Discussion
Hi
Is anyone aware of any experiements that have taken place to prove/disprove that a body loses 21 grams when the person dies.
I believe there was one in 1907 but wasn't very scientific which has meant it has become sort of common knowledge / myth.
- Pete
Is anyone aware of any experiements that have taken place to prove/disprove that a body loses 21 grams when the person dies.
I believe there was one in 1907 but wasn't very scientific which has meant it has become sort of common knowledge / myth.
- Pete
Edited by PeterGadsby on Thursday 10th September 08:06
Seem so on be b
ks or "sloppy science" as this site calls it...
http://www.livescience.com/32327-how-much-does-the...
ks or "sloppy science" as this site calls it...http://www.livescience.com/32327-how-much-does-the...
XM5ER said:
How much does a lungful of air and a few farts weigh?
About a gram at sea level on an average day. On such a day, a litre of air will weigh about 1.2g, and the tidal volume of the average person's lungs is about 0.5 litre. I reckon a jolly good fart would equal that, so we could round up to around a gram for both.Edited by RobM77 on Monday 14th September 10:56
Simpo Two said:
RobM77 said:
a litre of air will weight about 1.2kg, and the tidal volume of the average person's lungs is about 0.5 litre. I reckon a jolly good fart would equal that, so we could round up to around a gram for both.
What happened to the other 599 grams?
Nimby said:
I don't think your weight change in air with lungs inflated v deflated.
The extra buoyancy you'd get with inflated lungs exactly matches the weight of air inside you. (OK there may be minute differences due to temperature, pressure, water vapour and O2/CO2)
That's not right, there's a huge difference in buoyancy with full lungs vs empty lungs. The buoyant force an object feels in water is equal to the weight of the water that object is displacing. If you take a full breath, then you'll weigh an extra few grammes due to the increased air inside you, but the weight of that increased bodily volume in terms of water is huge, because water is 800 times denser than air. In other words, the buoyant force is going to be several kilograms full lungs vs empty lungs (2-3 grammes of air taken in, and about ~2kg of extra buoyancy).The extra buoyancy you'd get with inflated lungs exactly matches the weight of air inside you. (OK there may be minute differences due to temperature, pressure, water vapour and O2/CO2)
Sorry for the thread diversion by the way!
In response to the original question, I can't see how anyone can measure a 60-80kg living and breathing person with an accuracy of circa 21 grams - people eat, drink, pee, sweat, digest food, excrete food, grow hair and nails etc etc constantly. Furthermore, the study quoted above had a ludicrously small sample size.
In response to the original question, I can't see how anyone can measure a 60-80kg living and breathing person with an accuracy of circa 21 grams - people eat, drink, pee, sweat, digest food, excrete food, grow hair and nails etc etc constantly. Furthermore, the study quoted above had a ludicrously small sample size.
RobM77 said:
there's a huge difference in buoyancy with full lungs vs empty lungs. The buoyant force an object feels in water is equal to the weight of the water that object is displacing. If you take a full breath, then you'll weigh an extra few grammes due to the increased air inside you, but the weight of that increased bodily volume in terms of water is huge, because water is 800 times denser than air. In other words, the buoyant force is going to be several kilograms full lungs vs empty lungs (2-3 grammes of air taken in, and about ~2kg of extra buoyancy).
I think what you're trying to say is that with a lungful of air, the body's average density is lower. But the mass is effectively unchanged.Simpo Two said:
RobM77 said:
there's a huge difference in buoyancy with full lungs vs empty lungs. The buoyant force an object feels in water is equal to the weight of the water that object is displacing. If you take a full breath, then you'll weigh an extra few grammes due to the increased air inside you, but the weight of that increased bodily volume in terms of water is huge, because water is 800 times denser than air. In other words, the buoyant force is going to be several kilograms full lungs vs empty lungs (2-3 grammes of air taken in, and about ~2kg of extra buoyancy).
I think what you're trying to say is that with a lungful of air, the body's average density is lower. But the mass is effectively unchanged.An object's buoyancy is an upward force equivalent to the weight of water it displaces. So if an object displaces 1 litre (1kg) of water, they'll be an upward force on that object equivalent to 1kg. The downward force is obviously given by the object's mass. If that object displaces 1kg of water but has a mass less than 1kg, it'll float because the upward buoyant force is greater than the downward gravitational force. With regard to a human breathing in, they're taking on a about half a gram of air, so they get half a gram heavier, but because their lungs inflate they're displacing about 800g of extra water, so the buoyant force increases by an amount equivalent to 800g-0.5g.
Note for internet pedants: I'm deliberately trying to avoid a discussion of mass, weight and force in order to write a layman's explanation, thus the use of 'equivalent to'
RobM77 said:
Nimby said:
I don't think your weight change in air with lungs inflated v deflated.
