What If the Earth Had Two Moons?: And Nine Other Thought-Provoking Speculations on the Solar System

What If the Earth Had Two Moons?: And Nine Other Thought-Provoking Speculations on the Solar System

Neil F. Comins

Language: English

Pages: 304

ISBN: 0312598920

Format: PDF / Kindle (mobi) / ePub

“What if?” questions stimulate people to think in new ways, to refresh old ideas, and to make new discoveries. In What If the Earth Had Two Moons, Neil Comins leads us on a fascinating ten-world journey as we explore what our planet would be like under alternative astronomical conditions. In each case, the Earth would be different, often in surprising ways.

The title chapter, for example, gives us a second moon orbiting closer to Earth than the one we have now. The night sky is a lot brighter, but that won’t last forever. Eventually the moons collide, with one extra-massive moon emerging after a period during which Earth sports a Saturn-like ring.

This and nine and other speculative essays provide us with insights into the Earth as it exists today, while shedding new light on the burgeoning search for life on planets orbiting other stars. 

Appealing to adult and young adult readers alike, this book follows on the author’s previous bestseller, What If the Moon Didn’t Exist?, with completely new scenarios backed by the latest astronomical research.

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What If the Earth Had Two Moons?: And Nine Other Thought-Provoking Speculations on the Solar System

Breve historia de la astronomía











Like your help deciding who is correct.” The children looked at each other and Laurence stuck his tongue out at his sister. She kicked him, a move barely visible behind the folds of her long dress. “Laurence will speak first, as his ideas are more straightforward.” Laurence waited while his father put a platform behind the lectern. Then the boy mounted it and looked out at the audience. “We all know,” he began, in a high-pitched, child’s voice that caused many members of the audience.

Clearly the concept of a shoreline will be profoundly different than what we think of today. Here in Maine, tides are often ten feet high; tides on Anillo with Noom that close would run two miles high. Returning to the question of whether Noom spirals all the way in and collides with Anillo, we need to revisit the two key distances from a planet related to where moons can exist. Recall from Chapter 2 that synchronous orbit is the distance of the moon’s orbit at which the planet rotates (spins).

Electric currents similar to those created by batteries to run electronic equipment, among other things. In 1819, Danish physicist Hans Christian Orsted discovered that electric currents cause the deflection of compass needles. He correctly proposed that as it flowed, the current was generating a magnetic field, which in turn caused the deflection. The currents flowing in Futura’s (and Earth’s) outer crust also create magnetic fields. When convection in the core is combined with the planet’s.

Companion countered. “I have done a calculation as to how long it would shine under those circumstances. About six thousand years.” He smiled, knowing the irony that this number always generated. “Maybe our planet, Zweisonne, and its star were created six thousand years ago after all.” He waited, but before the young man could say anything, a middle-aged man approached. Hans recognized Ed Saltwater at once. “I was very intrigued by your theory that the Sun is actually two stars,” Hans said.

One is called Mizar B. They have quite elliptical orbits around their common center of mass and take about 5,000 years to make one orbit. In 1889, Edward Charles Pickering examined the spectrum of light emitted by Mizar A and discovered that all the colors were systematically alternating between being Doppler-shifted toward short wavelengths (blue-shifted, meaning that the star was moving toward us) and being Doppler-shifted toward longer wavelengths (red-shifted, meaning that the star was.

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