Neil DeGrasse Tyson on "sharing water" with historical figures

In summary, Neil deGrasse Tyson discusses how molecules in air move around the globe and how it is complicated to understand. He also brings up the idea of Avogadro's number and how it is too large for us to understand.
  • #1
willym
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Hello,

I've heard versions of these statements (below) from other scientists, but I've never seen anyone break them down. Do molecules in air really move (diffuse?) their way around the entire globe, or are there localized "pockets" that really don't move that far from home? Intuitively, water seems like it could be even more susceptible to getting stuck in a smaller, localized system. Maybe the real answer I am looking for is, "it's pretty complicated and hard to know, unless you did some studies to mark and track some matter."

Neil deGrasse Tyson - https://neildegrassetyson.com/essays/2007-04-the-cosmic-perspective/

"There are more molecules of water in an eight-ounce cup of the stuff than there are cups of water in all the world’s oceans. Every cup that passes through a single person and eventually rejoins the world’s water supply holds enough molecules to mix 1,500 of them into every other cup of water in the world. No way around it: some of the water you just drank passed through the kidneys of Socrates, Genghis Khan, and Joan of Arc.

How about air? Also vital. A single breathful draws in more air molecules than there are breathfuls of air in Earth’s entire atmosphere. That means some of the air you just breathed passed through the lungs of Napoleon, Beethoven, Lincoln, and Billy the Kid."

Thanks,
William
 
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  • #2
Air travels far and wide (think about the short time it took for radioactive material go from Chernobyl to the farthest reaches of western Europe). Mixing is also quite good.

You are right that water can be localized, but overall, because of evaporation, you end up in the same situation as air.
 
  • #3
willym said:
Maybe the real answer I am looking for is, "it's pretty complicated and hard to know, unless you did some studies to mark and track some matter.
Tyson is basing it on complete mixing.
And on somewhat on an implied instantaneous mixing, since he gives no time frame.

Giving the names of some historical figures from years and years ago, he does have a good chance somewhat of being correct with his statement. For how long ago would his statement hold - 1000 years, 1 year, certainly not a day - with global wind currents churning the atmosphere top to bottom all over the globe - that takes time.

Anyways,
1 mole of substance is 6.022 x 1023 particles.
Air occupies 22.7 L/mole.
Air weighs 28.97g/L
A normal resting breath is about 0.6g.
Thus, each breath is ( 0.6g/breath ) / (28.97g/L ) == 0.0207 L/breath.
and, each breath is ( 0.0207 L/breath ) / ( 22.7L/mole ) == 9.91 x 10-4mole/breath.
Giving, ( 9.91 x 10-4 mole/breath ) x 6.022 x 1023p/mole
= 5.49 x1020particles/breath.

The total air mass is 5.2 x 10 21g
or, ( 5.2 x 1021g )/ ( 0.6 g/breath ) == 8.67 x 1021 breaths .

From that, if my calculations are correct, every 10th breath could have a molecule of air from a particular figure.
Tyson's comment seems to be suspicious, but re-check my calculations to be sure.
 
  • #4
256bits said:
if my calculations are correct
I think your breath volume is low. For radiologic dose calculations, we use 1.2 m^3 per hour ("light work" per 10CFR20.1003). At 15 breaths per minute (900 per hour) that would be 1.33L/breath, vs. your 0.02. So I would say each breath is more like 1.33 L/B * 1.29 g/L or 1.7 grams per breath.

256bits said:
Air weighs 28.97g/L
no, it is 28.97 gram per mole. At 22.7 L/mol and 29 g/mol the air density is ~1.29 g/L.

More importantly for this thread, I think the purpose of the calculation is to show how big Avogadro's number really is. The pop-sci approach is, "nobody understands what 6.022 x 10 23 means." And then goes on to say, "it is so big that your breathing Napoleon's air molecules..." I think it is best to stay with this idea:

There are more molecules of water in an eight-ounce cup of the stuff than there are cups of water in all the world’s oceans.
 
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  • #5
good thing I said check it out.
gmax137 said:
I think your breath volume is low. For radiologic dose calculations, we use 1.2 m^3 per hour ("light work" per 10CFR20.1003). At 15 breaths per minute (900 per hour) that would be 1.33L/breath, vs. your 0.02. So I would say each breath is more like 1.33 L/B * 1.29 g/L or 1.7 grams per breath.
I was using the tidal volume of respiration for idle breathing, and breaths per minute for same.
Exercise and movement would increase both.
 
