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V'neef Massoud
05-27-2006, 04:54 AM
can somebody think of a easy way of determining the weight of my head ?

without removing it from the neck

gabriela
05-27-2006, 05:13 AM
I can't weigh your head, but I can tell you what a human head weighs once it is disconnected from the neck.

Ten pounds.

I work in forensics and we occasionally get a body in which, er, circumstances have separated the head from the rest. We weigh it.

Sage Rat
05-27-2006, 06:39 AM
But what if you died pondering weighty subjects? :)

But really, if you lie down on the ground and rest your head on a measuring thing, that should be pretty close once you have relaxed for a while. Of course you will need someone else to watch the meter.

And of course if it isn't around ten pounds, then I guess we know that this method doesn't work.

Wallenstein
05-27-2006, 07:36 AM
Get a bucket.

Weigh it. (x)

Fill it with water.

Weigh it again. (y)

Weigh the bucket. (z)

The human head is mostly brain. Brain is mostly water. Water has a density of 1kg per litre at 4C.

So the amount of water displaced is (give or take) the weight of your head.

(The average male head weighs 4.25kg)

spingears
05-27-2006, 07:40 AM
can somebody think of a easy way of determining the weight of my head ? without removing it from the neckWould this do the job?
1. Draw a line around your neck at the point where it leaves off and your head begins.
2. Plug you nostrils and be suspended over a tank of water with a scale in the suspension line.
3. Take weight in air.
4. Be lowered into the water up to the line.
5. Take weight with head in water and measure the water displaced.
5. Calculate.

So maybe not as easy as others suggested but more accurate.

bonzer
05-27-2006, 07:54 AM
Ah, the "how can you weigh a head?" quagmire ...

About 15 years ago the Notes & Queries column in the Guardian carried this question. (N & Q is a sort of low-grade version of GQ; they don't put the newspaper version online, but they do have a similar section on their website (http://www.guardian.co.uk/notesandqueries/0,,184276,00.html).) This prompted a long-running heated debate over multiple morning coffees in the theoretical physics group where I was a grad student at the time. Several of those who chipped in were FRSs. The result: "how can you weigh a head?" became the department's stock joke example of a simple physics question that nobody can agree on.

Several obvious possible answers were quickly deemed unsatisfying. Sage Rat's suggestion will quite possibly give a reasonable experimental result, but there's the feeling that it's an example of essentially appealing to the head being effectively disconnected under particular conditions.
However, the big obstacle that you keep running up against is density variations. For instance, as the other posts have recognised, the problem is trivial if we assume that the human body is of uniform density throughout: measure the overall weight and volume and then the volume of the head. Again, this assumption may be good in practice, but there was the counter-argument that this is just an accident of the circumstances. Generalise the problem to arbitrary distributions of mass with arbitrary shape, with the human body and its head as a special case, then these sorts of assumptions become useless. What was interesting - and part of the reason the debate got quite heated at times - was that even professional physicists could get rather entrenched in incorrectly arguing that their current suggestion - usually involving levers and buckets of water - managed to avoid these assumptions.
Naturally, people then appealed to X-rays and the like. (I think it was me who jokingly suggested gravitational lensing.) These methods can certainly get a handle on the density variations, but nobody ever managed to construct an elegant method that was obviously able to answer the general question.

Some of us did wind up conjecturing that there was some impossibility theorem along the following lines: given an arbitrary rigid mass there's no mechanical method of determining the mass on one side of an arbitrary plane. But nobody ever bothered trying to formalise this.

Of course, this was a bunch of theorists arguing. Though it's an interesting example of how in certain circumstances theoretical physicists will happily simplify a problem to get an answer, while in others they will argue that making a similar assumption - while maybe reasonable in practice - misses the interesting version of the problem.

Shalmanese
05-27-2006, 08:30 AM
Have a spring connected to a newton meter on one end and your head on the other. Record the force downwards suspended in mid air and then the force downward with your head dunked in water. Based on the difference of the two, it should be possible to work out how bouyant your head is and , along with the displacement, how much it weighs.

