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TEDx Talks
Published: 2016-06-02
Source: https://www.youtube.com/watch?v=EBebWBjpWIQ
all right before I start talking about T. matter physics and rockets going to other stars travelling interstellar I think it's important that we ask ourselves the question then is why explore space you know we have so many problems on here on earth in the global warming hunger war why should we spend time spend money and effort going into space and we could be spending that time
and effort here on earth you know I could I could list all of the technological advances the medical breakthroughs of over four decades of human space travel in space but I think the real question is why explore and I think simply the answer is it's in our DNA we are the descendants of people who were curious and who explored their environment and I think we need
to continue doing that but there's a problem is a big problem and that is that rockets are too slow in order to demonstrate that our fastest object that humans have ever created is the Voyager one spacecraft that moves it fifteen kilometers a second now that may seem like a fast speed but if you want to go to Mars with at that speed would take months to
get there if you wanted to go to Pluto which NASA just did and they spent billion dollars in ten years to get there it's just takes too long in the final example is really the most important one is that if we want to get to another star our closest star system Alpha Centauri and see their is about four light years away that's thirty eight million million
climbers so will take about thirty thousand years at fifteen kilometers a second to get there and and I don't wanna wait around for that so luckily human beings are actually quite good at developing tools that allow us to explore our environment the seventeen hundreds we build very accurate measurements of time we built the chronometer that allow us to travel to seize and allow for the really
the golden age of exploration in nineteen hundreds the Wright brothers that all flight really allowed us to master the skies now if you really want to explore beyond our solar system we're gonna have to come up with a new tool it being an antimatter physicist I'm kind of partial to antimatter but knew that it could be something else that could be later portion could be phaser
fusion or or solar cells %HESITATION some physicist even think that we can bend spacetime and travel faster than light but I think antimatter is actually the nearest term %HESITATION and most realistic so a little bit about anti matter yeah I was first %HESITATION predicted by Paul Dirac up there in the top right corner you know he was actually struggling with two relatively new concepts one being
special relativity which describes really life it really high speeds %HESITATION and speed of light I am quite a mechanics scribes through the earth or the world of the very small atoms and molecules so is solving this %HESITATION relativistic quantum can't execration came out with a two answers a positive energy in the negative energy for these particles now how many times I've been doing your homework and
you scum of the native answering your sales throw that away loosely that positive energy solutions because that that's what makes sense but Paul Dirac was a genius in that he saw these negative energy solutions they said wait a minute maybe there's a whole new set of particles out there that we have even seen so some people thought he was crazy of course but it was only
three years later that Carl Anderson at Caltech saw this in his cloudscape he saw the track of the particle going %HESITATION you'll curving and it had the same energy and mass is an electron but was actually curbing the wrong way issued and curving to the right it was a a few with an electron so this is actually the first experimental evidence of antimatter or an anti
electron if we like to call positrons so antimatter I like to describe as mere matter so if there was an anti you and in a mirror it would look exactly like you %HESITATION accept everything would be flipped and the same is true at the subatomic level %HESITATION anti electrons of the same mass is an electron just positive charge rather than negative charge that's why we call
them positrons so an interesting characteristic of antimatter is annihilation %HESITATION it's quite unique in that if you have an anti matter particle and a matter particle and they get close enough together they'll both disappear and turn into pure energy are now this is the universe's most efficient means of turning mass into energy and it's actually quite powerful that's actually what got me interested in positron physics
%HESITATION years ago what is that mean in terms of energy density if you had a clump of antimatter well anti matter has about ninety mega joules per microgram I know that doesn't mean much to you but odds for them or familiar terms IQ anagram of antimatter or Eminem sized piece of antimatter have the same amount of energy has about eighty kilotons of nuclear weapons or alternatively
about ten million liters of liquid natural gas without a full tank of so not only does antimatter have incredible promises as a fuel for spacecraft but this has some pretty significant %HESITATION applications in in the future of energy research %HESITATION energy production %HESITATION especially in inertial confinement systems and post energy delivery but I'm more interested in the propulsion side of things and so is my company
I know the original concept of antimatter propulsion it was actually developed in the fifties %HESITATION by Eugene Sanger and what he did was he said what if you had a clump of antimatter you took it out in your spacecraft and then you annihilated it in there rocket engine nozzle and you're able to direct that energy flow you drip you're able to direct those gamma rays %HESITATION
so that you have thrust in one direction %HESITATION this was is was %HESITATION cutting edge at the time but there were really three problems one of which was production you you can't create enough antimatter to do this unfortunately the other is is that you can't trap the antimatter of course the that property of annihilation which is good for %HESITATION energy density is actually really bad for
being able to trap also you need a very high strength magnetic fields and just wasn't feasible it still isn't feasible to trap large amounts of antimatter the third problem with the original concept %HESITATION was directing that energy %HESITATION gamma rays are much higher energy than xrays of course if you go through the TSA and in the airport they xray your bag xrays tend to go through
everything and gamma rays even more so so Rick reflecting gamma rays is is something that we can't do right now so I started thinking about these problems %HESITATION in twenty eleven finishing up my PhD in positron physics and I realize that the real issue the limiting factor was when you went from hot positrons to cold positive now state of the art in twenty eleven %HESITATION you
