Philip Gibbs - inactive
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What reasons are there to suspect string theory may be an incorrect theory?
8 votes

I don't know any reason to suspect string theory may be incorrect, but the closest analogy to renormalisation infinities is the fact that we only know string theory as a perturbation series from a ...

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Binary Black Hole Solution of General Relativity?
8 votes

There are no exact solutions, only approximations and numerical solutions. Don't forget that orbiting black holes will radiate gravitational waves so any solution would have to include those and the ...

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Basic Spin or Double Cover Experiment
8 votes

No that is not how it works. A 360 rotation multiplies the wave function by a factor -1 which by itself is not observable. It does not switch up and down spins. An experiment which demonstrated the ...

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How did Newton discover his third law of motion?
7 votes

The third law states that to every action (force) there is an equal and opposite reaction. According to "The historical context of Newton's Third Law and the teaching of mechanics" by Colin Gauld, ...

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Is integrability necessary for the Amplituhedron?
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7 votes

This question is answered by Nima Arkani-Hamed in his Simons Center talk, at about 112 minutes in. His answer is that the structure of the amplituhedron itself does not directly use integrability of ...

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Is everything made of massless particles?
7 votes

This is a very interesting question. It turns out that in the standard model before symmetry breaking the only particle with a mass term is the Higgs boson itself (and possibly the neutrinos) The ...

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Is there a trajectory which is not a solution of the equation of motion but satisfies all conservation laws?
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7 votes

The conservation laws provide just a few equations so if there are more degrees of freedom you can find trajectories that obey all conservation laws but which do not obey the dynamics. E.g. two ...

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Group Theory in General Relativity
7 votes

Symmetry is just as important in General Relativity as it is in Special Relativity. In SR the symmetry is the Poincare Group which is the group of mappings of space-time to itself that preserves the ...

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Your favorite Physics/Astrophysics blogs?
7 votes

Resonances Another best place for detailed reports on new particle physics discoveries (and rumours)

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All objects radiate energy, but we cannot see all objects in the dark. Why?
6 votes

Any warm body radiates electromagnetic radiation with a spectrum that depends on the temperature. Above 500 degree centrigrade there is enough radiation in the visible part of the spectrum to be ...

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Different age of universe
6 votes

You can define the age of the universe at any spacetime event defined as a place and time as the longest time measured along any timelike worldline stretching from the event back to the big bang. ...

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What are the implications of the Holographic principle?
6 votes

The holographic principle tells us that the description of what happens in a volume of space can be encoded on a surface that surrounds it. This is related to the Bekenstein bound that tells us that ...

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What happens if you try to freeze water in an water tight container
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6 votes

In order to keep the density of water at 1kg/litre as you decrease its temperature below 0 centigrade you would need a container that remained rigid at many thousands of atmospheres pressure. The ...

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Why do prescription glasses that darken in sunlight fail to darken when the light travels through a car windshield?
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6 votes

Reaction sunglasses (also known as photochromic glasses) go dark in reaction to ultraviolet light with wavelengths from 280-320 nm. The smallest wavelength of visible light is around 390 nm. Ordinary ...

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Rotations in space-time
6 votes

Take a system of four mutually orthogonal vectors lined up with the four axis x,y,z,t in 4D space. Apply an arbitrary rotation to move the four axis to some other positions. They remain mutually ...

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Might the LHC see nothing new at all?
6 votes

It is possible that the LHC could find just a standard model scalar Higgs. It would have to fit in the windows between 135 GeV and 157 GeV or 173 GeV to 185 GeV. In this case no new physics is needed ...

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Your favorite Physics/Astrophysics blogs?
6 votes

A Quantum Diaries Survivor The best place for detailed reports on new particle physics discoveries (and rumours)

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Does any particle ever reach any singularity inside the black hole?
6 votes

This puzzle is an aspect of the black hole information loss paradox and a proposed solution is the holographic principle and black hole complementarity. The classical view of black holes is that any ...

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Can an insulator have magnetic poles?
6 votes

In principle I can see no reason why an insulator cannot be magnetic, but in practice all pure materials that are ferromagentic seem to be conductors. This includes iron, nickel, cobalt and Gadolinium....

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What is "special" and what is "general" in Relativity?
5 votes

In special relativity the laws of physics are covariant under Poincaré transformation, whereas in general relativity the laws of physics are generally covariant, meaning that they take the same form ...

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Why are trajectories in General Relativity speed-dependant?
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5 votes

The trajectories are worldlines in 4D spacetime, not just paths in 3D space. They maximise proper time along the trajectory. They do not minimise distance along the curve traced through space. An ...

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What's the real fundamental definition of energy?
5 votes

Definitions of physical quantities in physics are dependent on context. For example the definition of energy in classical general relativity is different from the definition used in the quantum ...

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Other possible theories (other than string theory) which are generalizations of the standard model with incorporation of gravity
5 votes

This is the proverbial sixty-four thousand dollar question for fundamental physics. It may be helpful to split it down into steps. What are the possible consistent theories of quantum gravity? Which ...

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Two axes for rotational motion
5 votes

Angular rotation is a vector so at any given instant any rigid body can only be rotating about one axis. If the body is rotating freely in space with no external forces then angular momentum is ...

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Does the Pauli exclusion principle instantaneously affect distant electrons?
5 votes

Cox said that when he heats the diamond every electron in the universe shifts energy levels instantly to respect the Pauli Exclusion Principle. The problem here is not that he is talking about energy ...

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So, no Higgs boson then?
5 votes

The signal for a Higgs boson is still alive and kicking in the data. There were some reports that is had "faded" in strength since the EPS conference in July but that is not true. CMS had changed ...

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Is a "third quantization" possible?
5 votes

In the context of quantum field theory Weinberg's advice to ignore the term "second quantisation" is good advice. However, to go beyond quantum field theory anything goes and some people have promoted ...

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What happens when I place an object of certain temperature in space ? Does it loose its entire heat energy?
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4 votes

If (hypothetically) you could find a far off region of space where there is no radiation of any sort, and you place a hot object there, then it would radiate away its heat and gain no heat back from ...

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Breaking ocean waves on other planets possible?
4 votes

Breaking waves are understood as a breakdown in the solutions of the shallow wave equations. So yes there will be breaking waves on any world that has liquid seas with wind to generate waves big ...

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Mercury's orbit
4 votes

The actual amount of the precession for Mercury is about 574 arcsec/century so your figure is ten times too big. This is mostly due to tugs from other planets. Oblateness of Sun has an effect but too ...

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