Bonus - Dark Sky Conversations with Professor Fred Watson
Hi It's Andrew here and as you know Fred Meyer taking a little break at the moment while Fred Swans around the Arctic. We'll be back with the first episode of Space Nets for Twenty Twenty Very soon in the meantime now we thought you might like to take a listen to this episode of the new dark skies conversations. PODCAST is coming soon. It features an interview with Fred. It's a great little background As to who he is and what he does when you've been listening to him for a few years but papal ask a Lotta questions of red and his background so just what does an astronomer at large. Do you'll find out in this interview. And of course you can subscribe to dark skies conversations wherever you get your podcast from so sit back relax and enjoy an interview with Fred On aspects and that's platform and keep an eye out for the dark skies conversations podcast and I'll check you again real soon on space nuts hi with a flick of switch. We turn night today and day tonight. We can change seasons actions and states of mind. Light is everywhere used endlessly and very much part of our modern world. But what is it. How do we use it? And how is it changing our environment and behaviors style field sky used to be our evening's entertainment. Now it's net flicks ipads or even a podcast. When was the last time you looked at the night skies? I'm money okay. And this is doc sky conversations the podcast that brings people and science together to share With me today is a straight his astronomer at large Professor Fred Watson an astronomer science communicator working with the Department of Industry Innovation and science US prior to these outlandish role. Fred was the astronomer in charge of the Anglo Australian telescope at Siding Spring Observatory Australia's largest optical telescope. Fred is known for his award. Winning Books Stargazer the life and Times of the telescope wise Uranus upside down and stock craving so had nineteen years as of interviews on the radio. TV and public appearances and is now heading up some tours around the world with Fred Watson Tours. He's most recently well known freeze podcast series space. Nuts Fred is well loved by the Amateur Astronomical Community but few know of his pioneering work on multi object spectroscopy Oris Fascination for optics and binoculars. He's around knowledge of all things. Light place him. Well my first guest on dark sky conversations. Thanks for joining us for it. Thank you for having made a pleasure to be here. Thank you question has to be asked. What does an astronomer at large actually do hopes? Nobody'll find find out so the job is essentially an outreach education and advocacy role role. It's all about trying to spread the word scientists good for people to let the wider public. Know just what an enormous contribution contribution Australia makes to the world of astronomy and to engage with with the wider community internationally so there is now a lot of international involvement in astronomy with things like the space agency and despite the fact that we Australia now has a strategic partnership with the European Southern Observatory which operates the biggest telescopes in the world on the finest observatory site in the world in northern Chile. Right and so why why is it is it is astronomy moving offshore to Chile for example. A really interesting story and depends on how long you've got. The story. Goes back to the nineteen sixties when astronomers realized that because of the advent of wide body jets and cheap F- F- flight relatively cheap air flights. They could put their telescopes where the conditions were best rather than where the strongest happen to be before that strong observatories we're always in cities. Because that's where I live. So there was a worldwide push to find the very best observing sites in the world In during the nineteen sixty s and that means sites that are dark without light pollution. That's of course a given start with which we might talk a bit more rebel against but also sites which have clear whether a particular sites which are very stable atmospheres a a a low level of atmospheric turbulence and so Sykes were identified. All over. The world. Australia siding Spring Mountain was discovered it to be probably one of the best places to do. Astronomy visible light astronomy Australia. But we now know that some of the other ascites in the world are even better and in particular it turns out that you need a place on a mountain top. Maybe three thousand five hundred meters is kind of twelve thirteen thousand feet on the western seaboard of a continent. That's what you need to get this spectacular atmospheric stability and and the problem is. We don't have that in Australia. We we don't have a mountain. That high on the Western seaboard. I mean we should pay somebody to build one if we could we do that so observatories elsewhere have better sites and that's what's happened. The astronomical infrastructure has concentrated concentrated on those sites principally in the southern hemisphere in northern Chile in Northern Hemisphere. It's principally begawan defer wire which has the best conditions in the world world. And so that's why we engage with with international. So you mentioned there are a couple of times light. The first being that light is moved away from light pollution. So what does that mean to stretch of what is like pollution. And why. Why did you have to move away from it? So many people don't realize that the night sky itself has its own luminosity which comes partly from a