TechStuff Classic: How Planetariums Work

it's out of this world. Let's take a listen. So there are a lot of different types of planetariums that all use a very similar approach, but you know, the actual implementation can differ between one and the other. But we wanted to talk more about all of the kind of history that built into coming up to the planetariums as well as how they actually work. Right. We didn't I just explain it's a projector and then go in

from there. I mean, because because y'all basically it's a projector. Yea, So we could just say it's a projector, and if you know how a projector, it's a Friday, so we're ready to go home. But no, we wanted to actually talk about the history of planetariums because it's a fascinating story. I mean, obviously, as as a species, humans have been fascinated with the heavens since before recorded history. I mean, this is something that we've obviously been really amazed by

over thousands of years. It's pretty amazing. And what's interesting is that there have been lots of different attempts to create a an indoor version of this experience, because it's not always convenient to go outside and do all your your work. And based upon thousands of years of observations, we've got pretty good at figuring out how to represent the night sky in a way that was accurate even the movement of things like planets in the moon and

the sun and Earth itself. Yeah, I mean it took us a while to figure that part out, that the Earth itself was moving and not say everything else was moving around the Earth. And depending upon whom you are, you might still argue that thinking of a specific documentary that Jane Way was the voice for anyway, So assuming you're not having this geocentric view, even even that would allow you to see that the the heavens move in a very predictable way. It may take a long time

for a particular cycle to happen. But once you know what those cycles are, you could predict make observations that would end up either verifying or or negating the previous guesswork and eventually make it into a science. So why our planetariums themselves awesome? Well, for one, you get to look at the stars, even if again you are in a place where you can't normally see them, like here in Atlanta, we get a lot of what's called light pollution.

So that's just you know, any major city tends to have this where you've got lots of lights that are on at night, and that tends to drown out some of the stars. You can't see the fainter ones. You really only see the brightest ones that are in the sky. Uh. You know, you might be able to see things like Venus, which are that's that's extremely bright, and you might see some of the major stars and some of the major constellations,

but you're missing out on a lot. Oh certainly, so unless you go way out into the middle of nowhere where there aren't so many lights, or you have to live someplace that has really strict rules about the lights at night. Because there are a few of those places you probably can't see that many and even in those places it sometimes rains or gets cloudy. That turns out

clouds really inhibit the stargazing activities. Also, the sky over the Southern Hemisphere is different than that over the Northern Hemisphere. So um, if if you don't travel back and forth pretty frequently between the two, yeah, you don't know. If don't cross the line over at the equator and shout out to all my navy buddies who do. Um, if you don't do that frequently, yeah, you don't. You miss out on the way the sky looks and in the Southern Hemisphere or if you live in the Southern Hemisphere

the Northern hemisphere. So to our new deal and listeners, there's a lot of you. There's actually quite a few of you. Um, I will not confuse you with the Australian listeners. We love all of you equally. So if you've never been there, but you want to see what the sky looks like, a planetarium, some of them anyway can accommodate you. A lot of them have the capability of showing the stars over any particular point on Earth

like that's how sophisticated they've become so. Not only that, but they many of them can also show you what the sky would look like on any given date, So you might say, well, what did the sky look like yesterday, What will it look like tomorrow? What will it look like in a century? What will it look like a hundred centuries from now? What did it look like back in the day that Shakespeare wrote his plays? Like, you could do any of those things, and by plugging in

some some numbers. The computers that handle the calculations for most of these uh devices, not all of them, some of them are a little older, but most of them can take that into consideration and actually determine what the position of the planets would be on any given date, the stars, etcetera. Which is pretty awesome. Yeah. Um. They can also be used to teach celestial navigation, and they certainly were used for that purpose during World War Two.

Very useful, especially if you can't always depend upon instruments to be able to get around. Also, uh, hey, uh it teaches astronomy, which you know, I always almost left that out of the notes, and I was like, yeah, that's uh, that's a big deal. I guess that's a thing. Yeah, so obviously the astronomers out there if you want to be able to identify various star clusters things like that. And a lot of these have special um projectors that show things like the Milky Way galaxy or other nebula

or things like that. And that's important. Oh sure, sure, but we will get into that later on. Um, let's talk for right now about the history of these devices, because people have been painting the sky on ceilings, I mean, for for basically ever. Yeah, I mean, like I got a cousin who has the Glow in the Dark ones that's been on her her bedroom ceiling like since she

was like four. So yeah. Also, there's a star map on the ceiling of the tomb of the Egyptian official Sentement that dates from like that does predate my cousin, so a little bit. Your your argument is valid. Yeah, I mean this is something, like I said, humans have been fascinated with the stars for as long as we've been looking around and being able to express our thoughts.

