Mass - Sixty Symbols

uh we're going to talk about mass m is as with most symbols in physics gets used for multiple things but the most common use for m is to refer to the mass of something um what we don't know about mass is probably more interesting m is for mass so i've got a nice sphere which is a chinese metal ball for relaxing me and this weighs as i put it in the scales 140 grams as you can see it's a complicated concept to explain because mass has two two effects there are two things that that that mass matters for and this is what people normally mean by mass solid object which is really heavy and compact but the dictionary says that there are two different definitions according to chambers one is gravity um the more massive an object is the stronger its pull of gravity is this is the mass which acts downwards pulling this towards the earth and if it's a heavier object that is it has more mass or if i put on weight as i stand on the scales i weigh more this is a smaller mass which came from the red nose day a few years ago and you put that on there and it hardly moves and i weigh it at about five grams so you can actually measure the difference between these two quantities and the other is how much something doesn't like being pushed around so if you've got something that has a very high mass it has it really doesn't like being you know you have to push it very hard to get it to move at all now there's another aspect of the mass according to my version of chambers dictionary and that is its reluctance to move if something has a very low mass then then it's very easy to make it move so if i put these objects here and try to measure how reluctant this object is to move i can flick that and i'll do this with full vigor and it really moves did you see that oh i'll pick it up again and in some ways it's sort of one of the one of the great unknowns of physics one of the great unexplained things of physics is to why mass matters for both of these things and it's basically you can use the same number to explain both how strong something's gravitational pull is and also how much it doesn't like being pushed around and now i'll do it with this one with the same figure although i'm very reluctant to because i know and you can see that it moves but it's more reluctant to move and doesn't go with the same speed in fact it hurt my hand that is called the inertia of the object and it's the inertial mass of the object it's the reluctance to move in in the dictionary it said it's the resistance but i prefer to think of the object as wanting to stay still to be inert and it wants to stay where it is so those are the aspects of mass that we know about right from our childhood but the really fundamental question that hasn't been answered is what causes mass that's again uh there you're you're venturing into very deep water i have to say if you really want to answer that question you have to ask a particle physicist because they're the people who really understand these fundamental properties of matter as far as an astronomer is concerned it's just the property that objects have and we're quite happy to accept it as such and this is one of the questions that we're hoping that the large hadron collider might answer if it uncovers the higgs boson this is a big particle that we think might be involved with making objects actually have mass but nobody has actually seen it yet what is the origin of the mass of the electron or the mass of the proton or the mass of a quark or any fundamental particle because there is no um there is a theory but the theory hasn't been properly tested so it's still hypothesis there's a theory due to peter higgs of edinburgh that says there's a huge field throughout the universe permeating everywhere with a particle associated called the higgs boson and it is the presence of this field coupling to each particle which gives them mass but nobody yet knows whether this theory is right whether it's one higgs boson ii or whatever and that's the current state of play people have asked this question william waldergrave set a bet about 10 years ago it must be more because he was in the conservative government to ex that he would give a prize to the best explanation what a higgs boson was and the winning answer or something like the winning answer was that imagine you go into a cocktail party and you're very attractive so you found a 10 pound note and you're saying i've just found 10 pounds who dropped it everybody would come rushing towards you and then if you tried to move through the party you will be surrounded by people and find it very difficult to move whereas if you came in and said i've just lost 10 pounds has anybody found it you'll find everybody move away from you and that would be an anti-big higgs boson so i think it the the simple-minded picture which has no mathematics is this idea of accreting mass to you because you are attractive in some way just as the 10-pound note would be attractive and so you find it difficult to move and it's your reluctance to move against all these people clustering around you which is a simple mental picture i have well in astronomy oftentimes we don't use the most sensible units for measuring mass so in in truth sometimes we talk about measuring things like the mass of the sun in grams or kilograms um which gets into very very large numbers as with everything in astronomy the numbers get so big that they become completely meaningless so it's you know one with an awful lot of zeros after it well the large hadron collider is meant to be working at energy such that they would be able to detect the higgs boson if it's there the energy range covers it but then unfortunately as soon as they got it up and running uh the helium leaked out and the whole thing well there's huge amount of damage and it's gone back by about six months so in the next few years maybe we'll detect the higgs boson and then i'll find out more about it whether it's right or not in my line of work i'm talking about the mass of galaxies or even clusters of galaxies and these are some of the largest objects that we know about in the whole universe so what we tend to do is actually measure things not in kilograms but actually in units that are kind of more associated with the things we're interested in so for example the main mass unit that astronomers use is the solar mass the mass of the sun and that's kind of a useful number because for example if you figure out that some galaxy weighs 10 billion times the mass of the sun that immediately gives you a feeling that it's probably an object that's probably got about 10 billion stars like the sun in it even then the sun is so small compared to these large numbers that we have to talk in terms of billions or thousands of billions or millions of billions of times the mass of the sun i i grew up in the 50s and 60s and then we all had imperial units and so i had to learn grains and ounces and pounds and stone one after stone 100 weights and tons do you remember all those they were very difficult there are 16 grains in an ounce and 16 ounces in a in a pound and 14 pounds all these things and so you learned your multiplication tables but now we use kilograms meters second for everything and rationalize everything and it's certainly nicer but there's more flavor to the old units because when you talk about grains you're really talking about going back to babylonian times and measuring things in terms of grains of wheat or whatever or if you go back to roman times you talk about hands and feet and yards and in spanish the inch is called the pulgada which is just this part of your thumb because objects in astronomy can get to be pretty big you end up with rather a lot of solar masses but for some reason we don't actually use anything much heavier than the mass of the sun occasionally people kind of use a typical mass of a galaxy but but more often than not we just measure everything in solar units the mass of the sun so it's not always the most efficient way but at least it brings it back to something that we can actually comprehend in our heads can you can you comprehend the mass of the sun in your head uh yeah probably not there is a feeling that this was a french system set up by napoleon and it was one of the best things he ever did in many ways inventing the meter inventing the kilogram and somehow the english still love to have uh the old-fashioned pound but if you go and live in france they'll they'll talk about i would like to have a demi-levera which is half a pound of something in french so these old units that you grow up with and a part of the language and culture they stay even if you have been exposed to metric systems

Channel: Sixty Symbols

Views: 122,974

Keywords: mass, physics, sixty, symbols

Id: XJY24_n7nb8

Length: 8min 38sec (518 seconds)

Published: Tue May 12 2009