Space Exploration

1. Space Exploration Human understanding of both Earth & space has changed over time.

2. Why has our understanding changed?

3. Early Views about the Cosmos

4. 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.

5. 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.

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

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

12. Geocentric Model

13. 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.

14. 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.

15. Heliocentric Model

16. Nicholas Copernicus • 1530, Polish astronomer, suggested that the Sun was at the centreand Earth and the other planets revolved around it. • 100 years later(ish), the telescope provided solid evidence for Copernicus’ theory.

17. 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.

18. Ellipse: Oval shaped

19. Fun Fact • Sun 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.

20. Astronomer’s Tools Sundial is over 7000 years old and is used to measure the passage of time.

21. Quadrant 2nd Century AD; Egyptian astronomers designed a quadrant to measure a star’s height above the horizon.

22. Astrolabe Arabian astronomers used the astrolabe for centuries to make accurate charts of star positions.

23. Cross-staff 14th Century- Levi ben Gurson invented the cross-staff to measure the angle between the Moon and any given star.

24. Early Telescope Late 16th Century- revolutionized astronomy. Astronomers could suddenly see more in the night sky than had ever been possible.

25. Immensity of Time & Distance in Space • You 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.

26. 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).

28. Light Years • 1 light year is equal to the distance light travel 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!

29. Proxima Centauri Next closest start to Earth after the Sun is a little over 4 light years away.

30. 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.

31. 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…

32. What is a star? • Video • Stars vary a lot in their characteristics: density, size, colour. • Mainly hydrogen • Hot: Blue Cooler: Red

34. 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.

35. 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.

36. 10 000 000 C • Hydrogen starts to change to helium in a process known as fusion. • A star is born.

37. Life & Death Sun-Like 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 • Main sequence- convert hydrogen to helium • As hydrogen is used up, becomes larger- red giant • White dwarf-fusion reaction stops • Black Dwarf

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

39. Constellations • Totally 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.

42. Galaxy A grouping of millions or billions of stars, gas & dust held together by gravity. There may be a billion billion galaxies

43. 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.

44. Elliptical Galaxy Shaped like a football or an egg; made up of mainly old stars. This picture shows many elliptical galaxies.

45. Irregular Galaxies No noticeable shape and is usually smaller than spiral or elliptical galaxies; made of a mix of young & old stars.

46. 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.

48. Planets • The planets in our solar system are as different as the people that make up a community.

49. 2 distinct planetary groups Inner Outer Jovian- Jupiter Large, gaseous, and located a great distance from sun Pluto not visited by probe Jupiter, Saturn, Uranus, Neptune, Pluto • Terrestrial- Earth-like • Smaller, rockier, closer to the sun • All visited by probes • Mercury, Venus, Earth, Mars

50. Asteroids • Small 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.