Quantum Gravity
Why Physics Stack Exchange recommends it
Physics Stack Exchange users link it to illustrate how enormously weaker gravity is than electromagnetism and to explain why gravity matters in the microworld and what properties a graviton would need.
Recommended by 1 people across 1 different months, 2018 to 2023.
What it is
A 9-minute explainer from Fermilab in which physicist Don Lincoln describes why gravity is so hard to fit into quantum physics. He covers how weak gravity is next to the other forces, why particle experiments cannot detect it, and what a graviton would have to be.
What people said
Recommends mmesser314 · 2023-11 · Physics Stack Exchange · on “In JJ Thomson's cathode ray experiment why is effects due to gravity on electron ignored?”
Let's try a somewhat different approach. A rule of thumb is the electromagnetic forces are far, far stronger than gravitational forces. Don Lincoln's video Quantum Gravity [this video] describes this in the first couple minutes. Then it goes on to other things. Let us look for this. Suppose the high voltage in your diagram is $100$ V. Suppose the tube is half a meter long. Suppose the deflection of the beam is $1$ cm. These are somewhere in the neighborhood of reasonable numbers, though the voltage is likely higher. $100$ V will accelerate $1$ Coulomb of charged particles to an energy of $100$ Joules. It will accelerate $1$ electron $ = 1.6 \times 10^{-19}$ Coulomb to $1.6 \times 10^{-17}$ Joules
Cites Shirish · 2018-08 · Physics Stack Exchange · on “"Gravity, even if weak, must apply in the microworld"”
So I was just watching this video [this video] and at 1:42 [this video] he mentions, "If all we had to go on was the data from particle physics experiments, we wouldn't even know gravity existed." Then at 2:23 [this video] - "Gravity, even if weak, must apply in the microworld. That's not a very profound thought, but it's true." Might be a stupid question, but I don't see why he's so confident that that would be true. I'm just curious about the reason, especially since he mentioned that detecting gravity effects in quantum-scale experiments is impossible ( 1:33 [this video] ).
Cites user256968 · 2020-04 · Physics Stack Exchange · on “Graviton properties defined”
In this video [LINK] Dr.Lincoln says that the weak interaction is weak in low energies because the particles cannot emit the Z and W bosons easily. He mentions the decay of a neutron to a proton an electron and an electron antineutrino.He says the beta decay through the weak interaction happens slowly because for it to happen a W boson with mass 0.002 billion eV/c^2 must be emmited and the W boson has an average mass of 90 billion eV/c^2 -> it is very rare to find a W boson with such low mass which will cause the decay. He made another video about quantum gravity [this video] which highlights some of the properties graviton must have: averagely massless ( averagely moving at c , does not decay(in
Cites mmesser314 · 2021-12 · Physics Stack Exchange · on “Is space build of smaller space-particles?”
Let me answer this in parts. It is too much of a leap to say matter is stretchy and bendable. Matter is made of atoms. Space is stretchy and bendable. Space must be made of atoms too. There could be other ways of being stretchy and bendable. Space can curve, but it is a different thing from the stretchiness of matter. We don't know what space is like on the tiniest scales. We can't say if space has a granular structure or not. Part of the reason that matter is stretchy comes from it being made of atoms. The atoms are connected together with atomic bonds, and the bonds are stretchy and bendable to a degree. But that isn't the only way to imagine the cause of an object being stretchable. Peopl
Cites mmesser314 · 2023-11 · Physics Stack Exchange · on “In JJ Thomson's cathode ray experiment why is effects due to gravity on electron ignored?”
In the Millikan oil drop experiment, the upward force is from the electric field on $1$ (or a few) electrons. The downward force is the gravitational attraction between an oil drop (perhaps a trillion atoms, each with a mass of perhaps 10000 electrons) and the entire Earth. Gravity is unimaginably weaker. See Quantum Gravity [this video]