Space and beyond

The science of the origin and development of
the universe. Modern cosmology is dominated
by the Big Bang theory, which brings together
observational astronomy and particle physics.
Cosmology

What is Cosmology?
Cosmology is one of the most exciting disciplines in all of physical science.
It is concerned not so much with individual stars or galaxies in their own
right, but rather with the properties of the Universe as a whole: its origin,
evolution and eventual fate.
Cosmologists work to understand how the Universe came into being, why
it looks as it does now, and what the future holds. They make astronomical
observations that probe billions of years into the past, to the edge of the
knowable Universe. They seek the bases of scientific understanding, using
the tools of modern physics, and fashion theories that provide unified and
testable models of the evolution of the Universe from its creation to the
present, and into the future.

Observable Universe
The observable universe, also known as the Hubble volume, is the region
of space that it is theoretically possible for us to observe, small enough
that light from the furthest regions has had sufficient time to reach Earth
since the Big Bang. This region of space has a diameter of approximately
92.94 billion light-years, centred on the planet Earth. Each different
portion of space has its own visible universe, some overlapping, some not.
There are a number of misconceptions about the concept of the
observable universe. The first is that its size is equal to its age in years
times the speed light travels in a year, about 15 billion light years. This
figure would be true if it was flat, but thanks to Einstein, we know that the
universe is highly curved on cosmological distances by virtue of its
expansion.

Origin of the Universe
The Big Bang is the origin of the universe, occurring approximately 13.7 billion
years ago. It began as a point of nearly zero volume and tremendous density. Then
this point started stretching outward in all directions, not expanding within space
but causing the expansion of space itself.

The Big Bang
Once it was understood that the Universe had a beginning, scientists began
to ask “how did it come into existence, and what existed before it?”
Most scientists now believe that the answer to the first part of the
question is that the Universe sprang into existence from a singularity -- a
term physicists use to describe regions of space that defy the laws of
physics. We know very little about singularities, but we believe that others
probably exist in the cores of black holes.
The second part of the question, as to what existed before the Big Bang,
has scientists baffled. By definition, nothing existed prior to the beginning,
but that fact creates more questions than answers. For instance, if nothing
existed prior to the Big Bang, what caused the singularity to be created in
the first place?

The Big Bang
Once the singularity was created, it began to expand through a
process called inflation. The Universe went from very small, very
dense, and very hot to the cool expanse that we see today. This
theory is now referred to as the Big Bang, a term first coined by Sir
Fred Hoyle during a British Broadcasting Corporation (BBC) radio
broadcast in 1950.
Interestingly, there really wasn’t any sort of explosion as the name
suggests, but rather the rapid expansion of space and time. It is like
blowing up a balloon, as you blow air in, the exterior of the balloon
expands outward.

Evidence for the Big Bang
The CMB signal detected by Penzias and Wilson, a discovery for
which they later won a Nobel Prize, is often described as the echo of
the Big Bang. Because if the Universe had an origin, it would leave
behind a signature of the event. The Big Bang left behind a heat
signature throughout all of space.
Another prediction of the Big Bang theory is that any direction we
look out into space, we should see objects moving away from us
with a velocity proportional to their distance away from us, a
phenomenon known as the red shift.

Evidence for the Big Bang
Edwin Hubble, in 1929, was able to correlate
the distance to objects in the universe with
their velocities -- a relation known as Hubble's
Law. Big Bang theorists later used this
information to approximate the age of the
Universe at about 15 billion years old, which is
consistent with other measurements of the
age of the Universe.

Space is the boundless three-dimensional extent in
which objects and events have relative position and
direction. Physical space is often conceived in three
linear dimensions, although modern physicists
usually consider it, with time, to be part of a
boundless four-dimensional continuum known as
spacetime.
Space

Will Space expand forever?
The fate of the universe is determined by a struggle between the
momentum of expansion and the pull of gravity. The rate of
expansion is expressed by the Hubble Constant, Ho, while the
strength of gravity depends on the density and pressure of the
matter in the universe.
If the pressure of the matter is low, as is the case with most forms of
matter of which we know, then the fate of the universe is governed
by the density.
If the density of the universe is less than the critical density, which is
proportional to the Ho
2, then the universe will expand forever.
If the density of the universe is greater than the critical density, then
gravity will eventually win and the universe will collapse back on
itself, the so called Big Crunch.

Will Space expand forever?
However, the results of the WMAP mission and observations of
distant supernova have suggested that the expansion of the universe
is actually accelerating, which implies the existence of a form of
matter with a strong negative pressure, such as the cosmological
constant. This strange form of matter is also sometimes referred to
as dark energy.
If dark energy in fact plays a significant role in the evolution of the
universe, then in all likelihood the universe will continue to expand
forever.

