Pr0t3ct!on#cyber_security@12*12.2011+ copy and paste that -jjong
because you touch it.
Your joints are releasing the synovial fluid and makes a cracking noise.
Well actully, when you crack your back, its not like a bone or joint cracking. Its sort-of "bubbles" in your back from spinal fluids.
Almost immediately. If you paint each nail and watch for a few seconds you can actually see it crack.