Final answer:
Grace's plan to become an astronaut should focus on obtaining an aerospace engineering degree and a doctoral degree in physics, alongside gaining relevant experience and meeting NASA's rigorous selection criteria. General relativity predicts time dilation in strong gravitational fields, which could lead to an astronaut aging slower than people on Earth. Long space voyages near light-speed involve challenges such as significant time dilation, isolation, and potentially irreversible decisions affecting the astronaut's life and relationships with people on Earth.
Step-by-step explanation:
Grace's goal of becoming an astronaut by age 30 entails a well-planned educational and career path. While aspirations are important, achieving such a high-caliber profession requires concrete steps. An appropriate plan for Grace would involve completing an undergraduate degree in aerospace engineering and a doctoral degree in physics. These credentials are essential for NASA or any other space agency's astronaut selection. Additionally, Grace will need to gain experience in her field, which could include working on relevant projects, research, or obtaining a pilot's license, coupled with maintaining excellent physical condition and passing rigorous NASA selection criteria.
General relativity indicates that in a strong gravitational field, such as near a black hole, time progresses slower relative to a distant observer. This concept has gripping implications for astronauts venturing close to such extreme environments. For example, if an astronaut travels to a black hole and spends significant time in orbit around it, upon returning to Earth, she may find that much more time has passed here than she experienced in space. This is a result of the time dilation effect predicted by general relativity.
Challenges associated with long-duration spaceflights, especially at speeds close to the speed of light, include significant time dilation effects. An astronaut might age only slightly on a journey to a star 20 or 30 light years away, while many decades could pass on Earth. The psychological and physical effects of such a journey, potential isolation, and the inability to return within their lifetime are severe considerations for anyone undertaking these missions.