In the following analogy my brain is compared to a goose, my high-school exam results are fois gras, and physics is the 'gavage'. Now read on!
When i was at high school being force-fed dry physics equations -( Newton's laws etc) i remember thinking : "..but what actually is gravity"?
The equations i learned described how things moved but i wanted to know what gravity actually was. What ACTUALLY IS IT? How is it possible that I (by this I i mean my body not my 'spirit')- that i am connected to EVERY OTHER THING in the observable universe?
The billions of trillions of stars in the night sky tug me upwards WHILST those on the daytime side of the earth pull me downwards. "Here i am stuck in the middle with you". I wonder if it is possible to estimate the total pull of all that stuff up there- what's the gravitational attraction of half the universe from here? It's pretty far away but there is an awful lot of it. (Please forward this blog entry to anyone with a physics degree).
I am attracted to my cat, your cat, your brother's cat,you and your children, that pen that you dropped in the car that slid between the door and the seat- right now i am exerting a force over that pen that reduces by the square of the distance between it and me.
Why does nobody else seem to find this utterly incredible? If it was discovered yesterday it would all over the papers. But no- it's Britney, Britney, Britney, Britney, Heath.
Honestly, even the serious "news" is a glorified version of "he said this, she said that". Nobody will remember presidents or pop-stars in a thousand years. Nobody will care who said what to who(m?) - but humanity will ALWAYS remember Einstein and Newton and that other guy i can't remember- what's him name.. Laplace? Kepler? Something.
They will be remembered as (to paraphrase Newton) the giants who have an infinite regress of mini-giants standing on their shoulders so as to see further (it's giants all the way down by the way).
Unless you are a scientist (and i don't mean a medical doctor) you should consider yourself a support network for the smart people. I am here in case there's a local Einstein with a rash. Britney exists to entertain the scientist with her heartfelt passionate music in his/her time away from the lab.
Nobody will remember us- not even our own family after 3 generations. That's all the fame we've got to look forward to.
"Granny- who is that JPEG of?"
"Oh, that was my great grandfather... he lived at the turn of the century when blogging had just been invented.".
I was told "just learn the equations". So I stopped asking questions and got 91% in physics which got me into medical school. After decades of thinking about it i still don't really get it. Maybe nobody before Einstein got it... and it probably came to him in a flash whilst daydreaming between patents. (i daydream between patients but just get more and more confused). The internet isn't helping.
It seems it's often the most obvious things that take the longest to get 'discovered' by science - think about the discovery of "air", "sleep", "consciousness". What about 'plate tectonics'? .. it's pretty clear to a 3 year old looking at a map that the continents fit together like a jigsaw puzzle- yet it took till 1960 for that theory to be generally accepted.
Ok... so don't think of gravity as a "force" between two objects. Think (apparently) about a bowling ball on a trampoline. In this case, the 3-D universe is represented by the 2-D surface of the trampoline. When placed gently upon it's surface, a bowling ball indents it.
The more mass an object has, the more it warps the fabric (of trampoline spacetime). When you place a tennis ball at the edge of the trampoline, it rolls downhill until it hits the bowling ball-(or might orbit it a bit until friction slows it down). Viewed from above, it would seem like the bowling ball is attracting the tennis ball by some mysterious force. (Bowlingballation).
More interestingly, imagine throwing a bowling ball on to the surface- you can imagine ripples in the trampoline spreading outwards from the epicentre like ripples on a pond.
These waves are analagous to "gravitational waves". They are waves of space that alternately shrink and stretch space and everything in it. A wave like this passing through a round ball - or even a drawing of a circle - would stretch it back and forth. Gravity wave detectors all over the world are poised waiting to detect this wobble.
Even more interestingly, gravity waves radiate energy away from the objects that emit them... i guess this is like vacuum friction!
N.B. "gravity" the not the same thing as a "gravity wave". A massive stationary object still exerts a force of 'gravity' but does not emit any gravity waves. Gravity is a static warping of spacetime- a Gravity wave propagates this warp.. i think.
Gravity itself also travels at "the speed of light".. although it could also be said that light travels at the speed of gravity. Whatever it is, it is the cosmic speed limit- nothing can ever travel faster.
What this means is that if the sun suddenly disappeared, the earth would continue nicely on it's elliptical orbit for eight whole minutes before the lack of gravity 'registered' and we were flung out into space. (The light would go off at the same time.).
When i first read about this, i couldn't stop thinking about it. What if it had already happened 7.5 minutes ago? Presumably, we could live in the dark burning fossil fuels for a bit- but my guess is the planet's temperature would drop within a few hours to freeze everything solid.
I guess these morbid eschatological thoughts of mine (see "The End of the World") are the atheist analogy to thinking about death and "hell". My scatological eschatological thoughts entail thinking about "Fucking Hell".
This excellent, informative video explains it all: