Since photons are massless, they always move at the speed of light. However, they can still have different energies and momenta; but in contrast to massive objects (E=p^2/2m and p=mv), for a photon both are given by the frequency (E=hf and p=E/c).
One of the interesting differences between Newton's theory of gravity and Einstein's general relativity, is that in relativity everything is affected by gravity, including massless particles such as photons. What happens then, is that the gravitational field changes the energy of the particle, causing it's frequency to shift. This causes a "gravitational redshift" when a photon moves out of a gravitational field, and a "gravitational blueshift" when a photon moves into a gravitational field.
I haven't looked at this article in detail, but I would guess that it relies on somehow blueshifting a laser to increase the energy and momentum of the photons in the beam. This laser can in theory then be used to more efficiently push other objects away.
If they're handing over single queries, without tracking/correlating/storing/selling which queries come from the same person (e.g. via cookies, browser fingerprinting, etc.), I'm okay with it. It's the profiling I dislike about Google and Microsoft, not the collection of anonymized data.
Depends on the topic. For e.g. tech searches, it works really well. But if you're trying to search for a scientific paper where you don't have a doi or arXiv identifier (but know e.g. the first author's last name, the journal abbreviation, the volume number, and the publication year), Google usually shows it as its first or second result, while DuckDuckGo can show 20-30 results that cite that article before getting it right. In my experience, searching for local businesses where I live is also much easier on Google, even if I add my city and country to the search terms.
But I agree that it's worth supporting DuckDuckGo for privacy reasons, and luckily, you can always add a !g when you're searching for stuff it does badly. (I have the same attitude to OpenStreetMaps vs. Google Maps; I usually try the open alternative first, but know that for some searches, I'll just have to resort to Google.)
Depends on your country. In many European countries, legal rights cannot be signed away, because that would be quite prone to abuse. Instead, if you signed a contract where you gave away any legal rights, then that part of the contract is simply considered illegal and void.
As far as I know, D-Wave doesn't make any universal quantum computers, but only quantum annealers. That means that they can solve some optimization problems on their machine, but they can't actually run e.g. Shor's integer factorization algorithm. As far as I'm aware, the current record for universal quantum computers is Google's Bristlecone, which has 72 qubits with a single-qubit error rate of ~0.1%. For comparison, most quantum error correction require an error rate of below 0.001% or so, and running Shor's algorithm to break 2048-bit RSA encryption might require up to 10,000 qubits. It'll probably be a while until they'll find those primes for you.
Saying that you can't model the climate without an accurate prediction of the weather tomorrow, is like saying that you can't model tides without an accurate prediction of the ocean waves tomorrow.
I use a Google-free version of Android on my phone. I try to use F-droid apps where I can. When that is not sufficient, I often check if there's a webapp for it. Webapps can't run in the background, and can't force arbitrary permissions out of you, so they at least track you less than ususal apps. So e.g. the few times I need to resort to Google Maps, having a bookmark to the web page that opens in a mobile browser is sufficient. When I really need a proprietary app, I use Amazon's app store (doesn't need as many permissions as Google Play Services) or Yalp (downloads free Google Play apps without a Google account).
The US has the largest prison population in the world per capita. If you define a "free country" as a "country where you deprive as few people as possible of their freedoms", then the prison population alone disproves your point.
For the record: I'm a physicist doing research on superconductivity. My own work is on low-temperature superconductivity, but I've tried to keep up-to-date on high-temperature stuff.
Actually, they do. The electron-electron interaction of a Cooper pair has energies on the order of 10E-3 eV. The "high temperature superconductors" assume that somehow you can compensate the random heat movement (kT) and (also random) electric repulsion (order of eVs) by interactions in the crystal lattice.
This is a bit disingenuous. First of all, the critical temperature of a superconductor is proportional to the pairing energy, so trying to find a high-temperature superconductor is synonymous with increasing this energy scale. Having a pairing energy of ~1meV is typical for a good low-temperature superconductor (like Nb), where the pairing is caused by phonons. Compensating the random heat movement (~kT) would happen precisely by increasing the pairing energy proportionally. Note also that we don't really know how most high-temperature superconductors work (cuprates), but some theories actually invoke the electric repulsion you brought up as a possible mechanism for superconductivity.
