6 ms·

List of Unsolved Problems in Physics

105 points by lukas 12y ago

new299 12y ago
I always find reading over this article pretty entertaining, in particular Sonoluminescence generally catches my attention: http://en.wikipedia.org/wiki/Sonoluminescence http://en.wikipedia.org/wiki/Sonoluminescence As it seems like it should be practical to replicate it on a relatively small budget.
- stolio 12y ago
  Looks like they can reproduce it at will but they can't figure out why it happens.
  - new299 12y ago
    yep, I find it interesting that on a relatively small budget (hobbyist level) you can reproduce an experiment which exhibits unexplained physical phenomena. It gives me some home that there's still interesting experimental physics to be done on a low budget. Potentially by hobbyists outside of a traditional industrial or academic framework.
- accurrent 12y ago
  Its pretty hard to observe as the luminisence is ridiculously low.
  - new299 12y ago
    Huh? The luminisence is for very short periods of time, but I don't believe it's particularly challenging to detect. I would imagine it's more challenging to setup the chamber. The first paragraph of the wikipedia article should tell you it's not that hard to detect: "H. Frenzel and H. Schultes put an ultrasound transducer in a tank of photographic developer fluid. They hoped to speed up the development process. Instead, they noticed tiny dots on the film after developing and realized that the bubbles in the fluid were emitting light with the ultrasound turned on." Other articles suggest photomultipler tubes have been used, with which you can detect single photons. PMT are relatively cheap (I've seen them for ~30USD on ebay), the motivation seems to be to get good time domain resolution. Even so other pages suggest that around 500,000 photons are produced. This should be relatively tractable. Obviously it's not as easy as making an LED flash, but I can't see that it would be intractable for a hobbyist.
ggonweb 12y ago
The list of unsolved problems by field http://en.wikipedia.org/wiki/Lists_of_unsolved_problems http://en.wikipedia.org/wiki/Lists_of_unsolved_problems
- Beltiras 12y ago
  I find the "Unsolved in AI" funny. One sentence is enough for the entire article: "We have no idea what the problem is but when we do we should come back and make this list."
calebm 12y ago
I want a room-temperature superconductor!
spanko_at_large 12y ago
"Whats a Z job?" "If you have to ask you can't afford it" -Beerfest "What are some unsolved physics problems?" "If you have to ask you can't solve them" -spanko
bglazer 12y ago
"Ecliptic alignment of CMB anisotropy Some large features of the microwave sky at distances of over 13 billion light years appear to be aligned with both the motion and orientation of the solar system. Is this due to systematic errors in processing, contamination of results by local effects, or an unexplained violation of the Copernican principle?" Wait what? An unexplained violation of the Copernican principle? That's pretty crazy. What is being referred to? The article on the CMB says that it's isotropic to one part in a thousand
- TheOtherHobbes 12y ago
  http://arstechnica.com/science/2014/03/is-the-universe-lopsided/ http://arstechnica.com/science/2014/03/is-the-universe-lopsi...
- Ono-Sendai 12y ago
  The anisotropy of the CMBR is easily explained in terms of red/blue shift due to the velocity of the earth, solar system, galaxy etc.., as long as you don't mind violating special relativity. (in some sense) See http://en.wikipedia.org/wiki/Cosmic_microwave_background http://en.wikipedia.org/wiki/Cosmic_microwave_background, 'CMBR dipole anisotropy'
suprgeek 12y ago
The one (listed under other problems) which always struck me since the first time I heard it: "How does the quantum description of reality, which includes elements such as the superposition of states and wavefunction collapse or quantum decoherence, give rise to the reality we perceive? " I still vividly remember the first time I heard the "collapse of the wavefunction" and openly challenged our poor Solid-state electronics professor - it led to a looong discussion at the end of which he got flustered enough that after shifting thru entanglement, decoherence, Measurement problems, many worlds interpretation, Bohm, time travelling interactions, philosophy, etc he pretty much kicked me out of his office. I think I might have partly contributed to him seeking a transfer to another dept. the next year...
- whatshisface 12y ago
  There is a bit of a parable I hear told sometimes when this topic comes up: A man is being taught how computers work, and is presented with the design of an adder in the form of a few Boolean logic expressions. Thinking back to the true "reality" of addition, he rejects the design of the adder on the grounds that nand gates have no apparent connection to the sensible reality of having 5 apples and 3 oranges and 8 fruits. This would be considered a ridiculous objection in every field but physics, where misunderstandings following from it have become the basis of many bestsellers. For some reason, we consider the math involved in physics to be exempt from the otherwise universal sense of abstraction that all the other fields enjoy. We don't go looking for tiny calculators in bacteria capable of plotting out exponential population growth, so why should the weirdness of quantum math cause so much trouble?
  - noobermin 12y ago
    I'm not so sure this is a fair comparison. Anything that grows proportionally to its population will grow exponentially, math just says it will, and you can't avoid that. You can look at the bacteria itself and see that bacteria divide, and so, you expect this sort of growth, and so, it mathematically follows. It just isn't that way for QM, nothing in nature says that systems have to evolve by a hermitian operator on a fock space, we just know that it gives us the right results. I think part of the issue is that Physicists really care about why, not whether something fits the model.
cmpb 12y ago
Reading through these makes me really miss my undergraduate days as a physics major. Only marginally related: If you ever have a chance to go to one of the LIGO [1] sites (Laser Interferometer Gravitational-wave Observatory), do go take a tour! I've been to the one in Livingston, Louisiana [2], and it is simply amazing. The technology used and the science involved is very interesting. It's also kid-friendly! [1] http://www.ligo.caltech.edu/ http://www.ligo.caltech.edu/ [2] http://www.ligo-la.caltech.edu/ http://www.ligo-la.caltech.edu/
mijoharas 12y ago
It's been a while since my physics degree but aren't the "cosmological constant problem" and the "vacuum catastrophe" two different phrasings for the same problem? reading through to the linked pages doesn't help me in understanding what the difference between the two is (or if there is any).
lkbm 12y ago
> The beauty and clearness of the dynamical theory, which asserts heat and light to be modes of motion, is at present obscured by two clouds. Lord Kelvin's two clouds led us to relativity and quantum mechanics.

