Archaeoastronomy

Posted on February 12, 2018 by laurenegish

Stonehenge Stonehenge

The concept of time is something that is invaluable to humans. The passage of time brings with it changes in weather, seasons, rainfall, and daylight. Especially during the beginning of civilizations, it was important to understand how much time passed to keep track of the changing conditions. In order to keep track of the time of day, the first clock invented was a sundial. The sundial works by using a stick or another long object that can cast a shadow on a flat plate as the Sun passes through the sky. The shadow from the sun that this sundial creates would help people of ancient societies assess the time of day according to where the shadow fell. In order to keep track of the seasons, some societies created elaborate structures that predicted solstices and equinoxes. For example, Stonehenge was used for the purpose of predicting these seasons with the site aligned towards the sunrise at the summer solstice and the sunset of the winter solstice. Another astrological site, El Castillo in Chichen Itza, Mexico was also used to keep track of seasons. Every spring and fall equinox, as the sun sets, the sun and shadows that fall across the steps of the structure create the appearance of a snake. In order to create this design, the Mayans had to have an understanding of the sun and the changing of seasons.

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Derivation of Kepler’s Second Law

Posted on February 12, 2018 by danielsolarsystem

Here is a detailed derivation of Kepler’s second law of planetary motion.

I find this derivation of Kepler’s Second Law and similar derivations I have seen for other laws extremely interesting. This is actually the most straightforward of the derivations of Kepler’s three laws. The reason I am so intrigued by this derivation is because much of the math used had not yet been invented during Kepler’s lifetime. No formal knowledge of calculus had yet been published. No works would be published formally documenting derivatives or integrals until over a hundred years after Kepler’s death. Without any knowledge of these mathematical methods, Kepler would have had to derive these laws based entirely on his own intuitions about the data he was collecting. In addition, he would have had to stake his pride on the publication of these laws which he would not be able to formally prove. That shows a great deal of confidence.

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Contextualizing Historical Astronomers

Posted on February 12, 2018 by danielsolarsystem

Sir Isaac Newton- Born: 12/25/1642, Died: 3/20/1726

      Isaac Newton is regarded by many as the father of modern science. Not only did he come up with his three laws of physics, but he also invented calculus as he was trying to understand the orbital paths of comets he was observing. The application of the math that he was inventing allowed for a fundamentally new understanding of the way that celestial bodies interacted with each other. Newton’s Law of Universal Gravitation was prominent in these new understandings. The theory held that bodies were gravitationally attracted to one another according to the inverse proportion of the square of the distance between those bodies. His three laws of motion were later derived from this and other early theories.

      The English Civil War broke out during the year of Newton’s birth. In this war, Charles 1 fought Oliver Cromwell’s parliamentary forces also known as the “Roundheads”. In the end, Charles 1 was executed after Cromwell’s concessions were demanded from the royal family.

      In the late 1600s, the English were consolidating their hold on the 13 colonies. In 1664, they were able to claim New Amsterdam from the Dutch. In the same year, Newton was conducting his experiments with gravity.

      Gottfried Wilhelm Leibniz, who was alive at the same time, is also credited with the invention of calculus. His notation and differential techniques are the ones primarily used in modern calculus today.

I found the dispute between British and continental European mathematicians over who invented calculus to be very interesting. It seems emblematic of the time to be caught up in the honor of inventing or pioneering a field. Unfortunately, there was no tale of a duel a la Tycho Brahe.

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Moon and Tides – The Magic of Gravity

Posted on February 12, 2018 by dempsy
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Tides, picture source

Our sea has a periodic rising and falling phenomena. At a time, the sea will go up and reach to the peak, and at another time, the sea will go down and leaves us an island or a beach. This phenomena is called tides.

