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Dr. Rhett Allain, an Associate Professor of Physics Education Research at Southeastern Louisiana University, brings topics each week that he finds fascinating! Join us for STEM Radio every week!
It's science.
Tyler Thomas:Alright. Ladies and gentlemen, welcome back to another edition of STEM Science Radio with Tyler Thomas and the host himself, Dr. Rhett Allain. And Rhett, it's good to have you in even though it's a little cold outside, but we're having fun. And we are talking about
Dr. Rhett Allain:Clocks. Clocks. I mean, do you use clocks?
Tyler Thomas:I like to look at my phone that has a clock on it. Okay. I used to rely on clocks before I had a phone when
Dr. Rhett Allain:I was mean,
Tyler Thomas:phone's a clock?
Dr. Rhett Allain:So I'd I'd say
Tyler Thomas:time is pretty important, especially when you have to upload something at a certain time or this and that. Yeah.
Dr. Rhett Allain:So I mean, we we run on clocks. We run on we always have. Right? Whether it's a seasonal clock, a yearly clock, a daily clock, whatever. But there are some really important developments in clocks, and they're used for some really important things.
Dr. Rhett Allain:But let's talk about the very first clocks. How did how did humans first measure time?
Tyler Thomas:I'm gonna give you a guess. The sun.
Dr. Rhett Allain:The sun. Right. I mean, it's the easiest way to do it because you can say, oh, the sun rises, the sun sets. Check. That's one day.
Dr. Rhett Allain:That's a clock. If you say the sun came up, the sun came down, that's it.
Tyler Thomas:It's a built in clock.
Dr. Rhett Allain:It's a built in clock. And then we also have a sundial. Have you ever seen a sundial? I haven't. They're kind of difficult to use, because the position of the sun changes over the course of the year.
Dr. Rhett Allain:But the goal is to look at where is the sun at the highest point, or when is it at the highest point. That's what call solar noon. There's a there was a there's a nice sundial in I think it's the New Orleans Zoo. They have one out there. I've seen some other places.
Dr. Rhett Allain:They have more elaborate ones too. But if you just wanna take a stick, stick it in the ground and look at its shadow over the course of a day, there's there's your clock. That's pretty easy. Right?
Tyler Thomas:Yeah. You know what's coming, when it's coming, and how it's gonna be there.
Dr. Rhett Allain:Yeah. And you can you can estimate when the sun's gonna set and all that kind of stuff. And then if you monitor it over the course of the year, you actually can see some really cool things. But the point is that that's the most basic clock. Now humans made even better clocks, and we'll talk about that on the next STEM Science Radio.
Tyler Thomas:It's science. Alright, ladies and gentlemen. Welcome back to another episode of STEM Science Radio. Tyler Thomas with doctor Rene Lane, and we are talking about clocks this week. In the last episode, we talked about the original, the OG clock, the sun.
Dr. Rhett Allain:And, you know, there's a lot of developments between the sun and where we're gonna get now. But I wanna talk about this clock based problem called the longitude problem. Have you ever heard of the longitude problem?
Tyler Thomas:I've heard of longitude? I've heard problems, but I don't know if I've heard of the longitude problem.
Dr. Rhett Allain:So, you know, we can measure our or determine our position on the globe using longitude and latitude. And the latitudes are the lines that run east and west. They're really easy to determine your latitude. You can just look at the North Star. Okay.
Dr. Rhett Allain:So the North Star, and if you measure how high above the horizon it is, that's your latitude. That's that easy. Okay. Yeah. But longitude, how far east and west you are, is very, very, very difficult to measure.
Dr. Rhett Allain:And in fact, you need a clock. You need a clock in order to do that. So if you look at a clock and you measure the time of local noon, when is the sun the highest, and compare that to local noon in a particular location, which would be Greenwich. Greenwich Mean Time, that's where that comes from. So that's our zero point.
Dr. Rhett Allain:And then if you measure the difference in time between solar noon at Greenwich and where you are, you can find your longitude. Now the problem was, how do you get a clock and put it on a boat and make it be accurate?
Tyler Thomas:Because it's moving?
Dr. Rhett Allain:Yeah. Because the boat's moving. Think about, you know, seventeen hundreds and things like that. You know, one very easy clock to make is a pendulum clock. So this mass swings back and forth, and you can use that to determine time.
Dr. Rhett Allain:But if you put that on the boat and the boat's swinging back and forth, you have a problem. Right?
Tyler Thomas:Yeah.
