Discovery of the Expanding Universe

For many centuries, scientists and astronomers have been battling over the question of how old and big the universe is? The ancient Greek civilizations came to the realization of how difficult it was to vision a infinite universe and what it would look like.

Georges Lemaitre

Sourced From: http://www.physicsoftheuniverse.com/scientists_lemaitre.html

Georges Lemaitre was a catholic priest and a Belgium cosmologist. He was born in 1894 in Charleroi, Belgium and even as a young boy he had a passion for science[1]. He completed his primary education at College du Sacre-Coeur which was located in Charleroi and later wen on to study at the catholic university of Louvain focusing on civil engineering at the age of 17[2]. As World War 1 began it unfortunately interrupted his education as he served as a artillery officer and witnessed the first poison gas attack in history. After the war he returned back to school and decided to focus his studies theoretical physics[1]. During the same time of his schooling he also worked on becoming a priest and by the year 1923 he was ordained a catholic priest. After being ordained he continued on in school to graduate studies in Astronomy at University of Cambridge which is located in England[2]. In 1924 he migrated to America and studied at the Massachusetts Institute of Technology. In the 1925, at the age of 31[1], Georges Lemaitre became a professor at the University of Louvian where he originally completed his studies at. Due to an injury he sustained in war, he was able secure his position as a teacher and he had a strong passion to teach[2]. Lemaitre had very strong religious beliefs but his love for science was that much stronger[3]. Einstein had already theorized about General Relativity and in 1927 Georges Lemaitre published a research paper that went unheard of but it went in depth in a solution to the equations of General Relativity specifically the case of an expanding universe.

Unfortunately, a Russian scientist by the name Alexander Friedmann had already derived he solution prior in 1922 which is 5 years earlier. Although Friedmann had a higher interest in the physics and mathematics of the solutions and possible expanding and contracting universes theoretically. Friedmann did not apply his solution to the physical universe. However, Lemaitre produced his solution with the sole purpose of explaining the cosmos and he realized that his solutions predicted the expansion of the real universe.

Edwin Hubble, another famous astronomer, in 1929 published his official report after discovering a redshift in the light emitted from distant galaxies further proving Lemaitres expanding universe theory. Lemaitre published his research in 1927 but it wasn't until astronomer Arthur Eddington who widely publicized the theory on again in 1931 by translating it and republishing it in English.

Later that year, Lemaitre further explored into our expanding universe and came to bold proposal that the universe originated at one point as a single particle. This theory came to be known as " The Big Bang Theory"

This is theory had some friction with other scientist when it was initial proposed. Einstein did not approve of the theory initially because he didn't agree with the physics but he did accept the argument that the static model that he proposed could explain indefinitely into the past. Although the theory caught on in later years by the media and Lemaitre obtained much praise for it.

Lemaitre eventually gave up his teaching career and retired but still continued to work on his calculations and developed an interest in computer language and sciences. He passed away on June 20, 1966 after the discovery of cosmic radio microwaves which further proved his theory[2].


Friedmann

Sourced From: http://www.physicsoftheuniverse.com/scientists_friedmann.html

Alexander Friedmann was born on June 16, 1888 in Russia and he known as a cosmologist and mathematician. Through out his career he developed many model that explained the universe and its development. He is also widely known in the scientific communtiy for his solutions to Albert Einstein's general relativity equations which provided early evidence of the Big Bang Theory and steady state model of the universe.

Alexander excelled in his studies both in highschool and at Saint Petersburg State University. Friendmann studied mathematics in university from 1906 to 1910 as well as attending Paul Ehrenfest's modern physics seminars. These seminars discussed in great detail about quantum theory, relativity, and statistical mechanics. In 1914 he graduated and received his master's degree in applied and pure mathematics.

