"What if?" is a question that science-fiction authors sometimes ask themselves to come up with a novel, tweaking this or that fact in order to create a world sort of like ours, but with a significant twist. These are called "allohistories" or "alternative histories."
But sometimes historians use what-ifs to get a picture of the history surrounding an event or person uninfluenced by their presence. Significant discoveries and important people color our recollection of the rest of the world around them, giving us an unalterably weighted picture of their era.
Writing in last month's Nautilus, Philip Ball does a little of that kind of sketching with some of the major discoveries of science. If the particular person associated with a great discovery or theory had not existed, would the same idea have been developed or uncovered? And who would have been most likely to do so?
In just about every case, Ball thinks that the discovery would have been made anyway. In some cases, the person he puts forward as the most likely candidate was already working towards the same idea and simply came in second in the history we know. Christiaan Huygens, for example, studied collisions and was definitely on the path of Isaac Newton's Third Law of Motion and had already derived an understanding of the Second Law.
Some of the famous scientists explicitly mention their forbears and it's not tough to believe those same forbears might have come to the conclusions their successors did. Albert Einstein's theories of relativity came about because the Scot physicist James Clerk Maxwell had already predicted the speed of light was a constant, and Einstein started wondering what would happen if that were so. Maxwell died young, about 35 years before Einstein published, and it's not a stretch to believe he would have started playing around the same questions that teased Einstein.
Ball suggests that many of the great discoveries he's examining would have happened at about the same time as they did anyway, perhaps even earlier. A couple might have been delayed -- Ball sees Johannes Kepler as the most likely person to formulate Copernicus' view of the heliocentric solar system, a few decades after Copernicus' own work.
He leaves examination of Charles Darwin's theory of natural selection until the last. Ball holds that it's pretty tough to figure out which of the many competing understandings of evolution floating around the 19th century might have taken hold had the naturalist himself never lived. When you add in that Darwin's original theory has been added to over the years based on new discoveries about genetics and DNA, the reality is that the most plausible modern evolutionary theories could have shown up coming from several of those old competitors, especially since modern theory carries features of those old theories in them.
Ball comes to a pretty reasonable conclusion about the theories he checks into, which is that someone would have figured them out anyway. Since they describe reality, then eventually someone would have tripped over them. Relativity describes the universe and whether Albert Einstein or someone else describes it doesn't change that.