http://www.forbes.com/sites/startswithabang/2016/03/18/ask-ethan-could-dark-energy-recycle-the-universe/#3ab4b8be1cd2

http://www.forbes.com/sites/louiscolumbus/2016/03/30/2016-state-of-marketing-high-performing-marketing-teams-4-2x-more-likely-to-use-analytics/#3ab4b8be1cd2

That brings up the issue of finiteness or infiniteness of the universe, which has boggled the minds of scientists all along; simply nobody knows by established science other than that the “observable universe,” which constitutes only 4% of the entire universe, is finite.
Meanwhile, science tells us that according to the Second Law of Thermodynamics, entropy, which is forward-only continuous disorder, points to the fact that the observable universe is winding down to a state of cessation as the total usable energy, which is inversely proportional to entropy, is decreasing.

http://arxiv.org/abs/astro-ph/0312440

http://arxiv.org/abs/astro-ph/0312440

Ethan SiegelEthan Siegel, Contributor
Image credit: NASA / WMAP science team.
Image credit: NASA / WMAP science team.

There’s something eerily similar about the start of our Universe, a period of cosmic inflation, and the driver of the ultimate fate, the accelerated expansion of dark energy, that leads one to speculate if they might be related. In fact, this week’s chosen question comes from Andrew Gillett, who wants to know:

If eternal inflation is correct, could dark energy be a precursor to a return to that original state?

Not only is it possible, it might not even require eternal inflation to be correct. Let’s start by talking about the stage that preceded the birth of the Universe as we know it and set it up: cosmic inflation.

Image credit: E. Siegel, from his book “Beyond the Galaxy,” illustrating the fact that the Universe appears to be the same temperature everywhere, even in causally disconnected regions of the sky.
Image credit: E. Siegel, from his book “Beyond the Galaxy,” illustrating the fact that the Universe appears to be the same temperature everywhere, even in causally disconnected regions of the sky.

When the Universe as we know it — full of matter and radiation — began, it began with a few strange properties that didn’t necessarily have to be so: it was spatially flat, it was the same temperature everywhere, it didn’t have ultra-high-energy relics, and it had a very particular pattern of overdense and underdense regions. It’s possible that the Universe just began with these conditions in place, but the idea of cosmic inflation was that if the Universe started off with a period of exponential expansion, where there was a large amount of energy inherent to space itself, and then that period came to an end, it would create the hot Big Bang with all of these conditions already in place. It took a number of years for the consequences to be worked out properly, and it took even longer for the evidence from the fluctuations in the cosmic microwave background to validate it, but cosmic inflation is now understood to be the first thing we can point to with supporting evidence for it in our Universe’s history.

Fluctuations in spacetime itself at the quantum scale get stretched across the Universe during inflation, giving rise to imperfections in both density and gravitational waves. Image credit: E. Siegel, with images derived from ESA/Planck and the DoE/NASA/ NSF interagency task force on CMB research.
Fluctuations in spacetime itself at the quantum scale get stretched across the Universe during inflation, giving rise to imperfections in both density and gravitational waves. Image credit: E. Siegel, with images derived from ESA/Planck and the DoE/NASA/ NSF interagency task force on CMB research.

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Eternal inflation is an offshoot of inflation, based on a property you might not think about very often. Normally, when you have a transition in nature — like a pot of very hot water that’s transitioning from the liquid state to the gaseous state — it happens in different locations to start, and those locations expand and merge together. In the case of boiling water, we call this “percolating,” when the small bubbles rise and merge together, creating larger bubbles by time they reach the surface. In inflation, however, you have this problem where the regions where inflation doesn’t end at a particular point in time continue to expand exponentially, and this prevents the regions where it does end from “percolating.” Our observable Universe, therefore, must all be contained within a single bubble where inflation ended, rather than being made from many bubbles that percolated together.

