We all understand the invisible boundaries of our personal space, i.e. how close the next person can be before we start to feel crowded.

It’s not something most of us put a number to. We just sense it. But, should we feel claustrophobic in the universe?

The answer is that it depends on scale. At the atomic level, the universe is profoundly empty, averaging roughly 1 atom for every 4-5 cubic meters. To experience how sparse space is to atoms, imagine if the next nearest human was over 600 times farther away than the moon, on average.

Compared to planets’ sizes, the solar system is empty too. The inner planets are relatively bunched together, while the outer planets are separated by mind-numbing expanses. Yet, even when Mars makes an unusually close approach to Earth this summer, it will still lie 4,520 earth diameters away. To feel this lonely, stay at least 7.6 kilometers (4.5 miles) away from the nearest Homo sapiens (and usually more — remember this is when Mars is closest).

Planets, however, are positively cozy compared to stars. The sun’s nearest neighbor, Proxima Centauri, lies 40 trillion kilometers away, or 29 million solar diameters. There’s no remote island on which you could experience this much isolation from fellow humans. To achieve it, travel one-eighth of the way to the moon.

If the universe seems like a terribly empty place at this point, take heart. Galaxies practically rub elbows: Our nearest large neighbor, the Andromeda galaxy, lies a mere 24 Milky Way diameters distant. If you were the Milky Way, standing on the 50 yard line of a football field, your friend Andromeda would be standing on the 5 yard line. And, scattered about the field would be about three dozen diminutive companions (dwarf galaxies).

Next column: Return of the Evening Star.

Sky calendar through Feb. 21:

Planets:

One hour after sunset:

No planets visible.

One hour before sunrise:

Saturn: SE, very low.

Mars: SSE, low.

Jupiter: S, low.

Moon: Between Mars and Jupiter 2/8. Left of Mars 2/9. Very close to Saturn 2/11. New moon 2:05 p.m. 2/15.

Chris Anderson manages the College of Southern Idaho’s Centennial Observatory in Twin Falls. He can be reached at 208-732-6663 or canderson@csi.edu.

Chris Anderson manages the College of Southern Idaho’s Centennial Observatory in Twin Falls. He can be reached at 208-732-6663 or canderson@csi.edu.

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