A former NASA astronaut, Leroy Chiao, has warned that life on Earth will eventually die out because the cycle of life and death is the "natural progression just like individual lives on our planet."
But, according to Chiao, when life eventually dies off on Earth it will be replaced by other forms of life elsewhere in our galaxy and universe. Life exists all over our universe, Chiao asserts, and it is always starting in some parts and dying out in others.
Life on Earth could end either through natural causes or through civilization's self-destructive tendencies, Chiao wrotes in an article published on Space.com on September 2, 2016.
But regardless of what eventually causes extinction of life on Earth, it will be replaced by other forms of life in other parts of our galaxy and universe because life is widespread in our universe and goes through a cycle of birth and death as part of its natural progression.
According to the former astronaut, it would be "the height of arrogance" to believe we are alone in our galaxy or universe. Our Milky Way Galaxy is teeming with life and advanced civilizations. But civilizations are unaware of each other because of the vast distances that separate them.
"I believe that there is life all over our universe," he writes. "I believe that at some point, life on Earth will die out, either from natural causes, or from our own doing. To me, this is a natural progression, just like individual lives on our planet."
"Life on Earth will die out... To me, this is a natural progression."
"Life is always starting in some parts... and dying out in others. We don't know about each other because the distances are so vast."To illustrate how natural causes could eventually cause extinction of life on Earth, Chiao points out that Mars had a much different environment hundreds of millions of years ago. Mars had a thick, protective atmosphere like Earth's. The atmosphere may have incubated simple life forms by protecting the surface of the planet from harmful solar radiation. Mars was also much warmer millions of years ago and scientists believe that liquid water flowed on the surface of the planet.
Chiao believes that because of the vast distances between stars, we should focus on searching for extraterrestrial life in our space neighborhood, such as on Mars.
"For me, the discovery of incontrovertible evidence of past or present life on Mars would prove my theory on alien life, without having to send probes to other star systems," Chiao comments.
But Chiao, who worked with NASA for 15 years (1990-2005) and has spent 230 days in space, believes that discovery of Proxima b supports his theory that life is widely distributed in our galaxy.
"With the recent discovery of a possible Earth-like planet around a star in our cosmic backyard, tantalizing new questions are being raised about the possibility of finding life elsewhere in the universe," he writes.
"My hope is that we will find answers in my lifetime, by continuing to look even closer than 'down the block.' Let's continue to explore Mars, which is in our own 'backyard!'" he concludes.
Experts have dubbed Proxima b, a newly discovered exoplanet about 25 trillion miles (4.25 light years) away, a "second Earth" because of its remarkably Earth-like nature.
The planet, which orbits its star in the "habitable zone," is believed to have a rocky Earth-like terrain and Earth-like surface temperature estimated to range between -90° and 30° Celsius (-130 and 86 Fahrenheit). The estimated range of temperatures means the planet could have liquid water running on its surface, according to scientists.
Discovery of Proxima b appears to confirm suspicions that our galaxy has a huge population of Earth-like planets that could support Earth-like life. Already, astronomers using the Kepler Space Telescope have discovered thousands of exoplanets. Scientists recently listed 20 of the thousands of known exoplanets that are most likely to be rocky Earth-like planets supporting Earth-like life.
Proxima b is the closest of all known Earth-like planets and likely the closest we will ever find as it orbits the dwarf star Proxima Centauri, the nearest star to our Sun.
"Measurements indicate that Proxima b is a rocky planet, just slightly larger than Earth, orbiting the star at the right distance to be able to support liquid water on its surface, and thus perhaps life," according to Chiao.
Although scientists say Proxima b is Earth-like, it is different from Earth in significant aspects. It has an orbital period of only 11 days compared with Earth's 365.
"Also the radiation environment is estimated to be much harsher than that for Earth," Chiao added. "Still, scientists say some kind of life could exist there."
The ex-NASA astronomer does not share the optimism that technology will save mankind from eventual extinction.
"Unlike many people, including several of my astronaut colleagues, I don't think that technology will save us," he writes. "Indeed, there are strong arguments that after enabling life to thrive, technology is now hastening our collective demise."
Chiao is a former International Space Station (ISS) commander who completed four space missions and six spacewalks during 15 years with NASA.
[Featured Image by Apollo 17 crew/NASA/Wikimedia Commons Public Domain]