The symbols by the planets give their relative distance from the sun as binary values.
the two circles represent two different states of a hydrogen atom that changes every 0.7 nanoseconds. Light travels 21 centimetres in 0.7 nanoseconds, so the unit I between the two circles can be used to describe either that time or that distance, and is used as a binary digit on other parts of the plaque to give measurements in both time and space - those long lines radiating from a single point for example, use the 0.7 nanosecond time period in binary to give the period of the pulsars. And using the 21 centimetre distance and binary digits to the right of the woman, her height is given as 168 centimetres (5’6”).
(I had to teach a lesson on this recently).
“...the two circles represent two different states of a hydrogen atom that changes every 0.7 nanoseconds. Light travels 21 centimetres in 0.7 nanoseconds...”
Very interesting - thanks for the explanation!
(Makes converting over to metric seem simple!)