An illustration of eternal inflation; where the red Xs appear, inflation ends, giving rise to a hot Big Bang, but where the blue cubes persist, they continue inflating. Mathematically, in order to get enough inflation to create our Universe, you need to have inflation continue indefinitely into the future. Image credit: E. Siegel.
An illustration of eternal inflation; where the red Xs appear, inflation ends, giving rise to a hot Big Bang, but where the blue cubes persist, they continue inflating. Mathematically, in order to get enough inflation to create our Universe, you need to have inflation continue indefinitely into the future. Image credit: E. Siegel.

At the far other end of the spectrum, though, there’s the fact that our Universe’s expansion appears to be accelerating. The best explanation for this, to the greatest precision and accuracy we’ve measured it, is that there’s a small component of energy inherent to space itself: what we refer to as dark energy. This energy component is omnipresent — it exists at all locations equally in space — and it’s extremely small: if you converted it into mass via Einstein’s E = mc^2, it would only equate to one proton per cubic meter of the Universe. But space is not only very large, it’s also expanding! So as time goes on, this dark energy becomes more and more important, eventually, after some 8 billion years, causing the expansion of the Universe to accelerate and to later become the dominant component of energy in the Universe.

The four possible fates of our Universe into the future; the last one appears to be the Universe we live in, dominated by dark energy. Image credit: E. Siegel.
The four possible fates of our Universe into the future; the last one appears to be the Universe we live in, dominated by dark energy. Image credit: E. Siegel.

These two periods might seem very different: inflation and the late-time accelerated expansion. Indeed, the magnitude of these energy scales are different by about a factor of 10^120, which is tremendous! But they both represent energy inherent to space itself, they both cause the fabric of space to expand exponentially, and given enough time — fractions of a second for inflation and a trillion years for dark energy — they will take everything that isn’t bound together into a single structure in the Universe and drive it apart. There are a whole class of models out there, known generically as quintessence, that seek to unify inflation and dark energy.

So what are the possibilities for our Universe to recycle itself? There are two good ones.

The different ways dark energy could evolve into the future. Remaining constant or increasing in strength (into a Big Rip) could potentially rejuvenate the Universe. Image credit: NASA/CXC/M.Weiss.
The different ways dark energy could evolve into the future. Remaining constant or increasing in strength (into a Big Rip) could potentially rejuvenate the Universe. Image credit: NASA/CXC/M.Weiss.

1.) If dark energy is truly a cosmological constant, it might be the leftover, relic energy from the inflationary period that started it all. And if that’s the case, there’s no reason why, given enough time, it couldn’t further decay to a much lower energy state! Perhaps that transition will give rise to a large number of extremely low-mass particles, like neutrinos, axions or something even more exotic, that may yet bind together to form their own analogues to stars, planets or even humans on long enough timescales. Just because it isn’t really accessible to us doesn’t mean it isn’t possible, and it’s one potential fate for the very long-term future of our Universe, even if it takes googols of years to occur.

2.) Dark energy may not be a cosmological constant, but may actually increase in strength over time. If it does, then it will continue to rise and rise, potentially leading to a “big rip” scenario where every bound structure in the Universe eventually tears itself apart. But under a scenario developed by Eric Gawiser, it’s possible that right at the final moment — just before space itself rips into oblivion — that energy inherent to space, which would be indistinguishible from inflationary scenarios, transitions… into a hot Big Bang! This “rejuvenated Universe” scenario may not only be in our far future, but it could make our Universe much older than it appears, possibly even infinitely old.
Right now, the best evidence we have points towards dark energy truly being a cosmological constant, meaning that scenario #2 is out. If there is no lower-energy state for it to transition to, then scenario #1 is out as well, but we don’t know enough to rule either one of them out for now. If I had to bet, I’d say the lower-energy transition is more likely, but the idea that dark energy is truly a constant that exists for an eternity is better supported by the data we have available. But until we know for sure, we have to keep our minds open to all possibilities! The EUCLID mission, NASA’s WFIRST and finally the LSST will help us measure dark energy to an even better precision, which should turn up evidence either for or against the latter of these two possibilities, while developments in theoretical high-energy physics may tell us more about the possibility of the first. No matter what, the answer to your question, Andrew, is that dark energy may herald a return to a hot Big Bang from an inflation-like state, but it isn’t dependent on inflation’s eternal nature!

