PHY1401 Gravitational Acceleration Research Paper of Physics Research Paper on a Selected Topic in Physics o Choose a topic within the realm of physics, p

PHY1401 Gravitational Acceleration Research Paper of Physics Research Paper on a Selected Topic in Physics

o Choose a topic within the realm of physics, preferably one that truly interests you.

§ The topic can be a person, event, or concept.
§ The topic does not have to be one we cover in this class (i.e., although we did not coverastronomy, you can still choose a topic in astronomy, since it is within the realm of physics).

o Examples of possible topics :blackholes, IsaacNewton, gravity, soundwaves, Galileo, detection of

neutrino particles, semiconductors, etc.
o Research your topic using at least four references.

§ One of the references must be our textbook. Type a report summarizing your research on the topic.

§ You will be graded on the content of the paper, the flow of the writing, and grammar and spelling.
§ For your reference, a sample paper is available on Blackboard.

o Reportrequirements:

§ Standard font type and size (10-12 pt)
§ 1.5-line spacing; 1-inch margins maximum
§ Suggested length: 1.5 to 3 pages
§ List of references must be included
§ Must be submitted in hard copy form
§ Figures are not required, but you are encouraged to use them if it helps to convey a certain concept

SAMPLE PAPER AND GRADING CRITERIA IS ATTACHED The Michelson-Morley Experiment: An Experimental Overview
Written October 2017 by Charli Rust
Introduction
The notable history of the Michelson-Morley experiment of 1887 illustrates the notion that, in science, a
null result can nevertheless be a significant one. Until the late 19th century, many physicists wholeheartedly
believed in the existence of an invisible, massless medium through which light waves propagated. This
mysterious medium was referred to as the luminiferous aether (or “ether”). The first scientists to carry out
successful experiments regarding the so-called ether were Albert A. Michelson and Edward W. Morley, using an
instrument called an interferometer to measure the properties of light [1]. The significance of their results not only
shocked many scientists around the world, but it earned Michelson the Nobel Prize in Physics in 1907, the first of
such an award to be given to an American [2]. The purpose of this essay is to summarize the mechanics and
significance of the Michelson-Morley experiment of 1887.
Background
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th
Physicists of the 18 and 19 centuries were aware that a medium was needed in the propagation of
mechanical waves (such as seismic or sound waves), and they assumed that a medium of an analogous sort was
required for the propagation of light waves [1]. In pursuit of evidence of the ether, it was believed that an
experiment could be designed to measure Earth’s velocity through the ether. The idea was that the relative
velocity between the ether and the Earth’s frame of reference could be calculated.
One proposed idea was to experimentally measure the upstream-downstream time for the propagation of a
light wave (i.e., the velocity of a light wave moving parallel to Earth’s rotation), and to compare the result to the
cross-stream time for the propagation of a light wave (i.e., the velocity of a light wave moving perpendicular to
Earth’s rotation) [1]. Figure 1 illustrates this proposed motion of the ether.
Figure 1: Illustration of the motion of the ether with respect to Earth’s motion.
Experimental Setup
The experimental setup of the instrument Michelson conceived, called an interferometer, begins with a
light source that travels to a beam-splitting mirror which splits the light into two beams, one parallel to the
original direction and one perpendicular to the original direction. Upon being reflected by secondary mirrors, the
two split beams travel back to the mirror and recombine, causing observable “fringe” patterns depending on the
distance that each individual light beam travels. Bright bands correspond to two wavelength maxima adding
together (constructive interference), whereas dark bands correspond to a cancellation effect (destructive
interference). Figures 2 and 3 illustrate the basic design of the original Michelson-Morley experiment.
Figure 2: Sketch of the experiment.
Figure 3: Schematic diagram of the interferometer.
In Figure 3 (a birds-eye view), light is emitted from a source at point S. At point A, the light is split into
two separate beams. One light beam travels to a mirror at point B while the other travels to a mirror at point C.
Upon reflection of each light beam back to point A, the light beams recombine to form a single light beam, which
enters the observer’s view. By keeping the distances AC and AB equal, it was believed that there would be a
measurable time difference between the parallel and perpendicular paths of the light waves due to the presence of
the ether. Ingeniously, Michelson and Morley decided to rotate the apparatus exactly 90 degrees such that the
parallel path before rotation became the perpendicular path after rotation.
They performed the experiment and recorded their results, then repeated the experiment six months later.
Michelson and Morley failed to observe the Earth’s motion through the postulated ether, a conclusion made from
the inexistence of an observable change in the fringe pattern.
Discussion and Conclusion
Michelson and Morley failed to detect any observable motion of the Earth relative to the ether. The
upstream-downstream and cross-stream velocities did not add in the way that intuition would suggest, and the
result ultimately led to the disposal of the ether hypothesis. Despite the null result obtained, the tool the
experimentalists designed has become a useful instrument to measure microscopic distances with incredible
precision. The negative result also led to other areas of important scientific research, such as the special theory of
relativity [1].
The purpose of this essay was to summarize the Michelson-Morley experiment of 1887. American
physicists Albert A. Michelson and Edward W. Morley obtained a null result in the measurement of the ether,
implying that the ether was totally nonexistent. It was shown that a null result does not equal failure in science;
rather, it may in fact lead to revolutionary thinking. The talents and contributions of Michelson and Morley were
many. For example, Michelson’s work led to some of the most accurate measurements of the speed of light at the
time, and in 1920, he used an advanced version of the interferometer to determine the diameter of the well-known
star Betelgeuse, with a diameter 1000 times that of the Sun. Michelson’s measurement was considered to be the
first accurate measurement of the size of a star [2].
References
1. K. Krane, Modern Physics 3rd Edition, John Wiley & Sons, Inc., February 2012.
2. “Albert A. Michelson – Biographical”, Nobelprize.org, Nobel Media AB 2014, accessed 2017.
(http://www.nobelprize.org/nobel_prizes/physics/laureates/1907/michelson-bio.html)
PHYS 1401
College Physics I
Research Paper Grading Rubric
Category
Points
Points
Remarks
Possible Earned
Introduction
10
Flow of Writing
20
Relevance of
Content
40
Spelling &
Grammar
10
Formatting
10
References
10
Grade

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