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Physics

Classical Mechanics

• What is a Lagrangian?

• How does pumping on a swing make you swing higher?

• Are fictitious forces (centrifugal, Coriolis, Euler) real?

• Effective potentials and Lagrange points

• Matter - Why do ice spikes form in ice trays?

Fluid Mechanics

• What causes buoyancy?

• How fast does pressure move?/Speed of sound

• Bernoulli equation/Venturi effect, 1, 2

• How do wings produce lift?

• The Coriolis force, cyclones, and toilets

• Do airplanes heat up in flight?

• Rayleigh and Fanno flows, choking

Gravity and General Relativity

• Do we weigh less at the equator than at the poles due to the centrifugal force of the Earth's rotation? 1, 2, 3

• What is gravity like inside the Earth?

• What is the relationship between space-time and gravitation?

• Does the force of gravity have an infinite range?

• If light has no mass, how does gravity affect it?

• What is the gravitational force at the center of the Earth?

• Does gravitational force inside the Earth go down with depth? Does the non-linear density of the Earth have an effect?

• If you could drill a hole directly through the center of the Earth and jumped in, what would happen?

• How does gravity vary as you go towards the centre of the Earth?

• Perihelion precession of Mercury

• What is imaginary time?

• Why is it difficult to describe gravity with a quantum field theory?

Light and Special Relativity

• Check out our FAQ Friday on the speed of light!

• Why can't we go faster than the speed of light?

• What's the difference between space and time?

• How was the speed of light first calculated?

• If you add two things going near the speed of light, why don't they add up to be faster than the speed of light?

• If you add together the velocity of two things going at very close to the speed of light, why don't they add up to be faster than the speed of light? (Alternate)

• If I push on a stiff rod that's one light year long, isn't the rod going to move faster than the speed of light?

• If you had an infinitely stiff rod and pushed it, could you transmit information faster than the speed of light? (Alternate)

• Is light massless?

• What is mass?

• Does light have momentum?

• How quickly do photons accelerate to the speed of light once they're emitted?

• What happens to light when it interacts with a material?

• If light has no mass, how does gravity affect it?

• Why isn't it possible for light to escape a black hole?

• What is the relationship between light and time?

• Does light experience time?

• Can quantum entanglement be used to communicate information faster than the speed of light?

• How do we resolve the Twin Paradox?

Electromagnetism

• How do superconductors have zero resistance?

• Where does the energy in magnetism come from?

• How do magnets work?

• Does a full hard drive weigh more?

• Magnetic monopoles

• What's the difference between high-energy x-rays and gamma rays

Nuclear and Atomic Physics

• Nuclear physics - Nuclear masses and binding energies

• Nuclear Physics - What keeps protons together in the nucleus?

• Nuclear Physics - What determines the energy released by a nuclear reaction?

• Nuclear Physics - What determines nuclear half-lives?

• Nuclear Physics - What exactly does it mean to be "stable"?

• Nuclear Physics - Why are technetium and promethium radioactive?

• Nuclear Physics - How do we know that the strong force is short-ranged?

• Nuclear Physics - Fission and fusion

• Nuclear Physics - What makes something fissile?

• Nuclear Physics - Heavy element nucleosynthesis

• Nuclear Physics - How are the heavy elements formed in nature?

• Nuclear Physics - Why didn't the Big Bang produce heavier elements?

• Nuclear and Atomic Physics - Is there a limit to the number of elements?

• Nuclear Physics - Island of stability

• Nuclear Physics - Why is it difficult to produce superheavy nuclides?

• Nuclear Physics - Cold fusion

• Nuclear and Atomic Physics - Are atoms and nuclei spherical?

• Nuclear and Atomic Physics - Are there orbitals beyond s, p, d, and f?

• Nuclear Physics - How many isotopes can each element have?

• Nuclear Physics - How are exotic isotopes produced?

• Nuclear Physics - What's the difference between "nuclear" and "thermonuclear"?

• Nuclear Physics - Can any material sustain a fission chain reaction?

• Nuclear Physics - Can you make a nuclear weapon out anything?

• Nuclear Physics - Hydrogen bombs/Teller-Ulam design

• Nuclear Physics - Nuclear weapon safety

• Nuclear Physics - Mushroom clouds from nuclear weapons

Quantum and Particle Physics

• Field Theory - What is Gauge Theory? (Layman's version)

• Field Theory - What is Gauge Theory? (Physicist's version)

• Particle Physics - What are the fundamental particles and their behaviors?

• Particle Physics - What is antimatter?

• Quantum Physics - What is quantum entanglement? What can it do?

• Quantum Physics - What is the significance of the Planck scale?

• Quantum Physics - Do photons really need exactly the right energy to excite an atom?

• Quantum Physics - Are particle decays instantaneous?

• Quantum Physics - Why does the Pauli exclusion principle exist?

• Quantum Physics and Field Theory - What is the relationship between quantum mechanics and QFT?

• Quantum Field Theory - Force carriers and virtual particles

• Quantum Field Theory - What are virtual particles?

• Quantum Field Theory - What determines the ranges of forces?

• Quantum Field Theory - What is renormalization?

• Quantum Field Theory - Why is it difficult to describe gravity with a QFT?

Statistical Mechanics and Thermodynamics

• What is entropy?

• How are the different definitions of entropy equivalent?

• Maximum entropy and equilibrium

• Can the entropy of a closed system decrease?

• What is the difference between heat, temperature, and internal energy?

• Why are negative absolute temperatures "hot"?

• How are negative absolute temperatures achieved?

Optics and Color

• FAQ Friday on color!**

• Red and violet blend together on the color wheel but they're on opposite ends of the spectrum of visible light?

• The visual spectrum uses red, green, and blue (RGB) but not in color theory and CMYK used in printers. Why?

• Why can we see colors like pink and brown when they aren't on the visible light spectrum?

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