Submit your questions and suggestions for the next Ask Ethan here!
Astrophysicist and author Ethan Siegel is the founder and primary writer of Starts With A Bang. Follow him on Twitter, Facebook, G+, Tumblr, and order his book: Beyond The Galaxy, today!

http://www.forbes.com/sites/startswithabang/2016/03/12/ask-ethan-could-our-universe-be-a-hologram/#1a3bb1fc732b

Ethan SiegelEthan Siegel, Contributor
Image credit: Dominic Alves of flickr under a c.c.-by-2.0 license, via https://www.flickr.com/photos/dominicspics/5480234275.
Image credit: Dominic Alves of flickr under a c.c.-by-2.0 license, via https://www.flickr.com/photos/dominicspics/5480234275.

Holograms are some of the most interesting “flat” objects humans can create. By encoding a fully three-dimensional set of information onto a two-dimensional surface, holograms change their appearance accordingly as you change your perspective. Well, many extensions to our current understanding of the Universe say that our three spatial dimensions may only be the three we can perceive; there may actually be more than that. Furthermore, there’s the tantalizing possibility that we may actually be that holographic projection of a higher-dimensional Universe, from a particular perspective. Reader Jim Bray wanted to know more about this, asking:

[The] Holographic Universe seems like it might explain a lot. So, assuming that the Holographic viewpoint is correct, what is the relationship between the 2D surface and the 3D manifestation? Is the common hologram at all useful in thinking about this?

We’ve all seen holograms before, but most people don’t know how they’re actually made. The science behind them is nothing short of fascinating.

Image credit: laboratory setup of the creation of a hologram, via Epzcaw of Wikimedia Commons, under a c.c.a.-3.0 unported license.
Image credit: laboratory setup of the creation of a hologram, via Epzcaw of Wikimedia Commons, under a c.c.a.-3.0 unported license.

Photographs are simple enough: you take light that’s emitted or reflected from an object, focus it through a lens, and record it on a flat surface. That’s not only how photography works, it’s also the science behind what your eyes see at any given instant: the lens in your eyeball focuses the light, and the rods and cones on the back of your eye record it, sending it to your brain which processes it into an image.

But by using a special emulsion and coherent (e.g., laser) light, you can instead create a map of the entire light field from an object, which is what a hologram is. The variations in density, textures, opacity and more can all be faithfully recorded. When that flat, two-dimensional map is properly illuminated, it displays the full suite of three-dimensional information that can be gleaned from your perspective, but the amazing part is that it does it for every possible perspective that you can view it from. Print it onto a metallic film, and you’ve got yourself a conventional, common hologram.

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Now, our Universe as we actually perceive it has three spatial dimensions accessible to us. But what if there are fundamentally more than that? Just like a common hologram is a two-dimensional surface that encodes the full suite of information about our three-dimensional Universe, could our three-dimensional Universe encode information about a fundamentally four-or-higher-dimensional reality that we’re embedded in? It could, and there are some fun possibilities that emerge, but those possibilities also have limits to them that are important to understand.

The idea that our Universe might be a hologram came out of the conception of String Theory. String Theory grew from a proposal — the string model — to explain the strong interactions, as the insides of protons, neutrons and other baryons (and mesons) were known to have a composite structure. It gave a whole bunch of nonsensical predictions, though, that didn’t correspond to experiments, including the existence of a spin-2 particle. But people recognized if you took that energy scale way up, towards the Planck scale, the string framework could unify the known fundamental forces with gravity, and thus String Theory was born. A feature (or flaw, depending on how you look at it) of this attempt at a “holy grail” of physics is that it absolutely requires a large number of extra dimensions. So a big question then becomes how do we get our Universe, which has just three spatial dimensions, out of a theory that gives us many others? And which string theory, since there are many possible realizations of string theory, is the right one?