The tides are mainly caused by gravitational force from Moon. When we are at the near side of Moon, we are closer to Moon and therefore we will experience a larger gravitational force from Moon. Thus, as the seawater near us will also experience a larger gravitational force, it will be pulled a little bit closer towards Moon and then a rising tide occurs. Besides, when we are at the far side of Moon, we will experience the least gravitational force, which means we will experience the most centrifugal force. Therefore, we the gravitational force from Moon cannot hold the water at the far side of Earth from it, and the seawater at that part will also experience a rising tide. On the contrary, when we are at middle way between the far side of Moon and near side of Moon, the gravitational force from Moon will be neither too large nor too small. Therefore, neither will the seawater be pulled towards Moon nor will it loosed by the Earth. The seawater will come closer towards the earth surface and then a falling tide occurs.

Besides the liquid tide such as tide of seawater, there are some other kinds of tides. An interesting one needs to be mentioned is solid tide. Solid tide occurs on Moon due to the gravitational force from Earth. Unlike Earth, Moon always faces Earth from one direction, that is – one part of Moon will always be the near side of Earth and another part will always be the far side of Earth. As Moon is orbiting Earth and experiencing the gravitational force from Earth, its near side and far side of Earth gradually stretched out, which slowly makes it transit from sphere towards a ellipsoid. Scientists call this phenomenon “Tidal Locking”

MoonTorque

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Privatization in Aerospace

Posted on February 12, 2018 by Taylor Matalon

In the past week, the Trump administration published a document, obtained by the Washington Post, that described its plans to cease funding for the International Space Station and leave the station up for grabs for the private sector. This is being done to free up the NASA budget for other Aerospace Endeavors. NASA currently spends $3-4 billion per year on the station’s maintenance (which is handled by Boeing Company). Though many pro-NASA members of Congress are pushing back on this decision, I personally see it as a smart financial decision for the future of aerospace. Orbital space is becoming easier and easier to reach, and to open the space for commercial and private endeavors is a smart move for the “business” of space exploration. Boeing already runs the ISS (and is just funded by the federal government), and private enterprises like SpaceX are already leaders in the field of deep space exploration. When the market is opened up to potential competitors, competition increased the production and effectiveness of the existing firms. Also, if there is an economic incentive to explore Space, rather than simply a scientific incentive, the masses (especially those who care about money) will jump on the Space train (or rocket, if you will). Then, us scientists will have the backing of the corporate elite for all of our nerdy explorations.

The Trump administration is also, unfortunately, planning to cancel 5 Earth-Science missions, defund the Wild Field Infrared Survey Telescope, and terminate the NASA Office of Education. Clearly, there is still work to be done to convince politicians and private interests that Space Exploration is necessary for humanity’s progress and deserving of full funding.

ISS

 

 

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Absolute Hot

Posted on February 12, 2018 by yadavdhruv

Screen Shot 2018-02-12 at 4.30.40 PM

We all have heard about absolute zero – the coldest temperature possible. At this point, atoms cease to move completely. All heat is really is just the movement of atoms and the energy with which they’re moving. Hotter things tend to have more energy, and their atoms move more. Thermodynamically, it is impossible to reach this temperature. But we know that we are able to at least define it. So that begs the question, is there an opposite end of the spectrum – an absolute hot? Absolute zero makes sense because you can keep taking energy away from something until it has none. But adding energy shouldn’t be a problem. Theoretically, you should be able to add an infinite amount of energy, so there is no limit to how hot something can get.

Technically, that is correct. You can keep adding energy to no end. However, there is a point where “too much energy” becomes a problem for us. This is at the Planck Temperature. Planck Temperature occurs at 1.417×1032 K, which is mind bogglingly hot. To understand a little more, gravitation along with quantum theory tells us that wavelength and temperature are related. If something’s temperature is 1.417×1032 K, then it also is emitting the smallest possible wavelength at 1.616 x 10−35 meters, which is called the Planck length. This is the shortest distance possible in our universe! We could potentially add even more energy to this system, however our current understanding of physics breaks down when we reach beyond this temperature. If we had a theory of quantum gravity, perhaps we could be able to explain this, but currently we do not.

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gravity.wav

Posted on February 12, 2018 by Nathan Xiao

 

FINAL_Header_Gravitational_waves_LIGO_092916

Picture: Artist depiction of gravitational waves at work

Gravity has long been one of the most transfixing ideas in our universe. For centuries, we have tried to crack the code of what exactly lies beneath our 9.8 meters per second squared. Since the apple first dropped on Newton’s head, we’ve been pining to understand gravity’s secrets. An important idea in understanding gravity is waves. Albert Einstein first predicted the existence of gravitational waves over 100 years ago. Gravitational waves help to explain a lot of the happenings of the universe. These “ripples” in space-time travel at the speed of light and carry important information about the universe.

