Physics is the study of the physical laws that govern the universe—from the smallest subatomic particles up to clusters of galaxies and distances of billions of light-years. All other sciences rest on the foundation of physics. For example, biology studies the application of the laws of chemistry to the complex molecules that make up living cells. But the laws of chemistry are themselves an application of the laws of physics to different kinds of atoms interacting with each other. Understanding physics allows us to understand the world we live in as well as create new technologies, and thereby shape our environment more effectively.

In the novel, Danielle recognizes this at age four, when she realizes that everyday reality is made of “machines within machines within machines.” This inspires her to study physics, where she later comes up with her “n-dimensional membrane” theory to describe the smallest scales of the universe, and wins a Nobel Prize at fifteen for her “hidden gear” experiment about uncertainty in quantum physics. But accomplishments such as this aren’t just for fictional superheroines. The tools exist today to conduct serious science experiments at a young age.

The first step to become a physicist, or any type of scientist, is getting inspired. Great physicists are motivated by a passion for learning about how the universe works. Many have described the way these rules work as elegant and beautiful, and inspiring awe. Let some of these great minds share with you their inspiration:

• Nobel laureate Murray Gell-Mann¹ on the beauty of physics, and the wonder he still experiences from unlocking its mysteries.
• Stephen Hawking,²  (1942 – 2018) one of the world’s most famous scientists, on the “big questions” that are still unanswered about the universe.
• University of Cambridge physicist Harry Cliff³ on a fascinating question: “Have we reached the end of physics?” Or is there still a lot left to discover?
• Renowned physicist and science author Brian Greene,⁴ pondering the question of whether there are multiple universes, and why the laws of physics are what they are.
• Footage from old TV documentaries with the late Richard Feynman,⁵ one of the greatest physicists of the 20th century, talking about why science can be so exciting and interesting, and why he finds doing physics his most enjoyable activity.
• Episode of the Vsauce series on YouTube, hosted by Michael Stevens,⁶ asking the sort of question young kids argue about on the playground: “What would happen if every single person on earth jumped at the same time?” It shows how you can apply scientific logic to all kinds of problems.
• Physics for Future Presidents,⁷ an excellent book by Richard A. Muller that explores intriguing and relevant questions in physics in accessible language.

If the physics classes at your school are not challenging enough, many community colleges allow younger students to enroll in courses if they can show that they’re ready for it. Other organizations in your community can also support and reward your physics study—for example, the Girl Guides⁸ and Girl Scouts⁹ are developing special merit badges to recognize achievements in science-related fields. The Boy Scouts¹⁰ have several badges for these areas, too.

Yet some people find that classroom education isn’t the best way for them to learn physics. It can be a big help to study at the times that are most convenient for you, when you can focus your full attention on the subject, and to work at your own pace. There is a wide range of websites and mobile apps you can use to help you improve your physics skills:

• Brain It On!¹¹ (Android). Lets you solve physics puzzles, and has you use games to get a better intuition for how the forces of physics work.
• Monster Physics¹² (iPhone). This one is aimed at younger kids, and encourages creative thinking to understand how things work. Create your own virtual machines from a range of parts, and watch how the parts work together.
• Pocket Physics¹³ (Android). Simple explanations for a wide range of concepts in physics, including illustrations. Good for all ages from primary school up to university.
• High School Physics – Free¹⁴ (Android). High school-level physics lessons, including problem-solving exercises and calculator functions.
• Physics Full Course¹⁵ (iPhone). An all-inclusive course with school-style lessons and exercises to practice your skills.
• Complete Physics¹⁶ (Android). Includes advanced physics over a wide range of topics, with quizzes to help you test your knowledge.
• Physics Classroom ¹⁷ (Web). Website with lots of different exercises and simulations to see the forces of physics in action.

If you’re looking for a more structured and intensive method of learning physics, online courses can be a great solution. These are taught by some of the best professors in the world, and many give you the option to work collaboratively and discuss the subject with fellow students or even to receive personalized feedback from instructors. Some of the best offerings in physics include:

• A Khan Academy course that provides an introduction to physics¹⁸ from the very beginning, and works up to more advanced concepts. Based on video lectures and animated demonstrations.
• A slightly more advanced course from Udemy,¹⁹ with more focus on learning problem-solving techniques. Includes about 1.5 hours of video lectures, with problems to solve in between.
• “How Things Work,”²⁰ a popular University of Virginia course available on Coursera. The course includes videos and graded assessments, and focuses on learning physics in the context of everyday objects. Takes about 11 hours to complete. After you finish, take a look at Coursera’s many other options²¹ in physics.
• Yale University offers open-access free online courses based on its college-level physics classes. The introductory physics course comes in Part I and Part II.²² In total, there are 49 lectures of about 75 minutes each, along with problem sets and quizzes. This is a good option for advanced physics students looking to stretch their knowledge and improve mastery of the subject.

