Advertisement

A
new research paper published in Physical Review Letters has brought forward a
significant new understanding of general relativity laws, and has found some
strange physics taking place inside black holes.

Specifically, that the
direction of time could be reversed within them. Several physical procedures
are perfectly symmetric in time. Take a pendulum for instance. If someone shows
you a video of a pendulum swinging, you cannot differentiate if the video is
actually moving forward or backward.

But
some processes are not symmetric at all. We can tell that a pendulum will
ultimately slow because of friction and we know that it was triggered at some
point, so we can give a temporal direction to physics. The directionality of
time and our view of it was called the "Arrow of Time" by British
astronomer Arthur Eddington, and it has been connected to the entropy of the
cosmos.

Event
horizons ascend from the mathematics of general relativity, but the simplest
mathematical explanation of an event horizon leads to a paradox. Event horizons
must contain all the history of the cosmos, from the Big Bang to its death.
This generates numerous complications as it assumes that the universe must be
deterministic and that past and future are inscribed on the "skin" of
black holes. While this paradox doesn’t affect explanations and forecasts of
the physics of black holes, it is evidently a limiting factor in correctly
understanding how black holes work.

The
new research tries to fill this important gap in black hole physics. The
elementary notion of this paper is grounded on the holographic principle.
According to the author of the paper the event horizon is essentially a
holographic screen, a hypersurface with a precise entropy. You can have two
kinds of holographic screens, past holographic screens and future holographic
screens, liable on whether the entropy inside the surface is increasing or
decreasing.

Study
author Netta Engelhardt told Phys.org "Holographic screens are in a sense
a local boundary to regions of strong gravitaitonal fields. Future holographic
screens correspond to gravitational fields which pull matter together...
whereas past holographic screens correspond to regions which spread matter
out..."

If
this principle is applied to the cosmos as a whole, the entropy arrow is steady
with the second law of thermodynamics. Entropy increases, time moves forward.
But the use of the law onto black holes yields a interesting outcome. Within a
black hole, entropy decreases (things become more structured) and thus
thermodynamically time runs backward.

Although
this is an exciting consequence, the paper is important because it verifies the
first area law in general relativity and it might have solved a long-standing
problem in black holes physics.

This post was written by Usman Abrar. To contact the
writer write to iamusamn93@gmail.com.
Follow on Facebook

## Post A Comment:

## 0 comments: