Science fiction stories often make use of miniaturization as a plot device and perhaps the best known example is the book and the film Fantastic Voyage. In this tale, a team and their submarine are reduced in size so as to be able to perform a delicate operation within a human body. One of the most extreme versions of shrinking occurred in Henry Hasse’s 1936 story “He who Shrank.” The protagonist of the story is subjected to an experiment which causes him to constantly shrink. The author of the story conjectured that the atoms of the world are made up of other worlds. So as the protagonist would, as he shrunk, appear as a giant in the universe just “below” the one he had left. In the story he wondered how far he would shrink-is there some ultimate limit to the size of an object or would he diminish for infinity?
According to our best theory, such shrinkage is not possible. While matter can be compressed (you can test this yourself with a slice of bread or a Styrofoam cup) there is supposed to be a limit on how far an atom can be compressed (matter is, as far as we can tell, made of atoms). This limit was postulated by Niels Bohr (see page 52-54 of What’s Science Ever Done for Us? for a very clear discussion of this matter). The gist is that electrons already orbit as close as possible to the atomic center. If an electron was any closer, it would strike the atomic center and thus matter would be in a great deal of trouble. To use an analogy, think of a satellite orbiting the earth. At a certain point it would be too close and would fall from orbit-plunging to a fiery end.
While a lot of math would be involved, it is easy enough to calculate how far a human being could be compressed before the limit postulated by Bohr would make further compression impossible. This limit, unfortunately, does not allow for enough compression to make the science fiction shrinkage possible. Naturally, even this lays aside the rather serious problem of keeping someone alive as they are being reduced.
Of course, another scientific hypothesis creates what might seem to be a possibility for getting small.
According to the “generic” big bang hypothesis, the entire universe began from a rather tiny bit of stuff. Now, if the entire universe was originally compressed into a tiny mass, then it could be argued that it could be recompressed. After all, if the big bang hypothesis is correct, then such compression must be possible.
There are, however, a few problems with this.
First, there is the obvious problem that even if matter can be so compressed, it is unlikely that a human being could survive such compression.
Second, there is the problem of getting the stuff back to that original state-what sort of means would suffice to bring about such compression?
Third, there is the problem that things might be different now. To be specific, when the stuff was all compressed in the pre-bang mass the qualities were perhaps very different. For example, there were no electrons. Once there are electrons they cannot be compressed like the original stuff. To use a rough analogy: imagine a block of clay that is then made into several mugs. The mugs will not be able to fit back into the same space as the original block. This is because a fired mug is quite different from wet clay. Of course, the mugs would fit again if they were ground into powder-but that is not the kind of shrinkage the stories envision. However, it is interesting to think that the universe must be able to fit into a tiny space. If it cannot, then that means that new things have been added to the universe (either ex nihilo or from outside) since its inception.
So, it looks like getting small is not a viable option.