If these courses excite you, and you feel a calling to become a physicist, you should give some thought to what aspects of physics seem most exciting. Broadly speaking, there are three kinds of physicists, divided by what role their work does in the context of science.

• Theoretical physics is concerned with figuring out what laws govern the universe, and coming up with theories that can explain the phenomena that scientists observe. Often, these theories are given in the form of mathematical equations. If the theory is correct, observations about the real world will follow those equations. The big challenge for theoretical physicists is coming up with equations that describe real life as accurately as possible, but in the simplest possible way. Theoretical physics requires a combination of creativity, persistence, logic, and abstract thinking. Probably the most famous example was Albert Einstein performing simple thought experiments which led him to devise his special Theory of Relativity. This theory resulted in unexpected and strange conclusions, including that the passage of time for you relative to another object would be affected by your speed relative to that other object. Einstein’s theory has been confirmed by countless experiments over the past century. In my book How to Create a Mind, I describe the simple thought experiments that Einstein performed to come up with his theory. These experiments required no equipment or resources other than a rich imagination and a willingness to “not fall off the horse”—meaning a willingness to stay with the implications of a thought experiment even if it led to apparently bizarre conclusions. These thought experiments require no substantial understanding of physics and very elementary math.
• Experimental physics is the work of testing physics theories in the real world and collecting data that can be used to create new theories. Experiments were how early scientists like Galileo, Isaac Newton, and Michael Faraday first figured out the laws of physics. Famous experiments were used to discover effects like electricity and radiation, which have countless practical applications in the modern world. Experimental physicists use the scientific method to attempt to find evidence that disproves a current theory, or demonstrates the existence of something previously unknown. Successful experiments involve coming up with novel ways of testing physical laws, and then carefully making sure that the experiment isn’t thrown off by unexpected factors. Thus, to be a good experimental physicist, you should work on improving your ingenuity, patience, and organization.
• Applied physics is the use of physics knowledge to solve real-world problems. Thus, it has a lot of crossover with inventing and engineering. The challenge of applied physics is figuring out how known theories can be used to make new technologies possible. Thus, it requires both understanding how physics works and imagining how those principles could be applied in innovative ways. To do this, applied physicists need to be good at “lateral thinking,” which is approaching problems from unexpected and original angles. They also need to develop good analysis skills—for looking at big, difficult problems and breaking them down into smaller, simpler problems that can be solved more easily. Applied physicists often have a “hacker” mentality, and get a thrill from figuring out how to do things that are seemingly impossible.

Hundreds of years ago, science was primitive enough that some people could master everything there was to know about physics. But now, so much has been learned already that people only have time to master a small part of it. So they specialize, which has become true of every area of science. Thus, physicists—whether theoretical, experimental, or applied—usually focus on one or two sub-fields within physics. Here are the main branches of physics, along with college-level online courses that can help you explore them more deeply to see if that’s where you’d like to specialize:

