Transcript

The inertia of ideas through the universe | Jason Spyromilio | TEDxAUEB

um i love inertia inertia tells me where i am it tells me how i'm moving gives me a frame of reference for my physical existence and it gives me a frame of reference for my thoughts because ideas which i love having ideas have inertia too good ideas have lots of inertia good ideas have huge amount of inertia and bad ideas have no inertia bad ideas you can push aside it's very easy they have no weight what i'm going to try and talk to you today about is how you build inertia for ideas because if you have the way of building up and working out which are the good ideas and which are the bad ideas you're free to have ideas you can have as many as you like because the bad ones you'll just throw away it's not a big stress you just keep on having ideas so i'm going to tell you about the inertia of ideas there's only one truly bad idea and that is the idea that tells you that there are some ideas that you should not test that is a truly bad idea all the others can be tested and you can have whatever you want however much fun you want with those ideas now i'm a physicist so i'm going to try and walk you through a story of ideas in physics and for that i need you to know a little bit of physics so we're going to have one slide of physics and i hope this will not be too traumatic for all of you and this is the bit of physics you need to know the universe is very big now that is not an obvious statement that the universe is everything is relatively straightforward the word actually says it but that it's big is a different thing now the reason this piece of physics matters is because if the universe is very big there's only one force that governs how the universe behaves that's the force of gravity all the other ones that make radios work and atoms and all of this thing happen they don't matter the universe doesn't care because the universe is very big so if you're going to talk about gravity you have to talk about this fella this is a drawing of isaac newton now isaac newton was probably the smartest person to have ever lived at the time that he was around smarter than every single person any person that lived before him and he did amazing things but today we're talking about ideas of gravity so we'll talk about gravity and it's a famous story amongst physicists anyway that newton sat under an apple tree saw an apple fall and wondered how that worked now that's quite a complicated thing to happen because an apple falls down in greece but it also falls down in australia but in australia down is the other way around so how does the apple know that's quite a complicated process and quite a complicated piece of physics but he had a great idea about how that worked things attract each other and gravity pulls things together and with this brilliant idea he could explain why apples fall down doesn't matter which side of the planet you're on and how the planets went around the sun this idea could be tested it could collect inertia it could be an idea upon which we could build other things it was a strong idea it was a good idea it had inertia it was such a good idea that in the 1800s astronomers like myself measured the orbit of uranus planet the last planet we could see and worked out that there was something wrong with the orbit of uranus it didn't fit with newton's idea what should we do and in fact the idea is so good that it could predict and it could test and they said there has to be another planet outside uranus outside the orbit of uranus there had to be another planet and in fact they said it had to be exactly there so astronomers went and measured and found neptune neptune was discovered because we tested an idea so i mean amongst astronomers this is pretty cool we found a planet right this is this this is this is great if you can measure some planets find the problem and then you find other planets now this is cool so we went off and measured all the planets trying to find a mistake and in fact mercury also had a problem in its orbit mercury's orbit was wrong by half an arc second a year now an arc second is a an angle it's a small angle if you held your arm at your thumb at arm's length and you cut your thumb in 3600 slices and our second would be one of those slices and mercury was wrong by half of that every year and we looked for the other planet well i didn't just 100 years ago looked for a hundred other planet couldn't find another planet to fix this problem we have to go to another very clever man another very clever idea einstein einstein comes along says i've got a theory the general theory of relativity and with this theory space bends and funny stuff happens and mercury's orbit is right the 43 seconds a century goes away it can be tested the enormous inertia of newton's idea goes away because it tested and failed it's a profound moment in physics but also in the development of ideas now einstein's general general relativity predicted all kinds of other stuff they predicted that the light from objects would be changing its course as it passed the gravity of heavy things and arcs in the sky would appear arcs like these ones the yellow galaxies that you see here are closer to us and the stretchy things the arcs that you see around the galaxies behind this cluster of galaxies and their light has been bent by the gravity of the objects in front this is a test of an idea the inertia of the general theory of relativity increases you have great confidence about what is happening the general theory of relativity is so great a theory that we can actually model and work out what the entire universe is doing this very big thing right not little things this is a very big thing everything we have a theory to actually explain how everything is behaving and einstein puts all his equations together and he finds that the universe is kind of like he wants to maybe wants to get a little bit smaller maybe a little bit bigger it's it's not quite sure it's it's it's like on an edge and you go to the