Origin of the Universe8 . 8 D – MO DE L A ND DE SCR IB E HO W L IG HT YE A R S A R E USE D TO ME A SURE DISTA NCES A ND SIZ E S IN T HE UNIVE R SE

How the universe began

•What evidence supports scientific theories on the origin of the universe?

•Video: The beginning of everything (6 min)

Scientific Theories about the beginning:

• Astronomers combine mathematical models with observations to develop workable theories of how the Universe came to be.

• The mathematical underpinnings of the Big Bang theory include Albert Einstein's general theory of relativity along with standard theories of fundamental particles.

• Today NASA spacecraft such as the Hubble Space Telescope and the Spitzer Space Telescope continue measuring the expansion of the Universe.

• One of the goals has long been to decide whether the Universe will expand forever, or whether it will someday stop, turn around, and collapse in a "Big Crunch?"

Big Bang Theory• Once it was understood that the Universe had a beginning, scientists

began to ask “how did it come into existence, and what existed before it?”

• Most scientists now believe that the answer to the first part of the question is that the Universe sprang into existence from a singularity -- a term physicists use to describe regions of space that defy the laws of physics. We know very little about singularities, but we believe that others probably exist in the cores of black holes.

• The second part of the question, as to what existed before the Big Bang, has scientists baffled. By definition, nothing existed prior to the beginning, but that fact creates more questions than answers. For instance, if nothing existed prior to the Big Bang, what caused the singularity to be created in the first place?

The growing universe:

• Once the singularity was created (however it happened), it began to expand through a process called inflation. The Universe went from very small, very dense, and very hot to the cool expanse that we see today. This theory is now referred to as the Big Bang, a term first coined by Fred Hoyle during a British Broadcasting Corporation (BBC) radio broadcast in 1950.

• Interestingly, there really wasn’t any sort of explosion (or bang) as the name suggests, but rather the rapid expansion of space and time.

• It is like blowing up a balloon, as you blow air in, the exterior of the balloon expands outward.

What is IN space?

GALAXIES!

VIDEO:

What makes our little “blue dot” special?

•Why and how do we exist?

•Class Discussion - Someone - Explain our solar system to everyone

The Milky Way

• The Milky Way is a cluster of stars, known as a galaxy

• It contains hundreds of billions of stars

• If you traveled at the speed of light for about 2 million years, you would reach the next galaxy – the Andromeda Galaxy

• There are billions of galaxies in the universe and they are VERY far apart from each other!

Distance to Stars

• Astronomers use light-years and astronomical units to measure distance

• A light-year is the distance that light travels in one year

• In space, light travels at a speed of 300,000km per second

• A light year is about 6 trillion miles or 9.5 million million km

Light Years Explained

MIT camera captures light at a

trillion frames per second

Key Idea

The light-year is a unit of distance, not time!

How long does it take light to get from the Sun to the Earth?

8 minutes

It takes 16 minutes to go there and back

Stars• If A light year is the

distance light travels in a vacuum in one year (An Earth year that is, 365.25 days), then how far apart are all of these stars within ONE galaxy?

Start with our own galaxy - The Milky Way Galaxy is

about 100,000 light years across, we are about 26,000

light years away from the center.

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Measurements in Space: Astronomical Unit

• The distance of the Sun to the Earth is called an Astronomical Unit (AU) and is sometimes used to denote large distances that are less than a light year

• Distances within our universe are measured in light years and AU

A light year = about 63,241 astronomical units

93,000,000 Miles1 Astronomical Unit (AU)

Sun to Earth Distance

Body AU

Mercury .39

Venus .72

Earth 1.0

Mars 1.5

Jupiter 5.2

Saturn 9.5

Uranus 19.2

Neptune 30.1

Pluto 39.5

Other planet distances in astronomical units (from the sun to that planet)

What do you notice about the table?

What number is Earth?

WHY?

Check for understanding: #1

• If the nearest star is 4 light years away how many miles away is it?

A light year means 6 trillion miles.

Think about that for a moment. If you go outside tonight and shine a flash light at the sky, in the next year that light will travel 6 trillion miles.

6 trillion x 4 light years = 24 trillion miles!

Check for understanding: question 2

•How long will it take for the light from that star (that is 4 light years away) to travel to the Earth?

Four years.

Remember, a light year is the distance that light can travel IN A YEAR!

Light Year and Time

• Using a light year as a distance measurement has another advantage -- it helps you determine age.

• Let's say that a star is 1 million light years away. The light from that star has traveled at the speed of light to reach us. Therefore, it has taken the star's light 1 million years to get here, and the light we are seeing was created 1 million years ago.

• So the star we are seeing is really how the star looked a million years ago, not how it looks today. In the same way, our sun is 8 or so light minutes away. If the sun were to suddenly explode right now, we wouldn't know about it for eight minutes because that is how long it would take for the light of the explosion to get here.

How big is the solar system?

USING SCIENCE MODELS

What makes our little “blue dot” special?

•Why and how do we exist?

•Someone - Explain our solar system to everyone

How big is Earth?

Let’s start by looking at the planets and other celestial bodies in the system. I want to start with our home planet.

Earth is 8,000 miles

wide! It is hard to grasp

how big that is because

we live ON it!

How big is Earth?

• How can we compare 8,000 miles to something we know?

It’s about 3 times the length of the United States.

Times 3!

How big is Earth?

•Driving:

It would take you about 6 days to drive the United States once, so 12 days to do it twice and 18 days to drive it 3 times!

How big is Earth?

•Walking:

The average stride length is 2.5 feet

….approximately 2000 steps per mile…times 8000

miles equals approx. 16 MILLION STEPS!

What about the other planets?

How do they compare in size to the Sun or to Earth? How about to each other? Can you REALLY picture the dimensions of the solar system?

Making a Model

Science Models

•Take a look at the model I have.

Do you think that the model is accurate?

What would have to change to make it

accurate?

Making a Model of SCALE

•How can we begin to understand the SCALE of space in the universe?

Distances in Space:

• Even in our own “cosmic neighborhood,” distances in space are so vast that they are difficult to imagine. In this activity, we will build a scale model of the distances in the solar system using a roll of toilet paper.

• That’s right – good ol’ TP!

Distances in Space:

• Instructions:

Are we alone? Is it possible???• Activity:

Videos for activity:

• Fermi paradox (6.5 min)

• Drake Equation (4 min)