105 points by lukas 12y ago

I always find reading over this article pretty entertaining, in particular Sonoluminescence generally catches my attention: http://en.wikipedia.org/wiki/Sonoluminescence http://en.wikipedia.org/wiki/Sonoluminescence As it seems like it should be practical to replicate it on a relatively small budget.

stolio 12y ago
Looks like they can reproduce it at will but they can't figure out why it happens.
- new299 12y ago
  yep, I find it interesting that on a relatively small budget (hobbyist level) you can reproduce an experiment which exhibits unexplained physical phenomena. It gives me some home that there's still interesting experimental physics to be done on a low budget. Potentially by hobbyists outside of a traditional industrial or academic framework.
accurrent 12y ago
Its pretty hard to observe as the luminisence is ridiculously low.
- new299 12y ago
  Huh? The luminisence is for very short periods of time, but I don't believe it's particularly challenging to detect. I would imagine it's more challenging to setup the chamber. The first paragraph of the wikipedia article should tell you it's not that hard to detect: "H. Frenzel and H. Schultes put an ultrasound transducer in a tank of photographic developer fluid. They hoped to speed up the development process. Instead, they noticed tiny dots on the film after developing and realized that the bubbles in the fluid were emitting light with the ultrasound turned on." Other articles suggest photomultipler tubes have been used, with which you can detect single photons. PMT are relatively cheap (I've seen them for ~30USD on ebay), the motivation seems to be to get good time domain resolution. Even so other pages suggest that around 500,000 photons are produced. This should be relatively tractable. Obviously it's not as easy as making an LED flash, but I can't see that it would be intractable for a hobbyist.

ggonweb 12y ago

The list of unsolved problems by field http://en.wikipedia.org/wiki/Lists_of_unsolved_problems http://en.wikipedia.org/wiki/Lists_of_unsolved_problems

Beltiras 12y ago
I find the "Unsolved in AI" funny. One sentence is enough for the entire article: "We have no idea what the problem is but when we do we should come back and make this list."