AH atoms in the upper atmosphere of the earth relaxing after a hard day in the Sunday. Get excited and they released that radiation after dark. There's also dust in the solar system mm-hmm which lights up the night sky and a very fame background of stars and galaxies. They all contribute to a natural sky brightness so astronomers are always battling thing against that an often what they're doing is studying faint objects whose light is only maybe one percent brighter the this natural background. So they're right down there up against what nature throws at you if you then put in artificial light you lose the signal together. It's as simple as that. So you simply cannot tolerate any artificial light pollution for this kind of groundbreaking research and AH AH. Are there technologies or anything that we can use to try and adapt conditions or is it just simply that we have to have no pollution. Yes it really is. It really is that you can't have light pollution. The problem the problem is astronomers. Look across cross what we call the whole visible wave band so there measurements are made in all colors of light from deep violet and beyond in what we call coli ultraviolet right up the wavelengths scale to red light and far infrared light and far infrared light. Those are. That's what you might say. Covers the the the visible light waves and light. Pollution tends to occupy much of that spectrum for a while there was an enthusiasm among astronomers for what it called low pressure sodium vapor lamps. Yeah street particularly the street lighting getting because they emit light effectively of one single wavelength are in. July's very familiar to people. See You could Aratu Kate so what that's what's doing. He's only polluting that one little bit of the spectrum and the rest of the spectrum is much much clearer but you never get a city or a community community that only has so every wondering outdoor housing lights normally incandescent lights mercury lights all the rest of it. Actually it turns out now so From the Vantage Point Twenty Nineteen that Sodium Vapor Street lights are almost obsolete. And that's for a number of reasons operationally operationally for for for councils and bodies like that that actually operate them. These sodium vapor lights have some disadvantages right. Yeah so I've heard you talk previously about a rainbow of light that you that you can study and you've just mentioned in the band of flight. Could you explain a little bit about the bar. Code of information that you get from from from this rainbow this spectrum of color that you're that astronomers use so. Yeah Ah I mean it's a really fascinating story. Goes back to Newton who a played around with a prison in the sixteen sixty s and discovered that you can shine wide wight light for example sunlight which effectively why even though it looks but yellowish he could pass that light through prison and break it up into this rainbow of colors. uh-huh Red Orange Yellow Green Blue and violet indigo. Isn't there people used to say those indigo as well but it's not really there so the spectrum colors which merge into one another so it's actually a continuum and it was Newton who coined the term spectrum in fact back a little bit later than that in the early eighteen hundreds around eighteen hundred to a scientist by the name of Williston noticed that if he put sunlight through a prism. Did it in a way that allowed you to look at specific wavelengths. Sorry look at specific color. Shouldn't use that. That came later. Williston notice that there were dark lines crossing the spectrum of the Sun and he thought Oh this must be just where these colors join together but ah later in the nineteenth century it was realized that those dark lines actually are the imprints of atoms in the atmosphere of the Sun. Who and the positioning of the lines actually depends on which elements elements are producing them? So what you've got is this array of lines and in the son's case it's it's tens of thousands of them The the early guys could only see a handful but now we recognize there. There are very many of them and each one is the signature of a particular a particular atom elements like Hydrogen Yup. Yep exactly the most. Common Element is hydrogen but we also find iron calcium sodium. All of those things are imprinted on the sun spectrum. So if you use a device vice to to form the spectrum then you can tell with absolute clarity what the sun is made of. So what is the device to ease. It's called a spectrum. Graph actually clean in early days. It was called a spectra scope which is just a something for looking at the word. Scopus Spectrum Spectroscopy. Lets you look at it and the early days when we started the first people who really put spectrum together. We're at the turn of the of the nineteenth nineteenth century so the likes of Williston. Yes that's right. It was actually two German scientists by the name of kickoff onto Bunsen pair of them. They were the guys who really built the first decent spectra scope and they were the people who worked out what was going on in the atmosphere appear the sun and it was actually an Englishman by the name of William Huggins later. Sir William Huggins who tried that technique on the stars ause realized that he could tell what the stars were made of was it. was there a comment that I remember some way that someone said that we would never know what all this that was. A Frenchman by the name of. Auguste comte was a philosopher and in eighteen. Thirty five he wrote in a book no we will never know what the stars are made of. We