Certain subsectors of the scientifically-oriented blogosphere are abuzz — abuzz, I say! — about this new presentation on Dark Energy at the Hubblesite. It’s slickly done, and worth checking out, although be warned that a deep voice redolent with mystery will commence speaking as soon as you open the page.
But Ryan Michney at Topography of Ignorance puts his finger on the important thing here, the opening teaser text:
Scientists have found an unexplained force that is changing our universe,
forcing galazies farther and farther apart,
stretching the very fabric of space faster and faster.
If unchecked, this mystery force could be the death of the universe,
tearing even its atoms apart.We call this force dark energy.
Scary! Also, wrong. Not the part about “tearing even its atoms apart,” an allusion to the Big Rip. That’s annoying, because a Big Rip is an extremely unlikely future for a universe even if it is dominated by dark energy, yet people can’t stop putting the idea front and center because it’s provocative. Annoying, but not wrong.
The wrong part is referring to dark energy as a “force,” which it’s not. At least since Isaac Newton, we’ve had a pretty clear idea about the distinction between “stuff” and the forces that act on that stuff. The usual story in physics is that our ideas become increasingly general and sophisticated, and distinctions that were once clear-cut might end up being altered or completely irrelevant. However, the stuff/force distinction has continued to be useful, even as relativity has broadened our definition of “stuff” to include all forms of matter and energy. Indeed, quantum field theory implies that the ingredients of a four-dimensional universe are divided neatly into two types: fermions, which cannot pile on top of each other due to the exclusion principle, and bosons, which can. That’s extremely close to the stuff/force distinction, and indeed we tend to associate the known bosonic fields — gravity, electromagnetism, gluons, and weak vector bosons — with the “forces of nature.” Personally I like to count the Higgs boson as a fifth force rather than a new matter particle, but that’s just because I’m especially fastidious. The well-defined fermion/boson distinction is not precisely equivalent to the more casual stuff/force distinction, because relativity teaches us that the bosonic “force fields” are also sources for the forces themselves. But we think we know the difference between a force and the stuff that is acting as its source.
Anyway, that last paragraph got a bit out of control, but the point remains: you have stuff, and you have forces. And dark energy is definitely “stuff.” It’s not a new force. (There might be a force associated with it, if the dark energy is a light scalar field, but that force is so weak that it’s not been detected, and certainly isn’t responsible for the acceleration of the universe.) In fact, the relevant force is a pretty old one — gravity! Cosmologists consider all kinds of crazy ideas in their efforts to account for dark energy, but in all the sensible theories I’ve heard of, it’s gravity that is the operative force. The dark energy is causing a gravitational field, and an interesting kind of field that causes distant objects to appear to accelerate away from us rather than toward us, but it’s definitely gravity that is doing the forcing here.
Is this a distinction worth making, or just something to kvetch about while we pat ourselves on the back for being smart scientists, misunderstood once again by those hacks in the PR department? I think it is worth making. One of the big obstacles to successfully explaining modern physics to a broad audience is that the English language wasn’t made with physics in mind. How could it have been, when many of the physical concepts weren’t yet invented? Sometimes we invent brand new words to describe new ideas in science, but often we re-purpose existing words to describe concepts for which they originally weren’t intended. It’s understandably confusing, and it’s the least we can do to be careful about how we use the words. One person says “there are four forces of nature…” and another says “we’ve discovered a new force, dark energy…”, and you could hardly blame someone who is paying attention for turning around and asking “Does that mean we have five forces now?” And you’d have to explain “No, we didn’t mean that…” Why not just get it right the first time?
Sometimes the re-purposed meanings are so deeply embedded that we forget they could mean anything different. Anyone who has spoken about “energy” or “dimensions” to a non-specialist audience has come across this language barrier. Just recently it was finally beaten into me how bad “dark” is for describing “dark matter” and “dark energy.” What we mean by “dark” in these cases is “completely transparent to light.” To your average non-physicist, it turns out, “dark” might mean “completely absorbs light.” Which is the opposite! Who knew? That’s why I prefer calling it “smooth tension,” which sounds more Barry White than Public Enemy.
What I would really like to get rid of is any discussion of “negative pressure.” The important thing about dark energy is that it’s persistent — the density (energy per cubic centimeter) remains roughly constant, even as the universe expands. Therefore, according to general relativity, it imparts a perpetual impulse to the expansion of the universe, not one that gradually dilutes away. A constant density leads to a constant expansion rate, which means that the time it takes the universe to double in size is a constant. But if the universe doubles in size every ten billion years or so, what we see is distant galaxies acceleratating away — first they are X parsecs away, then they are 2X parsecs away, then 4X parsecs away, then 8X, etc. The distance grows faster and faster, which we observe as acceleration.
