Our Place in the Cosmos


During the past few decades we have discovered that at least from a physical perspective, humans are but a speck of dust in the grand scheme of the universe.

We live on a small planet which revolves around a very ordinary star. The Kepler space observatory has shown us that our Milky Way galaxy is teeming with about a billion Earth-size planets orbiting their parent stars in the Habitable Zone (that not-so-cold-not-so-hot region that allows for liquid water to exist on the planet’s surface). The Hubble Space Telescope has revealed that there are a few hundred billion galaxies in the observable universe (Figure 1 shows the Hubble Ultra Deep Field 2014). That is not all. Even the stuff we are made of — ordinary (baryonic) matter — constitutes less than 5% of the cosmic energy budget. About 25% is in the form of dark matter — matter that neither emits nor absorbs any light, and about 70% is in the form of dark energy — a mysterious, smooth energy that may represent the energy of empty space.

Figure 1. The Hubble Ultra Deep Field 2014. A deep image of a tiny piece of sky, taken with the Hubble Space Telescope. Almost every point of light in this image represents a galaxy with about a hundred billion stars like the Sun. Credit: NASA, ESA, H.Teplitz and M. Rafelski (IPAC/Caltech), A. Koekemoer (STScI), R. Windhorst (ASU), Z. Levay (STScI).

And if that is not enough, some recent speculations suggest that even our entire universe may be just one member of a huge ensemble of universes — a “multiverse” — consisting of some 10500 (that is, 1 followed by 500 zeros) universes.

Taken at face value, these facts may seem depressing for our sense of importance.

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