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Admetus@sopuli.xyz ⁨2⁩ ⁨months⁩ ago

• lvxferre@mander.xyz ⁨2⁩ ⁨months⁩ ago

  You certainly know it, but sharing it for the ones who don’t:

  The full equation is E² = (pc)² + (m₀c²)² where E, p, c, m₀ are respectively: energy, momentum, the speed of light, inertial mass. The (pc)² part is kind of a big deal, because otherwise massless particles (like photons) would have no energy.

  If p = 0, then the equation simplifies into that famous E=mc².

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  • Karyoplasma@discuss.tchncs.de ⁨2⁩ ⁨months⁩ ago

    What I think is funny is that if you assumed E=mc^2 for all particles, then that would mean that red light is lighter than blue light.

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    • lvxferre@mander.xyz ⁨2⁩ ⁨months⁩ ago

      This, too: if E = hc/λ and E = mc², then we can combine both as hc/λ = mc². Rearranging this shit you get m = h/λc. Since h/c = 2.2*10⁻⁴²kg*m, you’d get:

      Photon colour	wavelength (in nm)	“Weight” (in 10⁻³⁶kg = 10⁻³qg)
      red	650	3.4
      yellow	600	3.7
      green	550	4.0
      blue	450	4.9

      …BLOODY ULTRAVIOLET IS MAKING ME FAT!

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• Karyoplasma@discuss.tchncs.de ⁨2⁩ ⁨months⁩ ago

  Einstein initially did write:

  If a body gives off the energy L in the form of radiation, its mass diminishes by L/c^2

  Does the inertia of a body depend upon its energy-content?, 1905

  which got re-arranged to E=mc^2. Although he was aware that this doesn’t apply to systems in motion or mass-less particles such as photons.

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