Like many universities, the University of Central Florida (UCF) has had many guest speakers this semester. It is quite interesting to hear the thoughts of folks from other universities regarding mathematics and its role. Two of my favorite talks recently have been by Dr. John dePillis and Krishnaswami Alladi.

**Mathematical Conversation Starters: John dePillis – University of California, Riverside**

Dr. dePillis’ talk was aimed at both mathematicians and non-mathematicians. (Even some of my calculus students were in attendance and found it quite enjoyable.) He discussed many different topics including the scientific method, the birthday problem, Monty Hall problem, Sherlock Holmes, algebra of the mind, critical thinking, etc.

I think the talk’s message that most impacted my students is the algebra of the mind. Students many times think of algebra as something that occurs in mathematics and does not relate to how they think during their daily lives. dePillis used the distributive law to show this is not the case. He defined the following events:

- R: I will go to a restaurant
- S: I will order salmon
- T: I will order tuna

Then he said he will go to the restaurant and order salmon or tuna, explaining that it is the same as I will go to a restaurant and order salmon or I will go to a restaurant and order tuna. Everyone in the room could easily understand this thought process. Then he used mathematics and the distributive law. He gave Then he explained that the mathematical equation was representing the exact thought process you were just having. Unfortunately, oftentimes this lesson is lost on students.

I cannot wait to check out dePillis’ books *777 Mathematical Conversation Starters* and *Illustrated Special Relativity Through Its Paradoxes*.

**Paul Erdős – one of the most influential mathematicians of our times: Krishnaswami Alladi – University of Florida**

This talk was sponsored by the UCF Math Club and was given at a level understandable to undergraduate mathematics (or related fields) majors. Dr. Alladi gave some general information about Erdős who, in my opinion, is one of the most interesting mathematicians of all time.

Alladi told of a hyperbole that I had never heard in which Erdős was on a train and by the end of the train ride, he had jointly authored a paper with the railway collector. Although this story, as Alladi pointed out, is likely untrue, it serves to demonstrate Erdős’ willingness to collaborate with multitudes of people.

I particularly enjoyed listening to Alladi’s story of how he met Erdős. Alladi had done some work on a problem and he was not sure of its important or if it was already known. He sent his work to Erdős and quickly got a response asking if they could meet at a conference in India. unfortunately, Alladi was not able to attend, but his father was attending the conference and went in his place. Erdős enjoyed the work so much he replanned his next trip so that he could travel to where Alladi lived to speak with him in person. This began his collaboration with Erdős.

One of my favorite quotes from the talk came from Alladi himself,

If you are comfortable with the convergence and divergence of a sequence, you have developed into a more mature man.

Have you had any really interesting speakers come to your university? What did they speak about and why did you enjoy it?