When we introduce a new theory, old experiments need to be seen to back it up up, even though that is not what they were originally performed for.
Even if old experiments do not seem to back our theories up we need to be able to explain why they did not observe what we propose now. We may be measuring what they did not or expecting what they discarded as irrelevant. In medicine this is crucial in reviewing older research; past generations have marked patients we would consider to be in grave status as healthy and patients we now understanding as going through natural processes as deathly.
Even if old experiments do not seem to back our theories up we need to be able to explain why they did not observe what we propose now. We may be measuring what they did not or expecting what they discarded as irrelevant. In medicine this is crucial in reviewing older research; past generations have marked patients we would consider to be in grave status as healthy and patients we now understanding as going through natural processes as deathly.