Item #: SCP-XXXX

Object Class: Euclid

Special Containment Procedures: The cave system containing the accessible portion of SCP-XXXX is to be closed off from the public. Area-XXXX is situated 0.5km from the main mouth of the cave.

Prolonged use of SCP-XXXX represents a great risk to Foundation secrecy. As such, any testing of SCP-XXXX requires majority approval from the O5 council and must be conducted over the span of less than 30 seconds.

Due to widespread knowledge of SCP-XXXX-1, any other containment is based on maintaining public consensus of it as a non-anomalous component of reality.


SCP-XXXX is an elaborate and massive mechanical device located below a cave system in northern Scotland, UK. The full size of SCP-XXXX is currently unknown, though it has an estimated cross-sectional area of 17 km2 and extends vertically for at least 25 km below sea level. The accessible portion of SCP-XXXX has a surface area of 24m2, and is located approximately 700m from the mouth of the cave system.

SCP-XXXX-1 is the speed of light in a vacuum, exactly 299,792,458 m/s. Within the prime reality, no particle with mass can travel at any speed equal to or greater than SCP-XXXX-1, and no massless particle can travel at any speed not equal to SCP-XXXX-1.

The primary function of SCP-XXXX is maintenance and modulation of SCP-XXXX-1. Via a command terminal situated on the exposed face of SCP-XXXX, a user is able to modify the value of SCP-XXXX-1, with a minimum possible value of 1m/s, and no observed maximum value.

It is unknown what would occur if SCP-XXXX were to be deactivated, destroyed, or otherwise rendered inoperable, though a number of theories have been proposed, the most likely of which being:

  • Modification of SCP-XXXX-1 to an infinite value, resulting in massless particles existing in all locations at once due to having an infinite speed.
  • Modification of SCP-XXXX-1 to zero, resulting in motion of massless particles being rendered impossible, and a possible ZK-Class reality failure scenario as mass-having particles are both incapable of having negative speed and of having a speed of zero or above.
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