The two main theories in physics are quantum physics and Einstein's theory of general relativity.
These two theories represent the bedrock of modern physics and are crucial for understanding the universe at different scales. Quantum physics deals with the behavior of matter and energy at the atomic and subatomic levels, while general relativity describes gravity as a curvature of spacetime caused by mass and energy.
Key Differences and Relationships
| Feature | Quantum Physics | General Relativity |
|---|---|---|
| Scale | Microscopic (atomic, subatomic) | Macroscopic (cosmic) |
| Focus | Particles and their interactions | Gravity and spacetime |
| Concepts | Quantization, wave-particle duality, uncertainty | Curvature of spacetime, gravity as geometry |
- Quantum physics: Explains the behavior of particles like electrons and photons.
- It uses concepts like quantization of energy (energy comes in discrete packets).
- It introduces the wave-particle duality (particles can act like waves, and vice-versa).
- It has the uncertainty principle (there are limits to how precisely we can know certain properties of a particle).
- Einstein's general relativity: Explains how gravity works on large scales.
- Gravity is not a force but a curvature of spacetime caused by mass and energy.
- Objects move along the curves in spacetime caused by mass.
The Central Open Question
According to the reference, a central open question in theoretical physics is understanding how these two theories are related. They are both incredibly successful in their respective domains, but they are fundamentally incompatible. This incompatibility is a major challenge for physicists.
Practical Insights
- Quantum physics is essential for understanding electronics, lasers, and medical imaging technologies such as MRI.
- General relativity is crucial for understanding the behavior of black holes, the expansion of the universe, and the GPS technology used in daily life.
Examples
- An example of quantum physics is the laser, which uses the principle of stimulated emission of photons.
- An example of general relativity is the orbital motion of planets around the sun, which is due to the curvature of spacetime caused by the sun's mass.
Solutions
While there is no single solution that unifies quantum physics and general relativity, there are many ongoing research efforts attempting to solve this problem:
- String Theory
- Loop Quantum Gravity
- Other alternative theories
These are just a few of the many attempts at finding a theory of everything.
