Cloud Hosting

In Fig. 2, we plot all the composite objects in the Universe: protons, atoms, life forms, asteroids, moons, planets, stars, galaxies, galaxy clusters, giant voids, and the Universe itself. Humans are represented by a mass of 70kg and a radius of 50cm (we assume sphericity), while whales are represented by a mass of 105kg and a radius of 7 m. Objects with uniform density are described by m r 3. Thus, in a log(m)log(r) plot such as Fig. 2, all objects of the same density fall along the same isodensity line of slope 3. For example, atoms and objects made of atoms, such as life on Earth (viruses, bacteria, fleas, humans, and whales) asteroids, moons, planets, and main sequence stars, lie close to the atomic density line atomic water = 1 gm / cm 3. At the top of the plot, this line is labeled atomic 10 3 s, because objects along this isodensity line have the density of water, and because the entire Universe had this density at the end of Big Bang Nucleosynthesis, 10 3 s after the big bang. Protons, neutrons, and neutron stars are found along the slope = 3, nuclear density line which is 14 orders of magnitude more dense than anything made of atoms: nuclear / atomic 10 14. It is labeled nuclear 10 6 s because the entire Universe was at this nuclear density a millionth of a second after the big bang.

The largest objects in the upper right are super-clusters of galaxies with densities approximately 20% larger than the current matter density of the Universe. For completeness, we have also plotted the largest known voids. The current matter density is the longest diagonal isodensity line on the right labeled at the top now 10 17 s). This density is the value in Fig. 1 of the black ( r + m) line at t=now.

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All objects and some questions | American Journal of Physics - American Institute of Physics