Final answer:
The state of retirement involving engaging in new activities such as travel is known as Exploration, and it aligns with the Activity Theory of Aging which posits that activity and social involvement lead to a fulfilling retirement.
Step-by-step explanation:
The state of retirement that involves retirees engaging in a variety of activities such as travel, which was less possible while they were working full time, is known as Exploration. This phase pertains to the period in a retiree's life when they pursue a wider range of goals and activities that they did not have the time for during their working years. The Activity Theory of Aging suggests that maintaining a high level of activity and social involvement is crucial for happiness in later life. This theory implies that continued engagement in activities, whether through traveling or pursuing hobbies, leads to a more fulfilling retirement, and contrasts with the Disengagement Theory which posits a natural tendency for older adults to withdraw from society.