I am a senior Physics/Math major. I want to go to grad school (99% sure) but I am not ready to start immediately after undergrad, I hope to bike to and live in South America next year. My question is, how harmful will this be to my chances at getting into a top tier physics Pd.D. program the following year? And would it be a better idea to apply now to grad schools and ask for a deferral if I am accepted, or just wait until next year to apply? Thanks.