1. About science

What is science?

Science is the systematic pursuit and organization of knowledge that comes about through asking questions, making careful observations, and carrying out controlled experiments about how the universe works. Science has helped us answer questions as diverse as: how large is our planet? How old is the universe? What are the fundamental building blocks of matter?

The scientific method is the process by which scientists come to answer questions about the universe. It all starts with asking a question. What is light? What elements make up stars? How far away is the nearest galaxy to ours?

Science does a really great job answering questions we have that ask: “What…?” and “How…?” For example, how big is our planet? That is a question we can use the scientific method to solve. What is all matter made of? That is another question we can investigate using scientific principles.

Unfortunately, science is not always well suited to answering questions that ask: “Why…?” Why does our universe exist? Why do humans have consciousness? These are really great questions. Science may help us inch closer to an answer, but likely will not be able to provide any definitive answers. In these cases, philosophy and religion can help us to interpret and understand these deep questions.

Science is best used to answer questions that can be tested and validated experimentally. Consider the statement, “the Earth has a mass of kilograms.” That statement is only a hypothesis until it is experimentally validated by other scientists. If this hypothesis is verified by many other scientists, then it becomes a fact.

Experiments that seem to disprove a well-known fact can lead to revolutions in our understanding of the physical world. Up until about the late 19th century, it was commonly accepted that light was a wave. All of our observations and experiments verified that light acted exactly like a wave. At this time, scientists realized that the photoelectric effect, which had been observed for many decades, led to some conclusions that could only be explained if light also acts like a particle! This discovery helped usher along the newly formed quantum physics, and has led to technology such as light sensing photomultiplier tubes and some of the sensors used in digital cameras and night vision goggles.

However, experiments must be repeatable and verified by more than one scientist. Experimental errors, or misunderstandings of experimental results, can lead to setbacks in science. Whether these mistakes are malicious or not, scientists must remain skeptical of experimental evidence until it is verified by others.

From all of this, we can conclude that scientists must be not only open-minded and curious, but also exhibit healthy skepticism and fastidiousness!

Scientific terminology

One thing you may notice in the physical sciences is the use of proper scientific terminology. It is important to convey information in such a way that multiple readers can come to the same correct interpretation and understanding of a concept. This is important not only in the physical sciences, but in engineering and technology fields as well.

Sometimes you may find that there is a disconnect between the colloquial or casual use of a term, and the physics use of a term. This textbook will aim to point out these cases when they occur and give you a note of caution in using these terms in a classroom setting!

A hypothesis is a descriptive statement about how the world works, based on observations. In order for a statement to be a scientific hypothesis, there has to be a way to prove the statement wrong. This hypothesis can be tested to determine whether or not it is valid. An example of a hypothesis would be: “The Sun is more massive than the Earth.” Any scientist can devise an experiment to test whether or not this hypothesis is true. If shown to be untrue, this hypothesis is discarded and a new one formulated to explain an observation or experimental result.

A scientific theory uses well-tested hypotheses as an explanation of how the universe works and is supported by multiple, repeated experiments. A good theory makes predictions that can be verified as true or false by experiment. If a theory offers no predictions that can be proven or disproven by experimental observations, then we have no way to determine whether or not it is valid.

There are many theories that explain our physical world. Plate tectonics, general relativity, and quantum mechanics are just three examples. These three theories have held up to much scientific rigor and scrutiny over many years. We may revise and edit theories as we learn more about the universe. Often an individual or a group of individuals dismiss them as “just a theory” (see Figure 1.1 for a humorous example), which discounts the vast amount of evidence that points to their accuracy. However, in doing so, the individual is generally confusing the term “theory” with “hypothesis”.

A scientific law is a statement that describes relationships among the quantities that we observe or measure. These laws can be used to predict the behavior of objects. Many times, laws use mathematical equations to explain and quantify these behaviors and phenomena.

Newton’s law of universal gravitation explains the motion of objects such as planets, stars, and satellites. We use an equation to quantify the degree of gravitational attraction between different objects: for example, to determine the gravitational force between yourself and the planet Earth.

The scientific method

How do we actually do science? How can we go from an observation to an understanding of how the universe works?

The scientific method that you may have learned about in school is usually presented as a straightforward set of tasks that, when completed, will result in an updated understanding of our physical world. That is not always the case!

Regardless of the set of steps we go through in our pursuit of science, the scientific method always starts with a question, or an observation that leads to a question. Why is the sky blue? What is an atom made of? How fast is light?

After asking our question, we then conduct background research. Has this question already been answered? If so, do we agree with the results? If the question has not already been answered, are other scientists working on answering this question? If not, are there similar questions that have been asked that might give us an idea of how to formulate a hypothesis or conduct an experiment?

Then we form a hypothesis. This can be an educated guess, or a more reasoned statement that attempts to answer our question. Our hypothesis should be testable using experimental methods. We may find ourselves reformulating or revising our hypothesis as we go through the next few steps in the scientific method.

Determining how to test a hypothesis can be a challenge. Some experiments may be simple and straightforward to conduct. Others may require expensive equipment or a specialized research laboratory to conduct.

