Reading：Three ways to avoid space debris from colliding with spaceships. 1. Tracking technology; 2. Spaceship shield; 3. Laser broom. Listening: The professor is against three methods: 1. Tracking technology will only track bigger debris. Small debris travel fast and collision caused them are fatal. E.g. a chip of paint from one spaceship collided with another spaceship. The small debris smashed on another spaceship’s wall and created a hole. 2. Shield method is not good too since it adds extra weight to the spaceship. We need to develop more powerful rocket to deliver the spaceship to the space. The challenge is harder for us. 3. Finally, the professor doesn’t like laser broom idea. A laser broom with such power could be used a military weapon in space, which violates the international agreement.