had your source of hot positrons you knew what they did over the care they still do really is to run it through a solid piece of material and what this does is it's very thin so that most of positrons just travel right through a very small number will actually stop inside material %HESITATION of course a large member of those will hit an electron because our matter
is made of lot of electrons and they will lose it a very small number about one out of a thousand will actually make it to the surface and be admitted as a cold positron so you have to be able to create called positrons in order to work with them may come out %HESITATION a million times harder than the surface of the sun so you have to
be able to cool them down in this process was very inefficient so we started thinking of new ways to do this are my lab partner and I discussed this of about a year our cable for a napkin sketch of the array moderator %HESITATION soon after that we made it an actual patent %HESITATION and then actually asked for some money from a grant and we are funded
by the feel foundation ought to do the initial proof of concept on that %HESITATION moderator so this moderator now forms the heart of all of our propulsion concepts in that little piece of there is actually very tiny it's about three by three millimeters but it's the source for all of our anti matter %HESITATION concepts so I know it when you're developing a concept yourself to develop
a team so back in twenty twelve I asked some friends of mine who was working on another rocket project there in the desert with I said well let's let's give up this chemical stuff why you guys come help me build an antimatter rocket who's gonna say no to that %HESITATION so we are we rented a little office %HESITATION brought in a bunch of nuclear science equipment
weekly realize that %HESITATION landlord didn't appreciate that us we got kicked out of there %HESITATION in the next year we moved into the more appropriate facility %HESITATION and then last year finally we're gonna we made our way down to a nuclear fallout shelter with a clean room and so this this new facility will allow us to develop some of our concepts and integrate them into a
cube sap which is a very small satellite very easy to launch very easy to demonstrate new concepts on so how to get around those three issues production trapping in directing energy well the first two issues of production and trapping are you really get around by having a very efficient moderator well we use a radio isotope source of positrons tenuously admits positron now we run it through
our little tiny moderator and we can create a very high intensity positron beam now the third challenge of directing the annihilation energy now in order to do that we transfer to Connecticut orgy of the camera into a charged particle via fusion reactions and now we have a charged particle that's high energy rather than a gamma ray that's important because charged particles like to follow if magnetic
field lines as you know from the aura borealis so we use magnets like the one the bottom right there out actually direct energy and produce thrust so in about two years we're hoping he'd put a demonstrator cube sat the little tiny spacecraft in orbit and so why is this useful what what is a really small spacecraft and do for you well turns out of about four
billion people on the surface of the earth earth don't have access to internet so there's a lot of companies that want to launch constellations of small satellites into low earth orbit and what level do not create a global network of broadband internet so that anyone can access that information I think that would be incredibly incredible opening door %HESITATION for the earth I look at further down
the road but we want to do and what government agencies want to do that and %HESITATION some private company like SpaceX they want to send things out to Mars and our technology would allow me to do that and then cut the transit time significant and then kind of a far out application for this is asteroid mining I know you probably heard of asteroid mining but turns
out the very small asteroid in our asteroid belt metal rich is worth a lot of money and %HESITATION with chemical rockets you can't just go out there and get you need something like an intimate system so in terms of our extending this technology into human space travel %HESITATION that will create required course line work %HESITATION it turns out that are squishy bodies can only really %HESITATION
handle about one G. of acceleration anda even so one G. nine point eight meters per second per second is actually pretty high acceleration are you know NASA took ten years to get Pluto if we if we got one G. we can get there in about three and half weeks %HESITATION which isn't that bad %HESITATION if we want to go to hell for the tar the story
gets a little different and we start the ringing and concepts of special relativity %HESITATION now if we wanna go out there at four point three light years that one GE take about five years going about eighty five percent the speed of light now once we start getting towards a significant fraction of the speed of light we start getting time dilation which is an interesting phenomenon but
really it's the thing that allows us to travel out into this into the universe are so well five years has elapsed on the spacecraft and only nine years has elapsed on earth it's getting weird but still feasible %HESITATION if we extend this out to Kepler four fifty to be now Kepler four fifty to be is an interesting place because what people call it earth two point
now it's a little bit bigger than earth within the habitable zone of its sun so it's actually a lot of people want to go there and see what maybe there's life and I think there's a good chance that there might be although it is fifteen hundred light years away with our one G. spacecraft we can get there in twelve years I'm on the spacecraft unfortunately fifteen
hundred years will have passed on earth so things are getting a little weirder %HESITATION now if we look at the ultimate application of this exploring the edges of our universe thirteen point five billion light years away at one G. we could make it there any human lifetime thirty years now we're going incredibly fast towards the speed of light but merely problems at thirteen point five billion
years years would've passed here on earth so when trying to say is that with the transformative technology like this we have to think seriously about the consequence %HESITATION and actually new questions arise are the first of which is if we want to really explore beyond our solar system %HESITATION into our galaxy we're gonna have to do it ourselves our if we do send the probe a
robot we'll never hear back from it essentially and then the second issue is that if we do want to go out into beyond our %HESITATION galaxy we're gonna essentially be saying goodbye to this and you know human beings used to be a nomadic species so one questions I am asking you is that do we want to become nomads again thanks very much
