PhD vs. Master's program : not having the same research topic

[Adelaide9216]

Hello! What are the pros and/or cons to choosing a different topic for a PhD program than your master's research topic? (that includes having different supervisors for the PhD versus the master's)? 

[rising_star]

In brief:

Pros: getting to explore a new area of interest, gaining experience working with multiple PIs (you'll need 3-5 rec letter writers for academic job applications typically), possibility of engaging in more interdisciplinary work.

Cons: new literature to familiarize yourself with, changing supervisors may not go smoothly, overall time to degree could be longer.

[TakeruK]

I would summarize it the same way as @rising_star did. I changed supervisors, (sub)fields/topics**, departments and schools between my MSc in Canada and my PhD in the US. Very happy to have done so---I don't regret it at all! The only con that was really a con is the longer time---changing from the Canadian system to the US system meant I was in grad school for 7 years in total, but this isn't really that bad. Most people in my field took 5 or 6 years, so an extra year or two in exchange for the amazing experience I got at my new PhD program was completely worth it, to me. 

(** This is all relative of course, to an academic in astronomy/planetary science, yes, I definitely changed topics and also methodology, but to someone outside of my field, I went from studying one aspect of one type of planet to another aspect of a different type of planet.)