THE UNIVERSE
The universe is
full of stars, arranged in enormous groups called galaxies. Our Sun is one star
among 100 billion in the Milky Way Galaxy. And there are about 100 billion
galaxies in the universe, each with a comparable number of stars.
With some simple
math, we can figure out the total number of stars in the universe:
(100 billion
stars/galaxy) x (100 billion galaxies) = (100 x 10^9) x (100 x 10^9) = 10^22
stars. How many is that? The number of
stars in the universe is more than the number of grains of sand on all
the beaches of the entire Earth!
The entire universe, or just the visible portion of
the universe if it is infinite, is roughly 27 billion light-years across.
That's 159,000,000,000,000,000,000,000 miles. Our solar system, from the Sun to
Pluto, is only 0.00063 light-years across or 3,720,000,000 miles. That makes
our solar system 42,700,000,000,000 times smaller than the whole universe. Can
we put that into a more meaningful perspective? If the entire Earth's surface
represents the whole universe, the solar system on that scale would be
one-millionth of a meter wide, about 1/25,000 of an inch, the size of a single,
small bacteria !
Now consider
that there are at least 10 trillion planetary systems in the
known universe. Notice the “at least”. That is 10,000,000,000,000.
Earth would be “1″ of those. The idea that there is no life on any
of those other 9,999,999,999,999 planets is absurd. Let alone that there
has been no life in the past and there will be no life in the future!
Add in the possibility of multiple, or even
infinite dimensions, which means entire civilizations could exist on a planet
like Earth right alongside us without us knowing it, throw in the nature of
time and time travel as it interacts with gravitational forces like black
holes, and the concept exceeds the human mind’s ability to grasp.
This is Earth. Presumably, it is safe to say you
are here.
This is the solar system in which Earth resides. We
are surrounded by several other planets and orbit a star we call the sun.
Further out in space, there are several solar
systems surrounding ours forming what we call the Solar Interstellar
Neighborhood. Each of these solar systems contains stars and planets.
See that tiny, tiny dot? So tiny you can't even see
it? That is our Solar Interstellar System. From here, we can't even make out
our solar system let alone individual planets. The galaxy is enormous. We are
rotating what is believed to be a black hole. Current scientific estimates
conclude that there are approximately 100 billion stars in our galaxy alone
with planets orbiting them.
As we travel further into space, the entire galaxy
becomes just a dot of light. Each of those other dots are other galaxies.
Further away, it is possible to see the Virgo
Supercluster. That red notation represents our local galactic group, containing
all of the galaxies near us. In that is the Milky Way galaxy. In that is the solar
interstellar neighborhood. In that is our solar system. In that is planet
Earth.
The local supercluster group contains the virgo
supercluster, where we are located, as well as the other superclusters near us.
That tiny dot that you can hardly make out on the
screen is the Virgo Supercluster. All of those other dots are superclusters.
And this is just the observable universe that we can estimate. It is believed
that there are countless, perhaps even infinite, other dimensions.
Theoretically, planet Earth could have entire civilizations that exist in other
dimensions we can't access or interact with at the present time. Then there is
the issue of time and gravity. If time travel is possible, all of these
universes would be occurring at the same time everywhere in all dimensions.
Imagine the entire history of the universe, from
the Big Bang to the present moment, was one year of time. The 12 billion years
of history compressed down into 12 months, each month represents 1 billion
years.
On this compressed time scale, some notable events
are:
January 1, 12 am
|
Big Bang occurs
|
Early February
|
Our Milky Way
Galaxy forms
|
August 12
(approx.)
|
The Earth and Sun
are formed
|
September 28
(approx.)
|
First life arises
on the Earth
|
December 13
|
First animals
appear on Earth
|
December 25
|
Dinosaurs now
walk the Earth
|
December 30,
12:33 am
|
Dinosaurs wiped
out by asteroid collision
|
December 31, 9:00
pm
|
First humanoid
life appears
|
December 31,
11:58 pm
|
Homo Sapiens
first appear
|
December 31, 11:59
pm + 30 seconds
|
Agriculture
developed
|
December 31,
11:59 pm + 47 seconds
|
Pyramids built
|
December 31,
11:59 pm + 59 seconds
|
Shakespeare
writes plays
|
The universe is so old that all of recorded human
history occupies only the last 13 seconds or so of the year.
