Great science from pointless questions Danail Obreschkow TEDxPerth

science is profoundly human adventure it is an endeavor of building knowledge interestingly many useful scientific discoveries arose from seemingly pointless questions that simply sparked the curiosity of scientist well am scientist and love pointless questions stay with me for instance imagine large body of water and now cut out small pocket of water to make an empty bubble let's just call this cavity what would happen to such cavity well the water would push into the cavity to make it smaller and smaller and still smaller in fact millimeter sized cavity would only take hundreds of hundreds of second to collapse at the end of this implosion when the cavities ball crashes into itself at supersonic speed then it's full motion energy gets compressed into virtually single point researchers found that this highly concentrated energy can then escape in the form of fast water jets shock waves and sometimes flash of light emitted by compressed gas hotter than the surface of the Sun scientists still don't quite understand how much energy goes into each of these channels so my colleagues and decided to find out by asking nature itself we decided to measure precisely the chat's shocks and light of cavities in various conditions but to simplify the challenge we chose to start with the ideal case of single isolated extremely spherical cavity now making such perfect bubble really isn't easy it required us to design an optical system that is able to focus laser precisely in water at the focal point the laser produces small explosion that then generates the most spherical cavitation bubbles ever studied there is only one problem with these bubbles gravity the force of gravity eventually distorts every spherical cavity into an odd pear shape so if we are serious about studying the most simple situation we must remove gravity but this is easier said than done since the only way to remove gravity is to be in freefall you are experiencing short moments of freefall in bungee jump during the first seconds of skydive or on diving roller coaster however these scenarios are way too scary for our experiment we would like to have more stable and longer free fall trajectory such as on spaceship in orbit which is in endless freefall around the Earth more economical way our so called parabolic flights where an aircraft injects itself into an arc of an ellipse once when was still physics student my friends and had drink after an exam when suddenly poster caught our attention it was opposed to by the European Space Agency ISA announcing an international contest for students to fly their own experiment on parabolic flights now this was game-changing moment in our lives we went for it won the competition and just months later our experimental setup arrived in Bordeaux France ready to be loaded into the world's largest aircraft for parabolic flights in the early morning when everything looks so calm from the outside our team of scientists and engineers is enthusiastically getting the experiment flight ready and just before the doors of the aircraft get closed for departure smuggled an Australian rules football into the plane for bit of fun now ladies gentlemen fasten your seat belt as we are about to take off on the Airbus a310 zero-g once established in cruise flight in military airspace above the Atlantic Ocean the pilots steadily pull up the nose to 47 degrees above the horizon during this slow turn the passengers are in hypergravity the football now has twice its weight you feel like you are glued to the floor and raising your arms is like weightlifting but then the engines get turned down such that the entire plane moves just like piece of rock thrown into empty space this plane isn't flying anymore it is falling with style for 22 seconds everything is in freefall you feel light like feather and you get strange perception that up and down have disappeared there is no notion of the fact that we are all on huge ballistic trajectory but towards the end of the parabola the plane is now diving towards the ocean and the pilots must recover it by pulling the nose up again leading through another face of hypergravity back to steady cruise flight and then this whole manoeuvre is repeated 30 more times over the past years our team has accumulated nearly 800 parabolas worth about five hours of continuous weightlessness and whenever we are floating the bubbles start to dance slow motion movies reveal the hidden Beauty taking place in just blink of an eye zero gravity lets the bubbles collapse with nearly perfect symmetry and 10 million frames per second we registered flashes of light and shock waves stronger than ever observed on the ground most importantly we were able to directly compare identical bubbles in zero gravity normal gravity and hypergravity this comparison led to predictive theory for the amount of energy cavities turn into jets shocks and heat as function of the surrounding pressure gradient interestingly these models are turning out to be useful not just in space but right here on earth this is because cavities in complex pressure fields are infected commonplace for instance behind the moving edge of spinning ship propeller the pressure can be so low that the water literally gets ripped apart into cavities closer look at similar blade exposed to cavitation for some time then reveals lot of damage on the metal done by millions of little collapsing bubbles Nature has already learned to harvest this destructive power for instance the odd-looking pistol shrimp with its huge oversized right claw produces bubble whose collapse shock can then destroy prey at distance we humans are also learning to benefit from cavitation artificially induced bubbles can already be used to destroy bacteria in dirty water to remove kidney stones and even to kill cancer cells in living tissue since our models have the potential to help improve such beneficial applications most of our current research is actually focused on biomedicine initially we had no idea where this research was going to lead us it was hard to foresee that curiosity driven questions can take you to zero gravity let alone that the results would yield some practical benefit this shows the value of blue-sky science basic research is not about addressing eminent practical issues but about supplying basis for answering the questions of tomorrow thank you you