That all makes a sort of sense, and never once did we mention “negative pressure.” But it’s nevertheless true that, in general relativity, there is a relationship between the pressure of a substance and the rate at which its density dilutes away as the universe expands: the more (positive) pressure, the faster it dilutes away. To indulge in a bit of equationry, imagine that the energy density dilutes away as a function of the scale factor as R-n. So for matter, whose density just goes down as the volume goes up, n=3. For a cosmological constant, which doesn’t dilute away at all, n=0. Now let’s call the ratio of the pressure to the density w, so that matter (which has no pressure) has w=0 and the cosmological constant (with pressure equal and opposite to its density) has w=-1. In fact, there is a perfectly lockstep relation between the two quantities:
n = 3(w + 1).
Measuring, or putting limits on, one quantity is precisely equivalent to the other; it’s just a matter of your own preferences how you might want to cast your results.
To me, the parameter n describing how the density evolves is easy to understand and has a straightforward relationship to how the universe expands, which is what we are actually measuring. The parameter w describing the relationship of pressure to energy density is a bit abstract. Certainly, if you haven’t studied general relativity, it’s not at all clear why the pressure should have anything to do with how the universe expands. (Although it does, of course; we’re not debating right and wrong, just how to most clearly translate the physics into English.) But talking about negative pressure is a quick and dirty way to convey the illusion of understanding. The usual legerdemain goes like this: “Gravity feels both energy density and pressure. So negative pressure is kind of like anti-gravity, pushing things apart rather than pulling them together.” Which is completely true, as far as it goes. But if you think about it just a little bit, you start asking what the effect of a “negative pressure” should really be. Doesn’t ordinary positive pressure, after all, tend to push things apart? So shouldn’t negative pressure pull them together? Then you have to apologize and explain that the actual force of this negative pressure can’t be felt at all, since it’s equal in magnitude in every direction, and it’s only the indirect gravitational effect of the negative pressure that is being measured. All true, but not nearly as enlightening as leaving the concept behind altogether.
But I fear we are stuck with it. Cosmologists talk about negative pressure and w all the time, even though it’s confusing and ultimately not what we are measuring anyway. Once I put into motion my nefarious scheme to overthrow the scientific establishment and have myself crowned Emperor of Cosmology, rest assured that instituting a sensible system of nomenclature will be one of my very first acts as sovereign.
Lawrence,
But light can’t go faster then the speed of light, so light falling into a gravitational well can’t go any faster, so how can its energy be increased? On the other hand, it can go slower then C, so it can be decreased.
So it seems waves and particles are both abstractions. A duality defining the deeper reality. Waves being the expanded potential and particles being the contracted focus. Both meaningless without the other.
It would seem that curvature is only detected in redshift being relative to distance. It’s curved in time, but not in space. And our ability to measure ‘time is so uncertain that it effectively does not exist.’
How can the energy of light be increased? By Doppler blue shifting of course. The energy of a photon is E = h*frequency. A higher frequency then the higher the energy.
Well, I am not going to belabor the issue of particles vs waves too much. There are some experiments which have gotten direct measurements of the modulus squared of waves. Most experiments detect a particle. Generally a particle is real valued, and is regarded as “real.” OTOH waves are complex valued and not regarded as directly real. There are all sorts of quantum interpretations, one in particular by Bohm that has a real particle “guided” by a so called pilot wave. I am not a partisan of so called interpretations.
The redshift is given by v = Hd, for H the Hubble constant, v a velocity and d a distance.
Lawrence B. Crowell
LC,
“An atemporal approach to quantum gravity is probably somewhat on the mark. Time is a curious quantity. In quantum mechanics it is regarded as conjugate or complementary to energy. Yet for those who understand classicl physics and Hamiltonian formalism there are not Poisson brackets between time and energy. Quantum mechanics exploits a Fourier relationship between frequency (or energy by E = h*freq) and time, but quantum mechanics does not define an energy operator. Time exists in a manner not entirely equivalent to spatial quantities which have a strict dual to momentum in classical mechanics.”
“Hence the relevant quantity is a fluctuation in the Newtonian force. The variation in the Newtonian force will then manifest itself as the variation in the angle of swing for the torsional balance. The energy error functional is &E_g = hbar/&T. This error functional is a measure of our “ignorance” in assigning a coordinate map between the two metrics. It also indicates a potential relationship between the uncertainty principle and spacetime physics.”
“This appears to be an indication of how one relationship system, gravity and a geometric relationship between particles, and another system of relationships, quantum mechanics and entanglements etc, are related to each other in a general relationship system. This appears to require that time be regarded as “derivative.” the energy error functional for zero energy uncertainty (a fine grained description) has the time uncertainty &T —> infinity. In other words time is so uncertain that it effectively does not exist.”
