 Hello everyone. Today I will be talking about the ways and means on how we study the physical world. But first we are going to define in today's context what we mean by physical world. So physical world consists of the things that manifest through our five senses, like for instance trees. We can see them, we can feel them, we can touch them, you can taste them if you want. Music, you can hear it. Our galaxy, we can see them. Or rainbows perhaps. And it also includes the things that we cannot readily observe. And usually these things manifest their existence indirectly through our use of detectors. I'm talking about things like electrons or the subatomic particles that we know, the other subatomic particles. Microwave, ultrasound. We know that these things exist because of the many ways that we detect them. The many ways that we use them. We use electrons, we use ultrasound, we use microwave in our daily activities. That means that we already have the means to detect, control and manipulate them. So this is the physical world that we mean, observable or not. As long as they are a compulsive matter or they have energy then they belong to our physical world. So how do we proceed? So to give you an idea on how we go about in studying physical world, I'm going to give a very simple example. For instance, how are rainbows created? We want to know. We want to understand how rainbows are created at least in our atmosphere. So where do we start? Well, initial clues are drawn from our experience, our observations. Or sometimes we draw also from our a priori knowledge about the event. So what do we know about the rainbows at first glance? Well, about their shape. They always manifest themselves a circular arc over the horizon. In terms of colors they always appear in the same arrangement of colors. Red, orange, yellow, green, blue indigo violet depending on your reference literature. Sometimes the indigo is removed from the colors. What else do we know? What else do we have as initial clues? We also know that they always appear at the same location relative to the ground. Something like 43 degrees with respect to the horizon. And another clue is that we always see them in pairs. The primary one is more intense. But there is always a secondary one. A little bit higher than the primary rainbow. And it is less intense. That's why most people don't notice the presence of the secondary rainbow. So you have these clues. But you cannot still answer the question how are rainbows created. But you have clues. And of course you may as well observe that rainbows usually appear right after rain on a relatively sunny day. And so perhaps you hypothesize that water droplets may have something to do with the production or the creation of rainbows. And since they appear during a relatively sunny day, then maybe perhaps the sun also as the source of light has something to do with rainbow. And of course the best way to study rainbows is your ability to create them by yourselves. So in this instance the importance of a laboratory cannot be under stated. If you can only produce rainbows in your laboratory so that we can study further within the confines of your own laboratory within the comfort of your laboratory then you can proceed faster. And whatever theory that you will arrive at in the end to be able to explain the existence or the creation of rainbows they must explain. Your theory must be able to explain all the initial clues that we already presented. The color, the shape the exact location with respect to the horizon. The presence of the secondary rainbow which has a reverse order of colors by the way if the primary rainbow is roigibib the secondary rainbow is your reverse in order. So your theory should be able to explain all these observables. But then you might also need further clues from sometimes seemingly unrelated observations. You cannot explain of course I am talking with the benefit of hindsight because I already know how rainbows are created. You cannot explain how rainbows are created without invoking certain properties of light. And these properties of light have been studied centuries before us. In fact we owe the arrangement of color to the pioneering study conducted by Newton. Newton observed that when you pass light the visible light through a prism the light bends and some colors bend more than other colors. That's why they don't bend at the same angle. Some are less bent and some are more bent. So that gives us the arrangement of colors. So you have to draw from the results of that experiment. So suppose you know these things and to piece them together it takes creativity to put these things together to tie these things up to make them part of a single puzzle. It takes creativity. That's why we also say that science is a creative human endeavor. So upon tying these things up you now have a very good picture on how rainbows are created. You now have a theory. And your theory as far as you are concerned because you were able to explain all the observations to account for all of those clues that we have encountered in the actual rainbow or in the simulated rainbow in your laboratory then you have a reason to believe your theory. And these theories, theories like this this make up the science that we know. And after you have put all these things together you now come up with probably a statement with of course at most confidence on how rainbows are created. This is what we call a theory. And theories like this is what builds science. Science is not only a way of knowing the process that we undertake towards knowing but it is also about the results. The results of our investigation. The results of our seeking for answers. And these results is of course these results are embodied on a theory. We say that we study physical world through science, not only enumerating the observables but also being able to fix on certain laws that govern the existence of things and of course being able to explain the characteristics, the observables and all the clues. In science