Shape of the space
The density of the universe also determines its geometry.
If the density of the universe exceeds the critical density, then the
geometry of space is closed and positively curved like the surface of a
sphere.
If the density of the universe is less than the critical density, then the
geometry of space is open (infinite), and negatively curved like the surface
of a saddle.
If the density of the universe exactly equals the critical density, then the
geometry of the universe is flat like a sheet of paper, and infinite in extent.
The simplest version of the inflationary theory, an extension of the Big
Bang theory, predicts that the density of the universe is very close to the
critical density, and that the geometry of the universe is flat, like a sheet of
paper.

Space-time
The concepts of time and space are very important for
understanding the function of phenomena in the natural world. The
measurement of time is not absolute. Time is perceived by humans
in a relative fashion by using human created units of measurement
i.e. seconds, minutes, hours, and days.
In physics, spacetime (space–time continuum) is any mathematical
model that combines space and time into a single interwoven
continuum.

Relativity and the Space-time Continuum
In order to sidestep the issue of Newton's Third Law of Motion and
the impossibility of matter traveling faster than the speed of light,
we can look to Einstein and the relationship between space and
time.
Taken together, space, consisting of three dimensions and time are
all part of what's called the space-time continuum.
In his Special Theory of Relativity, Einstein states two postulates:
 The speed of light ( ~300,000,000 m/s) is the same for all
observers, whether or not they're moving.
 Anyone moving at a constant speed should observe the same
physical laws.

Putting these two ideas together, Einstein realized that space and
time are relative -- an object in motion actually experiences time at a
slower rate than one at rest.
Although this may seem absurd to us, we travel incredibly slow when
compared to the speed of light, so we don't notice the hands on our
watches ticking slower when we're running or traveling on an
airplane.
Scientists have actually proved this phenomenon by sending atomic
clocks up with high-speed rocket ships. They returned to Earth
slightly behind the clocks on the ground.

The closer an object gets to the speed of
light, that object actually experiences time
at a significantly slower rate.

Speed of Light
The speed of light in a vacuum is 299,792 km/s, and in theory
nothing can travel faster than light. If you could travel at the speed of
light, you could go around the Earth 7.5 times in one second.
Early scientists thought it must travel instantaneously. Over time,
however, measurements of the motion of these wave-like particles
became more and more precise.
Thanks to the work of Albert Einstein and others, we now
understand light speed to be a theoretical limit: light speed — a
constant called c — is thought to be not achievable by anything with
mass.

Faster than Light?
Faster-than-light (also superluminal or FTL) communication and travel
refer to the propagation of information or matter faster than the
speed of light.
Under the special theory of relativity, a particle (that has rest mass)
with subluminal velocity needs infinite energy to accelerate to the
speed of light, although special relativity does not forbid the existence
of particles that travel faster than light at all times

In physics and mathematics, the dimension of a
mathematical space (or object) is informally
defined as the minimum number of coordinates
needed to specify any point within it.
In modern physics, space and time are unified in a
four-dimensional continuum called spacetime.
Dimension

3D Space
Three-dimensional space is a geometric
three-parameter model of the physical
universe in which all known matter
exists. These three dimensions can be
labelled by a combination of three
chosen from the terms length, width,
height, depth, and breadth. Any three
directions can be chosen, provided that
they do not all lie in the same plane.

4th Dimension?
In mathematics, four-dimensional space is a geometric space with four
dimensions. It has been studied by mathematicians and philosophers
for over two centuries, both for its own interest and for the insights it
offered into mathematics and related fields.
In modern physics, space and time are unified in a four-dimensional
Minkowski continuum called spacetime, whose metric treats the time
dimension differently from the three spatial dimensions. Spacetime is
not a Euclidean space.

Hypercube or The Tesseract
Hypercube is a multidimensional analogue
of a 3-dimensional cube in that each
coordinate of a point in a hypercube is
restricted to the same 1-dimensional (line)
segment. Tesseract is a 4-dimensional
hypercube.
This hence verifies that a 4th dimensional
world is possible with 4 dimensional
objects.

Time travel has been a popular topic for science
fiction for decades, Often jumping on special
vehicles and arriving at a different point in time.
The reality, however, is more muddled.
Not all scientists believe that time travel is possible.
To understand time travel, we have to understand
time.
Time Travel

Understanding time
While most people think of time as a constant, physicist Albert Einstein
showed that time is an illusion; it is relative — it can vary for different
observers depending on your speed through space.
To Einstein, time is the fourth dimension. Space is described as a three-
dimensional arena, which provides a traveller with coordinates — such
as length, width and height —showing location.
Time provides another coordinate — direction — although
conventionally, it only moves forward.

