EAS

EAS-134 Is Earth Unique?

Fundamentals

1. Numbers

Generally, in science we leave spaces between groups of 3 digits (e.g. 1 000 000), whereas in commerce one uses commas (e.g. $1,000). Here we use “_” just for clarity – don’t use this yourselves.

Numbers	Name	Scientific Representation
0.000_000_000_001	trillionth	10^-12
0.000_000_001	billionth	10^-9
0.000_001	millionth	10^-6
0.001	thousandth	10^-3
0.01	hundredth	10^-2
0.1	tenth	10^-1
1	one	10⁰
10	ten	10¹
100	hundred	10²
1_000	thousand	10³
1_000_000	million	10⁶
1_000_000_000	billion*	10⁹
1_000_000_000_000	trillion	10¹²

*In the European system a billion is a million million (10¹²)

For those of you interested in the really large numbers we have the following, from the website

http://en.wikipedia.org/wiki/Names_of_large_numbers

Name	US	British	Authorities								Relative frequency of use
			AHD4	COD	Dcom	OED2	OEDnew	RHD2	SOED3	W3
million	10⁶	10⁶	*	*	*	*		*	*	*	39
milliard		10⁹	*		*	*					1/94
billion	10⁹	10¹²	*	*	*	*	*	*	*	*	14.0
trillion	10¹²	10¹⁸	*	*	*	*		*	*	*	1.0
quadrillion	10¹⁵	10²⁴	*		*	*		*	*	*	1/44
quintillion	10¹⁸	10³⁰	*		*	*		*	*	*	1/150
sextillion	10²¹	10³⁶	*		*	*		*	*	*	1/190
septillion	10²⁴	10⁴²	*		*	*		*	*	*	1/200

NB There is no specified translation of the word ‘zillion’.

Number of Stars in the Universe?

On average there are 100 billion stars in the average galaxy (10¹¹)

The estimates number of galaxies in the known universe is also 100 billion (10¹¹)

The number of stars in the known universe is therefore estimated to be

100 billion x 100 billion = 10^{11 x}10¹¹ = 10¹¹⁺¹¹= 10²² = ‘10 sextillion’.