Physics Before Relativity

X-ray plate of a frog, 1896
YPM 1.175
Taken by A.W. Wright

 

One hundred years ago, Albert Einstein formulated his Theory of Special Relativity. This theory revolutionized 20th century physics. But even earlier physicists were discovering new phenomena that challenged the foundations of classical physics. These discoveries set the stage for Einstein’s work.

X-ray print of the hand of Mr. H.A. Bumstead, 1896
YPM 1.161
Taken by A.W. Wright

 

Vacuum technology also improved in the 19th century, mainly through the work of William Crookes, who developed the Crookes' Tube.

Physicists had long known that the inside of a vacuum tube would glow when an electric current passed through it. In 1895 Wilhelm Röntgen connected a Ruhmkorff induction coil to a Crookes’ Tube and discovered that any fluorescent material outside the tube would also glow. Knowing that whatever was emanating from the tube was not light, he simply called these rays “X.”

After much experimenting, Röntgen placed a photographic plate between the tube and the fluorescent material and asked his wife to put her hand in front of the plate, thereby creating the first X-ray of a human hand. Within a few months physicists at Yale University replicated the experiment, and produced a series of X-ray plates. Some of these plates are displayed in the exhibit.

Astatic Double Needle Galvanometer
YPM 1.440
Deleuil, Paris

 

Magnetism has been observed since antiquity, but the relationship between magnetism and electricity was only revealed in 1820 when Christian Øersted observed that an electric current could deflect a compass needle. Øersted’s discovery created interest in the new study of electromagnetism, and greater interest in galvanometry.

A galvanometer is a device that can detect and measure the presence, strength and direction of an electric current. It was one of the first tools used to study the physical properties of electric currents even before Øersted’s findings. Such devices helped later physicists like Georg Simon Ohm to formulate laws for measuring the strength of electric currents.

Railroad Tube with enlarged detail showing interior wheel
YPM 5.201
Maker and date unknown

 

The vacuum tube contributed to another famous and very important discovery. Crookes had already found that the glow inside a vacuum tube could be bent with a magnetic field. In 1897 Joseph John Thomson studied this phenomenon and concluded that the glow was caused by charged particles.

Thomson soon discovered that these particles, later named “electrons,” had mass and momentum. Momentum can be demonstrated using a Railway Tube: the electrons, which emanate from the cathode (or negative end) of the tube, move towards the anode (the positive end), hit the paddles and push the wheel along the tracks.

Electric Motor, 4 coils
YPM 1.9
Mid-1800s

 

Michael Faraday applied the findings of Øersted and Marie Antoine Ampére to convert electromagnetic energy into mechanical energy, a process called induction. Faraday’s theories led Hippolyte Pixii (and later Charles Wheatstone) to build an electromagnetic generator, a device that went on to transform industry and eventually brought electricity into homes.

Electromagnetic motors, like the one shown here, were also developed during the 19th century as prototypes for future domestic and industrial machinery.

Visit the Division of Historical Scientific Instruments to see other items in the Yale Peabody Museum’s collections.