there is always this underlying faith in the existence of rationality. We say that nature or parts of nature follow an orderly and predictable patterns governed by fixed laws. Ever since we took away as the main cause, divine intervention or the winds of the gods like why is there a storm? Because might say because the gods wield its soul maybe we did something bad and the gods are punishing us. Ever since we abandoned that paradigm, we abandoned that thinking that belief that is the true start or the true birth of science as a way of knowing. So we always have this underlying faith that things can be explained in a logical or rational manner that all phenomena behave in a rational manner. There is also another underlying faith in its simplicity. We assume that these laws are simple enough for man to be able to discover and at the same time comprehend. Simplicity by the way is one virtue of a good theory. If a theory can explain a certain phenomenon but it is made up of a lot of assumptions of a lot of adjustable parameters then it's not a good theory because it's a very complicated theory. In science there is more probability that a theory is correct when it is a lot simpler than a competing theory. May I warn you about the use of the word correct in here? When I say correct it's not a permanent thing. It may be correct up to this point in time only because we can never tell when somebody can make an observation that cannot be explained by this quote-unquote correct theory. So we studied the physical world through science starting from the days of Aristotle. Aristotle gave us a very simple science around 300 BCE. The main characteristic of that science is the simplicity of its theory. Remember only four elements in the whole world. The fifth element does not reside in our world. It resides up there. It's called the quintessence. Perfection. It's the fifth element. From the Aristotelian time to modern science around 1700 BCE or common era. The only addition to the simplicity of theory is our use of experimental verifications. So the characteristic of science during Aristotelian time is simplicity while the characteristics of modern science from 1700s up to our time is simplicity plus experiments. Science is as I said a while ago a creative human enterprise. We have been taught since we were kids in our primary years that science proceeds in a well-defined recipe, if you may, called the scientific method. And in scientific method you start with a question, a curiosity or a problem and then you make a guess. This guess is what we call technically as hypothesis. So you list down all probable answers as many as you can. And then you start observing. You start conducting your experiments. Through your experiments one by one you eliminate the hypothesis until only a single one remains. And then at the end you say that this is the most probable reason or this is the most probable answer. That is the scientific method. But in truth very rarely do we investigate using the scientific method. Most of the scientific revolutions that we have going back to the years of modern, the so-called modern scientists actually were products of chance, intuition, insights, trial and error. It's a quantum leap. Sometimes from a logical deduction to that crucial intuition there's nothing in between. There is no way of explaining how this particular scientist arrived from point A to point B. Such is the case of war's hydrogen atom when explained why the hydrogen atom is very stable. Nobody can provide a proof that would lead to those quantization of orbits. So some authors call it a misconception whenever we attribute a scientific method to every scientific inquiry and as I have said actually most of the things that we know today are products of things other than the scientific method. But it is true it is always true that science progresses through two things. The use of mathematics and the use of experiments. So we ask ourselves what makes a good theory? A good theory should be simple. It must have very few adjustable parameters or the use of constants that we insert in those terms so that it will give a number that is in agreement with the observed or measured number from experiments. The simple parameters that you have the better the theory is and of course it must be able to explain all the past and current observations and at the same time it has the ability to predict what happens when certain conditions are not met, when certain conditions are changed. So science has this predictive capability. And according to the philosopher of science Karl Popper the most important attribute of a good theory is that it must allow for falsification. It should be falsifiable. There should be a clear cut experimental design that could result in things that would falsify the theory. If it doesn't allow for falsification then it's an overly encompassing theory. There is no way to know if it is wrong because it is never if it is right because it is never wrong. So theory and mathematics on the other hand this is both a blessing and a bane. It is a blessing because when science with the theory and that theory is expressed in its ultimate form using the language of mathematics we are able to summarize everything into a single mathematical sentence most of the time. For instance Faraday's law in electromagnetism when Faraday completed his series of experiments he summarizes observations and results and conclusions. He was able to come up with two volumes of books this thick and it doesn't contain a single equation because Faraday was not that much adept in mathematics and Maxwell summarized those two volume books of Faraday in a single equation. So mathematics makes the presentation of theories more simple and more elegant and at the same time if you know how to manipulate mathematics if you know how to do mathematics then you have a way of predicting what will happen to a certain variable when certain parameters are changed and there is your predictive capability. I said it is also a bane it is