Download The Universe

Prepared a presentation
Teacher of English
Anisova Julia Vladimirovna
The Big Bang
Most astronomers believe the Universe began in a Big Bang
about 14 billion years ago. At that time, the entire Universe was
inside a bubble that was thousands of times smaller than a
pinhead.
It was hotter and denser than anything we can imagine. hen it
suddenly exploded. The Universe that we know was born. Time,
space and matter all began with the Big Bang. In a fraction of a
second, the Universe grew from smaller than a single atom to
bigger than a galaxy. And it kept on growing at a fantastic rate.
It is still expanding today.
No one knows the exact size of the Universe, because we cannot
see the edge – if there is one. All we do know is that the visible
Universe is at least 93 billion light years across. (A light year is
the distance light travels in one year – about 9 trillion km.)
The Universe has not always been the same size. Scientists
believe it began in a Big Bang, which took place nearly 14
billion years ago. Since then, the Universe has been expanding
outward at very high speed. So the area of space we now see is
billions of times bigger than it was when the Universe was very
young. The galaxies are also moving further apart as the space
between them expands.
The birth of galaxies
We cannot see anything that happened during the first 300 000
years of the Universe. Scientists try to work it out from their
knowledge of atomic particles and from computer models.
The only direct evidence of the Big
Bang itself is a faint glow in space.
Spacecraft and telescopes on balloons
see this as a patchy pattern of slightly
warmer and cooler gas all around us.
These ripples also show where the
hydrogen clouds were slightly denser.
As millions of years passed, the dense
areas pulled in material because they
had more gravity. Finally, about 100
million years after the Big Bang, the
gas became hot and dense enough for
the first stars to form.
What is space?
In space, no one can hear you scream.
This is because there is no air in space –
it is a vacuum. Sound waves cannot
travel through a vacuum.
‘Outer space‘ begins about 100 km above
the Earth, where the shell of air around
our planet disappears. With no air to
scatter sunlight and produce a blue sky,
space appears as a black blanket dotted
with stars. Space is usually regarded as
being completely empty. But this is not
true. The vast gaps between the stars
and planets are filled with huge amounts
of thinly spread gas and dust. Even the
emptiest parts of space contain at least a
few hundred atoms or molecules per
cubic metre.
The Universe
The Universe is everything we can touch, feel, sense, measure
or detect. It includes living things, planets, stars, galaxies, dust
clouds, light, and even time. Before the birth of the Universe,
time, space and matter did not exist.
The Universe contains billions
of galaxies, each containing
millions or billions of stars.
The Universe is incredibly huge.
It would take a modern jet
fighter more than a million years
to reach the nearest star to the
Sun. Travelling at the speed of
light (300,000 km per second), it
would take 100,000 years to
cross our Milky Way galaxy
alone.
Black Holes
Black holes are the strangest objects in the Universe. A black hole
does not have a surface, like a planet or star. Instead, it is a region
of space where matter has collapsed in on itself. This catastrophic
collapse results in a huge amount of mass being concentrated in
an incredibly small area.
The gravitational pull of this region is so great that nothing can
escape – not even light. Although black holes cannot be seen, we
know they exist from the way they affect nearby dust, stars and
galaxies. Many of them are surrounded by discs of material.
As the discs swirl around them like a whirlpool, they become
extremely hot and give off X-rays. Black holes come in many
different sizes. Many of them are only a few times more massive
than the Sun.
The mystery of the dark Universe
Ordinary matter makes up everything we can see, smell or
touch. This matter – which is made from atoms – also makes up
planets and stars.
All objects made of atoms pull on each other according to how
much matter they contain. This is why a small, low mass object
such as an apple falls towards a much more massive object - the
Earth.
Only about 15% of the matter in the Universe is made of atoms.
The remainder is dark matter. However, no one knows what
dark matter is made of. We do know that it does not absorb, emit
or reflect light, because none of our scientific instruments can
directly detect it.
Many scientists believe that most dark matter is some unknown
subatomic (smaller than an atom) particle that interacts only
very weakly with normal matter. If this is true, billions of these
particles will have passed through your body by the time you
finish reading this article. Experiments buried deep underground
may one day capture a few of these particles, finally solving the
mystery of what dark matter really is.