Assignment 6 - Modern Astronomy

            Telescopes were used to enhance vision for better observations of our universe since the 16^th and 17^th centuries. When the 18^th century came around, the telescope was the go-to instrument to explore the universe with just the naked eye. It allowed people to observe such distant objects that would otherwise unseen by the naked eye, this allowed for such huge advancements in this field of science. As the 20^th century began, many astronomers believed that the universe only consisted of one galaxy: the Milky Way. But, in 1924, an American astronomer, Edwin Hubble, disputed this belief and believed that there were galaxies than just our own. He used the Hooker telescope on Mount Wilson in California to observe so many other galaxies that were all moving away from each other. This observation triggered to raise a theory of how the universe was constantly expanding. Many astronomers spent many nights in observatories using telescopes to help prove this theory and possibly find out more unknown facts about the universe, however, there was a major obstacle that prevented them from getting a clear image of the universe: the Earth’s atmosphere.

            The Earth’s atmosphere blurs visible light, which causes brighter stars to twinkle, hence making it harder to observe dimmer stars in comparison. In addition, the atmosphere absorbs or totally blocks other wavelengths of light such as ultraviolent, infrared, gamma rays, and X-rays (to actually protect us from the harmful effects of these types of light rays). This is also why observatories have telescopes near the tops of mountains to prevent any disruptions caused by city lights. In 1923, Hermann Oberth (a German scientist), published a paper that proposed a telescope being propelled into Earth’s orbit with the use of a rocket to bypass the obstacle of the Earth’s atmosphere in observations. A Princeton astrophysicist Lyman Spitzer then wrote about his support about the scientific benefits of a telescope above the Earth’s atmosphere in 1946. Subsequently, as the Soviets launched their satellite Sputnik in 1957, NASA followed suit and launched two Orbital Astronomical Observatories (OAOs) into orbit. This allowed for further research into more space observatories and allowed them to make many ultraviolet observations.

            As a result, in 1969 after Spitzer gathered support of other astronomers, the National Academy of Sciences approved a project for a Large Space Telescope (LST). Although, with the “race to the moon” by the Soviets and the Americans, much of NASA space program funding went into their expedition and landing on the moon in 1969, which put the project for a LST in jeopardy. This caused numerous budget reductions into the building of the LST but in 1974, the LST had specifications to have a wavelength range from ultraviolet to infrared light and it had the ability to resolve at least one-tenth of an arcsecond.

            After finally building the LST, the next issue was how NASA was going to launch it into space. NASA and its partners began to think of something that could launch an object into orbit but then return to Earth, in order to be reused over and over again, this resulted in the concept of the space shuttle. NASA predicted that the lifetime of a space telescope would be approximately fifteen years, which raised the issue of having the ability to service the satellite while it is in orbit. They began to develop tools and parts that were high quality but did not harm the satellite’s orbit due to its size; too many instruments (especially large ones) decreased any chances of financial support. NASA and the European Space Agency (ESA) exchanged fifteen percent of telescope time for fifteen percent of the funding for the LST. By 1977, Congress approved the funding and construction began.

            NASA began to then assign tasks for specific NASA field centres. First, the Marshall Space Flight Centre in Huntsville, Alabama was chosen for the design, development, and construction for the newly named Space Telescope (ST). Next, the Goddard Space Flight Centre in Greenbelt, Maryland was chosen to be the lead in scientific instrument design and ground control for the space observatory. Lastly, the Johnson Space Centre in Houston, Texas and the Kennedy Space Centre in Florida provided Space Shuttle support. Maintenance and any upgrades of the space telescope were decided to be done while in orbit as opposed to on Earth to save funding and by 1985 the telescope was renamed the Hubble Space Telescope (HST) and was ready for launch. Unfortunately, in 1986, an accident required NASA to ground the satellite but the bright spot was the enhancements that were made to the equipment on the satellite including the solar panels, computers, and communication systems. Following many stress tests to improve durability, the HST was brought into orbit on April 24, 1990 by the Space Shuttle Discovery.¹

