Neil deGrasse Tyson Explains "What Goes Up, Must Come Down"
StarTalk・11 minutes read
The concept of "what goes up must come down" is rooted in gravity's impact on objects thrown upwards, with escape velocity being key for space travel to break free from Earth's gravitational pull and reach other celestial bodies. Achieving escape velocity varies based on the celestial body, such as Earth needing 7 miles per second and black holes requiring the speed of light, highlighting the importance of understanding gravity's impact on objects in motion.
Insights
- Gravity plays a crucial role in determining the trajectory of objects thrown upwards, causing them to slow down and fall back symmetrically due to Earth's gravitational pull.
- Achieving escape velocity is essential for space travel, enabling objects to break free from Earth's gravity and reach other celestial bodies, with different bodies having varying escape velocities, such as black holes requiring speeds equal to that of light.
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Recent questions
What is the concept of escape velocity?
The concept of escape velocity refers to the speed required for an object to break free from the gravitational pull of a celestial body and reach infinity without being pulled back.
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Summary
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"Escape Velocity: Breaking Free from Gravity"
- The saying "what goes up must come down" originates from a pre-space era concept, where gravity acts on objects tossed upwards.
- Gravity subtracts from the initial speed of an object thrown upwards, causing it to slow down until it stops and falls back down symmetrically.
- The speed at which an object is thrown determines how high it goes before gravity brings it back down.
- Earth's escape velocity is 7 miles per second, the speed required for an object to reach infinity before gravity stops its motion.
- Escape velocity varies based on the gravitational pull of different celestial bodies, with black holes having an escape velocity equal to the speed of light.
- Achieving escape velocity is crucial for space travel, as it allows objects to break free from Earth's gravitational pull and reach other celestial bodies.
- To reach the moon, astronauts must achieve escape velocity through a translunar injection, using the moon's gravity to guide them.
- Neglecting air resistance, firing a high-powered rifle straight up would result in the bullet falling back down at the same speed it left, emphasizing the importance of not firing guns in the air.
