1. Astro / Stars
- Astronautics
- Astrophysics, Astrodynamics
- Astronomy
- Age, Lifespan of Stars
- Radio, Microwave, Infrared, Visible, Ultraviolet, X-Ray, Gamma Ray
- Space-based, Earth-based
- Astrology
- Astrogeology, Astrohydrology, Astroarcheology
- Astrobiology
2. Extraterrestrial
- SETI
- Science Fiction
- Star Trek
- UFOs
- Aliens
- Etc
3. Terrestrial / Gaia All Life
- Humans
- Monkeys, Apes, Chimpanzees, Dolphins, Whales, Horses, Cows, Elephants, Pigs, Dogs, Cats, etc
- Birds, Fish, Amphibians, Reptiles, etc
- Ants, Bees, Insects, etc
- Amoeba, Bacteria, Microorganisms, etc
- Plants, Trees, Flowers, etc
4. Metaphysics
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