will never no the densities sizes. We just won't know that temperatures. He said we'll never know these things and actually in that same year. A demonstration took place in Dublin. In fact by a man called Charles Wheat Stone doing more or less the same as it was talking about with Williston but he it was using metal two pieces of metal with the spark passing between them and he realized that if you looked at the spectrum of the spark I told him what metal the electrodes who made of and that was once again building up to this idea kickoff Brunson were slightly later. They were around the eighteen sixties. So comp got it wrong we actually know a lot of stuff about this does go to complete. So what other information does like give us about the universe hard to overestimate what we can learn about the spectrum of objects coming from the universe so not only do you get for example exemplify looking at stars you not only get composition a starts composition. You can also tell whether it's moving towards or away from us and how Fast Austin moving what you did with the radio velocity. That's right that's something called. The radial velocity its its velocity along the line of sight and and so measuring the velocity of a star towards or away from you is pretty straightforward to do the spectrum of a look actually took until the eighteen ninety s before another German called the handle it better fogel time. He was the first guy to measure of raining. So yes you can tell the speeds also you can tell whether an object's rotating you can see that from the spectrum. E can even tell whether it has a magnetic connectic field because a magnetic field actually splits up the spectrum lines Z.. But wait there's because you can use and and this is technology that we really have only we've only had for the last twenty four twenty five years you can use a spectrum graph to see whether a star is moving slightly towards or away from you as it is pulled this way and that by a planet in orbit around. You can't see the planet is too far away to faint but you can see that. This research has allowed us to find exit planet. Exactly what we call exoplanets or extra solar planets and how many have we found. Now it's swell over three thousand the Yes. There is a different method. That's now used to detect them that. The the methods called the Doppler wobble technique the one I just mentioned because the doppler effect another German scientists. This is the effect of the of the wavelength of the light changing slightly by the towards or away from the motion of a star. And but the what happens is if you've got a planet going around to start pulls the star Dr this way and that and the the doppler effect is measurable for the Movement of the story itself. It's a matter of only meters per second for an object. The size is of Jupiter but something the size of the centimeters per second these tiny tiny houses. They're they're not even walking pace. They're very very slow. And yet you can muse light to measure those and so as you're saying I'm realizing how critical technologies with this and how how much information there is that we could about universe but we we're actually impairing these with pollution that's right yes that's correct Having said that all the world's leading observatories and you can these probably half a dozen of them that will be right at the top of the heat there in terms of the the excellence of the sites that they're on they're all protected with legislation to prevent there being undue light pollution and the legislation simply says that if you've got if you've got a development nearby within up to while in in the case of the siding uh-huh Otari in Australia it's up to a hundred kilometers with two hundred kilometers under certain conditions developments within area have to comply with Orwell's observatories all leading. Pretty well yeah. It varies The the major observatories in on the island of La Palma in the Canary Islands. This this grey observatory there in the Northern Hemisphere. The Hawaiian one's the Chilean ones. There are protections which are more or less effective depending on you the local circumstances just like to go back a little bit to talk about spectroscopy again and specifically ask you about your role well in developing multi object spectroscopy. I had never. I know what that is. Please explain an executive order it. Does this marvelous marvelous technique invented by William Huggins effectively the idea of using a spectroscopy for a spectrum graph which records the spectrum originally it was photographic now hold on electrically to workout. What's going on in the heavens? That became very much stock in trade astronomers during the first seventy years of the twentieth century. Words up until the nineteen eighties. It still is but the a big change happened in the early nineteen eighties. Because in the early days you had to meet your observations one star at the time. It was the only way a telescope under spectograph combination could work then in the late one thousand nine hundred seventy s a man with us absolutely delightful name Roger Angell who looked to the heavens German Brit. He works at the University of Arizona Eh. He's retired now. Still one of American astronomer astronomy very favorite strenuous Roger. Angell thought well outside outside the box in terms of how you could use technology to to you know improve astronomy and he got mixed up with fiber optics now fiber optics were until nineteen seventy. Were essentially an entertaining diversion. What what they are is stones of glass very fine strands