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.
There is no significance. It is fatal for life on earth.
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."
The significance of Earth's atmosphere is the sustainment of land based life.
Yes.
The orientation of constellations in the sky changes throughout the year due to the Earth's orbit around the Sun. In January, Leo is on the opposite side of the Earth as the Sun, making it visible in the evening sky in the east. In July, Leo is on the same side of the Earth as the Sun, causing it to be visible in the evening sky in the west.
Earth is visible all the time to every human being.
gravity of the earth
Planet earth is the only planet that we know of that has life on it.
because they shiny and they are far from the earth
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.