Gravitational Wave Detector

The Design Challenge

The challenge is to perform a Michelson Morley experiment to measure Gravitational Waves. This interferometer, although used to find the presence and properties of a substance called the luminiferous aether, is now used to detect Gravitational Waves. After constructing the interferometer, the data collected from the experiment will be compared to the data from LIGO, the Laser Interferometer Gravitational-Wave Observatory. A conclusion can be therefore made about the properties of Spacetime curvature as well as the characteristics of black hole and neutron star binaries.

Summary of Research

There are four categories of gravitational waves which are: Continuous Gravitational Waves, Compact Binary Inspiral Gravitational Waves, Stochastic Gravitational Waves, and Burst Gravitational Waves. The main gravitational wave that LIGO detects are Compact Binary Inspiral Gravitational Waves.

According to the LIGO Scientific Collaboration, there have been 11 detections since 2015. There have been 9 binary black hole detections and 2 binary neutron star detections. The first gravitational wave detection from two merging black holes was on September 14, 2015. This detection is called GW150914, with two black holes each with around 30 solar masses where the frequency rose from 35 to 250 Hz with a peak gravitational-wave strain of 1.0×10⁻²¹. The first neutron star merger was on August 17, 2017, and is called GW170817. This was the first detection of a binary neutron star and the first time that a cosmic event was observed with both gravitational waves and light; LIGO observed gravitational waves and various telescopes observed the electromagnetic emission (light) from the resulting collision in multiple wavelength bands. 

The Michelson-Morley Experiment was initially designed to find the “luminiferous ether”, which was a medium that people imagined to exist for light waves. In the experiment, a light beam is shot out and travels towards a  beam splitter, which splits the light beam into two. After the light beam is split into two, one of the beams travels to one mirror and the other beam travels to the other mirror. Once both light beams are reflected by the mirrors, the light travels back to the beam splitter. When they reach the beam splitter, the two light beams merge back into one. This single beam will be displayed on a screen. This is the same concept that LIGO uses for its gravitational detector.

This is my final prototype. The two mirrors are 12 cm apart and all the items are level. The light beam travels parallel to the ground and merges at the same point. The merged light beam creates a fringe pattern.

This is the fringe pattern of the interference of light waves in superposition. Superposition is a principle where two or more waves overlap in space and the resultant disturbance is equal to the algebraic sum of the individual disturbances. In this image, you can observe the constructive and destructive interferences of light. The constructive interferences occur when the two light waves are in phase. This is seen where there are red horizontal lines. On the other hand, destructive interference occurs when the light waves are out of phase, resulting in little or no light on the fringe pattern. 

More information and all the sources are on the journal

Link to Process Journal & Final Reflection Video

Link to Journal