In the visible world, the Milky Way is a tiny fragment; within this fragment, the solar system is an infinitesimal speck, and of this speck our planet is a microscopic dot. On this dot, tiny lumps of impure carbon and water, of complicated structure, with somewhat unusual physical and chemical properties, crawl about for a few years, until they are dissolved again into the elements of which they are compounded. They divide their time between labour designed to postpone the moment of dissolution for themselves and frantic struggles to hasten it for others of their kind. (Russell, “Dreams and Facts”, reprinted in his Sceptical Essays)
Compared with Russell’s description of how small we are, which seems accurate, the usual metaphor that human beings are tiny specks in a vast universe seems an exaggeration of our size. If even the solar system is only a tiny speck, how should we describe our smallness? However, what we should ask in this connection is rather the question “What does the size of us have to do with the meaningfulness of our lives?”. It does not seem that meaningfulness depends on the relative size of our existence. If I think my life is meaningful, I would not think that it was less meaningful simply because I had come to believe that the universe had become several hundred million times bigger (while my size did not change). As Frank Ramsey so pithily puts it, “[t]he stars may be large, but they cannot think or love” (see “Epilogue” of his Philosophical Papers). Whether our lives are meaningful or not depends on what we do and think and feel, rather than on how big or small we are.
But then why do some people think the relative size of our existence matters to the meaningfulness of our lives, or more specifically, why do some people think our smallness implies that our lives as such are meaningless? I think the most reasonable answer is that when people think in this way, they see their smallness as a kind of limit of their lives. Death can be understood along the same lines ¾ death is a temporal limit of life. Our smallness is, by contrast, not just a spatial limit, but also a limit to our abilities: being so utterly small relative to the universe, we are confined to the extremely tiny space we are in and not able to achieve much even within that tiny space. There is no better expression of this understanding of how limits of a life and meaningfulness are related than the following passage by Robert Nozick:
Consider the most exalted and far-researching life or role imagined for man: being the messiah. Greater effect has been imagined for no other man. Yet still we can ask how important it is to bring whatever it is the messiah brings to the living beings of the third planet of a minor off-center star in the Milky Way galaxy, itself a galaxy of no special distinction within its particular metagalaxy, one of many in the universe. Te see something’s limits, to see it as that limited particular thing or enterprise, is to question its meaning. (Nozick, Philosophical Explanations, p.597)
On this understanding,“[t]he problem of meaning is created by limits, by being just this, by being merely this”, and “[a]ttempts to find meaning in life seek to transcend the limits of an individual life. The narrower the limits of a life, the less meaningful it is” (pp.594-595). Hence the quest for grand meaningfulness.