Context: Time appears to have a direction—the past lies behind, fixed and immutable, while the future lies ahead and is not necessarily fixed. Yet for the most part the laws of physics do not specify an arrow of time, and allow any process to proceed both forward and in reverse. This is generally a consequence of time being modeled by a parameter in the system being analyzed, where there is no "proper time": the direction of the arrow of time is sometimes arbitrary. Examples of this include the Second law of thermodynamics, which states that entropy must increase over time (see Entropy); the cosmological arrow of time, which points away from the Big Bang, CPT symmetry, and the radiative arrow of time, caused by light only traveling forwards in time (see light cone). In particle physics, the violation of CP symmetry implies that there should be a small counterbalancing time asymmetry to preserve CPT symmetry as stated above. The standard description of measurement in quantum mechanics is also time asymmetric (see Measurement in quantum mechanics).

Question: What laws do not specify an arrow of time?
Answer: the laws of physics

Question: The direction of the arrow of time is sometimes what?
Answer: arbitrary

Question: Which law states that entropy must increase over time?
Answer: the Second law of thermodynamics,

Question: The violation of what implies that there should be a small counterbalancing time asymmetry?
Answer: CP symmetry

Question: The standard description of measurement in quantum mechanics is what?
Answer: time asymmetric

Question: In what directions do the laws of entropy allow light to go?
Answer: Unanswerable

Question: What does quantum mechanics determine about entropy?
Answer: Unanswerable

Question: What needs to be preserved according to quantum mechanics?
Answer: Unanswerable

Question: Which law says that CPT symmetry must increase over time?
Answer: Unanswerable

Question: In particle physics what should there be to preserve entropy?
Answer: Unanswerable

Question: What laws specify as an arrow of time?
Answer: Unanswerable

Question: The direction of the past is sometimes what?
Answer: Unanswerable

Question: Which law states that entropy must increase in the past?
Answer: Unanswerable

Question: The violation of what implies that there should be a small counterbalancing difection asymmetry?
Answer: Unanswerable

Question: What is the standard description of direction in quantum mechanics?
Answer: Unanswerable