NASANational Aeronautics and Space

Administration Pioneer and Voyager craft

Sent off on missions to transmit images of Jupiter, Saturn, and outer solar system

No communication from Pioneer craft anymoreEventually it will be the same for Voyager craft

Voyager 1 is the most distant human-made object in spaceStill 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 locatedEach 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.

With your partner(s), discuss the following questions. Record your thoughts in point form. 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: 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

Two important annual events for our ancestors: Summer solstice (northern hemisphere)

Near June 21 start of summer Longest day of the year

Winter solstice (northern hemisphere) 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 Ancient African cultures also used this

method

It means a day when the hours of daylight and hours of night are of equal length. Vernal/spring equinox

Around March 21 Autumnal/autumn equinox

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 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

Geocentric Model2000+ 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 motionPtolemy 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

Two key things about planetary orbit helped support the heliocentric (sun-centred) model1. Orbital radius

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) Galileo Galilei

Two key things about planetary orbit helped support the heliocentric (sun-centred) model1. Elliptical orbits

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. In the northern hemisphere, what is the:(a) summer solstice and when is it?(b) winter solstice and when is it?

2. What is the main difference between the geocentric model and then heliocentric model?

3. Define retrograde motion and make a sketch to support the definition.

4. The orbits of the planets are not exactly circular. What shape are they?

Sundials Used for more than 7000 years to measure

time Quadrant

Measures the stars’ height above the horizon Astrolabe

Makes accurate charts of star positions Cross-staff

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

Two lenses gather and focus starlight Has a size limit (1m diameter) glass warps

Reflecting 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 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 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