What is mass? - If I knew, I wouldn't ask :)

Palomar · 2002-06-04 16:17:36

Alrighty folks, here's a "little" science term I still do not understand.

What the heck is ::mass::? Any replies in simple English, please!

About a year ago, I was subscribed to one of the MS mailing lists. The topic of recreational activities for colonists came up...and I asked about the possibility of a swimming pool, given the lower Marsian gravity, etc. One nice and polite fellow (I think a scientist or engineer) mentioned that ::mass:: would also have to be taken into consideration.

He gave an explanation of how mass comes into play in this (and other) regard...no light went on inside my cranium.

Here's your chance to try and explain what mass is. I want to understand what it is, at least on a "beginner's" level. Physics were never my thing (yuck). The winner may receive a year's supply of Turtle Wax!

--Cindy

MS member since 6/01

Phobos · 2002-06-05 03:29:33

Hmm, that free supply of turtle wax sounds tempting. I guess if you simplify it mass would be the amount of matter that something contains. A lot of people mistake mass for weight, not knowing that weight is merely a measure of how gravity is affecting mass. As for the swimming pool, I'm not exactly sure what he's getting at. Is he just making some point about the difficulty of transporting a mass of water or how the water would behave under Martian gravity? I'm lost.

Byron · 2002-06-05 08:47:41

Hey,

Maybe this will clear things up a bit Mass is a constant; i.e., one cubic meter of water always has the same mass, whether it be on Earth or Mars. This something that astronants have to contend with in microgravity (like building the ISS.) Objects may not have any weight in space, but they still have the same mass and the same inertia, so it still takes effort to move large and heavy objects around. Same thing on Mars, less weight, but the mass stays the same.

As for the swimming pool idea, it certainly sounds like fun, as the water would be much more "wavy" and "bouncy" than a pool here on Earth. The sides would probably have to be a lot higher to prevent all the water from splashing out..lol.

Palomar · 2002-06-05 13:07:06

Thanks for the answers, Phobos and Byron. I have a better understanding of mass now.

Phobos wrote: "As for the swimming pool, I'm not exactly sure what he's getting at. Is he just making some point about the difficulty of transporting a mass of water or how the water would behave under Martian gravity? I'm lost."

Again, this was about a year ago, so I'm trying to recall from memory as best as possible. I think his point was the properties of mass having to be taken into consideration, and how water would behave in Martian gravity.

--Cindy

Phobos · 2002-06-05 21:10:57

As for the swimming pool idea, it certainly sounds like fun, as the water would be much more "wavy" and "bouncy" than a pool here on Earth. The sides would probably have to be a lot higher to prevent all the water from splashing out..lol.

Aw man, just think of the high dive you could strap to the side of that beast. Make it like three times as high then do a big cannonball, you'd drown the whole colony in a tidal wave!!
So Cindy have you already given away that free supply of turtle wax to Byron? I'll try not to take it personally if you did. *sniff* ???

Josh Cryer · 2002-06-06 09:10:13

Actually, I was thinking about that. Because the prospect of swimming in low G is simply awesome (I never thought about it before). But since you would fall at a slower rate (about 2.4 times slower), would not your impact into the water cause about the same ammount of displacement (only it would look 2.4 times slower)? Also, wouldn't the surface tension on the water be higher?

Byron · 2002-06-06 10:44:34

Here's my two cents: Yes, one would have to jump from a point 2.4 times higher to reach the same velocity on impact--i.e., a 3-meter board on Earth would be equivilant to 7.2 meters on Mars, and it's true the same amount of water would get displaced upon impact (and the inertia would be the same), but the .38 gee would allow that water to "bounce" a whole lot higher (2.4x?) and for a much longer time. I wouldn't think the difference in the gee would have much effect on surface tension, if at all.

Phobos · 2002-06-06 20:01:45

Also, wouldn't the surface tension on the water be higher?

It makes sense that it would. It would probably behave just a tad like gelatin. All this talk of big waves and jumps from impossible heights has me convinced that going to Mars is worth it just to go swimming.

Tom Jolly · 2002-06-12 08:18:10

It makes sense that it would. It would probably behave just a tad like gelatin. All this talk of big waves and jumps from impossible heights has me convinced that going to Mars is worth it just to go swimming.

Don't forget flying. Once the atmosphere is thickened up to Earth normal, or even if it's just a bubble canopy on a city at Earth normal, "hang gliding" will be a totally different experience, with relatively tiny wings compared with today's gliders. We can ALMOST make a man-powered glider here on Earth (we can, it just takes an Olympic peddler to power it). On Mars it'll be relatively easy. I have to say, Mars is going to be a real treat once it's terraformed. The ultimate vacation resort. Of course...no one is going to want to leave it once they get there.