Beware of Doug
05-27-2006, 08:53 AM
Get a bucket.

Weigh it. (x)

Fill it with water.

Weigh it again. (y)

Weigh the bucket. (z)

The human head is mostly brain. Brain is mostly water. Water has a density of 1kg per litre at 4C.

So the amount of water displaced is (give or take) the weight of your head.

(The average male head weighs 4.25kg)

And if you have a few apples, you can weigh them, subtract the total from the equation and BOB FOR APPLES! :D

Mangetout
05-27-2006, 09:52 AM
Get a bucket.

Weigh it. (x)

Fill it with water.

Weigh it again. (y)

Weigh the bucket. (z)

The human head is mostly brain. Brain is mostly water. Water has a density of 1kg per litre at 4C.

So the amount of water displaced is (give or take) the weight of your head.

(The average male head weighs 4.25kg)
Someone can perhaps correct me on this, but I was under the impression that a considerable proportion of the bran was composed of fat.

Mangetout
05-27-2006, 09:53 AM
Brain :smack: obviously bran isn't made of fat.

MonkeyMensch
05-27-2006, 10:06 AM
I don't know if this thread is apporopriate for GQ: calling people fat-heads and telling them to go stick their heads in a bucket.

Since the skull has some substantial air pockets too (sinuses, airways and esophagus) my guess is that that lowers density even farther.

Wallenstein
05-27-2006, 11:01 AM
I took my info from the New Scientist - they were asked the same question and that's the method they suggested.

Weighing a head will never be easy as it's attached to the rest of the body - finding the volume and then using average compositional data is probably the nearest you're gonna get from a home experiment.

Wallenstein
05-27-2006, 11:10 AM
Brain :smack: obviously bran isn't made of fat.
Intracranial contents by volume
Whole Brain (1,700 ml, 100%):
brain = 1,400 ml (80%);
blood = 150 ml (10%);
cerebrospinal fluid = 150 ml (10%)

(from Rengachary, S.S. and Ellenbogen, R.G., editors, Principles of Neurosurgery, Edinburgh: Elsevier Mosby, 2005)

Composition of Brain
Whole Brain (%):
Water 77 to 78
Lipids 10 to 12
Protein 8
Carbohydrate 1
Soluble organic substances 2
Inorganic salts 1

(Reference: McIlwain, H. and Bachelard, H.S., Biochemistry and the Central Nervous System, Edinburgh: Churchill Livingstone, 1985)

(Just need the proportion of the head that the skull makes up...)

ratatoskK
05-27-2006, 11:14 AM

Annie-Xmas
05-27-2006, 11:22 AM
can somebody think of a easy way of determining the weight of my head ?

without removing it from the neck

Find someone of a similar build and head size as your own.

Weigh it.

L. G. Butts, Ph.D.
05-27-2006, 12:01 PM
As others have mentioned using water diplacement to measure volume and assuming that the body has a uniform density is the easiest. I don't know how close to the real answer you will get using this method, though I imagine it would be good enough for government work...

Could something be done with moments of inertia? Stand on a freely rotating like a mery go round. Measure the rotation speed. Tilt your head forward known amount. Measure change in rotation speed. Repeat. Do lots of numerical simulations/integrations changing head mass parameter until the data matches the experiment.

