Opinions remain divided over the cause of the sinking of the Cheonan. One theory is that the vessel ran aground early on. This idea was put forward by Shin Sang-chul and Lee Jong-in, who lack doctoral degrees but are rich in first-hand experience, and an identical conclusion was reached by a team of Russian experts. Another theory is that a North Korean torpedo was responsible, the conclusion reached by the South Korean government-sponsored Joint civilian- military Investigation Group (JIG) with more than 20 PhDs among its members. The types of evidence presented by the two groups also differ entirely in character.

The former group has presented evidence that any sensible person could understand, including the clean condition of the surviving and deceased sailors, the lack of a water column, the damaged state of the ship's screws' wing blades, and he fishing net wrapped around the propeller¡¯s axis. On the other hand, the latter group has presented a piece of torpedo propeller.

That piece of metal is a ghost without substance, presented by the JIG in order to conceal the truth. Regarding the degree of corrosion of the metal surface, Lee Jong-in conducted his own experiment with small metal pieces under water, and

argued that the JIG's claim that the chunk of the metal had been underwater for just 50 days was false. This is consistent with the results of visual examination done by Russian experts. The old pieces of metal that anyone with common sense

would conclude had been underwater for years was presented by the JIG as ¡°conclusive¡± evidence proving that a North Korean torpedo sank the Cheonan.

There are two logical steps in the JIG's claim. First, the torpedo fragment has to be North Korean-made, and second, the torpedo must have exploded right next to the Cheonan. The ¡°No. 1¡± blue ink mark written in Korean on the fragment was

presented to confirm the first step, and the "adsorbed materials" data for the second. If any one of the two were wrong, the JIG's claim would be invalid.

First, if one thinks sensibly, the ¡°No. 1¡± mark could be written by South Koreans as well, and thus it would not be taken as evidence by a court of a democratic society. Even the JIG have denied its evidentiary validity; their own chemical

analysis concluded that the ingredient of the blue ink was ¡°Solvent Blue 5¡± that had patented by a South Korean company, Monami, and they said that it cannot be traced to North Korea.

Recently, Song Tae-ho, a mechanical engineering professor of the Korea Advanced Institute of Science and Technology (KAIST), claimed that the ink letter might not be burned by explosion. According to his calculations, during the explosion the temperature of the back of the disk where the ¡°No. 1¡± was written would not increase by more than 0.1 degree. His conclusion is wrong, but even if his conclusion were true, it is still impossible to explain how aluminum, an ingredient of an explosive, became stuck to the surface of the torpedo propeller that was farther away form the warhead part that contains the explosive than the disk. According to Dr. Song¡¯s claims, it would take only about 0.15 seconds for the high pressure gas bubble formed by the explosion to expand to the propeller part, and by the time the temperature of the bubble gas would become below zero degree Celsius. At such a freezing temperature, aluminum oxide would have

solidified and could not adhere to the propeller.

In other words, Song¡¯s claims contradict the JIG's claim that the "adsorbed materials" are aluminum oxide stuck to the propeller as a result of the explosion. Moreover, the JIG claimed that the paint on the exterior of the torpedo burned

away completely due to the heat, and Dr. Song¡¯s conclusion predicts the exactly opposite.

So what could have led Song to obtain his conclusion that, contrary to a sensible belief, temperature would not rise nearby an explosion? It is because he used an equation PV¥ã=C that works for a reversible process in which expansion occurs relatively slowly with the pressures inside and outside the bubble being kept equal at all time. Any explosion is, however, an irreversible process. A third-year physics major in a college would know that the initial expansion of the high

pressure bubble gas is similar to an irreversible process in which gas expands into a vacuum. This is because the pressure inside the bubble created by an explosion of a 250kg explosive is well over 100 thousand times greater than the pressure outside. In this process, for an ideal gas, temperature remains the same before and after the expansion. Since the process is irreversible, a precise calculation is nearly impossible, but an approximation would show that the temperature when the bubble reaches the propeller part would be extremely high, at least 1,000 degrees Celsius.

The second piece of ¡°scientific¡± evidence presented by the JIG were the EDS/XRD data, and it requires at least a master¡¯s degree in a specialized field to understand the data, which is beyond the knowledge of the general public. This

seemed to have given the JIG some tremendous authority and power for a while. The florid and difficult explanations, touted as a ¡°world¡¯s first discovery,¡± made by people carrying dazzling doctoral degrees seemed to be convincing and to make most people dumbfounded. However, a quick examination by Dr. Panseok Yang, a specialist in EDS, and myself, a specialist in XRD, revealed that the JIG's data did not make sense, and that some of the data must have been fabricated. The JIG's explanations on the issues that Dr. Yang and I raised have been all false. Since the JIG is supposed to release their final report on August 6, Friday, we will release our summary report afterwards.

Looking back on how the Cheonan incident has unfolded up till now, one can see that the activities of two groups of people with PhDs have been mostly related to the ghost. Most of the PhD members of the JIG and Dr. Song have worked hard to create the ghost and to keep it alive. On the other hand, many of the scientists who posted their thoughts on scientific community websites, along with Dr. Yang and myself, have been trying to bust the ghost and to clear up the confusion. Now is the time to move onto the next stage: uncovering the truth about the sinking that was hiding behind the ghost. In fact, it has already begun. The starting point, in my opinion, was when the JIG gave a briefing to South Korean

media groups on June 29. The JIG was explaining, citing the Newton¡¯s ¡°law of inertia¡±, the damaged state of the screw wing blades, a journalist Roh Jong- myeon who has a non-science bachelor degree asked the sharp question, ¡°If the

damage was due to the force of inertia, shouldn¡¯t the direction of the force be the exact opposite?¡± This question marks the start of the next state to find the real truth about the cause of the Cheonan¡¯s sinking. We found out later that the

Russian investigation team had reached exactly the same conclusion. Recently, a Chungnam National University Professor Nho, In-sik, who was a JIG member and who was in charge of investigating the damaged screw wings , attested that his own simulation results differed from the JIG's claims.

The fancy Doctoral degrees are not necessary in finding the truth about the Cheonan. The collective reasoning of people with common sense is enough. The only role of the PhDs is to clear away the ghosts that may pop up during the

process. There is one more role for the PhDs; to find out who created the ghosts and how. This can be achieved simply by redoing the JIG's test explosion experiment. It will probably take a few years to see it happen, considering the current political situation.

	» Seunghun Lee.

During the course of the Cheonan issue, South Korean society has been showing an outstanding collective reasoning. Why, then, have we so far been unable to unveil the truth about the sinking? The reason is that the South Korean government is hiding the relevant information. A formal congressional inquiry is needed, but the current congress is neglecting its proper duties. Even with the limited information, however, cracks are showing in their version of the events.

One of these is the damaged state of the ship's propeller wings. I wish the best of luck to the South Korean people and believe that their common sense will prevail in this difficult endeavor. Collective reasoning can reveal the truth

about the Cheonan.

The views presented in this column are the writer¡¯s own, and do not necessarily reflect those of The Hankyoreh.