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

3.68  ·  Rating details ·  231 ratings  ·  35 reviews

“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.

Hardcover, 304 pages
Published March 30th 2010 by St. Martin's Press (first published 2010)
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Oct 08, 2010 rated it it was ok
Recommends it for: Qualified rec to space-science fans/SF authors looking for world-building ideas
First the "good stuff":

The ideas alone get a minimum three+ stars in my reckoning. I've always liked SF stories that took me to truly weird worlds like Mesklin (Mission of Gravity) or Helliconia (Helliconia: The Classic Epic Trilogy in One Volume) and how the environments shaped the natives and the humans who (sometimes) colonized them. So in this book we get 10 scenarios about what an Earth-Moon system would be like if something were changed:

1. What if the Earth had two moons?
2. What if the Ear
Natalie aka Tannat
2.5 stars.

Parts of it were interesting, but nothing is really gained by reading the introductory vignettes. Unlike others, I won't criticize the renaming of the different scenario planets because of the way the names were subsequently used in the discussion. Thanks to the unknown library patron who pointed out the mistakes in the text which I had glossed over. Actually, some of the information was dated, even for 2010. Perhaps it's a consequence of the chapters having been written separately.

Jul 20, 2013 rated it really liked it
This book, like Comins' earlier What If the Moon Didn't Exist?, contains a series of thought experiments about alternate Earths. This book is essential for science fiction writers and for anyone who's ever wondered what might have been. I especially liked the section 'what if the earth was a moon?' But each one of the book's ten chapters poses some interesting questions. ...more
Dec 09, 2020 rated it liked it
What If Earth Had Two Moons
And Nine Other Thought Provoking Speculations on the Solar System
Author: Neil F. Comins
Publisher: St. Martin’s Press
Publishing Date: 2010
Pgs: 288
Dewey: 525 COM
Disposition: Irving Public Library - South Campus - Irving, TX

“What if?” Science. The title questions and nine other scenarios about what Earth could be and what life, the past and the future would be like “If”.

Ten speculative ess
Sep 07, 2018 rated it it was amazing
Shelves: what-if, y2018, astronomy
We all wonder about the enduring question 'What if?'
In this case, there are in 10 different speculations regarding the the Earth, planetary scientific variations and the background (as known in 2010) for each. In actuality, there are 16 as some possibilities can have multiple scenarios.

Once you're past the introduction which gives origin of this book - which this is actually the author's second book of what if's - you're asked what if the Earth had two moons. The author gives a little fictional
Jul 27, 2010 rated it liked it

I am not happy with this book.

To be sure, the subject -- the question of what an earthlike world would be like if it had formed and evolved in different circumstances than ours, and what life would be like on such worlds -- is fascinating. Comins presents ten such scenarios:

1) What if the Earth had two moons?

2) What if the Earth were a moon?

3) What if our Moon orbited backwards?

4) What if the Earth's crust were thicker?