Although Einstein could not detect the presence of the waves, we have recently been able to detect their presence and validate his theories. In 2015, scientists used an instrument called LIGO (Laser Interferometer Gravitational-Wave Observatory) to detect gravitational waves, generated by two colliding black holes nearly 1.3 billion light years away. 

Detecting gravitational waves is a huge breakthrough in understanding our universe.  These waves carry information about cosmic objects and events that is not carried by electromagnetic radiation. Objects like black holes that do not emit electromagnetic radiation can now be detected through gravitational waves. Another benefit of gravitational waves is that they are not impeded by mass in the universe, giving us a clear perspective on distant phenomena in far reaches of the universe. The potential for gravitational waves is ripe with opportunity, and detecting them opens many new doors in astronomy. We really have only just begun.

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A Powerful Letter

Posted on February 12, 2018 by astronomydylan

Galileo-1636-0tp
Some letters can change the world!

Chapter 3 explained to us how Galileo solidified the Copernican revolution, and sealed the case on how Earth would be viewed in perspective of the universe. In 1615, Galileo wrote a letter to Grand Duchess Christina, in attempt to accommodate his observations’ confirmation of Copernicanism with the doctrines and scripture of the Church. He held that Copernicanism was not merely another perspective, but it was the correct way of looking at the universe. The Catholic Church, which had long held that the Earth must be the center of our perfect (and small) universe, because if Earth is not so special, how else could we know that God is watching everything?

As part of that letter, Galileo wrote “the intention of the Holy Ghost is to teach us how one goes to heaven, not how heaven goes.” With these few but powerful words, Galileo posited that the Church authorities had been improperly interpreting the word of God, dealing a massive blow to the link between astronomy and Christianity, claiming that the latter had no place in governing the former.

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A Powerful Letter

Posted on February 12, 2018 by astronomydylan
Galileo-1636-0tp
Some letters can change the world!

Chapter 3 explained to us how Galileo solidified the Copernican revolution, and sealed the case on how Earth would be viewed in perspective of the universe. In 1615, Galileo wrote a letter to Grand Duchess Christina, in attempt to accommodate his observations’ confirmation of Copernicanism with the doctrines and scripture of the Church. He held that Copernicanism was not merely another perspective, but it was the correct way of looking at the universe. The Catholic Church, which had long held that the Earth must be the center of our perfect (and small) universe, because if Earth is not so special, how else could we know that God is watching everything?

As part of that letter, Galileo wrote “the intention of the Holy Ghost is to teach us how one goes to heaven, not how heaven goes.” With these few but powerful words, Galileo posited that the Church authorities had been improperly interpreting the word of God, dealing a massive blow to the link between astronomy and Christianity, claiming that the latter had no place in governing the former.

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Physics in the Olympics

Posted on February 12, 2018 by astronomydylan

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These athletes understand physics!

We have all heard the joke which rings all too true: the Olympics need one average person competing for reference. Last night, olympic figure skaters dazzled the international community with their many spins and jumps. I found myself extremely curious as to how the skaters are able to spin so many times with apparent ease.

When a figure skater spins, as they are able to do for very long durations, they actively conserve angular momentum by bringing their arms and legs inward, reducing the distance between the skater’s center axis of rotation (the skate on the ice) and the skater’s mass. Thus, by conserving angular momentum, rotational velocity increases, and the figure skater is able to complete what appears somewhere between extremely nauseating and impossible to the rest of us.

Angular momentum is basically similar to linear momentum, which is simply calculated by multiplying mass and velocity of the object. While the formula is not the same, if no external force is present, then momentum must be conserved and not change, in both linear and angular form. Since there is virtually no friction slowing down a figure skater on the ice, angular momentum is conserved, and thus the skater is able to increase speed by compressing mass into a smaller amount of space. 

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