            The Hubble Space Telescope has been in orbit for more than twenty years now and with recent services done to the telescope, it is predicted that the HST would last at least five more years. The telescope has resulted in many discoveries that have greatly impacted the field of science. Two discoveries it has made are dark matter and dark energy, two new fields that have now many physicists exploring these new topics. Dark matter makes up for about twenty-three percent of the universe and is only known to exist based on gravity (it cannot be seen). Dark energy, on the other hand, helped to observe that the rate of expansion by the universe is accelerating as opposed to being constant or slowing down. In addition, the HST has made many important advances in field of extrasolar planets by even having the ability to determine the composition of their atmospheres.⁴ I have chosen these three results because it is so fascinating that beyond our world there many things that humans have not discovered and the way we perceive our world and our universe can change at any second especially with the way advancements in science seem to be trending upward at an astonishingly fast rate.

References:

¹http://www.nasa.gov/mission_pages/hubble/story/the_story_2.html

²http://www.nasa.gov/mission_pages/hubble/story/timeline.html#.VRod1kJBA_s

³http://www.spacetelescope.org/about/

⁴http://www.space.com/17-amazing-hubble-discoveries.html

Assignment 5 - Discoverer of Expanding Universe

Alexander Friedmann was a mathematician and cosmologist born in Saint Petersburg, Russia on June 16, 1888. His father and mother were both working in fields that were not related to the sciences (ballet dancer and a pianist, respectively). Friedmann attended Saint Petersburg State University from 1906-1910, where he studied mathematics. He then got his master’s degree in pure and applied mathematics in 1914, while his research focused on aeronautics, the magnetic field of the earth, the mechanics of liquids and theoretical meterology. Friedmann took many flights in airships to make meterological observations, although when the First World War started he volunteered as a technical expert and bomber pilot for the Russian Air Force. He taught pilots on aerodynamics in 1915, and a year after he became the head of the Central Aeronautical Station in Kiev, then Moscow. When the station disbanded due to the Russian Revolution of 1917, he became a professor of theoretical mechanics at Perm University.

Friedmann returned to his hometown in 1920 after life was getting too difficult in Perm due to the civil war. By the late 1920s, he had become aware with Albert Einstein’s General Theory of Relativity. As a result, in 1922 Friedmann discovered the expanding universe solution to Einstein’s general relativity field equations. Einstein first rejected these solutions, then later acknowledged them to be correct. The expansion of the universe was then supported in 1929 by Edwin Hubble’s observations. Friedmann depicted three models in his papers: positive, zero, and negative curvature of space-time. These models helped to establish the standard for the Big Bang and steady state theories of the universe. In 1923 and 1924, he traveled through Europe discussing his research with other scientists and he was later given the job as the director of the Main Geophysical Observatory in Leningrad. Throughout this period, he had a student, George Gamow, who briefly studied under him. Sadly, Friedmann died at the young age of 37 from what is believed to be from typhoid fever.

References:
http://www.physicsoftheuniverse.com/scientists_friedmann.html
http://www.decodedscience.com/alexander-friedmann-unsung-hero-of-modern-cosmology/19423

Assignment #4 - The Changing Pluto

Pluto is part of a family of small, icy worlds that orbits the sun out on the edge of the solar system. It was once considered the ninth planet in our solar system; however, since 2006 it is now considered a dwarf planet. Pluto’s orbit is highly inclined and so elliptical that it actually comes closer to the Sun than Neptune at times. Its diameter is only 65% of the Earth’s moon though it is very difficult to observe from Earth. Since it orbits so far from the Sun, Pluto is cold enough to freeze most compounds. Observations have found evidence of nitrogen ice, and its atmosphere is thin and composed of Nitrogen (N₂), carbon monoxide (CO) and small amounts of methane (CH₄). This thin atmosphere is said to only be present at times when it is closer to the Sun, though when it gets further from the Sun the atmosphere is said to freeze and basically disappear. Pluto’s low gravity (one-twentieth of the Earth’s gravity) causes the thin atmosphere to extend much further in altitude than the Earth’s atmosphere. Although Pluto is a small planetary body, it has five moons: Charon, Nix, Hydra, Kerberos and Styx.¹

