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![]() the announcements in 1998 and subsequent measurements, we now know that the accelerated expansion of the universe did not start until sometime in the last 10 billion years, |
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![]() is a dynamic, time-evolving, and spatially dependent form of energy with negative pressure sufficient to drive the accelerating expansion, ... Whereas the cosmological constant is a very specific form of energy — vacuum energy — quintessence encompasses a wide class of possibilities. |
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