Nature of The Absolute Horizon
The definition of an absolute horizon is sometimes referred to as teleological, meaning that it cannot be known where the absolute horizon is without knowing the entire evolution of the universe, including the future. This is both an advantage and a disadvantage. The advantage is that this notion of a horizon is very geometrical, and does not depend on the observer, unlike apparent horizons, for example. The disadvantage is that it requires the full history (all the way into the future) of the spacetime to be known. In the case of numerical relativity, where a spacetime is simply being evolved into the future, only a finite portion of the spacetime can be known.
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Famous quotes containing the words nature, absolute and/or horizon:
“So Nature deals with us, and takes away
Our playthings one by one, and by the hand
Leads us to rest so gently, that we go
Scarce knowing if we wish to go or stay,
Being too full of sleep to understand
How far the unknown transcends the what we
know.”
—Henry Wadsworth Longfellow (1809–1882)
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“The thought of you will constantly elevate my life; it will be something always above the horizon to behold, as when I look up at the evening star. I think I know your thoughts without seeing you, and as well here as in Concord. You are not at all strange to me.”
—Henry David Thoreau (1817–1862)