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[Book Reviews] Where Are All the Aliens? 'Out There' Book Excerpt.

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Post time: 9-1-2019 10:28:26 Posted From Mobile Phone
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"Out There,"  Space.com senior writer Mike Wall's book about the search for alien life (among other things), comes out Nov. 13, 2018.
Credit: Grand Central Publishing
▼ In " OUT THERE: A Scientific Guide to Alien Life, Antimatter, and Human Space Travel (for the  Cosmically Curious)," (Grand Central Publishing, 2018),  Space.com senior writer Mike Wall tackles the most pressing questions about alien life. For example, how are scientists searching for ET? What might aliens look like, would they want to kill us, and are they likely to have sex? The book, which comes out Nov. 13 and was illustrated by Karl Tate, also talks about humanity's quest to get off its natal rock and spread out into the solar system. You can read an excerpt below.
Chapter 1: Where Is Everybody?
In 1950, Nobel Prize-winning physicist Enrico Fermi — who led the team that created the first-ever nuclear reactor, the inadequately named Chicago Pile-1 — and a few of his colleagues were discussing UFOs during their lunch break. The conversation prompted Fermi to ask his companions, "Where is everybody?"
Fermi meant that the lack of visits by ET is distinctly odd. The Milky Way harbors hundreds of billions of stars and is about 13 billion years old, so there has been plenty of time and opportunity for alien civilizations to rise and spread throughout the galaxy. By some estimates, a colonization-minded species with propulsion technology not much more advanced than our own could island-hop its way to every corner of the Milky Way in just a few million years.
The physicist's simple question is enshrined now as Fermi's paradox— one of the two coolest paradoxes of all time, along with the crocodile paradox — and it continues to puzzle scientists to this day. Indeed, the mystery has deepened considerably over the years. For one thing, we're not just talking about the lack of visitation anymore. In 1960, 6 years after Fermi's death, astronomer Frank Drake pointed a radio telescope at West Virginia's Green Bank Observatory at the nearby sun-like stars Tau Ceti and Epsilon Eridani, kicking off the search for extraterrestrial intelligence (SETI).Nearly 60 years later, SETI scientists are still hunting for the first confirmed peep from ET.
Then there's the exoplanet revolution. Alien worlds were purely hypothetical objects in Fermi's day and for decades afterward; scientists didn't announce the first confirmed detection of a planet beyond the solar system until 1992. But in the last decade or so, NASA's Kepler space telescopeand other instruments have revealed that the cosmos is teeming with possibly life-supporting worlds. Kepler's discoveries suggest that about 20 percent of the Milky Way's sun-like stars host an Earth-sized world in the "habitable zone" — that just-right range of orbital distances that would allow you to walk around in flip-flops pretty much year-round. The proportion appears to be similar for red dwarfs, the small, dim stars that dominate our galaxy. (About 75 percent of Milky Way stars are red dwarfs, whereas just 10 percent or so are similar to our sun.)
"There's a lot of real estate out there, and we now know that," said radio astronomer Jill Tarter, who co-founded the SETI Institute in Mountain View, California, and served as the inspiration for Ellie Arroway, the lead character in Carl Sagan's novelContactand the movie based on it.
Not all of this real estate is way out in the boonies, either. The sun's nearest neighbor, the red dwarf Proxima Centauri, hosts an Earth-size planet in the habitable zone. Seven rocky planets circle the dwarf star TRAPPIST-1, which isn't much farther away from us in the cosmic scheme of things — and three of those worlds may be able to support life as we know it. (Proxima Centauri and TRAPPIST-1 lie about 4.2 light-years and 39 light-years from Earth, respectively. The entire Milky Way is about 100,000 light-years wide.)
So, again: where is everybody? Nobody knows. The Fermi paradox is tougher than a Brazil nut, and scientists haven't cracked it yet. But it's not for lack of trying. They've advanced hundreds of hypotheses to explain it. As varied as these ideas are, they all encompass just a few basic possibilities, as physicist Stephen Webb noted in his bookIf the Universe Is Teeming with Aliens, Where Is Everybody?Let's take a look at each of these three explanation families.
Possibility 1: What paradox? Intelligent aliens have already messed with us
You may already have wandered off, irritated or incensed that I put the Fermi paradox on equal footing with the beloved crocodile paradox. Perhaps you're now thumbing through a dog-eared copy ofChariots of the Gods?or watching YouTube clips of that "alien autopsy" TV special that Fox aired in the 1990s.
Indeed, one possible resolution of the Fermi paradox is that it's no paradox at all, because ET has already journeyed to Earth. Adherents of this explanation often point to UFO sightings and alien abduction stories, topics that you can read about in chapter 10. For our purposes here, suffice it to say that scientists generally don't regard any of these reports as convincing evidence of alien life. (If they did, you definitely would have heard about it.)
There are more subtle possibilities in play as well. For example, what if ET came to our planet long ago, before people were around to be probed? Unless the voyaging aliens were particularly interested in us, this is much more likely than a documented visit, given that our species has existed for just the last 200,000 years of Earth's 4.5-billion-year history and has been capable of capturing encounters on blurry, low-light video for only a few decades.
Let's indulge in some wild speculation, because it's fun! Say Earth has been colonized many times over the eons by greedy, grabby alien civilizations, each of which ground the planet's native species into the dust in the process. (Don't get too high and mighty: pioneering humans have tended to wreak ecological havoc as we've explored the globe.) As astrophysicist and sci-fi author David Brin has pointed out, a history of such oppression could explain why it took intelligent life so long to arise on our planet as well as the radio silence in our galactic neighborhood. Maybe Earth is the only planet for light-years around to have recovered from the ravages of invasion.
If you squint a little, this scenario lines up with the five mass extinctions that scientists have identified in the fossil record. These great purges occurred about 450 million years ago, 375 million years ago, 251 million years ago, 200 million years ago, and, most famously, 66 million years ago, when an asteroid strike wiped out three-quarters of all Earth's species, including the dinosaurs. "It may not be preposterous," Brin wrote in a seminal 1983 paper, to compare the intervals between these extinction events and the time it might take for different waves of invasion to wash over Earth. The dino-killing asteroid could even have been a weapon of war, slung by a space-dwelling alien faction with a beef against their brethren on Earth.
Brin didn't mean to suggest that any of this actually happened, and neither do I. There's no evidence that it did — no spacecraft entombed in ancient amber, no ruins of a 200-million-year-old city — and I certainly wouldn't put any money on it. But it's possible.
Possibility 2: They're out there, but we haven't found them yet (▪ ▪ ▪)

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Post time: 14-1-2019 16:03:57
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Out There: A Scientific Guide to Alien Life, Antimatter, and Human Space Travel (For the Cosmically Curious) by Michael Wall has been posted.



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Pedro_P + 15 Good info... Thanks for sharing it.

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