So it's no surprise that we're seeing evidence of that in in prehistoric and and uh, you know, just post historic, fairly historic uh you know, drawings and and uh and depictions on things like this tomb. And then we have some early examples of what could be something like a planetarium from the Arabic world. Right right there, there were Arabic tents made with holes in the fabric to let outside lights shine through, representing each star or each star

as they knew them in in that time. UM described in European History Circle that twelve hundreds or so, and so that's that's you know, that's a good while back, right and then we had, uh, let's let's switch up to say, oh, I don't know, let's let's go to

the idea of using globes and sky maps. This is really cool too, So starting a couple of thousand years ago, it became really popular in the West to draw sky maps on globes and um the first planetariums known to history were huge versions of these, like big enough for people to sit in. A really famous example is the gor Top globe, supposedly based on plans found among Tico Brahe's papers. Okay, so wait, wait, wait, Tico Brian, I've always heard Tycho Bray. Where did you hear Tico Brian?

I'm one of my astronomy professors in college called him Tico. That's good enough for me. So, I know, I know that the Penny Arcade dude calls himself tycho, but hey, we're going with an astronomy professor's approach. I'm I'm all right with bowing to authority on this one. He had a really impressive beard. So that also, I mean, that's like credentials in the astronomy world. So that's totally cool.

So that that was that was built in the mid sixteen hundreds and what's now Germany, and it was large enough for like twelve people to sit in on these circular benches that were around a table um where refreshments could be served. Obviously, yeah, um so so the so the object, this globe was about ten feet or three meters in diameter, and the stars in it were these gilded, spangled fixtures in the inside surface of the globe that we're eliminated by a lamp that would sit on the

table along with your you know, snacky cakes. Interesting. So it's like it's like if you look at a regular globe, you know, that's something that we look at on the outside service obviously that's you know, representing the Earth. But this is one where we would go on the inside and we're looking at the inner wall, which is representing the heavens, the heavens right right, and the outside of it was actually painted like like the Earth. It had

all of the continents and everything on it. Pretty cool that whole globe shell could could rotate around the viewers thanks to some water powered machinery. And it took some ten years to build and weighs like three tons, despite which it was moved to St. Petersburg as a gift to Peter the Great in seventeen seventeen. Shortly after that it was partially destroyed in a fire, then restored, then stolen by the Germans in World War Two, found by

US troops, and restored again to St. Petersburg. Pretty sure, that should be an Indiana Jones plot, right, it's great, And this thing weighs three tons. It takes some determination to steal anything that weighs three tons. That's pretty incredible.

But so the practice of making these these enterable sky globes like this unwieldy as they were persisted into the nineteen hundreds, and the Museum of the Chicago Academy of Sciences built their atwood globe as late as nineteen um and that's that's about the same size a little bigger at measure sixteen feet that's about five meters in diameter um and shows six stars plus the planets in our Solar system as as holes through which outside light can shine.

It's electric and the shell can spin once every eight minutes around viewers. Interesting, and so this is kind of it's it's like it's taking a note back from those old Arabic tents, right, the lights coming from outside shining through holes, and that's what represents the stars, very much like those tents that had the holes pin break through

the tent canvas right right. You know, of course this depends on either in this case probably electric lights outside or in the case of those tents, having a good source of sun light in order to see what's going on. Um. By the way, a couple of distinctions that I wanted to make here. If you've ever heard of an order e um, that's that's a physical model of the planets in our Solar system and sometimes also called a planetarium,

and they're also sometimes included in planetariums. So that's nice and confusing, right, So orris are if you've ever seen one of those physical models where you've got the Sun in the center, and then you have all the different planets that can spin around the Sun. Sometimes they are actually mounted on gears or motors so that it represents the accurate movement of each of these bodies as they

would move in relation to one another. So for example, the Earth's uh, the Earth's movement around the Sun is different from Saint Mars, which is different from Neptune or Saturn. Anyway, you would be able to watch these and see how they move in relation to each other, see the times when they happen to align, when they get out of alignment, and it's really fascinating to see an or but it's from an outside perspective. You're not looking from the inside out.

