During the new DC Comics Universe series "Flashpoint," in which a time-traveling supervillain alters the past to warp the present, Life's Little Mysteries presents a 10-part series that examines what would happen if a major event in the history of the universe had gone just slightly differently.
Part 7: What if ... Earth were twice as big?
If Earth's diameter were doubled to about 16,000 miles, the planet's mass would increase eight times, and the force of gravity on the planet would be twice as strong.
Life would be: Built and proportioned differently.
If gravity were twice as strong, bodies possessing the same construction and mass as our flora and fauna would weigh twice as much and would collapse. It'd be "timber!" for tall, thick trees such as redwoods. Large, sunward-reaching plants might still develop, but would require stiffer architectures of cellulose fibers or another material altogether.
Animals would have to be thicker-legged to support their weight. As for humans, our appearance would depend on the evolutionary demands placed on our biological forebears in a higher-gravity world, said Neil Comins, a professor of physics at the University of Maine. "If our ancestors had to run fast and fight hard, then we would be burly, but if not, we could be thin and light," Comins told Life's Little Mysteries.
Previously: What would life be like if the moon had never formed?
Next: What would life be like if the sun were half its size?
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Adam Hadhazy is a contributing writer for Live Science and Space.com. He often writes about physics, psychology, animal behavior and story topics in general that explore the blurring line between today's science fiction and tomorrow's science fact. Adam has a Master of Arts degree from the Arthur L. Carter Journalism Institute at New York University and a Bachelor of Arts degree from Boston College. When not squeezing in reruns of Star Trek, Adam likes hurling a Frisbee or dining on spicy food. You can check out more of his work at www.adamhadhazy.com.