There are about ×1079
hydrogen atoms in the observable universe. total mass for the visible universe
of 3.14×1054 kg,
The
universe is commonly defined as the totality of everything that exists, including all physical matter and energy, the planets, stars, galaxies, and
the contents of intergalactic space.
The broadest definition of the universe is simply everything that is created
and everything that is not created.
Discovery
of the red shift and cosmic microwave
background radiation revealed that the universe is expanding and
apparently had a beginning. The high-resolution image from the Hubble ultra
deep field shows a diverse range of galaxies, each consisting of billions
(1000,000,000 or 109) of stars.
According
to the prevailing scientific model of the universe, known as the Big Bang, the universe expanded from an
extremely hot, dense phase called the Planck epoch, in which all the matter and
energy of the observable universe
was concentrated. Since the Planck epoch, the universe has been expanding to
its present form.
Recent
observations indicate that this expansion is accelerating because of some
unexplained force named dark energy, and
that most of the matter in the universe may be in a form of matter which cannot
be detected by present instruments, and so is not accounted for in the present scientific
models of the universe; this has been named dark matter. The imprecision of current
observations has hindered predictions of the ultimate
fate of the universe.
The
most
precise estimate of the universe's age
is 13.73±0.12 billion years old, based on observations of the cosmic
microwave background radiation. The diameter of the observable universe
is at least 93 billion light years.
As the distances between spatial
objects are far larger than the earthly measurements we are familiar with lets
understand a few terms first. Speed of light is about 300,000 KM per Second. An
Astronomical Unit (abbreviated
as AU) is a unit of length equal to
approximately the mean Earth–Sun
distance which is about 149,597,870.7 kilometers or the distance travelled by
light in 499 seconds (8 minutes and 19 seconds).
One
light year is the distance that light travels in a year with its velocity of
300,000 KM per second. Light can travel from earth to moon in 1.28 seconds flat
! Light from the sun will reach the farthest planet Pluto in 5 and 30 minutes.
Light will reach the outer most periphery of the solar gravitational field (the
Oort cloud) in one light year by travelling 9.5 trillion kilometres.. One
trillion is 1 followed by 12 zeroes abbreviated as 1012. One billion
is 109.
To
repeat; light moving at 300,000 KM per SECOND would take 93 billion years to
cross the observable universe as of now. So the universe is quite big after
all! And it is still expanding. No need to try to imagine the size. The mind
may blow up ! So just read the figures, wonder and continue.
According
to general relativity,
space can expand faster than the speed of light (spots on the surface of an
enlarging balloon as example), although we can view only a small portion of the
universe due to the limitation imposed by light speed. Since we cannot observe
space beyond the limitations of light (or any electromagnetic radiation), it is
uncertain whether the size of the universe is finite or infinite. We need light
to see the objects. If the object moves faster than light then we cannot see
it. This is the limitation of the eye. Further scenarios can only be assumed in
the light of what we have already observed / experienced. Those parts of the
universe, if any, which are expanding faster than the speed of light, can not
be traced ever by using equipments that require observable data needing light
as a mandatory condition.
According
to this definition and our present understanding, the universe consists of
three elements: space and time, collectively known as space-time or the vacuum; matter and various forms of energy and momentum occupying space-time; and the physical laws that govern the first two.
The three elements of the universe (space-time, matter-energy, and physical
law) correspond roughly to the ideas of Aristotle.
Is this Universe only one part of a
Multiverse?