Mangetout
05-27-2006, 08:32 PM
Intracranial contents by volume
Whole Brain (1,700 ml, 100%):
brain = 1,400 ml (80%);
blood = 150 ml (10%);
cerebrospinal fluid = 150 ml (10%)

(from Rengachary, S.S. and Ellenbogen, R.G., editors, Principles of Neurosurgery, Edinburgh: Elsevier Mosby, 2005)

Composition of Brain
Whole Brain (%):
Water 77 to 78
Lipids 10 to 12
Protein 8
Carbohydrate 1
Soluble organic substances 2
Inorganic salts 1

(Reference: McIlwain, H. and Bachelard, H.S., Biochemistry and the Central Nervous System, Edinburgh: Churchill Livingstone, 1985)

(Just need the proportion of the head that the skull makes up...)Hmmm... I can't cast doubt on your cite of obvious authority, however, I'm surprised the percentage of fat is so low; I'm reading in lots of different places (none of which I feel particularly worthy of citing here, and all of which may be simply quoting each other) that the brain is composed of 60% structural fat.

05-27-2006, 08:37 PM
Oh, Cecil...

robardin
05-27-2006, 11:22 PM
I don't get it. As ratatoskK also asked, why can't you just do something equivalent to lying on a couple of gym mats stacked to about a foot's height with your neck on the edge, and putting your head on a plate resting on a scale?

WTP?

Klaatu
05-27-2006, 11:48 PM
Well, a cursory google of "weight of a human head" shows some answers of 4 to 6 kilograms, which appears to somewhat agree with Gabriela.

If you go through the results, they pretty much end up at a ballpark figure of around 10-12 pounds.

Klaatu
05-27-2006, 11:52 PM
Pardon, there was a dead link to a New Scientist article in which they used the water displacement method to come up with a weight of 4.25 kilos.

gazpacho
05-28-2006, 12:10 AM
Well, a cursory google of "weight of a human head" shows some answers of 4 to 6 kilograms, which appears to somewhat agree with Gabriela.

If you go through the results, they pretty much end up at a ballpark figure of around 10-12 pounds.Do y'all remember that mad magazine cartoon about how to get rid of ten pounds of ugly fat?

05-28-2006, 12:19 AM

I couldn't find any references for this online, so I asked around my workplace (the Department of Anatomy & Histology, University of Sydney). The most convincing response came from the service room where the technical officers actually cut up the bodies:

"An adult human cadaver head cut off around vertebra C3, with no hair, weighs somewhere between 4.5 and 5 kg, constituting around 8% of the whole body mass."

Shalmanese
05-28-2006, 12:48 AM
Have a spring connected to a newton meter on one end and your head on the other. Record the force downwards suspended in mid air and then the force downward with your head dunked in water. Based on the difference of the two, it should be possible to work out how bouyant your head is and , along with the displacement, how much it weighs.

Anyone willing to point out why my method won't work?

Princhester
05-28-2006, 03:11 AM

Mangetout
05-28-2006, 04:02 AM
Further investigation seems to indicate that the various sources stating that the braoin is 60% fat are mirepresenting a statistic.
Myelin, the material of which neural tissue is composed, is apparently around 60% structural fat, but of course not all of the brain is made of myelin.

bienville
05-28-2006, 05:20 AM
Now, if my head were veal, which I know it is not, if my head were veal, how much would it be worth?

Wallenstein
05-28-2006, 05:34 AM
The correlation between skull measurements and the true brain weight can be expressed by the formula:

brain weight, g = (21.8 x axial circumference, cm) + (13.9 x transversal circumference, cm) + (2.105 x length x width, cm) - 890.

The mean brain weight as calculated by this formula was within 1.5% of the true weight in the male and within 0.08% in the female cadavers examined.
(Determination of human brain weight in vivo by skull measurements - Brunholzl C, Widmer AC, Buser MW, Muller HR.; Neurologische Universitatsklinik, Kantonsspital Basel, Schweiz.)

Still can't find either:

1) average weight of human skull (have seen unreferenced claim of 2.2lbs)
2) proportion of total weight of head represented by the skull

Richard Pearse
05-28-2006, 06:15 AM
Don't know what's so difficult about this one, just weigh the torso, legs and arms, then weigh the entire body, remove the combined weights of the torso, legs, and arms and hey presto! You are left with the weight of your head.

