Transcript Saloni

Universe – The Beginning
Astronomers are now fairly sure that the Universe was born 15 billion years ago due to
the Big Bang.
The Big Bang theory tells us how the Universe began and that it is evolving. Basically, it is a theory that
was created to explain two facts that we know about the Universe - it is gradually expanding and
cooling at the same time. In the 1920s, Edwin Hubble found that the galaxies far from our own Milky
Way are moving away from us. So he concluded that the whole Universe must have been expanding.
Working backwards, this means that at one stage, the Universe must have originated from a single
point.
Our Solar System
To reach mercury it takes 5.5 earth
months.
It has the widest range in temperature
of any planet, from a chilly -170°C at
night to a sizzling 350°C during the
day. This is because it has no
atmosphere.
Venus is the brightest object in the sky
after the Sun and Moon. It is the
hottest planet – temperatures can go up
to 480 Celsius. This is because the
gases in the atmospheres act as good
insulators and trap all the heat of the
sun – this is called the greenhouse
effect!
Mars is also called the ‘Red
planet’(after the Roman god of war)
because of its colour. It has the largest
volcano(extinct) in the solar system
and is named Olympus Mons. It is
27km high and 700 km wide!
Scientists believe that one day they
might find life on Mars.
Jupiter is the largest planet in the solar
system. It is a ‘gas giant’. It has the
largest number of moons (about 63).
The surface appears banded because of
belts of clouds. It has a giant red spot(3
times the size of the Earth) – which is
actually the largest storm in the solar
system raging for over 300 years!
Our Solar System
Saturn is the next of the “gas giants’. It
is the least dense planet – it could in
fact float on water if there was an
ocean large enough. It has a
spectacular ring system made of
particles and ice crystals. It took
Voyager II, 29 years to reach Saturn.
Neptune is the fourth gas giant. It also
appears to be blue in colour – though
no one knows why. It also has a system
of rings. It has the wildest weather in
the solar system with winds raging up
to 2000 km per hour!
Uranus is the third largest planet in the
solar system. It is also a gas giant. It
has a blue colour. This is because the
atmosphere has methane gas which
absorbs red light and the blue light is
reflected. It also has rings – but these
are not visible. It is the only planet to
spin on its side.
Pluto is the smallest planet. It is half
the size of the moon. It is also the
coldest planet (temperatures are around
– 200 Degrees Celsius). It has a funny
orbit and for twenty years it is closer to
the sun than Neptune! When this
happens Neptune is the farthest planet
of the solar system. It is made up of
rock and ice.
Beyond the Solar System
Our Solar System was a vast cloud of gas and dust billions of years ago. Comets are made
of the same
material,
a part
of cosmos
at athat
time. TheThe
comets
When
a large
star haswhich
burnt formed
all its fuel,
it explodes
into
Supernova.
stuffconsist
that is of
the
chunks
ofextremely
hydrogen,
ice
dust which
then escaped
the
gravitational
pull
ofin
the Sun
Nebula
is the
Latin
word
forand
‘cloud’.
It
is a cosmic
cloudIfof
gas
and dust
floating
left
becomes
dense
to form
a ‘Neutron
Star’.
this
Neutron
Star
is too
as
it was
being
leftover
masses
the
material
then
startedit orbiting
space.
Nebulae
are These
the basic
building
blocks
outcosmic
of which
starsdue
and
large,
itThe
exerts
aformed.
tremendous
gravitational
pulloftowards
the center
tosolar
which
round
the
Sunbeen
These
are and
called
Comets.
A comet
has
comprising
hydrogen
cornea
systems
have
made.
Bulk
of
the Nebulae
consists
of hydrogen
and that
helium
starts
imploding
further
becomes
even
denser.
It nucleus
becomes
so dense
duewith
to its
and
a tail
of dust
gas.escape
Many
comets
beenhole
discovered
using
powerful
telescopes
a small
percentage
of heavy
metals.
It is have
then
presence
ofathese
metals
that give
the
gravity
even
light and
cannot
it.
Hence
a black
is
region
in space-time
from
available
nowadays.
The most
comet
is the
Halley’s
Comet
which to
was
nebulae
different
Nebulae
are
verycannot
vast.
Sometimes
these
extend
which
nothing
cancolours.
escape.
The famous
black
holes
be
seen but
its presence
can last
be seen in
1986.
Itusing
orbits
round
the
Sun
and appears once in 75 years. As such, it is expected to pass
thousands
of the
light
years
in
extent.
known
radio
telescopes.
the solar system in the year 2061.
Halley’s Comet
This picture is a Nebula
Our Universe – The end
If the expansion continues forever then the Universe is destined for the Big Freeze,
gradually pulled apart into a cold desolate wasteland of dying stars and black holes.
OR
If space stops stretching and springs back on itself, it will shrink until galaxies start colliding in
the Big Crunch - terminating in the mother of all black holes.
OR
The final scenario involves the Universe gradually slowing down to a halt. Eventually the
Universe would succumb to the Big Freeze, it would just take a lot longer.
But before that , in about 4 billion years the Sun will expand and engulf our planet Earth
(become huge, a red giant). Also around the same time, our nearest galactic neighbor,
Andromeda, will start to crash into our own galaxy, the Milky Way. Life on Earth must escape
into space if it is to survive.
This is what it will look like when the universe
collides on itself resulting into a Big Crunch