You're looking as if you were able to distance yourself all the way out of the Solar system and look in on it, right and and being that especially early ones, where we're you know, the planets were all on their little rods and would all be going on a on a single plane around the Sun, rather than in the truth three dimensions in which right right, it would be it would be as if we had a completely flat solar system, which is not exactly true. Yeah, it's like

Star Trek world. Everything just comes right knows up to each other. Yeah. And also they would move in and essentially perfect circles. They wouldn't have these kind of elliptical orbitals because that's really hard to do with physical rods. But you know, my favorite or y of all time is from the movie The Dark Crystal, and it's what Augra had. Now that of course was an or y for a fictional solar system, but was amazing that an

enormous things spinning around all over the place. That that lady still creeps me out as an incredible movie that everyone should go see. Uh oh, absolutely, yes, very much so. Plexis I can't okay science besides planetariums and uh and or planetaria if we want to talk about or reason in that sense, and these globes, we also have the concept of keeping track of astronomical phenomena in other ways

that aren't again all immersive. All right, Well, part of the function of a planetarium is as an astronomical clock, right, like you were saying earlier, being able to to go into the future, into the past and see what the stars looked like at any given point. Um, and you and Joe talked about a really famous one Antiquathera device or Antiquithera mechanism, which is a some people would call the oldest computer and analog computer. And yeah, on Forward

Thinking we did a podcast. No I think I think you did it on tech Stuff. It was well days, that's right, that's right. See here's the things that I do. Too many shows for too many different different versions. Yes, we did do the tech Stuff one so as a re minder, because obviously I need one. Uh. The Anticathera device was this, uh, this gadget that had been lost in a shipwreck and recovered by sponge divers, and it

was recovered in very poor repair. It was all these different pieces and some of them were big chunks and some were smaller pieces. Uh. And eventually it took decades to do this, but eventually we figured out that this

was an astronomical computer. It was able to show where the position of the planets were in relation to the Earth on any given date, including the position and phase of the Moon and the position of the Sun. And you would turn a crank in order to adjust the dials so that you could change it to any date and see what what the that actual alignment happened to

be on that given date. It was also very useful for things like planning out specific events, because you could do this and find out when there was going to be an eclipse, for example, and an eclipse tended to be considered a bad men, so you might think, hey, this big festival, we want to have what happened to fall on in the eclipse, So we're going to have a special a special festival that's going to be three weeks earlier so that we don't have to worry about that,

or an Olympics event that there would be another example, So it's really super cool. However, again this was something that was relatively small. We're talking about like the size of a large book, and so you're looking at at these dials rather than again being immersed in the experience. But it was really useful for checking out, you know, what a a a planetary alignment would be on any given date, because again they understood that the movements of

the planets were regular and cyclical. Yeah, and so they were able to do this, and I don't want to minimize how difficult this was. They had to build exact gear ratios to represent the movement of all these planets and sometimes hand machining those yeah, yeah, yeah, and dorble amount of precision is required and sometimes you know, you would have to have things move backwards a little bit and then move forwards because from our perspective, that's the

way things seem to be moving. So really really complicated stuff. Uh but still again, that's that's not quite an astronomical clock. It's very similar to one. Once we looked at actual astronomical clocks. Those look like clocks, but they happen to have either a dial or sometimes it's a uh, you know, a little physical representation of what the planetary alignments are going to be or those phase of the moon or whatever.

These have been popular since the Middle Ages. There were also some of those posh sky globes that could hypothetically predict the movement of celestial bodies, and Archimedes is said to have had one background two right, so uh, probably true lost stuff about that time period. Difficult for us to verify, but but I'm willing to believe it because they are wicked smart. So uh yeah, yeah, again, we're still talking about stuff that lets you look at it.

