What we know about the Universe

A celestial body is a natural object out in space such as a planet, a moon, an asteroid, a comet, or a star.

People made note of the movement of the celestial bodies.

People would use celestial bodies the measure the passage of time

Patterns of stars in the skyThe people told stories of kings and

queens, heroes and villains, animals and mythical creatures, and put them in the sky.

Characters from Greek and Roman mythology make up most of the constellations we use today

(including the Big Dipper)

-(including the Little Dipper)

cyclic paths

The sun appears to move across the ecliptic due to the earth movement around the sun

The moon also moves across the sky following the ecliptic on 28 day cycle.

the planets revolve around the Sun

they move at different rates along the ecliptic.

Mercury and Venus are close to the Sun ( seen in the at dawn or dusk)

Outer planets can be seen at all times throughout the night

comets can orbit in different planes.

Different periods

Haley ‘s comet every 75-76 years (1986 to 2061)

Comet Hale-Bopp comes every 2520-2533 years ( 1997- 4527)

The are constellations only visible in the winter.

The are constellations only visible in the summer.

Orion is a winter constellation

Gemini is a summer constellation

Aristotle (383–322 B.C.E.)

A geocentric universe has Earth at the centre and the Sun, Moon, planets, and stars revolving around it

Ptolemy (83–168 C.E.) Aristotle’s model did not

explain all the observed motions

ie. Retrograde motion . A planet appearing to move backwards in the sky for a short time because we pass the planet on the inside.

Ptolemy envisioned each planet not attached directly to its sphere,but attached to an off-centre wheel, which rotated as the sphere turned.

Nicolaus Copernicus (1473–1543),

Copernicus’ model of a heliocentric universe set the stage for other scientists to better understand the universe and to propose their own theories based on his model.

Galileo Galilei (1564–1642)

First person to turn a small telescope toward the heavens

He observed craters on the Moon

spots on the Sun four “stars” orbiting the

planet Jupiter (the moons of Jupiter)

Galileo reasoned that Venus could only have phases if it orbitedthe Sun

Johannes Kepler (1571–1630)

He could describe the motions of the planets more accurately using new technologies to make very accurate observations, then analyzing the data using mathematics.

Kepler developed three laws of planetary motion

Sir Isaac Newton (1643–1727)

the most influential scientist who ever lived

developed three laws to describe and predict motion (Laws of motion)

the first to show mathematically that the force of gravity extends far beyond the surface of Earth (Law of Gravitation)

These same laws govern the motion of stars throughout the Milky Way galaxy.

Stone Circles Ancient observatories for plotting the movement

of celestial bodies

Stonehenge in EnglandBighorn Medicine Wheel Wyoming, U.S.A.

Astrolabe help them locate and predict the positions of the

Sun, Moon, and stars. Measured angles in the sky

Telescope an optical device that uses lenses to gather and focus light to provide a magnified view.

Galileo

Canada-France-Hawaii Telescope

Hubble Space Telescope

Equivalent in angular size to a 65 mm tennis ball at a distance of 100  metresAlmost all of the 3,000 objects in the image are galaxiesWe believe it is the same in all directions