Understanding time
Einstein's theory of special relativity says that time slows down or
speeds up depending on how fast you move relative to something else.
Approaching the speed of light, a person inside a spaceship would age
much slower than his twin at home. Also, under Einstein's theory of
general relativity, gravity can bend time.
Picture a four-dimensional fabric called space-time. When anything
that has mass sits on that piece of fabric, it causes a dimple or a
bending of space-time. The bending of space-time causes objects to
move on a curved path and that curvature of space is what we know as
gravity.

Understanding time
Both the general and special relativity theories have been proven with
GPS satellite technology that has very accurate timepieces on board.
The effects of gravity, as well as the satellites' increased speed above
the Earth relative to observers on the ground, make the unadjusted
clocks gain 38 microseconds a day. (Engineers make calibrations to
account for the difference.)
In a sense, this effect, called time dilation, means astronauts are time
travellers, as they return to Earth very, very slightly younger than their
identical twins that remain on the planet.

A wormhole is a hypothetical
topological feature of
spacetime that would
fundamentally be a shortcut
through spacetime. A
wormhole is much like a
tunnel with two ends.
Wormholes

Through the wormhole
General relativity also provides scenarios that could allow travellers to go
back in time, according to NASA. The equations, however, might be difficult
to physically achieve.
One possibility could be to go faster than light, which travels at 299,792 km/s
in a vacuum. Einstein's equations, though, show that an object at the speed
of light would have both infinite mass and a length of 0. This appears to be
physically impossible, although some scientists have extended his equations
and said it might be done.
A linked possibility would be to create wormholes between points in space-
time. While Einstein's equations provide for them, they would collapse very
quickly. Also, scientists haven't actually observed wormholes yet. The
technology needed to create a wormhole is far beyond anything we have
today.

Black holes
Another possibility would be to move a ship rapidly around a black hole, or to
artificially create that condition with a huge, rotating structure.
"Around and around they'd go, experiencing just half the time of everyone
far away from the black hole. The ship and its crew would be traveling
through time“, physicist Stephen Hawking wrote in the Daily Mail in 2010.
Imagine they circled the black hole for five of their years. Ten years would
pass elsewhere. When they got home, everyone on Earth would have aged
five years more than they had."
However, he added, the crew would need to travel around the speed of light
for this to work. Physicist Amos Iron at the Technion-Israel Institute of
Technology in Haifa, Israel pointed out another limitation if one used a
machine: it might fall apart before being able to rotate that quickly.

Cosmic Strings
Another theory for potential time travellers involves something called
cosmic strings — narrow tubes of energy stretched across the entire
length of the ever-expanding universe. These thin regions, left over
from the early cosmos, are predicted to contain huge amounts of mass
and therefore could warp the space-time around them.
Cosmic strings are either infinite or they’re in loops, with no ends,
scientists say. The approach of two such strings parallel to each other
would bend space-time so vigorously and in such a particular
configuration that might make time travel possible, in theory.

Grandfather Paradox
Besides the physics problems, time travel may also come with some
unique situations. A classic example is the grandfather paradox, in
which a time traveller goes back and kills his parents or his grandfather
— the major plot line in the Terminator movies — or otherwise
interferes in their relationship — think Back to the Future — so that he
is never born or his life is forever altered.
If that were to happen, some physicists say, you would be not be born
in one parallel universe but still born in another. Others say that the
photons that make up light prefer self-consistency in timelines, which
would interfere with your evil, suicidal plan.

So.. Is it possible?
While time travel does not appear possible — at least, possible in the
sense that the humans would survive it — with the physics that we use
today, the field is constantly changing. Advances in quantum theories
could perhaps provide some understanding of how to overcome time
travel paradoxes.
One possibility, although it would not necessarily lead to time travel, is
solving the mystery of how certain particles can communicate
instantaneously with each other faster than the speed of light.

A black hole is a mathematically
defined region of spacetime
exhibiting such a strong
gravitational pull that no
imminent particle or
electromagnetic radiation can
escape from it.
Black Holes

When a super-massive star
dies, it's corpse collapses into
a knot so tight not even light
can escape. And this drain on
the fabric of the Universe can
alter the shape of space and
shift the flow of time.
Black Holes

Formation of Black Holes
Black holes are the cold remnants of former stars, so dense that no matter—
not even light—is able to escape their powerful gravitational pull.
When giant stars reach the final stages of their lives they often detonate in
cataclysms known as supernovae. Such an explosion scatters most of a star
into the void of space but leaves behind a large cold remnant on which fusion
no longer takes place.
In younger stars, nuclear fusion creates energy and a constant outward
pressure that exists in balance with the inward pull of gravity caused by the
star's own mass. But in the dead remnants of a massive supernova, no force
opposes gravity—so the star begins to collapse in upon itself.
With no force to check gravity, a budding black hole shrinks to zero volume—
at which point it is infinitely dense. The star's own light becomes trapped in
orbit, and the dark star becomes known as a black hole.