It doesn't surround you like the crazy um the globes where you would walk inside and take a seat. But that's what leads us to the more modern day planetarium that would require projection and not not like standing in the middle and projecting out by speaking more loudly. We're talking about light projection here. Okay, we've got some some planetarium talk ahead of us, but uh says here on my clock that it's time for us to take a

quick break and we'll be right back. Okay, So projectors planetarium, all right. The first one was installed in a roof on a rooftop in Jenna, Germany. And I apologize, I suppose it would it be Jenna, Germany? The j is generally pronounced like a y. I did well, Jacob would be a cub Johan. I, I see where you're going, and I approve. I'm guessing it's Jenna. Any of our German listeners who would like to to reprimand me on my pronunciation feel free, because um, I should know better

at this point. But it was an optical projector, so it actually used light and lenses to project images of stars on a curved surface the inside of a dome. Yeah, so this dates all the way back to nineteen thirteen for the earliest of the plans. That's when a man named Oscar von Miller commissioned the device for the Deutschet Museum in Mind. So the idea to actually use projection

was agreed upon in nineteen fourteen. There was this big meeting and generally speaking, most people credit and engineer by the name of Walter Bausfeld who came up with this idea to use a projector. He was working with the company, a company called Carl Zeiss, which was an optics company still is in fact, is that that's very true? Uh, And they decided that they would use this kind of approach. They decided that they wanted to use something that was fairly new, the idea of a new source of light

for people at that time. Well, their their original idea here was was to use those fancy newfangled light bulbs as instead of a pin prick, instead of having a pin hole for for each light source, they wanted to use a light bulb for each star. And they very quickly realized how complex and expensive and terrifying that would be, especially if you want to be able to move your field of vision right right. So if you had all

these stars in fixed positions on the dome. How do you move them if you want to if you want to move the entire ceiling and that's oh, that's not good. Can you imagine the heat generated from those old bulbs to all of those things. So this this one engineer, Vaulter Uh supposedly said, hey, why don't we put the light in the middle and then shine it out on the on the on the inside, as opposed to poking holes on the inside and putting these light bulbs through.

And people said, you're crazy, except for another engineer, and this one. This is a very interesting and tragic story. There's actually a really good documentary that we'll talk about. But there's an engineer, a scientist, an engineer named Rudolph Straubel who expanded upon Bauersfeld's suggestion. He actually said, wait,

this is a great idea. We can use a projector, and not only can the projector show things like the the position of planets, which was that that was kind of the initial approach was, well, we can show the planets this way, So no, we can actually show the stars this way too. We don't have to just rely on this as being a way of showing the planets,

and they all began to work on this. Now, Strawble would eventually leave the museum and this his position working on this project because he refused to divorce his Jewish wife. So this was the rise of the Nazis in Germany

at the time. And UM there's a documentary called Planetarium that really follows this, and the the general perspective on Planetarium is that straw was actually a major contributor to UH, to this first planetarium, but his work was all but erased by the Nazis, and then the Nazis attempts to erase it were then subsequently erased, partly because the the company, the Zeiss Company, got split into two companies after World

War Two. Half of it was in the East Germany, the other half in West Germany, and too for the West Germany side to UH to talk about Strawble would have also been to admit that they had bowed to the Nazis UH demands, and so it was not politically UH, let's see, what's the rightway prudent. It was not prudent at that at that juncture, so to speak, to make that admission. So if you're really interested to hear more about the uh, the drama behind that and also the

truly the tragedy behind that story. Check out the documentary Planetarium at Anyway, getting back to the planetarium itself, it took year of research and development before construction could begin, right. Also they were there was a war from from uh, yeah, there was World War one, yeah, and then and then the nineteen fourteen nine eighteen yeah, so that we had World War one going, so that that puts things on hold.

Construction will begin in nineteen nineteen. It wouldn't be completed until nineteen twenty three and was first shown on a rooftop in Jena, Germany, and then would eventually move to its permanent home in the Deutsche Museum in nine and

this had what was called a star ball. A star ball this is this is a perforated sphere that that powerful light can be shown through up onto the dome like like we've been talking about um by By around a decade later, domes like this would be installed in museums around the world, especially after affordability improvements were made to the Zeis device by Armand's fits in nineteen six. He was then the director of the Franklin Institute in Philadelphi.

