### A Huge Cosmic Bubble of Gas and Dust

I was reviewing a MAT082 lecture note and I clicked the Astronomy Picture Of The Day hyperlink. The "Explanation" for the picture started as follows.

```   "A cosmic bubble of gas and dust, RCW 79 has
grown to about 70 light-years in diameter."
```

Diameters... timely subject; therefore, let's look at NASA.gov:: RCW79.

A light-year approximates `5.88 trillion` (5,880,000,000,000) miles. This number needs to be multiplied by `70` because the RCW79 cosmic bubble is `70 light-years` in diameter. [Note: the `.88` in `5.88 trillion` represents ``` 880 billion```.]

```   5.88 x 70 = 411.60

70 light-years is 411.60 trillion miles.

411.60 trillion is 411,600,000,000,000

411,600,000,000,000 is 411.6 x 1012

411.6 x 1012 is 411.6 x 10 x 10 x 10 x 10 x 10 x 10
x 10 x 10 x 10 x 10 x 10 x 10

411.6 x 1012 is 4.116 x 1014
```

First returned Google hyperlink was to The Nine Planets Glossary at Arizona.edu.

A light-year is "the distance light travels in one year." The speed of light approximates `186,282 miles per second`. One light-year is `63,239 AU`, where AU is astronical unit (distance between earth and sun).

Wikipedia.org:: Speed of light

Creator: Gerald D. Thurman [gthurman@gmail.com]
Created: 15 April 2005

##### An Approximation Observation

One of the definitions given by Google said a light-year was "approximately 5.8 trillion miles." The difference between 5.88 trillion and 5.8 trillion is `.08 trillion` which is `80 billion`.

In some cases being off by plus-or-minus `80 billion` is insignificant; however, in other cases, being off by `one` could cause problems.

The Friday, 15 April 2005, Arizona Republic had a short "News from home" article from Saginaw, Michigan, about a guy stuck with a bullet in his chest because it is only `5 millimeters` away from his "aortal artery."

Google Search tells us `5 millimeters = 0.196850394 inch`.

It is tough to save somebody when a bullet is two-tenths of an inch away from the body's main artery. [ view an inch]

To be completed.