Big Bang Theory & SigFigs! woohoo!

Some classes got to homework today and some did not; if you didn't have homework today, rest assured, everyone will tomorrow.  Tuesday HMWK (due Thursday):  read p. 231-236, 238-241, and problems #1-6 on p. 237, # 2-7 on p. 241.
EXAMS upcoming!!  Friday 5/4: Astronomy exam.  TGT review game here
Friday 5/11 cumulative exam.  skim/review notes and materials from this whole year.
5/15 or 5/16: essay final (I will provide a question from each chapter this semester; you choose which you want to answer)
Sig figs practice problems may be found here and here.  <-- these pages include answers.
Notes for today / tomorrow here and below (some classes were truncated due to Freeman not being used to short class periods again haha)
The Big Bang Theory - evidence from Doppler effect, cosmic microwave radiation, implications of whether the universe will expand forever, stop, or re-collapse.

Significant figures rules & practice: why / how to round
Accuracy vs. precision - accuracy is correctness, precision is the degree of closeness of a measurement; a descriptor of how small the units or increments used to measure something are.

Significant figures:
Report answers with the smallest number of significant figures used in calculation so as to avoid displaying more precision than exists.
Sig figs are:
nonzero numbers AND ...
zeroes IF they
*are between two nonzero digits
*are to the right of the decimal AND to the right of a nonzero digit
BUT NOT IF they
-are to the left of all nonzero digits
-are to the right of nonzero digits but not to the right of a decimal.