You and he His innovation was to um to scale it down from from a starball to a star dottecahedron. Ah yeah, okay, that makes sense. You get a lot more flat surfaces. Flat surfaces, it's easier to machine in those days. The machining a sphere is not easy. No, no, Um. It was actually suggested to him by Einstein. The story

goes way to go Einstein. All right, So yeah, Um, circ of the nineteen sixties, lenses would come and to use to amplify the appearance of brighter stars to make a more realistic starfield, and more expensive machines around the same time, multiple projectors, each with their own star plates. Um would let you use lights of different brightnesses to

project different magnitudes of stars. Gotcha. So yeah, it gets a little tricky, like how do you represent the stars accurately because some, of course when you look up in the sky, are much brighter than others. And there's only so much you can do with with machining different different apertures of pin pricks, right right, So yeah, it was pretty complicated stuff. So how do they work today? Well, if you were to go to the one in the

Deutsche museum. It's been updated several times over the course of its history, so it's not the same device that was installed back. It's had some eight million visitors or more over the intervening years. And now they use a projector that has thirty two different slides to create the images of stars and planets on the curved surface of the walls and ceiling. Now these slides have a fine pattern of holes that correspond to the actual position of

stars in the night sky above Germany. It's specific to that. Yeah, I mean it would be weird for them to have a representation of the sky above somewhere else. I mean, this is this is, you know, above where the facility is. Each slide is a pair of glass panes, you know, like a slide you know, the jubilender a microscope or something. Between these pines there's a thin layer of copper and

they punch holes in the copper. Now, the size of the whole determines how bright the star is going to be, right, So if you make a tiny hole, it's going to be a relatively faint star. If you make a larger hole, it's gonna be a brighter star. The lenses you used to help focus that light so that it's the right size, so you've got the right brightness and size. Yep. Yeah, you don't want to have just this kind of fuzzy

blurry effect. Uh. So generally speaking, you got a lamp that's what's providing the back light, and you have special projectors for the sun, Moon, the planets, and the Milky Way to complete the picture. So this is a multi projector set up. Now, the original structure relied on gears to turn the projectors precisely to mimic celestial movements, so you would actually have someone manually turning something. We have

sense upgraded now it's electric motors that do this. Uh. And again you have the gear ratios worked out so that they mimic the actual movements. So uh, you know, you could just have everything turning, but of course that wouldn't be accurate to what we actually see in nature. You have to be a little more specific so that you know when Mars is going past your vision, it's doing so at the right speed relative to the other

other sites in the sky. So the neat thing about this is that you can actually obviously speed things up or slow things down. So you could sit there and say, all right, here's what the path of Mars looks like over the course of a month, and you could show it in in uh sped up time, so you don't actually have to sit there for a month to see it happen, right, Or you can reverse it so that you can say, here's what Mars did last month, right,

And then of course that sets time backward. And then, because we learned that from Superman, right, if you spend the world backwards, then obviously time reverses. It's okay, they all have way back machines in turns, right, so they all everything works out in the end. By the time you leave, everything's right back to where was, so you don't have to mess with your watch. That's that's really smart. Now about six of all planetariums still use projectors like this.

I get this particular figure from the planetarium in Hilo, white E, a lovely place to visit, by the way, So they use standard video special mechanical projectors to create those images of the night sky. But beginning in the nineteen eighties, some planetariums began to experiment with going digital rather than analog. It wouldn't be until the nineteen nineties that planetariums could actually experiment with full dome animated content. Uh now, full dome animated content. This is used for

lots of stuff. It's not just used for planetariums. For example, there are virtual environments that use domes to represent things like say the sky for a a jet simulator. So these domes allow you to have this amazing field of view that you can then project some sort of virtual environment on, and that's more effective than say being in a flat room with corners and flat surfaces. That doesn't

usually convey as realistic and experience. So for planetariums it's great because it can mimic the night sky very well. Uh Now, this this full dome approach meant that you could have some really cool effects, but it also comes with some challenges. It's not uh always easy to do. If you're using a multiprojector approach, for example, you have to make sure that all of the edges are going to line up with each other so that you don't

have any kind of wackiness in between, right exactly. Let's so, let's say that you have a projector that is a certain like if you look at the dome as kind of a a pie. So you think of a slice of that pie. One projector is responsible for that slice, the next projector is responsible for the slice next to that. If those two projectors are out of alignment, then you're gonna have some stars that are overlapping each other. And

then you have this additive property of light. You know, you have light from two different sources hitting the same physical space, and it's gonna be blurry, it's gonna be too bright, it's not going to represent the actual stars. So this is something that has to be very carefully calibrated every single time any maintenance is done on it. So this is true for all planetariums. It's not just for the ones that are multiprojector, but multi projector in particular.

You have to make these considerations. Yeah, they generally still call it a star ball. By the way, this kind of a spherical construction into which all of these projectors are are sat is still called a star ball. I think starball is a really great word. Starball just I mean, it sounds like something out of Cartamari Domonty to me, which I think is why I'm so fond of it. I was I was thinking it sounds like a like like a John Carpenter movie, but maybe I'm thinking Starman.

