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 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.

Thank you for your attention!