Silent Realm

The Silent Realm is a location in Skyward Sword. It can be accessed by thrusting Link's sword on the blue, glowing ground. When Link thrusts his sword, he will be taken into an alternate dimension of the current world he is in. The Silent Realm is similar to the normal world, except it has a blue atmosphere and seems to be similar to the Twilight sections from Twilight Princess. As such, knowledge of the normal area will help Link navigate the Silent Realm version of it.

Link must enter the Silent Realm and complete the trial to claim proof of his spiritual growth.

Overview
Since Link accesses the Silent Realm with the use of his sword, he will be unarmed while he explores the alternate dimension. To leave the Silent Realm, he will have to collect all 15 Sacred Tears. As he fills his Spirit Vessel with the tears, Link's spirit will grow. However, Guardians, powerful enemies that inhabit the Silent Realm, will be patrolling the area. Guardians will come after Link, and one single hit from them will defeat the young hero. Link must use the tear-shaped items in the alternate reality to stun the creatures for a limited time while he continues to look for the items. A flower on the side of the screen acts as a timer, with its petals disappearing to indicate how long the Guardian will be stunned. If Link is spotted by a Watcher's light, the sentry will emit a loud sound that will awaken the Guardians, canceling the effects of the tears.

To help him find the remaining Sacred Tears, Link can pick up a Light Seed to reveal their locations for a short time. After you gain all 15 Sacred Tears, the time you have to get back to the entrance is unlimited, unless you get spotted by a Watcher, then the Guardians will be after you

Theory
The Silent Realm is sometimes compared with the Sacred Realm, due to the fact that in both realms the Triforce is hidden. The difference between both of them is that The Silent Realm is mentioned as a place where the hero will be tested by the goddesses, while the Sacred Realm is refered as a place where the Triforce lies. This clearly contradicts the theory, but at the same time the statement supports it, because when Link enters the Silent Realm, the region is suddenly transformed into a quiet place, similar to Ganon's Dark World. Something that also contradicts the theory are the Guardians. Those Guardians are sent by the Goddesses to prove the hero and obviously, they have been never mentioned during the events of the Imprisoning War. But, when Link reaches the Sky Keep and obtain any part of the Triforce, he is sent into a dimension (and a room) where that part of the Triforce is hidden. That room is similar to the Silent Realm Link visited before, but this time, there are no Guardians at all, because the hero already proved himself with the goddesses. This highly supports the theory, because maybe Link's Sacred Realm is reflected as a quiet place due to his intentions to use the Triforce are not evil instead of Ganon's.

Something that also supports the theory, is the fact that when Link is sent to the Silent Realm, he can't use any of his weapons. At the ending of Ocarina of Time, Ganondorf is sealed in the Sacred Realm, and also he's not wearing any weapons.

Also, the timeline placement of Skyward Sword is before the events of Ocarina of Time. This also is important, because the Imprisoning War hasn't happened yet or, it happens sometime between these two games and the Sacred Realm has not been created either.