5 ms·

Just for everyone to have a picture, uranium doesn’t take much room because it is quite heavy: 19.1g/cm3, denser than lead (11.3) but slightly less than gold (1

• fastball 6y ago
  The density of uranium is secondary to just how unbelievably energetic (per unit mass of fuel) fission is.
• loeg 6y ago
  Energy density is the main reason you don't need much volume of uranium. Fission is just extremely energetic. That c² factor in E = m c² is huge (9 * 10¹⁶). It is really hard for humans to intuit about factors of ten to the power of 16 or 17.
  • Jabbles 6y ago
    You need to include the units, else that doesn't make much sense - many physicists use units such that c = 1. In this case the units (for speed²) you want are m²/s² = J/kg
    • loeg 6y ago
      The fun thing is, the units are basically unimportant! A factor of 10^3 or two is peanuts on 10^17. Humans have just as terrible intuitions about 10^14 and 10^11 as they do about 10^17.
      • exporectomy 6y ago
        The error is 10^17, not 10^3. Units are important.