The document discusses orders of magnitude and scale in the universe. It begins by comparing sizes of fundamental particles like atoms and nuclei to larger structures like bacteria, humans, Earth, the Sun, solar systems, galaxies, and the observable universe. It then discusses densities and distances at both small atomic scales and large cosmic scales, noting that matter is sparsely distributed at both extremes. The document goes on to define concepts like the speed of light, light-years, and how observing distant objects means seeing them in the past due to the long travel time of light across immense distances in the universe.

1. Seconde F
The Universe

2. Order of Magnitude

3. Order of Magnitude

4. Order of Magnitude

5. Order of Magnitude

6. Order of Magnitude

7. Order of Magnitude

8. Order of Magnitude

9. Order of Magnitude

10. Order of Magnitude
1 Gm = 1 gigameter = 10^9 meters = 1 000 000 000 m

11. Order of Magnitude
1 Gm = 1 gigameter = 10^9 meters = 1 000 000 000 m
1 nm = 1 nanometer = 10^(-9) meter = 0.000000001 m

12. Order of Magnitude

13. Order of Magnitude
nucleus
Nucleus of an atom

14. Order of Magnitude
Atom

15. Order of Magnitude
Bacteria

16. Order of Magnitude
Humans

17. Order of Magnitude
Earth

18. Order of Magnitude
Sun

19. Order of Magnitude
Solar System

20. Order of Magnitude
Interstellar distance

21. Order of Magnitude
Galaxy

22. Order of Magnitude
Observable universe

23. Order of Magnitude
1000 kg 1 Kg

24. Order of Magnitude
1000 kg 1 Kg

25. Order of Magnitude

26. Order of Magnitude
Filling of space by the matter is essentially incomplete, at
both tiny (atom) and big (cosmos) scales
(essentially void around us)

27. Speed of light
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28. Speed of light
 Speed of light in vacuum is a phyical constant :
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29. Speed of light
 Speed of light in vacuum is a phyical constant :
c = 3.10^8 m/s = 300 000 000 m/s
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30. Speed of light
 Speed of light in vacuum is a phyical constant :
c = 3.10^8 m/s = 300 000 000 m/s
 The light is composed of photons


31. Speed of light
 Speed of light in vacuum is a phyical constant :
c = 3.10^8 m/s = 300 000 000 m/s
 The light is composed of photons
and is propagated in straight line

32. Speed of light
 Speed of light in vacuum is a phyical constant :
c = 3.10^8 m/s = 300 000 000 m/s
 The light is composed of photons
and is propagated in straight line
A.Einstein 1879 - 1955

33. Speed of light
 Speed of light in vacuum is a phyical constant :
c = 3.10^8 m/s = 300 000 000 m/s
 The light is composed of photons
and is propagated in straight line
A.Einstein 1879 - 1955
 Speed of light (speed of propagation) depends
only on the medium

34. Speed of light
 Speed of light in vacuum is a phyical constant :
c = 3.10^8 m/s = 300 000 000 m/s
 The light is composed of photons
and is propagated in straight line
A.Einstein 1879 - 1955
 Speed of light (speed of propagation) depends
only on the medium
 speed(vacuum) = speed(air) = c = 3.10^8 m/s
 speed(water) < c

35. Speed of light
 Speed of light in vacuum is a phyical constant :
c = 3.10^8 m/s = 300 000 000 m/s
 The light is composed of photons
and is propagated in straight line
A.Einstein 1879 - 1955
 Speed of light (speed of propagation) depends
only on the medium
 speed(vacuum) = speed(air) = c = 3.10^8 m/s
 speed(water) < c
 Refraction index n : quantity without unit

36. Speed of light
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37. Speed of light
 Galilée, Romer, Cassini, Newton, Michelson..
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38. Speed of light
 Galilée, Romer, Cassini, Newton, Michelson..
using astronomy

39. Speed of light
 Galilée, Romer, Cassini, Newton, Michelson..
using astronomy
 The meter is the distance travelled by the light
in the void during 1/299 792 458 second

40. Speed of light
 Galilée, Romer, Cassini, Newton, Michelson..
using astronomy
 The meter is the distance travelled by the light
in the void during 1/299 792 458 second

41. Speed of light
 Galilée, Romer, Cassini, Newton, Michelson..
using astronomy
 The meter is the distance travelled by the light
in the void during 1/299 792 458 second
m
v = c (m/s) s

42. Speed of light

43. Speed of light
d = 1m

44. Speed of light
d = 1m

45. Speed of light
d = 1m
s m
m/s

46. Speed of light
d = 1m
s m
m/s

47. Speed of light
d = 1m
d = 150 000 000 Km
s m
m/s

48. Speed of light
d = 1m
d = 150 000 000 Km
s km
s m
km/s
m/s

49. Speed of light
d = 1m
d = 150 000 000 Km
s km
s m
km/s
m/s
Even if the light of speed is great, the gigantic distances at the
cosmos scale cause delays (we don’t see things in ‘real time’)

50. Light-year
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51. Light-year
 A light-year is the distance travelled by the
light in vacuum during one year

52. Light-year
 A light-year is the distance travelled by the
light in vacuum during one year

53. Light-year
 A light-year is the distance travelled by the
light in vacuum during one year
m
s
m/s

54. Light-year
 A light-year is the distance travelled by the
light in vacuum during one year
m
s
m/s
1 year converted in seconds

55. Light-year
 A light-year is the distance travelled by the
light in vacuum during one year
1 ly
m
roughly
s
m/s
1 year converted in seconds

56. Light-year
 A light-year is the distance travelled by the
light in vacuum during one year
1 ly
m
roughly
s
m/s
1 year converted in seconds
The light-year (ly) is not a new unit, it’s used only because it’s
handy with the gigantic distances we have in the cosmos

57. Light-year

58. Light-year
How far are we
from this planet?
I see dinosaurs

59. Light-year
How far are we
Extinction of the dinosaurs : from this planet?
65 millions years ago
I see dinosaurs

60. Light-year
How far are we
Extinction of the dinosaurs : from this planet?
65 millions years ago
I see dinosaurs
The aliens are at least
65 000 000 light-years away
from us
(6.5 * 10^22 meters)

61. Light-year
How far are we
Extinction of the dinosaurs : from this planet?
65 millions years ago
I see dinosaurs
The aliens are at least
65 000 000 light-years away
from us
(6.5 * 10^22 meters)
Watch far = Watch in the past

62. Light-year
 Questions ?
 Homework