Dr. Rhett Allain:And so there was a big competition to come up with a better clock that you could use on a boat so you could determine where you were. And they tried more elaborate pendulum clocks, ones that correct themselves, ones that could be exposed to seawater and environment conditions that you'd have on a boat, and they ended up with the invention of the pocket watch. That was the only way that you could really get it to work. So with the pocket watch, you could actually measure your position on the earth, and so it was really kind of a big deal. And it's amazing to think that, you know, the invention of a pocket watch was so important in terms of navigating the earth, but that's what it was.
Tyler Thomas:Wow. And so is that why the pocket watches have a compass on them or did they always have a compass on
Dr. Rhett Allain:They didn't always have a compass on them. You know, if you just have a normal gentleman's pocket watch, it probably doesn't have a compass, but a lot of them do. We don't use pocket watches anymore, but that's that's what you have right there. So now there are some more much more sophisticated clocks that we use now. We don't really base all of our times off of a of a pocket watch.
Dr. Rhett Allain:And we'll talk about that on the next STEM Science Radio.
Tyler Thomas:It's science. Welcome back, ladies and gentlemen. Talking about clocks here on STEM Science Radio. Tyler Thomas with the host, doctor Renal Lane. And last episode, we talked about longitude and how it's calculated using true north well, not true north, but what was the
Dr. Rhett Allain:A watch. A pocket watch.
Tyler Thomas:Oh, yeah. Well, a pocket watch.
Dr. Rhett Allain:Yeah. Yeah. So and, you know, it was funny because they actually tried other things before they got to the pocket watch. They tried to use one of the clocks they tried to use to measure longitude was the orbit of moons around Jupiter. So if you look at Jupiter and you can kind of see where the moons are and use that as your clock, right?
Dr. Rhett Allain:And it didn't really work. But it was a great idea. We don't use Jupiter. Use We pocket watches. We don't use pendulum clocks for scientific measurements.
Dr. Rhett Allain:One of the things that we use is what's called an atomic clock. Have you heard of an atomic clock? I haven't. Okay. So if you want to have a clock, you need to have something that oscillates it with a regular frequency, and then you really just count.
Dr. Rhett Allain:Right? So if it's a pendulum, you count how many times it goes back and forth, and that's really your measurement of time. But if you have a normal pendulum clock, it may be a second for one oscillation. What if you wanna measure one one thousandth of a second? Well, you can't.
Dr. Rhett Allain:Right? Mhmm. Because it's gotta be just one second or more. So you need something with a much higher frequency and something that's super stable. That's where an atomic clock comes in.
Dr. Rhett Allain:So you take, normally we use something like a cesium atom, and we bombard it with electromagnetic radiation to get an electron in the atom to go to a higher orbital level and then back to lower. So it oscillates between levels, And that oscillation frequency is set, right? It's some constant value. And it's very fast. So you can get very, very accurate clocks.
Dr. Rhett Allain:And in fact, if you look at an atomic clock, it's accurate to within one second in the age of the universe. If you look at Wow. How Yeah. So that's kind of crazy. Now, the problem with atomic clocks is that they're they're not really easy to set up, right?
Dr. Rhett Allain:You want to shield them from external radiation so that that doesn't oscillate at a different frequency based on that. So they have they're not really portable. Mhmm. And that is a problem. But they're very, very important for scientific measurements for measuring very, very, very small time intervals, but not portable.
Dr. Rhett Allain:So that's the problem.
Tyler Thomas:Not portable. Right. You think it's possible that one day there will be a portable one?
Dr. Rhett Allain:There is a portable one, and we'll talk about that on the next STEM Science Radio.
Tyler Thomas:It's science. Welcome back, ladies and gentlemen. Another episode of STEM Science Radio. We're talking about clocks. It's Tyler Thomas with the host, doctor Rhett and Lane.
Tyler Thomas:In the last episode, we talked about atomic clocks and how they're not portable. But, Rhett, you you told me you told me there's a new new fancy
Dr. Rhett Allain:So so quiz. I'm quizzing you based on the previous episode, right? How accurate are atomic clocks?
Tyler Thomas:Within one second of the age of the universe. Very good. You get
Dr. Rhett Allain:an A on that quiz. Thank Good you. Yeah. So they're very important, we'll talk about why they're important later, but they're not portable and that's the problem. So so think about an atom.