Figure 1 - Pluto (http://onwardstate.com/wp-content/uploads/2014/03/pluto.jpg)

Figure 2 - Pluto and its Moons (http://theplanets.org/wp-content/uploads/2014/09/pluto-moons.jpg)

Pluto was first discovered in 1930 by Clyde Tombaugh at the Lowell observatory, based on predictions from other astronomers. Clyde Tombaugh was born in Illinois on February 4, 1906. Tombaugh built over 30 telescopes in his lifetime since building his first telescope at the age of twenty. Using his telescopes, Tombaugh made detailed observations of Jupiter and Mars and sent them to the Lowell Observatory in hope of recognition. As a result, in 1928, he was offered a job at the Lowell Observatory in Arizona. Scientists observed weird movements by Uranus that could be attributed to another planetary body that was not Neptune, this was the reason scientists were searching for a ninth planet to possibly explain such movements. In 1930, just a couple years after he was offered a job, Tombaugh noticed movement across two images taken of the same area. After studying this object to verify the movement, Tombaugh was able to announce it as the discovery of a ninth planet. The name Pluto was suggested by an eleven-year old girl and was named after the Greek god of the underworld. ²

 

Figure 3 - Clyde Tombaugh (http://i.space.com/images/i/000/020/845/i02/clyde-tombaugh-telescope.jpg?1345732608)

Plutinos are objects from the Kupier Belt which have a 3:2 orbital resonance with Neptune and have semi-major axes of ~39 AU. Some of the Plutinos also cross Neptune in their orbit (like Pluto). The name Plutino is named after Pluto because of the orbital resonance similarities and it does not imply similarities between physical characteristics. The first plutino, besides Pluto itself, was discovered in 1993 and is named (385185) 1993 RO.

References:

¹http://www.space.com/43-pluto-the-ninth-planet-that-was-a-dwarf.html

²http://www.space.com/19824-clyde-tombaugh.html

³http://scienceworld.wolfram.com/astronomy/Plutino.html

Images From:

Figure 1: http://onwardstate.com/wp-content/uploads/2014/03/pluto.jpg

Figure 2: http://theplanets.org/wp-content/uploads/2014/09/pluto-moons.jpg

Figure 3: http://i.space.com/images/i/000/020/845/i02/clyde-tombaugh-telescope.jpg?1345732608

Assignment #3 - Universal Gravitation and Discovery Disputes

Isaac Newton was an English scientist, mathematician, and philosopher who lived from 1642-1727. He is highly regarded as one of the most influential scientists due to his many contributions to the field. Newton is most known for his three laws of motion, which serves as the foundation for classical mechanics. He derived these three laws of motion from Johannes Kepler’s three laws of planetary motion and his own concept of gravity. ¹

Figure 1 - Sir Isaac Newton

Figure 2 - Johannes Kepler

Newton’s first law of motion is that an object will continue to move at a constant velocity as long as there are no forces acting on it. For example, bowling alley lanes have near frictionless surface; therefore if it were an infinite lane, the bowling ball would never stop rolling (never reach a resting point). His second law of motion is that a force is equivalent to its mass times acceleration and that gravitational acceleration on Earth is equivalent for all objects. For example, if you drop a pen and a ball from the same height, it would experience the same acceleration. Newton’s third law is that for every acting force, there is a reacting force. For example, if one pushes on a wall with a force, the wall pushes back at the same amount of force.

Newton then applied his laws to planetary objects by claiming that the force of gravity between two objects is proportional to the product of the two masses divided by the square the distance between the two objects. He used this to explain the motion of planetary objects and it helped support the idea of a heliocentric model. This was a breakthrough because in combination with Kepler’s three laws of planetary motion it helped to affirm the fact the planets have an elliptical orbit. It also helped Newton believe that the Earth is a spherical object.

