No Way Physics: Thought provoking

Many principles of physics are of the form "If you do this, what will happen is that." Newton's second law, for example, says that the acceleration of a particular mass will be proportional to the force applied to it. Such principles imply that certain effects are practically impossible. A small number of principles, however, belong to a different category. These say, in effect, "That cannot happen." Such principles imply that certain effects are physically impossible.

Notorious examples of the latter include the first two laws of thermodynamics. The first law says that energy cannot be created or destroyed ("You can't win"), while the second can be stated in several forms, such as that heat cannot be transferred from a colder to a warmer body or that the entropy of a closed system always increases ("You can't break even, either"). Other examples include Heisenberg's uncertainty principle and the relativity principles regarding the impossibility of recognizing absolute velocity and the prohibition of faster-than-light travel.

Such principles often represent not "new physics" but deductions from other principles. What is different about them is their form. And to say that something is physically impossible tends to make scientists want to rebel.

The article goes on to explain that such laws force scientists to re-think their theories, to try to find ways to make something work that is actually impossible. Such provocations lead us to new theories and new technologies.

While some things are truly impossible, sometimes being told something is impossible is the first step to getting it done.