Yes, planetary positions **do change** over time due to orbital dynamics, gravitational interactions, and even cosmic collisions. Here’s how:

### 1. **Orbital Migration**

- Planets don’t stay in fixed orbits forever. Gravitational interactions with other bodies (like gas giants or passing stars) can cause **orbital migration**.

- Example: Jupiter likely moved inward, then outward in the early solar system, scattering smaller planets and asteroids.

### 2. **Time Scales Vary by Planet**

- Inner planets (Mercury, Venus, Earth, Mars) orbit the Sun **quickly** (months to years).

- Outer planets (Jupiter, Saturn, etc.) take **decades to centuries** for noticeable shifts.

- Over **millions of years**, orbits can change significantly due to gravitational perturbations.

### 3. **Mergers & Collisions**

- **Theia Impact (~4.5 billion years ago)**: A Mars-sized protoplanet (Theia) collided with early Earth, ejecting debris that formed the Moon.

- **Giant Impact Hypothesis**: Such collisions were common in the chaotic early solar system, reshaping planets.

### 4. **Future Planetary Motion**

- **Mercury’s Unstable Orbit**: Simulations suggest it might collide with Venus or the Sun in billions of years.

- **Mars vs. Phobos**: Mars’ moon Phobos may break apart or crash into Mars in ~50 million years.

- **Andromeda-Galaxy Collision (4-5 billion years)**: While stars/planets likely won’t collide, orbits could be disrupted.

### Could Planets Merge or Collide Again?

- **Unlikely in the current stable solar system**, but over **trillions of years**, gravitational chaos or passing stars could destabilize orbits.