Microscopic atoms exhibit many strange quantum effects that make biochemistry possible, and biochemistry keeps macroscopic cats alive. Yet while we accept bizarre quantum behavior from atoms because it explains our experimental data and because we have no other alternative, we would be shocked if we saw cats exhibiting the same quantum weirdness we accept from the atoms that form them. The great QM physicist Erwin Schrodinger said this distinction is an illusion and in fact cats can, should and do exhibit the same quantum weirdness as the atoms from which they are made. (And the cat weirdness he was talking about wasn’t them chasing the bright spot of a QM-based laser pointer, either.)
Schrodinger envisioned a thought experiment now called Schrodinger’s Cat where a cat was placed in a box with a tank of posion gas having a valve controlled by a Geiger counter watching for the decay or splitting of a single radioactive atom. As soon as the box is closed, the radioactive atom becomes subject to the laws of QM and exists simultaneously in both a split and unsplit condition which persists until an observer opens the box again to check the reading on the Geiger counter – and the fate of the cat. (In QM, the act of conscious observation seems to be a key component in the “future-present-past funnel” described above.) But in the closed box, if the radioactive atom is both split and unsplit simultaneously, then the the valve is both open and closed simultaneously and the cat is both dead and alive simultaneously – or actually, in some kind of ghostly state we would call “deadalive” if we could ever see it, which we can’t.
Nobody has ever built a Schrodinger’s Cat experiment for real because a cat is too big – spans too many “powers of ten” or “orders of magnitude” in size – to exhibit observable quantum weirdness in a lab. A smaller experimental setup using a blood-cell sized mirror that would get “observably quantum weird” instead of a cat, however, is now believed to be feasible to build and is currently under discussion among physicists. From the CERN press release linked above: “Scientists from the University of Oxford, UK, and the University of California, Santa Barbara, US, have designed a “Schrdinger’s cat” that would be the largest quantum mechanical object ever seen. The team, led by Roger Penrose and Dik Bouwmeester, has proposed an experiment that uses an interferometer to split a light beam, with mirrors to reflect the two halves so that they recombine, their waves either adding together or cancelling. In the proposed experiment, the two-fold path of each photon leads to a pair of mirrored cavities in which the photon is reflected back and forth. In one of these cavities, one mirror is just 10 mm wide and mounted on a cantilever such that it moves if a photon strikes it. This mirror is the cat. If the photon behaved classically it would just follow one of the paths, but because it is a superposition it follows both, simultaneously making the mirror move and leaving it undisturbed. [Measuring if the mirror is in some position other than fully deflected of undisturbed would be “proof” that the Schrodinger Cat thought experiment was/is indeed valid.] If this [mirror] experiment proves feasible [it is still under study, not being built], it would extend the validity of quantum mechanics by nine orders of magnitude – to an object [the mirror] the size of a blood cell.” If this mirror experiment is built and works, it would become one of the classic physics experiments ever performed, and besides becoming one for the textbooks, would have profound impact on our philosophical beliefs about reality itself.