The Pyramids: Science or Non-Science? In class, I described some of the discussion, most of it very non-scientific, about the origin and purpose of the pyramids. (Were they built by ancient astronauts who arrived on UFO's?) Part of the speculation about the intervention of astronauts, a notion which was popularized in a book called `Chariots of the Gods' by Erich von Daniken, is motivated by our understandable surprise at the fact that such enormous constructions as the Pyramids could have been built by what we assume to have been very primitive people. There are several important points I want to make in this context. 1 Cultural Bias: There is no doubt in anyone's mind that the great cathedrals of Europe were built by people without the help of extraterrestrials, even though some of those date from almost a thousand years ago. These are architecturally very elaborate, with arches, windows, flying buttresses for support, and so on. The pyramids have some impressive structural subtleties, like the inner (burial) chambers hidden behind false doors and the like, but basically they are much simpler than the cathedrals, and there is no real need to invoke superhuman engineering. It has in fact been pointed out that the argument put forward by von Daniken is fundamentally racist. He concedes that Europeans could build the complex cathedrals, but refuses to admit equivalent levels of skill and endeavour in the non-European societies. Discussions which depend on and repeat such racist or unjustifiably Eurocentric thinking are to be mistrusted. 2 The Non-linear Growth of Technology: Part of von Daniken's rationale, however, is that the pyramids were built four thousand years ago, when presumably the Egyptian people were much less technologically able than the cathedral builders of Europe a mere one thousand years ago. This sort of reasoning is not unique to von Daniken, but should be carefully considered in light of the fact that progress is not linear, but rather exponential (i.e. comes at an ever-increasing pace). In the last century, for instance, we have seen people go from horse-and-buggy days to cars, airplanes, and spacecraft; from pencil and paper to a personal computer in every home and supercomputer power available on the network; from written letters to telephones, faxes, and television; from kerosene lamps to electrical services to every home and (probably soon) controlled nuclear fusion reactors providing essentially unlimited power. Given this rate of progress in recent years, it is tempting to think as follows: if we were technologically so poorly off in 1900 (no TV, no cars, no electricity), what must life have been like in 1800? or even worse, in 1700? or 1600? or 1500? or .... This sort of linear extrapolation, assuming that every century marks an equivalent decrease in our abilities and technology, soon leads you to conclude that the ancient Egyptians (and other societies of the time) must have been terribly primitive indeed, scarcely scraping out an existence from the bare soil. It is undeniable, of course, that the medieval cathedral builders had some advantages over the Pyramid builders, mostly the product of centuries of experience. They had better ways of making pulleys and ropes, scaffolds and jacks; and they had better metal tools to work with. But the differences are very much smaller than is generally realized, and the Egyptian accomplishment of (to express it in simplistic terms) piling up a lot of stone blocks into a heap would indeed have been realizable with such technology. (See also my point 4, below.) 3 Failed Pyramids: Another reason to doubt the suggestion that the Egyptians were helped by extra-terrestrials is the fact that there are `failed' pyramids, and indeed we can trace a gradual evolution in the design and construction techniques over the many centuries during which the various pyramids were built. One of the very oldest, for instance, is in two parts: the lower level was started with very steep walls, but the construction started to crack under the weight of the upper levels, partly because it was built on an unstable sandy base. To reduce the load, the upper levels were built with a different, less steep slope (i.e. less rock in total). The next stage in this process came with the building of `step' pyramids, rather like wedding cakes, with discrete layers instead of a continuous slope. Only later was the technology perfected to permit the building of the regular pyramids we all think of. It is hard to understand how the intervention of extraterrestrials would have made this learning process necessary. By the way, it is also true that there are failed cathedrals! Quite a lot of the construction business was learned by simple trial and error, and there are examples of cathedrals which collapsed in whole or part (Ely cathedral, just north of Cambridge, England, had one of its towers collapse, for instance). There are many more which have needed shoring up over many centuries or which contain clear construction mistakes (such as a pair of mismatched arches over the apse of Durham cathedral, in the north of England). 4 A Test Case: These arguments are not compelling, of course. How do we counter von Daniken's more direct statement that the actual cutting, moving, and putting in place of the stones would simply have been beyond the physical abilities of the Egyptians? One can do calculations, but a more persuasive experiment is actually to see if real people, using the simple tools available to the Egyptians of the day, could have carried out the enterprise. That is the subject of a fascinating NOVA program, a video copy of which I own. (I invite any interested student to borrow it from me.) In this program, an American archaeologist, working with Egyptian labourers, was set the challenge of building a scale-model pyramid; and the conclusion was that the enterprise was indeed feasible. To build a full-scale Pyramid would, of course, have required many thousands of labourers and decades of work -- as did the building of the European cathedrals, for that matter -- but technologically there is no impediment to this straightforward interpretation of the origin of the pyramids. 5 Intellectual Grave Robbing: Most of you know already that many of the burial chambers in the Egyptian pyramids were desecrated by looters, often despite elaborate devices meant to keep them out. By analogy, I would suggest that we do a serious disservice, which you might think of as `intellectual grave robbing,' to the ancients if we fail to acknowledge their profound work and the depth of dedication and motivation (probably largely religious, since the Pharaohs were seen as at least partly divine) which moved them to build the pyramids. Do not be too quick to belittle their efforts (which are part of your history as a human being) by saying that they simply couldn't have done it. By the way, it is also worth remembering that pyramids are not unique to Egypt: they occur, in different design but with the same general shape, in Aztec Mexico, Central America, ancient Mesopotamia, and so on. Partly this reflects the fact that "heaping stones up" (to again express this in oversimplistic terms!) is the easiest imaginable way of building a huge monument or temple without getting into the architecturally more complex job of building something like the great medieval cathedrals of Europe with freestanding walls.

