Q: It is said that the universe appears to be expanding faster the farther out we see. Instead of claiming that the universe is in fact expanding exponentially faster, doesn’t it make more sense to say that the universe WAS expanding faster the farther back in time we see? And does this mean that the most proximate areas in our space/time continuum are in fact moving slower than those remote regions?
—Eric Valdez, Los Angeles, Calif.
A: No, it does not work. It is true that observations show that standard candles are dimmer than what they should be if there was no dark energy. You are asking whether this observation is enough to decide if the universe expands faster today or did it expand faster in the past.
The answer is that the dark energy density remains constant with time, while the (dark) matter and radiation densities increase as fast as we do toward the past; therefore, it is impossible for dark energy to have played any role in the expansion of the universe in the past. General relativity is very clear about it: If things appear dimmer than what we would expect in a universe with only matter and radiation, then there must be some dark energy and the expansion must have accelerated recently only.
—Dr. Ludovic Van Waerbeke, University of British Columbia
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