NOTE: You summarize your conceptual viewpoint on the possible relationship between GR and QM very briefly and very well. I can see that our points of view on this are much closer than I first assumed.
“As for the curvature of the early universe, if it is a sphere then at earlier epochs it has a higher radius of curvature. So as we look further out, since light travels at its locally finite speed we see earlier into time. So far the universe looks very flat, so if the universe is a sphere we see only a tiny portion of it. The inflationary period converted a region of the universe a billionth the radius of a nucleus into a meter or so in size. The curvature of the universe was drastically reduced.”
NOTE: Conceptually many people have difficulty with a universe which is eternally everywhere, and is based on invariant frames, yet potentially varies widely in spatial extent. I liked your appropriate comments about space as only existing as it relates energy densities. Understanding this fact makes it easier to conceptually internalize the axiom that nothing exists outside of a GR universe! In fact, that space is defined as a relationship between particles also must be understood as foundational to understanding the concept of space/time curvature, inertial and non-inertial motion.
Global space time in GR is spherical, however space as observed from our particulate 4D frame of reference is anything but spherical…almost flat, in fact. As energy densities have become more widely separated, and space itself more diluted to the level of the present submicroscopic Planck Realm, a CMB, space at our coordinates seems almost flat at 360 degrees.
However, a universe with both black holes and white holes can immediately be seen to complete the picture of an everywhere, eternal universe, with space varying from non-existent to spherical and then becomming almost flat…then becomming spherical and non-existing anywhere, while the universe as a whole yet continues to exist, from other frames, in reversed polarity, everywhere.
We know black holes attract energy and continue to grow in gravitational influence. That the universe emerged in a “bang” from a massive singular entity is evidence enough that white holes are a reality as well, but the overall evidence for the existence of white holes is almost as varied and rich as the evidence for black holes…photons do work; what else can they be interpereted to be? Big bang/ white hole is but a matter of scale, and observational frame.
As singular cosmological objects, entangled with the Planck Realm, continue to grow in mass and the entangled Planck Realm everywhere rises in scale, there comes an instant, after eons of “almost flat space” where and when the universe becomes, at one half of its coordinates, spherical in shape…then briefly non-existent…and re-emergent as a white hole in opposite baryonic polarity.
If we observe this process in the sub-microscopic, we can observe a rapid proper time pulse…continuous baryonic polarity reversal, which when mathematically evaluated in terms of the gravitational time dilation formula produces “space” and the sensation of the passage of “time” at our observing frame.
SR, GR and QM tie the universe together. All the formulae when taken together, provide us with a jigsaw puzzle-like description of the universe which when carefully pieced together, matches what we observe in an uncanny and incredible manner.
It just amazes me that these concepts are not really esoteric at all. We live in a continuously accelerated frame of reference on the surface of the Earth which in some key ways is much like that of an astronaut leaving the Earth in an equally continuously accelerating spaceship. What we observe as ourselves, the Earth..in fact space and time themselves are the products of relativistic and quantum relationships. From the GR perspective, our baryonic informational existence is tied to the relationships of particles and the resulting geometry of space-time.
Appreciated your remarks very much…
Lawrence,
Yes, but what is being described isn’t Doppler Effect, because the source of the light isn’t actually getting closer.
So if the particle is real and the wave is statistical, how do you impart more energy/higher frequency into the particle, other then to make it travel faster?
Sam,
So if you add more energy between points of reference, they are effectively being pushed apart and vice versa. So presumably dark energy is causing galaxies to fly away from each other. On the other hand, this expansion presumably results in increasing distance, as measured by lightspeed, so it would seem the metric of light traveling in a vacuum measures a stable dimension.
Does the fact that this energy is falling into gravitational wells balance the expansion effect?
First: When it comes to gravitational Doppler effect, as illustrated by J.M.’s question, it appears that I am having to answer the same questions over and over. I would advise looking up sources on this issue. I am sure Wikipedia might provide a first look at this.
The orgin of the universe is of course an open question in physics, and general relativity indicates a singularity as time —> 0. Of course general relativity is a classical physical theory, which has singularities and divergences which might be ameliortated by quantum mechanics. A similar situation exists with electrodynamics, and quantization removes these problems.
Feynman first proposed a path integral as a way of describing the motion of particles as traversing all possible paths. These paths were thought to “go anywhere,” such as an electron which traverses a band gap in a solid has some probable path (amplitude) for travelling to the Jurassic period, then to the M82 galaxy and then across the band gap. Feynman’s vision was not entirely fulfilled since such a general path integral involves inequivalent vacua. So the path integral had to be “tamed” with time ordering procedures and other tools, and divergences still required regularization schemes.
