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There are a number of people starting to follow this collection (Dr. Koberlein) and apparently nothing else on my page. That is fine but it is a bit unusual. I would suggest that you follow Dr. Koberlein's page, though you are more than welcome here. I am merely organizing posts of his that I like (and would have reshared to "public" in the Classic G+) into a single (new G+) collection to keep track of them.

See +Brian Koberlein page.

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Somewhat interesting in light of the current fascination with certain theories. For my part, I always see if I can find the technical discussions that back up the claims, discussions from "uninterested" experts. Of course, such a person is inherently interested but what do they have invested in the train of thought? What do they have to loose?

I enjoy speculation - and I have no problem with it from others as long as it is obviously speculation. But if you tell me it's "science", then I had better be able to find the justification of it in technical terms from a person who is not writing from self-interest. On this, I have never had a problem in the main - except for one thing.

Nullius in Verba
Take no one's word for it.
Doing It Wrong

Lots of models kinda fit observational data. Good science focuses on the weaknesses of a model and strives to improve them. Bad science claims a rough fit overcomes any theoretical contradictions.

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Since the spectrum of light from matter and antimatter is the same, a distant antimatter galaxy would look the same to us as if it were made of matter. Since we can’t travel to distant galaxies directly to prove their made of matter, how can we be sure antimatter galaxies don’t exist?

If you are following this collection, you should also be following Dr. Koberlein - see the post below and click on the link to get to it. Or:
Antimatter Astronomy

In astronomy we study distant galaxies by the light they emit. Just as the stars of a galaxy glow bright from the heat of their fusing cores, so too does much of the gas and dust at different wavelengths. The pattern of wavelengths we observe tells us much about a galaxy, because atoms and molecules emit specific patterns of light. Their optical fingerprint tells us the chemical composition of stars and galaxies, among other things. It’s generally thought that distant galaxies are made of matter, just like our own solar system, but recently it’s been demonstrated that anti-hydrogen emits the same type of light as regular hydrogen. In principle, a galaxy of antimatter would emit the same type of light as a similar galaxy of matter, so how do we know that a distant galaxy really is made of matter?

The basic difference between matter and antimatter is charge. Atoms of matter are made of positively charged nuclei surrounded by negatively charged electrons, while antimatter consists of negatively charged nuclei surrounded by positively charged positrons (anti-electrons). In all of our interactions, both in the lab and when we’ve sent probes to other planets, things are made of matter. So we can assume that most of the things we see in the Universe are also made of matter.

However, when we create matter from energy in the lab, it is always produced in pairs. We can, for example, create protons in a particle accelerator, but we also create an equal amount of anti-protons. This is due to a symmetry between matter and antimatter, and it leads to a problem in cosmology. In the early Universe, when the intense energy of the big bang produced matter, did it also produce an equal amount of antimatter? If so, why do we see a Universe that’s dominated by matter? The most common explanation is that there is a subtle difference between matter and antimatter. This difference wouldn’t normally be noticed, but on a cosmic scale it means the big bang produced more matter than antimatter.

But suppose the Universe does have an equal amount of matter and antimatter, but early on the two were clumped into different regions. While our corner of the Universe is dominated by matter, perhaps there are distant galaxies or clusters of galaxies that are dominated by antimatter. Since the spectrum of light from matter and antimatter is the same, a distant antimatter galaxy would look the same to us as if it were made of matter. Since we can’t travel to distant galaxies directly to prove their made of matter, how can we be sure antimatter galaxies don’t exist?

One clue comes from the way matter and antimatter interact. Although both behave much the same on their own, when matter and antimatter collide they can annihilate each other to produce intense gamma rays. Although the vast regions between galaxies are mostly empty, they aren’t complete vacuums. Small amounts of gas and dust drift between galaxies, creating an intergalactic wind. If a galaxy were made of antimatter, any small amounts of matter from the intergalactic wind would annihilate with antimatter on the outer edges of the galaxy and produce gamma rays. If some galaxies were matter and some antimatter, we would expect to see gamma ray emissions in the regions between them. We don’t see that. Not between our Milky Way and other nearby galaxies, and not between more distant galaxies. Since our region of space is dominated by matter, we can reasonably assume that other galaxies are matter as well.

It’s still possible that our visible universe just happens to be matter dominated. There may be other regions beyond the visible universe that are dominated by antimatter, and its simply too far away for us to see. That’s one possible solution to the matter-antimatter cosmology problem. But that would be an odd coincidence given the scale of the visible universe.

