Bizarre Units used by Scientists - Sixty Symbols

okay so today we're gonna be talking about units and in particular the weirdest units of the weird and wonderful ones I'm gonna limit myself to the ones that are actually used in physics literature today because otherwise we'd be here all day talking about pirate ninjas on Mars and measuring bridges in Smoots so this is gonna be from my own experiences in research a little bit of research I've done and then also just talking to people on Twitter units are important we should care about units there was once a hundred and twenty five million dollar unit error in the Mars climate orbiter in 1999 basically us JPL were expecting the units of thrust in Newton's per second normal SI unit of thrust whereas Lockheed Martin gave it to them in pound force per second satellite entered Mars orbit to shallow and it exploded in the atmosphere and everyone swear it was lost people should care about units always write the unit's so what I want to start with is the one that when I was learning physics I thought was the weirdest it is a parsec so a lot of people might be familiar with the parsec was that famous line in Star Wars the Millennium Falcon made the Kessel run in 12 parsecs which makes people think that it's a time but it's not it's a distance the way that it is a fine is actually in terms of an angle it's really quite strange so it's all to do with this thing called parallax the named parsec comes from a portmanteau of parallax an arcsecond which is an angle parsec everybody probably at some point has done this where they put their finger up in front of their face and then like closing one eye and then open it so like oh look my thing is on the left hand side of your face Brady on the right hand right hand side I'm not even my finger yeah I I wasn't trying to wave it again and so basically what's happening there is that the foreground object is moving with respect to the background object Brady with respect to like what angle I am viewing my finger at and if I move my finger away from my face and closer to it moves a smaller angle and a bigger angle the same thing happens with stars so foreground stars moving with respect of the background stars at the constellations so in terms of like where the earth is in in winters left eye and where the earth is in summer my right eye sees a star move a certain angle with respect to the background stars and you work out that that angle actually corresponds to a distance use trigonometry and the distance from the earth the Sun so it turns out that a parsec is about 3 times 10 to the 16 meters a parsec is 30 petter meters we don't go around saying things like you know that the Sun is 5 micro parsecs away it's definitely only used for distances outside the solar system the cool thing is it scales really well so nearby stars are like 10 to a hundreds of parsecs galaxies are kiloparsecs across galaxies are separated by mega parsecs and then the universe itself is Giga PASOK's across so this comes from the idea of a Hubble length you know what's the distance to the farthest object that we can observe and that's about 4.5 Giga parsecs and that's also similar to the hubble time as well which is the best estimate for the age of the universe 14 Giga years billions of years kicking in so if it feels really weird to me to talk about distances in terms of angle shifts why wouldn't you just calculate the distance and I had a little put down from someone on Twitter for my millennial ways and they said to me folks wouldn't think parsec was so weird if their professional career extended back to the time when electronic calculators were Rarity's owned by university departments so bill keel professional astronomer in alabama put me in my place an electron volt it's not a voltage nope do you know what it is instead yeah so it's not a voltage it's an energy of an electron basically so it's the energy that an electron gains moving through a voltage of 1 volt so obviously electricity comes from the movement of particles with charges and protons and electrons protons tend to be locked into atoms so it's the electrons that move so it makes a lot of sense when you think about it like that but the reason that I think it's weird is that it's not a defined unit it's an empirical unit it comes from measurement so to actually refer to an electron volt in an experiment you have to have actually measure what the energy gained by the electron is over 1 volts because it's not necessarily like defined like say the speed of light is defined it's a measurement unit and and so I think that's kind of weird how it becomes the sort of like self-referential kind of unit so if you do measure an electron volt it comes out at one point times 10 to the minus 19 joules or 16 at Oh Jules if you prefer so atomic physics nuclear physics particle physics they all deal with the tiny things in our universe and so these kind of energies are appropriate for those fields cool thing is though it's not often