Since the main question was whether high-temperature superconductors break any known laws of physics, you might also be interested to know that we already have near-room-temperature superconductors. After the discovery of superconductivity at 203K (-70C) in sulfur hydride (SH3) a couple of years ago, the record was recently pushed to 250K (-23C) in lanthanum hydride (LaH10). The caveat is that these materials require millions of atmospheres of pressure to function at these temperatures, so they're not that useful for practical applications. But they do demonstrate that room-temperature superconductivity is not prohibited by any physical laws; for instance, a high-pressure hydride would still be subject to the same thermal (~kT) and electron repulsion (~eV) conditions you referred to, but they still work. Secondly, if one is able to replicate the conditions inside these crystals chemically instead of via external pressure (e.g. via the "pressure" between atomic layers in a crystal), they could in principle be made more useful.
As for the article itself: I agree that it sounds unlikely. I'll believe it when I see a published paper replicating the effect, and eliminating other possible explanations of the observations. There are bogus papers claiming to discover high-temperature superconductivity all the time, such as this obvious fraud that made some headlines last year.
Yeah, you're right:). Fundamentally, the distinction between fermions and bosons is about whether the wavefunction of two identical particles is an antisymmetric or symmetric function in their coordinates. Antisymmetric wave functions directly result in the Pauli exclusion principle, while symmetric wave functions allow for Bose-Einstein condensation.
In quantum field theory, the so-called spin-statistics theorem connects these properties of the wave function to the particle spins. But that theorem is only valid under certain constraints. This theorem not valid in e.g. condensed matter systems: not only can one have fermions with integral spins and bosons with half-integral spins (due to "flux attachment"), but you can have even more exotic anyons, which are neither bosons nor fermions. So these are some examples where the spin-statistics theorem breaks down, and you have to actually look at the symmetries of the wave function with respect to swapping particles to really figure out if you're dealing with fermions or bosons.
I know that some composite force carriers exist, but that wasn't my point. My point was that "the rule" that all bosons are force carriers and all fermions are matter particles doesn't hold for composite particles. It's often repeated in the science journalism related to particle physics, but that "rule" only works for the elementary particles in the standard model. (Whether it makes sense to think of neutronos as matter and Higgs boson a force carrier is a different story, but at least that rule-of-thumb works okay for the other fundamental particles.)
Regardless of whether rubidium could in principle act as a force carrier or not, my point still stands: the dichotomy between bosons as force carriers and fermions as matter particles clearly has to break down at the atomic level. If you're arguing that rubidium is not matter, then that would be really strange. If you claim that it is matter, but could potentially be a force carrier as well, then you still have to concede that grouping stuff into the mutually exclusive groups "matter" and "forces" doesn't work anymore since rubidium would be both.
If you really want, you can calculate the probability amplitude for a particle spontaneously emitting a virtual rubidium atom as a force carrier, and that being absorbed by another atom. I suspect that the probability will be roughly zero. Similarly to other technically possible scenarios, like a human spontaneously quantum tunneling from Earth to Mars.
Actually, referring to fermions as "matter particles" and bosons as "force carriers" is an oversimplification, and is only true for the elementary particles of the standard model. The true distinction between them is that fermions follow Fermi-Dirac statistics, while bosons follow Bose-Einstein statistics. In practice, this means that fermions follow the Pauli exclusion principle (and thus repel each other), while bosons do not (and can condense into macroscopic quantum states).
If you put together these elementary particles, it turns out that an odd number of them forms a composite fermion, while an even number of them forms a composite boson. If you want to think about it in terms of the spin-statistics theorem you referred to: you can put together two spin-1/2 fermions to form either a spin-0 or a spin-1 composite particle, and either one would be a boson. But if you put together three spin-1/2 fermions, the result has to be a spin-1/2 or spin-3/2 particle, which is again a fermion.
This is very important at low temperatures, since e.g. He-3 atoms (fermions) repel each other, while He-4 atoms (bosons) do not, so only the latter can directly enter a macroscopic quantum state. The same distinction is relevant for the common isotopes of potassium and rubidium.
