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The professor at the end (at about 7:28), used the formula for scale factor and redshift as a(t) = 1/z, instead of the actual one a(t) = 1/1+z. And when we apply both of them, they give very different results. So, how could the professor use the first formula, which we were never taught about previously and I'm inclined to think is incorrect?

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# I Scale factor/redshift formula wrong at the end?

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