used as energy unit it's used as a mass unit yeah so if we think about what Einstein told us e equals MC squared energy and mass are equivalent once we've measured how much energy an electron has in this one volt we then can know its mass if we divide it by C squared so a lot of times that you see electron volt is actually quoting the mass of these tiny tiny particles instead you just have to remember that there's this divided by C squared unit that's there as well that you have to not forget an electron nor point five one one mega electron volts per C squared and that might sound really strange but like most undergrad physicists will probably know that off the top of their head in mega electron volts four C's good which is kind of cool right the Higgs boson that's 125 Giga electron volts this is good and so again this idea of like the the prefix of the unit's gives you an idea of how much bigger in terms of an electron the Higgs boson really is it's one of those massive particles we know so it's an energy but sometimes used as a mass so Brady have you ever heard of snoo B yeah Newby's my favorite record it's not like Snoopy's cousin its rapid its newbie so anything this is one my favorites do be it stands for supernova unit in the B band so basically what it is is the number of supernovae per century per 10 to the power of 10 solar luminosities in the B band yeah basically what it boils down to is number of so you put over per century per galaxy because galaxies are about sort of 10 billion solar luminosities each ish about 2 to 3 for the Milky Way so I mean it probably the smallest number astronomy has so how could it give us that really even a 2 to 3 Snoopy galaxy exactly 2 to 3 Snoopy's you can do this in any astronomical wave band so you know this is the range of wavelengths that you look at to tell what amount of light that you're getting an optical and thread so that can be u bv RI g z YJ h KL m and cute so you can have Snoopy snoot K snug and the Newsies yeah you could have smoothies as well I wouldn't know whether it'd be like five snooze ease rather than like two to three Snoopy's for the Milky Way I don't know but I just want the idea that like professional super nova restaurant up is going around going oh yeah that one's like three Snoopy's i guess that would get same therefore the names just too much fun okay so let's break this down Kerma for kinetic energy released per unit mass anything about like a radioactive atom how much kinetic energy it releases air kurma is you know how much kinetic energy is released per unit mass into a unit mass of air so how much energy the air then absorbs air coma strength is then you know how much energy is deposited into the air at a distance away from the radioactive source squared okay so air kurma is obviously its energy so that's measured in just joules per kilogram but then people refer to that as a gray instead which is shortened capital gy not to be confused with a gig year which is capital g yr and so that's a gray and then you've got that in terms of you know the rate so it's per hour as well but it's you know air chemist strength so it's this distance away so it's the Gray's per hour per meter squared okay and they decided that was too complicated of a unit to to work in and so they gave it a new name you want to know what they called this unit unit they called it unit and it has just a capital u it's just it's just it's so ridiculous but they just call it you'd it like how lazy can you pay so one or arrogant yeah good yeah it's just this is the defining unit one you one unit is a micro gray per meter squared per hour an ERG it's not like an unsure leg it's actually a unit of energy so most of the units that we come across every day are you know like meters seconds kilograms I mean like there are a part of a unit system that's actually defined it's called the SI units basically the define system but and so in the SI units your standard unit of energy is joules people are quite familiar with that instead you can work in a completely different system of units which is called CGS or centimeters grams per second okay and that's your base system that all your units are built up and the base energy unit in that system is eggs okay because my son a little bit weird people but back at the turn of like sort of a century of the 1802 1900s this was the preferred system of unit Maxwell was a big fan of working in CGS and he wanted that to become like adopted across all fields this is one of these sort of historical units that was was in use then in in a lot of areas of physics because you know centimeters Graham's second when you're thinking about early physics in like labs those are the kind of scales that you're working with right you're working with grams of substance across centimeters in terms of seconds so it made total sense thing is cuz it's tradition there are some fields that still use it problem it's the fields that still use this it's astronomy where they're done quoting