- Solar flares
- The WOW signal: An unusual extremely strong 72-second radio transmission detected coming from the direction of the constellation "Sagittarius". It is the strongest candidate for an extraterrestrial (alien) radio transmission ever detected.
- The Drake Equation: An equation to estimate the quantity of active communicative alien civilizations in our galaxy.
- Fermi's paradox: Given how vast & old space is, and how many sun-like stars ("suns") there are, and how many Earth-like planets orbit said suns, and given how quickly humans developed space travel, where are all of the aliens? ¿Where is everybody else?
The Zoo Hypothesis:
One of many theoretical explanations for Fermi's paradox (see "Fermi's Paradox" section).
Hypothesizes that aliens are aware of mankind, but decline to ineract with nor make themselves known to man.
Possible reasons for their decision include (but are not limited to):
- That we are like animals in a zoo to them.
- For the purpose of entertainment.
- To study us. (¿probes?)
- To not disturb our natural evolution & development.
- To avoid conflict (war).
- To avoid contamination (e.g. disease) in either direction.
- Arecibo message
- Radio Quiet Zone(s), including United States National Radio Quiet Zone, & related Radio silence
- Great Filter: Whatever is preventing the abundance of extraterrestrial life that Fermi's Paradox (see Fermi's Paradox section) expects. Perhaps this filter is abiogenesis (i.e. the process by which life arose from non-living matter), perhaps it is between abiogenesis and mankind's past, perhaps it is during our present (e.g. nuclear weapons, falling birthrates, pollution), or it may still be in mankind's future that we have yet to encounter.
Both Space & Weather
- NASA Clean Air Study: Certain plants remove many harmful polutants from the air
- Airglow & Aurora
- The Carrington Event
- Fresh fluffy snow is porous, thus absorbing sound vibrations, making the environment quieter.