Generate a series of (instruction, response) pairs that are similar in context and structure to the example provided below. Each pair should consist of a concise instruction followed by an appropriate, detailed response. The instruction should pose a clear task or question, while the response should provide a comprehensive answer or solution that could be understood by someone with a basic understanding of the subject.

Example pair: 
Instruction: I need a summary for second-grade students. Keep it under 5 sentences and keep measurements in the imperial system. 

A penguin typically has a black back and a white belly. Different types range in height from about 14–45 inches (36–114 centimeters). The largest type is the emperor penguin, which weighs about 80 pounds (36 kilograms).

Penguins are excellent swimmers and divers. They can swim faster than 25 miles (40 kilometers) per hour. Penguins use their short, paddlelike wings as flippers for swimming. Their feet are webbed, and their bodies are shaped like torpedoes. Penguins have short legs, but they can run fairly quickly. To travel over ice and snow, a penguin may slide on its belly.

A penguin is covered nearly all over with short feathers. The feathers keep water out and trap warm air against the skin. A thick layer of fat also protects this bird from the cold. 
Response: Penguins have black backs, white bellies, and short legs. They range from 14-45 inches, and emperor penguins are the largest at 80 pounds. Their paddle-like wings, webbed feet, and torpedo-like bodies make them great swimmers and divers who can swim over 25 miles per hour. Penguins have short feathers and a layer of fat that helps keep them warm. 

Your task is to generate more pairs that maintain this level of clarity and detail. The topic is Summarization. Write a long text of instruction by yourself, then summarize the given instruction in a response. Ensure that the responses are informative and accurate, suitable for an educational context. 

Store the generated pairs in valid JSON format, with each pair as an object within an array. Each object should have two key-value pairs: "instruction" and "response". For instance: 

{"contents": [{"instruction": "text", "response": "text"}, {"instruction": "text", "response": "text"}, ...]} 

Remember to maintain consistency in the format and ensure the generated pairs are diverse and cover a broad range of subjects. You must return the response in the asked format and you must not add any additional text in your response.

Summarize the basic concept of gravity for a second-grade class.
user
Gravity is a force that pulls things towards the ground. It's why we don't float away and why things fall when you drop them. Everything with mass has gravity, but the Earth’s gravity is the strongest for us.
assistant