A pioneer in quantum physics born on this day in 1877, Schrodinger put his theoretical cat in a theoretical box to illustrate a paradox of quantum mechanics.
The cat is enclosed in a box with a radioactive device that could trigger a mechanical device that would kill the cat.
Paradoxically, at least in a quantum universe, the cat is simultaneously alive and dead until the experimenter "knows" whether an atom in the radioactive device has decayed, leading to the death of the cat.
Schrodinger was pointing out the strangeness of the prevailing interpretation of the indeterminate behavior of fundamental particles; that a quantum particle exists in many possible states until the moment we observe it.
As long as the electron remains unobserved -- and thus undisturbed -- it hangs in limbo, occupying all of its possible states, at least under the laws of quantum mechanics.
Schrodinger's cat, by extension, is both dead and alive.
Schrodinger, a native of Vienna who worked for a brief time alongside Albert Einstein, also developed what is called Schrodinger's wave equation -- an important discovery in the field of quantum mechanics for which he shared the 1933 Nobel Prize for Physics.
He died in 1961.