also a curse because ever since science adapted the use of mathematics as its main language science became so very difficult to some people who have this natural aversion of mathematics. In fact studies show that what makes science difficult is not the science because the concepts of science are very very simple, easy to understand that's what good theories are but it's the language that it uses the mathematics that it uses so it's a blessing and a curse the use of mathematics. Theory and experiment so what is the use of experiment aside from providing a chance to falsify a theory so experiments are used actually in order for us to gain more observables measure quantities gain clues gather clues in order for us to develop a very good theory and when the theory is made when the theory is done because it has this predictive capacity then we also design experiments that might falsify the theory if there is no experiment that can falsify the theory then as we have learned a while ago the theory is no good if it doesn't allow for falsification so if you take a look at Einstein's general theory of relativity it's actually provided in its claim that light is affected by gravity it provided an opportunity for an experiment to disprove him and that's what Sir Arthur Eddington did he went to Africa to conduct an experiment that would in all probability falsify Einstein's general theory of relativity well as it turned out what Eddington measured was in agreement with what Einstein predicted and so that was the start when we started embracing the general theory of relativity with the of Einstein because a landmark experiment agreed with what the theory predicted so that's how important experiments are they validate the theory but also they falsify the theory experiments however cannot prove a theory even if you already have conducted a million experiments and they all agreed to the theory a single experiment that does not agree with the theory makes the theory no longer viable no longer correct in our sense of correctness just a single experiment can do that so the main purpose therefore of experiment is simply falsification slash validation but never improving the theory so we therefore say that theories are accepted until such time that a particular observation comes along that does not agree with the theory and it is time to look for a better theory it doesn't necessarily mean that the theory is wrong if you compare Newtonian mechanics with Einstein's relativity theory actually Einstein did not prove Newtonian mechanics what the relativity theory did to mechanics is that it just relegated it into a limited applicability we now know that for very fast motion we can no longer use Newtonian laws if we are expecting accuracy or precision we have to use the relativistic mechanics according to Einstein we now know that for very very small particles we can no longer use Newtonian laws we have to use the laws resulting from quantum mechanics but I repeat this do not mean that Newtonian laws are wrong because for all practical purposes as far as we are concerned based on our daily experience we are not living in subatomic world we do not experience speed close to the speed of light we are very slow and very big particles therefore as far as we are concerned Newtonian mechanics is still a correct theory what about technology what is the contribution of technology to science it's actually a two way relationship most technology that we know are based from understanding provided by science the ability to manipulate to tamper with, to control to troubleshoot a certain phenomenon that ability is given to us by science which provided us the basic understanding of that phenomenon and so we have this technology for example the technology of electron microscopy that technology was only made possible when we understood the nature of electrons when we understood how to produce electrons with different energies when we understood that electrons behave like waves sometimes as all matter do they behave as particle but sometimes they behave as wave the so called wave particle duality so our creativity our ingenious ability for design allow us to come up with this electron microscope and what that does the electron microscope do as far as scientific progress is concerned it allows us better degree of visualization imaging we can now study insects very small insects bacteria, cells and so on so this added capability provided by technology gives back to science a certain crucial steps towards further progress and because of the nature of our physical world from the very small to the very big from the very slow to the very fast in the process of studying our physical world we came up with several branches of science that we know today from the sub atomic domain which is of course the domain of the particle physicists we call it particle physics to the study of the nucleus the nuclear physics and to the largest dimension that we know probably the radius or the diameter of the known universe that is the discipline of cosmologists geology the study of the earth or we can extend its definition to the study of other planets chemistry of molecules biology also of cells of life forms and so on all of these branches arose from our single of the physical world but since there are so many things to study we begin to allocate or apportion these lots of things into several branches of science now in its faith in simplicity the ultimate goal of science is the search for unity the search for the theory that could explain everything the search for the theory that could explain gravitation and electromagnetism at the same time in a single equation the search for a theory that could explain black holes and the shape of chicken eggs and that is the holy grail of science most people believe that that theory exists that we can succeed in looking for that theory that's so called the theory of everything and there's no telling if ever we will come to that point and thank you that's how we study the physical world