  • #6
This includes dissociation(s) and recombination(s)? If specific atoms could be labelled, an exercise for the statisticians among us. Given O(m) rates for the processes, I'll wager before putting pencil to back of an envelope that the probability is ten to a large negative number, not infinitesimal, but veerrryyyy small that you inhale the (exact same oxygen molecule to metabolize to water/the exact same water molecule to dissociate carbon dioxide/other metabolic processes) as did Socrates, B the K, Joan of Arc, Abe Lincoln....
 
  • #7
Bystander said:
If specific atoms could be labelled ...
As I understand it, the atoms are identical in the QM sense, so the entire idea that "this" atom was in Socrates is meaningless. As mentioned, the point is only to put a wow factor on how big Avogadro's number really is.
 
  • #8
It's absurd grandstanding for deGrasse to speculate that without proof.

It's like saying Einstein's farts have rejoined to pass thru your nose or that our bodies have more bacteria than stars in the universe which has more cosmic dust, so each of us must have some cosmic bacteria and primordial dust in us. However it is amazing how Earth has been so sustainable up till now.:woot:
 
  • #9
TonyStewart said:
It's absurd grandstanding for deGrasse to speculate that without proof.

That is a nice opinion. Would you like to include some physics in your description of Einstein's farts? Or are you just grandstanding.....
 
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  • #10
hutchphd said:
That is a nice opinion. Would you like to include some physics in your description of Einstein's farts? Or are you just grandstanding.....
No. But agreed, the analogy was also ipso facto absurd.
 
  • #11
My point was a little more subtle.
I can using simple physics (but will not) argue that I am "smelling" the great hip Einie's flatulence as I sit here.
Also we are, as Carl Sagan said, made of starstuff. The heavier elements on earth passed through stars.
So I found your commentary supercilious.

.
 
  • #12
hutchphd said:
My point was a little more subtle.
I can using simple physics (but will not) argue that I am "smelling" the great hip Einie's flatulence as I sit here.
Also we are, as Carl Sagan said, made of starstuff. The heavier elements on earth passed through stars.
So I found your commentary supercilious.

.
I was not intending to sound superior, rather mock the assertions claimed with grandiose names and low probability of meaningful effects.
 
  • #13
TonyStewart said:
I was not intending to sound superior, rather mock the assertions claimed with grandiose names and low probability of meaningful effects.
Yet that same attitude allows people to mock claims about evolution and global climate change as being absurd. I think Dr. Tyson intends it as a lesson in what these big numbers can mean even if it may be counterintuitive.
He is an educator. Why do you feel compelled to mock him?
 
  • #14
Tyson is far from the first person to use this idea. I'm pretty sure it was old when I first heard it 50 years ago. So I wouldn't beat him up too much over it.
 
  • #15
It is obvious that all water must be shared from all living people, fish and mammals in the past. But to assume the consumption , wasted flushed, diffusion, evaporation, precipitation, processing and distribution and with all depths of the ocean that is included in the quantity is more than a super SWAG.

It is important to note that the water you drank has likely undergone various forms of treatment and purification before reaching your cup, which may have removed any traces of evidence having been in anyone else's mouth in the distant past and hopefully all the potential contaminants and learn where it comes from and waste goes and how it gets contaminated , recycled and treated.

It is even more significant for people who live along the Thames to understand they are drinking recycled water mixed with upstream waste. Recycling is more likely localized.

At least cities have standards and test for purity daily unlike the bottled water companies.
 
  • #16
If you cannot positively identify, or tell the difference between individual molecules, then the concept of an individual molecular history is interesting statistically, and quite irrelevant at the same time.

The concept of our containing molecules that have been a part of other people is also interesting. This is a science forum, but we are all subject to the human condition, which brings up the concept of homeopathy, a rational inversion where less is more, and we are each composed of a tiny mix of other's molecules, and so karma. Will the forces of evil out-compete the forces of good? Can I be a truly good person, if I do not have evil thoughts, and resist them? It seems that the symbolic war between the Einsteins and the Hitlers continues conceptually, in the molecules of all of us, and there can be no decontamination. Science is our only escape.
 
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