Theory of storage:
Several reasons seem to be involved in this view, including one pointing out the fact that the temperature and atmospheric pressure in the pyramid are maintained at a certain level, and the other arguing that it must have been used to store emergency provisions many years ago at the time of food shortage. (My comment: The spaces in the Great Pyramid that have been discovered until now are only a little part to the pyramid as a whole. Thus supposing it used to be used as storage, it would be very inefficient.)

Eternal calendar:
It is a theory advocated by Piazzi Smyth, a Scottish astronomer of 19th Century. It argues that 1-pyramid inch indicates 1 year, and by using that measurement, we can divide a passageway in the pyramid running from the lowest part, which indicates 4,000 BC, to the King's Chamber, which indicates 2001. Then by looking at the condition of the passageway at each point, it is possible to find out what incident has occurred at certain period. (My comment: In 1800s, the year 2001 must have been considered as a far future, but we are now in 2002. That means that we are in the time that can no longer be indicated with the calendar of pyramid.)

Index for land investigation:
This theory was set up with the reason that the pyramid is visible from everywhere. (My comment: If it was built only as an index, I suppose, the complex structure inside the pyramid would be unnecessary.)

Astronomical observatory:
An astronomer, Procter, and later astronomer McNaughton advanced this theory, arguing the Grand Gallery in the Great Pyramid to be an observatory, and the two passageways to be observatories for Sirius. However, there also is a counterargument, which seems to be receiving considerable support, saying that such a huge construction is not necessary if it was only to look at the stars. Sundial:
This theory has been put forward by Cotsworth. It explains that the northern slope of the pyramid would be in complete shade for the first 6 months, and then get some light the rest of the year. Also, twice in the year, the northern slope would be half in the sun and half in the shade. The theory holds those two days to be indicating the vernal and autumnal equinoxes. (My comment: This also does not explain the purpose of the complex interior structure.)

Repository of mathematical and scientific knowledge of the lost civilization:
There is such a theory like this also.

Device to help deceased pharaoh's spirit rising to heaven:
This idea is quite commonly mentioned in the pyramid text. It probably is a result of consideration of the relationship between the pyramid text and the Great Pyramid. (My comment: It seems to me that concrete directions for use of the device have not yet been provided. It is necessary to prove a consistency between the theory and the actual interior of the pyramid.)

Public works:
This theory argues that the Great Pyramid itself has no purpose, and the point was to build something large. (My comment: It sounds like an ancient Egyptian version of the New Deal policy. As it says that the Great Pyramid itself has "no purpose," it is hard to give a comment, but if I were to venture an opinion, I would say that I am working on it aiming to find a purpose.)

Other than those I mentioned above, there seems to be more and more opinions such as energy-storing device, the earth in miniature, irrigation pump, and so on.

To be continued

Translated by Maiko Noda