Viewing a single comment thread. View all comments

Enorats t1_j4yzg6z wrote

Reply to comment by Patrick26 in Are Two Tidally Locked Earth in One Solar System Possible? by Thirdy-DOg

That's not necessarily possible though. The Moon is tidally locked to the Earth because its smaller by a large margin. The Earth would eventually tidally lock to the Moon as well, but our Sun will destroy both the Earth and Moon long before that ever happens.

Two similarly sized bodies would take longer to lock to one another than the Moon did to the Earth, but less time than it'd take the Earth to lock to the Moon. I've no idea how long that'd actually take though, or if it'd be within the lifespan of the average star similar to the Sun.

5

Underhill42 t1_j53hdho wrote

Keep in mind the moon is only ~1% the mass of the Earth, it's not doing much.

I would imagine the time to tidal locking decreases at *least* linearly with increasing gravity from the "lock-er" (e.g. twice the force = half the time, maybe less. That's normal for most systems), in which case if the moon were Earth-mass, 100x larger, Earth would lock to it 100x faster, and the 50 billion years until tidal locking (~55 with time served) would be closer to 550 million - almost before liquid water appeared on our surface.

1