of what we now use for fines and yes? That's right exactly. It's actually not quite a few silica which is classy. Material material drawn into these fines strands seldom more than a tenth of a millimeter diameter with the hair. It's it's yes that's about twice the width of very very fine. And they have the property that like put light in at one end and it will come out of the the other now they were known back in the nineteen fifties lava lamp lava lamp different ones. And the Yes. That's right all right. Yeah go sorry for my aside. There they were known back in the nineteen fifties these fiber optics but it was only in nineteen seventy that the corning glass works in the United States manage to draw fibers. Because that's how you make them start off with a block of glass and then you melt it and pull it out into these strengths. And they manage to draw fibers with extremely low losses by that. It means that if you put light in at one end most of it comes out the other disruption eruption. Well it's it's attenuation is. The technical is a reduction in the amount of light absorbed by the fiber before that you put light in at one into not tiny dribble came out of the but from nine hundred seventy with these what were called low loss optical fibers that's when they became a potential chill for the communications industry and so Calling it it allows sound and light to pass through it does allow any other it allows. There's light to pass through it. You Can put light in at one end and it will come out the other if you want to transmit sound through it. You've got to turn that sound signal into light clever modulating citing a light source you imprint. A sound wave on through and and that transmit through the fiber comes out the other end. You need decode and you get the sound route. So that's how communications work but astronomers and Roger Angell in particular. He thought well. These things are brilliant because astronomers are always jealously regarding the amount of light that they receive because it is so faint usually we're talking about single photons. Individual particles light so can can we use these newfangled optical fibers and in fact he's first idea was to have many many telescopes smallish telescopes all coupled together with optical fibers. So Oh you gather the light from all these telescopes and bring it back to a single place and you cannot do all the light together on one single object or one single object. That's right but then he turned the idea on its head and realized that with one big telescope which is looking at an area of sky instead of just taking one star or Galaxy Alexey from within that field of view you can actually use these optical fibers to line per fiber on many many objects simultaneously. So let me get this right. We have a field of sky. We have maybe a planet or is that too close. We don't bother with planets looking at enough galaxies and fire off stars and we could have fifteen or twenty items in sky and we could be looking at all of them and getting this barcode information from the stars Civil Tony's because you you can put a fiber on each one and in fact the first one I built actually had thirty nine optical fibers which by the standards of the day were quite quite large means thirty thirty nine objects simultaneously. So what what Roger Angell duty you got a PhD student. By the name of John Hill to work on this build something called Medusa which Medusa head thank you and that had think twenty-five fibers and they tried it out on a telescope in Arizona at the Steward Observatory and it worked. It was a technique that worked really well L. But then astronomers Australia got hold of the idea and in particular an engineer at the Angle Shirley Telescope by the name of Peter Gray. He worked out that you could engineer this thing. In a far more effective way the Medusa I worked with Peter. He was working with the anglo-australian telescope. I worked with a small telescope telescope called the United Kingdom Schmidt telescope which has a very wide field of view and together we produced a kind of workable optical tickle fiber systems for these two telescopes which kind of took the lead in the world on this science. Could you tell us the names of these. Well Peter Peterbilt you built the. What was it called fiber optic coupler psychot- remember the name but it turned into fo cap that was the acronym I built? Something called the fiber linked array imagery for matter which was flare then flare worse built in the early nineteen eighties. It was the first multi-fibre telescope spectroscopy system that coupled telescope to a spectrum graph which was actually stationary in the dome. Now that sounds weird an esoteric but what it meant was the spectrum of which is a very delicate piece of equipment was not riding around on the back of the telescope. It was fixed on the floor and was incredibly stable. And that's so we were the first to do that. So flair was the pioneer. Then I built a second version. Because flair had certain inadequacies the second one was the panoramic area coverage with higher efficiency. which was panache panache? A Well what clearly came next finesse. Until one of my colleagues said Venus stands for fails to interest nearly everyone saves spectrograph engineers engineers well. She called it flat to then evolved to a robotic system with more boring name of sixty F- with one one hundred fifty fibers that was commissioned in two thousand one and now a building an amazing machine called Taipan which uses things called starbucks so each optical fiber sixty had robot a