*The number of viruses in the biosphere has been estimated to be anywhere from 10*

Roger Hendrix gives a great list of examples, and one of these is "How far will 10

^{30}to 10^{32}. But what does this number really mean? How big is 10^{31}? (The number I see most commonly cited as the number of phages in the biosphere)Roger Hendrix gives a great list of examples, and one of these is "How far will 10

^{31}phages stretch if laid end to end?" I thought I would do the calculation for myself (and the readers) to see exactly how long 10^31 phages will stretch.So, we must first begin with two assumptions.

**1)**The number of phages in the biosphere. 10

^{31}is the number I see most cited, but I have also seen 10

^{30}and 10

^{32}. Since 10

^{31}is more familiar too me, and is between the others, we'll use this.

**2)**The length of a phage virion. The average range of virion size is 25ish to 250ish nm. So, I will use 125nm as a middle average.

**125nm at 10**

*The Equations*

^{31}phages, laid end-to-end is 1.25 x 10

^{33}nm.

This converts to 1.25x10

^{24}m

Or 1.25x10

^{21}km

But how far is 10

^{21}km?1 km is 1.05702341 × 10

So, 1.25x10

^{-13}light yearsSo, 1.25x10

^{21}km = ~1.3 x 10^{8}light years**10**

^{8}light years?! THAT'S A LOT!**Here's some scale:**

Distance to the Moon: 0.00000004 light years

To the Sun: 0.000016 light years

To Pluto: ~0.0005 light years

Distance from the Sun to the Center of the Milky Way: ~2.6x10

^{4}light years

Diameter of the Milky Way: 1 x 10

^{5}light years

To Andromeda Galaxy: 2.5x10

^{6}light years

To the M81 Local Group: 1.1x10

^{7}light years

*Phages would stretch a whole order of magnitude further than the next closest galactic local group! Almost 100x farther than the Andromeda Galaxy! And 1000X longer than the diameter of the whole Milky Way!*

Mind boggling.

Mind boggling.