Earlier this month, Ken Ham, the founder of the Creation Museum, in Petersburg, Kentucky, held a debate with Bill Nye at the museum. Within the creationist crowd, Ham represents the young-Earth wing, which believes that the planet is around six thousand years old. He also has other extreme interpretations of biblical claims: for example, he believes that the Tyrannosaurus rex and other dinosaurs were actually vegetarians that lived in the Garden of Eden before the fall of Adam and Eve.

Ham often stresses a line of argument made within the broader creationist community, which resonates, at least somewhat, with the public at large. “There’s experimental or observational science, as we call it. That’s using the scientific method, observation, measurement, experiment, testing,” he said during the debate. “When we’re talking about origins, we’re talking about the past. We’re talking about our origins. You weren’t there, you can’t observe that…. When you’re talking about the past, we like to call that origins or historical science.” In other words, Ham was saying that there is a fundamental difference between what creationists call the “historical sciences”—areas of study, like astronomy, geology, and evolutionary biology, that give us information about the early Earth and the evolution of life—and other sciences, like physics and chemistry, which appear to be based on experiments done in the laboratory today.

On the surface, this does not seem completely unreasonable. There is, after all, a difference between an observation and an experiment. In the laboratory, one can have much better control when attempting to establish cause-and-effect relationships. However, to suggest that somehow this qualitative difference between observation and experiment translates into any sort of deep qualitative difference between the different sciences mentioned above is to demonstrate a fundamental misunderstanding of the nature of science itself.

In the first place, science doesn’t involve merely telling stories about history. If it did, scientific explanations might not have any claim to a higher level of veracity than religious stories. The stories that science does tell have empirical consequences, and make physical predictions that can be tested.

In this sense, all science is historical science. We make observations about past events, based on everything from data gathered in the laboratory yesterday to remnants of phenomena, like meteor impacts or stellar explosions, which may have happened billions of years ago. We then use them to make predictions about the future, about experiments or observations that have not yet taken place. To quibble about how long ago the original data was generated is to miss the point. Predictions about the future, rather than a focus on the past, is what gives science its ultimate explanatory and technological power.

Let’s consider some examples. In the field of evolutionary biology, scientists can postulate an evolutionary relationship between species, which suggests the development of some biological characteristic—legs, say, as animals moved from the sea to the land, or eyes, as organisms developed photoreceptors that helped to guide their search for food. One can then search for fossil evidence of such developments, looking for transitional fossils that demonstrate gradual evolution. It is a prediction that such transitional species existed. Given the sparseness of the fossil record, there is no guarantee of unearthing evidence of such species, but, in the cases of legs and eyes, the predictions have been validated by discoveries made over the past decades.

Or, take my favorite example: the prediction of a genetic relationship between the great apes and humans via a common ancestor, as taught in many (I wish it were all) introductory biology courses. Humans have twenty-three pairs of chromosomes, where all the great apes have twenty-four pairs. If they have a common ancestor, this difference must be explained. One possibility is that two of the chromosomes in the great apes fused together at some point in the human lineage. But this makes two testable predictions. Each chromosome has a characteristic end, called a telomere, and a distinctive central part, called a centromere. If fusion had occurred, then one of the human chromosomes should, in its central region, include the remnants of the two fused telomeres, lined up end to end. It also should have, at between roughly a quarter and three-quarters of the way along the chromosome, a structure identical to that of the centromeres of the great-ape chromosomes. This prediction, tested in the laboratory today, and not in the distant past, has been beautifully verified.

Now, think about geology, another bugaboo of the young-Earth creationists. The phenomenon of plate tectonics and continental drift has transformed the field of geology in the past fifty years. When I was young, it was a new theory. But continental drift is measurable today. Moreover, given the measurements and the current shape of continents, one can speculate that, in the distant past, at periods determined by measurements made using modern physics and chemistry, which allow us to model the dynamics of the crust and the mantle of Earth, the currently existing continents were fused together, apparently several times, in a supercontinent. This theory makes predictions, most notably that—like the chromosomes—one will find identical geological structures at the edges of the current continents that were once fused. Guess what has been observed?

Finally, let’s consider the particles, called neutrinos, coming from the Sun—one of the great astrophysical observations of the past century. It established directly a fact that is at the basis of stellar astronomy, that the Sun’s power arises from nuclear-fusion reactions at its center. The neutrinos interact so weakly that they make it out of the Sun unimpeded after they are produced. If our ideas about the Sun’s power source are correct, each second of each day, six hundred billion neutrinos are going through each square centimetre of your body, originating from the Sun.

The Nobel Prize-winning observation of solar neutrinos—made by Ray Davis and his colleagues over a twenty-year period, starting in the nineteen-sixties—was performed using a mammoth tank of cleaning fluid located deep in a mine in South Dakota. A deep mine was required to shield the detector from all the other cosmic rays that bombard Earth’s surface. Cleaning fluid was a cheap source of chlorine, and calculations suggested that, of the billions and billions of neutrinos going through the detector each day, one, on average, would interact with an atom of chlorine and change it into an atom of argon. So the task was to detect a few atoms of argon in a hundred thousand gallons of cleaning fluid. The experimenters succeeded, and their results have been validated by many other experiments since then. This has established that our detailed model of the Sun—which determines other aspects of its structure measured in independent ways, such as by techniques like seismological observations of the solar surface—is, essentially, correct.

But there’s the rub. The model uses the very same physics that we test with the neutrino data, which probes the nature of the very dense core of the Sun where the neutrinos are produced. It also implies, however, that it takes almost a million years for light to get from the center of the Sun, where the energy is generated in the nuclear reactions, to the outside, as it is continually scattered to and fro by the dense material in between, and before it escapes for us to see.

Thus, when we feel the warmth of the light from the Sun on a warm day in the summer, we are doing historical science. And, if the Sun were only six thousand years old, it wouldn’t be shining as it is while I sit here and write this in Phoenix. Nor would it be shining in Petersburg Kentucky, on the Creation Museum and Ken Ham.

Lawrence M. Krauss is the director of the Origins Project at Arizona State University. His most recent book is “A Universe from Nothing: Why There Is Something Rather Than Nothing.”

Above: Ken Ham poses with one an animatronic dinosaur during a tour of the Creation Museum; May 24, 2007. Photograph by Ed Reinke/AP