When black holes go faster than light

[Music] one of the great things about making videos on YouTube is the feedback that you get in the comments it's not that sort of feedback I mean the feedback you get from really clever people watching your science videos like you'll get someone who works in the particular field that the video is about giving you extra insights or you'll have someone asking probing questions that you hadn't thought to answer in the original video I asked recently on social media are there any videos that you really want to see a follow up on and a lot of you said that you wanted to see a follow up on the gravitational waves video but where I spin the black holes faster than the speed of light what a great idea if you haven't watched the original video yet I recommend you do that first the link is in the card there and in the description but a quick summary gravitational waves are essentially ripples in the fabric of the universe and we detect them here on earth when distant massive objects like black holes move backwards and forwards really quickly for example if they're orbiting around each other and so I'm representing the fabric of the universe with this literal stretchy fabric and I'm representing the black holes with these wheels massive objects like black holes warp the fabric of the universe so I'm simulating black holes warping the fabric of the universe by pressing the wheels into the fabric and look you can see as the black hole's orbit each other that backwards and forwards motion causes ripples in the fabric of the universe to radiate outwards and they'll eventually reach our detectors here on earth in my simulation I was spinning my wheels lack holes close to the speed of light in my fabric universe and you can see what the speed of light in my universe is because the speed of gravitational waves is also the speed of light so look this ripple this gravitational wave is traveling at the speed of light in my universe this is slow-mo footage the actual speed is about eight meters per second so I was spinning my black holes just below eight meters per second and your question was what happens if you spin those wheelie black holes above the speed of light in universe above the speed of gravitational waves in the original video I was able to capture a kind of fake slow-motion footage using the stroboscopic effect unfortunately you can't use the stroboscopic effect to capture faster than light travel you need an actual slow-motion camera fortunately Destin from smarter every day was visiting me in London a few weeks ago to film a collaboration video link to that in the card in the description as well he brought his slow-motion camera with him and he was out for the day we went to a conference and he left the slow motion camera with me to play with so I was able to capture this slow-motion footage of faster-than-light travel so look when you get to the speed of light the wavefront bunches up but in front of the black hole and if you go a little bit faster than the speed of light that bunching up in front of the black hole generates these ripples that propagate behind the black hole a bit like the wake of a ship which totally makes sense actually because ships tend to travel faster than the ripples across the water that they create so you end up with this triangle behind the boat it's also like breaking the sound barrier you have this cone of sound that propagates outwards behind the aircraft sound waves interfere constructively at the surface of the cone so you get a spike in amplitude you experienced that as a sonic boom as the cone passes over you and you can see a similar thing here when you get past the speed of light these ridges form which is like the spike in amplitude you experience with a sonic boom where the ripples are constructively interfering with each other that's my hypothesis anyway in a minute I want to show you the disastrous consequences of going much faster than the speed of light because it's really interesting but first I want to just quickly answer a follow-on question that a lot of people had so a lot of people said can you show us what happens when you go faster than the speed of light and would that be a good illustration of what happens in our universe when we go faster than the speed of light and I think the answer to that question has to be no it would not be a good model of what happens when you go fast in the speed of light in our universe because in our universe you simply can't go faster than the speed of light and you might sell well ok yeah technically you can but like imagine if you could would it look like that and I still think the answer has to be no because well there's a couple of good reasons why you can't go faster than this be the right now universe the first is as you get closer to the speed of light it takes more and more energy to accelerate to the point where if you actually wanted to reach the speed of light you will need to input an infinite amount of energy to get there it's not possible the other issue is if you go faster than the speed of light it breaks causality so cause doesn't follow effect anymore you can travel back in time and you know kill your grandfather before he gives birth to your father and you know create those kind of thought experiment paradoxes that you hear about so two good reasons why not you might say yeah ok but like if you could would it look like that here's why I think the answer is no it because well it comes down to the way we build models if you have a model for the universe it's really important to probe the limitations of that model like the model that I have here is essentially a model of Einstein's description of gravity so Einstein says massive objects warp the fabric of the universe and I'm showing that here except what he specifically means is massive objects warp space-time space-time is this four dimensional thing three spatial dimensions and a time dimension they all get warped and I'm clearly not doing that in my model I'm warping two spatial dimensions I'm not warping time at all so you don't get you know Lorenz contractions you don't get time dilation you don't get any of that good stuff in relativity that leads to these mathematical singularities that you can't go beyond that means you can't break the speed of light in our universe so the reason this model isn't a good description of what happens in our universe when you go faster than the speed of light is because this model is limited in terms of its explanatory power like it's a good way of explaining what happens when an object that warps its surroundings moves backwards and forwards when it move backwards and forwards the warping of its surroundings travels outwards like a wave and that's a good analogy for the detection of gravitational waves were essentially detecting the backwards and forwards motion of black holes when they orbit each other but beyond that the model starts to break down because we're not really warping space-time and we're certainly not warping it in the strict mathematical sense as described in Einstein's theory of gravity but I'm still glad I tried it because you know I'm in the business of trying to explain things as well as I can like that's that's what I strive to do so it's important for me to probe the limitations of the tools that I use to explain things and it's kind of an analogy for how science works like all of our theories are essentially just models that try to explain the workings of the universe like quantum mechanics is a set of equations that model the universe when you solve the equations it T it seems to show you what we actually observe in the universe except that we know the model is incomplete because it doesn't work for extreme masses and velocities and the exciting thing is that's when new scientific discoveries are made they're made at the boundary of the descriptive power of the models that we use I think we should be grateful that we can't go faster than the speed of light because it's quite dangerous look what happens the fabric of the universe is torn a path and look control over those black holes is ripped out of the hand of God so I guess we should literally be thanking our lucky stars this video was curiosity driven it was driven by your curiosity to find out what happens when you do this thing now I'll talk about the elements of curiosity like inquisitiveness obviously that's an important element of curiosity like a willingness to figure out where your ignorance is and to step into that ignorant and have a look around you know until that ignorance turns into enlightenment another important element is seeking out the opinions and ideas of other people that's what I try to do on social media and in the comments on YouTube if you're interested to hear about other elements of curiosity then I encourage you to click on the sponsor link in the description I hope you enjoyed this video if you did don't forget to hit subscribe and I'll see you next time [Music]

Channel: Steve Mould

Views: 1,229,214

Keywords: Explained, understand, LIGO, gravitational waves, Einstein, General relativity

Id: 1nkhelaMaIA

Length: 9min 29sec (569 seconds)

Published: Thu Nov 07 2019