So in this case, the error in science journalism is not calling potassium a fermion and rubidium a boson. The error is to call fermions "matter particles" and bosons "force carriers". That is a simplification that only happens to be true for the elementary particles, but not composite particles.
Actually, rubidium is a boson, the article is correct. Fundamentally, the distinction between bosons and fermions is the distinction between particles that follow Bose-Einstein statistics (bosons) and those that follow Fermi-Dirac statistics (fermions). Due to the spin-statistics theorem, you end up with bosons having integral spins (0, 1, etc.) and fermions having half-integral spins (1/2, 3/2, etc.). The short version of the statistics is that fermions obey the Pauli exclusion principle (so they repel each other), while bosons do not (so they can condense into a macroscopic quantum state).
It so happens that for the elementary particles in the standard model, all matter particles (leptons and quarks) are fermions, while what we call force carriers (photons etc.) are bosons. But this does not hold true in general. For composite particles, you end up with an odd number of subatomic particles combining to form a fermion, while an even number of subatomic particles form a boson. This is again relevant because e.g. He-3 is a composite fermion, so a cold gas of those atoms will repel each other due to the Pauli exclusion principle; while He-4 is a composite boson, so a cold gas of those atoms will form a macroscopic quantum state known as a "Bose-Einstein condensate". Thus, just changing the number of neutrons in the nucleus actually has an enormous effect on the behavior of a gas at sufficiently low temperatures. (In the case of He-3 and He-4, the latter can form a superfluid directly, while the former has to create boson-like pairs in a manner that is similar to what happens in superconductors before any exotic phase transition can take place.)
This is actually accurate. All "subatomic components" (protons, neutrons, and electrons) are fermions. Put an odd number of fermions together, and you get a composite fermion. Put an even number of fermions together, and you create a composite boson. So whether the atom is a fermion or boson can be established by counting the subatomic building blocks in the atom. Since atoms have one electron per proton if they're not ionized, you can alternatively say that an odd vs. even number of neutrons decides whether the atom is a fermion or boson (so e.g. He-3 is a fermion, while He-4 is a boson).
This is important to cold atomic gases because the Pauli exclusion principle only applies to fermions. This means that fermions usually repel each other, while boson gases do this.
Responding in a timely manner shows that you are conscientious -- organized, dependable and hardworking. And that matters. In a comprehensive analysis of people in hundreds of occupations, conscientiousness was the single best personality predictor of job performance. (It turns out that people who are rude online tend to be rude offline, too.)
Conscientiousness is one of the Big Five, which together with your IQ, can predict work performance quite well. Being conscientious, among other things, implies that you naturally try to respond in a timely manner. But that doesn't mean that forcing yourself to answer emails more rapidly makes you more conscientious, nor that answering emails more rapidly will affect overall work performance. In other words: forcing non-conscientious people to reply quickly may just end up decorrelating reply time from conscientiousness, instead of boosting their overall work performance.
TLDR: Correlations in human behavior tend to change if you try to force new behavioral patterns on them.
This. It's similar to the fact that if someone leaves a password-protected private laptop on their work desk, you could easily use a LiveUSB to boot it up and get around their password protection. If their harddrive isn't encrypted, you can easily copy all their data onto an external harddrive, and have fun with it at home. But if anyone I know did that, including my employer, that should be grounds for suing them, and someone should end up in jail over it.
That it's technically possible to do something doesn't make it right.
...and how exactly is your bible quote related to the science, which discusses how a mutated mixture of two non-homo-sapiens human species appears to have interbred with homo sapiens in ancient times? Or did you perhaps just read the title, and commented without even reading the summary?
I believe it is a prerequisite at some Indian universities for PhD candidates.
My impression that this is the case everywhere but the US/UK. In Europe, a Master's degree is usually a prerequisite for even applying to a PhD program. We have some integrated Bachelor+Master programs, but few integrated Master+PhD programs.
Slashdot Mirror
Since photons are massless, they always move at the speed of light. However, they can still have different energies and momenta; but in contrast to massive objects (E=p^2/2m and p=mv), for a photon both are given by the frequency (E=hf and p=E/c).