Effect of Black Holes
Black holes pull matter and even energy into themselves—but no more
so than other stars or cosmic objects of similar mass. That means that
a black hole with the mass of our own sun would not "suck" objects
into it any more than our own sun does with its own gravitational pull.
Planets, light, and other matter must pass close to a black hole in order
to be pulled into its grasp. When they reach a point of no return they
are said to have entered the event horizon—the point from which any
escape is impossible because it requires moving faster than the speed
of light.

Power of Black Holes
Black holes are small in size. A million-solar-mass hole, like that
believed to be at the centre of some galaxies, would have a radius of
just about three million kilometres—only about four times the size of
the sun. A black hole with a mass equal to that of the sun would have a
three-kilometre radius.
Because they are so small, distant, and dark, black holes cannot be
directly observed. Yet scientists have confirmed their long-held
suspicions that they exist. This is typically done by measuring mass in a
region of the sky and looking for areas of large, dark mass.

What lies inside a black hole?
We cannot glimpse what lies inside the event horizon of a black hole because
light or material from there can never reach us. Even if we could send an
explorer into the black hole, she could never communicate back to us.
Current theories predict that all the matter in a black hole is piled up in a
single point at the centre, but we do not understand how this central
singularity works.
To properly understand the black hole centre requires a fusion of the theory
of gravity with the theory that describes the behaviour of matter on the
smallest scales, called quantum mechanics. This unifying theory has already
been given a name, quantum gravity, but how it works is still unknown. This
is one of the most important unsolved problems in physics. Studies of black
holes may one day provide the key to unlock this mystery.

What lies inside a black hole?
Einstein's theory of general relativity allows unusual characteristics for
black holes. For example, the central singularity might form a bridge to
another Universe. This is similar to a so-called wormhole (a mysterious
solution of Einstein's equations that has no event horizon).
Bridges and wormholes might allow travel to other Universes or even
time travel. But without observational and experimental data, this is
mostly speculation.
We do not know whether bridges or wormholes exist in the Universe,
or could even have formed in principle. By contrast, black holes have
been observed to exist and we understand how they form.

Gravity: Not what it seems
When Einstein wrote his general theory of relativity in 1915, he found
a new way to describe gravity.
It was not a force, as Sir Isaac Newton had supposed, but a
consequence of the distortion of space and time, conceived together
in his theory as space-time.
Any object distorts the fabric of space-time and the bigger it is, the
greater the effect.
Just as a bowling ball placed on a trampoline stretches the fabric and
causes it to sag, so planets and stars warp space-time - a phenomenon
known as the geodetic effect. A marble moving along the trampoline
will be drawn inexorably towards the ball.

Gravity: Not what it seems
Thus the planets orbiting the Sun are not being pulled by the Sun; they
are following the curved space-time deformation caused by the Sun.
The reason the planets never fall into the Sun is because of the speed
at which they are travelling.
According to the theory, matter and energy distort space-time, curving
it around themselves. Frame dragging theoretically occurs when the
rotation of a large body twists nearby space and time.
It is this second part of Einstein's theory that the NASA mission has yet
to corroborate.

Einstein’s Relativity
Einstein's Theory of Relativity is mostly
known for it’s assertion that time travel is
possible, but in reality this theory
encompasses much more.
The theory itself is actually split into
Special Relativity and General Relativity.

Special Relativity
Special Relativity is based upon two postulates:
 The laws of physics are the same for all observers in
uniform motion relative to one another.
 The speed of light in a vacuum is the same for all
observers, regardless of their relative motion or of the
motion of the source of the light.

General Relativity
General Relativity is the geometric theory of gravitation put
out to argue against Newton’s Law of Universal Gravitation.
Newton’s law was based on the idea that gravity could move
faster than the speed of light, which Einstein obviously
found to be false.
Consequently, Einstein stated that gravity is instead a
property of the geometry of space and time, also called
spacetime.

Conclusion
We know little about the world we live in. The
amount of questions we haven’t been able to
answer is far more than we have.
We are an infinitesimally small part of a universe
bigger than we can imagine.
There are many phenomenon's that are beyond our
capability to understand, but we’ll never stop
trying.
Our journey may be long and hard, but our
curiosity will drive us to the truth.

Thank You
Tanvi Sharma | Aryan Mann| Manan Narang
XI-B
Special Thanks to Vani Ma’am

Space and beyond

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