Sunday, September 11, 2016

On Light, Gravity and Inter-Galactic Travel Plans

Conventional wisdom is that light travels in a straight line. It is also wrong. This is not an outrageous claim and has been well known to anyone following Einstein's General Theory of Relativity. The explanation is also rather simple and everything to do with gravity - yes, the same gravity we all were taught in high school.

This post is not to explain General Theory of Relativity (I gather that there are very few who understand it - so I'd imagine I don't). The post is around how we can actually travel across the universe without breaking the speed barrier. Current science puts the max. speed limit of any object at c - the speed of light. Weird things start to happen as an object approaches light speed - its mass becomes close to infinity, but more importantly, TIME STOPS for that object at the speed of light.

1) There is indeed a way to stay young forever and ever - just keep traveling at the speed of light.
2) The old Hindu mythology I read in my childhood often made references to a strange concept - that a second ("ek pal") for the Gods is equivalent of eons and eons of life here at Earth. They probably travel at a speed very close to light.

I digress. The cosmic problem is that the universe is so vast, it would take a near-infinite amount of time to get to its edges (at least 14 billion years traveling at light speed since that's the age of the universe as per the current scientific wisdom). Even to get to Andromeda Galaxy, the nearest galaxy to our Milky Way, it would take 2.5 million years when traveling at the speed of light.

So even if we devise a way to travel at the speed of light (and stop time, i.e. aging for us), it would still take 2.5 million years for a person to go explore Andromeda. That just seems useless.

I do think there is a way - and that we can rely on our old friend Gravity to help us here. You see, Gravity is nothing but a warp in space-time. Bigger the object, bigger the warp. See picture on the right (courtesy  (c) NASA).

The warp is what pulls nearby objects to the bigger object - objects essentially "fall" towards the bigger object. P.S. If you are curious why Earth just doesn't fall into Sun, it's because of the angular momentum Earth has (google for more info).

Here is the important piece though - Light travels along the warp created by gravity.  It doesn't travel in a straight line but along the curve (warp). Now this has some huge implications, one of which is gravitational lensing, allowing us to see galaxies that are hidden behind other galaxies (again, google it).

So how is this relevant to my inter-galactic travel plans. Well, you see, gravity is directly proportional to the mass of an object. So, my gravitational warp is less than that of Earth's, and the Earth's is less than that of Sun's. Imagine the gravitational warp that'd be created by the galaxies themselves - Milky Way and Andromeda. 

And light has to follow the warp to get from Milky Way to Andromeda - in other words, light is taking really the long, curvy route to get between these two galaxies. See picture on the right.

What if we figure out a way for us to travel really using the shortest path, and not along the gravitational warp (i.e. not along the path light takes). Then the distance we'd have to travel will be cut down massively. The reduction in distance will be proportional to the mass of the two objects we are trying to travel between. Given that galaxies are massive, the reduction in distance would also be massive when we travel using the shortest path.

The key issue is that we would be traveling across a completely new (as yet undetermined and undiscovered) vector, since the space-time vectors we know are warped (curved). I imagine it is only a matter of time (?) we find that vector. And then, off we go to Andromeda and beyond.

While on the subject, think about the gravitational warp created by the whole universe itself (meaning all the objects in it combined). I'd imagine the warp to be so deep, and the distance for light to travel from our universe to perhaps an adjacent universe so long, that for all practical purposes, our universe would appear as a block hole to another universe!

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