6.1 The Search of Ether: The Michelson-Morley Experiment

REPORT BY J. MUNCAL / K. NONO / A. ROSARIO

“Light is transmitted at a limited speed through the luminiferous aether wind”

-ISAAC NEWTON (1642 – 1727), “OPTICKS”

the Luminiferous Aether Wind

Aether : Latin – the upper or rarified air reaching through the heavens

Greek – to glow or burn

Absolute and stationary

easily compressible, “stiff” but lighttransparent

Permeates all matter and space

must also allow solid bodies to pass through

Michelson & Morley

AlbertAbrahamMichelson

became the firstAmerican toreceive a NobelPrize in Physics(1907 )

Edward W. Morley

collaborated withMichelson in thecreation of asecond “moreaccurate”interferometer

Michelson’s 1881 interferometer

Light source

Mirror 1

Mirror 2Detector

The idea behind the experiment

The Michelson interferometer

Interference pattern (light and dark parts)

The “failed” experiment

▶The result shows that the travel time of the two light beams were not different

▶Michelson conducted the experiment again, with E.W. Morley, using a more refined instrument which yielded the same results

▶Even though the experiment failed, it proved that the speed of light is constant

Several Hypotheses

▶The ether might be dragged along with the Earth

▶Everything is moving with respect to the Earth and the ether

▶The velocity of light is constant with respect to the source

▶The ether did not exist at all

6.2 Postulates of Einstein’s Theory of Relativity

Special Relativity

▶“The Electrodynamics of Moving bodies” (1905)

▶“special” since it applies only when the frames of reference are in constant unchanging motion

THE PRINCIPLE OF RELATIVITYAll inertial frames are equivalent with respect to all laws of physics.

The laws of Physics are true in all reference frames but experimental results depend on the nature of the experiment.

*there is no preferred reference frame*consequence - there is no absolute motion, which is motion of an object described by

its measurement in a frame of reference that is preferred over other frames of reference

THE PRINCIPLE OF INVARIANT LIGHT SPEEDThe speed of light is independent of the motion of the light source or receiver.

c = 3 x 108 m/s

Applications of Einstein’s Postulates

▶ a new concept of time, space, and light

▶ GPS, communication systems (time dilation)

Sources

▶ http://www.relativitycalculator.com/Albert_Michelson_Part_I.shtml

▶ http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/mmhist.html

▶ http://galileoandeinstein.physics.virginia.edu/lectures/michelson.html

▶ https://helix.northwestern.edu/article/einsteins-theory-relativity-implications-beyond-science

Albano, C.,et al. (1999). Introduction to Physicsand Chemistry. Diliman, Quezon City: UPDiliman Learning Resource Center