The Case for a Creator - Lee Strobel [89]
“The problem is that if the probability of life at any one star is zero, then the probability for all the stars remains zero,” he said.
“Zero?” I replied. “There are more than a quarter million stars in that globular cluster. Don’t you think any of them harbor planets with life?”
Gonzalez stood his ground. “A globular cluster is one of the worst places in the entire galaxy to expect any life,” he replied.
“Why?”
“Two reasons,” he said. “First, globular clusters are among the most ancient things in our galaxy. Since they’re extremely old, their stars have a very low abundance of heavy elements—carbon, nitrogen, oxygen, phosphorous, calcium, and so on. Instead, they’re made up almost entirely of hydrogen and helium. In contrast, Earth is composed of iron, oxygen, magnesium, and silicone. Next comes sulfur.
“You see, the Big Bang produced basically hydrogen and helium. That’s what the earliest stars were made of. The heavier elements were synthesized—cooked, if you will—in the interior of stars. Eventually, when these stars exploded as supernovae, these elements got expelled into the interstellar medium. They coalesced into other stars, where more heavy elements were cooked. Then they were expelled again and again, with stars subsequently containing ever-greater amounts of these ‘metals,’ or heavier elements.
“Now, you need these elements to eventually build terrestrial planets like Earth. Because the very old stars in globular clusters formed so early that they’re composed virtually exclusively of hydrogen and helium, they’re not going to have planets accompanying them. Maybe there will be dust, or grains, or boulders, but that’s about it. You’re not going to have Earth-size planets.
“The second problem is that globular clusters are so densely packed with stars that they wouldn’t allow for stable, circular orbits to exist around them. The gravitational pull of the stars would create elliptical orbits that would take a hypothetical planet into extremes of cold and heat, which would create a life-prohibitive situation.”
His assessment made sense, but it caused me to wonder why Sagan and Drake, both knowledgeable astronomers, would waste their time trying to communicate with the stars of M13. Gonzalez shook his head when I asked him about it.
“It’s really surprising that they would think there would be any chance of a civilization receiving their message in a globular cluster,” Gonzalez said. “They should have known better! Frankly, I think they were so deluded by their complete belief in the metaphysical Copernican Principle—that life was just going to be everywhere in the galaxy—that they overlooked the facts.”
LIVING IN THE SAFE ZONE
Gonzalez’s explanation made me wonder about the suitability of other places to harbor intelligent life. I knew that there are three basic types of galaxies in our universe. First, there are spiral galaxies like our own Milky Way. These are dominated by a central spherical bulge and a disk with “spiral arms” extending outward from the nucleus in a spiral pattern, resembling a celestial pinwheel. Second, there are elliptical galaxies, which are sort of egg-shaped. And, third, there are irregular galaxies, which appear disorganized and distorted. I asked Gonzalez to assess the life-bearing potential of each one.
“Certainly, our type of galaxy optimizes habitability, because it provides safe zones,” he said, his tone professorial. “And Earth happens to be located in a safe area, which is why life has been able to flourish here.
“You see, galaxies have varying degrees of star formation, where interstellar gases coalesce to form stars, star clusters, and massive stars that blow up as supernovae. Places with active star formation are very dangerous, because that’s where you have supernovae exploding at a fairly high rate.