Introduction to the Universe

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Introduction to the Universe
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How was the homework (article questions)

1. Very easy
2. Somewhat easy
3. Medium
4. Hard
5. Super hard

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Topics in this presentation

• Astronomical numbers
• Light travel time
• Composition of universe
• Why the composition changes
• What causes the change?
• Sizes, distances, and ages
• Motions
• Expanding universe, how we measure age

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Astronomical numbers

• 1 million 1,000,000 106. 1 million sec 11.6
  days
• 1 billion 1,000,000,000 109 (aka. Giga or G).
  1 giga-sec
• 31.8 years.
• 1 light sec distance light travels in
• 300,000 km 186,000 miles. Almost to the Moon.
• 1 light year distance light travels in one year
• 1 light year 6 trillion miles.
• Nearest star to Sun 4.3 light-years away.
• The Sun, all 8 planets are about 4.6 Gyr old.
• How many years is that?
• Universe everything in it is 13.7 Gyr old

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Astronomers can detect a galaxy that is 10
billion light-years away.

1. True
2. False

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Will it ever be possible to see something 20
billion LY away?

1. Yes
2. No

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Finding baby senior citizen galaxies

• Talk to your neighbor for 1 minute and answer
  these
• Where would astronomers need to look to find
  galaxies in their earliest stages of life
  (babies)?
• Where would we find galaxies in their later
  stages (senior citizens)?

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Where would astronomers need to look to find
galaxies in their earliest stages of life
(babies)?

1. Nearby
2. Far away

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Picture

• FOR MORE HELP
• See figure 1.5 on p. 8.

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Composition of the Universe
Overall 26 4 22 73

• Stuff in universe (matter)
• Regular matter
• Hydrogen (often gas) 73
• Helium (often inert gas) 25
• Everything else 2
• Oxygen, Carbon, Iron, Sulfur, Neon, Potassium,
  etc.
• Gold, silver, platinum are VERY rare.
• Dark matter
• Matter we cant see. Infer its existence many
  ways. Not elements. (regular)
• Dark Energy
• Energy we cant see. Infer its existence by
  studying expansion of universe.

(half is invisible or hiding)
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Another visual of universes composition
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What grade do astronomers get for understanding
the universe?

1. A
2. B
3. C
4. D
5. F

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Normal matter

• Everything you know about is made of a few
  elements
• Hydrogen, Helium, Carbon, Nitrogen, Oxygen, Gold
• Most things are molecules 2 atoms
• Water (H2O), Carbon dioxide (CO2)
• Science tells us right after the Big Bang, the
  universe only had 2 elements
• Hydrogen (75), Helium (25)
• TINY bit of 1-2 more.
• Where did everything else come from?
• Book calls it recycling.
• Only makes up 2 of matter. But thats enough to
  form planets like Earth, luckily.

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How is the amount of heavy elements in the
universe changing?

1. Increasing
2. Decreasing
3. Staying the Same

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Ages of a few things

• When things formed
• The Big Bang 13.7 billion years ago
• The Sun Earth 4.6 billion years ago
• The Milky Way galaxy 12-13 billion years ago
• See the calendar discussion on page 14.

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Sizes Distances

• Planet order sizes with hands
• In the Voyage scale model, 10 billion1
• Sun is the size of a large grapefruit
• Earth is the size of 1mm, located 50 ft from Sun
• Moon is ¼ Earths size, located 1.5 inches from
  Earth
• Jupiter is
• Pluto is
• Nearest star is named , size dist
• Size of Milky Way is
• Light travel times to these objects

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Are you moving right now?

1. Yes
2. No

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Motions

• Daily motion Earths rotation once per __
• Speed varies ___ for Santa, 1000 mph for Ecuador
• Yearly motion Earths revolution once per __
• Distance 1AU ____
• Speed average 66,000 mph
• Direction tilted 23.5 relative to rotation.
• Sun orbits Milky Way center once per 230 Myr
• 28,000 ly radius, speed 500,000 mph
• Studying this motion ? dark matter discovered
• Galaxies moving relative to each other.
• Nearest galaxies get closer to us. Most move away.

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Does everyplace on Earth take 24 hours to make
one circle around the Earth?

1. Yes
2. No

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Galaxies outside the Local Group are moving

1. Towards us
2. Away from us
3. Randomly towards away

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Expanding universe means objects are getting
_________?

1. Further apart
2. Bigger
3. Both further apart and bigger

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Expanding universe

• Gravity and other forces hold THINGS together.
• Expansion refers to space between galaxies
• Objects dont grow because held together
• We see things moving away
• Speed away from us depends on distance
• Objects twice as far are moving twice as fast
• Objects 100x further are moving 100x faster
• This rule is now called Hubbles Law
• Lets see how Hubbles law works with cars

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Car expanding universe

• Car 1 is 60 miles away and travels 30 mph
• Car 2 is 120 miles away. How fast is it moving if
  it follows Hubbles Law?
• Car 3 is 240 miles away. How fast?
• How long since Car 1 left you?
• Car 2?
• Car 3?
• How old is the car universe?
• This is exactly what we see with galaxies, except
  the time is _________ years.

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Which of the properties below do astronomers need
to measure about galaxies to determine the age of
the universe? Select all that apply. DONT VOTE
UNTIL YOUVE MADE YOUR FINAL DECISION.

1. Composition
2. Speed
3. Distance
4. Brightness
5. Luminosity
6. Number of stars

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Is the composition of the universe changing?

1. Yes
2. No

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Summary

• Astronomical numbers
• Light travel time
• Composition of universe
• Why the composition changes
• What causes the change?
• Sizes, distances, and ages
• Motions
• Expanding universe, how we measure age