Scope asks: What are the boundaries of physics? What topics, questions, and problems does physics cover?
In IB Physics, the scope is massive — from studying subatomic particles (Quantum Physics, Nuclear Physics) to understanding the behavior of galaxies (Astrophysics).
Physics deals with phenomena on all scales: time, size, and energy. But it also recognizes its limits — for example, physics cannot fully describe consciousness or moral values.
Studying gravitational fields (D1) explores motion on astronomical scales.
Studying thermodynamics (B4) helps explain engines, stars, and even black holes — but only within the assumptions of our models.
Physics defines its scope through models and theories but acknowledges where other disciplines (like biology or ethics) must take over.
Perspective asks: How do different viewpoints affect our understanding in physics?
In physics, different models provide different perspectives on reality. Classical mechanics gives one view; quantum mechanics gives another — and they don't always align. Cultural, historical, and technological contexts also influence which theories are developed or prioritized.
Newtonian physics vs Special Relativity: Different perspectives on motion and time depending on the observer's frame.
Particle vs wave models: Light can be viewed either as a wave (interference) or a particle (photoelectric effect).
Physics teaches that reality can be viewed through multiple frameworks — and context matters.
Methods & Tools asks: How does physics investigate reality? What techniques, models, and instruments does it use?
Physics depends heavily on the scientific method, mathematical modeling, and experimental validation. Tools range from simple (stopwatches, rulers) to complex (particle accelerators, space telescopes).
Using Faraday’s law and oscilloscopes to study electromagnetic induction (D4).
Using graphical analysis (slopes, areas under curves) to interpret kinematics and dynamic systems (A1, A2).
Progress in physics often depends on inventing better methods (like the Large Hadron Collider) and refining mathematical tools (like calculus, vector analysis).
Ethics asks: What moral responsibilities come with the pursuit and application of physics?
Physics discoveries often have profound consequences for society, which creates ethical responsibilities for scientists and engineers.
The development of nuclear physics leading to both nuclear power and atomic weapons (E4 Fission).
The use of physics in understanding and combating climate change (B2 Greenhouse Effect).
Debates over space exploration vs focusing resources on Earth (Astrophysics and Energy Resources).
Just because something can be done (like building nuclear weapons or AI-based surveillance) does not mean it should be done — and physicists must engage in these ethical debates.
In physics, evidence is essential for validating theories, models, and laws. Without experimental evidence, claims remain speculation.
For example, the observation that electrons create an interference pattern when passed through a double-slit apparatus provides evidence that particles exhibit wave-like behavior. Without this experimental evidence, the concept of wave-particle duality would not have been accepted.
In another example, astronomers use observational evidence (period, separation, Doppler shifts) to determine the masses and properties of binary stars. Here, evidence (spectral data) is critical for justifying models of stellar motion and structure.
Certainty in physics is often limited. Even widely accepted laws are based on measurements that carry uncertainties, and theories can be revised when new data emerges.
For example, Newtonian mechanics was once considered absolutely certain, but experiments showing time dilation and length contraction at high velocities forced a shift to Einstein’s theory of special relativity. This shows that certainty in physics is always provisional.
In another example, when applying conservation of momentum to collisions, physicists must account for uncertainties in measurements like velocity and mass. Therefore, experimental confirmation of conservation laws always includes an allowance for experimental error, reflecting the limits of certainty.
Truth in physics is often seen as provisional rather than absolute. Models and theories are accepted as "true" only as long as they consistently explain observations and survive experimental testing.
For example, the idea that time and space are absolute was once regarded as true under Newtonian physics. However, with the development of special relativity, it became clear that time and space are relative to the observer’s frame of reference, shifting the accepted “truth” of how the universe operates.
In another example, the Bohr model of the atom was once accepted as the true description of atomic structure. Later developments in quantum mechanics revealed that electrons do not move in fixed orbits but exist in probabilistic clouds, updating the truth about atomic behavior.
Physics often requires interpreting experimental results, and different interpretations can lead to different theories and models.
For example, when interpreting the perihelion precession of Mercury, scientists originally thought it might be due to unknown planets or measurement errors. However, Einstein’s interpretation led to the theory of general relativity, which successfully explained the anomaly through spacetime curvature.