One of the interesting differences between Newton's theory of gravity and Einstein's general relativity, is that in relativity everything is affected by gravity, including massless particles such as photons. What happens then, is that the gravitational field changes the energy of the particle, causing it's frequency to shift. This causes a "gravitational redshift" when a photon moves out of a gravitational field, and a "gravitational blueshift" when a photon moves into a gravitational field.
I haven't looked at this article in detail, but I would guess that it relies on somehow blueshifting a laser to increase the energy and momentum of the photons in the beam. This laser can in theory then be used to more efficiently push other objects away.
They have their own crawler as well, according to their Wikipedia page. Bing is just one of ~400 backends used in addition to their own crawler.
If they're handing over single queries, without tracking/correlating/storing/selling which queries come from the same person (e.g. via cookies, browser fingerprinting, etc.), I'm okay with it. It's the profiling I dislike about Google and Microsoft, not the collection of anonymized data.
Depends on the topic. For e.g. tech searches, it works really well. But if you're trying to search for a scientific paper where you don't have a doi or arXiv identifier (but know e.g. the first author's last name, the journal abbreviation, the volume number, and the publication year), Google usually shows it as its first or second result, while DuckDuckGo can show 20-30 results that cite that article before getting it right. In my experience, searching for local businesses where I live is also much easier on Google, even if I add my city and country to the search terms.
But I agree that it's worth supporting DuckDuckGo for privacy reasons, and luckily, you can always add a !g when you're searching for stuff it does badly. (I have the same attitude to OpenStreetMaps vs. Google Maps; I usually try the open alternative first, but know that for some searches, I'll just have to resort to Google.)
You're both right. They have their own crawler, but also source results from ~400 other sites, including e.g. Bing, Wikipedia, and WolframAlpha.
(Posting to undo accidental moderation...)
Depends on your country. In many European countries, legal rights cannot be signed away, because that would be quite prone to abuse. Instead, if you signed a contract where you gave away any legal rights, then that part of the contract is simply considered illegal and void.
As far as I know, D-Wave doesn't make any universal quantum computers, but only quantum annealers. That means that they can solve some optimization problems on their machine, but they can't actually run e.g. Shor's integer factorization algorithm. As far as I'm aware, the current record for universal quantum computers is Google's Bristlecone, which has 72 qubits with a single-qubit error rate of ~0.1%. For comparison, most quantum error correction require an error rate of below 0.001% or so, and running Shor's algorithm to break 2048-bit RSA encryption might require up to 10,000 qubits. It'll probably be a while until they'll find those primes for you.
Saying that you can't model the climate without an accurate prediction of the weather tomorrow, is like saying that you can't model tides without an accurate prediction of the ocean waves tomorrow.
I use a Google-free version of Android on my phone. I try to use F-droid apps where I can. When that is not sufficient, I often check if there's a webapp for it. Webapps can't run in the background, and can't force arbitrary permissions out of you, so they at least track you less than ususal apps. So e.g. the few times I need to resort to Google Maps, having a bookmark to the web page that opens in a mobile browser is sufficient. When I really need a proprietary app, I use Amazon's app store (doesn't need as many permissions as Google Play Services) or Yalp (downloads free Google Play apps without a Google account).
The US has the largest prison population in the world per capita. If you define a "free country" as a "country where you deprive as few people as possible of their freedoms", then the prison population alone disproves your point.
Actually, they do. The electron-electron interaction of a Cooper pair has energies on the order of 10E-3 eV. The "high temperature superconductors" assume that somehow you can compensate the random heat movement (kT) and (also random) electric repulsion (order of eVs) by interactions in the crystal lattice.
This is a bit disingenuous. First of all, the critical temperature of a superconductor is proportional to the pairing energy, so trying to find a high-temperature superconductor is synonymous with increasing this energy scale. Having a pairing energy of ~1meV is typical for a good low-temperature superconductor (like Nb), where the pairing is caused by phonons. Compensating the random heat movement (~kT) would happen precisely by increasing the pairing energy proportionally. Note also that we don't really know how most high-temperature superconductors work (cuprates), but some theories actually invoke the electric repulsion you brought up as a possible mechanism for superconductivity.
