Space Exploration

Space ExplorationHuman understanding of both Earth &

space has changed over time.

Why has our understanding

changed?

Early Views about the Cosmos

For thousands of years…

Humans have watched the heavens in wonder; it has fueled our imaginations, marked the passage of time, and foretold the changes of seasons.

Early knowledge was passed from generation to generation and from culture to culture, often as legends and folklore.

Important events for our

ancestors…Summer & Winter solstice: predictions about the approach of summer & winter were important to early peoples.

Summer Solstice- occurs near June 21 & marks the longest period of daylight in the year- start of summer.

Winter Solstice- occurs near December 21 & marks the shortest day of the year- start of winter.

Sol- Latin for sun

Stice- Latin for stop

Ancient Civilizations

Built huge monuments to honour their beliefs about the change between summer and winter.

Although they only had the unaided eye, their observations about the path of the Sun throughout the year were highly accurate.

Spring & Fall Equinox

From Latin & means equal “equi” night “nox”.

Time when day and night are of equal length.

About March 21 & September 22

Mayans: Chichen Itza equinox snake… built a giant cylinder shaped tower to celebrate the occurrence of the 2 equinoxes about 1000 AD.

EgyptiansBuilt many pyramids to align with the seasonal positions of certain stars.

Aboriginals- Southwest

AlbertaUsed large rocks to build medicine circles; key rocks aligned with the stars that rose in the dawn- Rigel & Sirius

Models of Planetary MotionThe religions, traditions, myths, and rituals of ancient cultures all reveal different interpretations of how the universe works.

Geocentric Model

Aristotle, 2000 years ago

Sun, moon & 5 planets known.

Hypothesized that the reason why distant stars did not move is because they were attached to the outermost sphere (celestial sphere)- like they were glued to an immovable ceiling.

Pythagoras & Euclid

Little optical technology existed in Aristotle’s time, but he was aided by math & geometry.

Geocentric model allowed early astronomers to forecast some events, like the phases of the moon, but left a lot of questions unanswered- like why did Mars, Jupiter & Saturn sometimes “loop back” opposite their usual movement across the sky.

Heliocentric Model

Nicholas Copernicus

1530, Polish astronomer, suggested that the Sun was at the centre and Earth and the other planets revolved around it.

100 years later(ish), the telescope provided solid evidence for Copernicus’ theory.

Galileo Galilei, 1600s

His discoveries added credibility to the Copernican ideas; mountains on the moon, Saturn’s rings, spots on the Sun, moons orbiting Jupiter, phases of Venus.

Johannes Kepler: German mathematician who discovered that the orbits of the planets are ellipses, not circles.

Ellipse: Oval shaped

Fun FactSun is about 149 599 000 km from Earth.

Not very far compared to other distances in the Universe.

But, if you could fly a 747 from Earth to the sun, traveling about 965 km/h, the flight would take 17 years.

Astronomer’s Tools

Sundial is over 7000 years old and is used to measure the

passage of time.

Quadrant2nd Century AD; Egyptian astronomers

designed a quadrant to measure a star’s height above the horizon.

HorizonThe line at which the earth's surface and the sky appear to meet.

AstrolabeArabian

astronomers used the

astrolabe for centuries to

make accurate charts of star

positions.

Cross-staff14th Century- Levi ben Gurson invented

the cross-staff to measure the angle between the Moon and any given star.

Early Telescope

Late 16th Century- revolutionized

astronomy. Astronomers

could suddenly see more in the night sky than had ever been

possible.

Immensity of Time & Distance

in SpaceYou would not measure the the length of our school in millimetres.

Or the distance from your home to school in centimetres.

When measuring distances in space, even kms are not practical; to describe such enormous distances, astronomers devised 2 new units of measure.

Astronomical Units (AU)

Used for measuring “local” distances inside our solar system.

1 AU is equal to the average distance from the centre of the Earth to the centre of the Sun (149 599 000 km).

Light Years

1 light year is equal to the distance light travels in one year.

300 000 km/s - In one year that adds up to 9.5 trillion km. If you wanted to wind a string 1 light-year long around Earth’s equator, you could wrap it around 236 million times!

Proxima Centauri

Next closest start to Earth

after the Sun is a little over 4

light years away.

Looking into the past:

When you look at an object in space, you are seeing it as it was at an earlier time.

Some stars you see no longer exist, but we are only receiving their light now.

Images from the Hubble Space Telescope, launched in 1990, could be showing us images from as far back as 12 billion years.

How long?

Light from the sun, about 8 minutes.

Light from Pluto, about 5 hours.

Light from stars at the centre of our galaxy, about 25 000 years.

