Puzzler: Are we there yet? A hiker's conundrum.

Note: This puzzler was adapted the puzzler on 12/18/2006 from Cartalk.com.

Jack and Sam go on a hike in a national park. They plan to go from point A to point C via point B. At A, they see a sign that says, "8 hours until point C". They start off. At point B, they see a sign saying "3 hours to point A" and "3 hours to point C". How can this be?
Not all paths are equally easy. It is more tiring to walk uphill than downhill. Typically, you walk or ride faster downhill than uphill. This is similar to something that can happen in chemical reactions.

It can be difficult to cross the barrier between A and C, slowing the reaction down. This energy barrier that would need to be overcome is called an activation energy. You can see that the starting and ending states are not necessarily at the same energy (they often aren't). In our research, we investigate these activation energies using differential scanning calorimetry and use x-ray diffraction to better understand the rate at which the reaction occurs. We also may use Raman spectroscopy to verify the models we make to describe this behavior. Kinetics is a discipline that describes how things move from one state to another in time.