Xema
05-28-2006, 01:32 PM
I believe Shalmanese is proposing to measure both the volume of the head and the loss of measured weight caused by submerging it in water. It seems that this would allow the specific gravity and thus the weight to be determined.

Princhester
05-28-2006, 06:49 PM
OK then but that can only be done if you can measure the loss of bouyancy precisely. Which you can't because the head is attached to the neck, which is going to make your measurements imprecise. If this problem didn't exist, this whole question would be very simple.

Bosda Di'Chi of Tricor
05-28-2006, 06:56 PM
I can't weigh your head, but I can tell you what a human head weighs once it is disconnected from the neck.

Ten pounds.

I work in forensics and we occasionally get a body in which, er, circumstances have separated the head from the rest. We weigh it.

And then, you make it wear a hat.

You do!
:D

Sam Stone
05-29-2006, 01:18 AM

You put a person in a big test tube. You attach just enough weights to his feet that the body floats just below the chin. Then add weight in small increments until the head submerges. The weight added is the difference between the weight of the head and the weight of an equivalent volume of water. Measure how much the water rises, and you have the volume of water displaced by the head submerging. Subtract the added weight from the weight of the displaced water, and you have the weight of the head.

(This assumes that the head floats)

Crescend
05-29-2006, 03:46 AM
Computed tomography can quantitatively measure tissue density, with every voxel in the image has an associated Hounsfield number.

So:

Take one (1) head, preferably attached to one (1) body.

Place head into bore of one (1) high-resolution CT scanner.

Scan head entirely, use voxel Hounsfield numbers to figure out all tissue densities.

Use water bucket procedure to determine head displacement.

Use tissue densities and displacement to determine mass.

Shalmanese
05-29-2006, 08:20 AM
OK then but that can only be done if you can measure the loss of bouyancy precisely. Which you can't because the head is attached to the neck, which is going to make your measurements imprecise. If this problem didn't exist, this whole question would be very simple.

Re-read what I posted. You hold a person upside down over a bucket of water and attach a newton meter to their feet. You can measure the the weight precisely and the neck muscles wont interfere.

Princhester
05-29-2006, 06:45 PM
Imagine a rigid dummy with a head made of a hollow fibreglass sphere. Imagine a rigid dummy with a head made of lead. Each head is precisely the same volume. Now do your upside down dunking trick. In each case, the head will displace precisely the same amount of water, and the reading on the newton meter will decrease by precisely the same amount. Yet the head weights are going to be totally different.

To measure the difference in bouyancy, you would need the head to be free to float/sink and find its own level but this is not going to be precisely possible when it is attached to a neck.

Majikthise
05-29-2006, 07:00 PM
Have a spring connected to a newton meter on one end and your head on the other. Record the force downwards suspended in mid air and then the force downward with your head dunked in water. Based on the difference of the two, it should be possible to work out how bouyant your head is and , along with the displacement, how much it weighs.

If you suspend a person upside down from a newton scale with just their head underwater, the forces on the system are (besides the reaction force from the scale):
* the force of gravity on the person (downwards)
* the buoyant force from the water (upwards)

The problem is that the buoyant force does not equal the weight of the head, it equals the weight of the displaced fluid, i.e. the volume of the head times the specific weight of water. You can use this setup to calculate the volume of someone's head, but unfortunately not its weight.

Chronos
05-29-2006, 08:34 PM
I think bonzer has it correct:Some of us did wind up conjecturing that there was some impossibility theorem along the following lines: given an arbitrary rigid mass there's no mechanical method of determining the mass on one side of an arbitrary plane. But nobody ever bothered trying to formalise this.That is, of course, provided that measurements of the gravitational field are excluded (also suggested by bonzer, in his gravitational lensing comment). I think that the proper approach to rigor here is to first demonstrate that the moment of inertia tensor contains all of the information which can be mechanically determined about an object's mass distribution, and then to note that there are an infinite number of possible mass distributions for any given moment of inertia tensor, with different "head masses" associated with them.