Since the main question was whether high-temperature superconductors break any known laws of physics, you might also be interested to know that we already have near-room-temperature superconductors. After the discovery of superconductivity at 203K (-70C) in sulfur hydride (SH3) a couple of years ago, the record was recently pushed to 250K (-23C) in lanthanum hydride (LaH10). The caveat is that these materials require millions of atmospheres of pressure to function at these temperatures, so they're not that useful for practical applications. But they do demonstrate that room-temperature superconductivity is not prohibited by any physical laws; for instance, a high-pressure hydride would still be subject to the same thermal (~kT) and electron repulsion (~eV) conditions you referred to, but they still work. Secondly, if one is able to replicate the conditions inside these crystals chemically instead of via external pressure (e.g. via the "pressure" between atomic layers in a crystal), they could in principle be made more useful.
As for the article itself: I agree that it sounds unlikely. I'll believe it when I see a published paper replicating the effect, and eliminating other possible explanations of the observations. There are bogus papers claiming to discover high-temperature superconductivity all the time, such as this obvious fraud that made some headlines last year.
Yeah, you're right :). Fundamentally, the distinction between fermions and bosons is about whether the wavefunction of two identical particles is an antisymmetric or symmetric function in their coordinates. Antisymmetric wave functions directly result in the Pauli exclusion principle, while symmetric wave functions allow for Bose-Einstein condensation.
In quantum field theory, the so-called spin-statistics theorem connects these properties of the wave function to the particle spins. But that theorem is only valid under certain constraints. This theorem not valid in e.g. condensed matter systems: not only can one have fermions with integral spins and bosons with half-integral spins (due to "flux attachment"), but you can have even more exotic anyons, which are neither bosons nor fermions. So these are some examples where the spin-statistics theorem breaks down, and you have to actually look at the symmetries of the wave function with respect to swapping particles to really figure out if you're dealing with fermions or bosons.
I know that some composite force carriers exist, but that wasn't my point. My point was that "the rule" that all bosons are force carriers and all fermions are matter particles doesn't hold for composite particles. It's often repeated in the science journalism related to particle physics, but that "rule" only works for the elementary particles in the standard model. (Whether it makes sense to think of neutronos as matter and Higgs boson a force carrier is a different story, but at least that rule-of-thumb works okay for the other fundamental particles.)
Regardless of whether rubidium could in principle act as a force carrier or not, my point still stands: the dichotomy between bosons as force carriers and fermions as matter particles clearly has to break down at the atomic level. If you're arguing that rubidium is not matter, then that would be really strange. If you claim that it is matter, but could potentially be a force carrier as well, then you still have to concede that grouping stuff into the mutually exclusive groups "matter" and "forces" doesn't work anymore since rubidium would be both.
If you really want, you can calculate the probability amplitude for a particle spontaneously emitting a virtual rubidium atom as a force carrier, and that being absorbed by another atom. I suspect that the probability will be roughly zero. Similarly to other technically possible scenarios, like a human spontaneously quantum tunneling from Earth to Mars.
Actually, referring to fermions as "matter particles" and bosons as "force carriers" is an oversimplification, and is only true for the elementary particles of the standard model. The true distinction between them is that fermions follow Fermi-Dirac statistics, while bosons follow Bose-Einstein statistics. In practice, this means that fermions follow the Pauli exclusion principle (and thus repel each other), while bosons do not (and can condense into macroscopic quantum states).
If you put together these elementary particles, it turns out that an odd number of them forms a composite fermion, while an even number of them forms a composite boson. If you want to think about it in terms of the spin-statistics theorem you referred to: you can put together two spin-1/2 fermions to form either a spin-0 or a spin-1 composite particle, and either one would be a boson. But if you put together three spin-1/2 fermions, the result has to be a spin-1/2 or spin-3/2 particle, which is again a fermion.
This is very important at low temperatures, since e.g. He-3 atoms (fermions) repel each other, while He-4 atoms (bosons) do not, so only the latter can directly enter a macroscopic quantum state. The same distinction is relevant for the common isotopes of potassium and rubidium.
So in this case, the error in science journalism is not calling potassium a fermion and rubidium a boson. The error is to call fermions "matter particles" and bosons "force carriers". That is a simplification that only happens to be true for the elementary particles, but not composite particles.
