The part that is perpendicular to the orbit changes the path of the orbit but not the speed. In a circular orbit, gravity always pulls perpendicular to the path so it can't do any work and can't change the kinetic energy or speed. In an elliptical orbit, there is a component of gravity that is along the path. This component can change the speed and can do work. Ch 10 Review Questions 1.
Atoms are as old as the universe.
The solar system would have taken some time to form, so atoms would be older. Atoms are much smaller than the wavelength of visible light. When atoms or molecules hit the dust particles or grains of soot, this is a collision and gives an impulse to the particles. This force then causes the particles to accelerate and move. We see the resulting movement, or change in movement.