-
Asked by naomibrereton to Enda, Jean, Kate, Kev, Tim on 9 Nov 2012.
-
Jean Bourke answered on 9 Nov 2012:
That sound like a complicated maths problem. It is Friday evening and I’m tired, also maths isn’t my area. For now I will say that, unfortunately, there is no patron saint of physics 🙁 so technically the answer is none 😉 but I assume you mean by any other given person which I suppose can be worked out. For now though I think we can start looking for a patron saint of physics. Here in chemistry we could do with one too so we have someone to pray to when stuff goes wrong!
According to wikipedia “a saint is one who has been recognized for having an exceptional degree of holiness, sanctity, and virtue” so be on the lookout!
-
-
Enda O'Connell answered on 13 Nov 2012:
Hi Naomi
This type of calculation has been done for water molecules, and it is estimated that during your lifetime you will drink at least one molecule of water twice. From that, you can say that you will probably drink a molecule of water that has been drunk by anyone in history, such as Einstein, Julius Caesar or even a T. Rex!
Comments
naomibrereton commented on :
oh okay thanks for taking the time to answer my question anyway i appreciate it what about the question without the pattern saint of phissics?? hope u get to answerthanks….
Jean commented on :
Right, I’ve spent some time with google and a calculator and this is what I have so far:
The average life expectancy in Ireland is 78.9 years.
78.9 X 365 X 24 X 60 = 41469840 minutes/life
But this doesn’t include leap years. 78.9/4 = 19.725 leap days
19.725 X 24 X 60 = 28404 minutes due to leap days.
Add these together and you get 41498244 minutes/life.
There’s loads of info on how may breaths/minute. Basically the younger you are, the more breaths you take. For the sake of (relative) simplicity let’s say the more breaths is cancelled out by the smaller lungs. An adult takes 12-20 breaths a minute.
Average= 16 breaths/minute
Average breath volume = 0.5L
-> 8L/minute
Putting this all together:
41498244minutes X 8L/minute = 331985952L/life
The density of the earth’s atmosphere is not constant (less dense the higher you go) so can’t use volume to compare coz we’re at (about) sea level.
Weight of the atmosphere = 5.1480^18kg =5.1480^21g.
I need to use a unit called a mole for this bit. A mole related the weight of something (its mass) and how many molecules there are. Bear with me, if you need me to explain a mole ask me separately coz it’ll take too long here.
Taking into account the different things in the atmosphere and their percentages (and rounding off to make my life easier), the molar mass of the atmosphere is 29g/mole
So if you divide the weight by the weight/mole you get the number of moles:
(5.148^21) /29 = 30339701594706 moles of “air” in the atmosphere.
Now we need the number of moles that someone breathes in a life time.
At 25 degrees Celsius 1 mole of any gas will occupy 24L
(331985952L/life) / (24L/mol) =13832748 moles/life
And this is where I get stuck. I don’t know how to work out much else.
I can tell you that, based on the above calculations, and assuming you don’t rebreathe any of your previous molecules and that the composition of the atmosphere is constant (i.e. plants don’t use up CO2 and make O2 and we don’t use up O2 and make CO2) then over the average lifetime and Irish person will breathe in 0.00004559% of the atmosphere.
Phew.
If anyone can take the next step in the calculations that would be great.
Jean commented on :
Actually I seem to have made a mistake in calculating the number of moles in the air. It’s actually 1775172414^20 which means that the % at the end should be 7.79^-21%
naomibrereton commented on :
Hey wow thanks… I apresiate the time And effort u put in to answer this question i really do apresiate it and am very intrested in this topic thanks again