Note, however, that this assumes a rigid object, which a human body is not. Eyer8's suggestion of measuring moment of inertia with head and neck in various configurations should in principle give fairly good results, given some simplifying assumptions about the biomechanics of how the head moves. We do still need those simplifying assumptions, though: One could in principle, for instance, have most of the mass of the head concentrated in a small lump rigidly attached to the torso, with a hollow shell of a head of negligible mass moving around it. In this case, moving the head would not change the moment of inertia of the body, indistinguishable from the case where the entire head is of negligible mass.

And of course, if we're going to settle for pretty good approximations given the human body, then the uniform-density method and the cadaver method are both much simpler than any measurement of moment of inertia.

FordPrefect
05-29-2006, 09:42 PM
Now, if my head were veal, which I know it is not, if my head were veal, how much would it be worth?
That's the joke I came in here to make :)

bienville
05-29-2006, 09:44 PM
That's the joke I came in here to make :)
Awwww, and I thought it had gone completely unnoticed. You just made my night!

MonkeyMensch
05-29-2006, 09:50 PM
... the entire head is of negligible mass...
And now we haveChronos calling people airheads! Can't we all just get along?

To put a different spin on the problem couldn't we rotate the person horizontally face up at a number of different pivot points? The changing moments of inertia should give us a distribution of mass along the longitudinal axis and we could then tell what portion of mass was above the neck.

Zulema
05-29-2006, 10:00 PM
Did anyone else lie on a scale yet to see what measurement they got?

I got ten pounds and my husband got 8, this is no matter how far up we positioned our heads on the scale.

Mangetout
05-30-2006, 02:33 AM

You put a person in a big test tube. You attach just enough weights to his feet that the body floats just below the chin. Then add weight in small increments until the head submerges. The weight added is the difference between the weight of the head and the weight of an equivalent volume of water. Measure how much the water rises, and you have the volume of water displaced by the head submerging. Subtract the added weight from the weight of the displaced water, and you have the weight of the head.

(This assumes that the head floats)This sounds promising, except that the subject breathing in and out affects his buoyancy, and even if that wasn't a problem, I think you'd have to allow the above described system to settle for a number of minutes before being sure you had some kind of accurate measurement. So instead of decapitating the subject in order to weigh the head, you have to suffocate or drown him.

Sam Stone
05-30-2006, 03:13 AM
It's the price you pay for science, man.

Ellis Dee
05-30-2006, 03:36 AM
Get a bucket.

Weigh it. (x)

Fill it with water.

Weigh it again. (y)

Weigh the bucket. (z)

(y-x) - (z-x) = your headWhat is the point of x? Obviously, it's not needed based on the final calculcation, but what is the thinking behind introducing it in the first place?

(y-x) - (z-x) = y - x - z + x = y - z + x - x = y - z

Wallenstein
05-30-2006, 06:11 AM
What is the point of x? Obviously, it's not needed based on the final calculcation, but what is the thinking behind introducing it in the first place?

(y-x) - (z-x) = y - x - z + x = y - z + x - x = y - z

yup, fair point :)

CalMeacham
05-30-2006, 06:58 AM
As I've mentioned before on this Board, there have been a number of studies correlating the mass (and raxdius of gyration, and other such biomechamical data) of body parts with easily measurable dimensions (such as diameter of the neck). These measurements were performed on corpses, which were then cut up and measured. They found the parameters for which there were high correlations and computed formulae thatr could be used to determine the physical peopetrties of bodies so you don't have to cut them up -- you could get a reasonably good value for the weight of yopur head by measuring (as an example -- I dobn't know if these are the measurements with high correlations) neck diameter, nose-to-chin distance, and circumfeence around the temples, then plugging these into the appropriate formyulas.

Where are the formulas? You'll have to look them up in books and journals on Biomechanics. I haven't got the data here. The earliest ones were by Wilfrid T. Dempster at Wright-Patterson Air Force Base in the late 1950s or 1960s. They were looking at space requirements for operators (especially pilots). You can find stuff in the proceedings of the Stapp Car Crash studies, too.

