 18th century scholar, hypothesized that the alignment may have drifted over the centuries due to changes in the solar system’s ecliptic obliquity. This change is something that Stukeley believed the builders of Stonehenge hadn’t known about, and thus its construction didn’t account for. Whether this is truly the case or not remains unknown, but the striking image of the Summer solstice’s sunrise over the central circle, and its alignment over the heel stone is a sight that is not readily forgotten.

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The Hubble Space Telescope

Posted on February 27, 2021 by derrick37027

The Hubble Space Telescope is one of humanity’s greatest achievements. Deployed in 1990, the telescope is responsible for many of the discoveries made about distant solar systems and galaxies. According to the Nasa website, the Hubble “has made more than 1.4 million observations.” Without this great invention, we would still in be in the dark when it comes to a visual representation of our Universe.

The Hubble Space Telescope

Following the launch of the Sputnik by the Soviet Union in 1957, the United States began devoting more time and money into space travel and research, in an effort to beat the USSR to the Moon (which we did). However, even after the Moon landing was a success, the United States remained interested in space exploration. In 1977, the United States Congress approved funding for the Large Space Telescope project. As the construction and planning for the telescope began, Nasa was simultaneously training astronauts for future telescope service mission. In 1983, the telescope was officially named after late astronomer Edwin Hubble, who made the important discovery that other galaxies in the universe existed and that they were travelling away from the Milky Way. Finally, in April 1990, the Hubble Telescope was deployed and it took its first pictures about a month later.

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