Question

if a scientist wants to predict when a comet or asteroid will collide with a planet, what must they understand? chemical reactions weather patterns magnetic fields gravitational attraction between all bodies

Explanation:

Step1: Understand the problem

The problem is about what a scientist must understand to predict when a comet or asteroid will collide with a planet.

Step2: Analyze each option

• Chemical reactions: These are related to the transformation of substances at a molecular level and not directly relevant to predicting celestial collisions.
• Weather patterns: Weather patterns are about the state of the atmosphere on a planet and have no bearing on predicting collisions between celestial bodies (comets/asteroids and planets).
• Magnetic fields: Magnetic fields are related to the magnetic properties of objects and do not play a direct role in predicting such collisions.
• Gravitational attraction between all bodies: According to Newton's law of universal gravitation, every object in the universe attracts every other object with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers. Celestial bodies (comets, asteroids, planets) move under the influence of gravitational forces. To predict a collision, one must understand how the gravitational forces between the comet/asteroid and the planet (and other relevant celestial bodies) affect their orbits and paths.

Answer:

Gravitational attraction between all bodies.