I know there have been studies since. An updating of Dempster's data took place in the 1970s, and I don't doubt they've refined it since then.

Jake4
05-30-2006, 08:40 AM
In some of the above posts, there are statistics cited on weight of the brain.

Don't forget about the skull. (and cartilige, skin, etc.)

Lionne
05-30-2006, 09:29 AM

Amaranta
05-30-2006, 11:51 AM
That's the joke I came in here to make :)

Darn you both. That was my joke to make!

jawdirk
05-30-2006, 12:19 PM
This sounds promising, except that the subject breathing in and out affects his buoyancy, and even if that wasn't a problem, I think you'd have to allow the above described system to settle for a number of minutes before being sure you had some kind of accurate measurement. So instead of decapitating the subject in order to weigh the head, you have to suffocate or drown him.

I think Sam Stone got it, basically. The subject can breath through a thin plastic tube with negligible weight. The subject can hold his breath while the measurement is made, and I think you could pull it off in that amount of time. The subject doesn't have to be submerged in pure water. Something denser would work better (I can't keep my head above water without treading water).

KlondikeGeoff
05-30-2006, 12:56 PM
OK, after snorting over all the absurd humor and pondering the weird science, I am left with one question, that for some reason has not been asked:

V'neef Massoud Why in hell would you possibly want to know??????

jawdirk
05-30-2006, 01:36 PM
V'neef Massoud Why in hell would you possibly want to know??????

It's the first step in the process of weighing your options.

handsomeharry
05-30-2006, 01:39 PM
You could remove your neck from your head. I know that this is a trivial difference from the OP, but I think that science is best served by doing first, and then debating later!

hh :cool:

Don Logan
05-30-2006, 02:16 PM
Thanks bienville, for reminding me of my favorite Gavin sketch, and second overall to "Feelyaat!". I haven't thought of that in ten years!

Bruce: How much do you think my head weighs?

Kevin: [disbelieving] What!?!

Bruce: How much do you think my head weighs. Like if I weighed it on the scale, you know if the angle was right?

Kevin: With or without hair?

Bruce: With. [rolls eyes as if to say 'Duh']

Kevin: Twelve pounds.

Bruce: Now, if my head were veal, which I know it is not, if my head were veal, how much would it be worth?

Kevin: Fifty four dollars.

Bruce: [Mulls it over a moment] No, I don't think I'll sell.

bienville
05-30-2006, 03:02 PM
Darn you both. That was my joke to make!

And you thought you'd be able to make it at Post#50???

I was actually very surprised that it hadn't been made before my Post#27!

Don Logan thanks for posting the whole exchange!

Chronos
05-30-2006, 03:26 PM
Just to reiterate, no method based on buoyancy will work. All you can measure from buoyancy is the volume of the head, not its weight. The more complicated variations of the buoyancy experiments basically boil down to "Measure the volume of the head, then measure the volume, then measure the volume, then steal underpants. From these three measurements, solve for the mass of the head".

Don Logan
05-30-2006, 04:00 PM
bienville, the entire sketch can be found here:

http://www.kithfan.org/work/transcripts/two/gavbutcher.html

jawdirk
05-30-2006, 05:42 PM
Just to reiterate, no method based on buoyancy will work. All you can measure from buoyancy is the volume of the head, not its weight. The more complicated variations of the buoyancy experiments basically boil down to "Measure the volume of the head, then measure the volume, then measure the volume, then steal underpants. From these three measurements, solve for the mass of the head".

I thought about this for a while, and I think I understand why this is true. Whether the head is above or below the water line doesn't matter, because the density of the whole person (plus weights you attach) determines where the water line is.

Can you debunk this idea?