Image credit: David Trowbridge of flickr, under c.c.-by-s.a.-2.0, via https://www.flickr.com/photos/davidtrowbridge/528769754.
Image credit: David Trowbridge of flickr, under c.c.-by-s.a.-2.0, via https://www.flickr.com/photos/davidtrowbridge/528769754.

Perhaps, the realization goes, the many different string theory models and scenarios that are out there are actually all different aspects of the same fundamental theory, seen from a different point of view. In mathematics, two systems that are equivalent to one another are known as “dual,” and one surprising discovery that’s related to a hologram is that sometimes two systems that are dual to one another have different numbers of dimensions. The reason physicists get very excited about this is that in 1997, physicist Juan Maldacena proposed the AdS/CFT correspondence, which claimed that our three dimensional (plus time) Universe, with its quantum field theories describing elementary particles and their interactions, was dual to a higher-dimensional spacetime (anti-de Sitter space) that plays a role in quantum theories of gravity.

Image credit: Alex Dunkel (Maky) and Polytope24 of wikimedia commons, under a c.c.a.-by-s.a.-3.0, of the AdS/CFT correspondence between the interior volume and the boundary of the surface enclosing it.

Now, so far, the only dualities we’ve ever discovered relate the properties of the higher-dimensional space to its lower-dimensional boundary: a reduction in dimension by one. It’s not yet clear whether we can go from, say, a ten-dimensional String Theory to a three-dimensional Universe like our own and have them be dual to one another. The two-dimensional holograms we can create encode only three-dimensional information; we can’t encode four-dimensional information in a two-dimensional hologram, nor can we encode our three-dimensional Universe down onto one-dimension.

Image credit: flickr user Kevin Gill, of a hologram of Earth under c.c.-by-2.0. Via https://www.flickr.com/photos/kevinmgill/14676390490.
Image credit: flickr user Kevin Gill, of a hologram of Earth under c.c.-by-2.0. Via https://www.flickr.com/photos/kevinmgill/14676390490.

Another reason that two spaces of different dimensions being dual is interesting is the following: there’s less information available on a lower-dimensional boundary of a surface than inside the volume of the full space enclosed by the surface. So if you can measure something happening on the surface, you may learn more than one thing about what’s going on inside the volume. The configurations about what’s happening in the larger-dimensional space may be related to what’s going on at other locations, rather than independently. This might sound “unreal,” but perhaps it makes some sense if you think about quantum entanglement, and how measuring the property of one member of the entangled system instantaneously tells you information about the other. It’s possible that holography is related to this quirk of nature.

Image credit: screenshot from YouTube user StarGazer, via https://www.youtube.com/channel/UCuE22KuJhcIRyeTx8Yp1rBQ.
Image credit: screenshot from YouTube user StarGazer, via https://www.youtube.com/channel/UCuE22KuJhcIRyeTx8Yp1rBQ.

Duality is a mathematical fact, and an intriguing physical possibility. Will it eventually lead to deep insights in allowing us to better understand our own Universe? Perhaps, but so far we aren’t sure how far its applications apply, and whether it will provide the connection from gauge theory to quantum gravity that we all desire. But that’s the ultimate hope. If the Universe truly is a hologram, that’s what the greatest of implications really are!