It
is possible to conceive of disconnected space-times, each existing but unable to
interact with one another. An easily visualized metaphor is a group of separate
soap bubbles, in which observers living on
one soap bubble cannot interact with those on other soap bubbles, even in
principle. According to one common terminology, each "soap bubble" of
space-time is denoted as a universe, whereas our particular space-time is denoted as the universe, just
as we call our moon the Moon. The entire
collection of these separate space-times is denoted as the multiverse. In principle, the other
unconnected universes may have different dimensionalities and topologies of space-time, different forms of matter and energy, and different physical laws and physical constants,
although such possibilities are currently speculative.
The
universe is immensely large and possibly infinite in volume. The region visible
from Earth (the observable universe)
is a sphere with a radius of about 46 billion light years, based on where the expansion of
space has taken the
most distant objects observed. For comparison, the diameter of a typical galaxy is only 30,000 light-years, and the
typical distance between two neighbouring galaxies is only 3 million light-years.
Some
interesting facts !
No.
|
Between Objects
|
Distance
|
1
|
Moon to Earth
|
1.28 light-seconds
|
2
|
Sun to Earth
|
8.3 light-minutes
|
3
|
Sun to Pluto
|
5 1/2 light-hours
|
4
|
Sun to Oort Cloud
|
1 light-year
|
5
|
Sun to Proxima Centauri (nearest star)
|
4.22 light-years
|
6
|
Diameter of Milky way Galaxy
|
100,000 light years
|
7
|
Milky Way Galaxy to
the
nearest sister galaxy,
the Andromeda Galaxy
|
2.5
million light years
|
8
|
Diameter
of the observable
universe
|
93 billion light years
|
There
are probably more than 100 billion (1011) galaxies in the observable universe.
Typical galaxies range from dwarfs with as few as ten million (107
or one crore to the Indians) stars up to giants with
one trillion
(1012 or One lakh crores) stars, all orbiting the galaxy's centre of
mass. Thus, a very rough estimate from these numbers would suggest there are
around one sextillion (1021)
stars in the observable universe; though a 2010 study by astronomers resulted
in a figure of 300 sextillion (3x1023).
The
observable matter is spread uniformly (homogeneously) throughout the universe,
when averaged over distances longer than 300 million light-years. However,
on smaller length-scales, matter is observed to form "clumps", i.e.,
to cluster hierarchically; many atoms are condensed into stars, most stars into galaxies, most
galaxies into clusters,
super clusters and, finally, the largest-scale
structures such as the Great Wall of
galaxies.
The Great Wall (also called Coma Wall),
is one of the largest known super-structures in the Universe. It is
a filament
of galaxies
approximately 200 million light-years away and has dimensions which measure over 500
million light-years long, 300 million light-years wide and 15 million
light-years thick. In comparison our Milky way galaxy is (only) 1,00,000 light
years across. So the great wall of galaxies is 150 to 5000 times bigger than
the milky way galaxy.
The
observable matter of the universe is also spread isotropically, meaning that no
direction of observation seems different from any other; each region of the sky
has roughly the same content. The universe is also bathed in a highly isotropic microwave radiation.
The
present overall density of the universe
is very low; on the order of a single hydrogen atom for every four cubic meters
of volume. The universe is believed to be mostly composed of dark energy and dark matter, both of which are poorly
understood at present. Less than 5% of the universe is ordinary matter, a
relatively small contribution. This mass-energy appears to consist of 73% dark energy, 23% cold dark matter
and 4% ordinary matter.
The properties of dark energy and dark matter are largely unknown. Dark matter gravitates as 0; by contrast, dark /energy accelerates its
expansion.
The
universe appears to have a smooth space-time
continuum consisting of three spatial dimensions and one temporal (time) dimension.
The
universe appears to behave in a manner that regularly follows a set of physical laws and physical constants.
According to the prevailing Standard Model of physics, all matter is
composed of three generations of leptons and quarks, both of which are fermions. Six leptons and six quarks comprise most of the matter; for example, the protons and neutrons of atomic nuclei are composed of quarks, and
the ubiquitous electron is a lepton.