While completing his graduate studies in 1913 he was given a position at the Aerological Observatory in Saint Petersberg, which was known for meteorology. At this observatory he studied theoretical meteorology and took part in many expeditions around the earth skies making meteorological observations. As Friedmann graduated, that same year the world war 1 had began and Alexander Friedmann decided to volunteer for the Russian army, specifically in the air force as a bomber pilot. After 1915 he decided to lecture pilots on the topic of aerodynamics and later taught mathematics and mechanics at Petrograd University. Once a professor he became very aware with Einsteins Theory of Relativity and in 1922 he discovered the solutions to the field equations of the expanding universe[4]. Einstein did not approve of the calculations that Friedmann made and sent a letter to the German Physics Journal saying that Friedmann's work was suspicious. Afterwords Friend sent Einstein proof of his work in a detailed letter and six months later Einstein wrote in the journal and apology saying that he himself made mistakes in his calculations.[5]

Friedmann published papers in 1924 which demonstrated 3 models of the universe with positive, zero, and negative space time curvature. These cosmological models helped explain general relativity and the big bang theory. In 1924 he also became a director of Main Geophysical Observatory in Leningrad where he met George Gamow who was a Russian physicist and cosmologist and he stuided under Friedmann for a number of years. Unfortunately for Alexander Friedmann on September 16, 1925 he was diagnosed with typhoid fever and suffered a tragic death[4].

George Gamow

Sourced From: http://www.physicsoftheuniverse.com/scientists_gamow.html

Geogre Gamow, born on March 4, 1904, was theoretical physicist who studied under Alexander Friedmann. He had many predictions about the cosmic microwave background radiation and he explained about the levels of hydrogen and helium in the universe. The explanations provided important evidence and support to the Big Bang Theory.

In 1948, George Gamow published a research paper that was very important in the world of theoretic physics. His paper about the universe was entitled "The Origin of Chemical Elements" and in it he explains the present levels of the element hydrogen and helium saying that they made up 99% of all matter in the universe. He also mentioned that this make up of the universe was due to the reactions that occured in the initial stages of the Big Bang. In the same paper he published a prediction of the cosmic microwave background radiation saying that after billions of years the radiation filling the universe would have cooled down to about 5 degrees above absolute zero. Surprisingly, in 1965 when cosmic microwave background radiation was accidentally discovered, that they were 2.7 degrees above absolute zero which was very accurate to the predictions.[6]


3 models of the Universe

Soured from: http://abyss.uoregon.edu/~js/cosmo/lectures/lec15.html

Positive Curvature - Spherical

Negative Curvature - Hyperbolic or saddled shape

Zero curvature - flat

According to the Friedmann Equations the shape of the universe depended on the overall mass / energy in relation to critical density [5]

Sources:

1. http://www.amnh.org/education/resources/rfl/web/essaybooks/cosmic/p_lemaitre.html
2. http://www.pbs.org/wgbh/aso/databank/entries/dp27bi.html
3. http://www.physicsoftheuniverse.com/scientists_lemaitre.html
4. http://www.physicsoftheuniverse.com/scientists_friedmann.html
5. http://www.decodedscience.com/alexander-friedmann-unsung-hero-of-modern-cosmology/19423
6. http://www.physicsoftheuniverse.com/scientists_gamow.html
7. http://abyss.uoregon.edu/~js/cosmo/lectures/lec15.html

The Changing Pluto

History of Pluto



sourced from: http://interviewly.com/i/nasas-new-horizons-oct-2014-reddit

Pluto was once recognized as one of nine major planets orbiting the sun but is now only considered as a dwarf planet. In modern day astronomy, Pluto is seen as one of the largest members of the Kuiper Belt [1]. The Kuiper belt is a disc shaped ring and its a region of icy objects located billions of kilometers away from the sun [2].

Pluto was once classified as the ninth planet in our solar system therefore being extremely far away from our earth. Due to the enormous distance, there's is little information about the planets size or surface condition. According to the article in www.space.com, Pluto is estimated to have a diameter equivalent to less than one fifth of the Earth. It guesses that Pluto's surface probably contains ices of various composition such as methane and nitrogen at the surface, a mantle of water ice under the surface, and a rocky core at the center. NASA's hubble space telescope has been able to provide observations and evidence of the different compositions of gas.

This Hubble Space telescope from NASA has shown that Pluto has a very eccentric orbits therefore creating huge variance in distance from the sun as well as penetrating the planet Neptune's orbit. As Pluto orbits closer to the sun, the ice on the surface of the planets temporarily melts and forms a thin atmosphere around the planet containing mostly nitrogen and methane. Due to Pluto's extremely low gravity causes the temporary atmosphere to extend higher than earths atmosphere. While Pluto has its atmosphere, it can apparently experience strong winds. Once Pluto orbits further away from the sun, it's atmosphere beings to freeze and eventually disappears. Pluto apparently has one of the most cold surfaces in the entire solar systems with approximately 375 degrees Fahrenheit below zero. Astronomers also discovered that Pluto had a very large moon and they have a very short distance between each other in terms of other planets and their moons.[1]

Discovery of Pluto


Sourced by: http://sciencefiction.com/2014/10/12/pluto-may-just-fact-planet/

Pluto was discovered less than 100 years ago, which is very recent in terms our known existence. An astronomer at the Lowell Observatory in Flagstaff, Arizona by the name, Clyde W. Tombaugh, discovered the planet on February 18, 1930. Originally, it was an American Astronomer by the name Percival Lowell who proposed that there was another planetary body somewhere in the range of Neptune and Uranus because he had observed something affecting the orbits of the two planets have been the gravitational pull of something large. Lowell referred to the large body as "Planet X" in 1905 and unfortunately died in 1916, sadly never being able to discover the planet.[3]

More than a decade later the Lowell Observatory decided to continue on with research of "Planet X" done by Percival Lowell, the founder of the observatory. Clyde W. Tombaugh was hired to discover the existence of this unfounded planet using a 13-inch telescope that the Observatory had built just for the purpose of it's discovery. Tombaugh had to contribute an immense number hours and hard work before discovering the planet Pluto. On February 18, 1930 Tombaugh was able to examine the photographic plates that were outputted by the telescope. The Lowell Observatory was not ready to announce the discovery until more research took place and on March 13,1930, which would have been Percival Lowell;s 75th birthday, they confirmed the discovery.[3]

The "Planet X" eventually needed a name and was chosen by an  11 year old girl, Venetia Burney. The name "Pluto" often refers to the roman god of the underworld which fit due to the similar surface conditions of the planet. The name also hon ours Percival Lowell because the first two letters in "Pluto" and his initials. [3]

Sourced From :http://www.icollector.com/Clyde-W-Tombaugh_i11385124

Clyde W Tombaugh also discovered many galaxies and clusters of stars with this improved telescope. He also made various observations of the surfaces on Mars, Venus, Saturn, Jupiter, and the moon. After the discovery of Pluto, Tombaugh attended the University of Kansas and going on to receive his M.A. in astronomy. After graduation he returned back to the observatory to continue his astronomical work and he cataloged over 30,000 objects in the universe. He also went on to teaching at a few colleges and university. Even when he decided to retire he still continued to observe the sky and advise the university. [4]

As mentioned before the telescope used in the discovery of Pluto at the Lowell Observatory was very advanced and it was equipped with photography. This camera within the telescope was used to take two pictures of the sky on various days. They also used a device known as a blink comparator which switch views between pictures rapidly. In these pictures, the stars and galaxies were stationary but orbiting objects could be identified due to the motion across the sky. Apparently, Clyde W. Tombaugh close to 7000 hours analyzing each pair of photos which contained 150000 to 1 million stars in a single photo. After precise measurements and study, Tombaugh was able to identify the movement of one particular object[5].


