leroyjenkens said:
How much does it decline? How fast does it decline? At what point during the decline is constructive to tell someone to abandon their hopes and dreams because they'll never come true?
To the last, I'd say that sometimes it can be good advice. If I had a 45yr old student getting their BS, I would let them know that if their dream is to get a faculty position in theoretical physics then they're probably wasting their time. Its honest truth, but that doesn't mean you can't pursue Physics or make contributions to the field, but your career will end after grad school 99.9% if the time at that age. Sure, its POSSIBLE, but improbable.
Its unfortunate to be in a situation where someone puts their hopes and dreams into something that's nearly impossible, but there's an age we reach where we have to take responsibility not only for our current actions but to our depth of planning in our lives. I wouldn't tell a 10yr old he can't be an astronaut, but a 65yr old with no degree wanting to go back to school to try to be one is irresponsible. (Sure, its their RIGHT to pursue it, but sometimes they just don't have the knowledge to know what is and isn't likely and they look to those in the field for advice).
TO THE OP:
25 is barely old for college. Even if you're a freshman in college your fellow students will be 17-19, so you're not that much older. And to be honest that 5 year age gap might be enough to actually GIVE you an edge in terms of planning and focusing. Your thought process is most likely more mature, and you can take more responsibility for your grades and exams.
I'd also lump medical and biophysics in with materials inasmuch as they are all highly sought after at the moment (a lot of careers open) which is good. Unfortunately, you don't know what it will be like when you finish your PhD, maybe like me there will be another recession with budgets cut everywhere and way too many graduates, who knows.
Stick with it though. 25 is nothing and these fields not only make you an expert in some very narrow field, you also learn mathematics, computational tools, statistics and general creative problem-solving capabilities so far beyond the general population that you'll be in a good situation no matter what.
Heres a few free tips too:
1. Grades will always matter. This is because sometimes there will be people who do not judge you based on your knowledge, ability, history or talents but on some number given to you 4 years prior as they have a stack of 3000 applications just like yours and its easy to do a "sort by GPA".
2. GRE and Physics GRE will matter. Seriously. See #1. There may be a firewall just to get looked at. (usually 3.4-3.6 GPA, not always)
3. Relationships are everything. Your professors can get you internships, REU's, grants, fellowships, papers, contacts, seminars, jobs etc. But you have to properly and professionally maintain these relationships. Your name must have attached to it some level of respect of your superiors. This means maintaining an independent, go-getter attitude whenever dealing with them.
4. Always move up. Your graduate school should be more well known than your undergrad, post doc better than graduate, etc. Not just the name of the school, but also independently the names of the people you will work with. Additionally, apply for everything. Take the time to write custom cover letters for even up to 100 schools for graduate school, as well as cater your research statements to their programs. Don't be lazy.
5. Plan ahead. Start looking at graduate schools in your 2nd-3rd year to get an idea of where the field is at the moment, and what interests you. Go to all the big schools sites and look through their research. Stay organized.
I guess that's is, I don't want to ramble but I like to give advice or at least some experience.