Does it take light to reach us…

What is a star?Video

Stars vary a lot in their characteristics: density, size, colour.

Mainly hydrogen

Hot: Blue Cooler: Red

Hertzsprung-Russel Diagram

1920s – 2 scientists discovered that the distribution of star temperature and brightness is not random.

Starts fall into several distinct groupings.

90% of stars fit into the main sequence grouping.

Remember from video:

Stars form in regions of space where there are huge accumulations of gas & dust called nebulae (about 75% hydrogen 23% helium 2% oxygen, nitrogen, carbon & silicate dust).

Some of this interstellar matter came from exploding stars.

Gravity

Causes a small area of the nebula to start collapsing into a smaller, rotating cloud of gas & dust.

As more material is drawn into the spinning ball, the mass at it’s core increases & the temperature climbs.

If the core gets hot enough, it starts to glow. This is called a protostar.

10 000 000 C

Hydrogen starts to change to helium in a process known as fusion.

A star is born.

Life & DeathSun-Like

Main sequence- convert hydrogen to helium

As hydrogen is used up, becomes larger- red giant

White dwarf-fusion reaction stops

Black Dwarf

Massive

Main sequence- convert hydrogen to helium

As hydrogen is used up, becomes larger- red supergiant

Supernova-explodes after core collapses/gravity

Neutron Star/Black hole- highly dense remnant-gravity so great not even light can escape

Black HolesAre invisible to telescopes. We know about them because of how material near a black hole becomes very hot and bright.

ConstellationsTotally made up by farmers, poets, astronomers, etc.

Break the sky up into more manageable pieces.

Grouped into patterns called asterisms.

Think of them as a “map” of the sky.

GalaxyA grouping of millions or billions of stars,

gas & dust held together by gravity. There may be a billion billion galaxies

Spiral Galaxies

From the front looks like it has

long, curved arms; like a cd from the

side.

Young stars provide most of the light in the

arms; older stars in the middle.

Elliptical GalaxyShaped like a football or an egg; made

up of mainly old stars. This picture shows many elliptical galaxies.

Irregular GalaxiesNo noticeable shape and is usually

smaller than spiral or elliptical galaxies; made of a mix of young & old stars.

Our Neighbourhood

The Sun: About 110 times wider than the Earth. That means that if the sun were a hollow ball, it would take almost a million Earths to fill it.

5500 C at the surface; 15 000 000 C at the core.

Solar Wind: The sun releases charged particles that flow out in every direction, which pass Earth at a speed of about 400 km/s.

Earth is protected by its magnetic field.

PlanetsThe planets in our solar system are as different as the people that make up a community.

2 distinct planetary groups

Inner

Terrestrial- Earth-like

Smaller, rockier, closer to the sun

All visited by probes

Mercury, Venus, Earth, Mars

Outer

Jovian- Jupiter

Large, gaseous, and located a great distance from sun

Pluto not visited by probe

Jupiter, Saturn, Uranus, Neptune, Pluto

AsteroidsSmall rocky or metallic bodies travelling in space.

There is a narrow “belt” of asteroids between Mars and Jupiter.

Scientists do not know where they came from.

Range in size, from a few metres to several hundred kilometres across.

Largest, Ceres, is over 1000 km wide.

Comets

Made up of dust & ice, and travel through

space.Long tails & bright glow only appear when they are close to the sun.

Sun heats up materials on the comet & gases are released.

Gases get pushed away from the comet by solar wind & tail is formed.

Some tails can be millions of km long.

Comets that orbit the

sun:Make predictable

appearances because of their elliptical

orbits.

E.g. Halley’s comet is visible from Earth every 76 years.

The last time it was seen was 1986

Meteoroids, Meteors & MeteoritesSmall pieces of rock flying through

space with no particular path.

When one gets pulled into Earth’s atmosphere by gravity, the heat of atmospheric friction causes it to give off light, and it is then known as a Meteor.

If a meteor lasts long enough to hit the Earth, it is called a meteorite.

Hoba West, Nambia

Math really is good for

something!

Describing the position of an

object in space2 questions must be answered…

In which direction? Answered by using the compass direction called the azimuth.

Due north is 0; south is 180; 270 is west (measured in degrees).

Describing the position of an

object in space2 questions must be answered…

How high in the sky is it? Answered by a measurement called the altitude.

Altitude ranges from 0 at the horizon to 90 straight up(measured in degrees).

ZenithHighest point directly overhead.

Objects far, far away

Like some stars, are at such enormous distances from Earth that they appear to stay in one place in the sky.

When observing planets, however, it only takes a few days to see it change its position against the backdrop of stars.

The path in the sky that the Sun appears to move is called the ecliptic.

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