Put the person on a flat plank with a movable lever line. Measure the torque on one end of the plank continuously as you move the lever line from the top of the person's head to the bottom of their feet. From this data curve, infer how the weight is distributed from the neck up relative to the rest of the body.

jawdirk
05-30-2006, 05:52 PM
Can you debunk this idea?

Put the person on a flat plank with a movable lever line. Measure the torque on one end of the plank continuously as you move the lever line from the top of the person's head to the bottom of their feet. From this data curve, infer how the weight is distributed from the neck up relative to the rest of the body.

Ah, I figured this one out too. The curve comes out very linear :smack:

Crafter_Man
05-30-2006, 09:48 PM
Just to reiterate, no method based on buoyancy will work. All you can measure from buoyancy is the volume of the head, not its weight. The more complicated variations of the buoyancy experiments basically boil down to "Measure the volume of the head, then measure the volume, then measure the volume, then steal underpants. From these three measurements, solve for the mass of the head".But let's say I divided the head up into a bunch of small cubes (e.g. 1 cm x 1 cm x 1 cm). And I knew the density of each cube. Could I then calculate the mass of the head after the overall volume is measured?

If so, then all you have to do is "divide" the head up into a bunch of small cubes and measure the density of each cube. Is there a technology that will do this? X-Ray? MRI?

Pasta
05-31-2006, 07:29 AM
If so, then all you have to do is "divide" the head up into a bunch of small cubes and measure the density of each cube. Is there a technology that will do this? X-Ray? MRI?
One still needs assumptions about the isotopic composition of the head. X-rays, for example, only measure the proton (or, equivalently, electron) density. A block of carbon-12 and a block of carbon-13 look the same to an X-ray, but one is 8% more dense. Even assuming typical isotopic ratios for each element, one still needs to know the elemental composition since the proton-to-neutron ratio is not the same for all elements.

Muon radiography was another thing I toyed with here, but it has the same proton/neutron problem, as muon scattering depends only on the density of the protons.

One thing that is immune to this problem is neutron scattering. Neutrons are agnostic to whether they bounce off a proton or a neutron. However, it's pretty tough to measure the outgoing neutrons, and one would need to average over much more than a lethal dose's worth of data to get anything competitive.

CalMeacham
05-31-2006, 07:56 AM
Here's a good source from 1969, although I think it's been superceded:

" Charles E. Clauser " # "and" #

" John T. McConville " # "and" #

" John W. Young "
,

title = "{
Weight, volume, and center of mass of segments of the human body
}",

institution = " Aerospace Medical Research Laboratory (AMRL) ",

type = " Technical Report ",

number = " AMRL-TR-69-70 ",

year = " 1969 ",

keys = " biomechanics, antropometry, body model, data "

Chronos
05-31-2006, 03:24 PM
But let's say I divided the head up into a bunch of small cubes (e.g. 1 cm x 1 cm x 1 cm). And I knew the density of each cube. Could I then calculate the mass of the head after the overall volume is measured?Heck, if you divided the head up into one head, that'd work, too, if you knew the density.

And on further thought, I'm not sure that even measuring the gravitational field would be enough, unless you had some means of probing the field inside the head as well as out (gravitational lensing of some sort of penetrating radiation might work). Suppose you took a person of uniform density. Now take a sphere of that material in the neck, with center just below the cut plane. Shrink that sphere down to a smaller uniform sphere with the same mass. You've just removed some mass from the head, without changing the gravitational field anywhere outside the original sphere. Nor the moment of inertia, nor buoyancy, for that matter.

06-02-2006, 11:44 AM
I think Sam Stone got it, basically. The subject can breath through a thin plastic tube with negligible weight. The subject can hold his breath while the measurement is made, and I think you could pull it off in that amount of time. The subject doesn't have to be submerged in pure water. Something denser would work better (I can't keep my head above water without treading water).If you perform a tracheotomy on the subject, you don't even need to rig up a complicated breathing mechanism. Hey, maybe Anthony Federoff has a useful career ahead of him after all!

