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The Question

(Submitted September 04, 2001)

Recent studies of exploding supernovae show that the Universe' expansion is accelerating. Hubble's law uses Hubble's constant (independent from distance) to calculate the distance for remote objects. Aren't both calculations in a contradiction? If the Universe is accelerating then Hubble's constant must not be a constant too.

The Answer

You are correct. If verified, the observation of an accelerating universe means that Hubble's constant is not in fact a constant after all. This is how science works - Hubble came up with a good idea that fit the observed data of the time. But technology and funding improves as time goes by, and more sensitive data has resulted in the idea being modified.

with regards,

Martin Still & Kevin Boyce
for NASA's "Ask an Astrophysicist"

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