Submit your questions and suggestions for the next Ask Ethan here!
Astrophysicist and author Ethan Siegel is the founder and primary writer of Starts With A Bang. Follow him on Twitter, Facebook, G+, Tumblr, and order his book: Beyond The Galaxy, today!

http://backreaction.blogspot.de/2016/03/dear-dr-b-what-is-difference-between.html

http://www.forbes.com/sites/startswithabang/2016/03/15/10-quantum-truths-about-our-universe/#48f125aa4642

David Hurn 16 days ago
Do you totaly dissmiss the idea that the cat is dead and alive in different quantum universes?
Top CommentREPLYFlagPermalink
Starts With A BangAUTHOR
Starts With A Bang 15 days ago
That is one potential interpretation that is also consistent with the rules of quantum mechanics, but only if the cat and the atom are sufficiently entangled.

http://www.forbes.com/sites/stevemorgan/2016/03/30/john-mcafee-fbi-knew-all-along-they-could-unlock-an-iphone-with-cellebrites-ufed-touch/#15e35aba368c

Cybersecurity legend and Libertarian candidate John McAfee says the FBI unlocked the San Bernardino iPhone using a device that the FBI had in their possession since 2013.

According to McAfee, the FBI signed a sole source contract with Cellebrite in the Summer of 2013 to provide forensic devices for analyses of smart phones and mobile devices.

The device used is called the UFED Touch.

Why would the FBI bother to get caught up in a battle with Apple AAPL +0.06% if they already had a solution to unlock the iPhone? McAfee says the FBI was less interested in Apple than it was in precedent. If it won against Apple, then it could go to Google GOOGL +0.01% and get a master key into Android — which has 91% of the world market. A software master key — which costs nothing, can be given to every agent in the DOJ for free. The Cellebrite devices costs thousands of dollars per unit — way above the DOJ budget for everyday use.

McAfee told several media outlets over the past two weeks that he knows who is helping the FBI to hack into the San Bernadino iPhone — but he would not reveal it was Cellebrite until today. When asked how he knew about Cellebrite’s agreement with the FBI, McAfee declined to give his sources.

Who is Cellebrite and what is the UFED Touch?

Cellebrite, headquartered in Petah Tikva, Israel — with its North American office in Parsippany, New Jersey — is a global company known for its breakthroughs in mobile data technology, delivering comprehensive solutions for mobile forensics and mobile lifecycle management.

Cellebrite mobile forensics solutions give access to and unlock the intelligence of mobile data sources to extend investigative capabilities, accelerate investigations, unify investigative teams and produce solid evidence.

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UFED Touch is a comprehensive, standalone mobile forensic extraction device that combines outstanding mobile device support with unrivaled data extraction technology. With its intuitive GUI and easy-to-use touch screen, the UFED Touch enables physical, file system, and logical extractions of all data and passwords, included deleted data, from the widest range of mobile devices.

Cellebrite’s own phones are probably ringing off the hook now.

Visit SteveOnCyber.com to read all of my blogs and articles covering cybersecurity.

Follow me on Twitter @CybersecuritySF or connect with me on LinkedIn. Send story tips, feedback, and suggestions to me here.

http://www.forbes.com/sites/insertcoin/2016/03/31/dont-fight-for-the-rights-of-overwatchs-tracer-but-fail-to-defend-real-life-women/#276ae1126085

http://scienceblogs.com/startswithabang/2016/03/27/comments-of-two-weeks-103-from-the-universe-as-a-hologram-to-dark-matter-in-galaxies/

http://arxiv.org/abs/1505.07489

omments

#1
Ken Ziebarth

United States
May 26, 2015
The one I like is sweeping your laser pointer across the moon. The edge of its beam moves across the lunar surface faster than c!

#2
Sinisa Lazarek

May 26, 2015
@ Ken
in that scenario nothing actually moves. The spot from a laser is not a material object, and the photons themselves that make it and your eye perceives, don’t move faster then c.

#3
Michael Kelsey

SLAC National Accelerator Laboratory
May 26, 2015
@Sinisa #2: I think Ken knows that. The edge of the beam isn’t an object, and the FTL movement at the lunar surface can’t be used for FTL communication. Ethan had a guest post on exactly this topic a month or two ago, if I recall correctly.

