4th Dimension

Suppose you've set up a hot date with a totally happ’nin’ (girl/guy). You decide to meet at Penguin's (thus, you have specified a point in space at which to meet). But your meeting plans are not complete: you might show up on Friday at 4:00pm, and your date might show up on Saturday at 8:00pm. So to set up the date, you must specify a point in time as well as a point in space. Time is the fourth dimension, no less important than the first, second, and third dimensions of space.

The FIFTH dimension was a groovin' 60's band who climbed the charts with their 1969 hit “Age of Aquarius/Let the Sunshine In.”

Src: http://homepage.mac.com/phyzman/phyz/BOP/1-XXMOTN/G-Graphical_Kinematics.pdf

The explanation is quite nice.. but the only thing i din understand was the groovin? and the charts and the age of aquarius.. may be my inability to relate this band and events surrounding them?