calebm 12y ago

I want a room-temperature superconductor!

spanko_at_large 12y ago

"Whats a Z job?" "If you have to ask you can't afford it" -Beerfest "What are some unsolved physics problems?" "If you have to ask you can't solve them" -spanko

bglazer 12y ago

"Ecliptic alignment of CMB anisotropy Some large features of the microwave sky at distances of over 13 billion light years appear to be aligned with both the motion and orientation of the solar system. Is this due to systematic errors in processing, contamination of results by local effects, or an unexplained violation of the Copernican principle?" Wait what? An unexplained violation of the Copernican principle? That's pretty crazy. What is being referred to? The article on the CMB says that it's isotropic to one part in a thousand

TheOtherHobbes 12y ago
http://arstechnica.com/science/2014/03/is-the-universe-lopsided/ http://arstechnica.com/science/2014/03/is-the-universe-lopsi...
Ono-Sendai 12y ago
The anisotropy of the CMBR is easily explained in terms of red/blue shift due to the velocity of the earth, solar system, galaxy etc.., as long as you don't mind violating special relativity. (in some sense) See http://en.wikipedia.org/wiki/Cosmic_microwave_background http://en.wikipedia.org/wiki/Cosmic_microwave_background, 'CMBR dipole anisotropy'

suprgeek 12y ago

The one (listed under other problems) which always struck me since the first time I heard it: "How does the quantum description of reality, which includes elements such as the superposition of states and wavefunction collapse or quantum decoherence, give rise to the reality we perceive? " I still vividly remember the first time I heard the "collapse of the wavefunction" and openly challenged our poor Solid-state electronics professor - it led to a looong discussion at the end of which he got flustered enough that after shifting thru entanglement, decoherence, Measurement problems, many worlds interpretation, Bohm, time travelling interactions, philosophy, etc he pretty much kicked me out of his office. I think I might have partly contributed to him seeking a transfer to another dept. the next year...

whatshisface 12y ago
There is a bit of a parable I hear told sometimes when this topic comes up: A man is being taught how computers work, and is presented with the design of an adder in the form of a few Boolean logic expressions. Thinking back to the true "reality" of addition, he rejects the design of the adder on the grounds that nand gates have no apparent connection to the sensible reality of having 5 apples and 3 oranges and 8 fruits. This would be considered a ridiculous objection in every field but physics, where misunderstandings following from it have become the basis of many bestsellers. For some reason, we consider the math involved in physics to be exempt from the otherwise universal sense of abstraction that all the other fields enjoy. We don't go looking for tiny calculators in bacteria capable of plotting out exponential population growth, so why should the weirdness of quantum math cause so much trouble?
- noobermin 12y ago
  I'm not so sure this is a fair comparison. Anything that grows proportionally to its population will grow exponentially, math just says it will, and you can't avoid that. You can look at the bacteria itself and see that bacteria divide, and so, you expect this sort of growth, and so, it mathematically follows. It just isn't that way for QM, nothing in nature says that systems have to evolve by a hermitian operator on a fock space, we just know that it gives us the right results. I think part of the issue is that Physicists really care about why, not whether something fits the model.

cmpb 12y ago

Reading through these makes me really miss my undergraduate days as a physics major. Only marginally related: If you ever have a chance to go to one of the LIGO [1] sites (Laser Interferometer Gravitational-wave Observatory), do go take a tour! I've been to the one in Livingston, Louisiana [2], and it is simply amazing. The technology used and the science involved is very interesting. It's also kid-friendly! [1] http://www.ligo.caltech.edu/ http://www.ligo.caltech.edu/ [2] http://www.ligo-la.caltech.edu/ http://www.ligo-la.caltech.edu/

mijoharas 12y ago

It's been a while since my physics degree but aren't the "cosmological constant problem" and the "vacuum catastrophe" two different phrasings for the same problem? reading through to the linked pages doesn't help me in understanding what the difference between the two is (or if there is any).

lkbm 12y ago

> The beauty and clearness of the dynamical theory, which asserts heat and light to be modes of motion, is at present obscured by two clouds. Lord Kelvin's two clouds led us to relativity and quantum mechanics.