Dr. Rhett Allain:You know, if you have an atom like cesium, you have a nucleus and in that nucleus you have protons and neutrons, and then you have electrons on the out out of that, and those are the ones that we use to measure time in a cesium atomic clock. We use those electrons. But they're easy to change positions, they're easy to do a bunch of stuff, and that's that's not good. So a more portable atomic clock, it's actually called a solid state atomic clock. In theory, it could be like the size of your phone, and not a big scientific experiment.
Dr. Rhett Allain:But what it does, it doesn't use oscillations of electron energy levels. It uses oscillations of nuclear energy levels. So if you have a nucleus and you excite it, it can go to a higher energy level based on the oscillations of the protons and neutrons in the nucleus. And what that does is that means that it's not susceptible to external radiation. So you don't have to worry about shielding and all this other complicated stuff to make it stay on its frequency.
Dr. Rhett Allain:You can do it with just a few atoms. And that's what these solid state atomic clocks are called. They're solid state, just like the chips in your phone, we call them solid states or they deal with transistors and different materials that are connected together like that. So but with this solid state atomic clock, it could be just as accurate, but portable. Now, you would be the next question you should say is, why do you even care about a portable atomic clock?
Dr. Rhett Allain:Right? Is that your question?
Tyler Thomas:I well, I was gonna ask, is there any downside to a portable atomic clock?
Dr. Rhett Allain:Well, they're more expensive to make, of course. And they're not well established yet, but they're gonna be. Right? They're gonna be more popular and more easily accessible. But we have a way to do it, and that's an Well, important
Tyler Thomas:was my thing. Was like, if you have something that's portable versus something that's not portable, and there's no downside to the portable one, think I'd rather the portable one. Right. At least to have the usefulness.
Dr. Rhett Allain:But what would you use that for? That's the question.
Tyler Thomas:Oh, no idea.
Dr. Rhett Allain:And we'll talk about that on the next STEM Science Radio.
Tyler Thomas:It's science. Alright, ladies and gentlemen. Welcome back. Another episode of STEM Science Radio. We're talking about clocks.
Tyler Thomas:It's Tyler Thomas and the host, Retta Lane. And in the last episode, we talked about the atomic clock, take it, make it smaller, portable, solid state, but what's the purpose of it?
Dr. Rhett Allain:Yeah. So you actually can use portable atomic clocks with super, super, super high resolution of time measurements for something very cool, and it has to do with general relativity. So general relativity is one of the things that Einstein came up with, and it has a bunch of stuff in there. One thing is that he says mass and gravity change how we perceive time. So if you're near a black hole and the gravitational field is much greater, then your perception of time would be different than someone that's not near that.
Dr. Rhett Allain:We actually can measure this time shift just by with our GPS satellites. So satellites in space have are at a different gravitational field than on the surface of the Earth, and so they experience a little bit different time. Not much, but a little bit. And by making a correction for that time, we can get more accurate GPSs. But imagine that you could have a super, super even more accurate measurement of time.
Dr. Rhett Allain:You could actually measure changes in the Earth's gravitational field due to stuff beneath the Earth. Right? So the Earth's not a uniform sphere. So as you move around, gravitational field changes slightly due to the type of rocks underground or the other if there's water there or whatever. So you could actually measure the changes in the stuff underneath the earth just by looking at the changes in the gravitational field that you would measure by looking at how time changed.
Dr. Rhett Allain:By tiny, tiny, tiny, tiny amounts. So, so tiny that you would never perceive it. If you can measure it, you're really using gravitational fields to look inside the earth.
Tyler Thomas:I can't even fathom that. It's not computing.
Dr. Rhett Allain:I mean, we do that anyway. We do that with satellites. We have a satellite going over orbiting the Earth, and there's slight changes in the gravitational field, and they make a gravitational field map. So like, oh, this part of the the country has a higher density ground. You know, Louisiana doesn't have a lot of rocks, so it's not very dense underground.
Dr. Rhett Allain:Whereas, you may be in, you know, Yellowstone, there's more rocks closer to the surface, so it's a higher density surface. And you have a slightly different gravitational field. But if you can make a portable gravity detector, it'd be like a metal detector for mass. You can just walk around and see how things change, and you could find spaces underground, maybe maybe there's something empty there or lower density with water, higher density with, you know, not gold, but, you know, gold, something like that. So you could you could just kinda look around with a high precision solid state atomic clock.
Tyler Thomas:I feel like the person who discovers that will definitely win a Nobel.
Dr. Rhett Allain:Yeah, think so too. Well, he already did it with Einstein.
Tyler Thomas:Oh, man.
Dr. Rhett Allain:Yeah. But that's what you need to know about clocks on STEM Science Radio.