Quantum fields in curved spacetime exist with non-unitarily equivalent vacua. These different vacua are related to each other by Bogoliubov transformations which emerge from relativistic transformations. As a result the radiation which an accelerated observer measures and that which comes from a black hole has a thermal distribution. Again due to limitations the Rindler wedge of spacetime on an accelerated from is a Poincare half plane, which is conformally mapped to the Poincare disk. The Poincare disk is seen in the Escher prints of tilings that “pile up” near the edge of the disk. This is similar to the deSitter spacetime, or more the Anti-deSitter spacetime, which appears similar to the universe we observe and in the AdS case has a duality with quantum (conformal) fields in the spacetime.
The early universe was likely a configuration of a huge number of inequivalent vacua that were unstable. There is a framed Higgs field (the inflaton etc) which is a measure of this instability in that it will evolve to the lowest energy physical vacuum configuration locally. This is likely how the universe emerged from the vacuum (or a set of inequivalent vacua) and the increasing entropy of the universe may be a measure of a coarse graining over these inequivalent vacua.
The AdS spacetime has as its conformal infinity a Minkowski spacetime. There are subtle issues of how this can be described by the evolution of a spatial surface, which involves the matter of conformal completeness. Yet the universe does appear to be evolving to a Minkowski flat spacetime completely devoid of matter fields. The grand path integral (similar to a grand canonical partition function in stat mech) takes as its initial point in superspace a maximal configuration of inequivalent vacua and low entropy and as its final point (at infinity) as one with a singly unitary vacuum but maximal entropy.
So quantum gravity likely involves fullfilling Saint Richard’s vision of a grand path integral over all possible configuration of fields, vacua, paths and so forth in order to describe how cosmology emerges from an unstable “nothing” and approahes at conformal infinity a stable “nothing.”
Lawrence B. Crowell
Lawrence,
Sorry to have tested your patience. I thought I had a handle on how gravity redshifts light, such as that coming from the sun. Something of a drag on the frame, so to speak. It just didn’t seem to translate that the opposite effect would cause a blueshift, since the light would already be traveling at C and couldn’t be speeded up, but it doesn’t appear that the answer lays in anything resembling classical or basic relativistic physics, so I guess I better just paddle back to shore and leave it at that.
Red shift and blue shift are the same as the high pitch of an approaching sound source and the lower pitch once it receeds. If you are at the bottom of a gravity well the frequency of light will increase (wavelength decrease) before you detect it. It does not speed up. Similarly if you are looking down into a gravity well where photons are being emitted there is a redshift, the frequency decreases and the wavelength increases. Again the light does not slow down as measured in any local frame. It is important to recognize this is for local frames. So a photon that leaves the sun will be gravitationally redshifted, but if you measure its speed it is the same.
Lawrence B. Crowell
PS — I notice in the start of this with regards to sound pitch I had the high and low reversed for comparison. I should have started out with “Blue shift and red shift ….”
Lawrence,
Is the blueshift a compression factor?
You can think of it as a compression factor, though that term is not usually used. The wavelength of a photon expands or contracts in response to climbing out of a gravity field or falling into one. Similarly if the space is expanding, or points of the space are being shifted apart, the wavelength of a photon expands proportionately. The inverse is the case if the space is contracting, say if the universe were recollapsing, and photons would be blue shifted. However, that is not what is observed.
Lawrence B. Crowell
LC,
“The AdS spacetime has as its conformal infinity a Minkowski spacetime. There are subtle issues of how this can be described by the evolution of a spatial surface, which involves the matter of conformal completeness. Yet the universe does appear to be evolving to a Minkowski flat spacetime completely devoid of matter fields. The grand path integral (similar to a grand canonical partition function in stat mech) takes as its initial point in superspace a maximal configuration of inequivalent vacua and low entropy and as its final point (at infinity) as one with a singly unitary vacuum but maximal entropy.
So quantum gravity likely involves fullfilling Saint Richard’s vision of a grand path integral over all possible configuration of fields, vacua, paths and so forth in order to describe how cosmology emerges from an unstable “nothing” and approahes at conformal infinity a stable “nothing”.”
A good concise description of the evolution of the 4D model!
The discovery of black holes, acceleration “outward” and other astronomical and sub-microscopic phenomena lay the foundation for a continuing extention of this obviously incomplete conceptual paradyme. I think the first item on the agenda, even before we look at related but extended geometries and topological relationships, is to recognize that the mathematical dualism (as you mention) of both relativity and Quantum Mechanics is not vestigial…a mathematical artifact of no cosmological significance, but rather is an essential part of a viable and verifiable concept which explains not only the part of the universe we observe, but also that part, the existence is which is inferred by the field work of the past 75 years.
