mass of all ordinary (baryonic) matter in the observable universe: 10^53 kg

if all the matter were collected and compressed to the density of water (e.g., "fluidic space" of Star Trek Voyager), it would fit in a sphere of radius 3 light years.

if compressed to the density of a neutron star (10^17 kg/m^3), it would fit in a sphere of radius 4 au, within the orbit of Jupiter.

if compressed to the density of a black hole singularity, it would fit in a sphere of radius 0. event horizon radius would be 16 billion light years. actually this event horizon applies to all densities.

(we have played the trick of specifying *observable* universe. the actual universe is likely infinite so doesn't fit into any sphere at any density. and because the volume outside the observable universe is likely filled with stuff at the same density as our observable universe, the event horizon Schwarzschild radius formula actually may not be applied, because Schwarzschild metric assumes vacuum outside a sphere.)

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