Elendil's Heir
06-02-2006, 12:19 PM
Now, if my head were veal, which I know it is not, if my head were veal, how much would it be worth?

All right, I'll admit it. I don't get this. A song lyric? Internet subculture in-joke?

Harmonious Discord
06-02-2006, 01:13 PM
There's a distintion between calculate or extrapulate the weight of my head, and actualy weighing my head.

Amaranta
06-02-2006, 01:14 PM
All right, I'll admit it. I don't get this. A song lyric? Internet subculture in-joke?

Psst... post #58. A little bit of Canadiana for you.

Elendil's Heir
06-02-2006, 01:49 PM
Ooops - thanks! I'd overlooked that.

davidm
06-02-2006, 08:06 PM
Find someone of the same gender and approximately same age as you who has no bone wasting diseases (unless you do) and who has a head slightly larger than yours (to make sure we don't come up short) and hair similar to yours (in thickness) but longer than yours (I'm assuming you want to measure the hair since it is part of your head). Make sure that they don't have any glass eyes or other prosthetics (unless you do). Make sure that they have the same number of teeth as you. Cut their hair to the same length and style as yours.

Now make a plaster mold of your head. After the mold dries, weigh it. Call this weight y. Now remove the head of the person you found. Without letting it drain, put it into some sort of powerful blender smasher thing which will render a completely homogenized pulp which is of equal density throughout. Fill the plaster mold with the pulp. There should be a little left over since we started with a slightly larger head. Weigh the pulp filled mold. Call this weight x.
x - y should be a good approximation of the weight of your head.

Saltire
06-03-2006, 08:55 PM
Fill the plaster mold with the pulp. There should be a little left over since we started with a slightly larger head. Weigh the pulp filled mold. Call this weight x.
x - y should be a good approximation of the weight of your head.Actually, since your method creates a mechanical average of head-density, if you had trouble finding a head slightly larger you could just use two heads. You would just end up with more leftovers.

davidm
06-03-2006, 09:07 PM
Actually, since your method creates a mechanical average of head-density, if you had trouble finding a head slightly larger you could just use two heads. You would just end up with more leftovers.True, but now that I think about , I'm not sure that this method would work too well any way. It doesn't account for air pockets such as in the sinuses, mouth, nose, ears, etc. Those would have to be accounted for somehow. The only way I can think of would be to fill your mouth, sinuses ears, nose, etc. with some of the pulp then remove it, weigh it, and substract that weight from your final x - y value.

n0disguise
06-04-2006, 02:17 AM
Couldn't you probably get a pretty accurate measurement by putting your head in a bucket of blended head to see how much it displaces, then weighing the displaced blended head?

kanicbird
06-04-2006, 05:56 AM
What about using rotational inertia, spinning the body along different axis'?

MonkeyMensch
06-04-2006, 09:49 AM
Couldn't you probably get a pretty accurate measurement by putting your head in a bucket of blended head to see how much it displaces, then weighing the displaced blended head?
Now this I rully, rully like, if only for the notion of blended head. Just make sure it's only blended and not puréed so it retains the proper proportion of air pockets and voids. Should have a nice heady aroma, though.

davidm
06-04-2006, 02:05 PM
Couldn't you probably get a pretty accurate measurement by putting your head in a bucket of blended head to see how much it displaces, then weighing the displaced blended head?Possibly, but this still doesn't account for the air pockets.

billfish678
06-05-2006, 08:11 AM
Hi guys...

Really neat physics problem here.

I THINK I came up with a good way, but I will have to double check my math first.

This is physics at its best.

Simple method, probably as accurate as anything else you could do, and MUCH easier than all those fancy, smancy high tech methods. And you dont even have to measure how much water is displaced.

I'll double check my math and hopefully post the answer in a day or two

take care

Blll

Elendil's Heir
06-05-2006, 10:10 AM
....Should have a nice heady aroma, though.