The physics that is used in forensics is described briefly in this article from the March issue of Physics Today. It is unfortunately that a clear example on where it is useful is in a tragic incident.
A young woman was found at the bottom of a cliff in Sydney, Australia, in June 1995. The site was a popular suicide spot, and the police assumed she had killed herself. But last November the woman's boyfriend was convicted of murder. “It took 10 years to figure out that the woman was thrown off the cliff; she did not jump,” says Rod Cross, a physicist at the University of Sydney who served as a consultant for the case. It took that long, he adds, “mainly because the police did not understand that physics could help solve the problem.”
The second example comes from the same issue of Physics Today, and in fact, is the very next article. It deals with the issue of making proton accelerators more compact (and thus, affordable) in the treatment of cancer. I decided to highlight this for two reasons:
1. It shows another application of accelerator physics which does not involved a high energy physics experiment, and
2. It shows that physicists and physics CAN, in fact, be used to "cure" cancer.
I'm mentioning this because of a blog entry that I made that was completely unrelated to this. I mentioned an amusing poster produced by the APS on how long one has to yell at a cup of coffee to heat it up. For some odd reason, it was picked up by fark.com, and the comment on the story was:
Scientists solve the biggest puzzle of our age: How long would you have to yell at a cup of coffee to heat it up? And why is there still no cure for cancer?
I also received a rather nasty and profanity-laced "comment" to the blog, which basically asked why us "MF's" are wasting out time and not using our brains to cure cancer (the comment was not approved and it is now gone into laa-laa land).
I'm sure the first was written in jest, but both of these comments reflects an ignorance of the usefulness of the back-of-the-envelope calculation shown in that "coffee" article, and how physicists often determine something at the very beginning before plunging into something. It is an example or illustration on how we translate physical concepts and ballpark figures to determine some "boundary conditions" to how something can occur. It has nothing to do with the coffee, it has EVERYTHING to do with the skill involved. This still transcends that stupid coffee and can be used in almost any kind of situation. I could easily come up with several different example: (i) if we need to build a solar collector to produce 20 MW of energy over the duration of x hours, how big does it have to be?; (ii) if we have a cancer cell that needs to be irradiated by a proton beam over an area that is this big, how energetic should the protons be? etc... etc...
These are the type of quick calculation that one start with to lay down the foundation of possibility or realistic scenario for the detailed calculation later on that takes into account more factors involved. But that initial calculation is crucial to narrow down or at least provide some idea on where in phase space the problem is, and what kind of daunting scenario we are faced with.
And yes, that SAME skill is involved in providing the physics to those in the medical profession the TOOLS needed to fight cancer, both in terms of treatment, diagnostic (where do you think MRI, CAT scans, PET scans, etc. came from?), and advanced analysis. These professionals are the ones you need to hark at to find the cure for cancer. Yelling at physicists to do that is similar to asking medical doctors to find the origin of high-Tc superconductors. They may help in maintaining the well-being of the people who are finding the answers to high-Tc superconductors, but they are not really experts in the field and not directly working in it.