astronomers and says what's the universe doing it says nothing nothing nothing it's just sitting there he's doing nothing so scratching his head he says i can fix that so einstein introduced the cosmological constant the letter lambda is familiar to all of you capital version of it it's uh it stands for i said the cosmological constant and this fixed the universe it no longer was trying to do one thing or another it just stayed still and all was good until uh astronomers started measuring the universe because now we had a theory we could actually test we could go i'd say so measuring the universe is pretty cool you can actually measure the whole universe this is nice you need telescopes and we build lots of telescopes they're kind of expensive and big and all kinds of other stuff but it's cool you go out and measure stuff and rather famous astronomer you may have heard of edwin hubble use this telescope this is the hundred inch at mount wilson and he measured how style how galaxies were moving in the in the universe and how far away they were and he worked out that the universe was not kind of doing nothing actually was doing something very important it was getting bigger the universe is expanding now that messed up einstein so we threw away lambda it didn't matter that einstein came up with it it was a bad idea could be tested and it was a bad idea and we have this beautiful result now we have a universe that is actually getting bigger now that's kind of weird because you'd like to know what it's going to do so our universe has stuff in it we know that because we're here right you're here so the universe has stuff in its stuff has gravity so the universe as it's expanding has to do one of three things if there's a lot of stuff in the universe then the gravity will actually hold it together and at some point it will stop expanding and it will actually get smaller again if the universe doesn't have enough stuff in it then it will keep on expanding forever but it will slow down because stuff has gravity so it will be slowing down but it will never slow down enough to to stop getting bigger and if the universe is just perfect just right absolutely perfect it will become the perfect size it will expand and end up being the perfect size it will take forever but it will become the perfect size and that would be a perfect universe so measuring how the universe is growing is fun right i mean you know who doesn't want to know well maybe you don't want to know but you know i think if you're asking questions it's a pretty good question to be asking now one of the things about the universe being big and expanding is that at some point it was smaller than it is today and if we're smaller and has all the stuff it'll be hotter too and that heat is light and we can see this light in fact every time you tune your television you see this white snow some of that white snow is some of this light and by measuring our universe when it was much younger we can work out certain things we can work out in fact that our universe is perfect it's one of these perfect universes this is a picture of our universe when it was a baby so in the equivalent age it would be a picture of me when i was 10 hours old so this is a picture of our universe when it was 300 000 years old today our universe is 13.7 billion years old in fact we know the age of our universe more accurately than most people in this room know their own and this picture tells us something very magic it tells us that our universe is complete it tells us that their density is exactly the right one so now we can go out and measure the deceleration how it's slowing down and we can do amazing things we have an explanation for how our universe works that's a very strong idea it's pretty cool so in the mid 1990s two teams of astronomers uh decided to go off and measure how our universe was slowing down for that uh i was part of one of the teams we use supernovae supernova bright explosions of stars in other galaxies and they become very bright and you can see them at great great distances and you measure them and you can measure how far away they are and you can measure how our universe is behaving well um bit of a problem because our universe is not slowing down it's full of stuff but it's not slowing down in fact our universe is expanding in an accelerating at an accelerating rate our universe is getting bigger faster our universe is made of very weird stuff my universe is made of things like us the stars the galaxies the planets yourselves the chairs all of this is four percent of our universe even the stuff between the galaxies all of that is four percent of our universe 23 percent of our universe is uh stuff we call dark matter which changes how our galaxies turn and how they get put together etc etc but what we discovered in 1998 is that 70 percent of our universe today is made out of a thing we call dark energy we have a good name for it we do not have any idea what it actually is but it is making our universe get bigger faster it's never going to come down and the future is very very very dark and bleak not to worry not in anybody's lifetime but we are physicists and we need to have a mathematical way of describing this and i'm sure you can guess what we're using lambda the idea that was bad the idea that we threw away because it didn't work with the test can bring it back and in fact the cosmological constant is one way we describe this bizarre universe in which we live in so i love the inertia of ideas i love the process which allows us to challenge any idea with a test ideas that cannot be tested don't have inertia they may be fun to have and you can live with them and have a great time but they do not carry weight they're great and can be entertaining but we build edifices on top of inertia and the process by which you free yourself to have any idea you want is the process by which you subject your ideas to test and you are happy when your bad idea dies because nobody wants to have bad ideas hanging around thank you very much