How High Can We Build?

Hey, Vsauce. Michael here. And when the pyramids of Giza were built, the tallest was 147 meters tall, making them the tallest things humans had ever built. And they remained that way for nearly 4,000 years. It wasn't even until the 1300's that we finally got around to making something taller, a cathedral in England. So, does that mean that the Great Pyramids of Giza are the "Best tallest structures of all time?" Well, to find out more, all aboard the BOAT.

So, what is a building? Well, technically, a building is a structure in which at least 50% of its height comes from floor plates where people can live, work, chill out; it has to be habitable. Any less than that and it's not a building, it's a tower. After the Lincoln Cathedral finally surpassed the height of the pyramids, a number of churches continued to be built that kept breaking and setting new records. The next long-term record holder was the Eiffel Tower. It was the tallest thing, ever in history, that we had built, for about 40 years in a row. It was finally surpassed by the Chrysler Building in New York, a personal favorite, which was then quickly bested by the Empire State Building.

Now, the Empire State Building is interesting in that it was the first structure ever built by man that was so tall, were you to jump off the top of it, you would actually reach terminal velocity before you hit the bottom. It was the first structure we'd ever built that was so tall; rather than just continuing to accelerate as you fell, you would actually stop accelerating because you would reach the fastest possible speed your limp body can fall at. In the mid 1950's, something weird started to happen. Humans started to build radio and TV towers. These things could be way taller than the buildings that we'd made previously that had to be habitable.

And so, ever since the Empire State Building had its record broken by a TV tower, all these other famously tall buildings, the Petronas Towers, Tapei 101, the World Trade Center, the Willis Tower - formerly Sears Tower - none of them have ever, within their existence, actually held the title for being the tallest "thing" we've ever built. There was always a radio or TV tower somewhere that was taller. Up until quite recently, and for quite a while, the record for the tallest thing ever built by humans went to the Warsaw radio mast in Poland. It's visually incredibly striking because there aren't any other skyscrapers around it. It's all alone, being very tall.

Well, that was until 1991, where some workers exchanging guy-wires made a mistake and the whole thing started to bend and then snapped in the middle. There's no video of the event happening, but it would have been similar to this collapse, though much, much taller. After the Warsaw radio mast collapsed, the KVLY-TV mast in North Dakota became the tallest, still standing, structure built by man. But recently, buildings have made a comeback. And to check that out, we're going to have to travel to the Middle East.

This is the first time I've ever touched the Nile. Tadaaa. Ok, so that was me dipping my waterproof camera into the Nile. If you were to take the entire length of the Nile River and stand it up on its edge, perpendicular to the Earth, it would reach into outer space about this far, which is pretty impressive. But where does the space shuttle orbit? And where does the International Space Station orbit? This far away? This far away? Maybe this far away? Actually, if this pink, inflatable "Horrible Bosses" ball was the Earth, the space shuttle would orbit about right there. It's incredible, but it's possible because the shuttle, and the International Space Station, travel so quickly.

They travel so quickly around the Earth that instead of seeing one sunrise and sunset every 24 hours, they see 16. But don't be jealous. You can easily see more than one sunrise and/or sunset in a day by taking advantage of tall structures. So, let's take a look at the tallest structure, the current record holder for the tallest thing humans have ever built, the Burj Khalifa in Dubai. The height of this building blows my mind. You can literally watch the sunset from the base of the building and then take a super-fast elevator all the way up to the top and watch the same sun set again.

In fact, the difference in timing between sunset at the base and the top is so significant that the Dubai Islamic Affairs department actually had to make a ruling about when you can start, and break, your fast during Ramadan inside the building. People above floor 80 or higher have to actually wait to start eating 2-3 minutes after the people at the base because the sun hasn't yet set for those at the top. But before you head to Dubai to watch the sun rise or set twice in a day, keep in mind that the only height you actually need to see two sunrises or sunsets is the height of your own body.

Try this the next time you're at a beach. Watch the sun rise or set over the water. Water is important because it won't have the terrain and hill issues that land does. Now let's say you're watching a sunset. Begin by laying on your stomach. Watch the sun set and as soon as the very last little bit of the sun goes below the horizon, quickly pop up into a standing position and voilà, you'll see the sun's back - part of it’s back - and it will set another time. If you take a stopwatch and record the time between the first setting and the second setting that you witness and measure the height of your eyes when you're laying down and when you're standing, you can use those numbers to calculate the radius of the Earth.

XKCD took this a little bit further by proposing the "Double Sunset Date." Take your date out to the beach in a cherry picker and sure enough, it was calculated, given the speed of a cherry picker, all you have to do is move about 6 feet up and you can watch a beautiful sunset all over again. To put things in perspective, the Burj Khalifa is nowhere near as tall as Mount Everest. But the tallest structure that we could potentially build wouldn't be as tall as Mount Everest; it would be way, way taller. Like, into space taller.

Of course, the problem with building things that are really tall is that they get heavier and heavier and have to support their own weight. But only up to a point. If a structure was so tall that it wound up at the altitude of a geostationary orbit, it would start to feel a new force, not just a gravitational force downward, but all of the sudden this new, centrifugal force up and outward. And so, a building that tall could be stable through tension. And more than 35,000 km high. This kind of structure is known as a "Space Elevator."

Unfortunately, there aren't any materials known to science today that are strong enough to make building something that large feasible. With the exception, maybe, of Carbon Nanotubes or Boron-Nitrate Nanotubes. Of course, if we went to a smaller celestial body, like the Moon, we could build one today out of stuff like Kevlar. There are a lot of different things that we have to be wary of when we build a space elevator. For instance, how do we dodge space debris?

One solution is to attach the Earth side of the cable to a boat in the ocean that can maneuver around and move the elevator away from dangerous obstacles. Another interesting point is that the taller the cable, the faster the far end of it will be traveling. In fact, if the cable is more than 50,000 km long, its far end will be traveling near escape velocity and simply walking outside could take you to the Moon. But why build a space elevator? Well, because it would be awesome. But also for better reasons too.

For instance, right now, in order to send a pound of material into orbit, it costs about 11,000 dollars. But with a space elevator, we could send the same amount of material into orbit for only about 100 bucks. That difference is so significant that Philip Ragan has said that the first country to deploy a space elevator will have a 95% cost advantage and will possibly be able to control all space-related activities.

Alright, so here you see, in the mirror, Alex playing guitar while she holds a camera in her mouth and records us. Impressive. I'm here with Kristen from Barely Political. She's visiting London and if you enjoyed this episode of BOAT, check out other episodes; I've got them all up there. And as always, thanks for watching. Oh and check out Kristen's channel right there. Bye! Bye.