That&#x27;s an interesting point. There are different ways to look at it. In terms of a huge change in our understanding of the world, I agree. But I think Asimov is thinking in terms of effectiveness of the model in explaining observations and making predictions.<p>In say 2000 BC, a flat-earth and spherical-earth theory were probably both about the same level of effectiveness in explaining observations and making predictions about new observations. In the year 1800, Newton&#x27;s mechanics were extremely effective in making correct predictions. As technology advanced and new observations were possible, some gaps were revealed. But even today, Newton&#x27;s mechanics are extremely effective and accurate for explaining and predicting many observations in our world; just not all of it. Einstein&#x27;s relativity does a much better job, but also not perfect.<p>Now again, you can say that there is a huge fundamental difference between the flat-earth and round-earth theories, or between Newton and Einstein, and I agree, but here I think Asimov is just arguing from this &quot;correctness of model in explaining&#x2F;predicting&quot; perspective.