So there might be distant antimatter galaxies in the Universe, but we can be confident that the galaxies we do see are made of matter just like us.

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For some reason, Dr. Koberlein's posts seldom show up in my feed since switching to the new G+ format. So I am catching up today.

And for those of you following this collection, I would suggest that you should at least follow Dr. Koberlein too.

That would be a hint.
A Light Change

One of the big mysteries of modern cosmology is the fact that the Universe is so uniform on large scales. Observations tell us our Universe is topologically flat, and the cosmic microwave background we see in all directions has only the smallest temperature fluctuations. But if the cosmos began with a hot and dense big bang, then we wouldn’t expect such high uniformity. As the Universe expanded, distant parts of it would have moved out of reach from each other before there was time for their temperatures to even out. One would expect the cosmic background to have large hot and cold regions. The most common idea to explain this uniformity is early cosmic inflation. That is, soon after the big bang, the Universe expanded at an immense rate. The Universe we can currently observe originated from an extremely small region, and early inflation made everything even out. The inflation model has a lot going for it, but proving inflation is difficult, so some theorists have looked for alternative models that might be easier to prove. One recent idea looks at a speed of light that changes over time.

The idea that light may have had a different speed in the past isn’t new. Despite the assertions of some young Earth creationists, we know the speed of light has remained constant for at least 7 billion years. The well-tested theories of special and general relativity also confirm a constant speed of light. But perhaps things were very different in the earliest moments of the cosmos. This new work looks at alternative approach to gravity where the speed of gravity and the speed of light don’t have to be the same. In general relativity, if the speed of light changed significantly, so would the speed of gravity, and this would lead to effects we don’t observe. In this new model, the speed of light could have been much faster than gravity early on, and this would allow the cosmic microwave background to even out. As the Universe expanded and cooled, a phase transition would shift the speed of light to that of gravity, just as we observe now.

Normally this kind of thing can be discarded as just another handwaving idea, but the model makes two key predictions. The first is that there shouldn’t be any primordial gravitational waves. Inflation models predict primordial gravitational fluctuations, so if they are observed this new model is ruled out. But it might be the case that primordial gravitational waves are simply too faint to be observed, which would leave inflation in theoretical limbo. But this new model also predicts that the cosmic background should have temperature fluctuations of a particular scale (known as the scalar spectral index ns). According to the model, ns should be about 0.96478. Current observations find ns = 0.9667 ± 0.0040. So the predictions of this model actually agree with observation.

That seems promising, but inflation can’t be ruled out yet. This current model only explains the uniformity of the cosmic background. Inflation also explains things like topological flatness and a few other subtle cosmological issues this new model doesn’t address. The key is that this new model is testable, and that makes it a worthy challenger to inflation.

Paper: Niayesh Afshordi and Joao Magueijo. The critical geometry of a thermal big bang. arXiv:1603.03312 [gr-qc]

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Doing The Wave

There has been a lot of digital ink spilled over the recent paper on the reactionless thrust device known as the EMDrive. While it’s clear that a working EM Drive would violate well established scientific theories, what isn’t clear is how such a violation might be resolved. Some have argued that the thrust could be an effect of Unruh radiation, but the authors of the new paper argue instead for a variation on quantum theory known as the pilot wave model.

One of the central features of quantum theory is its counter-intuitive behavior often called particle-wave duality. Depending on the situation, quantum objects can have characteristics of a wave or characteristics of a particle. This is due to the inherent limitations on what we can know about quanta. In the usual Copenhagen interpretation of quantum theory, an object is defined by its wavefunction. The wavefunction describes the probability of finding a particle in a particular location. The object is in an indefinite, probabilistic state described by the wavefunction until it is observed. When it is observed, the wavefunction collapses, and the object becomes a definite particle with a definite location.

While the Copenhagen interpretation is not the best way to visualize quantum objects it captures the basic idea that quanta are local, but can be in an indefinite state. This differs from the classical objects (such as Newtonian theory) where things are both local and definite. We can know, for example, where a baseball is and what it is doing at any given time.

