A notion of gravity

Here is one more in that series of seemingly strange perception of the universe. I am pretty sure I read this in some Scott Adams' book sometime.

Gravity. Ever since seventh grade we have been taught to consider gravity as a force that causes masses to be attracted towards each other. The magnitude of that force is proportional to the product of the masses and inversely proportional to the square of the distance between them. I guess ever since Newton discovered this fact due to a bump on his head caused by a falling apple, no one has debated this understanding firmly.

Einstein came up with another notion of gravity. As most of us know, Einstein never accepted the commonly known perception of the universe, and tried to understand it in his own way. He was a school dropout, which is why I wonder he turned out to be so successful. Newtonian classical forces cause a force acting upon a mass to accelerate, where the force is independent of the mass of the body on which it acts. Gravitational force isn't independent of that mass, which set Einstein thinking. And he went on to propose his general theory of relativity, where he describes gravity as something that causes a bump in space-time (Geek stuff here). This was a revolutionary breakthrough in the understanding of space and time and gravity. I will write another post on my perception of space and time in another post, but right now let's concentrate on gravity.

Before I give you my interpretation (rather the one I read somewhere and which set me thinking), let me give you a simple scenario to visualise. Consider a room inside which things double in size every second. Let us not worry about whether the room expands too right now. Suppose I keep you inside this room along with a pen. Now you will never realise that you are doubling in size every instant, because you can compare your size only with that of the pen, which is also growing in size at the same rate as you are. Hold on to this room for the time being.

Now suppose we have a big room like this, and there is a huge globe inside that room. Say you are standing on the globe. Now you feel like doing something funny and try jumping upwards. Let us consider what happens here. You and the globe, both are doubling in size constantly. When you jump up, both of you expand. But the globe is much larger than you, so you will feel it expands faster than you. Notice that I didn't say 'more' but 'faster'. As such, the globe will eventually catch up with you after you 'jumped'. Makes sense?

So what is gravity? Is it a way in which we perceive an ever expanding universe? Consider the other case where say objects would be shrinking in size constantly. In this space, once you jump upwards, the globe will seem to be going further away all the while, instead of catching up with you. I guess this is simple enough to be understood. So are we truly held to the earth by a force, or is it just that the earth is expanding faster than us, and so we never realise that?

One more line of thought. Newton's gravity fails to explain the bending of light around massive objects. Einstein's does; as gravity curves space time, thus reducing the shortest distance between two points, and also light always takes the shortest path from one point to another. How about our expansion theory? It can also explain the bending of light; the faster expansion of a 'massive' object can make us feel as if light is indeed following a bent path. So how do we really understand what gravity is? We cannot approve of this expansion theory unless we leave the system (universe; or if you go by my last post, a multiverse), which I am not sure is quite possible. I guess until we find a solution to do that, we should be content hypothesising such strange, but interesting theories.