The discovery of Pluto was not a true theoretical predication based on celestial mechanics. The Titus Bode law explained the approximate distance from planet to planet going away from the sun. Using Newtonian physics and the Titus Bode law, the planets and their distances from each other made sense. Astronomers noticed that there was a supposed "missing planet" between mars and Jupiter that should be in place rather than a gap. Guiseppe  Piazzi in  1801 discovered Ceres, a large asteroid/ minor planet, and many other minor planets forming and asteroid belt. Mathematical astronomers used the Titus bode law to explain the gap between mars and Jupiter. The law also pointed out that there should another planet after Jupiter and due to this theory astronomers later found Uranus.[6]

Le Verrier, another famous astronomers noticed that the orbit of Uranus didn't match its theorized paths as well as Neptune which was found due to this reason very reason. At the time Le verrier used Titus Bode Law to predict the paths of Neptune and Uranus and published his predictions. However with modern day science we figure out that Uranus, Neptune, and Pluto do not follow the Titus Bode law, therefore proving that Le Verrier and other astronomer's findings completely luck. Even the discovery of Pluto was due to luck.[7]

Changes to Plutos Discovery

Originally, Pluto was thought to be a similar size as the earth and therefore there was no question about it being a ninth planet. It was considered as the ninth planet in our solar system for 70 years. In 1978 astronomers discovered Pluto's largest moon, Charon. With this discovery they were able to approximate Pluto size at around 2400 km, which would make it the smallest planet in our solar system but the largest object past the orbit of Neptune. With advances in technology and observatories, astronomers were able to find many other celestial objects similar to Pluto and its moon in the Kuiper belt. There are approximately 70000 icy object with the same composition as Pluto within this Kuiper belt that extends out from the orbit of Neptune to 55 AU.

Astronomers had to decide on what exactly was the definition of a planet. There are three criteria that a celestial object has to meet to be considered a planet:
1. It needs to be in orbit around the sun
2. It has to have a strong enough gravitational pull to form itself into a sphere
3. It needs to have a clear dominant gravitational orbit

Unfortunately, Pluto did not meet the third criteria because it is in orbit along with tens of thousands of other objects in the kuiper belt. Astronomers decided that any celestial objects that also dont meet the third requirement is considered a dwarf planet. [9]


Plutinos

"Pluto and Eris were the first worlds to be classified as Plutoids, a special class of dwarf planets that orbit our sun in the icy region beyond the orbit of Neptune"[10]. Terrestrial planets are small rock and metallic objects orbiting close to the sun and Jovian planets are large objects with low density mainly made up of liquid composition, gases, and ices. Pluto is definitely not Terrestrial and is similar to a Jovian planet but because of its size cannot be classified as Jovian either. Due to this problem, astronomers have decided to create a new classification known as "Plutoids" to classify other objects like Pluto. Plutinos is a sub category of Plutoids but they are distinguished by the distinct way they orbit the sun. Pluto orbits in a perfect whole number ratio of 3 to 2 for the length of its orbital period compared to that of Neptune. Plutinos all share a similar ratio in orbital period either 3 to 2 or 4 to 3 or 2 to 1 but in any case it's a ratio of whole number.[10]




Sources (footnotes)

1. http://www.space.com/43-pluto-the-ninth-planet-that-was-a-dwarf.html
2. http://solarsystem.nasa.gov/planets/profile.cfm?Object=KBOs
3. http://history1900s.about.com/od/1930s/qt/Pluto.htm
4. http://www.britannica.com/EBchecked/topic/598927/Clyde-W-Tombaugh
5. http://ircamera.as.arizona.edu/NatSci102/NatSci102/lectures/pluto.htm
6. http://www.space.com/19824-clyde-tombaugh.html
7. http://www.fromquarkstoquasars.com/that-pluto-controversy/
8. http://www.splung.com/content/sid/7/page/solarsystem
9. http://www.universetoday.com/13573/why-pluto-is-no-longer-a-planet/
10. https://solarsystem.nasa.gov/multimedia/display.cfm?IM_ID=6823