What is Critical about Mass: having enough to sustain a process

    There is a phrase used from time to time -- "critical mass". This phrase was initially used in regards to the manufacture of nuclear weapons. In order for a nuclear device to be able to start a fission (splitting atoms) reaction, there must be enough material that each splitting of an atom creates enough energy to allow for the splitting of additional (at least one more) atoms. So, the critical mass is enough radioactive material to allow for the process to continue once it is started.

   This concept is central to the creation of weapons because a bomb is created such that two, or more, amounts that are less than critical mass are kept close together -- when it is desired to detonate, the smaller amounts are pushed together to create the critical mass and the reaction can take place. A bomb is "clean" if it has the opportunity to split most of its radioactive material before spreading apart and "dirty" if it ends up spreading the radioactive material (not fissioned) into the surrounding area.

   This concept is also important with the design of nuclear power plants -- rather what NOT to do when designing a plant. A properly designed plant will maintain control of how much radioactive material is allowed to be near each other (with the addition of materials called "damping" rods which absorb excess energy). This is important not only for safety but also for the economic operation of the plant. If a plant is not designed this way then it is just a one-time-use bomb. Thus, nuclear power plants (though there may be other dangers) are almost impossible to cause nuclear explosions.

   One more term that is very important to this topic is the "tipping point". This is the very small range that exists between NOT having a critical mass and the amount reaching a critical mass. Just a bit more and it becomes critical. Remove just a bit and it becomes inoperative. Before the tipping point is reached, the process requires continued external energy to maintain progress towards the critical mass.

   All that is just a preamble to this blog [smile]. The concept of critical mass enters into many areas of our society -- political, economic, sociological, and so forth.

   One area of present interest and, which is entering the region of the tipping point, is that of electric cars. Electric cars have been around for quite a while (according to the Net, 1834). However, we do not see electric cars everywhere -- it is mostly internal combustion (gas or diesel) engine cars. Cars, by definition, are used for movement. This means that the source of their energy must be carried along with them. In the case of gasoline engine cars, this means tanks of gas. In the case of electric cars (actually, electric engine powered cars), this means batteries (or an awfully long electrical cord [smile]).

   Batteries have traditionally not been very powerful or very efficient. This continues to change and, although not specifically a critical mass, they are now reaching the point of efficiency to be able to be used more practically. (Note that the same idea is involved with the efficiency of solar cells for solar power.)

   Even with more efficient batteries, they still must be charged on a regular basis and the means to charge them must be close enough together (driving range) such that an electric car can go from one charging station to another. Additionally, the time needed to charge the battery must be relatively short or timed such that the charging can reliably be done at "non-use" times (such as night).

   So, the technology needed to have practical electrical cars on the roads requires three things: sufficiently efficient batteries to provide workable range, charging stations within that range, and technology sufficient to compete with other alternatives. This is now beginning to happen. We are close to the tipping point. The external energy causing us to reach this point has come from the dedication of various people who want the end result. Note that the same process happened to make the internal combustion car practical in the early 1900s.

   Another area of critical mass is concerned with political, or social, matters. Let us take the matter of the ability to vote, within the United States, for women. Within the democratic process, one group cannot grant themselves additional authority, privileges, or rights. They must be granted such by the people who already have that power. This means a process of change of thoughts and attitudes. The energy to achieve that came from dedicated people who worked towards that goal. They achieved critical mass when enough of the existing authorized voters were convinced that women should be granted the right to vote.

   There are many areas where the ideas of a tipping point, and critical mass, are important. They are both involved in areas of change. The change may be a chemical, or physical, process. The change may be a social process. The change may be a political process. But they each have stages and move from one to another by approaching the tipping point, reaching critical mass, and effecting the change.

    What areas of critical mass do you see approaching and which ones do you see from the past?