Aim: Astronomy - Introduction Notepack 21 Aim: Astronomy - Introduction Do Now: Write down what you think the Big Bang is?

In the beginning….. (don’t Write) Humans have been looking up into the sky ever since they had self awareness. Some cultures believed that the stars in the sky where dead ancestors who looked down at them from heaven. Some cultures believe that the Sun and the Moon were gods, who needed to be worshipped. Some culture looked at the movements of the stars and the planets can predict the future. Some people used these constellations to predict the best time to plant crops or to migrate to new locations. It wasn’t long ago, that people believed that the Earth was the center of the Universe and that the sky moved around it.

What is the Universe? The Universe is commonly defined as the totality of everything that exist, including all matter (atoms) and energy, the planets, stars, galaxies and everything in between them including the emptiness of space.

How did the universe form? It is believed that about 13.7 billion years ago, the entire universe was compressed into a hot super massive ball of matter and energy. At some point, this ball exploded; causing all the material of the ball to expand outward at great speed and temperature. This expansion of material formed the Universe. This explanation of how the Universe was formed is known as the Big Bang Theory.

What happened after the Big Bang? At first, there was energy and charged subatomic particles bouncing around. After 3 minutes electron, protons and neutrons started to form. After 15 minutes, the first atoms (hydrogen) began to form. 300,000 yrs big clouds of hydrogen gas begin to collect and begin to glow. 1 million years, the first stars formed. 1 billion yrs large areas of gases and stars begin to swirl forming galaxies. 13 billion yrs planets begin to form.

Did the Big Bang really happen? Although no one was alive to witness the birth of the universe, there is a lot of evidence that support the theory such as: Background Radiation & Faint Radio Signals Red shift

Background Radiation & Faint Radio Signals Using sensitive equipment scientists are able to detect small amount of radiation, which is the leftover energy from the Big Bang. Radio antennae pick up static signals from all directions in space. This sound is believed to be the sound of the expanding gases from the Big Bang.

Don’t Write The static you hear when you are between channels on the radio or on TV is cosmic radio waves.

https://ak7.picdn.net/shutterstock/videos/4299557/preview/stock-footage-static-tv-noise-no-or-low-signal-with-sound.mp4

Red Shift Galaxies and stars give off energy (in the form of electromagnetic waves) from all directions at equal amounts. As these galaxies and stars move, waves that come out from the “front” of the galaxy/star get compressed, forming a slightly shorter wave length. Waves coming from the “rear” of the galaxy/star become stretched, forming a slightly longer wave length. This compressing and stretching of waves is known as the Doppler effect. The compressing and stretching of electromagnetic waves is known as the Red/Blue Shift.

Equal wave lengths Equal wave lengths Short wave lengths Long wave lengths

Red Shift (cont.) As a galaxy moves away from Earth it causes sensitive equipment to see the galaxy as slightly red. This is because the color red has a long wave length. If the galaxy is moving towards Earth, it will cause instruments to see it as slightly blue or violet. This is because these colors have short wave lengths. Because all galaxies we see in the sky tend to have a red tint when viewed from Earth, we assume that these galaxies are moving away from us.

Doppler Effect http://www.youtube.com/watch?v=Kg9F5pN5tlI

Will the Universe continue to expand? There are 2 possible futures for the universe: One possibility is that the universe will continue to expand until it is so spread apart that we will be un able to see any stars at night because they are too far away. This is called the open universe theory. The second possibility is that the universe will reach a point were gravity begins to pull on everything in it: causing the expansion to slow down. Eventually, everything will begin to reverse its direction and collapse onto itself. This is called the closed universe theory.

Open Universe Model Closed Universe Model