In my opinion, understanding the significance of quantum entanglement as a singular and photonic universal phenomenon, and establishing the connection of this “quantum reality” with the relativistic scale of time and space, are essential conceptually to a more complete understanding the atemporal nature of the cosmos and the link between the quantum/relativistic universe and its observation in space/time at an almost infinite number (variety) of interdependent levels of biological complexity and organization.
A related, and important task (as in the study of terrestrial organic evolution) is to trace the phylogenic development of the universe itself back to an archaic condition in which the inorganic complexity and behavior which underlie today’s biological complexity was much simpler than presently- and understand how the system gained in informational complexity toward the conditions we observe in this epoch.
Lawrence,
By compression, I don’t exlusively mean between waves. I mean that if space is being compressed by gravity, that this causes the distance between waves being compressed? Sort of like does the compression of longitude also compress latitude? On the other hand, it is radiation that DOES escape gravity!
Since gravity fields effectively extend halfway to the next equivalent source of gravity and most of what is affected is mass, while light radiates to the extent it is visible, which, for a galaxy is 10+billion lightyears, light is gravitationally blueshifted over a much smaller diameter, though far more intensely, than it is radiated…
My argument has been that radiation is the opposite effect of mass/gravity. That light, in all its forms, is the ‘white hole.’ That by putting energy back out into space, it effectively causes it to expand, just as gravity causes it to contract. As Sam said;
“space is defined as a relationship between particles also must be understood as foundational to understanding the concept of space/time curvature, inertial and non-inertial motion.” (substitute energy fields for particles)
…since much of what’s contracted is mass, while most of which is expanded is radiation, the redshift of light predominates over what’s blueshifted.
I know you’re probably sick of this, but from my perspective, way out here in the moon, where all the math runs together, it keeps coming around in a cycle of collapsing mass and expanding radiation. Sorry if this gets old, its just one of those simple patterns for simple minds.
Think of Doppler shifting like this. If you have a unit cube of volume then on average for every photon that leave it one comes in. So we can think of the cube as a resonance cavity for electromagnetic radiation, such as with a microwave oven. Now if the space evolves so that the volume changes in a homegenous manner (not like a Kasner spacetime) then the standing waves of electromagnetic radiation are stretched or shrunk with expansion or contraction of the volume.
A spherical shell of dust that falls to a gravitating body will become distended into a prolate ellipsoid. This is because the part of the shell closest to the gravitating body is under a larger gravity force. This is a way to think about tides. So as the spherical shell gets distended into a cigar shape along the radial direction of fall, we can think also of this as being an electromagnetic reonance cavity. If you are in this volume, freely falling with this reference frame, you would then witness a redshifting of light from other falling sources along the radial direction. Yet, just as the spherical shell is constricting into a cigar shape you would see radiation on a plane perpendicular to the radius a blue shifting of light from objects coming towards you.
There are a number of configurations one can consider.
Lawrence B. Crowell
Lawrence,
So it would seem that from the perspective of being in the falling volume, the longitudal lines are blueshifted, but the latitudal lines are redshifted?
The question then, for an observer at the bottom of the gravity well, it would seem these waves would be distended and redshifted, since the earlier waves get pulled in at an accelerated rate? It seems that from this explanation, of an elongated volume, it would be redshifted, since the distance between latitudal waves is stretched?
Also I’m still having problems with C constraining this, since the light is presumably traveling at C. If the “objects coming towards you,” is light itself, how can the ‘light’ from it be blueshifted?
Again think of the spherical cloud of particles or “dust” falling radially inward towards a gravitating body. Since the spherical cloud has a spatial extent it may not be a pure local inertial frame. The local inertial frame is an infintesimal ideal, which is physically approximate for reference frames defined on a small enough of a scale. The particles in this spherical cloud will then fall along slightly different geodesics. From a Newtonian perspective the particles closest to the body along a radial direction have a slightly larger gravitating force than particles furthest away. As such these particles will separate with a relative acceleration. Particles along an “equator” defined by these two points as the “poles” will have accelerations that are along slightly different radial directions. These particles
Think of youself are at the center of the spherical cloud of particles. You along with this cloud are falling towards a gravitating body. The particles along the radial direction of fall will in your frame be seen to accelerate in opposite directions away from you. Conversely particles on a plane prependicular to the radial direction of fall will in your frame be seen to accelerate towards you.
Now suppose these particles emit some known wavelength of radiation. The particles on the antipodal points along the radial direction will emit photons you measure as redshifted, while the particles on the perpedicular plane will emit photons you measure as blue shifted. Further since these particles are accelerating away or towards you this red and blue shifting will increase. If the gravitating body is a black hole this Doppler shifting will diverge.
If the universe were a black hole we would observe this sort of anisotropic distribution in Doppler shifts. Of course we don’t observe this, which is why the universe is different from a black hole.
