An atmosphere is a layer of gas that surrounds a planet.

The Earth's atmosphere is divided by scientists into  5  theoretical layers:

• The Troposphere contains   80% of the 5 trillion tons of air!  In direct contact with and heated by the ground, this layer of air is where the important thermal exchanges responsible for meteorological  phenomena take place.
• In the Stratosphere, the temperature gets higher as altitude increases.  This temperature inversion acts as a limit for clouds. It is here that we fiind the Ozone Layer that filters out a large part of the ultraviolet radiation coming from the Sun.
• In the Mesosphere, the temperature once again begins to drop.
• Those rare particles still present in the Thermosphere interact with solar radiation.  In absorbing this energy, they increase in temperature and ionize. This is the ionosphere. This part of the Thermosphere has important electromagnetic properties.  The International Space Station (ISS) is in orbit in the thermosphere, beyond the ionosphere.
• Partcles are so rare in the Exosphere that the probability of collisions among them is negligible. Some even escape the gravitational attraction of the Earth. Although the boundary is not clearly defined, the exosphere marks the beinning of outer space.  The majority of satellites are   orbiting in the exosphere, at altitudes between 800 km and 36,000 km.

Relative orbits for the planets of the solar system are shown. Their proportions are respected (except for the Sun) but not the scale ratio ! Pluto's orbit is elliptical and out of the ecliptic plane.

Once launched, the only forces governing the motion of a satellite are the force of gravity (red vector) and centrifugal force (not shown). The satellite’s speed is shown by a blue vector.  You can change the speed in real time or start an automatically synchronized sequence.

Satellites will orbit in paths which are ellipses.  Circular motion, as in a geostationary orbit, is achieved under very precise conditions.

Click and drag on  the screen to set the position and the initial velocity of the satellite.
Newton was the first to achieve the study of the dynamics of objects in space that we call now celestial mechanics. This animation allows one to use a single theory to explain short distance trajectories and orbital motion.

We highlight here the distinction between weight and mass on the moon. We also show the proportionality between them.

Animated version of the famous Newton's drawing dealing with gravitation and the free fall of a body. Free fall and the launching of an object into orbit are both governed by the same theory of gravitation.
The plus and minus buttons enable you to observe different cases, from free fall (initial velocity zero) to escape velocity (11.3 km/s starting from  the ground.)
Frictional effects are ignored. Only the force of gravity is acting.

Ariane 5 launching process.  Data of important features of the launch are proposed.

The animation is not to scale.