energies released from black holes like 10 to the 44 eggs per second and energy released from supernova of 10 to the 51 eggs it just is such a ridiculous unit to now work in so if you think about energy we think about maybe calories as well one calorie is forty one bigger eggs so that I'll give you an idea of how small an egg is and so this is why you see in astronomy is ridiculous right so much so the supernova scientist again these pesky super noted scientists just inventing units they decided that most supernovae are about 10 to the 51 eggs so they invented a new unit which is a foe which comes from 10 to the 51 eggs so a foe is 10 to the 51 X and so law go around saying okay let's supernova went off with like two foe or like 3.2 foe you look so gangster the only time I've ever looked gangster astronomy and I have to say this one probably got the most hate on Twitter like there are so many frustrated astronomers out there I have to use this unit and they just hate it the Jansky and it's used a lot in radio astronomy so it's all about the flux density that you have from a radio source how much energy you're actually getting from that radio source per sort of unit angle on the sky so a Jansky is defined as 10 to the minus 26 watts per square meter per Hertz so you're working in so Hertz is out which is the frequency of radiation you're out the frequency of the radiation you want to know in terms of like per meter squared because that's your collecting area of your actual sort of CCD as well and then your watts is obviously the amount of energy that you're actually getting from it but you've also had to integrate over the angle that you were on in the sky as well and the way that the Jansky is defined is that you have to integrate over a unit angle which is called the stir Radian so a stayer Radian is basically just a square Radian just a weird word for it so you have to integrate over square radians on the sky as well so it's just this horrendous unit especially if you never come across it before so I kind of feel like it's a little bit of a barrier to entry for a lot of students that come to Radio Astronomy as well in the fact that it's such a weird unit and also just conversion from that unit two units that people are used to working with in like optical studies instead like if you want to do like a comparative you know I have my source and I've seen it in the optical but now how much energy is it having the radio and how does that compare you obviously have to convert those units to the same unit to be able to compare them which brings me on to my next unit which is related which was called the Nano Maggie I just think of like tiny Maggie Simpson the Nano Maggie which is about three point six times ten to the minus six jean skis three point six micro G on skis is what the Nano Maggie is defined as and it comes from sort of your zero point in the magnitude system that you're working with this magnitude is like brightness system in astronomy and it's just this huge mess still so it's on my list because it's cause astronomers so much frustration over the years this is a paper from astronomers again and they're studying molecular cloud densities so that the clouds that are gonna form stars the gas it's all going to condense to form stars they're looking at how dense they are in the universe and what the pressure is in these clouds as well that's gonna squish them together so sentence is more over some of the highest column density clumps would require enormous confining pressures of roughly a thousand to a billion Kelvin per centimeter cubed so that was a pressure in kelvins per centimeter cubed Kelvin a unit of temperature and centimeter cubed a unit of volume so they're quoting pressures in temperatures per volume most the time pressures are done in atmospheres or bars as well here they're doing it in kelvins per centimeter cubed which probably doesn't make any sense until you think about the context so in space the gases that you're dealing with the gases you're modeling here they're very low density there's barely any interactions you know there's no collisions and so basically what we call that is an ideal gas so we might remember that from high school ideal gases okay let can beam always modeled as an ideal gas and so that means that we can apply the ideal gas law which people might remember PV equals NRT P being the pressure V being the volume n is the number of moles of an element R being a constant and then T being the temperature astronomers change this so that they're working in the number of actual atoms they've got because they can kind of estimate the number a so because it's such a low density they rearrange it so that it's P equals number of atoms divided by the volume times by the Boltzmann constant times temperature and they basically just say drop the Boltzmann constant and then they say the pressure is there for the temperature of the volume and so basically everybody knows that when they quote these numbers of