Once the experimental setup and testing has been devised, we then conduct the experiment. This may require collaboration with other scientists. For example: a scientist may have a hypothesis that can be tested by using a particle collider, say, the one at Argonne National Laboratory, or at CERN.

After performing the experiment, the data that was generated by the experiment must be analyzed. If we’re lucky, the data points to a clear conclusion that supports our hypothesis. Sometimes the data may be vague or unclear, which may require us to modify the experiment to collect more data. Maybe the data disproves our hypothesis! Some very important experiments have disproved incorrect scientific hypotheses. Famously, the Michaelson-Morley experiment in 1887 disproved the existence of some type of medium that permeates through all of space. We now know that light does not require a medium to propagate.

What if, instead of having clear data after our experiment, we got weird results instead? We need to determine if we made an experimental error, or if perhaps there was a problem with our hypothesis. We troubleshoot the problem – sometimes by conducting additional research – and then either reformulate the hypothesis, or create a new experiment to gather more data.

After we’ve completed our experiment, we communicate our results to the scientific community. Frequently this will be through a peer-reviewed scientific publication. Peer review means that other scientists in our field read through our work to double check our experimental procedures and data analysis. We may also decide to present our work to others at scientific conferences. These conferences can lead to new questions being asked, and collaborations formed to help answer them!

Once we’ve concluded our experiment, we can create technology based on our results. This does not always happen right away; sometimes it may take years to create technology based on scientific results.

Many times, the introduction of a new technology may generate new problems that require solutions using the scientific method. The internal-combustion engine is a wonderful technology, but it leads to greenhouse gas emissions. Nuclear power provides lots of energy to our homes, but generates hazardous waste. Even technologies such as computers, smart phones, and the Internet have led to issues involving the widespread propagation of misinformation and disinformation.

Sometimes, our knowledge of the universe is expanded upon by observations that occur serendipitously or by accident. For example: Penicillin was first discovered when a scientist’s research was left out, causing mold to grow. It was discovered that this mold was capable of killing bacteria. Through the use of the scientific method, and the collaboration and communication between many scientists, the life-saving antibiotic drug was developed.

Science and technology

Science, as mentioned, is the pursuit of knowledge about how the universe works. Physics is a branch of science that focuses on the fundamentals of the workings of our universe. While physics sometimes overlaps with other fields, such as chemistry, biology, and even mathematics and materials science, we consider physics to be the fundamental science, as it provides a foundation for the other sciences.

Two contributors to this textbook, Dr. David R. Fazzini and Dr. Carley Bennett, are physicists. They received their Ph.D. degrees in physics. Much of Dr. Fazzini’s research was conducted at Brookhaven National Laboratory and focused on condensed matter physics. Dr. Bennett’s high energy physics research was conducted at the Large Hadron Collider and focused on dark energy.

Engineering (in contrast to physics) is the application of the science that is generated in physics, chemistry, biology, and other fields into the creation of new technology.

One of the authors of this textbook, Dr. Alyssa J. Pasquale, has a Ph.D. degree in electrical engineering. She is an engineer. This means that she learned about physics, especially electricity and magnetism. This is science: explaining how the universe works, specifically as it pertains to electricity and electronics. She also took a lot of math classes such as calculus and differential equations to quantify those topics. In addition, she learned about and focused on the application of those scientific and mathematical principles to solving problems and creating new technology.

When you think about technology, what is the first thing that comes to mind? Computers? Electric vehicles? Spaceships and satellites? Those are all great examples of technology. Technology is what we get when we use scientific principles to solve problems. There are a lot of examples of technologies all around us: some of them are more high tech than others. Everything from the homes we live in, to the clothes we wear, to things as mundane as pencils and paper are technology. Over time, technologies improve as we learn more about the science behind them.

At times, science very quickly leads to technological innovations. Semiconductors were found to emit light, and this led to the invention of the light-emitting diode, or LED. These days, LED lighting has become affordable and practical enough for most of us to have LED lighting in our homes, flashlights, and even smartphones.

Other times, science may take years or even decades to evolve into practical technology. It took several decades between Einstein’s formulation of the theory of relativity and a technology that uses it: GPS. General relativity is required to coordinate the timing between moving satellites and the humans on the Earth’s surface who use them to accurately determine their position on the planet.

The scientific mind

There are many traits that a good scientist should possess. First and foremost: a scientist should be curious! Many people in science and engineering fields have been excited about learning how and why things work. This drive to learn more about the universe helps us to come up with new questions to solve, and new techniques that we can use to solve them.

Scientists should also be open-minded about how the universe works. One of the difficulties in teaching a physics class is that many students come to the class with many misconceptions about physics. And that’s okay, you’re still learning! However, be prepared to learn that the universe may work differently from how you currently think it does. It’s possible that you just don’t have all of the information you need to understand the full picture of how our universe works. This happens all the time in science!

On the other hand, a good scientist remains skeptical of scientific data until it has been held up to rigorous experimentation and scrutiny. You should trust, but verify, that information is correct. Hold things to a high standard of rigor. Do not believe what people in authority tell you just because they are in a position of authority: demand experimental validation and verification!