Phobos · 2002-06-12 15:41:14

Awesome, I never thought about the possibilities of having manpowered gliders on Mars. If we could thicken up the Martian atmosphere to the same degree as Earth's I'd definately take up gliding as a sport. I can see all kinds of endurance contests, like the first guy to try to fly all the way around Mars non-stop.

Palomar · 2002-07-20 10:43:01

*I'm afraid I'll have to admit I'm still confused about what mass is. ??? I thought I had a better understanding of it, thanks to the persons who replied to my initial post, but now upon re-reading some of Arthur C. Clarke's novels I'm apparently confused again.

Is this what mass is:

Weight + Gravitational Pull = Mass?

Or is it:

Bulk + Gravitation Pull = Mass?

Help please? I really want to understand this, since I come across it so much in reading science stuff.

--Cindy

Byron · 2002-07-20 14:48:23

*I'm afraid I'll have to admit I'm still confused about what mass is. ??? I thought I had a better understanding of it, thanks to the persons who replied to my initial post, but now upon re-reading some of Arthur C. Clarke's novels I'm apparently confused again.
Is this what mass is:
Weight + Gravitational Pull = Mass?
Or is it:
Bulk + Gravitation Pull = Mass?
Help please? I really want to understand this, since I come across it so much in reading science stuff.
--Cindy

Perhaps you might be overthinking things a bit...a common affliction of many of us here on this board..myself included..LOL.

Let's see if I can clear things up for you...

Forget those statements you posted above...those were confusing me as well..lol. In order to have gravitational pull, one must have mass, and all mass generates gravity..even you and me..but you need a LOT of mass to have an appreciable amount of gravity, such as on a planetary level. This could be shortened to: Mass = Gravity. The greater the mass, the greater the gravity.

Of course there's more to this than that simple statement, and that is a "body" of mass can be more dense or less dense, depending on what it is made of. For example, if there was a sphere of solid lead (a dreadful thought, I know, lol) the same size as Earth, you can bet your bottom dollar that the gravity on that giant ball of lead would be much higher than here on Earth, as lead is much more dense than the earth is, and therefore you have more mass concentrated in a smaller space, which means more gravity. A good example is the planet Saturn. It does have a lot of bulk, but since it is less dense than water, gravity on Saturn is not much greater than Earth's, although it's a heck of a lot bigger than Earth in size.

The idea of weight comes in when you're talking about the "effect" of gravity...gravity is the force that creates weight, and that varies depending on where you are. But mass is what stays the same no matter where you are, and the "bulk" of an object really depends on what it is made of, which then determines the mass of that object. One cubic meter of water will have the same mass no matter what..if that volume of water was turned into steam, that cubic meter of water will take up a great deal more space, but the mass is still the same, as we're still talking about the same number of water molecules...they're just more spread out if the water was turned into steam.

Another way of illustrating what mass is, is the idea of taking a ping-pong ball and a similar-sized ball made of steel into space...neither will have weight...but the steel ball still has a heck a lot more mass than the ping-pong ball..and if both balls were thrown at another person, the steel ball is the one that's still gonna hurt, as it will take a great deal more energy to stop the inertia of the steel ball than the hollow plastic one.

If I still haven't made myself clear...please let me know, and I'll try again....

B

Phobos · 2002-07-20 16:38:07

Mass is merely a clump of matter, it isn't really dependent on gravity to define it at all even though mass generates gravity.

So your equation "bulk + gravity = mass" should really read "bulk + gravity = weight"

the equation for mass would look something like this "bulk=mass"

Weight and mass aren't the same thing. Weight is merely the affect of gravity on mass. Think of mass as being an aggregate of sub-atomic particles or atoms. It's something of a mystery though why these particles have mass at all. Maybe your getting into a very fundamental question on why anything has mass at all. I don't think anyone has really hammered out a definitive answer to that yet.

Palomar · 2002-07-20 16:59:48

If I still haven't made myself clear...please let me know, and I'll try again....
B

*Okay...lemme see if the light's beginning to dawn in my dense brain [ha ha]:

Mass is the density of an object. Thus, a white dwarf star [of which 1 teaspoon of material would outweigh half a dozen -- or thereabouts -- adult elephants] has more mass than Saturn?

Am I getting warmer?

--Cindy

Byron · 2002-07-21 09:22:01

... a white dwarf star [of which 1 teaspoon of material would outweigh half a dozen -- or thereabouts -- adult elephants] has more mass than Saturn?
Am I getting warmer?
--Cindy

Yes, I would say things might be getting a bit toasty for you...lol.