single robot move the fibers around but with Taipan h fiber dopey. Three hundred in the end has its own micro robot round meanwhile anglo-australian telescope back in one thousand nine hundred ninety six built something called to death to the F. stands for two degree field. That's the amount of sky the thing sees in two F. Four hundred fibers but after tell you the aero which now stands for Australian astronomical optics used to be the Australian Astronomical Observatory. Hey always building. A system with more than four hundred fibers for telescope in Europe a European European telescope straight cuts way up doesn't it. It really does punch above its weight with regards to -nology develops right. That's why Australian astronomers Jonas have had such an given where small country because we have this equipment that we build it probably more effectively than anywhere else Somebody said we should call ourselves. Fibers are us. Because that's what we do. We do optical fibers the tech. The technique technique is in use around the world but many of the ones that are used elsewhere ones that have been built started struggling anticipate so just keeping bring on technology. Same here I heard Margaret Atwood before papal. She's the person that wrote. The Maidens Tail Modem Handmaiden handmaidens and. She comment was that old. Technologies have got good use a bad use and stupid. I use that we never considered and just thinking about lights and particularly with astronomy. What would you think the good the bad and the stupid well look for optical astronomy that's visible light astronomy not now talking about radio astronomers rexroad strong because these these are all different disciplines? Although we're all looking at the same things in a different way and often those results all piece together optical astronomers and and they're talking trades light so they are obsessed with light a more especially obsessed with with actually getting the very the best information from lies so the good is what we learn from from the from from the sky by Sifting light through the spectrum and other types of interest yep yep the baddies light pollution. So that's when light. which is it's been used for completely innocent purpose but gets out of hand in particularly in the light plumes of cities and and really goes back to the early twentieth century when councils putting lights with really no regard to what that was doing tonight sky because we simply simply never thought about it was becoming a problem by the time of the Second World War? It's really interesting. Is that in Los Angeles which is very next very very near the Mount Wilson Observatory in fact exceed Los Angeles from Mount Wilson. Where at the time? The biggest telescope in the world was during the second world. War centuries had had blackouts in order to to mitigate the possibility of invasion and during that time huge astronomical discoveries as were made because the the night sky koby seeing properly from moments again So it was inadvertent. So that's the bad side just on that I. I've attended some conferences in the U. K.. And one of the issues that they have when they talk about. Trying to mitigate light pollution the K.. Is that if you start talking to pay pooped in that sort of generation of about turning of streetlights and they feel like it's taking them back to that so I just like the blackout out to do that in blackout. Yes or no. I remember people saying that's true but it's not a blackout. I mean what we're talking about now is good lighting eh because this been huge progress in the last twenty years with understanding the ills of light pollution and not just for astronomers where the where the least least important in many ways of of the consequences of Bob Lighting. I again when I talk to groups about pollution. I often or haven't often and but I have been asked by people worldwide. Do we have to keep the lights down for the astronomers. When you've got a whole heaven stars you know? Why can't they study the start of the left or the brightest star or whatever and I think in some ways we lost that argument where we talked thirty years ago when when the International Dark Sky Association started and it was astronomers saying are we losing our night sky that that story was lost on the general public? I didn't understand the information that you're getting about heaven. That's probably true thing I'm most people think an astronomer is middle age bald man with a white coat. Who's got a long spindly telescope? And just spend his nights looking through uh-huh nothing could be further from the truth. It's all about you know. Well directed a scientific problems. We're trying to understand the universe because that understanding my actually actually turn out to be really useful to us one day and it's it's conducted in a very very progressive ways. Not just looking mistake. The sake of looking were studying and of course. The great thing is that it's no longer and more pulled middle aged man we we are. How far more diverse? So that's the good in a bed. Yeah stupid stupid. Use of technology that maybes. He's come through astronomy through light and and I know of things you talked about. Doppler effect isn't so I actually almost Lump the fiber optics work that I was talking about into their it certainly quirky. Because in you know I in one thousand nine hundred seventy. Nobody had thaw in this direction. It was Roger Angell towards the end of the nineteen seventies. We're thinking outside the box or this to what you could use these technologies for and I do remember number