#4
PJ

Perth, west Oz
May 26, 2015
Would this also depend on the rate of the sweep? If the laser is a diode (ie; not pulsed), the photons are going to arrive at the moons surface (average) 1.28 seconds after leaving the laser. If the sweep is very slow compared to the moons half degree apparent width, it would be less than C. Even if the sweep was (faster than C), some of the photons are still going to arrive 1.28 seconds after their departure

#5
Sinisa Lazarek

May 27, 2015
@ Michael

Don’t know what Ken knows or not. As for guest post.. i know, i was here.. lot of misleading info in that guest post.

#6
DJ

May 27, 2015
I’m curious about that entangling thing. There’s no way to send information based on what state it ends up in, but is there a way to send information based on the fact that a state has been read, ignoring the state itself? Like, when you measure one particle, is there any way for the other side to know THAT you measured it, that “their” side just got “locked”, by making some sort of device that responds when it gets locked?

#7
Sean T

May 27, 2015
DJ,

I must confess that QM is confusing to me, so I may be wrong here. However, I don’t believe that there is any way for an observer working with one member of an entangled particle pair to know that the other member of the pair has been measured short of actually communicating with the person doing the measuring on the other particle. If you have one member of an entangled pair and you measure some attribute of it, you would notice absolutely nothing out of the ordinary. For example, if you measure the spin of an electron about some axis, you get either +1/2 or -1/2. Nothing about that measurement indicates entanglement. Even if you communicated your result with your partner, (who would say he/she got the opposite value), that would not really be conclusive evidence that your particles were really entangled. You could measure a pair of non-entangled electrons and get opposite results by chance. (50% probability of that occurring in fact). To really detect anything strange, you’d need to measure a large number of electron spins. If you measured 20 of them, for example, you’d get some string of + and – values, occurring randomly. You would not notice anything until your partner gave you his/her values. If you find that your partner measured the opposite value for all 20 measurements, you now are fairly confident that you were measuring entangled pairs since there is only a (1/2)^20 probability of that occurring by chance. That is a bit less than a 1 in a million probability, so it’s very likely you have entangled pairs.

The key point is, though, that you really only can detect anything strange happening after the fact. You can’t look at the measurements and conclude anything about the other member of the pair. In particular, you generate a random string of values whether you go first or your partner does. The second set of measurements, looked at in isolation, is just as random as the first. It’s like looking at a series of coin flips and seeing HTTHHHTHTHTH. If you saw that sequence, you would have no reason to believe it’s not a random sequence. If you saw THHTTTHTHTHT, you likewise would not think anything of it. It’s only when you compare the two after the fact that you’d notice anything non-random about the situation.

#8
Sinisa Lazarek

May 27, 2015
@ DJ

Einstein had a bit of a naive representation about entanglement, but for this is purpose it is good. In short..he said.. imagine you had a socks in a drawer .. and there’s a red one and a yellow one.. i.e spin up and spin down of entangled particles… if you take a sock and you see it’s red. you know that there’s a yellow one in the drawer.. same thing for entangled particles.. if you have an entangled pair and you measure one particle.. you.. and only you know the state of the other particle.. but there’s not much you can do with that info. You don’t affect the state of the other particle…. you just measure… the states were defined at the moment of entanglement.

#9
Russell Seitz

May 27, 2015
You see superluminal red light every time you look at the world through a glass window with less than perfectly parallel surfaces – the dispersion of its refractive index with wavelength means the red light in the scene propagates faster then the blue light.

#10
Denier

United States
May 27, 2015
I scoff at the petty FTL imitators. The true King of FTL is the off-shell virtual photon. The virtual photon can create a link between point A and point B instantly. This is no slowpoke tachyon which takes time to travel from here to here. How pedestrian. The virtual photon’s entire plane wave is created at the same time and is completed in under Planck time.

