Transcript How ideas of the universe have changed over time

 NASA
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National Aeronautics and Space Administration
 Pioneer
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and Voyager craft
Sent off on missions to transmit images of
Jupiter, Saturn, and outer solar system
No communication from Pioneer craft anymore
Eventually it will be the same for Voyager craft
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Voyager 1 is the most distant human-made object in
space
 Still transmits data! :o
not
only transmission of
data, also have plaques
detailing a man and
woman, the solar system,
and other information
showing where Earth is
located
Each Voyager probe also
has a “golden record”
with recorded sounds and
pictures of Earth
 Each
of the Pioneer space probes that have
left the solar system carries the plaque from
the previous slide.
 It’s hoped that other planetary life forms
that think enough like humans might find one
of the probes and be able to use the plaque
information, even millions of years from now,
to locate Earth.
 We are going to think about the implication
of sending information about humans into
space.
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With your partner(s), discuss the following
questions. Record your thoughts in point form.
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What does our sending information like this out into
space suggest about our own ideas of the universe?
What does the plaque information assume about the
nature of any aliens who might acquire it?
If you were to design your own plaque, what would
you like to put on it? Why?
If the plaque can last a million years, will it outlive
the human race? Explain your answer.
Would aliens capable of finding the plaque already
know about Earth because of our radio transmissions?
Is the most likely finder of the plaque going to be
future human space travellers who have forgotten
their early roots? Explain your answer.
 Our
ancestors used astronomical phenomena
to:
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Mark the passage of time
Foretell the changing seasons
Indicate direction during travels
 Aztecs
and Mayans developed accurate
calendars over generations of observation
and recording
 During the Renaissance (15thc.) relied heavily
on knowledge gathered by Islamic
astronomers for more than 800 years
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Two important annual events for
our ancestors:
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Summer solstice (northern hemisphere)
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Winter solstice (northern hemisphere)
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Near June 21  start of summer
Longest day of the year
Near December 21  start of winter
Shortest day of the year
Solstices are opposite in southern
hemisphere
Stonehenge was used to mark summer
and winter solstices 4500 years ago
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Ancient African cultures also used this
method
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It means a day when the hours of daylight and
hours of night are of equal length.
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Vernal/spring equinox
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Autumnal/autumn equinox
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Around March 21
Around September 21
Mayans built towers (1000CE) to celebrate these
Egyptians built pyramids and monuments to align
with the seasonal position of certain stars
 First Nations used large rocks to build medicine
wheels
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Key rocks were aligned with bright stars that rose at
dawn (Aledebaran, Rigel, Sirius)
 Also used to predict right time of year to
plant/harvest crops or prepare for hunting and fishing
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 Geocentric
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Model
2000+ yrs ago, Earth
was believed to be the
centre of the universe
Using Plato’s work,
Aristotle first described
the earth-centred
(geocentric) model
Stars didn’t move? They
were attached to the
outside sphere
 Geocentric
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motion
Ptolemy helped many
astronomical phenomena
to be forecasted (moon
phases)
Retrograde motion:
apparent reversal o the
planets’ path relative to
the starry backdrop
 Heliocentric
model
Improvements in
technology changed
thinking
 Proposed by Greeks in 500
BCE
 Polish astronomer Nicholas
Copernicus revived the
idea
 Sun is at the centre of our
universe (Sun-centred) and
planets orbited around SUN
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 Two
key things about planetary orbit helped
support the heliocentric (sun-centred) model
Orbital radius
1.
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A planet’s distance from the Sun
The shorter this is, the faster the planet moves in its orbit
 Because of the Sun’s gravity being stronger when you’re
closer to it
Earth is moving faster than Mars, Mars is faster thanJupiter
 100
yrs later, more solid evidence was brought
on by the invention of the telescope (binoculars)
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Galileo Galilei
 Two
key things about planetary orbit helped
support the heliocentric (sun-centred) model
Elliptical orbits
1.
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This model could not predict planetary motion very
accurately, just like the geocentric model
Kepler figured it out
Using much of the observations from his teacher,
Tycho Brahe, found that the planets were
ELLIPSES, NOT CIRCLES
Everyone supports this idea now, and we use
it to study other star-and-planet systems
1.
2.
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4.
In the northern hemisphere, what is the:
(a) summer solstice and when is it?
(b) winter solstice and when is it?
What is the main difference between the
geocentric model and then heliocentric
model?
Define retrograde motion and make a
sketch to support the definition.
The orbits of the planets are not exactly
circular. What shape are they?
 Sundials
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Used for more than 7000 years to measure time
 Quadrant
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Measures the stars’ height above the horizon
 Astrolabe
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Makes accurate charts of star positions
 Cross-staff
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Levi ben Gerson invented this to measure the
angle between the moon and any given star
 Telescope
was invented in the late 16th cent.
 Refracting telescope
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Two lenses gather and focus starlight
Has a size limit (1m diameter)  glass warps
 Reflecting
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telescope
Uses mirrors instead of lenses to collect visible light
Often located high on mountaintops to get the
clearest view
Hubble Space telescope is one of these
Space-based is better than ground-based because
they escape light and air pollution, weather,
 Use
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radio waves emitted by objects in space
Less affected by weather, can detect during day
and night
Radio waves not distorted by clouds, pollution, or
atmosphere like light waves
These telescopes helped establish the BBT by
detecting CBR (microwave radiation leftovers)
Also detected enormously powerful energy sources
at the edge of the visible universe
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Called quasars
 Put out as much energy as a WHOLE GALAXY, but may
not be larger than a solar system
 Don’t know too much about them yet – but we’re
working on it