Yes, the length of an orbit can change over time due to various factors. Two common reasons for changes in the length of an orbit are gravitational interactions with other objects and the effects of tidal forces.
Gravitational interactions: The gravitational forces exerted by other celestial bodies can influence the shape and duration of an orbit. For example, if a planet or moon passes close to another massive object, such as a planet or a star, the gravitational attraction can cause the orbit to become more elliptical or change its orientation. This phenomenon, known as perturbation, can lead to variations in the length of the orbit over time.
Tidal forces: Tidal forces occur when the gravitational forces from one celestial body cause deformations in another body. These forces can induce changes in the shape of the orbit over time. For example, the Moon's gravitational pull creates tidal forces on Earth, causing ocean tides. These tidal forces can also induce friction, dissipating energy and leading to a gradual transfer of angular momentum between the Earth and the Moon. As a result, the Moon is slowly moving away from Earth, and the length of its orbit is increasing over time.
It's worth noting that these changes in orbit length generally occur over long timescales and may not be noticeable within a human lifespan. However, over millions or billions of years, the cumulative effects of gravitational interactions and tidal forces can lead to significant changes in the length and shape of orbits.