Gravitational fields

Coherence of galaxies

This is a photograph of the galaxy M100, a spiral galaxy like ours. Other galaxies are spherical or elliptical.

All galaxies have in common the fact that it is the force of gravity that keeps the thousands of millions of suns they are made up of travelling around their common centre of mass.

Why are there galaxies with different shapes? We now know that collisions between galaxies modify their shape.

However, their initial conditions are also very important in the formation of their final shape. Click on to see the original cause of these differences.

	Freely falling bodies
	Two theories of the universe
	Kepler's laws
	Conclusions

	Newton's law
	The superposition of forces
	Angular momentum and central force
	Conclusions

	Explanation of the tides
	The movement of artificial satellites
	Coherence of galaxies
	Conclusions

	The concept of field intensity
	Variations according to position
	Conclusions

	Gravitational potential energy
	Equipotential surfaces and lines of force
	Conclusions