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  • Kevin

The Hourglass Puzzle: A Parable

Updated: Jun 27, 2020

Andrew was no ordinary student. He was a critical thinker and often thought outside-the-box. Likewise, Dr. Origins was no ordinary geology professor. As a geologist at a Christian university, he can conduct research and experiments like any other geologist, but he often disagreed with his secular colleagues concerning the past. He spoke of two different kinds of science: observational science and historical science. Now, you might ask, what is observational science, and what is historical science? Well let me tell you a short story about the hourglass puzzle.

For the first day of class every year, Dr. Origins would conduct a little puzzle/competition with his students. This year was no ordinary year though because he had Andrew in his class. Dr. Origins began with the usual administrative introductions, and then began to explain the puzzle.

“As you can see in this laboratory classroom, we intend to conduct lots of experiments. Yes, we will be analyzing elements and compounds in rocks, experimenting with chemical reactions, and the like. But before we dig in to the meat and potatoes of this class, it is critically important that we understand the nature of science from a philosophical perspective. Therefore, we are going to have a little competition to solve a puzzle. Underneath this veil is a large hourglass that is in the process of letting sand fall from the top to the bottom. The objective of the puzzle is to determine when this hourglass was turned over. Here are the rules:

  • There will only be two competitors

  • They cannot work together

  • They cannot disturb the hourglass

  • They have a time limit of 20 minutes

  • They cannot simply ask me for the answer, of course

Now, I will give you just one hint. Under its present, normal conditions, this hourglass does not take one hour to empty from top to bottom…it takes much longer than that. Okay, who would like to enter the competition?”

Andrew and another student named Charlie rose their hands immediately. “Okay, Andrew and Charlie it is. Come on up. Your time starts…now!”

Charlie scrambles throughout the lab and opens up multiple drawers to find measuring devices. He finds rulers, measuring tape, and so forth, but decides that those objects are useless. He returns those items and then decides to start taking a series of photographs with his smartphone. As he’s taking pictures, he’s jotting down some notes and transferring photographs to his tablet.

Andrew on the other hand, inquisitively stares at the hourglass for about five minutes and does nothing else. Then he asks Dr. Origins, “Sir, may I exit the room for a moment.” “Yes Andrew you may.” Andrew exits the room and then returns about five minutes later and simply sits back down in his seat and jots down some notes. The whole class stares at him in astonishment.

Meanwhile, Charlie is still working fervently on his tablet…analyzing photographs, writing notes, and conducting calculations. Finally, the 20 minutes are up, and Dr. Origins calls the students to the front of the room.

“Okay Charlie, let’s start with you. First, explain to me your methodology, and then tell me your answer. As long as your answer is within plus or minus 10 minutes, that’s good enough for me.”

Charlie confidently replied. “I took a series of photographs and used image processing techniques to determine the current ratio of sand in the top and bottom chambers, as well as the rate of change of that ratio. Using these two pieces of information, I extrapolated backwards and determined that the hourglass must have been turned over four hours ago at 11:00 AM.”

“That was a very clever approach Charlie. You recognized that the sand falls from top to bottom at a certain rate, and you were able to calculate that rate. Moreover, you found a way to observe and calculate the ratio of sand in both chambers, which is not an easy task unless the hourglass chambers had volume labels. You conducted excellent observational science. Unfortunately, your answer is incorrect because there is a flaw in your approach which we will discuss in a moment. Andrew, what did you do?”

Andrew pulled out his notes and began to address both Dr. Origins and his fellow students. “At first, I considered Charlie’s method, but I realized that his method is inherently flawed. Charlie’s method is based on many assumptions about the past few hours, all of which are falsifiable. For example, I don’t know whether or not you, Dr. Origins, flipped the hourglass upside down a second time while it was already running. I don’t know whether or not you added or subtracted any sand from the top or bottom chambers. Furthermore, I don’t know if you tilted the hourglass at some point, resulting in a different rate of fall for the sand. I decided that the only way to know for sure was to find a reliable witness. Although you established a rule that we could not ask you for the answer, you did not say that we couldn’t ask somebody else for the answer. Therefore, I just walked across the hall and found the history professor, Dr. Shish Kabob. I said to him, ‘Sir, did you happen to see what time Dr. Origins turned over that large hourglass across the hall?’ He then said ‘Why yes Andrew, I did. Dr. Origins turned the hourglass over about two hours ago at 1:00 PM.’ He also said that I was the first student in ten years to walk across the hall and ask him that question. So that’s all I did…I found a reliable witness.”

Dr. Origins smiled very big. “That is absolutely outstanding Andrew! Yes, you are in fact the first student to get it right in the ten years that I’ve been doing this puzzle! Students, do you see the lesson here? Charlie used observational science to quantify both the ratio and the change in ratio of sand in the top and bottom of the hourglass, and he used that information to extrapolate backwards based on the assumption of unchanging conditions. This is a common philosophical approach called “uniformitarianism.” This approach has its limitations, because it relies on many falsifiable assumptions about the past. By the way, I did in fact manually remove sand from the top and add it to the bottom, after I turned the hourglass over. This distorted the apparent time that I turned over the hourglass. Despite my earlier actions, Andrew was still able to determine the correct answer because he recognized that any assumptions about the past could be wrong. He considered the type of science called “historical science,” which is not always verifiable because it cannot be tested or repeated. In fact, the only way to truly verify something about the past is to find a reliable witness.”

Dr. Origins motioned for Andrew and Charlie to take their seats. He paused for a moment, and then delivered a stunning conclusion to the matter by explaining the application of the hourglass puzzle. “Most geologists claim that the earth is billions of years old, and they justify their claims with various methods of radiometric dating. However, radiometric dating is often based on unverifiable and falsifiable assumptions about the past, just like Charlie’s method with the hourglass. Other geologists recognize this conundrum and consider the words of a reliable witness as their starting point, just like Andrew’s method with the hourglass. In regards to the age of the Earth, we have the most reliable witness: God. God told us in His Word that He created the earth about 6,000 years ago (based on the genealogies), and He also told us about a global catastrophic flood that occurred only 4,300 years ago. Considering these historical events is critically important when we examine rock layers, fossils, and even radioisotopes. Therefore, when we consider the “hourglass” of the Earth, we must account for these historical events in our calculations and scientific models concerning the past.”

If you would like to learn more about observational science versus historical science in regards to radiometric dating, I recommend the the following short video clip:


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