Note: This post was published in 2011, but the original was invaded by scammers to the point I copied the legitimate bits and deleted the original. :-)
We know what happens when a wet dog shakes itself and some always seems to get into your mouth! At the moment of impact have you wondered in what possible abominations your temporarily despised pet might have been rolling? Maybe you have, but then did you wonder at the forces that propel those contaminated droplets in your direction at speeds beyond your ability to avoid them?
Centripetal force, circular motion. That’s what it is. It is that force that makes a stone fly from a sling or a satellite stay up there.
Now, I direct your attention to a previous post that talked about the globe slowing a little (I postulated a change of 0.0137 seconds longer days by the year 2050) and then take your imagination back about four and a half billion years, when the whole glowing hot mess of oxides nitrogen and iron settled itself into orbit, third planet from its birth mother.
As mainly gases, imagine how much larger it would have been and how far from the axis its centre of spinning force must have been!
I am not about to try the math, but if we take ocean water again then imagine it all as vapour (steam to me and you), and if you like, include coal and oil, no longer buried, but in the atmosphere as CO2 , we realise that our planet would have been, by volume at least, predominately atmospheric gas, extending its weight hundreds, perhaps thousands of kilometres further out from where it is now, way below sea and ground level.
Don't go, because here is where the story really starts. It includes a confession of the method I used to teach ‘Conservation of Energy’ to otherwise disinterested eleven year olds.
We all went to the local park where there stood an old fashioned roundabout, all weathered wood and rusty tubing. That wonderful piece of scientific equipment is long gone, removed by Child Safety Nazis, possibly as a result of the use to which it was put by me. Nevertheless, let me confess what we did. It was really me, but I use the royal we to suggest shared responsibility.
We placed six of the smallest children at the centre, instructing them to hold on tightly no matter what. Then at the outer end of each of the six radiating bars, a larger child, with feet on the edge and body hanging out as far as possible, was instructed to listen for a signal from me. Other children spun the roundabout with its human appendages until they could impart no further energy.
Then, on the signal, the hangers-on pulled themselves towards the centre as quickly as they could.
What happened? Well, the whole system accelerated alarmingly and all were screaming with delight or terror until the signal was given for the moving bodies to slip back to the perimeter when it slowed again, allowing the guinea pigs off, to laugh hysterically, run for the washroom to vomit or demand a second go, depending on the strength of their stomachs or predilection to self harm.
But I guarantee their understanding of conservation of energy, levers and centripetal force were never forgotten.
So what has that got to do with the speed of rotation of our planet at its birth billions of years ago?
OK, let’s go find one of those old fashioned roundabouts and we can pretend we are water vapour and CO2 condensing towards the centre of the planet, and see what it does to its rotation.
Here it is expressed as a mathematical equation: v2 / r =a, where ‘a’ is centripetal acceleration, ‘v’ is velocity in meters per second, and ‘r’ is the radius of the circle in meters. Don't let that worry you. Suffice to say, any reduction in ‘r’ really gives ‘a’ some ‘wow’!
That suggests our planetary rotation speed has accelerated considerably over the last few billion years from when there might have been only a couple of hundred days or less in a year.
You understand? No? OK, climb onto the roundabout and hang on!