![]() ![]() Estimate the mass of the universe in mks. A typical galaxy has about 1.5 x 1012 including dark matter. This is a squishy number because galaxies far away are smaller in mass (they accrete mass over time), but it's a good rough number. Looking back toward the beginning of the class, we estimated that there are about 300 billion galaxies in the Universe. 1 (a) If you stop the expansion of the Universe in its tracks and could jump anywhere in the observable universe instantaneously (astronomers call these "proper" coordinates), you would find that the Universe is about Run = 15 Gpc in radius. Clearly my professor should not be an engineer. As a professor in astrophysical hydrodynamics told our class "2x = 1." I am still scratching my head over that. Without the bar, it is the official formula for Ac over a full 2radians. This is called the "reduced" Compton wavelength which is the wavelength over one radian. The attentive student will note that I have switched from h to fi. However, there is a coincidence that astronomers look at and think - that's kind of weird. It is not unless black holes survive the inflation period, in which case we would probably see ring-like structures in the CMB and galaxy counts, something that Sir Roger Penrose thinks he has detected (no one else has though). ![]() People on Quora and Reddit like to speculate that the Universe is a black hole. ![]()
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