Liquids<span> are not </span>packed<span> as tightly as </span>solids<span>. And gases are very loosely </span>packed<span>. The spacing of the molecules enables </span>sound<span> to travel much faster through a </span>solid<span> than a gas. </span>Sound<span> travels about four times faster and farther in water than it does in air.</span>
Look at the title of the graph, in small print under it.
Each point is "compared to 1950-1980 baseline". So the set of data for those years is being compared to itself. No wonder it matches up pretty close !
I'm pretty sure its transverse waves
-- Take a straight ruler.
-- Lay it down with the 'zero' mark at the start point.
-- Rotate it around the start point until the end point is also touching the edge of the ruler.
-- From the marks on the ruler, read the straight-line distance from the start point to the end point.
-- Without moving the ruler, observe and write down the DIRECTION from the start point to the end point.
-- The Displacement is the straight-line distance and direction from the start point to the end point.
