Dr John B Cosgrave - Mathematician
Career snapshot
Dr John Cosgrave teaches mathematics at St Patrick’s College, Drumcondra, Dublin. He specialises in number theory and has made a series of discoveries, including in the year 2000 a new prime number of 2,000 digits, his millennium prime, and on 10 October 2003 a new record composite Fermat number.
Degrees
- Mathematics degree (1968)
- Doctorate in number theory (1972), Royal Holloway College of London University
Where did you grow up and go to school?
“I am from Bailieboro, Co Cavan, where my father – an outstanding teacher – taught me for my last three years at national school . Besides the standard school work he introduced us to three Shakespeare plays, simultaneous equations, Latin, French and more.”
“I went to three secondary schools: Gormanston in Co Meath (I ran away three times, and eventually my father realised I didn’t like it there); St Mary’s Marist school in Dundalk; then the Salesian school in Oxford.”
When did you decide to make a career in mathematics, and when did you specialise in number theory?
“I never thought of myself as wanting to ‘have a career’. I simply wanted to be able to do mathematics. I always wanted to do number theory from the moment I first encountered it at school in Oxford.”
What is number theory?
“Number theory is just that: it’s about numbers. Like all mathematics it’s about trying to answer certain questions, such as how many prime numbers are there? There are, in fact, an infinite number of them, but how does one know that?”
How did it feel to discover a new record composite Fermat number in October 2003?
“The recent one (which broke a record previously established in February 2003, which in turn broke a record established in July 1999) came as quite a shock; it was so unexpected. Of course I was overjoyed, but the shock element was greater.”
What’s the best thing about your job?
“Being paid for doing what I love.”
How do you spend typical day?
“Putting off to tomorrow what should have been done yesterday.”
Did mathematics give you a buzz at school?
“Most definitely so. When I first heard of ‘geometry’ at secondary school I was totally bored with the whole thing, while at the same time being able to regurgitate stuff in exams. Then, one evening, at the start of my second year at Dundalk – through my own independent reading and thinking – I quite suddenly fell head-over-heels in love with ‘geometry’. There was no turning back; I was hooked.”
What has been the highlight of your career to date?
“Some rather than one. They include:
- Tim and Mair