There is no explanation for the particular values that physical constants
appear to have throughout our universe, such as Planck's constant
(h) or the gravitational
constant (G).
The
universe oscillates between a Big Bang and a Big Crunch.
The
galaxies appear to be flying apart; the space between them is stretching. The
stretching of space also accounts for the apparent paradox that two galaxies
can be 40 billion light years apart, although they started from the same point
13.7 billion years ago and never moved faster than the speed of light.
A
common misconception is that the Big Bang model predicts that matter and energy
exploded from a single point in space and time; that is false. Rather, space
itself was created in the Big Bang and imbued with a fixed amount of energy and
matter distributed uniformly throughout; as space expands the density of that
matter and energy decreases.
Prevailing
model of the origin and expansion of space-time.
The
ultimate
fate of the universe is still unknown. If the universe is
sufficiently dense, the universe will eventually recollapse in a Big Crunch, possibly starting a new
universe in a Big Bounce.
Conversely,
if the universe is insufficiently dense, the universe will expand forever,
cooling off and eventually becoming inhospitable for all life, as the stars die
and all matter coalesces into black holes (the Big
Freeze and the heat death of
the universe).
Recent
data suggests that the expansion speed of the universe is not decreasing as originally
expected, but increasing inexplicably defying the physical laws that we are
aware of. If this continues indefinitely, the universe will eventually rip
itself to shreds (the Big Rip).
Experimentally, the universe has an overall density that is very close to the
critical value between recollapse and eternal expansion.
So
we are living on the edge !
As
the universe expands, the energy density of the electromagnetic
radiation decreases more quickly than does that of matter. Thus, although the energy density of
the universe is now dominated by matter, it was once dominated by radiation. Poetically
speaking, all was light in the beginning !
Religions
have said similarly much earlier !
As
the universe expanded, its energy density decreased and it became cooler; as it
did so, the elementary particles
of matter could associate stably into ever larger combinations. Thus, in the
early part of the matter-dominated era, stable protons and neutrons formed, which then associated into
atomic nuclei. At this stage, the matter in
the universe was mainly a hot, dense plasma of
negative electrons, neutral neutrinos and positive nuclei.
Nuclear reactions
among the nuclei led to the present abundances of the lighter nuclei,
particularly hydrogen, deuterium, and helium. Eventually, the electrons and
nuclei combined to form stable atoms, which are transparent to most wavelengths
of radiation; at this point, the radiation decoupled from the matter, forming
the ubiquitous, isotropic background of microwave radiation observed today.
Other
observations are not answered definitively by known physics. According to the
prevailing theory, a slight imbalance of matter over antimatter was present in the universe's
creation, or developed very shortly thereafter as observed by particle physicists.
Although the matter and antimatter mostly annihilated one another, producing photons, a small residue of matter
survived, giving the present matter-dominated universe.
Multiverse
theory
Depiction
of a multiverse of seven "bubble"
universes, which are separate space-time continua, each having different physical laws, physical constants,
and perhaps even different numbers of dimensions or topologies.
Some
speculative theories have proposed that this universe is but one of a set of
disconnected universes, collectively denoted as the multiverse, altering the concept that the
universe encompasses everything. The disconnected universes are conceived as
being physical, in the sense that each should have its own space and time, its
own matter and energy, and its own physical laws that also challenges the
definition of parallelity as these universes don't exist synchronously (since
they have their own time) or in a geometrically parallel way (since there's no
interpretable relation between spatial positions of the different universes).
If
the observable universe is smaller than the entire Universe (in some models it
is many orders of magnitude smaller), one cannot determine the global structure
by observation: one is limited to a small patch.
In
short the observable Universe is of possibly unlimited size and a human being
of limited and insignificant size in comparison can visualise that infinite
size in mind.
So
what is more amazing? The universe in its sheer size and unending fireworks or
the simple (?!) human mind? Lets not fight over that now. Lets move on ! Need
to know much more now. May be we can fight afterwards !
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