Density is a property of mass...which is why bulk is definately not the same as mass..so you've got the right idea there. A dwarf star..or better yet, a neutron star, is made of highly concentrated mass...bulk concentrated in a very small space. Mass, simply put, is "what's there," which then has properties such as weight in the presence of a gravitational field, and so on. Remember that "weight" is just the result of a force being acted upon matter (gravity). But as Phobos mentioned, we still don't really know why atoms have mass to begin with...we just know that it does..

B

Shaun Barrett · 2002-07-23 02:40:29

Cindy, I think I can cast even more confusion into the discussion!
Mass is one of those things you wrestle with in physics classes until you have enough of an understanding of it to solve the problems they throw at you. But when you really try to analyse what mass is, you start arguing in circles ... mass causes gravity ... mass is independent of gravity ... you need gravity before you can feel the weight of a certain mass ... !!!! It's enough to drive a person to drink! ... Hmmm, maybe that's where I went wrong .. !
I don't think anyone really knows exactly what mass is. The best we can do is say it's a property of matter.This property causes an object at rest to resist being pushed. It also means an object which is already moving resists being slowed to a halt.
This property still exists even when the object is way out in intergalactic space, away from any significant gravitational fields. It is not the same as weight.
For an object to have weight, as well as mass, it has to be in a gravitational field.
To really get a handle on how it all works, I think you have to also consider gravity ... another of those things which people talk about confidently without really knowing how it functions! All we know is that any two objects in the universe exert an attraction on each other. Nobody knows why they should, but they do! As you sit in your chair, Earth is pulling you towards itself and you, in turn, are pulling Earth towards you ... it's a two-way relationship! Actually your chair is pulling both you and Earth towards it, too!! A menage a trois!
Of course your gravitational field and the chair's are minuscule in the extreme; vanishingly small compared to that of Earth.
A gravitational field is really a complete mystery. You can't touch it, taste it, see it or hear it. We don't know how to describe it except by measuring what it does to objects. And what does it do to objects? We've found that it accelerates them. When you dive off a diving board, you accelerate until the water stops you. So, in the absence of any other way to quantify or describe gravity, we just call it an acceleration.
So what's weight, then? Weight is really just the phenomenon you can feel when you STOP two objects from falling towards one another. When you were standing on that diving board, the board was stopping you accelerating towards Earth. Therefore you could feel your own weight ... pushing down on your feet. When you dived, there was no longer anything stopping you accelerating so you felt weightless ... and you were weightless (for a short time! ).
Whether you're standing on the diving board, falling towards the water, or floating out in intergalactic space, your mass is always the same. But you only feel weight when you move your mass into a gravitational field and then deny that field the ability to accelerate you ... by standing on something.
If this discourse has made things worse rather than better, I apologise in advance!!

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#1 2002-06-04 16:17:36

Re: What is mass? - If I knew, I wouldn't ask :)

#2 2002-06-05 03:29:33

Re: What is mass? - If I knew, I wouldn't ask :)

#3 2002-06-05 08:47:41

Re: What is mass? - If I knew, I wouldn't ask :)

#4 2002-06-05 13:07:06

Re: What is mass? - If I knew, I wouldn't ask :)

#5 2002-06-05 21:10:57

Re: What is mass? - If I knew, I wouldn't ask :)

#6 2002-06-06 09:10:13

Re: What is mass? - If I knew, I wouldn't ask :)

#7 2002-06-06 10:44:34

Re: What is mass? - If I knew, I wouldn't ask :)

#8 2002-06-06 20:01:45

Re: What is mass? - If I knew, I wouldn't ask :)

#9 2002-06-12 08:18:10

Re: What is mass? - If I knew, I wouldn't ask :)

#10 2002-06-12 15:41:14

Re: What is mass? - If I knew, I wouldn't ask :)

#11 2002-07-20 10:43:01

Re: What is mass? - If I knew, I wouldn't ask :)

#12 2002-07-20 14:48:23

Re: What is mass? - If I knew, I wouldn't ask :)

#13 2002-07-20 16:38:07

Re: What is mass? - If I knew, I wouldn't ask :)

#14 2002-07-20 16:59:48

Re: What is mass? - If I knew, I wouldn't ask :)

#15 2002-07-21 09:22:01

Re: What is mass? - If I knew, I wouldn't ask :)

#16 2002-07-23 02:40:29

Re: What is mass? - If I knew, I wouldn't ask :)

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