In part 2 of the series, we wish to explore why light behaves in a peculiar fashion near heavy objects.
But before doing that we need to expand our understanding of gravity.
Redefining Gravity
When we usually talk of Gravitation we are bound to think like Newton,
where objects are assumed to exerting a force upon each other. Like
imaginary arrows of force in space. But this picture, although good for
high school crumbled, with the advent of Einstein’s theory of
Relativity.
What is the Space-Time Fabric?
Think of spacetime fabric as
an actual cloth of fabric. When you place an object on the fabric, the
cloth curves. This is exactly what happens in the solar system as well.
The
sun with such a huge mass bends the space-time fabric. And the earth
and all the planets are kept in orbit by following this curvature that
has been made by the sun.
The earth - moon system can be thought of in the same manner.
A natural question to ask at this juncture would be:
Why don’t planets just swirl into the sun?
To put it bluntly, they stay in their orbits because there is no other force in the Solar System which can stop them.
The Solar System was formed from a rotating cloud of gas and dust which
spun around a newly forming star, our Sun, at its center. The sun did
pull objects towards itself. But the planets that we see today were
resilient and stuck with their course. And time passed, the net force
acting on them turned to zero and will continue to be zero.
Gravity and Light
Light is affected by the Gravity. This was discussed in a previous post about Gravitational Lensing.
The
gravitational field of a really massive object is super strong. And
this causes light rays passing close to that object to be bent and
refocused somewhere else.
This
is a consequence of the fact that space- time curvature is bent by
objects which have a huge mass.
When light is passing through this dent
the rays of light are directed in another direction. And this causes
effects like gravitational lensing.
The spookiness of the face in the image is also attributed to Gravitational Lensing.
TL;DR - Light bends around heavy objects because heavy objects bend space time. ;)
** If you still find it hard to visualize gravitational Lensing. Take a wine glass and just place it on a graph sheet and explore
