Case Study:  HOW COSMOLOGY BECAME A SCIENCE 

The Book of the Cosmos. Imagining the Universe from Heraclitus to Hawking. 

Ch. 7. He Supposes the Earth to Revolve, Aristarchus and Archimedes. “A great ancient mathematician tells of the strange theory of Aristarchus, according to which the sun, not the earth, stands at the center of the universe.”

First passage:

• Many ancient people believed the earth was round, not flat, and that the sun was at the center of the universe, not the earth. Nevertheless, the common myth is that these things were only discovered around the seventeenth century. Why?
•  Why would anybody want to think about the question, how many grains of sand the universe might hold? Is there any practical reason to pursue this question? Is there a correct answer? A verifiably correct answer?
•  How can the definition of the term universe be an issue? Isn’t it obvious what this means?
•  How might Aristarchus’ hypotheses lead to the conclusion, that the universe is larger than previously thought? Is the assumed motion of the earth relevant?

Second passage:

•  The Aristarchan theory entailed a huge increase in the size of the universe. How big is the universe? Can we ever know for sure?
• Why is it important to have numbers that are so big, that they describe the number of grains of sand it would take to fill the universe?

The article as a whole:

• Archimedes was led to develop new mathematical tools by his “scientific” considerations about the nature of the universe as a whole (i.e. cosmology). Why does this happen in a scientific inquiry, but not in other types of investigations of the same phenomena?
• Are there other instances when this occurred, or is this an isolated event?
•  Of what use are such huge numbers?
•  The two hypotheses, namely that the earth either does or does not move, were equally plausible, given the information available to the ancients. Could they nevertheless, somehow have known which one was right?
•  If one cannot choose between two contrary hypotheses based on observation, can there be other criteria for making a choice? Is it possible, that one of these assumptions was more scientifically fruitful? Should one or must one make a choice at all?
•  The number 10⁶³ is very large, but how large is it? For example, how big would a container have to be, to hold this many air molecules under ordinary conditions? How big would the universe have to be, to hold this many galaxies? How small would angels have to be, for a pinhead to hold this many? If a PC running at 1GHz (i.e. 10⁹ binary calculations per second) needed to make this many binary calculations, how long would it take to finish?