when I started working on this in one thousand. Nine hundred to building flared the first fiber optic system for the Schmidt Telescope. One of my colleagues. Call it what sins folly because nobody believed that it would do anything useful when it would just it was just be. Quirky is like is a bit like back in the postwar period the the then director of the Mount Strong Observatory which was Australia's Australia National Observatory at that time amounts from knowing camera the Commonwealth Observatory Sir. Richard Woolley. Somebody said to him. So why do you think radio astronomy will. We'll now ten years time he said forgotten and I think people thought that about the fiber optics. Where do you think fiber optic million ten years time forgotten? It's not going to be used on. The biggest telescope is already being used on the biggest telescopes in the world. It is absolutely revolutionized the science because what it lets she do as I said we didn't carry through the conversation that lets you look at many objects at a time. Four hundred eighty four thousand on the on the Vista Telescope which is in Chile operated by the Europeans that then allows you to gather enormous data sets of the most intimate statistics of stars and galaxies and quasars all these objects in the in the wider universe. And by doing that you can first of all you can. New Population Census Studies. You can look at the trends. You can start discovering a lot about the evolution of the universe. It's how we know for example old the the the Big Bang model of the origin of the universe how that is almost certainly the the the correct model because we can see its imprint. All over all over the millions of galaxies that we now have three dimensional positions for thanks to the fiber optic technique so it's kind of revolutionized that study but he also shows up the real oddballs. Tell if you're looking at you know four thousand stars at a time. You're going to find things that are very very unusual. And they're the ones that point the way to things like new physics the the understanding that relativity and quantum theory might not be all that there is these. Are Things things that we know the best models of reality we've got that we still but we still find gaps in the what we're looking for is what might be hidden hidden underneath which could lead to all kinds of things like teleportation travel all US grace and it actually leads me into the other question ahead. His real basic one but what is the speed of light. The speed of light is talking about Einstein's we know from him so yes. Is that going back to nine. Thousand Nine hundred five when Arnstein published his special theory of relativity which these who got words. But that's a theory of the way objects move and it sort of built on what Newton wrote in sixteen eighty seven in his book. Doc Principia the PRINCIPIA. He wrote his laws of motion. which which fine and work well until you get near the speed of light? The speed of light was already the well known at that time. Three hundred thousand kilometers per second. How by actually? It was first measured by a Danish astronomer in sixteen eighty seven by looking at the moons of Jupiter a man called Roma he Worked I think he'd Copenhagen studied the moons of Jupiter and realize is the way they behaved as he could see them in. The Sky meant that there was a time lag in the travel. Time of the light from the backside of Jupiter due to the front side of Jupiter analyzed. All that cracking good answer for the for the speed of light is actually French. Physicists in the late nineteenth century really kind of tidy down but what was curious and this is what fed into on Stein's thinking was that everybody expected expected. The speed of light would be something variable so that if you think about the speed of sound earth the speed the sound is carried through and if you're on a moving object like a car and the speed of sound changes for you because it's your station when you have a cargo past you can hear. Well that's the doppler effect. That's going back to what we're talking about earlier but the everybody everybody expected that if you if you say if you were looking at a source of light and that light is reaching you at three hundred thousand kilometers per second if if you're stationary yeah that's fine but the thinking was if in fact you're moving towards that light at one hundred thousand kilometers per second then then you should see speed as being less than or more than what it actually was. It turns out that the speed of light is. He's fixed in a vacuum. Does not how you moving. How the light source is moving? It is always three hundred thousand kilometers per second and one went. Once he realized is that was actually confirmed. By two Americans Mickelson Morley in the eighteen eighty S. The speed of light is in variant and announced. I'm I'm fed into his work and realized that actually the speed of light is almost mystical. It's it because space can vary space can change shape it depending on your motion and time can change depending on your motion but the speed of light doesn't is the is the thing that's constant absolutely constant. Yeah there is. There is a group of small group of scientists. One of whom is based here in Australia. John Webb who's Nelia Leo was somewhere else in the world. Which is why it's called the worldwide web? John Webb is a he believes he has evidence that the speed of light was different in the early universe Looking back thirty point five thirty point six billion years the beginning of the universe was thirteen. Point