Another example of Units, with conversions
•1 light-year
= c ´ t (where c
is the speed of light and t is one year)
= 3.0 ´ 108 m/s ´ 365 days
= 1.1 ´ 1011 (m ´ days /s)
= 3.0 ´ 108 m/s ´ 365 days
= 1.1 ´ 1011 (m ´ days /s)
•but we know light-years is a distance and must have
“dimensions” of
distance. We should have units of just
meters. The fact that we have this extra (days/s) means we have left something
out.
•If we multiply by
(24 hr/day ´ 60 min/hr
´ 60 sec/min)
the units will work out
right and so will the numerical answer
•
•
= 1.1 ´ 1011 ´ 24 ´ 60 ´ 60 m
= 9.5 ´ 1015 m
= 9.5 ´ 1012 km
= 1.1 ´ 1011 ´ 24 ´ 60 ´ 60 m
= 9.5 ´ 1015 m
= 9.5 ´ 1012 km