like a thousand to a billion Kelvin per centimeter cubed but there's some Boltzmann constant in there that they haven't taken into account but they don't say it it's just that everybody knows that it's there which I think it's just really lazy and also they haven't dumped this unit I feel like if this unit should be dub like they're lazy or something like it's just they need to give it a name if they're gonna keep using it because it's really strange and it would really confuse people especially people like new to the field that have never even come across this before last but not least is a barn you've heard a barn before like barn conversions or like sheds and stuff okay so a barn is using particle physics all the time it's a cross-sectional area of a particle okay so it's about a hundred femtometers squared its defined us so that's 10 to the minus 28 meters squared it's about the cross-sectional area of a uranium nucleus so the reason it's called a barn it comes from the u.s. expression couldn't hit the broadside of a barn which means that your aim is terrible basically so obviously the idea of particle because you're trying to get two particle beams to collide no Amy just be good so you need to be able to hit a bond and so they they talk about you know one bond cross-sectional area or we know we got to hit that target within like point by bond I presume I presume that's what like the control centers if these particle physics experiment for like the cross-sectional area of a particle you know you've always got something tiny times by something tiny I was even smaller so that's why they needed a new unit I'll give them that it's not an SI unit necessarily but it is recognized by them as a unit because it's used so much in the field as well similar to a Jansky actually there's also technically the outhouse which is a micro barn and the shed which is a Yocto barn the thing that I love about bonds is that you basically have a tiny area okay and what about if we combined a tiny area with a very large distance so if you remember we had a very large distance of beginning we had parsecs and we were talking about the Hubble distance being like 4.5 Giga parsec okay and if we combine a very small area and a very large distance we get a volume okay but very very tiny area and very very large distance gives you a volume that's actually quite reachable to like everyday volumes combined a barn in a mega parsec you get a barn megaparsec which is about the size of a teaspoon yeah which I really really like remember our Hubble length before was a 4.5 Giga PASOK's so you can have a Hubble bond which again is a volume and it's about 13 liters so you could talk about like filling up your car with like rubber bands if you wanted or like my car get so many cobble burns miles per Hubble bond which i think is really really nice so that got me thinking whether we could use these crazy units in something more everyday perhaps like a cake recipe and perhaps we could have a physics inspired cake recipe all in crazy units yeah yeah yeah okay I actually got a cake recipe you made one I actually well I acquired a cake recipe yeah from maryberry obviously yeah and I rewritten her cake recipe yeah to be physics yeah yeah I feel like this should be read in like my most be see RP accent what do you think yeah yeah okay okay preheat the oven to give an output flux density in the infrared regime of seven Yocto nano Maggie's then make sure to grease in line to 6.5 at Oh parsecs sandwich tins break for eggs that's eggs not eggs into a large mixing bowl then mix in 126 Yasha electron volts for speed of light squared of both sugar and flour with two barn megaparsecs of baking powder and naught point naught six humble bonds of butter divide the mixture evenly between the two tins and bake the cakes on the middle shelf of the oven for three femto Hubbell types sandwich together with Jam once cool and sprinkle over some castor sugar for decoration and there you have it a physics inspired Victoria sponge cake [Music] you

Channel: Sixty Symbols

Views: 255,296

Rating: 4.9424214 out of 5

Keywords: sixtysymbols, units, SI units, parsecs, nanomaggy, erg, astronomy

Id: hsEB65Q4kHI

Length: 18min 50sec (1130 seconds)

Published: Tue Oct 30 2018

Reddit Comments

[u/dekket]

An absolute Unit.

[u/JMoVS]

You missed the "DSE"! The, no joking, Dry sheep equivalent! @JeffDujon should know that one! :D

https://en.wikipedia.org/wiki/Dry_Sheep_Equivalent

[u/alternateme]

FYI: "Dr. Becky" just started her own YouTube channel now. (Only a few videos so far, but I'm excited to see more content!)

[u/hairnetnic]

No scruples per noggin. Waste of time.

[u/Jockl132]

This inspired me to make a python scripts that replaces the units in cooking recipies with silly ones. Dimensionless units like 4 eggs could be 6.64e-24 mols of eggs for example.

I will probably post about it somewhere on reddit when I have some progress to show

[u/cptnpiccard]

Come for the cuteness, stay for the science!