Astronomy of the Pyramids
Actor’s Version 3/10/2005
Welcome the audience by asking if they have seen the Egypt exhibit, and what comes to mind when they think of ancient Egypt.Why are we talking about Ancient Egypt in Space Odyssey? Because the Egyptians built their pyramids in alignment with the apparent movement of the stars. / Title slide - Pyramids at sunset
You’ve certainly seen pictures of the pyramids, possibly these, the famous pyramids at Giza, and seen what magnificent structures they are. You may even have heard that the Pharaohs were buried there. / Giza pyramids
But what you may not know is that, even though the walls of the pyramids are 100’s of feet long, they are accurately aligned to the cardinal directions of North, South, East, and West within a few tenths of a degree. We believe the Egyptians used the path of the stars in the sky to achieve this, but the question is: why? To answer that question, we need to look to Ancient Egyptian mythology. / Pyramid cutaway with compass
To the Egyptians, the afterlife was as important as life on Earth. Two gods, Ra and Osiris were essential guides in the passage to that afterlife. This is Ra (point to Ra). He represents regeneration, rebirth, and eternal life. This is Osiris, god of the afterlife (point to Osiris). Let’s look at how each of these gods appeared to the Egyptian people. / Photos of statues of Ra and of Osiris
Now Ra was so important, and part of so many daily rituals, that he shows up everywhere in different forms. Here is… point out the different images. Does anyone see a symbol that is repeated in each of these versions of Ra? ….take answers from audience. Yes, a disk. What do you think that represented? /
Three different depictions of Ra
… the Sun. And so the ancient Egyptians witnessed Ra born each morning at dawn on this side of the sky (point to eastern sky), cross the sky, and at sunset, die and pass into the underworld on this side of the sky (point to western sky).(when movie stops, continue:) Enter Osiris, god of the afterlife…
You may recognize this constellation as the Greco-Roman constellation of Orion. To the Egyptians, this is Osiris. Let me tell you the story of how Osiris came to be god of the afterlife. /
SNP Movie of Ra (Sun disk and horns) seen against the Sun as it rises in the morning, crosses sky, and sets
According to Egyptian mythology, Osiris was a pharaoh. He was married to his sister, Isis (yes, they did that in ancient Egypt!) Their brother, Seth, was so jealous of Osiris’ high position as Pharaoh that he chopped him up into pieces and spread them all over Egypt. When Isis found out, she was grief-stricken. She proceeded to collect all the pieces from every corner of Egypt. She wrapped the pieces in linen, and Osiris became whole again. This made Osiris the first intentional mummy, and the first pharaoh to cheat death and become immortal. And so, Osiris became god of the afterlife. / Single depiction of each of the three following characters: Osiris, Isis, SethThe Egyptians observed that Osiris traveled a path similar to Ra’s, only his journey was observable as he crossed the night sky. Of course today, we look at the movement of the Sun and stars and call it East to West. But to the Egyptians, this was the sacred path of Ra and Osiris. / SNP Movie of Osiris in boat seen against stars as it rises in the evening, crosses sky, and sets
The Ancient Egyptians believed that in order to gain entry into the afterlife, they would need gateways that were in near-perfect alignment with that sacred path. Those gateways are the pyramids that we still see today.
But how did they align the pyramids so precisely with this path? How did they take a path that was in the sky and mark it on the earth with such accuracy? Here are some ideas, based on evidence we've found in studying the pyramids. / SNP Movie of day-night cycle as seen from ground
We need to start by creating an artificial horizon, since the actual horizon is uneven. We’re going to build a circular brick wall, completely level on top, to be our horizon.
(Put the two wall sections in place, and forward to next slide) / SNP image of uneven horizon
We’ll also need this stick, which the Egyptians called a merkhet, and we’ll need these two stones. / Exact same view as above, but now with wall in front
Our last tool will be a star. We’ll use Sirius because it will be easy to find in the night sky, since Osiris is quite nearby (point out Osiris).
So, how can we use these simple things – a wall, a stick, some rocks, and a star – to accurately align the pyramids with East-West? We’re going to do something similar to surveying.
I’m going to need a volunteer to help me. Pick a ”volunteer” from the audience, not too young. Explain how you will use the merkhet to site the rising point of Sirius, and that s/he will help you to mark that place on the wall.
We’re going to move forward now through time, and stop when Sirius is just rising over our wall. / SNP image: Orion/Osiris image and Sirius mid way up in night sky, and marked.
Follow Sirius, and use the constellation Osiris if it helps. Point to Sirius as it starts to cross the sky. Notice that Osiris “leads” Sirius, and you’ll see it first, just before Sirius rises. When movie stops, use the merkhet to find the place on the wall that marks the setting point of Sirius, explaining aloud what you are doing. Have the “volunteer” mark that place with a stone. / SNP movie: start from above scene, and stop when Sirius is just rising above the wall.
Now let’s have time move forward again to when Sirius is about to set. Again, use the merkhet to find the place on the wall that marks the setting point of Sirius, explaining aloud what you are doing. Have the volunteer mark that place with a stone.
Give the volunteer the end with the double knot, and ask him/her to hold it at the rock that marks the setting point. Gather the rest of the rope and pull it to the other rock to connect the points. Now, if we use a rope to join these two points we will have an East-West line that is as accurate as could be found using modern methods such as GPS. And if we build our pyramid along this line, it will precisely mirror Ra’s and Osiris’s path across the sky. The volunteer should remain at that rock, holding the knot.
So now we have the alignment for our two East-West walls. But as we know, the base of a pyramid is a square. So we still need to find the North-South alignment for the remaining two walls. For this, we need to turn to geometry… / SNP movie: start from above scene, and stop when Sirius is just setting above the wall.
The Egyptians knew that if they created a triangle with very specific ratios of sides (point to these on the diagram), 3 units for the short length, 4 units for the longer length, and 5 units for the diagonal, they would have a perfect right angle.
I’m going to need another volunteer to help me with this next part. Pick another “volunteer” from the audience. Give the volunteer the red knot and ask him/her to hold it at the rock that marks the rising point. Take the final knot and stretch it toward the audience to complete the triangle. Explain how the one side of the triangle now shows the North-South line. Aswe know, an East-West line intersects with a North/South line at 90 degrees. And so, we’ve just found our North/South line! (indicate NS line) Finally, we have the precise alignments needed to orient our pyramid. Thank the volunteers and send them back to the audience. / Diagram of 3-4-5 triangle
The pyramids were built some 5000 years ago in the earlier time of Ancient Egypt. As time progressed, the center of Egyptian life moved southward along the Nile river. However, the reverence for the East-West path of Ra and Osiris remained strong. The Egyptians built the temples and the centers of commerce on the East side of the river, the side representing life and rebirth, in a city called Thebes. They built the tombs of the dead in the Valley of the Kings on the West side, the side where Ra passed into the underworld each night. / Map of Egypt
DURING QUEST EXHIBIT: Well, we hope that you enjoyed this journey into Egyptian astronomy. Be sure to visit the exhibit, The Quest for Immortality: Treasures of Ancient Egypt, which will be open from September 10 through January 31. Look for the pyramidion on the first floor of the exhibit, and see if you can see Ra and Orion.
I’ll stick around to answer any questions, or if any of you would like to try using the merkhet or find out more about doing this at home.
(automatically forwards to next slide) / Title slide with picture of pyramidion from Quest