My friend and I were trying to create a rollercoaster, I start putting down a bunch of minecarts on one spot and thought they would equally spread out. Instead, they all crammed together in the same spot, producing a dark shadow underneath. I thought it would be funny to see how far they all go and decided to break the tracks and blocks underneath. They don't seem to be moving. I lightly walk into the minecarts pushing them slightly and... they don't stop moving. These minecarts went on for hundreds of blocks, possibly even thousands all the while these thirty to forty minecarts were together. Some eventually separated and stopped but there would always be at least one that wouldn't stop. A sort of perpetual motion.

What I expected to happen was...:
...the minecarts would all separate once pushed and wouldn't keep going

What actually happened was...:
...the minecarts stuck together and kept going once pushed.

Steps to Reproduce:
1. Create a 3x3 square of blocks (Redstone blocks are easiest to recreate with.)
2. Place normal rails on corners and connect them with powered rails. (Power if needed.)
3. Repeatedly place minecarts on the side of the rail (30 - 50) until a dark shadow appears underneath the rails.

4. Destroy all blocks and rails so that the minecarts are resting on the flat floor as minecarts will stop if faced with an object unless it is water.

5. Walk into minecarts and push them into a direction, they will not stop.

I provided pictures down below 

Here is a video of it happening:

https://www.youtube.com/watch?v=ynj1W4OpI-8&feature=youtu.be