Things like chemistry

The first "official" post is now out!
It is currently September 21 and today in chem class we learned about the exciting world of the SI system and percent error (ooh fascinating), we also watched a video that made myself namely but probably pretty much everyone else feel very small. So I will try to upload it and if it doesn't work then I guess you'll just have to look it up yourselves. The video is called Powers of Ten... the unimaginable size of our universe.

Anyways though, after watching the video and before seeing the glowing pickle, we made some notes so here are the notes in a few simple points.

Experimental Accuracy
If you are measuring something and want to include the possibility that there may be an error in your measurements you write plus or minus (I can't put the symbol) 1/2 of the smallest division of your measuring device.
ie. if your are using a ruler the smallest division of measurement is 1 mm so your answer could be something like 20.2 cm plus of minus 0.05 cm.

Errors
Since no one is perfect (except for according to my brother, my brother is perfect) everyone (except my brother) makes errors. There are three reasons for errors (when you are measuring something)
1. errors in the measuring device (in which case it is not your fault)
2. sloppy measuring (now it's your fault)
3. changing conditions (ie. climate) (it's no longer your fault it's Mother Nature's fault)
Luckily for you though there are ways to calculate errors, two in fact. One however isn't very good.
The not very useful way to calculate errors is through absolute error. In absolute error the formula is simply:  measured-accepted
There is a fatal flaw in this however, because only how many units off are shown we do not know how accurate the answer is.
ie. 3 inches off of a measurement of a computers width is much less precise then 1.5 inches off of the height of
    a typical door frame. Yet the difference between the two of 3 inches and 1.5 inches seems to say
otherwise.
The far more useful way to calculate errors is with percent error, the formula is
((measured-accepted)/accepted)x100 or measured minus accepted divided by accepted, the quotient is then multiplied by 100.
This formula is far more useful then absolute error because the percent error shows how far off your measurement is in relation to the actual measurement in percentage form.
ie. you could be 42% off of the prior computer measurement but only 12.5% off of the door frames height.
 Thus showing exactly how far off your measurement is in comparison to the actual measurement.

Last but not least

SI System (or international system of units)
SI system the prefix's can change how large of small the number is
ie. gigabyte is 1,000,000,000 (and you probably have several on your itouch or whatever else you might have)
ie. a femtameter would be about 0.000000000000001 m or 1x10^-15 m.

Well that's me, good-bye and good night
(unfortunately I'm unable to figure out how to put the video on the blog at the moment so here is the link http://www.youtube.com/watch?v=aPm3QVKlBJg)