So you have a laser pointer aimed at the moon? Bwahahahah. I’ll bet that old thing uses batteries. Not so with the virtual photon. The virtual photon links two points in space, faster than light could traverse the distance, and borrows all of its energy from space-time. No external power source needed.

Although the virtual photon is bound by perturbation theory, it is completely exempt from the conservation of energy, obviously exempt from 186,000 mph speed limits, and exempt from Special Relativity. The off-shell virtual photon is too cool for school.

All hail the King!

#11
Wow

May 28, 2015
“The virtual photon can create a link between point A and point B instantly. ”

We’ve been there before.

No, it doesn’t.

You didn’t listen at all last time, and I’m not expecting any different here.

#12
Denier

United States
May 28, 2015
@Wow #11

Of course it doesn’t. It isn’t a real thing. What dark matter is to gravity, and dark energy is to cosmic expansion, virtual particles are to subatomic processes. A virtual photon connects two points only as fast as a physicist can draw the wavy line on a Feynman diagram. In the real world it isn’t real. The processes are real. The math describing the properties of the force carriers are real, but until they figure out sting theory, or loop quantum gravity, or however the universe actually works on the smallest scales, there remain some unknown areas of exactly how the communication works.

Those unknown areas are precisely what allows the V-I-R-T-U-A-L particle to do nonsensical stuff, because the nonsensical stuff isn’t mathematically ruled out. That includes faster than light travel. If you look up almost any collection of possible FTL travel or communication (like here, or here), virtual particles are listed.

If you continue to cling so desperately to the concept of virtual photons as bullets of matter flying around instead of the mathematical placeholders they are, then I say run with it. Cross the universe faster than a speeding laser pointer.

#13
Wow

May 28, 2015
“Of course it doesn’t.

Then why did you say it did????

What dark matter is to gravity, and dark energy is to cosmic expansion, virtual particles are to subatomic processes.

No it isn’t. All they have in common (which so many other things do: people can be quite inventive) is that many people don’t understand but feel this should be no impediment on making claims about it.

Those unknown areas are precisely what allows the V-I-R-T-U-A-L particle to do nonsensical stuff

It’s only nonsensical if you make up what they “are doing” out of thin air and hope and make out that this is what they are doing.

If you continue to cling so desperately to the concept of virtual photons as bullets of matter flying around instead of the mathematical placeholders they are

They aren’t either bullets (I certainly don’t call them that) nor are they mathematical placeholders.

Or, at the most generous disposition toward your ludicrous claim, that is definitely not a settled issue. Some theories for dark matter propose a change to the form of newtonian mechanics, but there aren’t many usable theories that manage it, unless they are only a small part of the reality, meaning that dark matter as ordinary matter, not a mathematical placeholder.

They are a *mnemonic* placeholder. Like “thingy”. A meta-syntatic variable. A placeholder for some thing that will be properly described, in the same way as electrons are described.

#14
Rose

May 28, 2015
I look forward to seeing your plans for a perpetual motion machine.

#15
em

sf
May 28, 2015
crappy article. imprecise on so many points.

#16
Michael Kelsey

SLAC National Accelerator Laboratory
May 29, 2015
Ethan et al., there’s a really cool preprint out which analyzes, in a very simple special relativistic structure, superluminal travel and closed timelike curves: http://arxiv.org/abs/1505.07489.

The math is quite straightforward algebra, and the authors construct their scenarios in a reasonable way (similar to most undergraduate relativity courses) to avoid “infinite energy” concerns.

I found it quite enlightening, and gratifying, to see actual worked-out examples for the trope that superluminal motion is equivalent to time travel. It turns out that is true, but only for particular regimes of superluminal speeds.

#17
Alexander Roth

MA
March 29, 2016
This was a good review of some super-lumic examples but a little short on practical applications.

