[meteorite-list] Fw: term definitions and usage

[Richard Montgomery]

Thanks Doug!   Another great explanation....

When papers write things such as "Ma (relative age)" as a subtext, one 
begins to question the long-held definition in one's head.

[Let's have some OT out-of-context fun:  so, if the EU considers Ga as 10^ 
deficits in billions, their definition of Ga, no wonder they're in 
trouble!!]

No jab intended.....only context....Washington should be reading this....
-Richard  M




----- Original Message ----- 
From: "MexicoDoug" <mexicodoug at aim.com>
To: <clp at alumni.caltech.edu>; <meteorite-list at meteoritecentral.com>
Sent: Sunday, July 24, 2011 6:54 PM
Subject: Re: [meteorite-list] Fw: term definitions and usage


> Chris wrote:
> "Ga is billions (gigayear) of years"
>
> ... and one reason it is in the scientific lit is because it is much less 
> confusing on the eye though nothing in rocks is a US trillion years old 
> (twelve zeros);
>
> Many Europeans consider the billion with 12 zeros (1,000,000,000,000), 
> while in the US and many other countries, it has been considered nine 
> zeros, a thousand million.  Giga has the benefit of only referring to nine 
> zeros everywhere ...
>
> Here's the rest of the prefixes fyi:
> http://en.wikipedia.org/wiki/Gigaannum#SI_prefix_multipliers
>
> SI prefix multipliers
>
>  ka (for kiloannum), is a unit of time equal to one thousand (10^3) years.
>  Ma (for megaannum), is a unit of time equal to one million (10^6) years. 
> It is commonly used in scientific disciplines such as geology, 
> paleontology, and celestial mechanics to signify very long time periods 
> into the past or future. For example, the dinosaur species Tyrannosaurus 
> rex was abundant approximately 65 Ma (65 million years) ago (ago may not 
> always be mentioned; if the quantity is specified while not explicitly 
> discussing a duration, one can assume that "ago" is implied; the 
> alternative but deprecated "mya" unit includes "ago" explicitly.). In 
> astronomical applications, the year used is the Julian year of precisely 
> 365.25 days. In geology and paleontology, the year is not so precise and 
> varies depending on the author.
>  Ga (for gigaannum), is a unit of time equal to 10^9 years (one billion on 
> the short scale, one milliard on the long scale). It is commonly used in 
> scientific disciplines such as cosmology and geology to signify extremely 
> long time periods in the past. For example, the formation of the Earth 
> occurred approximately 4.57 Ga (4.57 billion years) ago.
>  Ta (for teraannum), is a unit of time equal to 10^12 years (one trillion 
> on the short scale, one billion on the long scale). It is an extremely 
> long unit of time, about 70 times as long as the age of the universe. It 
> is the same order of magnitude as the expected life span of a small red 
> dwarf star.
>  Pa (for petaannum), is a unit of time equal to 10^15 years (one 
> quadrillion on the short scale, one billiard on the long scale). The 
> half-life of the nuclide cadmium-113 is about 8 Pa. This symbol coincides 
> with that for the pascal without a multiplier prefix, though both are 
> infrequently used and context will normally be sufficient to distinguish 
> time from pressure values.
>  Ea (for exaannum), is a unit of time equal to 10^18 years (one 
> quintillion on the short scale, one trillion on the long scale). The 
> half-life of tungsten-180 is 1.8 Ea.[20]
>
>
> Best wishes
> Doug
>
>
>
>
> -----Original Message-----
> From: Chris Peterson <clp at alumni.caltech.edu>
> To: meteorite-list at meteoritecentral.com
> Sent: Sun, Jul 24, 2011 9:37 pm
> Subject: Re: [meteorite-list] Fw: term definitions and usage
>
>
> Ga is billions (gigayear) of years. Ma is millions (megayear) of years. 
> "a" is the most commonly used symbol for year (from annus) in scientific 
> publications.
> Chris
> ******************************* Chris L Peterson Cloudbait Observatory 
> http://www.cloudbait.com
> On 7/24/2011 7:26 PM, Richard Montgomery wrote:
>>
>> Hello List, Another neophyte question (I can use some clarification): 
>> when / how
> are
>> the time-measurements (relatively speaking) designations "Ga" and Ma" 
>> used, and their respective differences? (I believe I know the difference 
>> through context, but why go through
> so
>> many papers and texts with the question-mark over my head?) Sincerely, 
>> Richard Montgomery
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