In another example, interpreting the results of the Young’s double-slit experiment was crucial: instead of seeing light as purely a stream of particles (the Newtonian view), scientists interpreted the interference pattern as evidence for the wave nature of light.
Knowledge in physics grants humanity significant power, enabling technological advancement but also carrying risks and ethical challenges.
For example, understanding nuclear fission allowed for the development of nuclear power plants, providing massive energy generation capabilities. However, the same knowledge enabled the creation of nuclear weapons, demonstrating the dual power of scientific knowledge.
In another example, mastery of electromagnetic fields and induction principles led to the widespread generation and distribution of electricity, profoundly transforming societies by powering industries, homes, and communications.
With the power that scientific knowledge provides comes a responsibility to consider how discoveries are applied and their consequences for society and the environment.
For example, physicists who understood the principles behind nuclear fission had to confront the moral responsibility of how their work was used — leading to both nuclear energy and nuclear weapons. The Manhattan Project scientists famously struggled with this burden.
In another example, understanding the physics behind the greenhouse effect places a responsibility on scientists and policymakers to address climate change. Knowing how infrared radiation is absorbed by greenhouse gases forces societies to act on that knowledge to mitigate environmental impacts.
Physics seeks to explain phenomena through models, theories, and laws that reveal underlying patterns in nature.
For example, simple harmonic motion explains how systems like pendulums, springs, and even molecular bonds vibrate. This single concept unifies diverse phenomena under a common mathematical and conceptual framework.
In another example, gravitational force is explained as the force that provides the necessary centripetal acceleration for planets and satellites to orbit. Newton’s laws and later Einstein’s theory of general relativity both offer powerful explanations for orbital motion.
Physics aspires to objectivity, aiming to describe the natural world in a way that is independent of personal bias or perspective. However, true objectivity can be difficult to fully achieve.
For example, in experiments involving conservation of momentum during collisions, objectivity is sought by carefully controlling variables and using statistical methods to account for experimental errors and uncertainties.
In another example, graphical analysis of motion — like determining velocity from the slope of a displacement-time graph — offers an objective, visual method for extracting physical quantities directly from experimental data, minimizing subjective interpretation.
Different perspectives in physics can lead to alternative models or interpretations of phenomena, enriching our understanding but also highlighting that no single viewpoint captures all aspects of reality.
For example, in the kinetic theory of gases, the microscopic perspective focuses on the random motion of molecules, while the macroscopic perspective uses pressure, volume, and temperature. Both are valid but describe the system differently.
In another example, viewing gravitational attraction either through Newton’s law (a force between masses) or Einstein’s general relativity (curved spacetime) provides two perspectives on the same phenomenon, each valuable in different contexts.
Physics does not develop in isolation; cultural, historical, and societal contexts shape scientific inquiry and determine which areas are explored.
For example, the race to develop nuclear technology during World War II was driven by cultural and political pressures, leading to enormous investments in nuclear physics research through the Manhattan Project.
In another example, the modern global focus on climate change has driven cultural interest and funding into areas like renewable energy physics, atmospheric modeling, and energy efficiency research.
Scientific communities prioritize certain values, such as simplicity, predictive power, reproducibility, and coherence, which influence which models and theories are accepted.
For example, conservation laws (like conservation of energy or momentum) are valued because they simplify analysis and apply universally, providing powerful tools across multiple domains of physics.
In another example, the ideal gas law is prized for its simplicity and ability to predict the behavior of gases under many conditions, even though it is an approximation. Its widespread use reflects the value placed on models that are simple yet broadly applicable.
In physics, theories, models, and experimental conclusions must be justified through logical reasoning, mathematical consistency, and empirical evidence.
For example, in mechanics, the conservation of mechanical energy (kinetic + potential) is justified by extensive experimental observations showing that, in closed systems without friction, total energy remains constant. This justification makes it a foundational principle used across physics.
In another example, the quantization of angular momentum in the Bohr model is justified by the need to explain discrete emission spectra observed in hydrogen. Classical physics could not account for these spectral lines, but the Bohr model’s quantized orbits provided a justified explanation matching experimental data.