Is it possible to PROVE that light speed, “c”, is the ultimate speed? It can certainly be demonstrated that by assuming a signal speed greater than c unacceptable paradoxes and violations of causality result.

But is there a direct physical proof of the speed limit? Depending only on paradoxes weakens the argument.

Basic to special relativity is the idea that there is no special frame of reference. Does this carry over into the universe at large? From any point in the universe we can measure the sum of the vector velocities to a large number of galaxies. If the measurement is other than zero, we can adjust our velocity to make it so. Have we not thereby found a special frame? We can also deduce the Hubble constant by noting the galaxy velocities vs distance. The Hubble constant thus derived gives us the age of the universe as the time since the big bang, TBB. This process, finding the special frame and the absolute TBB gives us points of absolute time and space as we wander around the universe. Of course the special frames vary smoothly as one changes position.

In this view, accepting the existence of special frames, paradox analysis becomes a little different. It can be shown that an infinitely fast signal, IFL, under the right conditions, will definitely not lead to a paradox. Is that enough to provide some hope of very distant high speed communication? See my web essay at Fermisquestion(dot)com and note the subsection “Instantaneous Communication”.

#18
Sean T

March 30, 2016
There is experimental evidence that relativity with it’s maximum speed is a better description of the universe than classical mechanics, which lacks any maximum speed. Consider this experiment: electrons are accelerated through a known potential difference. They are then detected by two separate detectors with a known spatial separation. This setup allows the energy and velocity of the electrons to be determined.

Now plot the velocity against the energy. Classical mechanics says K = 1/2 mv^2. Therefore this plot, assuming CM is right, should look like a parabola with velocity increasing without limit as energy increases. This experiment has been performed, but the result is completely different. The plot is not a parabola and velocity does not increase without limit as energy invreases. Instead, the velocity approaches c assymptotically as energy increases, exactly as predicted by relativity and confirming the maximum speed limit.

transmission wavelength of different stellar spectral classes

#19
what is the predominant transmission wavelength of different spectral classes of stars
http://www.skyatnightmagazine.com/review/camera/meade-dsi-pro-ii
http://astro.unl.edu/naap/hr/hr_background1.html

http://www.clarkvision.com/articles/night.and.low.light.photography/
Wowhttp://www.clarkvision.com/articles/night.and.low.light.photography/
http://www.clarkvision.com/articles/digital.sensor.performance.summary/#read_noise

http://scienceblogs.com/startswithabang/2008/02/04/faster-than-light-travel-is-it-possible/

http://scienceblogs.com/startswithabang/2015/03/10/photonic-booms-synopsis/

what is the predominant transmission wavelength of different spectral classes of stars
http://www.clarkvision.com/articles/color-of-stars/

http://www.clarkvision.com/articles/astrophotography.and.exposure/

View story at Medium.com

http://scienceblogs.com/startswithabang/2015/03/20/ask-ethan-80-can-space-expand-faster-than-the-speed-of-light-synopsis/

http://scienceblogs.com/startswithabang/2011/05/18/the-fun-of-going-faster-than-l/

http://scienceblogs.com/startswithabang/2013/0

4/26/the-cosmic-speed-limit/

http://scienceblogs.com/startswithabang/2011/11/18/the-new-opera-faster-than-ligh/

March 31, 2016
“But is there a direct physical proof of the speed limit? ”

You can easily prove it wrong: demonstrate something going FTL.

There was one thought that an experiment had, but it turned out to be a machine error.

This is how you do science. Overturn accepted science WITH BETTER SCIENCE.

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http://scienceblogs.com/startswithabang/2015/05/26/how-to-travel-faster-than-light-without-really-trying-synopsis/#comment-569026

View story at Medium.com
http://scienceblogs.com/startswithabang/2008/02/04/faster-than-light-travel-is-it-possible/

http://en.wikipedia.org/wiki/Wormhole

http://en.wikipedia.org/wiki/Metric_expansion_of_space

 

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