Michelson and Morley conducted an experiment using an interferometer to attempt to detect the motion of the Earth through the hypothesized luminiferous aether. Their improved design situated the device on a stable stone slab floating on mercury to reduce vibrations. The experiment found no difference in the travel times of light beams projected in different directions, disproving the existence of the aether and demonstrating that the speed of light is constant regardless of the observer's motion.

2. • To attempt to measure the motion of the
Earth through the “Aether”, the non-
viscous, invisible, and incompressible
medium through which light waves were
thought to propagate
 If the apparatus is moving through the Aether,
parallel to one of the beams, there would be a
delay between the arrivals of the two beams

3. • Albert Michelson’s design was not sensitive enough
• Vibrations of footsteps from the surrounding area was
skewing the results
https://perg.phys.ksu.edu/vqm/laser
web/ch-10/10-1.gif

4.  Teamed up with Edward Morley to create a
better design
 Situated the interferometer on a large stone
slab which floated on a pool of mercury

5.  This significantly increased the reliability of the
results
http://upload.wikimedia.org/wikipedia/com
mons/8/8a/On_the_Relative_Motion_of_the_
Earth_and_the_Luminiferous_Ether_-
_Fig_3.png

6.  No delay between the beams regardless of
which direction the interferometer was
positioned
 Demonstrated that the speed of light is the
same for all observers
 Disproved the existence of the Aether

7.  Large-scale interferometers are used today in
an attempt to prove the existence of
gravitational waves, predicted by Albert
Einstein
 These interferometers have arms spanning
roughly 4km each, allowing them to detect
length changes of up to one hundred-millionth
of the diameter of a hydrogen atom