Lawrence B. Crowell
erratum: I ended the first paragraph with : These particles
I meant to write:
These particles will accelerate towards each other and towards the observer.
I got distracted and forgot to conclude the paragraph.
“Now suppose these particles emit some known wavelength of radiation. The particles on the antipodal points along the radial direction will emit photons you measure as redshifted, while the particles on the perpedicular plane will emit photons you measure as blue shifted. Further since these particles are accelerating away or towards you this red and blue shifting will increase. If the gravitating body is a black hole this Doppler shifting will diverge.
If the universe were a black hole we would observe this sort of anisotropic distribution in Doppler shifts. Of course we don’t observe this, which is why the universe is different from a black hole.”
Excellent point. Some on the fringe have attempted to conceptualize the universe as a black hole and have even insisted we live inside a blsck hole…completely bizzare- and not supported by field observations either. It is one thing to assert that by definition the universe everywhere is (and must be) singular below a certain level of scale. It is quite another to assert we live inside a black hole!
The nature of the Hubble function, the uniformity of the cosmological redshift with observed distance, the acceleration of the universe outward, a measured Omega total of 1.02…all these observations and many others including the existence and behavior of black holes, imply a geometry for the cosmos which is at least based on Einsteins original local Euclidean SR and global GR spherical concept.
It is highly unlikely the universe we live in originated as the technology of a pre-existing outside intelligence. First, there is nothing outside this kind of universe anyway. Second, the way informational complexity is organized and interacts implies that the development of informational complexity in the universe is a continuing and (in some ways) quite irregular process which occurs within a set of implicit cosmic constraints, for example, mass and spatial extent.
The question: “Where did the cosmic constraints and orginal energy come from?” is not valid. A preqequisite for the continuing evolution of this kind of universe…finite in mass and spatial extent is that it must be eternal…infinite along the time dimension. If it has always existed, it “just is”. This axiom of existence can be further understood as we note the atemporal connection between existence and observation.
Of course, all this does not preclude a developing, profound, relating process within the universe itself which in fact, is somewhat implied by entanglement at singular and photonic scales. We definitely live in a universe where there is a place for everything and everything is in its place. Rather than saying time is an illusion, perhaps it should be said that time make the universe observable- and is the way it is possible to physically experience existence in this kind of reality. Subtract time, spacelike or time like and we bo longer have a cosmological concept, nor can we exist as we are.
Lawrence,
I get what you are saying here, but it still raises the two issues I mentioned; From the perspective of an observer on the surface of that gravitational body, the approaching light isn’t blueshifted because it is traveling at the speed of light in the first place. In terms of Doppler Effect, it would be as if the train were traveling at the speed of sound. The whistle wouldn’t be pitched higher, because you wouldn’t be able to hear it until the train passed and all the waves hit at once, creating a sonic boom.
Now as you described it, since the gravity is stronger for the preceding wave/particles, then for the succeeding ones, it actually stretches the frequency out on the radial, as it compresses their energy perpendicular to the radial. So it would seem to actually redshift them as they pass this observer on the surface of the gravitational body.
Since gravitational lensing magnifies light, it would seem logical that this would be caused by the perpendicular compression.
The description of redshift from comoving particles surrounding an infalling observer was given as way of demonstration. As for JM, the redshift as observed by an infalling observer obtains for that observer’s inertial frame. An observer on the surface of the gravitating body is on a different frame. Thus to compare directly the redshift/blueshift results of the infalling observer with what this observer would measure is wrong. Also, this has nothing to do with any speeding up of light or photons moving faster or slower, at least as measured in any local frame.
A comparison with Doppler shift of sound is only approximate for slow velocities. For large velocities there are Lorentz factors which enter into the picture. In the case of cosmology there are then also metric/curvature terms to consider as well. In the case of light the speed of light locally is an absolute invariant.
The redshift of galaxies in the universe is pretty isotropic, as is the cosmic microwave background, and so we can pretty safely conclude the whole universe is not a spacetime containing a black hole.
As to how particle masses and the strength of gauge fields are obtained has a bit to do with inflationary cosmology. One of the curious results of this is that the universe we observe may only be about one part in about 10^{50} of the whole thing. Without inflation everything in the universe would be causally connected more tightly. The inflaton, or Higgs-like particle that induced inflation, expanded rapidly across the cosmological horizon to determine the curvature of the universe and the nature of gauge fields and their fermionic sources on a spatial surface not causally connected to the same initial conditions. This opens a lot of questions on how the cosmos was determined with a single structure. Some such as Linde and Vilenkin have proposed bubbles of different vacua that determine different particle masses. This is given by Yukawa lagraingian terms L_y = psi-bar H psi, and if the Higgs or inflaton field H settles into different configurations on the degenerate physical vacua then H —> will differ.