Astronomical Alignments in the Pyramids.

Let us turn now to more directly astronomical matters. There are certain astronomical alignments built into the structure of at least some of the pyramids: they are carefully aligned North-South; there are shafts which would admit the light of the star Sirius (which had religious significance to the Egyptians, in part because it was the rising of Sirius which signalled the time of Nile flooding); another shaft would have admitted the light of the Pole Star. The astronomical importance or practicality of doing these things seems to be rather limited. It is possible that it was nothing more than generally symbolic, rather as we usually align Christian churches so the apse is at the East end, although this feature is not used in any astronomical way.

The Pole Star: Precession.

In an earlier lecture, we consider one of the important conservation laws: I pointed out that the spin of an object helps to maintain its orientation in space, and thus we can understand why the Pole Star (or North Star) seems always to be overhead for a person standing on the North Pole. Indeed, if the Earth were completely isolated in space, you would expect it to continue spinning in this way unchangingly forever. It is, however, possible to use a gyroscope (a spinning top-like device mounted on a small support point), to demonstrate that spinning objects affected by external forces do not act quite so simply. If a gyroscope could be set spinning in empty space, it would always point the same direction; but on a table top, it feels the extra downward pull of the Earth's gravity, and for reasons too complex to go into in detail this causes the direction of the spin axis to slowly move around in a phenomenon known as precession. An everyday example is provided a spinning top, which has the extra complication of friction with the floor on which it is spinning. As you may remember, a top wobbles around more and more until it finally falls over; the 'wobbling' is precession. The same is true for the Earth: it does not sit all by itself in empty space, unaffected by external forces. It feels the gravitational tugs of the moon and Jupiter, for instance, in addition to that of the Sun. The net effect of these is to make the Earth's axis slowly precess, just as the gyroscope did. (See pages 39-41 of your text.) That is, it slowly tips in direction in space, and as a consequence, many centuries from now the present Pole Star will not be above the North Pole. The precession of the Earth's axis takes about 26,000 years before the axis comes back to where it started. There will be times when there is no Pole Star. Indeed, this was the case at about the time of the birth of Christ, so if the Egyptians had been building pyramids in those days (rather than two or three thousand years earlier) they probably would not have even constructed the long shafts which admit the light of the Pole Star. At other times in history, another star may by chance be located above the Earth's North Pole, depending on the direction the Earth's axis points (which can be predicted very precisely). In the time of the Egyptians, for instance, the star we call Thuban was almost directly above the North Pole of the Earth, and it is the light of that star which would have shone down the shafts of the pyramids -- not the light of Polaris. Previous chapter:Next chapter

0: Physics 015: The Course Notes, Fall 2004 1: Opening Remarks: Setting the Scene. 2: The Science of Astronomy: 3: The Importance of Scale: A First Conservation Law. 4: The Dominance of Gravity. 5: Looking Up: 6: The Seasons: 7: The Spin of the Earth: Another Conservation Law. 8: The Earth: Shape, Size, and State of Rotation. 9: The Moon: Shape, Size, Nature. 10: The Relative Distances and Sizes of the Sun and Moon: 11: Further Considerations: Planets and Stars. 12: The Moving Earth: 13: Stellar Parallax: The Astronomical Chicken 14: Greek Cosmology: 15: Stonehenge: 16: The Pyramids: 17: Copernicus Suggests a Heliocentric Cosmology: 18: Tycho Brahe, the Master Observer: 19: Kepler the Mystic. 20: Galileo Provides the Proof: 21: Light: Introductory Remarks. 22: Light as a Wave: 23: Light as Particles. 24: Full Spectrum of Light: 25: Interpreting the Emitted Light: 26: Kirchhoff's Laws and Stellar Spectra. 27: Understanding Kirchhoff's Laws. 28: The Doppler Effect: 29: Astronomical Telescopes: 30: The Great Observatories: 31: Making the Most of Optical Astronomy: 32: Adaptive Optics: Beating the Sky. 33: Radio Astronomy: 34: Observing at Other Wavelengths: 35: Isaac Newton's Physics: 36: Newtonian Gravity Explains It All: 37: Weight: 38: The Success of Newtonian Gravity: 39: The Ultimate Failure of Newtonian Gravity: 40: Tsunamis and Tides: 41: The Organization of the Solar System: 42: Solar System Formation: 43: The Age of the Solar System: 44: Planetary Structure: The Earth. 45: Solar System Leftovers: 46: The Vulnerability of the Earth: 47: Venus: 48: Mars: 49: The Search for Martian Life: 50: Physics 015 - Parallel Readings.

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Mystery destination!

(Friday, 28 January, 2022.)