A View from the Back of the Envelope top

J (Joules)
Scale of some things
[ Scale | Other ]

Rough Draft

The universe's massergy comes in two forms, the dense matter, and the very-not-dense energy. We use mass (kg) to count matter, and energy (Joules, J) to count energy.


W·s100exactwatt second
W·h104 × 0.36exactwatt hour
kW·h107 × 0.36exactkilowatt hour
Btu103 × 1.055±<1%there are a couple of flavors
Btu103 × 1.05±1%
Btu103-6%, ±1%
kilocalorie104 × 0.42+<1%
calorie101 × 0.42+<1%, ±<1%various flavors
calorie101 × 0.4-5%
ton TNT1010 × 0.42+<1%
ton TNT1010 × 0.4-4%
eV10-19 × 1.6-<1%electron volt
hc10-25 × 2+<1%unit wave number (?)
amu10-10 × 1.5+<1%
foot-pound100 × 1.36+<1%
foot-pound100 × 1.4+4%
foot-poundal10-1 × 0.42-<1%
term108 × 1.06-<1%
default: [1]
[1] VadeMecum, p7-8
[2] N's scales

Various forms

Joule(m2·kg·s-2)Energy. The potential to do work. Often a potential field with something to ready to fall through it.
force·distance(m·kg·s-2)·(m)A weight waiting to fall some distance.
mass·accel·distance(kg)·(m·s-2)·(m)A mass, trying to accelerate, lifted for some distance, and thus ready to fall.
A mass in motion, reluctant to stop.
mass·c2(kg)·(m·s-1)2 Conversion between the mass and energy flavors of massergy.
W·s(m2·kg·s-3)·sWatt·second: Some time's worth of power.
V·A(m2·kg·s-2·A-1)·(A)Volt·Amp: Some electrons (a current), upstream in a voltage (electric potential difference).
Wb·A(m2·kg·s-2·A-1)·(A)Weber·Amp: Some electrons, upstream in the voltage created by some magnetic flux through the conductor.
Pa·m3(m-1·kg·s-2)·(m3)Pascal·volume: A hunk of some presure or stress.
Coulombs2/Farads: A capacitor, of some roominess (F), with charge (C) stuffed in against itself.

A View from the Back of the Envelope
Comments encouraged. - Mitchell N Charity <mcharity@lcs.mit.edu>


Currently in pre-first-draft state...
  nuclear phase transition requires particle energy order 2 GeV [AmSci '98 SepOct p449]
    Right on edge of oom 1e-9 J.  If turns out to be <2 GeV, should be 1e-10 J.
    I'm not clear on how speculative this model is.  Could check this.
  nucleon excitations: delta 290 MeV, N* 500 MeV [AmSci v86 '98 SepOct p451]

 What a mess.
reorganize pages
backfill derivations
drop 1kg n m
water boiling freezing
your thermal, spinning rotational?, n-story grav potential
room ...
molecule at nK, thermal in general
photon flashlight, sun
joule outward conversions ala Cow?
unit decomposition clusting description
a 10-watt night light produces 10 joules per second
  nuclear density critical-point 0.05 nucleons/fermi^3 at T of ~14 MeV.
    liquid-gas coexistence roughly ~0.09 to ~0.15 below ~10 MeV. [AmSci v86 98sepOct p451]
[AJP v60n6 Jun92 pg576]
  1 jelly donut (JD) = 106 J
  1 kWh = 3.6 JD
  1 flashlight battery (D cell) = 1.6 × 104 J = 0.016 JD
  1 mosquito pushup = 1 erg = 10-13 JD
  1 barrel of oil = 6 × 109 J = 6000 JD
  1 pizza (p) = 107 J = 10 JD (medium, with sausage and pepperoni)
  1 Pizza (P) = 1017 J = 1011 JD (one-half of the energy released
     in the annihilation of a pizza and an antipizza)
[The next few links, to the 1996 CIA factbook, are broken.
  The current factbook is here.]
From [World Factbook 1996]:
  world Electricity: 
   capacity: 2,773,000,000 kW (ie 2.8e12)
   production: 11.601 trillion kWh 
   consumption per capita: 1,937 kWh (1993) 
  US Electricity: 
   capacity: 695,120,000 kW (ie 0.70e12)
   production: 3.1 trillion kWh 
   consumption per capita: 11,236 kWh (1993) 

Metabolism of glucose quoted as 686 kcal/mol.  Sigh.  Ok...
mol is 6.022 × 1023 molecules, and kcal is 4184 J.
So metabolism of a glucose molecule yeilds 0.4766 × 10-17 J.

US per capita primary energy consuption is ~220 million Btu.
specific heat capacity (J/kgK) water 4200 J/kgK.  (3000 soup)
thermal potato (warm hands, high water content)
population density vs gasoline consumption[link broken]
  2003-Feb-04  Flagged 4 broken links.  Added 1.
  1998.Sep.15  Added nucleus vaporization energy, keV to TeV.
  1997.Aug.21  Added metabolism of a glucose molecule.