1. Blackness: Instead of the blue we're used to, the sky would be completely black during the day. This is because there would be no air molecules to scatter sunlight, causing the blue hue we perceive.
2. Bright Stars: We would see stars all the time, even during the day. The only reason we can't see them during the day is that the atmosphere scatters sunlight, making the sky bright enough to obscure the fainter light from stars.
3. Sharp Boundaries: The line between day and night would be very sharp and distinct, as there would be no atmospheric scattering to create a gradual twilight. The sun would appear as a blindingly bright white disk against the black backdrop.
4. Unfiltered Radiation: We would be exposed to the full spectrum of harmful radiation from the sun, including ultraviolet (UV) rays. This could be deadly for all life forms.
5. Cold Temperatures: Without the atmosphere's insulating effect, temperatures would fluctuate wildly between scorching hot during the day and freezing cold at night.
6. Meteors: We would see many more meteors, as they would no longer burn up in the atmosphere. This would be a spectacular but potentially dangerous sight.
7. No Clouds or Rain: Of course, there would be no clouds, rain, snow, or other weather phenomena since these are all created by the atmosphere.
In essence, without an atmosphere, Earth would be a very hostile and lifeless place. The sky would be a stark contrast to the vibrant blue we know, offering both beautiful and dangerous sights.
