How many stars do you think there are in the universe? If you are anything like me, who has a rather casual knowledge of science, you’ll feel completely unqualified to even hazard a guess. If you were to try, you could be forgiven for getting it wrong because the answer keeps changing. Once upon a time, it was thought there was only one star (in the sense in which we understand it), and the things we saw were holes through which we could glimpse this light of heaven. Not so long ago it was thought there were infinite stars in an infinite universe (we now know that our universe is not infinite) and it seems that the answer was, until recently, 100 sextillion stars (it looks more impressive with the numbers actually written down: 100,000,000,000,000,000,000,000). This answer is rather out of date with the publication of a report in the journal Nature by Dr Pieter van Dokkum from the University of Yale (http://blogs.discovermagazine.com/80beats/2010/12/01/the-estimated-number-of-stars-in-the-universe-just-tripled/). It has been reported by van Dokkum that the number of stars in the universe is three times what we previously thought. The study’s main focus was the class of star known as red dwarf stars, and up until now astronomers were only able to detect the red dwarf class of stars in our own galaxy and had to assume that in galaxies other than our own the ratio of stars like our own to red dwarf stars was 1:100 as it is in the Milky Way. Because of new methods of observation astronomers can now tell us that stars like our own are even more outnumbered by red dwarves in other galaxies. Something like 1:1000. The previous hypothesis was a rational estimation, the new hypothesis is an empirical. If it’s not fact, it is at least a much clearer estimation.
This information is intrinsically fascinating, if perhaps a bit remote from human experience, and has a myriad of implications which would take much more space to go into (what does this tell us about the likelihood of intelligent life throughout the universe? Is there a possibility of there being even more still stars in the universe? etc), but more narrowly it tells us something interesting about scientific method.
If we put aside the ontological question of what else might exist that we don’t know about, what I find interesting about this is the disparity between the rational method and the empirical method of scientific discovery. There is a famous dispute in philosophy between these two schools of thought and both have there clearly determined uses. I would argue that the rational method gives us insight into what we cannot yet discover by empirical study, but when empirical observations become available and it contradicts what rationality has previous told us, it is time to adapt our beliefs. There is the old phrase ‘begging only gets you so far’, well I think you could also apply it to rational thought; ‘rationality only gets you so far’, and in this case it’s within a factor of three of the truth.