Scientists should also have integrity. They should not falsify their experimental data or observations. They repeat their experiments to confirm that they are reproducible. Good scientists should never mislead people about their discoveries or their impacts. Unfortunately, there have been many scientists throughout history who have purposefully misled the public about their results, who have plagiarized the work of others, or who have fabricated information to boost their careers.

Not only should scientists be careful in how they present their data, they should also think through the possible repercussions of their work. Being able to split the atom was an outstanding scientific innovation, but it also led to the creation of atomic bombs. It is irresponsible to society to disconnect science from its possible uses and outcomes.

When people misuse scientific phrases and terminology – usually to mislead others into purchasing a product that sounds “high tech” – we call this pseudoscience. This is scientific-sounding jargon that is usually meant to get you to part with your money to purchase something that has not been verified to work using the scientific method. Or, pseudoscience can relate to an idea about how the world works. Unfortunately, there are individuals and companies that exploit people who lack the scientific literacy to see through their claims.

To identify pseudoscience, ask a few questions: Does the idea or product make use of vague, exaggerated, or unverifiable claims? Is the data behind the idea or product open and has it been tested by other scientists? Does the idea or product ignore compelling scientific evidence? Does the person or people behind the idea or product attempt to suppress others who dissent or show evidence to the contrary?

For example, astrology, the belief that we can make predictions about our lives based on the positions and movements of planets and other celestial bodies, has no basis in science. No evidence has been found to support astrology, and all falsifiable predictions made with astrological methods have been falsified using the scientific method.

Unfortunately, there are many areas of pseudoscience in areas ranging from physics to medicine, history, and psychology and sociology. At best, these products and ideas cost us money. At worst, they are harmful, toxic, perpetuate racism, and cause other societal problems.

The mathematics of physics

In physics, we frequently need to quantify our discussions of physical phenomena. This means we want to be able to express different values numerically. We use math to put numbers to our discussions.

Each physical quantity that we discuss will have a symbol associated with it. Every time we learn something new, that symbol will be defined so that you know what it means. For example: mass has a symbol of the lowercase letter . Temperature has a symbol of the capital letter .

Sometimes the symbols use the English alphabet. Sometimes they will use Greek letters. For example, the concept of wavelength tells us the distance between two identical points on a wave. The symbol for wavelength is the lowercase Greek letter lambda ().

Many quantities just convey a numerical quantity: a value or a strength. We call these quantities scalars. Sometimes a quantity needs to express both a strength and a direction. These quantities are known as vectors. Vectors have an arrow above the symbol (example: ), or are expressed using a bold font (example: ).

All this is to say that understanding that symbols relate to actual physical quantities is important. Different physical quantities relate to each other by means of mathematical equations. These equations are frequently derived from a physical law, for example, Newton’s laws of motion. We will learn about each equation as it is defined in this textbook, and what that equation tells us about the physical world.

Sometimes we may find that a few physical quantities use the same symbol. Specific heat capacity is defined by the lowercase letter c. But so is the speed of light! Capital V can stand for either volume or voltage. How do we know which is which? The same way we learned the meaning of the word “bat.” Does that refer to the animal? Or does that refer to the stick you use to hit a baseball? It all depends on context. When we see a symbol in an equation, we look at the other symbols nearby to help us determine the meaning, just as we read other words in a sentence to determine the meaning of the word “bat.”

If all of this seems overwhelming right now, that’s okay. Just as you did not learn to speak or read the English language overnight, learning the mathematics of physics is also a process. Be patient with yourself, but also know that all things improve with practice.

One last thing – all of the physical quantities we use in this textbook are not only defined by a symbol, but also have units that we use to express those values. One great example is temperature. Temperature has a symbol of the capital letter T. But if you are told that the temperature is 10, that’s not enough information to determine what to wear when you go outside. You also need to know the units (in that example: Celsius or Fahrenheit).

In physics, we will use SI units, known as the international system of units. These units are internationally used in physics and engineering. They differ from the English units you may be used to. We use meters as the SI unit of distance, not feet or inches. We use kilograms as the SI unit of mass, not pounds or slugs. Whenever possible, this textbook will attempt to give you some context for these units, as they may be new for you.

Why are units important? Just as scientists need to use precision in our language and terminology, so do we need to use precision in our quantities. It would be inconvenient to be told that it’s 10 degrees outside, so you decide to put on several layers of sweaters and jackets, only to realize that it’s 10 degrees Celsius outside, not 10 degrees Fahrenheit! That example may not be a big deal, but incorrect units used in dosing medication or medical therapies could have a fatal outcome. In 1999, an orbiter was sent to Mars. Rather than landing on the surface, it crashed, creating a very expensive crater on the surface of the red planet. The crash occurred because some of the team members used English units (pounds), while other members used SI units (newtons). Units matter! Get into the habit of using units all the time in your practice.

Practice questions

Conceptual comprehension

1. What is the difference between a scientific theory and a law?
2. Einstein’s theory of gravity (commonly known as general relativity), formulated in the early 20th century, found some conceptual flaws with Newton’s law of universal gravitation. Does this mean that Newton’s law of universal gravitation is wrong and should be discarded? Why or why not?