What is resonance? [in relation to moons]?

Question

What does it mean when astonomers say that two moons share resonance. . .

for example, 3:4 resonance between Hyperion and Titan. . .

Any help would be greatly appreciated, as I am working on a project and don't understand this term I've stumbled across!

Answer 1

A 3:4 resonance means one object completes 3 orbits in the same time that the other one completes 4 orbits. This means every 3 orbits for the slower one and every 4 orbits for the faster one causes them to pass each other and give each other a little gravitational nudge at that time. In physics, when any moving system gets a periodic nudge at the right time, it is called resonance. It can cause otherwise small motions to become larger. It is like swinging. If you are pushing a person in a swing, you can time your pushes at just the right moment to make them swing higher and higher, or if you just push them at random times, you do not make them swing higher. Timing your pushes just right is resonance.

Answer 2

From what I read, it looks like its the speed in which a moon circles its host planet.

"Europa is locked in a tidal resonance with its neighboring satellites, volcanic Io on the inside and large Ganymede on the outside. Like each of the Galilean moons, Europa is spin-locked to Jupiter, rotating about its pole with a period identical to its orbital period of 3.6 Earth days. Europa is in a 1:2:4 resonance with Ganymede and Io for every two times that Europa orbits Jupiter, Ganymede orbits once, and Io orbits four times. This resonance keeps the satellites from perfect circular orbits, causing a forced eccentricity that varies their distances from Jupiter. Jupiters strong gravity raises a bulge on the portion of the surface facing towards the planet, but since the distance between the moons and Jupiter varies, the height of the tidal bulge also varies throughout the satellites orbit. The variation in tidal amplitude results in tidal flexing as the bulge goes up and down, producing an internal dissipation of energy called tidal heating. "

Could be wrong, but that's what it sounds like.

Answer 3

Simply put:
An orbit is a dynamic balance between the gravity of the primary and the inertia of the orbiter.
In the case you state each moon receives a tug from the other every time they pass.
One at third points in its orbit, one at quarter points.
Such tugs will tend to cancel out.
If the tugs were not canceled the orbits would loose their almost circular shape and the system would decay.
The same is true of the major planets in their orbits about the sun.

Answer 4

At certain ratio's resonance can case a body to remain "stationary" relative to another body.