eight billion years ago to the best of our knowledge and he looks back nearly all that way and thinks he can see evidence that the speed of light has changed. It's a very speculative result nominee. Astronomers believe in but John Webb is convinced without from the University of New South Wales. We'll keep an interesting an eye on that. To see how it progresses. Yeah so when. When was the last time you looked at the night sky last night? Did you look to the stars. And so yeah. There's a bit of cirrus around. It's as long a brilliant night. Yeah look the best time you looked at what. What's the most memorable experience you've had in the nighttime environment? It's because my a life has been in astronomy and it goes back a long way. There are many many That I could that I could talk about one of them was in the mid to early. Two thousand two thousand six two thousand seven late in two thousand and six a colleague of Mine Robert macnaughton in siding spring discovered a comet. That was his job. He discovered comets but This one turned out to be incredibly bright and in the early months of two thousand seven it was just dazzling in a in western evening sky. Not where I lived at that time was totally crews are particular does. Yeah not all of them do some some go around the Sun Many of them are in orbit around the Sun but comics actually come from the depths of the solar system. In fact almost halfway to the next nearest star there's Sort of shallow of these icy objects called the ORT cloud named after a man called Yan art who was a Dutch stronger. In the Mid Twentieth Century must be a cloud of icy objects out there which fall inwards towards the solar system and when they get near the Sun the ice evaporates and they become luminous right. Yeah he was. That's right and that's how we that's how we know about comets but comment one of these. That came out of the Blue Egg. Robert detected it when it was quite faint but it turned out to be probably the most spectacular comet of the century so far it may be the most spectacular for the whole century. It was just so that's one but I I always have very fond memory of a night light. which would have been in the early nineteen eighty s and it was when I was building? The first of these fiber optic systems the flare thing that I mentioned that was a device that as I said used optical fibers to pick the light of stars from the focus of the telescope and brought them the fibers brought them out of the telescope to a basically a little thing that just line them all up in a straight line now we straight line was about half an inch long thirty millimeters or something AH thirty nine optical fibers in it each of them a about a tenth of meter in diameter and it was a crystal clear Leeann. I and I got the telescope all set up until this was right at the beginning of these experiments and I picked up this little fiber AIBA unit from the floor which I knew had the light of stars coming down in the end and I just saw a line of little lights. It'll all different colors because stars are different colors. Color is dependent on the temperature and it was magical. These are standing there withholding style in my hand with with these these. These thirty nine five lit up shining away and it was the real reason why it was. A buzz is because actually quite hard to get light down fibers become very very precisely at that point. I knew I could do it. And I knew the instrument was going to work. Did mazing so just to finish shop like to ask you if you had your soapbox and three minutes if time what do you want people to know about light and light pollution Russian. Okay so this is where I become. Well an advocate. It's not quite activists activism. It's very gentle activist. uh-huh why do we want moderate change. When do we want it in due course? So that's my soap box and what I would tell people will is that he asked them to think about whether light is going. Light basically goes on forever. I mean it does the dwindling away to very faint levels but if you're sending a beam of light upwards into the sky what am I going to do is going to light up the molecules of the atmosphere via and spoil that view of the sky for somebody else. And it's a death by a thousand cuts so individually our contribution to light pollution is very low but collectively when you've got a city like Sydney with more than four million people living there. Nobody thinks about where the light is going. Then you've got a city in which it is impossible to see the stars house so it's just to think about lighting up only what you want to light up. Keep the light below the horizontal plane. So none of it's going going up into the sky and there's a subtlety here. We now know that like that is rich in blue and that's really Dazzling white light that we getting used bright white light emission dial diodes light-emitting diodes. Led that light we now know is not good for human health at night because it fools circadian rhythms into thinking. It's still daylight screws up everything so think about Light Posi answer. Thanks for you time to great pleasure. Anytime thank you. Well that's it docks guy conversations this week. We hope you enjoyed it. We'd love to hear feedback thoughts. Were if you've got any questions about lot. Pollution suspended the name out. PODCAST DOC. Sky Travel Dot Com. Today you or Instagram's is to grandma's at least subscribe to our podcast at I tunes Stitcher spotify or wherever you get your podcast from. And why are they give us a reviewed. Thanks again for me this week until next week Matz Out uh-huh.