An interesting note is that the Relativistic High-energy Ion Collider at Brookhaven has found the large “blobs” of excited particles can be modelled as a sort of black hole. This machine slams heavy ions together which generates high energy “plasmas” of quarks, gluons, leptons and a gemish of other gauge particles. This then energetically fly apart and the decay products measured by hadron calorimeters and other detectors. It turns out this has a black hole-like behavior. I have been working on similar physics with what I call gauge-holes (which is what I call these) in Anti-deSitter spacetimes. This gets into the AdS/CFT Maldecana duality, but there should have existed black hole-like field configurations in the early universe that result in conformal completeness of the AdS. This gets into some rather subtle issues with AdS spacetimes and cosmology. Yet it turns out that the cosmic microwave background has some “textures” which appear to be defects that might be due to cosmic strings. I think these are the result of gauge-holes which were inflated into a large scale.
Lawrence B. Crowell
Lawrence,
My little mind can only take in small parts of the picture at a time. I’m still just trying to figure out how light is blueshifted by falling into a gravity well, as it is redshifted by climbing out of it. As you have described it, it would seem to be reshifted by the gravity pulling it in and stretching the “volume.” Am I correct in assuming this volume is the trough between waves?
That it does this by compressing them perpendicular to the line of radiation would seem to explain the magnification/focusing of gravitational lensing.
This is over-reach, but it would explain this point raised by Sam;
Since the further light travels, the more residual gravity fields it passes through. If they both magnify and redshift light, then the more distant galaxies might be much further then we assume, but their light is being magnified and focused, so they appear closer and clearer then they would over the same distance of completely empty space, but redshifted, so they appear to be moving away at an accelerated rate.
Don’t include me with those who think the universe is in a black hole. Black holes are a projection of gravitational effects to infinity. As I see it, gravity is one side of a cycle, where mass/gravity is constantly curving back out as radiating energy, not collapsing into infinity.
LC,
“The redshift of galaxies in the universe is pretty isotropic, as is the cosmic microwave background, and so we can pretty safely conclude the whole universe is not a spacetime containing a black hole.”
This thread is quite amazing! Usually before a thread goes 50 posts, people are discussing everything except the original topic and its implications!
1. The universe contains not one black hole but n…don’t ask me how many!
2. The “empty” universe model has be shown to be “flat” (a little play on words) incorrrect to a high degree of certainty, anyway.
3. Particulate matter exists on 4D event horizon surfaces in the sub-microscopic…that is where baryonic matter forms and exists according to the general mathematical parameters of SR, QM and GR.
4. There IS “extra mass” in the space of the solar system. Technological explanations for the anomolous acceleration of the Pioneer spacecraft have been pretty much eliminated.
5. Remember, according to the standard model, the mass of the universe is constrained by a certain, very particular density. So long as we theoretically accept the concept of a universe which is finite in mass, we can make it as massive as we wish, and still be within the parameters of the standard model, however, a universe which is 10 to the n (th) power greater than what is observable is a bit out of line with a universe which exists only as it is observed and measured. The geometry gets a bit out of line with spherical space in GR. Hyperbolic space can of course be closed, and would be expected to exist locally in a GR universe, however to assume space in the entire universe is hyperbolic is not consistent with an omega total of 1.02 either!
Best Wishes!…it has been very interesting following the development of this thread…..
Another very important point or two…
The age of the universe has been determined to a high degree of precision…about 13.7 billion years. Everywhere we observe outward, astronomically, the universe cumulatively becomes singular at 13.7 billion light years distant…space and time cease to exist anywhere and everywhere at that distance…there IS no universe as we understand it…only energy.
Although this fact by itself does not put a “lid” on the mass of the universe, it serves as a reminder and important parameter in determining the necessary limits of the universe. The most recent work I have seen is pretty consistent in deriving a universal mass of about 10 to the 60th Kg.
All the professional speculation about parallel universes, multi-verses, an infinity of universes…etc is fascinating but remains speculation.
Some of these ideas at least, are principally intended to explain the existence of universal information and complexity using infinities and probablilities, and since only one infinity (eternity) and certain fundamental universal parameters can also explain complexity in a vast universe of finite mass and limited spatial extent, it is hard to see how such radical speculation is really necessary. Most of those who propose these ideas readily admit they are probably not falsifiable- or provable. Max Tegmark for one is very open about this, and freely discusses the important “caveat’s” involved in the multi-verse idea.
Sam,
The line between knowledge and speculation is always a little fuzzy, but when it gets as fuzzy as current physics and cosmology would have it, it’s possibly due to some earlier speculation being incorporated as knowledge and throwing subsequent investigation off course.