We've got more about how planetariums work, but before we get to that, let's take another quick break. So if you wanna have a planetarium, one of the concerns you have is that you wanted to be really dark. You don't want to have any kind of other light bleeding into it because that's going to interrupt the actual view that you want. Um Also, you know, you could go with a single projector, which would be at the center of the planetarium, so you've got a injector that's right

in the very middle. Now, one thing that you have to keep in mind, there's a drawback there. You can't stand in the middle because that's where the actual projector is. These things, by the way, cost lots of money, you know, sometimes hundreds of thousands of dollars. So generally speaking, if you're in a planetarium that has a single projector, there tends to be like railings and things like that so that you can't get too close and mess with it.

I remember standing right next to one for a commercial for a science fiction convention back when I was thirteen years old, and I would never been more terrified in my life that I was going to end up bankrupting my parents by by accidentally falling against this planetarium projector. But yeah, it's it's uh, it's it's usually blocked off. It takes up that center space. So one thing you've got to keep in mind is that takes up potential

place for people to sit. However, sitting in the center of a planetarium is rarely the best seat, so usually you just you just make use of the outer edge as much as you possibly can. But with that center single projector, you also don't have to worry about bleeding into other projectors. Assuming you've got one that's the master projector that handles everything including the planets, the Sun, the moon,

all that stuff, you're good to go. You don't have to worry about that those other issues of are these things perfectly aligned, because everything should be fine assuming that the projector itself is in good working order. The multi projector set ups that that that I was talking about a second ago are are in those starballs. But I but it sounds like Jonathan, you're talking about a a different kind of projector set up. Yeah, there's actually there

are different ways you can do this. You can have the multiprojector all in the center, which is similar to that single projector I was just talking about, which may or may not have multiple lenses on it. In fact, it usually does have multiple lenses on it, so it can look a lot like the multi projector set up. But there are other multi projector setups where it leaves

the center completely clear. And the way they do that is they set the projectors up along the inside perimeter of this dome and they use mirrors to reflect the lie from the projectors so that it hits the precise spots on the inside of the dome, so you get that starry night appearance. So yeah, you know, they're multiple.

The nice thing is is that once you know the actual movement of the celestial bodies and you're able to represent them accurately, there are multiple ways to actually achieve that. And that's the cool thing is that we've seen lots of different approaches to this particular problem and all of them work. They just work in different ways, which is pretty awesome. It just shows the ingenuity of people when it comes to I want to represent this thing that's

in nature, how do I do that? And people come up with completely different ideas that all work the uh you know, equally well, just in different ways. So we actually have we have a couple of planetariums here in Atlanta that uh you know. I think fern Bank has one, but Emory also has one, and uh, Emory's is interesting

for a couple of different reasons. One is that it h it's a classroom as well as a planetarium, so it can actually double up, and in fact, the planetarium stuff can fade off into the background so that it can just be a regular schoolroom. By by by fade off, you mean you mean sink into the floor like a super villain layer. Apparently in Atlanta we have this thing about incredible equipment sinking into the floor. It's it's the planetarium at Emory. It's the Mighty mo Oregan over at

the Fox Theater. Why don't why don't we have this in the office anywhere? Yeah, you know, I think Ben sunk into the floor once, but I'm not sure that anyone besides me saw it, so I could just be crazy, but I don't know. Sometimes he likes to make me

think that. The other reason why I wanted to bring it up is because the planetarium itself has a projector called the Zeiss Skymaster z KP three, which is cool because it's it's Yeah, it's from the same company that made the very first planetarium projector, so again they're still in business. They're still making that. This one was installed, I believe in two thousand two, so it wasn't wasn't that long ago. Now, the one at Emory is computer controlled.

