An Expanding Universe How do we really know what's out there?

An Expanding Universe How do we really know what's out there? Space is a pretty big place and, after all, we've never been farther from earth than our moon. How do we know what the stars are made of?

This is the electromagnetic spectrum. It consists of waves which vary in length from very long (radio waves) to incredibly short (gamma rays visible spectrum – waves that we can see Different wavelengths = different colors ranging from red (long wavelengths) to blue/violet (short wave-lengths).

White light consists of all visible wavelengths together. When white light passes through a prism, a triangular piece of glass or plastic, the different wavelengths are separated and can be seen individually.

This instrument is a spectroscope. This one is attached to a telescope to separate the light from stars into a spectrum of different wavelengths. Scientists can then look for specific patterns of wavelengths.

When any element is heated hot enough it begins to emit light. The pattern of wavelengths emitted by an element are like a fingerprint. Each element emits its own unique pattern. Above you can see the pattern of wavelengths emitted by the element hydrogen. Whenever this pattern is seen in the light coming from a star it means that hydrogen is present on that star. This is called the emission spectrum of hydrogen. Emission spectrum – the pattern of light that comes from an element

Composition of Stars Scientist use spectroscopesto separate the light from stars into a spectrum of different wavelengths. When any element is heated hot enough it begins to emit light. The pattern of wavelengths emitted by an element are like a fingerprint. Each element emits its own unique pattern. What can scientist determine when they look at stars using a spectroscope? Scientist can determine what elements stars are made of when they use a spectroscope.

This is the pattern of wavelengths emitted by iron. When iron is heated until it vaporizes, as in a star, it emits this unique pattern of wavelengths. This is the emission spectrum of iron. Below is the emission spectrum of nitrogen. If scientists see this pattern in the light from a star they know that nitrogen is present.

So by using a spectroscope scientists can analyze all the wavelengths that are emitted by a star and can tell exactly what the star is made of even though it may be thousands of light years away. calcium uranium oxygen

What else can the light from distant stars and galaxies tell us? Blue Shift:When an object such as a star or galaxy is moving towards us the the wavelengths of the light it emits are shifted towards the blue end of the spectrum (frequency is shifted higher). Red Shift:If the object is moving away its light is shifted towards the red end of the spectrum (frequency is shifted lower). This phenomenon is called… Doppler Effect--the shifting of wavelengths due to the relative motion of objects You have experienced the Doppler Effect every time you listen to a car drive by. As the car is approaching the pitch is shifted higher and as it passes and moves away the pitch (frequency) is shifted lower.

1) Universal expansion and Hubble’s Law a) Hubble observed the majority of galaxies are moving away from us and each other b) The farther away, the faster they are moving away from us. c) Red Shift (Doppler Effect): objects moving away from us are tinted red. Objects moving toward us are blue shifted. Link (3:22): What is Red Shift?

EXPANSION OF THE UNVERSE • In astronomy , the Doppler Effect used to determine whether a star or other body in spaceis moving away or towards an object (usually the Earth).

Doppler Effect • Shifting of wavelengths can occur with both sound and light • Doppler effect is easier to observe with sound • With sound you will hear a change in pitch • Imagine an ambulance approaching a person standing on a sidewalk: • As the ambulance moves closer the pitch becomes higher • As the ambulance moves away the pitch becomes lower

The Doppler Effect is used............... > to tell us the speed of a fastball. > to help police to catch people traveling over the speed limit. > permit meteorologists to identify and track storms such as tornados. > analyze the flow of blood through arteries. To sum up (write all of me) ...... If frequency is shifted lower (red shift) it means the object is moving away, If frequency is shifted higher (blue shift) it means something is moving closer, and the amount of shift indicates the speed that object is traveling. How is the Doppler effect used in astronomy?

This is the pattern of wavelengths emitted by the element helium. This is the pattern of wavelengths of helium that is found in the light from distant stars and galaxies. We know it's helium because the pattern is the same but notice that all the wavelengths are shifted towards the red end of the spectrum. What does this mean? First, it means that there is helium on that star and................... second, it means that the star is moving away from us. Red shift!

Remember, the greater the amount of shift, the faster the star is moving! Helium Helium slightly red shifted. Moving away. Helium more red shifted. Moving away even faster!

Blue Red Red Shift – object is moving away Blue Red

Blue Red Blue shift – object is moving closer Blue Red

Blue Red No shift – object is moving same speed Blue Red

ALL of the light from stars and galaxies that reaches the earth has a red shift. What does that mean? It means that everything is moving away from us! How can everything be moving away from us? The only explanation for that is ............................................. THE UNIVERSE IS EXPANDING! And if the universe is expanding, then long ago it must have been much smaller. The expansion began about 13 billion years ago with the................. BIG BANG!

Big Bang: Chronology ~several hundred thousand years later • Atoms formed (mainly Hydrogen but also some Helium). • The early Universe was about 75% Hydrogen and 25% Helium. It is still almost the same today. Hydrogen Atom Helium Atom

Big Bang: Chronology ~200 to 400 million years later • First stars formed (due to gravity and nuclear fusion). • First galaxies formed (due to gravity).

The Big Bang Theory • All mass and energy was concentrated in a small area that started expanding with a big explosion; the Big Bang, about 13 billion years ago. • Since this time, it has continued to expand. • Matter began to organize, first forming hydrogen and helium atoms. • Then matter clumped together forming stars and galaxies.

The big bang… • Today, the universe is still expanding and the galaxies continue to move apart from one another. Ex- imagine a blueberry muffing cooking in the kitchen oven. -if you were able to sit on an individual blueberry, you would see all the other blueberries moving away from you. The farther away one blueberry is from another, the faster they move away from each other.

Gravity forms stars from clumps of hydrogen. Clumps of hydrogen atoms were pulled together by gravity. Next, gravity caused nuclear fusion to occur, and a new star was “ignited.” This is how our sun was formed

To understand the Big Bang just imagine that the galaxies are located on the surface of an inflating balloon. As the balloon expands, every point on its surface is moving away from every other point. So what can we learn from the light from stars? We can find out what stars are made of by examining the spectra. We can tell that they are moving away from us and that............... The universe is expanding. We can calculate the speed of that expansion and........................ And we can infer the age of the universe (13-14 billion years). All this just from starlight!

The RED end of the spectrum is made of INFRARED waves The BLUE/VIOLET end of the spectrum is made of ULTRAVIOLET waves Redshift means wavelengths are getting longer Blueshift means wavelengths are getting shorter

EVIDENCE for the Big Bang: • Doppler Effect- • Stars and galaxies show redshift (moving away from us) • Moving away in all directions • Cosmic Background Radiation- • The heat energy from the expansion produces radiation. • This electromagnetic energy is detected all through the universe. • Sometimes called “Cosmic Microwave Background” (CMB)

Bits & Pieces to make sure you know… • The big bang is called a moment of “singularity” – when all energy was concentrated at a single moment of heat, density, and pressure • Einstein’s theory of relativity E=mc2 • -says that energy and matter can be converted into one another • Light Years- distance in the universe is measured in light years (distance light can travel in 1 year) • 1 light year = 6 trillion miles • EX: the nearest star to earth is 4 light years away

An Expanding Universe How do we really know what's out there?