The extra buoyancy you'd get with inflated lungs exactly matches the weight of air inside you. (OK there may be minute differences due to temperature, pressure, water vapour and O2/CO2)
That's not right, there's a huge difference in buoyancy with full lungs vs empty lungs. The buoyant force an object feels in water is equal to the weight of the water that object is displacing. If you take a full breath, then you'll weigh an extra few grammes due to the increased air inside you, but the weight of that increased bodily volume in terms of water is huge, because water is 800 times denser than air. In other words, the buoyant force is going to be several kilograms full lungs vs empty lungs (2-3 grammes of air taken in, and about ~2kg of extra buoyancy).The extra buoyancy you'd get with inflated lungs exactly matches the weight of air inside you. (OK there may be minute differences due to temperature, pressure, water vapour and O2/CO2)
In air, the buoyancy is equal to the weight of air displaced.
Nimby said:
RobM77 said:
Nimby said:
I don't think your weight change in air with lungs inflated v deflated.
The extra buoyancy you'd get with inflated lungs exactly matches the weight of air inside you. (OK there may be minute differences due to temperature, pressure, water vapour and O2/CO2)
That's not right, there's a huge difference in buoyancy with full lungs vs empty lungs. The buoyant force an object feels in water is equal to the weight of the water that object is displacing. If you take a full breath, then you'll weigh an extra few grammes due to the increased air inside you, but the weight of that increased bodily volume in terms of water is huge, because water is 800 times denser than air. In other words, the buoyant force is going to be several kilograms full lungs vs empty lungs (2-3 grammes of air taken in, and about ~2kg of extra buoyancy).The extra buoyancy you'd get with inflated lungs exactly matches the weight of air inside you. (OK there may be minute differences due to temperature, pressure, water vapour and O2/CO2)
In air, the buoyancy is equal to the weight of air displaced.
It was Dr. Duncan MacDougall of Haverhill, Massachusetts who attempted to weigh the human soul. In 1907, he placed 6 dying patients on a homemade scale, which also acted as a bed for the patients. He then recorded their weights before and after death. According to Dr. MacDougall, there was a difference of 21 grams between the heavier, living patients and their dead bodies.
He also experimented on 15 dogs and found no loss of weight between the living dogs and their dead bodies. He believed this was because animals do not have souls.
His experiments were criticized since of the six patients, two tests had to be discarded and the level of error was very high. Obviously, it was not a very scientific study.
In addition, no one has ever been able to repeat the result of these experiments. Basically, there is still no physiological evidence of the soul. It's an urban legend propagated by a guy who did bad science - looking for an answer he already believed was true. Real science doesn't have attachments to preexisting beliefs and values. It just observes and hypothesizes.
It's assumed it was due to improper storage conditions.
He also experimented on 15 dogs and found no loss of weight between the living dogs and their dead bodies. He believed this was because animals do not have souls.
His experiments were criticized since of the six patients, two tests had to be discarded and the level of error was very high. Obviously, it was not a very scientific study.
In addition, no one has ever been able to repeat the result of these experiments. Basically, there is still no physiological evidence of the soul. It's an urban legend propagated by a guy who did bad science - looking for an answer he already believed was true. Real science doesn't have attachments to preexisting beliefs and values. It just observes and hypothesizes.
It's assumed it was due to improper storage conditions.
soad said:
. Real science doesn't have attachments to preexisting beliefs and values. It just observes and hypothesizes.
Not entirely correct it depends on the approach you take, Your comment looks like you are a positivist a definition you will find on wiki is : Positivism is the philosophy of science that positive facts, information derived from sensory experience, interpreted through rational or logical and mathematical treatments, form the exclusive source of all authoritative knowledge; and that there is valid knowledge (certitude or truth) only in this derived knowledge.
Now a constructivist would look at things differently:
the wiki definition is. Constructivism is basically a theory -- based on observation and scientific study -- about how people learn. It says that people construct their own understanding and knowledge of the world, through experiencing things and reflecting on those experiences.
Hmm thats interesting as it starts to reshape how a scientist my look at something....
and it gets more complex how about Interpretative Phenomenological Analysis
Wiki says, Interpretative Phenomenological Analysis (IPA) is an approach to psychological qualitative research with an idiographic focus, which means that it aims to offer insights into how a given person, in a given context, makes sense of a given phenomenon.
So depending on how one approaches a piece of scientific research depends on the Method or Methodology used so Soad I am gently saying in part you are right but there is a much broader approach to science the you mention and also what I have highlighted. but the 21 grams is still carp science
so we probably agree Gassing Station | Science! | Top of Page | What's New | My Stuff