5) What if the Earth w
Rachel McCollin
Nov 15, 2018 rated it really liked it
Mind boggling. I particularly enjoyed the little stories, a nice touch.
Dan Thompson
Oct 09, 2012 rated it really liked it
This is a collection of ten what-if scenarios for alternate earths in various solar systems. It includes the title scenario of Earth having two moons, how we would have gotten them, their effects on the Earth over time, and ultimately what’s going to happen to them. Other scenarios include the Earth as a moon, the Moon in a retrograde orbit, other planets in Earth’s orbit, Earth’s elsewhere in time, Earth’s elsewhere in the galaxy, and even what will happen to the Earth when the Milky Way and An ...more
Dec 22, 2013 rated it it was ok
Shelves: 2014, science
It takes a bit of work to take such riveting questions and fascinating science and turn it into one of the most boring non-fiction reads I've experienced in a while, but Neil Comins manages to pull it off. My review won't add anything to previous reviews, but merely agree. The fictitious excerpts on these alternate worlds was a corny trick. Feeling the need to rename the alternate earths and other worlds (presumably to remind the reader that this really isn't how earth is) was just annoying. I d ...more
Alex Telander
May 06, 2010 rated it liked it
Neil F. Comins is a professor of physics and astronomy at the University of Maine and has written a number of popular books including: The Hazards of Space Travel: A Tourist’s Guide and What if the Moon Didn’t Exist? Voyages to Earths That Might Have Been. In his new book, What if the Earth Had Two Moons, he gives us nine alternative realities, including what our world would be like if we had two moons. At the beginning of each hypothesis, Comins has a little fun with a short fictional reality e ...more
Apr 30, 2012 rated it liked it
I like the ideas and the guy clearly knows what he's talking about, but it was pretty boring, sadly. For me, he spent way too much time talking about how the planet would come to exist and not enough time exploring or explaining intricacies of what a "present day" would look like. I wasn't a fan of the fiction or renaming either, although I suspect I know what he did the renaming. The names themselves had me kinda eyerolling (Zweisonne? really? Well the inhabitants must be pretty dull if they do ...more
Gaabriel  Becket
Dec 09, 2010 rated it really liked it
I love Neil Comins and recommend this to anyone willing to give it a crack. Reading these essays on how single, but pivotal, changes to our solar system or our planet or our moon would effect the earth and life on it, really sparks and invigorates the imagination. These are great fun to read and to think and imagine with and Comins takes the reader through the ripple effects single differences might make. Two moons, as opposed to one, is just one example: how would it effect gravity and water an ...more
Feb 26, 2011 rated it it was amazing
I don't normally comment much on a book, but this one I loved. I'm normally a very fast reader, but this one did take me 25 days to get through only because I did get a little bogged down with the actual science/math he put into the book. And occasionally his suppositions took a little bit of thought too. However, it would be facinating to find "earths" like this and see how accurate everything he proposes is. I believe I saw that he had a book prior to this starting with the postulation of what ...more
Sally Lopez
Very enjoyable. I would have liked longer sci-fi sections that better introduced the explanatory parts, so I could have made more connections and been more fascinated by the differences each planet has from Earth. That would have made the book significantly longer, though, and maybe Comins wasn't ready to go deep in the story-telling realm. In all, highly recommended. I read Orson Scott Card used this book to plan the world in which his new Pathfinder series is set. ...more
Deanna Necula
Dec 24, 2014 rated it it was ok
Shelves: dropped
I can read dense scientific books with pleasure, but this, despite its layman-friendly premise, is simply too boring. I almost couldn't make it past the introduction. I'm somewhat disappointed, because I have the distinct impression I'm missing out on some interesting nuggets to come, but I believe my time will be better spent with a more interesting, and better-written book. Don't even get me started on the odd and far-too-long fictional vignettes opening each chapter. Ugh. ...more
Blair Conrad
Aug 07, 2010 rated it really liked it
Shelves: library, nonfiction
Interesting popular science book about how Earth-like planets might've developed under different astronomical circumstances. Not too deep, and each article is prefaced by (a pretty superfluous) story set on the planet to be discussed. Fairly fun, with the best bit being the one about Earth being a moon. ...more
Great science writing. As the title indicates, the author starts each of ten scenarios by imagining a solar system differing from our own in a different way - Earth with two Moons, Earth as a moon of a gas giant, etc.; then he explores the conditions that would result on Earth's surface and how - or whether - human civilization might form as a result. Good for adults or bright kids. ...more
Jul 01, 2012 rated it it was ok
This book was ok, but it got a little dry and at times the explanations could go from very elementary to more complex. However, I did like imagining what these various worlds would be like. If I could pick one to visit, I'd choose Mynoa the Earth-moon, orbiting the Neptune-like Tyran. Definitely not one of the better books I've read, it nevertheless threw out a few interesting concepts. ...more
Sep 05, 2015 rated it really liked it
A nice way to learn astronomy concepts through a series of thought experiments that could easily expand into works of science fiction (though some scenarios were more interesting than others, and the mini "stories" that begin each chapter were a bit cheesy). I particularly appreciated the way each scenario drew on the foundation of understanding from the previous ones. ...more
Jeff Brateman
Apr 18, 2010 rated it really liked it
Good intro read for those with or without an astrophysics background about the how and the effects of different situations having to do with the moon, earth, and sun placement. Pretty quick read, but I did skim a lot of it because it got repetitive.
Jul 21, 2010 rated it liked it
Shelves: non-fiction
It was interesting to read a book that by discussing different what-if scenarios involving the earth or the moon, ended up teaching me about so many different branches of science. Odd to see how much I've forgotten and how much I never learned...
Dane Mamula
Sep 16, 2010 rated it really liked it
Book asks and answers some really weird questions..."what if", questions to be precise (as if you couldn't determine that from the title). But almost all of them are really well-thought out and based off fact, not just some rabbit out of the hat mysticism. Good stuff. ...more
Mar 21, 2011 rated it liked it
Spent more time and went more in depth than what I was hoping to find. Still and interesting read and had I been in a different mindset I may have rated it higher. It is fascinating to know how much has to line up for life to exist the way it does on our planet.
Aug 16, 2010 rated it it was ok
worth skimming through
Feb 14, 2011 rated it liked it
Very helpful as I was just making stuff up for ' Verthandi '. Answered some questions. ...more
Snail in Danger (Sid) Nicolaides
Mar 07, 2011 marked it as decided-not-to-read
The weird historical fiction introductions turned me off reading the actual speculative material. Queen Isabella working on the galley of one of Columbus's ships as a spy or something? Right. ...more
May 05, 2012 rated it it was amazing
Deliciously accessible for a non-astrophysicist
This one was a little physics heavy for me and I couldn't get through it :( ...more
Becka Lloyd
Mar 28, 2013 rated it really liked it
DEfinitely interesting. If you're into this kind of thing, you'll find it of interest...if not...I'd avoid it :) ...more
Oct 01, 2014 rated it really liked it
Fun non-fiction Q&A book. I found it fascinating as a reference for writing about other planetary arrangements. It was a little thick and ponderous on the language.
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