The event marks 100 years since the development of matrix mechanics (Quantum Mechanics) by German physicist Werner Heisenberg in 1925 on the Island of Helgoland off the coast of Germany. This was the first formal mathematical framework for quantum mechanics, enabling the prediction of quantum behaviour in atoms, such as emission spectra.
Later that year, Austrian physicist Erwin Schrödinger devised an alternative approach called wave mechanics, which became more popular and widely accepted, this was published in 1926.
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Quantum mechanics is a branch of physics that deals with the behaviour of very small particles, like atoms and electrons. It's different from the physics we see in our everyday lives, often referred to as classical physics.
The key ideas in Quantum mechanics:
1. Wave-Particle Duality:
In quantum mechanics, particles like electrons can act both like particles and waves. This means they can spread out and interfere with each other, which is very different from how we usually think about particles.
2. Quantisation:
Energy in the quantum world comes in small, discrete packets called "quanta." For example, light is made up of tiny packets of energy called photons. This idea was first introduced by Max Planck and is a fundamental concept in quantum mechanics.
3. Uncertainty Principle:
Werner Heisenberg discovered that you can't know everything about a particle at the same time. For example, if you know exactly where an electron is, you can't know exactly how fast it's moving, and vice versa. This is known as the Heisenberg Uncertainty Principle.
4. Superposition:
Particles can exist in multiple states at once. For example, an electron can be in two places at the same time until you measure it. This is called superposition. A famous thought experiment called Schrödinger's Cat illustrates this idea, where a cat in a box with a poison can be both alive and dead until you open the box and look.
5. Entanglement:
When particles become entangled, the state of one particle is instantly connected to the state of another, no matter how far apart they are. This means that if you change one particle, the other one changes instantly, even if it's on the other side of the universe. Albert Einstein called this "spooky action at a distance."
Quantum mechanics helps us understand the fundamental nature of the universe at the smallest scales.
Applications:
Quantum mechanics isn't just a weird theory; it has real-world applications. It's the basis for technologies like lasers, MRI machines, and even the development of quantum computers, which have the potential to solve problems much faster than today's computers.
Timeline of Key Historical Milestones in Quantum Science
1900: Planck's Solution to the Ultraviolet Catastrophe
· Max Planck introduces the concept of energy quanta, proposing that energy is emitted in discrete packets, laying the foundation for quantum mechanics. Quanta mean that the quantity can have discrete values only. This is fundamental to our understanding of quantum science.
1905: Einstein's Photoelectric Effect
· Albert Einstein explains the photoelectric effect by proposing that light consists of quanta (photons), demonstrating wave-particle duality- demonstrate in class with the double slit experiment (can be done cheaply using a laser pointer with a microscope slide, painted black with 2 VERY fine lines scratched in VERY closely together)- this video is very clear and this simulation is useful.
1913: Bohr's Quantum Model of the Atom
· Niels Bohr develops a model of the atom with quantized energy levels, explaining atomic spectra and stability
1925-1926: Birth of Quantum Mechanics
· Werner Heisenberg formulates matrix mechanics, and Erwin Schrödinger develops wave mechanics, providing two equivalent formulations of quantum mechanics
Matrix mechanics represents physical quantities, like position and momentum, as matrices rather than continuous variables. Key points about matrix mechanics:
- Quantisation: In matrix mechanics, observable quantities are quantised and represented by matrices. The elements of these matrices correspond to the possible values that the quantities can take.
- Non-commutative Algebra: In classical mechanics, the order in which you multiply quantities like position and momentum doesn't matter. For example, p x s is the same as s x p. However, in quantum mechanics, this isn't true. The order of multiplication does matter. For example, multiplying the position matrix by the momentum matrix gives a different result than multiplying the momentum matrix by the position matrix. This property is called non-commutativity and is a key feature of quantum mechanics.
- Heisenberg's Uncertainty Principle: Matrix mechanics naturally incorporates the uncertainty principle, which states that certain pairs of physical properties, like position and momentum, cannot both be precisely known simultaneously.
- Energy Levels: In quantum mechanics, the energy levels of a system, like an atom, are not continuous but come in specific, discrete values. These specific values are called eigenvalues. Think of it like a staircase: you can stand on one step or another, but not in between. Each step represents a different energy level that an electron in an atom can have. This explains why atoms emit or absorb light at specific colours (or wavelengths), corresponding to the jumps between these energy levels.
- Equivalence to Wave Mechanics: Matrix mechanics is mathematically equivalent to wave mechanics, another formulation of quantum mechanics developed by Erwin Schrödinger. Both formulations describe the same physical phenomena but use different mathematical approaches.
