Edits do bump posts, and all questions are on equal footing.
Any time a question is asked, an answer is posted, or either a question or an answer is edited, the question is bumped to the top of the active tab, which is also probably what you see when you just go to the main site. A question will only appear once in that list, based on the most recent modification.
Note that we get about 66 new questions per day, the eighth highest across the network. Posts don't linger on any list of "most recently modified" because too many questions, answers, and edits are occurring. Imagine the chaos if every person who asked a question were in competition to keep their question at the top of such a list. Consider also that the reason edits bump posts at all is so more people can vet them and make sure there is no vandalism or quality degradation going on behind our backs, and we don't want to be flooded with unnecessary edits.
Thus there is a crowding-out effect -- you cannot keep your question more visible without reducing some other question's visibility.
Please do not edit just to bump posts.
Again, there is a fixed amount of attention the users of the site have, and making them notice your question necessarily detracts from other questions' views. There used to be a built-in safeguard: After a certain number of edits, the system automatically made your post community-wiki, meaning you no longer earned rep on it from upvotes. That feature has been done away with, though, for entirely unrelated reasons, so we are left to trust that users won't abuse the side effect of bumping that comes with editing.
Of course, making the question better is not a problem. If an edit substantially improves things (and remember, more is not always better), feel free to make it. But if you just want attention...
That's what bounties are for.
Yes they can be expensive when you are a new user, but that is intentional design. Bounties let you get that attention, but they make sure you really are dedicated to getting an answer, since it will necessarily detract from the attention others get.
A bounty keeps the question on the featured tab of the questions page for a week, where a number of users check to find particularly worthwhile questions to invest their time answering.
There are other channels that help unanswered questions get answered.
In addition to the featured tab and the active tab (which is the same content as the main page), the questions page also has a newest tab, which simply displays all questions ordered only by when they were asked. Your question will be visible here for a longer time, as answers and edits do not count. There is also the newest tab of the unanswered questions page. A number of users, myself included, will check this list when looking for stuff to answer.
Answerers are people too, with their own motives.
It's useful to remember that we all have our own interests, and thus have topics we're not as interested in helping students with (or don't know enough to do so). Add to that the fact that professional physicists may not want to spend all their free time answering low-level questions they've seen hundreds of times before, and you see that not everyone is in a position to serve you.
Also, most people have a particular weekly schedule in real life. Perhaps you post a question at the beginning of the weekend, while the users most eager to answer your style of question only visit on weekdays.
Give the question some time. Unlike Stack Overflow, we are not about rapid-fire replies that fix the problem you're being paid to fix with the minimal amount of information needed to get the job done. Answers here are often very well thought-out and considered, and they tend to trickle in over several days at least. In fact, if someone accepts an answer I give too soon, I usually tell them they shouldn't be so quick to consider the issue settled, since even better answers may very well be provided in due time.