I’m currently reading a Christmas gift called Aristotle’s Children, by Richard Rubenstein. It’s about the reintroduction of the works of Aristotle and other Greek philosophers, as well as centuries of Jewish and Muslim commentary, with the reconquest of Spain in the early part of the last millenium. Because they took these early explorations as fact, rather then speculation, much chaos eventually worked its way into the established assumptions. Epi-cycles being the most obvious. I think we may also be at a late stage of the current cycle, where the speculation becomes increasingly fantastical, before it finally breaks down.
The entire universe might actually be a grand nothingness. If one considers gravity wells as having negative potential energy and one then does an approximate sum over all energy and mass equivalent it may be be grand zero, as with Tolman’s thesis. Of course there are subtle issues of there being no time like Killing vector that projects onto the portion of a spacetime momentum 4-vector to give a constant energy. Yet this may also be telling us that globally energy is not defined, and that on a grand cosmological scale to say that the universe has a mass-energy is meaningless.
If one things about it there is no way one can step out of the universe and place it on a scale. Weight is a measure of a force that resists geodesic motion in spacetime, but “outside of the universe,” if such has any meaning, there is no spacetime, thus no geodesic motion, curvatures, gravity or — anything.
As for black holes, an early idea was that the universe was a spacetime with a giant black hole or a Schwarzschild spacetime. This black hole would have been a thundering thing weighting in at a mass greater than all observed galaxies. The entire universe is not such a thing. The vacuum solution for the black hole, before it was even called a black hole, had a symmetrical part that connected a cosmological patch’s conformal past infinity to a singuarity for a white hole. The white hole gives way to a black hole that connects up to the spacetime’s conformal future infinity. Some early ideas had the white hole part as some sort of creation field and the black hole as the recollapsing destruction field. The idea has passed into non-physics as the white hole portion is seen as a mathematical fiction of sorts.
Clear the universe contains black holes, and an average galaxy probably harbors many thousands or millions of them. They often have a very large one at their centers. The CMB of the universe contains anisotropies which were the seeds for matter clumping that lead to the formation of proto-galaxies and the earliest stars. These then may have lead to the formation of black holes early on. I think that the “texture,” in the CMB recently discovered are the result of a black hole-like object formed by gauge charges. This is called black hole-like, for in pure spacetime it is not a black hole, but in extended dimensions (eg 5-dim for AdS or 10-11 in supergravity) it has a guage charged induced horizon. This horizon forms IMO a conformal completeness on the AdS, which is tied to AdS/CFT duality. This object during inflation is stretched into a cosmic string, possibly tied to a black hole. There may have been a number of these objects in the early universe. A finer observation of the CMB might reveal 4-th order deviations (beyond second order standard deviations) in the CMB which point to a distribution of these strange objects.
The RHIC has found that heavy ions in high energy collisions have a black hole-like physics. It may well be that what is a black hole and what is not has a “fuzzy” quantum mechanical distinction. These RHIC objects, blobs at high energy for a 10^{-20}sec or so, might have some tiny quantum amplitude for being black holes, or gauge holes.
Lawrence B. Crowell
Here is an interesting article in today’s NYTimes, business section, that makes the basic psychological point I think physics and cosmology will have to eventually face; http://www.nytimes.com/2007/12/30/business/30know.html
IT’S a pickle of a paradox: As our knowledge and expertise increase, our creativity and ability to innovate tend to taper off. Why? Because the walls of the proverbial box in which we think are thickening along with our experience.
Andrew S. Grove, the co-founder of Intel, put it well in 2005 when he told an interviewer from Fortune, “When everybody knows that something is so, it means that nobody knows nothin’.” In other words, it becomes nearly impossible to look beyond what you know and think outside the box you’ve built around yourself.
This so-called curse of knowledge, a phrase used in a 1989 paper in The Journal of Political Economy, means that once you’ve become an expert in a particular subject, it’s hard to imagine not knowing what you do. Your conversations with others in the field are peppered with catch phrases and jargon that are foreign to the uninitiated. When it’s time to accomplish a task — open a store, build a house, buy new cash registers, sell insurance — those in the know get it done the way it has always been done, stifling innovation as they barrel along the well-worn path.
———-
When experts have to slow down and go back to basics to bring an outsider up to speed, she says, “it forces them to look at their world differently and, as a result, they come up with new solutions to old problems.”
———————–
“I would ask my very, very basic questions,” she said, noting that it frustrated some of the people who didn’t know her. Once they got past that point, however, “it always turned out that we could come up with some terrific ideas,” she said.
—————–
“Look for people with renaissance-thinker tendencies, who’ve done work in a related area but not in your specific field,” she says. “Make it possible for someone who doesn’t report directly to that area to come in and say the emperor has no clothes.”