Examples include massage, talk therapy, and hypnosis. Flotation requires a soundproof and lightproof fiberglass enclosed float capsule (sometimes referred to as float tank or spa – approximately 8 feet long by 4 feet wide by 4 feet high) filled with heated water (to skin temperature of 94-95 degrees F) and a very high concentration (800 lbs.) of Epsom Salts. The resultant high density allows ones body to float naturally and spontaneously without effort. Even the head floats. The center of buoyancy and the center of gravity of the head are in about the same place so you can tilt your head back comfortably without fear of sinking. Due to the high salt levels in the water, the flotation tank creates a zero gravity environment. Unless you are an astronaut the flotation tank is the only situation you will encounter where your body is free from gravity. NASA employs flotation to stimulate weightlessness. Zero gravity allows you to relax every single muscle, your neck, arms, back, and even ears. The tank enables you to find those areas you are holding tense so you can let go. Finding where gravity is and in which direction, then computing how you can move and not fall over, takes about 90% of your brains activity on a daily basis. When you start to float you are free from all the gravity computations and the physical world, which leaves the brain free to attend to other matters. The tank creates a state of sensory relaxation as the mind and body are shielded from all the external stimulation. The brains normal workload is reduced by up to 90%. In this situation, the body conserves energy and has a chance to heal and rejuvenate itself. Floating in darkness allows areas of the brain which are always in use when awake to be liberated from their work. Tests have shown that there is a drop in electrical activity of the brain and you begin to generate theta brain waves, which are associated with deep relaxation. The darkness during floating also induces a balance between the left and right brain. There is a shift from the normally dormant left side of the brain (logical, analytical, rational) to the right side (intuition, mental clarity and creativity). For the first time both sides of the brain are in harmony and the balance creates allows you to use huge amounts of previously unavailable brainpower. One of the major sources of stimulation in humans is the temperature gradient change on the surface of the body. Temperature inside the float tank is isothermal over the surface of the body so that the nerve endings covering the surface of the skin no longer perceive a separation between the skin and the solution inside the tank. The flotation tank is soundproof. During floating, you may choose to wear earplugs, your ears are below the surface of the solution, which cuts out external sounds. Some people find that gentle music from underwater speakers helps them to relax.