Why Earth Is A Prison and How To Escape It

Key Takeaways

we are prisoners on Earth the universe taunts Us by showing us all the places we can't ever visit however if our species wants to have a long-term future we have to escape our prison but what's keeping us here in the first place turns out we owe the universe a debt that is 4.5 billion years old [Music] [Music] everything with mass in the universe attracts every other thing with mass we call this phenomenon Gravity the closer you are to a big chunk of mass the stronger the attraction or the more you're pulled in this effect traps us on Earth we can imagine this as being prisoners in a gravity prison or a gravity well it's not a literal well but a handy concept to understand how this works being in a gravity prison means that you owe gravity energy but how can you owe energy because in our universe things don't want to change their speed or direction to convince them to move you have to expand energy billions of years ago the gravitational attraction of trillions of trillions of dust particles orbiting our sun pulled them together until they formed a planet this process used energy and created the gravity well we're now a part of the deeper you are inside a gravity well the more energy you owe gravity if you don't find a way to get enough energy you're not able to leave no matter what you do because your atoms were once part of the dust that the Universe expanded energy on to get to this place okay H let's summarize all of that again objects in the universe don't like to move you have to convince them to do so with energy Gravity used used energy to convince the parts that make up our planet to move together this created a gravity prison in the process trapping us to escape it we need to repair it with energy okay how do we do that to get into space we need to go through a complicated process of exchanging energy for this purpose we build a negative potential energy repaying machines known by their more boring name Rockets rockets work by using some of the most energetic chemical reactions humans know about to basically explode fuel in a controlled way this converts chemical energy into kinetic energy the exhaust of the reaction is directed outwards and pushes the rocket away from Earth by expending a lot of energy we are increasing our gravitational potential energy which is a complicated way to say that we're paying back our energy debt to gravity but it's actually a lot trickier than that when you burn fuel to get into orbit you lose lots of energy to heat the exhaust and Atmospheric drag so you actually need much more and you can't just p a huge amount of really explosive dangerous fuel close to your payload and detonate it you need a controlled burn which is complicated and makes your rocket very heavy which means it has more mass The more mass something has the more energy you need to convince it to move so you need more fuel to lift up your rocket but if you need more fuel that means you need more rocket to carry that fuel but this makes your rocket heavier thus requiring more fuel which requires more rocket to carry that new fuel and so on at the end of this madness you need closer to 100 times the weight of your payload to launch Ariana 6 for example the European rocket will weigh 800 tons and should be able to transport 10 tons into geostationary transfer orbit or 20 tons into medium earth orbit but a rocket can only produce so much thrust so there's a maximum weight after which it just won't take off if you add too much weight it won't lift off so you can't just build bigger and bigger fuel tanks this is the tyranny of the rocket equation and it means space flight will never become easy but wait it gets worse getting to space is still not good enough you're still inside the gravity prison at the edge of space and will crash back to Earth staying in space is much harder than getting there to get to a stable position where it can stay for a while the rocket has to reach low earth orbit to do this you need a lot of kinetic energy which means going extremely fast at an altitude of about 100 km this is 8 km/s 28,000 km/ hour fast enough to travel around Earth in 90 minutes here we can use a trick instead of flying straight up we can go sideways Earth is a sphere so if you're going sideways fast enough even though you're falling towards Earth the ground will curve away beneath you so as long as you're above the atmosphere about 100 km up you'll be able to stay up there in orbit this is what the ISS does falling around Earth expending energy from time to time to stay fast enough if we look at orbits in scale we see that near Earth orbit is laughably close to Earth to deploy for example satellites or leaf for other planets requires another round of energy debt repayment getting to orbit is the most difficult part of space line for us right now for example if we want to send a rocket to Mars half the energy is necessary just to get into orbit and the other half for the 55 million km to Mars therefore to be as effective as possible Rockets aren't built in one giant piece instead we use multi-stage Rockets you don't need to carry an empty fuel tank so Rockets drop it Rockets today shed their boosters and Main stage as they ascend with each successive stage being its own fully contained rocket complete with its own engine and fuel okay so this is why getting to space is hard if you feel all of this seems really complicated don't worry it's literally rocket science this video was made possible in part by a sponsorship by Airbus saffran launchers and Ariana space who are getting their new Ariana 6 rocket ready to launch into space in 2020 you can learn more about the rocket here and as always if you like what we do please consider supporting us on patreon.com it really helps us out a lot if you're craving more space stuff now here's a playlist for you