Description acceptable. Although this quantity doesn’t increase opacity, red stellar populations have higher values of it, making it degenerate with metallicity. Kelvin and Helmholtz were off by many orders of magnitude when calculating the Sun’s value of this quantity. Dimensional analysis can sketchily justify that a form of this quantity is about one over H-nought. Low-mass galaxies that are also [emphasize] low in this (-5[1])quantity are the main targets of JWST. Blue stars have relatively low values of this quantity when leaving the main sequence. Radiometric methods of determining this quantity use the half-life of known isotopes. For 10 points, the universe’s value of what quantity is about 13.7 billion years? (10[1])■END■