The expansion of the universe should be slowing down because gravity should be pulling everything back together. But it is not slowing down. In fact, the expansion appears to be speeding up. The name of what is causing the expansion to accelerate is "dark energy", even though nobody has figured out what it is. Keep in mind that the term does not necessarily refer to a form of energy.
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Dark Energy is the placeholder for what is causing the expansion of the universe. We currently do not know what it is, hence dark. Also Deepak Chopra is a quackeroo. Don't believe everything you hear from him.
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Perhaps you are referring to dark energy? Gee, if there were only some resource you could find some information?
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Shhhhh! It's a secret