People and all other known forms of life inhabit one very old planet. In numerical terms, the best estimate of Earth’s age so far is that it is close to 4.6 billion years old. But what does that mean exactly? If one uses a human lifetime of 75 years as a measure, the time between Earth’s formation and today has taken more than 61 million human lifetimes! Examining the interactive below, one can see that a great deal has happened since 4.6 billion years ago. For the first fifth of Earth’s geologic time, the planet had no life. Since then, ...(100 of 163 words) Access the full article Help support true facts by becoming a member. Subscribe today!