In Beowulf, the significance is that Grendel will soon meet his fate.
Grendel is about to meet his fate.
These lines are foreshadowing that the character will not be able to harm any more people after that specific evening due to fate or destiny (Wyrd). This suggests a potential turning point or consequence for the character's actions.
Earth and Venus. From Earth Venus and Mercury are planets visible as "morning" and "evening" stars. From Venus, Mercury would appear in the morning and evening sky. From Mars I would expect Earth, Venus, and Mercury to all be morning and evening "stars."
There is no significance. It is fatal for life on earth.
The significance of Earth's atmosphere is the sustainment of land based life.
Yes.
shadows are longer in the morning and evening because the earth is rotating and when the earth is facing the sun it is day and when it isn't it is night
gravity of the earth
Planet earth is the only planet that we know of that has life on it.
Earth is visible all the time to every human being.
Any planets further in would tend to appear as morning or evening "stars." So from Mars the planets Earth, Venus, and Mercury would all be morning and evening "stars." Venus, of course, would be much brighter than Earth, even though Earth would generally be closer. Earth has a lower albedo.
because they shiny and they are far from the earth