Cracking your knuckles does not actually hurt your bones or cause arthritis. The sound you hear is just gas bubbles bursting.
Cracking your knuckles (or any of your joints) can have therapeutic benefits. When you crack one of your joints you are pulling the bones that are connected at the joint apart from each other. This process stimulates your tendons, relaxes your muscles, and loosens your joints. Chiropractors do this for spinal joints when your back is sore and stiff, but you can do this on your own for your knuckles, toes, knees, neck, etc.
Unfortunately, there can be too much of a good thing. Cracking your knuckles will never lead to arthritis (despite what your mom keeps telling you), but scientists have discovered that it can cause tissue damage in the affected joints. Knuckle-cracking pulls your finger bones apart which stretches your ligaments. Too much stretching of your ligaments will cause damage to your fingers akin to the arm injuries sustained by a baseball pitcher who throws too many pitches. In addition to making your hand really sore, this ligament damage can also result in reduced grip strength.
How does this work? Your joints, the places in your body where you can bend, are where your bones intersect and are held together by ligaments. These joints are surrounded by a liquid called synovial fluid. When you stretch your ligaments by pulling the bones apart to crack your knuckles a gas in the synovial fluid escapes and turns into a bubble. This process is called cavitation. Cavitation ends when the bubble eventually bursts, producing that popping sound we know and love. After that, your joints won't be able to crack for another 25-30 minutes while the gas gets reabsorbed into the synovial fluid.
Scientists lit a cave of natural gas in 1971 expecting it to burn out in a few days, but it still burns to this day!
Near Darvaz, Uzbekistan, geologists were drilling for gas. They ended up drilling into a huge natural cavern that went super deep. The cavern was filled with gas, so none of them dared to explore the cavern and how deep it really went. They decided to light the cavern on fire, so that no poisonous gases would escape. This all went down in 1971, and they expected the fire to burn for a few days or so. Fast forward to today and the cavern is still ablaze. It hasn’t stopped burning in over 35 years. It’s now known as “The Door to Hell”.
Nobody has been able to calculate just how many tons of natural gas has burned throughout the years at the cavern sight, but it is a major loss of a natural resource and a total waste. They definitely should have done a little extra math or exploring before lighting a cavern on fire wasting millions of dollars of natural resources.
So, the REM Dreamer is a European sleeping mask covering the eyes. It creates light cues like camera flashes, sunlight, car headlights, and other types of stimulants. It is the dreamer’s job to recognize the flashing lights as a dream sign and become consciously lucid by a pre-determined reality check. The sound and light cues are sequenced into the dream so that the dreamer becomes lucid.
Sleep experiments show that during REM sleep, dreamers move their eyes in the same direction as they do in their dreams. In fact, it was Dr Stephen LaBerge who famously did this to scientifically prove lucid dreaming in the 1980s. When lucid, he gave pre-determined eye signals to researchers in the outside world. The point of the experiment and the mask is to help the dreamer remember their dreams better and shorten the time needed to learn lucid dreaming. It’s sold for 147 Euros.