Makes your world more reactive.

Main Features

Finite fluid physics (Flowing Fluids by Traben)
Reworked fire (Burnt Basic by pxlbnk)
Weathering and living flora (Immersive Weathering by Ordana)
Local weather with amazing clouds (Simple Clouds by nonamecrackers2)
Explosions throw blocks (Realistic Explosion Physics by xBigEllx)
Structural and falling block physics (Simple Block Physics by Ferrin-Ember)
Realistic audio (Sound Physics Remastered by henkelmax)
True darkness with sync to moon phase (True Darkness by dylanjkl)
Activity in unloaded chunks (Unloaded Activity by InZan17)
Huge render distance (Distant Horizons by jeseibel)
Paths from walking (Desire Paths by Insane96)
Nights will be simulated (Steve's Realistic Sleep by Steveplays)

Why add this?

I see Minecraft as a static game. Nothing happens without your intervention. This isn't bad, but sometimes I want to feel as if I am a part of the world and not the other way around. These mods make the world react and retaliate to your actions. If you aren't careful while mining you might cause a cave-in, and while you are being crushed by blocks your crops will still grow. You might notice some ore on the ceiling of the cave, but what you didn't notice was the dripping water. Oops... now you're stuck drowning in a pitch black cave you accidentally flooded. Meanwhile over at your base, your puppy grew up. Everything you do has a reaction, borderline retaliation, from the world.

Highlights

The amazing mod Simple Clouds by nonamecrackers2 adds local weather. This has the cool side effect of making scenarios where you can hear a thunderstorm rolling in.

The combination of Simple Block Physics, Flowing Fluids and True Darkness makes cave exploration terrifying. The risk of causing a cave-in plus flood leaving you in complete darkness adds a nice thrill to cave exploration.

Building is way more of a challenge. You actually have to think about structural integrity and the order you build things. Can't have a roof without supporting walls.

Notes

Shaders don't work with this modpack.
I recommend adding some ambience and rain improving mods.
When starting a server make sure to disable collapse in the physics mod config and remove the True Darkness mod from the server