Ah yes.. March 15. As a student of Latin, I felt that i should take time out to explain a few things (well.. one, actually. But to say, “I want to explain one thing” sounds too silly).

The “Ides of March” may sound spooky and ominous to us these days (thank you SO much William), but for the ancient Romans there were only three important parts of the month: The beginning, the middle, and the end. “Ides” is the middle of the month (literally “divide” as, in half). There. Demystified.

Now for something a little cooler

Julius Caesar (for whom the phrase, “Beware the Ides of March” has special meaning) died in March of 44 BC. Our friend Shakespeare penned Caesar’s last words as, “Et tu Brute” (for followers of the link, please note that I did not duplicate the comma. Classical Latin did not use commas), meaning:

“Dear GOD! Not you, my dearest friend! These sniveling senators I expected, but not YOU! We shared a vision, Brutus, we had a future!“

Yes, Latin is quite a powerful language.

Now, how about that last breath of his (he did have one you know. Even if it wasn’t as Shakespeare wrote it :p). How many molecules of that last breath of his do you suppose was in that breath you JUST took??

Lets figure it out, shall we?

Given:

• One breath= 2 liters of air at a pressure of 730 mmHg and 37 degrees Celsius.
• Earth is a sphere with a radius of 6370 Km and an average barometric pressure of 760mm Hg. (D of Hg=13.6g/cm³)
• The avg. molecular mass of air is 29 g/mol.

I. Number of moles in Caesar’s last breath:

1. n = PV/RT = (0.96 atm)(2L)/(0.0821 L atm/mol K)(310 K)
2. n = 0.075 mol

II. Number of moles in the atmosphere:

1. Surface area of earth:
• Area = (4)(p)(r²)
• Area = 5.10 x 10¹⁴ square meters
2. Pressure of the atmosphere on the earth’s surface:
• Pressure = 760 mm Hg = 1.01 x 10⁵ Pascals = 1.01 x 10⁵ Newtons/square meter
• Pressure = 1.01 x 10⁵ kg/m s²
3. Force of the atmosphere on the earth
• Pressure = Force/Area
• Therefore: Force = (Pressure)(Area)
• Force = (1.01 x 10⁵ kg/m s²)(5.10 x 10¹⁴ m²)
• Force = 5.15 x 10¹⁹ kg m /s²
4. Mass of the atmosphere
• Force = (mass)(acceleration)
• Therefore: mass = Force/acceleration
• mass = (5.15 x 10¹⁹ kg m/s²)/(9.8 m/s²) note: this is the acceleration due to gravity
• mass = 5.26 x 10¹⁸ kg or 5.26 x 10²¹ g
5. Moles in the atmosphere
• mol = (5.26 x 10²¹ g)(1 mol/29 g)
• mol = 1.81 x 10²⁰ mol

III. Fraction of atmosphere which represents molecules from Caesar’s last breath:

1. (0.075 mol)/(1.81 x 10²⁰ mol) = 4.14 x 10^-22

IV. Moles of Caesar’s last breath in your last breath:

1. Assume: your breath holds 0.075 mol
2. (0.075 mol)(4.14 x 10^-22) = 3.11 x 10^-23mol

V. Number of molecules:

1. (6.022 x 10²³ molecules/mol)(3.11 x 10^-23mol) = 18.7 molecules

Wow… 18.7 molecules. Now THAT’S science Before you get on my case about the validity of the calculations above, please note that they are taken from an online paper at the Florida State University website, on Molar Mass and Gas Densities. This is their final comment on the matter:

An even more disconcerting fact is that he probably had flatulence as well.

… Beware, indeed.