The Universe

Seconde F

Order of Magnitude

Order of Magnitude

Order of Magnitude

Order of Magnitude

Order of Magnitude

Order of Magnitude

Order of Magnitude

Order of Magnitude

Order of Magnitude

1 Gm = 1 gigameter = 10^9 meters = 1 000 000 000 m

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

Order of Magnitude

Order of Magnitude

Nucleus of an atom

nucleus

Order of Magnitude

Atom

Order of Magnitude

Bacteria

Order of Magnitude

Humans

Order of Magnitude

Earth

Order of Magnitude

Sun

Order of Magnitude

Solar System

Order of Magnitude

Interstellar distance

Order of Magnitude

Galaxy

Order of Magnitude

Observable universe

Order of Magnitude

1000 kg 1 Kg

Order of Magnitude

1000 kg 1 Kg

Order of Magnitude

Order of Magnitude

Filling of space by the matter is essentially incomplete, at

both tiny (atom) and big (cosmos) scales

(essentially void around us)

Speed of light

Speed of light

Speed of light in vacuum is a phyical constant :

Speed of light

Speed of light in vacuum is a phyical constant :

c = 3.10^8 m/s = 300 000 000 m/s

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

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

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 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

Speed of light (speed of propagation) depends

only on the medium

A.Einstein 1879 - 1955

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

Speed of light (speed of propagation) depends

only on the medium

speed(vacuum) = speed(air) = c = 3.10^8 m/s

speed(water) < c

A.Einstein 1879 - 1955

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

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

A.Einstein 1879 - 1955

Speed of light

Speed of light

Galilée, Romer, Cassini, Newton, Michelson..

Speed of light

Galilée, Romer, Cassini, Newton, Michelson..

using astronomy

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

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

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

v = c (m/s)

m

s

Speed of light

Speed of light

d = 1m

Speed of light

d = 1m

Speed of light

d = 1m

s m

m/s

Speed of light

d = 1m

s m

m/s

Speed of light

d = 1m

d = 150 000 000 Km

s m

m/s

Speed of light

d = 1m

d = 150 000 000 Km

s m

m/s

s km

km/s

Speed of light

d = 1m

d = 150 000 000 Km

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’)

s m

m/s

s km

km/s

Light-year

Light-year

A light-year is the distance travelled by the

light in vacuum during one year

Light-year

A light-year is the distance travelled by the

light in vacuum during one year

Light-year

A light-year is the distance travelled by the

light in vacuum during one year

m

m/s s

Light-year

A light-year is the distance travelled by the

light in vacuum during one year

m

m/s s

1 year converted in seconds

Light-year

A light-year is the distance travelled by the

light in vacuum during one year

m

m/s s

1 year converted in seconds

1 ly

roughly

Light-year

A light-year is the distance travelled by the

light in vacuum during one year

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

m

m/s s

1 year converted in seconds

1 ly

roughly

Light-year

Light-year

I see dinosaurs

How far are we

from this planet?

Light-year

I see dinosaurs

How far are we

from this planet? Extinction of the dinosaurs :

65 millions years ago

Light-year

I see dinosaurs

How far are we

from this planet? Extinction of the dinosaurs :

65 millions years ago

The aliens are at least

65 000 000 light-years away

from us

(6.5 * 10^22 meters)

Light-year

I see dinosaurs

How far are we

from this planet? Extinction of the dinosaurs :

65 millions years ago

The aliens are at least

65 000 000 light-years away

from us

(6.5 * 10^22 meters)

Watch far = Watch in the past

Light-year

Questions ?

Homework