The Krenim scientist Annorax used the energy beam of his weapon ship to initiate temporal incursions. (VOY: "Year of Hell") The level of alteration to the timeline after incursions was measured by 29th century Starfleet operatives in levels of incursion factors. For example, an incursion factor of 0.0036 was considered only a minor change to the timeline. (VOY: "Relativity") The Krenim also probed the continuum after an incursion and calculated the level of temporal restoration in comparison to the original timeline in percentages. (VOY: "Year of Hell")