1927: Heisenberg Uncertainty Principle
· Werner Heisenberg introduces the uncertainty principle, stating that the position and momentum of a particle cannot both be precisely determined simultaneously
1928: Dirac's Relativistic Quantum Mechanics
· Paul Dirac formulates the Dirac equation, predicting the existence of antimatter and combining quantum mechanics with special relativity
The Dirac equation, is a cornerstone of quantum mechanics and has several key reasons for its importance:
o It combines Quantum Mechanics and Special Relativity:
The Dirac equation successfully merges the principles of quantum mechanics with Albert Einstein's theory of special relativity. This was a significant achievement because it provided a framework for understanding the behaviour of particles moving at relativistic speeds (speeds close the the speed of light).
o Predicting Antimatter:
One of the most remarkable predictions of the Dirac equation was the existence of antimatter. The equation suggested that for every particle, there is a corresponding antiparticle with the same mass but opposite charge. This prediction was experimentally confirmed with the discovery of the positron in 1932.
o Fine Structure of Hydrogen:
The equation accurately accounts for the fine structure of the hydrogen atom's spectral lines, which classical theories could not explain.
1935: Schrödinger's Cat
· Erwin Schrödinger proposes a thought experiment to illustrate the paradoxes of quantum superposition and measurement
AI generated image Co-pilot 7th February
1947: Discovery of Quantum Electrodynamics (QED)
· Richard Feynman, Julian Schwinger, and Sin-Itiro Tomonaga develop QED, describing how light and matter interact at the quantum level
1964: Bell's Theorem
· John Bell formulates Bell's theorem, showing that no local hidden variable theories can reproduce all the predictions of quantum mechanics
1982: Experimental Verification of Quantum Entanglement
· Alain Aspect conducts experiments confirming the reality of quantum entanglement, supporting the non-locality predicted by quantum mechanics
Everyday uses of Quantum Mechanics
Quantum mechanics might seem like a complex and abstract field, but it plays a crucial role in many technologies we use every day.
· Transistors and Semiconductors:
The foundation of all modern electronics, including computers, smartphones, and tablets, relies on transistors and semiconductors. These devices operate based on quantum principles.
· Lasers:
Lasers are used in various applications, from barcode scanners and laser printers to medical surgeries and cutting-edge research. The operation of lasers is based on the quantum phenomenon of stimulated emission.
· Magnetic Resonance Imaging (MRI):
MRI machines, used in hospitals for detailed imaging of the human body, rely on quantum mechanics to manipulate the spin of atomic nuclei.
· Global Positioning System (GPS) Technology:
GPS that helps us navigate relies on precise time measurements, which are made possible by quantum mechanics.
· Fluorescent Lights:
Fluorescent bulbs work by exciting electrons in mercury vapor to higher energy levels. When these electrons return to their original levels, they emit light, a process explained by quantum mechanics.
· Solar Panels:
Solar panels convert sunlight into electricity using the photoelectric effect, a quantum phenomenon where light photons knock electrons loose from atoms.
· Quantum Computing:
Although still in its early stages, quantum computing promises to revolutionize computing by performing complex calculations much faster than classical computers.
· Encryption and Cybersecurity:
Quantum mechanics is used in developing secure communication methods, such as quantum key distribution, which ensures that data cannot be intercepted without detection.
Quantum Mechanics in the natural world.
Photosynthesis as a Quantum Process
Photosynthesis is the process by which plants convert sunlight into energy, and it involves quantum mechanics.
Light Absorption: When sunlight reaches a plant, the photons are absorbed by chlorophyll in the plant's leaves.
Energy Transfer: The energy from the photons excites the electrons in the chlorophyll transferring the energy. This is where quantum mechanics comes in. The excited electrons need to transfer their energy to other parts of the plant to start converting the carbon dioxide and water to glucose.
Quantum Coherence: Instead of taking just one path, the excited electrons use a quantum phenomenon called coherence. This means they explore multiple paths at the same time to find the most efficient route to transfer their energy. This enables the photon to try all possible ways to get somewhere and instantly pick the best one.
Energy Conversion: Once the energy reaches the right place, it's used to convert carbon dioxide and water into glucose and oxygen.
Photosynthesis uses quantum mechanics to make the process of transferring energy incredibly efficient. This helps plants make the most out of the sunlight they receive, ensuring they can produce enough food to survive and grow.
Other ways we see quantum mechanics in nature are:
Bird Navigation: Some birds, like the robin, use a quantum process to navigate. They have a protein called cryptochrome in their eyes, which helps them sense Earth's magnetic field through quantum entanglement, allowing them to migrate accurately.
Enzyme Reactions: Enzymes, which are proteins that catalyse (speed up) chemical reactions in our bodies, sometimes use quantum tunnelling. This allows particles to pass through energy barriers, making reactions happen faster than they would otherwise.
Photosensitive Molecules: In our eyes, the molecules that detect light (photoreceptors) rely on quantum mechanics to change shape when they absorb photons. This process is essential for vision.