It's got a key board for manual input and has thirty nine different projecting lenses of different sizes that create the stars, planets, and other celestial bodies on the inner surface of the dome, and can project more than seven thousand individual stars, plus star clusters, nebula galaxies, the Milky Way, the planet's sun, the Moon, and it can superimpose lines between stars to illustrate constellations. So if you hear about these constellations and you think I just just looks like

a cluster of stars. I don't, I don't get it, then they can actually show the connections that U The inspired the imaginations of people thousands of years ago to call the stars wacky things like O Ryan. Yeah, I always had trouble with those. The only one I could ever pick out was a Ryan because I could pick out a Ryan's belt. But otherwise I was I was hopeless. I was. I was a whiz at it when I was a kid. I've had a really big astronomy phase. Yeah, I wish I had taken a course in astronomy. I

never did. Uh. The one at Emory also usually shows the sky over Atlanta. Again, no big surprise, but because it is a computer system, it's one of those that can show you the sky over any given point on the art at any given time, so you can set

it for whenever now. Um. The other cool thing about is that it's connected to a telescope that's on the building's rooftop, and they have a direct video feed from the telescope to the planetarium, So for astronomical events you can go and you know, yeah, just watch it, and just watch it from on the ceiling of this planetarium, which is you know, you could see a live event. They they've hosted several live events there, not all of

them were some that you could watch through the telescope. Like, uh, I'm pretty sure that the Mars rover landing you probably couldn't see thither the telescope. I cannot imagine that would be possible. Now, but but they do show some interesting feeds from various sources. So these days, I mean, as impressive as that planetarium is and as proud as I am as a as a native at Lantin, that's here. Uh there are others that are even more sophisticated. We're

talking four K or eight K projectors. So you know, think of the general rule of thumb, and granted it's a rough rule of thumb is four K means four times the the resolution of say a ten eight high definition television. That that's when you get into ultra high definition. Yeah, this is this is way more high def than your local cinema. Yeah, eight K even more so. Uh yeah, even if you have a four K cinema near you, eight K twice as good relations when you get down

to it. Again, that's very rough. I mean, anyone who's a a true video file is cringing when I say this. But yeah, you can go and see planetariums use eight K projectors. Some of them have full three D effects at six D frames per second, so you can actually feel like you're floating through space. They can take you on on journeys all the way around the the Solar System and the galaxy. You've got data feeds from all over,

like including space probes. It's pretty incredible. So yeah, yeah, some of these things can show over nine and stars that ago, go backward and forward ten thousand years into the past and future, um and and right take you so far beyond Earth to to show any kind of any kind of data that we have anywhere in the universe. Um and you can you can composite the astronomer's data

and and artists composits. Yeah, it's fantastic. I love the idea of also being able to see things like here's what the Knights Sky would look like if you were on Mars. I mean, that's incredible stuff that we clearly most of us are not going to ever have the chance of looking at the stars from the surface of another planet, or to go into the center of our galaxy and check out the black hole there. Yeah. I

had plans and they got canceled. The other couple that was gonna go with us something came up, and when that happened. Yeah, So that's the nice thing about the planetariums is they give us this opportunity to journey to places we physically could not get to and really understand more about our galaxy and the way everything seems to work in relation to each other based upon our knowledge now.

And the other nice thing about planetariums is that these facilities update as our understanding grows, So there are times when we might learn something that ends up affecting the way a planetarium is displaying the night sky, and it's pretty easy with digital projection to fix it and relatively yeah, and so you might even be able to watch something

like here's what a supernova looks like. And you know, there there have been events in the past where they've been amazing astronomical events, but many of them happened before most of us were alive, so it'd be really cool to be able to see those kind of representations things like uh Hallie's comment as another good example, or maybe if you wanted to see what it would look like with some of the other famous comments that have gone by, but you never got a chance when they actually happened,

maybe it was clowney that day, or maybe you weren't born yet. It would give you the opportunity. So super cool stuff. Um really interesting again to look into it, and the fact that so many different people have created similar but different approaches for this same purpose is really cool. I mean it's it's it's rare when we talk about a technology where there are all these multiple pathways that

get to the same destination. Usually we talk about convergence, where you know, competing technologies start to fall away until you have a clear front runner or maybe two possible ones. But with this there are lots of different ways. Oh yeah, and all of these interactions with multiple disciplines of of bringing together the knowledge that we have been gathering over the centuries about the universe around us, along with the optics fields that have let us use these technologies to

to project stuff onto a ceiling. That wraps up this classic episode of tech Stuff How planetariums work. Hope you enjoyed it. If you have any suggestions for topics I should cover in future episodes of tech Stuff, or perhaps a topic that needs an update, maybe you just want to say hi, the best way to reach me is over on Twitter. The handle we use is tech stuff H s W and I'll tell it to you again really soon. Yeah. Tech Stuff is an I Heart Radio production.

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