Figure 3 - Newton's Law of Universal Gravitation

A main reason for Newton’s many scientific disputes is his tendency to publish papers only after someone published something similar. Three scientists, Christopher Wren, Robert Hooke, and Edmond Halley disagreed over Newton’s idea of elliptical orbits due to the gravitational force of the Sun, which varied planet-to-planet. Hooke was one who argued with Newton over who discovered the inverse square law and elliptical orbits first; the dispute only ended due to Hooke’s death in 1703. ²

As much as Newton did for the field of science, he also contributed to the mathematical field with his development of calculus. However, Gottfried Leibniz claimed to have developed his theory of calculus first because it was published first, though Newton claimed he developed it first but kept it to himself as he so often does. Though Leibniz published his work almost ten years before Newton did, at the time Newton’s work was published it was the more accepted due to the bias toward Newton. Although in present day, it is Leibniz’s notation and his way of writing calculus that is widely used. In my opinion, it is Leibniz that deserves most of the praise because it is the notation that is widely used in present day. In the situation of a person who first made a discovery but kept it secret, or the one who made it later and announced it first, I believe the one who announced it first should be acknowledged as the real discoverer because he or she is the only one that has distinct proof that it was their theory that was developed first. ⁴  

References:

¹ http://www.universetoday.com/38643/what-did-isaac-newton-discover/

² http://space.about.com/cs/astronomyhistory/a/isaacnewtonbio_2.htm

³ http://galileo.phys.virginia.edu/classes/152.mf1i.spring02/KeplersLaws.htm
⁴ http://www.storyofmathematics.com/17th_leibniz.html

Images From:
Figure 1: http://www.crystalinks.com/newton.html
Figure 2: http://kepler.nasa.gov/Mission/JohannesKepler/
Figure 3: https://www.learner.org/courses/physics/visual/visual.html?shortname=figure6

Assignment #2 - The Copernican Revolution

Mikolaj Kopernik, or more well known as Nicolaus Copernicus, was a Polish astronomer and mathematician who lived from 1473-1543. He is well known for developing a heliocentric version of the solar system. However, the heliocentric model he is most known for was not particularly a new idea as others, like Aristarchus of Samos and Nicholas of Cusa, also proposed similar heliocentric theories but Copernicus was the one who developed mathematical backing to his theories. Copernicus targeted at establishing a few theories. First, that the Earth is spinning around its axis every day, while the immense distant world of stars is motionless. Second, the Earth is a planet orbiting the Sun once a year like the other planets, so it is not in the centre of the universe. Lastly, the Sun does not orbit around the Earth, but remains motionless in the centre of the planetary system.  

Copernicus was able to prove these theses through the means of observations over a long period of time. Within his book, he explains that the Earth must be rotating on its axis every 24 hours due to the movement of the stars in the sky around the Earth. Copernicus also observed that the other planets depicted the same orbit around the Sun that the Earth had shown. Although, Copernicus believed that these orbits were perfect circles (which was later disproven by Johannes Kepler). This furthered his belief of a heliocentric model against the Ptolemaic geocentric theory. Copernicus mainly used observations more than any mathematics or physics as his mathematical findings were used for the description of the planet’s motion.

Of the three theses, the last statement that the Sun does not orbit around the Earth, but rather remains motionless in the centre of the planetary system proved the most important to the field. Although Copernicus attempted to disprove the geocentric model with his heliocentric model, his model could not predict the positions of the planets any more accurately than the Ptolemaic model. In addition, the Copernican model’s inclusion of uniform circular motion was inaccurate. This meant that he established Earth as a planet but it also meant that all planets were treated as equal. By establishing the Sun at the centre of the universe and the Earth as a planet, it provided a stepping-stone that was used for many astronomers in the future. Through the observational work of Tycho Brahe and the mathematical genius of Johannes Kepler and Isaac Newton, Copernicus’ heliocentric model was transformed into the established ideas of our solar system in the present.

References:
http://csep10.phys.utk.edu/astr161/lect/retrograde/copernican.html
http://scienceworld.wolfram.com/biography/Copernicus.html