Actually, rubidium is a boson, the article is correct. Fundamentally, the distinction between bosons and fermions is the distinction between particles that follow Bose-Einstein statistics (bosons) and those that follow Fermi-Dirac statistics (fermions). Due to the spin-statistics theorem, you end up with bosons having integral spins (0, 1, etc.) and fermions having half-integral spins (1/2, 3/2, etc.). The short version of the statistics is that fermions obey the Pauli exclusion principle (so they repel each other), while bosons do not (so they can condense into a macroscopic quantum state).
It so happens that for the elementary particles in the standard model, all matter particles (leptons and quarks) are fermions, while what we call force carriers (photons etc.) are bosons. But this does not hold true in general. For composite particles, you end up with an odd number of subatomic particles combining to form a fermion, while an even number of subatomic particles form a boson. This is again relevant because e.g. He-3 is a composite fermion, so a cold gas of those atoms will repel each other due to the Pauli exclusion principle; while He-4 is a composite boson, so a cold gas of those atoms will form a macroscopic quantum state known as a "Bose-Einstein condensate". Thus, just changing the number of neutrons in the nucleus actually has an enormous effect on the behavior of a gas at sufficiently low temperatures. (In the case of He-3 and He-4, the latter can form a superfluid directly, while the former has to create boson-like pairs in a manner that is similar to what happens in superconductors before any exotic phase transition can take place.)
This is actually accurate. All "subatomic components" (protons, neutrons, and electrons) are fermions. Put an odd number of fermions together, and you get a composite fermion. Put an even number of fermions together, and you create a composite boson. So whether the atom is a fermion or boson can be established by counting the subatomic building blocks in the atom. Since atoms have one electron per proton if they're not ionized, you can alternatively say that an odd vs. even number of neutrons decides whether the atom is a fermion or boson (so e.g. He-3 is a fermion, while He-4 is a boson).
This is important to cold atomic gases because the Pauli exclusion principle only applies to fermions. This means that fermions usually repel each other, while boson gases do this.
And with legal matters. Doing a crime "on the computer" is always worth stronger punishment.
Responding in a timely manner shows that you are conscientious -- organized, dependable and hardworking. And that matters. In a comprehensive analysis of people in hundreds of occupations, conscientiousness was the single best personality predictor of job performance. (It turns out that people who are rude online tend to be rude offline, too.)
Conscientiousness is one of the Big Five, which together with your IQ, can predict work performance quite well. Being conscientious, among other things, implies that you naturally try to respond in a timely manner. But that doesn't mean that forcing yourself to answer emails more rapidly makes you more conscientious, nor that answering emails more rapidly will affect overall work performance. In other words: forcing non-conscientious people to reply quickly may just end up decorrelating reply time from conscientiousness, instead of boosting their overall work performance.
TLDR: Correlations in human behavior tend to change if you try to force new behavioral patterns on them.
This. It's similar to the fact that if someone leaves a password-protected private laptop on their work desk, you could easily use a LiveUSB to boot it up and get around their password protection. If their harddrive isn't encrypted, you can easily copy all their data onto an external harddrive, and have fun with it at home. But if anyone I know did that, including my employer, that should be grounds for suing them, and someone should end up in jail over it.
That it's technically possible to do something doesn't make it right.
The half-life of U-238 is roughly the same as the age of the Earth. I think we can handle that.
I'm not the AC above, but they probably thought about this one.
...and how exactly is your bible quote related to the science, which discusses how a mutated mixture of two non-homo-sapiens human species appears to have interbred with homo sapiens in ancient times? Or did you perhaps just read the title, and commented without even reading the summary?
I believe it is a prerequisite at some Indian universities for PhD candidates.
My impression that this is the case everywhere but the US/UK. In Europe, a Master's degree is usually a prerequisite for even applying to a PhD program. We have some integrated Bachelor+Master programs, but few integrated Master+PhD programs.
It's easy for a fact-checker to say that claim is false, because the physics of a blue sky are well-understood.
Actually, physics say that the sky is violet. It's biology that makes it blue, since our eyes are not very sensitive to violet.