字幕表 動画を再生する 英語字幕をプリント Ok, so we are going for a ride around the pyramids. The great pyramid was the tallest man made structure for nearly 4000 years. Only surpassed by a large margin by the Eiffel Tower in 1889. 147 metres high You are interested by climbing? Yeah! Let's climb it! But is not free. How much? What makes the pyramids even more impressive, is that these structures were built over 4500 years ago, when Egyptians didn't have wheels or steel. The only metal available was copper and copper alloys. It took about 2 million stones to build that pyramid. Well, I call them stones—giant rocks. Somewhere between 1.5 - 3 tons each Pyramids took about 20 - 30 years to make. That's a long time, but if you think about the number of stones, a couple million stones in every pyramid, you'd have to be laying a stone roughly once every... 3 minutes. If you consider a regular work day, like a 10 hour, 12 hour work day. Nobody knows how they built it. Still secret. But a lot of people just try to do the best to give you some information about how they did it. But we must say it's secret. The dead and the thing that sealed them. Nobody knows. No plans survived to show us how the pyramids were built, so perhaps it's not surprising that this is the subject of countless conspiracy theories involving aliens, time travel, or lost technologies. But there is a less far-fetched myth which has become widely accepted, that the pyramids were built by slaves. But recent discoveries suggest that the pyramid builders were not slaves at all. They were skilled workers. Well-preserved tombs near the pyramids suggest that their hard labour and sacrifice were rewarded. If these workers had been slaves, they would not have received such honourable burials. But how did they actually manage to build the pyramids? One of the things I find really interesting is that the Egyptians didn't know about wheels, so they didn't really even use rollers, as far as we can tell. I mean, these rocks would have been carted across the desert on sleds. There's a famous diagram of this giant statue being pulled by 172 men, and that, that statue would have weighed somewhere on the order of 68 tons, or something. This would normally create a lot of friction, but the sand was wetted in front of the sled. Experiments show this would reduce the pulling force required by half. The internal stones of this pyramid are all limestone, which is a bit softer and easier to work. You can imagine them working it with those copper chisels that they had. Some of these blocks may have been actually sawed through using copper saws. Now you wouldn't think that copper could really cut the rock, but if you put an abrasive in there, like a sand, you could actually wear away the stone. It would probably be a very difficult and labour-intensive job. Something that you don't really think about is that when you build a pyramid you need to build it on level ground. You can actually see there how they had to level out that ground. Well it's speculated that when the Nile flooded, they put the flood water into a channel and see where the high parts were. So the inside was made of this limestone. The outside of this pyramid was actually made of granite. Much harder stone. I'm at the granite quarry in Aswan where they would have quarried the stones that were used in the pyramids at Giza. Now that is an incredible feat because this is nearly 1000 km away from Giza, and when the Nile flooded, water would come right through here so that they could move all the stones quarried here, this granite, they could move this back up to Giza and use it on the pyramids. These would of had to have been floated down on rafts. Now quarrying this would have been really hard. Granite is one of the hardest rocks because it contains quartz, and quartz on the hardness scale is about a 7, where diamond is a 10. So how would you dig a massive trench like that? Basically the technique was just to smash the dolerite rock into the granite over, and over, and over, again. They would make about 5 mm progress per hour. So there is no clear account of how the pyramids were actually built, but the best guess is that ramps were used. And in fact some ramps have been found on incomplete pyramids. But you can't build just a straight ramp, a long straight ramp, and keep putting the rocks up. I mean the problem with that is the ramp actually ends up taking up more material than the pyramid itself. I think a ramp which sort of wraps around the pyramids is probably the most likely thing. The top third of the height of the pyramid actually only accounts for about 4% of all the material in the pyramid. That's why it's suspected that levers were actually used to finish off the pyramid, to do the top levels. Now the pyramids have clearly weathered, but in the past they would have been a brighter white because they would have used a white limestone to cover the whole face of that pyramid. And then the very top may have been covered with electrum, which is a mixture of gold and silver, so you can imagine, that would be a pretty spectacular sight. The reason these pyramids are shaped this way is so they represent sun rays. Imagine what that would have looked like when it was first built: With a shiny metallic top, and smooth white finish on all of the sides. I think that would have been a sight to behold. Hey! I hope you enjoyed that video, I filmed it earlier this year when I was in Egypt. Now I'm currently in Melbourne, Australia and tomorrow I am flying to the US. In fact next week I'm actually doing a live show in Alabama with Henry from Minute Physics, Dustin from Smarter Every Day, Brady Haran from Numberphile, Periodic Videos, and Sixty Symbols, and CGP Grey from CGP Grey. Yes, he will actually be there in person, so if you want to come and join us, then checkout the link in the doobly doo. You know on all of these long flights I always need something to help me pass the time, and I know what I'm going to be doing tomorrow, I'll be listening to the brand new audio book from Bill Nye. The book is called Undeniable: Evolution and the Science of Creation, and he actually narrates this book himself, so I can't wait to listen to it. And if you want, you can download this book for free by going to audible.com/Veritasium or you can pick any other book of your choosing for a 1 month free trial. So I really want to thank Audible for their support, they've helped me go to all of these amazing places, and they have hundreds of thousands of audio books, so if you love audio books you should definitely try them out. So thank you for watching and hopefully I will see you next week.