Neil deGrasse Tyson Explains Measurements

yes which one is this okay let me first ask how told you 5 feet 10 inches or 11 if it's for a casting director all right are you not 510 and a half I 5 10 and a quarter nobody believes you when you say that okay but you're talking to me okay I'm your friend 510 and a half could work for me okay okay I've heard people say I'm exactly 510 and I say what is what do you mean by that if I want to just be a pain in the ass what do you mean well it came in exactly 510 right well if you look at if you look at a tape measure okay okay and you go to like 510 right the the mark that indicates 510 uh-huh has a thickness okay so then you say this wait a minute so you're saying that yeah what where do you fall in the thickness of the mark correct if that determines your exact whatever measurement I what I'm saying is that if you're measuring something you can never know the answer exactly it will only be an approximation that you just agree to and move on I disagree okay okay because I think about what you said were true we couldn't have that atomic clock you told me about oh well do you remember stuff remember things okay so let me tell you out the atomic clock okay when did I tell you about the atomic clock at about how the fact that because measurement of time was not at one point precise right okay okay and that basically you couldn't have you couldn't have this you wouldn't have the same time one place as you would the other because you didn't have well the measurement of time measurement of time wittingly so we went to an atomic time right rather than earth reverse rotation by the way and the thing to was that the Earth's rotation is not the same we didn't know that and you can't know that if earth is your measure so you all slowed the precision measurement to an atom and the atom has very high dependability in its frequency that's vibrating you get how many times it vibrates per second is the cesium atom you do that you get that now you look back at earth it oh my god earth is slowing down right you could not have known that without that know if earth was your man what is Earth or the means of measuring you would never know that the correct as the mean itself is actually slowing down correct okay so all I'm saying is when you make a measurement you can never know anything precisely you can only know it to some point where you agree so here's the best example okay it's related to how tall you are all right the best example I asked you how long is the way I'm I'm six hands tall that would only be that's four inches oh I don't know I thought I was using the one where horses but go ahead write the hand okay so you don't say how many feet so I mean hoofs oh sorry so the coastline of England all right okay how long is it how would you go about finding that out well I would take you would have to measure the actual squiggly luckily I get out a map that's the a post get a nice big map right and you get a squiggly line okay put a ruler up against because it's squiggly so what are you get like a string okay you take the string and you do that all right you coming at it and then you when you're done you go out and you hold it up against the sky oh it's six at eight hundred miles long okay I don't know the exact number so there it is but wait a minute if I had a bigger map it would show more squiggles wouldn't it okay so with a bigger map I want if I do this exercise again my string is doing more as it goes around now I got more string out of better measurement it's well so it's not just that it's a bigger map but of course the scale is bigger but my string did more right because I got more detail okay which length of the coastline of England are you going to use the one from the small map is one of the bigger man probably the one of the Big Mac is made more precise for you right are you done no let's make it even bigger in fact let's make a map the size of England okay and now gonna have to do that because England's there so now you just go around with a string wait a minute guys do that wait there's a boulder there what side of the boulder you were gonna go around wait a minute the tide is coming in and out the coastline is the boundary between land and water but the water is not constant where are you going to draw that when then you get down to the to the to the to the sand which same green are you gonna go around what I'm telling you is making me not believe in math a lot of time you is yeah you can measure their circumference of Colorado okay because it's got square sides but when you guys squiggly lines that measurement is an agreed upon point where you're gonna say I give up let's just call it this all right that's my point that's the point right and and you can say do you know you do is that you make measure at high tide or at low tide right or an in-between tide all right you have to pick you have to at some point you just have to say we're done here guys okay how much do you weigh okay I've had it scaler all right I got a scale just like a kitchen scale okay and I turn it on and it measures you know I put you do the tear and tear and all that and it'll say let's say three three ounces okay is three and a quarter ounces it doesn't register that it'll only register again when it hits floor ounces true wait so it can't measure this scale cannot measure between three and four ounces right now let's get another skill that goes through tenth seven ounce okay so now you get three point four two ounces 3.4 ounces okay what's the next three point five so poaches in between those okay can't measure that so now I got a scale there does now you got it scaled it goes to two decimal place and you can take that all the way right wait am it is ugly exactly because now you have made scales and weight summer into fractals because I'm late yes you can just kiss come we can keep going all the way down but you never get you're never ever because we'll always be societies so the line that you're doing the measurement with it will always have a thickness so you can measure things to some approximation that we all conversationally agree with but you will never out care what it is okay you can count precisely you're exactly two of us here on this set okay right there's not two and a half that we can count that are we counting the voices in my head you have 3/4 of a voice I got 1/4 we have to sleep so so you can count things per second you cannot measure with unlimited precision interesting yes that is that but see no okay yeah now here's what happen right just this past year all right the kilogram something I know nothing about because I'm American that mark American non drug dealer kilos in the international system of measures that keeps track of the length of the second and the lake the duration of a second the length of a meter the and the mass and a kilogram that the last thing based on an artifact in that facility was a kilogram was the kilogram yes everything else is based on measurements of on highly precise things that you can duplicate in laboratories this was an artifact sitting there that's a kilogram by definition right okay right they said we got it we can't do this anymore you know why because they made copies of it put them around the world and every now and then they bring them back and none of them are equal anymore some are losing atoms there so they said we need we got to fix this yeah so that little thing that you see that wouldn't use when it says it yeah okay that little cylindrical a little candle on the tablets when they're doing the thing all right right correct so you're saying that that no longer is the proper measurement of a kilogram as of the middle of 2019 that's correct no longer because here's what they did we have ways of making precise crystals of silk oh so precise that you can count the atoms in the lattice that's pretty cool so what they did was they took the kilogram that's dill they this dope they took the kilogram right and then they made a silicon sphere pure silicon and they made them equal each other okay once you do that you throw away the kilogram right and now I know exactly how many silicon atoms equals a kilogram so now I have an atomic representation of what the kilogram measurement is and I can count the atoms so there is no uncertainty in the mass of the kilogram right now and and I can tell people around the world you want a kilogram assemble this many silicon atoms the or they also do also that - go ahead it's it's avocados number what do you remember him that's was what Avogadro's number remember it was 6.02 times 10 to the 23rd it's how many particles make a mole right all right once you set the kilogram with the silicon atoms you set them you set how many part how many particles are in a mole we've set avocados number and it's now to nine decimal places that is we got this that's pretty little done that's cool so it's true for everything you measure on the speedometer your weight the time the temperature there's always some range across the indicator where it could be at the bottom the middle or the top make a thinner one there's gonna be a bottom middle the top you will be doing that all the way down that makes sense that is the world of measurement so here we go people what have we learned believe nothing no just as important we say we're good you're fine I'm good with that you're not 5/8 you're not six feet I'm good with it I'm gonna be five eight and seven five ten anyway this has been a Startalk info bit thanks Chuck ya know what helping me through it by the way bite eight bits no isn't it but this mate depends on what you're eating [Music]

Channel: StarTalk

Views: 580,494

Keywords: measurements, Neil deGrasse Tyson, Chuck Nice, StarTalk, kilogram, particles, Avogadro's Number, time, precision, atomic clock, cesium, science podcast, map, Avocado's Number, Earth's rotation, silicon, atoms, avogadro, avogadros number, star talk, measurement, measure, measuring, space podcast, astronomy podcast, physics, science, space, neil degrasse tyson podcast, niel, nielsen degrasse tyson, startalk radio youtube, startalk radio podcast, podcast, explain, explainer, education, weight

Id: 8IuBLd3qoUo

Length: 11min 21sec (681 seconds)

Published: Tue Mar 03 2020