Independent Research Project #5
NATS1745A, Summer 2022
Prof. Rafiee
Edwin Hubble: a pioneer of Modern Cosmology.
Table of Contents
Introduction ....................................................................................................................................... 2
Discoveries/Observation .............................................................Ошибка! Закладка не определена.
What we know/basic facts .................................................................................................................. 2
What we don’t know/Open questions ................................................................................................ 3
Conclusion ......................................................................................................................................... 4
Bibliography....................................................................................................................................... 5
Introduction
General relatively theory and new observing techniques, especially large optical telescopes
positioned thousands of feet above sea level helped shape the modern science of cosmology in the
first three decades of the 20th century. Along with these major shifts in the filed of astronomy,
astronomers, physicist and mathematicians also made major changes to their theories and
observational methods. There were questions regarding the existence of other galaxies and
formation of the universe which were answered in the early years of the 20th century.[1]
Background History
Edwin Hubble, a scientist who was born in Marshfield, Missouri, on November 20, 1889, proved
that the Milky Way is only one of many galaxies and that the redshifts of galaxies rise with
distance. Hubble completed his education at Oxford and the University of Chicago. In accordance
with his father's desires, he pursued studies in law. Hubble pursued his own hobbies and enrolled in
astronomy school after the death of his father. He graduated from Chicago with a PhD in
astronomy in 1917 and temporarily served in the US Army before joining the Mount Wilson
observatory staff in California. The observatory’s 100-inch (254-cm) Hooker telescope, the most
powerful in the world, was used by Hubble to make observations. Through the observations mad
from the telescope he was able to provide enough and significant evidence to prove that there were
other galaxies in the universe and milky way was only a small part of the various galaxies.[2][3]
What we know/basic facts about his method
Hubble completed studying reflection nebula within the milky way galaxy, however soon returned
to studying the spiral nebulae, objects he investigated for his doctorate. The theory that these so
called spirals were other galaxies was not so well received in the 19th century, however, things
changed in 20th century. Although this theory received recognition, there was no evidence to fully
believe it. [2] In 1923, Hubble began concentrating on studying the novae of a spiral nebulae, he
found a Cepheid variable stars in the Andromeda Nebula. He used the connection between the
variable stars fluctuations' period and luminance to calculate the nebula's distance from these stars'
light fluctuations. According to him, Andromeda was approximately 900,000 light years away and
this estimation seemed to indicate that this galaxy was way further away from milky way galaxy
and clearly not within it. The Andromeda Nebula had to be a galaxy, not a nebulous cloud or a
small star cluster. Hubble's discoveries in the Andromeda Nebula and other comparatively close-by
spiral nebulae quickly persuaded most astronomers that the universe does, in fact, contain an
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infinite number of galaxies. (The Andromeda Galaxy, also called the Andromeda Nebula, is
currently thought to be 2.48 million light-years away. Most of the variation between the Hubble
estimate and the present estimate is explained by an improved Cepheid period-luminosity
association.)[1][2][3]
What we don’t know/errors and mistakes
One of the innovators of early 20th-century empirical cosmology is Edwin Hubble. He is
associated with several of significant discoveries made between 1920 and 1930 that are listed in
the majority of textbooks such as the classification of extragalactic nebulae, the finding that
extragalactic nebulae have a linear relationship between distance and velocity, giving the first
proof that the universe is expanding ,the brightness profile of galaxies. However, there was another
astronomer before Edwin Hubble who suggested that the universe was expanding.[5] In 1913, V.
M. Sipher found that the Andromeda Nebula was moving towards the solar system with a speed of
300 kilometers per second, this was faster compared to other stars in the milky way galaxy. This
was abnormal, if the nebula was nearby star and planetary system in formation. But instead of
publishing it in a major astronomical journal, he published it in the Lowell Observatory bulletin
briefly. By 1914, he had studied the velocities of 14 spiral nebula, while some seemed to be rapidly
moving towards us, others seemed to be moving further away. He was able to conclude with these
evidence at hand that these spiral nebula may not be part of the milky way galaxy and could be an
entirely different independent galaxy. In a meeting with 66 astronomers at Michigan Lake, Sipher
talked about his observations and theory, astronomers present were greatly impressed and gave him
an standing ovation. One of the astronomers present in this meeting was Edwin Hubble, therefore,
it is likely that inspired by Sipher he was able to extend his research. However, Hubble has not
credited Sipher, a reason for this could be that the unlike the current literature bibliography was not
compiled at the back of the article in the 1920’s. The work could be cited by the persons name at
the footer of the same page.[4][5]
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Conclusion
Astronomy has progressed as we have been able to discover numerous other galaxies and because
of astronomers like Edwin Hubble and V.M. Sipher we are aware of the big bang theory and how
was universe was formed. With the contributions of these great astronomers, there has been a
significant change in the field of astronomy. From, assuming that these spiral nebulae were part of
the milky way galaxy to finding out that there are various other galaxies in this universe,
astronomy has greatly progressed.[2][3]
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Bibliography
1. R. W. Smith, Edwin P. Hubble and the Transformation of Cosmology, Physics Today 43,
52-58 (1990).
2. R. Smith, Edwin Hubble . Encyclopedia Britannica,
https://www.britannica.com/biography/Edwin-Hubble
Accessed 28 March 2023.
3. American Institute of Physics, Edwin Hubble, Physics Today, https://physicstodayscitation-org.ezproxy.library.yorku.ca/do/10.1063/pt.6.6.20171120a/full/
Accessed 28 March 2023.
4. M. Bartusiak, The Cosmologist left behind: Edwin Hubble usually gets the credit, but Vesto
Slipher was the first to see the signs that the universe is expanding. Sky & Telescope, 118,
3, (2009).
5. M.J. Way, Dismantling Hubble’s legacy? ,Astronomical Society of Pacific, 471,(2013).
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