This Hubble infrared image is of a dense star cluster that surrounds the center of our Milky Way galaxy. That's a lot of stars, around 500,000 in this image alone! Its currently estimated that our galaxy contains somewhere between 100 to 400 billion stars.
Image credit: https://www.nasa.gov/image-feature/hubble-peers-into-the-heart-of-the-milky-way-galaxy
We live in a barred spiral galaxy that is roughly 100,000 light years across and about 2,000 light years thick. Our Sun, the Earth, and everybody we know is currently thought to be within the inner edge of the Orion-Arm approximately 27,000 light years distance from the center. In other words, the light from the center we see today took 27,000 years to reach us. Putting this into perspective, the light from our nearest neighboring star, Proxima Centauri, takes 4.2 years to reach us, and the light from our Sun which is 93 million miles away takes 8.3 minutes.
Just as the Earth rotates around the Sun, our Sun rotates around the galaxy with a period of ~230 million years. The last time our Sun was in a similar position in the galaxy the Earth was at the end of the Triassic period with dinosaurs roaming the planet. What will the Earth be like the next time around? Hopefully we will still be around in some form or another, and if so we will have very likely evolved into a different species. What we end up becoming is driven by evolutionary pressures we as humans face today.
I'm going to take this moment to acknowledge the scientists that I work with who utilize the telescopes here in Hawaii and elsewhere to perform a wide variety of scientific studies. Two of the most recent and noteworthy are the imaging of the supermassive black hole (SMBH) in M87 galaxy followed by the imaging of Sagittarius A* SMBH in the center of our Milky Way. Maybe less exciting but no less important are the scientists who perform astrometric measurements to map out the galaxy we live in. In my mind they are akin to the navigators for the seafaring explorers of the past.
Image credit: https://www.universetoday.com/65343/what-galaxy-is-the-earth-in/
It's been estimated that our Milky Way galaxy hosts at least 300 million stars with Earth sized planets in the habitable zone. That's a pretty big number! But just because there are planets similar to Earth doesn't mean there is life on board. Look at Venus and Mars as an example.
The question of how life got started on Earth is still unknown. Our Sun and its planets including Earth were formed about 4.5 billion year ago. It was a hostile place for the first billion years or so due to constant bombardment from comet and asteroids. As the number of asteroid impacts tapered off and the surfaced cooled there may have been a point in time when the Earth was a pristine world with oceans, land, an atmosphere, but devoid of life. But this didn't last long because the first fossil evidence of life dates back to around 3.5 billion years ago.
One could fathom that there are other worlds with similar environments as our planet Earth. How long can a world with oceans of water and atmosphere exist without the formation of life? My intuitive feeling is that if such a world exists then some form of life will take hold of it.
Image credit: https://www.jpl.nasa.gov/images/pia17999-kepler-186f-the-first-earth-size-planet-in-the-habitable-zone-artists-concept
Most technical people with whom I interact with and are admittedly an odd group believe that life such as bacteria and possibly even simple multicellular life such as plants and jellyfish may be common outside of the Earth. But beyond that peoples opinions differ greatly because we simply don't know.
It's my opinion that given the right environment and enough time, it is inevitable that life evolves to become more complex due to evolutionary pressures to compete for resources. Here on Earth plant and animal species have continued to change to adapt and optimize to their environment. Mutations that are advantageous are passed on while less successful ones are suppressed. This constant evolution, however, doesn't necessarily have to continue forever. Case in point, there is a species of shark that exists today with fossil records indicating that they have existed in the same physical form over the past 150 million years! Its as if nature created the perfect marine apex predator.
On the other hand homo sapiens have only recently evolved to become what we are today. A million years ago we were quite a different species. What sets us apart from other creatures is our level of intelligence but it comes at the heavy price of carrying around a big brain that requires a lot of energy. We don't have sharp teeth, claws, venum or armor, run slow and can be taken down by an agitated or hungry cougar. Many people, including some evolutionary biologists, believe that the development of intelligence capable of manipulating atoms to constructing megastructures is a fluke and likely won't happen again either here or elsewhere. But I'm of the mindset that intelligence emerged on Earth to fill a specific niche and that if other worlds present similar niches they will be filled just the same.
Image credit: https://www.bbc.com/future/article/20221101-should-extraterrestrial-life-be-granted-sentient-rights
SETI has been around since the early 1960s and focused on radio emissions from potential civilizations. We are still searching the radio spectrum today but with technology that permits orders of magnitude increase in sky and frequency coverage.
What does 60+ years of null results for SETI indicate?
Image credit: https://www.thesmartset.com/should-we-stop-looking-for-intelligent-life/
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