Final answer:
The inference from measuring the redshift-distance relation with supernovae is that the universe may be expanding at an accelerating rate, rather than slowing due to gravity as previously thought. This conclusion has been supported by multiple subsequent observations and led to the awarding of the 2011 Nobel Prize in Physics.
Step-by-step explanation:
When we measure the redshift-distance relation with supernovae, we are inferring the expansion rate of the universe at different times in its history. By using Type Ia supernovae as standard candles, researchers can calculate how far these supernovae are from Earth. Observations in 1998 showed that these supernovae were fainter than expected from Hubble's law, suggesting that the universe might be expanding at an accelerating rate, contrary to the expectation that the expansion would be slowing down due to gravity. This implication of an accelerating universe was so revolutionary that the discovery received the 2011 Nobel Prize in Physics. Subsequent studies have continued to support this astonishing finding, indicating that we live in a universe with an expansion rate that has not remained constant over time.