Why might the conclusions of scientific studies, later be viewed as invalid?

The conclusions of some scientific studies could later be viewed as invalid because there could be more studies done that disprove the findings of earlier studies. This would make the earlier studies be viewed as invalid because they no longer are correct in what they state.

Explanation:

the gravitational force on an object increase as the mass of an object also, im not going to report you, but this question should be under the science category, not health