Dusk
It means just below the visual horizon. Although light waves can't see below the horizon, radio waves can, a bit.
beneath
If the North Star sinks below the horizon, it means you are moving southward. The North Star is located directly above the Earth's North Pole, so as you move away from the North Pole towards the equator in a southerly direction, the angle of the North Star above the horizon will decrease, eventually causing it to disappear below the horizon.
means when the sun is low on the horizon -- early morning or late afternoon.
"Circumpolar" means literally 'around the pole', referring to a star that from a given observer's latitude does not go below the horizon
When the North Star sinks below the horizon, it indicates that you are moving southward. This phenomenon is due to the Earth's rotation on its axis and the tilt of its axis, causing different stars to be visible at different latitudes.
It's the circle whose radius is the same as your north latitude. (That means it depends on where you are, and if you're south of the equator, Polaris is below your horizon anyway and there is no such circle.)
twilight means when the sun rises, or when it sets/ the soft, diffused light from the sky when the sun is below the horizon. So they really isn't one, because if it can be sunrise and sun set, they isn't an oppisite. Maybe you could find a word which means the sun is above the horizon.
In Internet Slang, the letters PSB in an email means Please See Below. Note that not everyone will know what PSB means.
It means: "cousin disappears"
Twilight means the time of the day where the sun is below the horizon line in either the morning of the evening.
it means that it goes to the horizon because the horizon looks like it meets the sky