Encounter 06 · 06 of 42 · 1887
The experiment that found nothing
In Cleveland in 1887 two men looked for an ether wind and published a null. They did not know what the nothing would later be asked to mean.
Cleveland, Ohio
Listen · Eve
The mirrors are still. What were they for, before any later theory?
Light was supposed to travel in an ether. If the Earth moved through that ether, two equal arms, rotated, should have shown a fringe shift. In 1881, at Potsdam, Michelson tried. The path was short. The cellar shook. He published a small result he did not treat as final.
What changed between attempts
- 1881, PotsdamA first interferometer. Expected shift on the order of 0.04 of a fringe. Vibration and a short path. Not a first whim; a first machine that could not yet answer.
- 1887, ClevelandWith Morley: a sandstone slab about five feet on a side, floating on mercury so it could turn without a jerk. Path about ten times longer. Expected shift on the order of 0.4 of a fringe.
Expected
Rotating the 1887 interferometer should have shown a fringe shift on the order of 0.4 of a fringe.
Observed
Noise on the order of 0.02. No significant ether drift. They published the null in the American Journal of Science, 1887.
They reported that the expected shift was not there.
1887
The notebook
A detection they had tuned the instrument to make did not occur. Other people kept measuring.
1905
A later kinematics
Einstein’s paper on special relativity does not open as a thank-you note to Cleveland. Lorentz and Fitzgerald offered contractions. Those sentences were not prizes in the 1887 notebook.1905 is afterward. The 1887 notebook is a null, not a prophecy.
A repeated attempt is not automatically perseverance. Ask what changed. Path length, isolation, a colleague. The null is still a null.
What if the attempt does not work, and that is the result?
Private. No one else will see it.
Source
- primary01 · A. A. Michelson & E. W. Morley“On the Relative Motion of the Earth and the Luminiferous Ether,” American Journal of Science, 1887.
Cleveland · ether wind · a published nothing