
What On Earth Is Wrong With Gravity?
The Power of Gravity Helps Shape the Universe

Particle
physicist Dr Brian Cox wants to know why the Universe is built the way
it is. He believes the answers lie in the force of gravity.
But Newton
thought gravity was powered by God, and even Einstein failed to
completely solve it.
Heading
out with his film crew on a road trip across the USA, Brian fires
lasers at the moon in Texas, goes mad in the desert in Arizona,
encounters the bending of space and time at a maximum security military
base, tries to detect ripples in our reality in the swamps of Louisiana
and searches for hidden dimensions just outside Chicago.
Brian
Cox is a British particle physicist, a Royal Society University
Research Fellow and a professor at the University of Manchester.
Particle physicist Dr Brian Cox wants to know why the Universe is built
the way it is. He believes the answers lie in the force of gravity.
Gravity,
is one of the four fundamental interactions of nature (along with the
strong force, electromagnetism and the weak force), in which objects
with mass attract one another.
In
everyday life, gravitation is most familiar as the agent that gives
weight to objects with mass and causes them to fall to the ground when
dropped. Gravitation causes dispersed matter to coalesce, thus
accounting for the existence of the Earth, the Sun, and most of the
macroscopic objects in the universe.
E=mc^{2}
Einstein and the World's Most Famous Equation
The history behind how this equation could be invented..and who all
played their role in inventing this wonderful and powerful equation
which can destroy the world or also make the whole world glow.
Gravitation
is responsible for keeping the Earth and the other planets in their
orbits around the Sun; for keeping the Moon in its orbit around the
Earth; for the formation of tides; for natural convection, by which
fluid flow occurs under the influence of a density gradient and gravity;
for heating the interiors of forming stars and planets to very high
temperatures; and for various other phenomena observed on Earth.
Modern
physics describes gravitation using the general theory of relativity,
in which gravitation is a consequence of the curvature of spacetime
which governs the motion of inertial objects. The simpler Newton's law
of universal gravitation provides an accurate approximation for most
calculations.
In
general relativity, the effects of gravitation are ascribed to
spacetime curvature instead of a force. The starting point for general
relativity is the equivalence principle, which equates free fall with
inertial motion, and describes freefalling inertial objects as being
accelerated relative to noninertial observers on the ground.
In
Newtonian physics, however, no such acceleration can occur unless at
least one of the objects is being operated on by a force.
Einstein
proposed that spacetime is curved by matter, and that freefalling
objects are moving along locally straight paths in curved spacetime.
These straight paths are called geodesics.
Like Newton's
first law of motion, Einstein's theory states that if a force is applied
on an object, it would deviate from a geodesic. For instance, we are no
longer following geodesics while standing because the mechanical
resistance of the Earth exerts an upward force on us, and we are
noninertial on the ground as a result.
This explains why moving
along the geodesics in spacetime is considered inertial. Einstein
discovered the field equations of general relativity, which relate the
presence of matter and the curvature of spacetime and are named after
him. The Einstein field equations are a set of 10 simultaneous,
nonlinear, differential equations.
The solutions of the field
equations are the components of the metric tensor of spacetime. A metric
tensor describes a geometry of spacetime. The geodesic paths for a
spacetime are calculated from the metric tensor.
Einstein's Messengers
Ripples in the fabric of spacetime from monumental collisions between
black holes, and how scientists are trying to measure them with lasers
and mirrors.
The
discovery and application of Newton's law of gravity accounts for the
detailed information we have about the planets in our solar system, the
mass of the Sun, the distance to stars, quasars and even the theory of
dark matter.
Although we have not traveled to all the planets nor to the Sun, we know their masses.
These masses are obtained by applying the laws of gravity to the measured characteristics of the orbit.
In
space an object maintains its orbit because of the force of gravity
acting upon it. Planets orbit stars, stars orbit Galactic Centers,
galaxies orbit a center of mass in clusters, and clusters orbit in
superclusters. The force of gravity is proportional to the mass of an
object and inversely proportional to the square of the distance between
the objects.