The pilot wave model handles quantum indeterminacy a different way. Rather than a single wavefunction, quanta consist of a particle that is guided by a corresponding wave (the pilot wave). Since the position of the particle is determined by the pilot wave, it can exhibit the wavelike behavior we see experimentally. In pilot wave theory, objects are definite, but nonlocal. Since the pilot wave model gives the same predictions as the Copenhagen approach, you might think it’s just a matter of personal preference. Either maintain locality at the cost of definiteness, or keep things definite by allowing nonlocality. But there’s a catch.

Although the two approaches seem the same, they have very different assumptions about the nature of reality. Traditional quantum mechanics argues that the limits of quantum theory are physical limits. That is, quantum theory tells us everything that can be known about a quantum system. Pilot wave theory argues that quantum theory doesn’t tell us everything. Thus, there are “hidden variables” within the system that quantum experiments can’t reveal. In the early days of quantum theory this was a matter of some debate, however both theoretical arguments and experiments such as the EPR experiment seemed to show that hidden variables couldn’t exist. So, except for a few proponents like David Bohm, the pilot wave model faded from popularity. But in recent years it’s been demonstrated that the arguments against hidden variables aren’t as strong as we once thought. This, combined with research showing that small droplets of silicone oil can exhibit pilot wave behavior, has brought pilot waves back into play.

How does this connect to the latest EM Drive research? In a desperate attempt to demonstrate that the EM Drive doesn’t violate physics after all, the authors spend a considerable amount of time arguing that the effect could be explained by pilot waves. Basically they argue that not only is pilot wave theory valid for quantum theory, but that pilot waves are the result of background quantum fluctuations known as zero point energy. Through pilot waves the drive can tap into the vacuum energy of the Universe, thus saving physics! To my mind it’s a rather convoluted at weak argument. The pilot wave model of quantum theory is interesting and worth exploring, but using it as a way to get around basic physics is weak tea. Trying to cobble a theoretical way in which it could work has no value without the experimental data to back it up.

At the very core of the EM Drive debate is whether it works or not, so the researchers would be best served by demonstrating clearly that the effect is real. While they have made some interesting first steps, they still have a long way to go.

Paper: Harris, D.M., et al. Visualization of hydrodynamic pilot-wave phenomena, J. Vis. (2016) DOI 10.1007/s12650-016-0383-5

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The LIGO event(s) are still fascinating. It's a signal detection problem, with black holes communicating via space-time.

When we try to develop a quantum version of black holes, weird paradoxes arise.

Theorists have developed possible resolutions to these paradoxes, but there hasn’t been any way to test them.

But a new paper argues that LIGO might actually be able to test these ideas.

But can we detect the residual ringing in the vacuum fluctuations predicted by QM?
Echoes From The Abyss

With the detection of gravitational waves, we’re now able to observe black holes as they merge. We’re already able to determine the mass and rotation of the merging black holes, but gravitational waves might be able to settle the fierce debates over the conflict between black holes and quantum gravity.

The LIGO signals we have so far show the classic properties of a black hole merger. Two orbiting black holes create a regular pattern of gravitational waves that gradually increase in frequency. Eventually the two masses merge, creating a chirp and “ringdown” as the newly formed black hole settles into a stable state. According to general relativity, once the new black hole settles down, it should no longer emit gravitational waves. That’s because a single black hole simply has the properties of mass and rotation (and theoretically charge), but nothing else. This is known as the “no-hair theorem.”

While relativity is a well-tested scientific theory, it runs into problems when you try to incorporate it into quantum theory. The foundational principles of quantum mechanics are very different from that of general relativity, so the two models don’t play well together. Since we have reasons to presume the ultimate theory of gravity is a quantum theory, there has been a lot of research on what such a theory would look like. When we try to develop a quantum version of black holes, weird paradoxes arise. One of them is known as the firewall paradox, where quantum fluctuations would create intense heat near the event horizon of a black hole, though this would seem to violate the equivalence principle, upon which relativity is based. Another is the information paradox, where knowledge of an object disappears when it crosses the event horizon, which violates a fundamental principle of quantum theory. Theorists have developed possible resolutions to these paradoxes, but there hasn’t been any way to test them. We can’t travel to a black hole to look at one up close.

But a new paper argues that LIGO might actually be able to test these ideas. While a classical black hole should be silent after the merger, quantum interactions near the event horizon could create small secondary chirps. These chirps should be regularly spaced, and their timing could put constraints on various quantum models. Interestingly, the team looked at data from the three black hole mergers that have been publicly announced, and found some evidence of these secondary signals. The statistics isn’t particularly strong, so it can’t be confirmed as a real effect, but that will change as we observe more black hole mergers. If these secondary chirps keep showing up, then we might be able to test the quantum behavior of black holes.

It’s an interesting result, and it demonstrates the power of gravitational astronomy.

Paper: Jahed Abedi, et al. Echoes from the Abyss: Evidence for Planck-scale structure at black hole horizons. arXiv:1612.00266 [gr-qc] (2016)

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Interesting update - be sure to read the comments at the OP.

I admit that in my quick scanning of the paper (at another post), I did not note that they did the tests in a vacuum, which is important. I suppose I should read it more carefully now but .... I just cannot get too excited about it. It has to be fake, unless someone can explain the phenomenon. The pilot wave thingee is new to me, except for this:

And then there is of course this:
The Unruh effect was first described by Stephen Fulling in 1973, Paul Davies in 1975 and W. G. Unruh in 1976.[1][2][3] It is currently not clear whether the Unruh effect has actually been observed, since the claimed observations are under dispute. There is also some doubt about whether the Unruh effect implies the existence of Unruh radiation.

Oh well, it will work itself out at some point, with all of this attention.
Jury Of One's Peers

The reactionless thruster known as the EM Drive has stirred heated debate over the past few years. If successful it could provide a new and powerful method to take our spacecraft to the stars, but it has faced harsh criticism because the drive seems to violate the most fundamental laws of physics. One of the biggest criticisms has been that the work wasn’t submitted for peer review, and until that happens it shouldn’t be taken seriously. Well, this week that milestone was reached with a peer-reviewed paper. The EM Drive has officially passed peer review.

It’s important to note that passing peer review means that experts have found the methodology of the experiments reasonable. It doesn’t guarantee that the results are valid, as we’ve seen with other peer-reviewed research such as BICEP2. But this milestone shouldn’t be downplayed either. With this new paper we now have a clear overview of the experimental setup and its results. This is a big step toward determining whether the effect is real or an odd set of secondary effects. That said, what does the research actually say?

The basic idea of the EMDrive is an asymmetrical cavity where microwaves are bounced around inside. Since the microwaves are trapped inside the cavity, there is no propellent or emitted electromagnetic radiation to push the device in a particular direction, standard physics says there should be no thrust on the device. And yet, for reasons even the researchers can’t explain, the EM Drive does appear to experience thrust when activated. The main criticism has focused on the fact that this device heats up when operated, and this could warm the surrounding air, producing a small thrust. In this new work the device was tested in a near vacuum, eliminating a major criticism.

What the researchers found was that the device appears to produce a thrust of 1.2 ± 0.1 millinewtons per kilowatt of power in a vacuum, which is similar to the thrust seen in air. By comparison, ion drives can provide a much larger 60 millinewtons per kilowatt. But ion drives require fuel, which adds mass and limits range. A functioning EM drive would only require electric power, which could be generated by solar panels. An optimized engine would also likely be even more efficient, which could bring it into the thrust range of an ion drive.

While all of this is interesting and exciting, there are still reasons to be skeptical. As the authors point out, even this latest vacuum test doesn’t eliminate all the sources of error. Things such as thermal expansion of the device could account for the results, for example. Now that the paper is officially out, other possible error sources are likely to be raised. There’s also the fact that there’s no clear indication of how such a drive can work. While the lack of theoretical explanation isn’t a deal breaker (if it works, it works), it remains a big puzzle to be solved. The fact remains that experiments that seem to violate fundamental physics are almost always wrong in the end.

I’ve been pretty critical of this experiment from the get go, and I remain highly skeptical. However, even as a skeptic I have to admit the work is valid research. This is how science is done if you want to get it right. Do experiments, submit them to peer review, get feedback, and reevaluate. For their next trick the researchers would like to try the experiment in space. I admit that’s an experiment I’d like to see.

Paper: Harold White, et al. Measurement of Impulsive Thrust from a Closed Radio-Frequency Cavity in Vacuum. Journal of Propulsion and Power. DOI: 10.2514/1.B36120 (2016)

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Uh oh.
Peer Review for the EM Drive

Yep, it's finally passed peer review. Now what?

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Interesting ...
QUESTION: Would you contribute to a crowdfunding campaign to create a demo video in support of pitching a never envisioned science related TV series? Please share if you also know someone who might!
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