• Mechanics is the study of how objects behave when in motion or when forces are acting on them. Mechanics usually focuses on objects at the scale that we can see and interact with in everyday life. When people are trying to invent new machines or vehicles, they use mechanics to figure out how they will work. Mechanics can also be used in the creative arts—for example, people making video games or computer-animated movies use mechanics to make sure that the objects onscreen behave accurately and therefore look “convincing.” A course from the University of New South Wales in Australia²³ provides a solid introduction to mechanics.
• Quantum physics studies the tiniest scales of the universe, from individual atoms down to subatomic particles, and even smaller objects called strings that we can study through math but can’t observe directly. Unlike classical mechanics, where the interactions of objects can be perfectly modeled and predicted if you know all their properties, quantum physics features uncertainty. No matter how much information you have about a given subatomic particle, you can’t say for certain how it will behave—you can only talk about it in terms of probability. A major question in quantum physics is how the properties of particles at these tiny scales relate to the properties of larger objects. A course from the University of Maryland, College Park²⁴ lets you explore the basics of quantum physics and prepares you to go deeper. Danielle questions the probabilistic nature of quantum mechanics. She postulates a “hidden gear” mechanism that cannot be observed, but determines the outcome of quantum events. She gets a Nobel prize for conducting an experiment confirming this “gear,” but she discovers that the action of this mechanism is still indeterminate.
• Chemical physics focuses on the link between the most basic laws of nature and the chemical properties of atoms and molecules. Why is it, for example, that chemical bonds between atoms work the way they do? Why do certain molecular structures show some properties instead of others? This area of study can reveal the deeper mechanisms that drive large-scale chemical reactions such as what might occur in a chemistry class. This understanding can lead to creation of new materials and molecules that are useful in medicine, science, computing, and other fields. The University of Manchester has a highly-rated course²⁵ that will introduce you to the intersection between physics and chemistry.
• Electromagnetism is an area of physics central to most of the technologies we use today. Electricity, magnetism, radio waves, visible light, x-rays, microwaves (and other kinds of waves) are all effects of the electromagnetic force, which is one of the four fundamental forces of physics. A video from the SciShow with Hank Green²⁶ explains in more detail. Scientists who study this force uncover insights that may be helpful in areas like computing, communication technology, and sensor devices. An open MIT course²⁷ lets you get a better understanding of electromagnetism-related physics.
• Astrophysics is the branch of physics dedicated to planets, stars, galaxies, and the universe itself. Astrophysicists study how these heavenly bodies form, and how they evolve through their life cycles. They also study the origins of the universe itself, from the effects from conditions right after the Big Bang to what the universe might be like billions, or even trillions, of years from now. Other topics in astrophysics include research into the workings of exotic objects like black holes, neutron stars, and quasars. Astrophysics also investigates unusual concepts like dark matter, wormholes, time travel, and parallel universes. The University of Tokyo provides an excellent course²⁸ for beginners on astrophysics.
• Materials physics concerns how the basic laws of physics shape the properties of liquids and solids. It includes substances like crystals, and investigates why some molecules assemble into crystalline shapes and others do not. It also documents how matter behaves when it is transitioning between different phases, such as when liquid water freezes into ice. Materials physics opens opportunities for the creation of new materials and new technologies that make use of them. The National University of Science and Technology MISiS in Russia offers an informative course²⁹ on this.
• Mathematical physics is the development of new mathematical techniques for modeling physical phenomena, or for creating new theories. Often, ideas in pure math that at first don’t seem to have any practical applications are later discovered to be helpful in solving unexpected kinds of problems. A series of lectures by physicist Carl Bender at Washington University in St. Louis³⁰ is a very popular introduction to the techniques of mathematical physics.
• Particle physics is the branch of physics that covers how different kinds of subatomic particles behave, especially the 61 types of elementary particles that make up all known matter. It uses many ideas from quantum physics, but puts more emphasis on experiments, such as the Large Hadron Collider at CERN. These particle accelerators smash subatomic particles apart at incredibly high energies to study what they’re made of. The University of Geneva offers a rigorous course³¹ for people first getting into particle physics.

Finally, growing your skills and knowledge of physics requires hands-on experience of how these laws work. Since large-scale experiments in the real world are time-consuming and expensive, a great alternative is learning about physics through simulations. The simulators available below let you get a practical feel for many of the phenomena you’ll be studying.

• A wide variety of interactive physics simulations,³² covering topics like buoyancy, electric charges, density, and projectile motion.
• Another large group of simulations³³ to choose from, mainly focusing on the interaction of simplified objects like springs and pendulums. You can adjust all the properties of these objects, like size and mass, and see how those changes affect the simulation.
• A set of sophisticated physics simulations³⁴ on chemistry, biology, and physics. Accessing these simulations costs money, but your school may be able to purchase them for you.

For more information, please see the following entries in the companion book A Chronicle of Ideas: A Guide for Superheroines (and Superheroes): Orbits of Celestial Bodies, Quarks, String Theory, Multi-Dimensional Manifolds, Quantum Probability Fields, Terahertz Frequency, Hidden Variable, Probabilistic Nature of Quantum Mechanics, Falsifiable Experiment, Collapse of the Wave Function, Presence of an Observer, Entangled Membranes, Curled Dimensions, Anti-matter, Hidden Dance of Pairs, Entangled Particles at a Distance, Speed of Light, Heisenberg’s Uncertainty Principe, Gaussian Distribution, Muons, State Information in a Quantum Field, Quantum, Hidden Quantum Variable, Indirect Measurements in Physics, CERN Accelerator, Multi-Dimensional Folds, Probabilistic Elements in Physics, Indeterminate Nature of Quantum Mechanics, Nanotechnology.