NASA satellite could reveal if primordial black holes are dark matter

Dec 09, 2011 by Lisa Zyga feature
An image taken by Kepler of star cluster NGC 6791, which is located 13,000 light years from Earth. The image has been color-coded so that brighter stars appear white, and fainter stars, red. Image credit: NASA/Ames/JPL-Caltech

(PhysOrg.com) -- The primary objective of NASA’s Kepler satellite, which was launched in March 2009 to orbit the Sun, is to search for Earth-like planets in a portion of the Milky Way galaxy. But now a team of physicists has proposed that Kepler could have a second appealing purpose: to either detect or rule out primordial black holes (PBHs) of a certain mass range as the primary constituent of dark matter.

The scientists, Kim Griest and Agnieszka Cieplak of the University of California, San Diego; Bhuvnesh Jain of the University of Pennsylvania; and Matthew Lehner of the University of Pennsylvania and Academia Sinica in Taipei, Taiwan, have published their study on using the Kepler satellite to detect PBH dark matter in a recent issue of Physical Review Letters.

“The nature of the dark matter is one of the biggest unsolved problems in all of science and so an answer would be extraordinary,” Griest told PhysOrg.com. “If it turns out to be primordial , that will be totally fascinating and everyone will want to understand what happened in the early universe to create them. If nothing is found, then we eliminate much of a major contender, but it is not as exciting.”

As the scientists explain, PBHs have been considered as a candidate for dark matter since the 1970s. These black holes are thought to have formed during the early universe from density perturbations that may have resulted from a variety of factors, such as inflation, phase transitions, and possibly even the collapse of string loops. Because there is no single theory for how PBHs formed, scientists don’t know how massive they would be. However, previous experimental and theoretical work has eliminated most PBH masses, including almost the entire mass range from 10-18 to 1016 , the exception being the mass range between 10-13 and 10-7 solar masses. Scientists call these 5 orders of magnitude the “PBH dark matter window.”

In the current study, Griest and his coauthors think that Kepler data could potentially rule out a significant portion of this window. Currently, Kepler’s photometer is measuring the light intensity of stars – about 150,000 different stars every 30 minutes. When analyzing the data, scientists look for specific fluctuations in star light, or stellar flux, since a decrease could signal an Earth-sized planet transiting in front of the star.

In their study, the physicists have shown that Kepler’s photometer could also be used to detect small amounts of gravitational lensing, or “microlensing,” which is the bending of star light as it travels through nearby space. According to general relativity, the bending is due to the gravity of an invisible mass that acts like a “lens” and lies between the light source (star) and observer (satellite). This lens could be a PBH or another type of massive compact halo object (MACHO) as well as mini halos, all of which are dark matter candidates.

“PBHs are really just one form of MACHOs,” Griest explained. “In the mass range we are sensitive to, I think PBHs are the most likely MACHO, but we won't really be able to tell if they were instead, say, non-topological soliton objects, which are another form of MACHO.”

According to the scientists’ calculations, Kepler could detect microlensing events caused by masses in the range between 5 x 10-10 and 10-4 solar masses, which means it could potentially rule out about 40% of the mass in the PBH dark matter window, if it doesn’t detect anything. If it does detect microlensing events, then of course the implications would be much more exciting: PBHs could be dark matter.

“One never really expects to solve such a major problem that has defeated explanation for more than 50 years,” Griest said. “So my skeptical scientist side says, most likely we'll rule out some parameter space. The searches for particle dark matter at LHC, etc., have so far come up empty handed, so I do think PBHs are becoming more likely as candidates.”

Although other microlensing surveys have examined tens of millions of stars over periods of many years, the scientists explain that Kepler can, somewhat surprisingly, provide stronger limits on in this particular mass range than these earlier surveys. Kepler’s advantages arise from the extreme precision of its photometer, which allows very small magnifications to be detected.

Griest and his coauthors have already begun looking at Kepler’s data, which is publicly available. Analyzing the data will not be that simple, since it requires an understanding of the complex light curve data, understanding false positives and background events (such as stellar flares), and using strict selection criteria.

Explore further: Neutrino trident production may offer powerful probe of new physics

More information: Kim Griest, et al. “Microlensing of Kepler Stars as a Method of Detecting Primordial Black Hole Dark Matter.” Physical Review Letters 107, 231101 (2011). DOI: 10.1103/PhysRevLett.107.231101

Journal reference: Physical Review Letters search and more info website

5 /5 (19 votes)

Related Stories

Could primordial black holes be dark matter?

Sep 21, 2011

(PhysOrg.com) -- “We know that about 25% of the matter in the universe is dark matter, but we don’t know what it is,” Michael Kesden tells PhysOrg.com. “There are a number of different theories about what da ...

Found: Heart of darkness

Aug 01, 2011

Astronomers using the 10-meter Keck II telescope in Hawaii have confirmed in a new paper that a troupe of about 1,000 small, dim stars just outside the Milky Way comprise the darkest known galaxy, as well ...

Recommended for you

And so they beat on, flagella against the cantilever

2 hours ago

A team of researchers at Boston University and Stanford University School of Medicine has developed a new model to study the motion patterns of bacteria in real time and to determine how these motions relate ...

Tandem microwave destroys hazmat, disinfects

5 hours ago

Dangerous materials can be destroyed, bacteria spores can be disinfected, and information can be collected that reveals the country of origin of radiological isotopes - all of this due to a commercial microwave ...

Cornell theorists continue the search for supersymmetry

7 hours ago

(Phys.org) —It was a breakthrough with profound implications for the world as we know it: the Higgs boson, the elementary particle that gives all other particles their mass, discovered at the Large Hadron ...

How did evolution optimize circadian clocks?

Sep 12, 2014

(Phys.org) —From cyanobacteria to humans, many terrestrial species have acquired circadian rhythms that adapt to sunlight in order to increase survival rates. Studies have shown that the circadian clocks ...

User comments : 46

Adjust slider to filter visible comments by rank

Display comments: newest first

Ironhorse
1.4 / 5 (9) Dec 09, 2011
If Steven Hawking is right, then any black hole in that mass range would long ago have evaporated, except for those far enough away that we see them as they were at the beginning of the universe. But at the same time if they do find them in our neighborhood, then Hawking's solution to the black hole 'entropy' problem will be ruled out which will leave other exciting possibilities to investigate, ie. what happens inside the black holes.
rawa1
1.4 / 5 (10) Dec 09, 2011
The only primordial black holes existing so far are the atom nuclei. No such thingies do exist in strict relativistic sense.

At the beginning of the last century the Austrian/Czech physicist Ernst Max proposed a hypothesis, that the inertia of massive bodies is a result of all massive objects in the Universe. This hypothesis has been rejected, because it implied a superluminal action at distance, but recently A. Carati demonstrated the same for dark matter, just with opposite sign. These two findings are giving sense in ancient de Duillier-LeSage theory, in which the gravity of massive bodies is given with shielding of superluminal particles or waves coming from all directions at the same time. And because the gravity is formed with shielding with massive objects, it means, it should be affected (actually shielded) with remote massive objects as well. And because shielding of gravity is actually antigravity, it would mean, the dark matter exhibits some the antigravity behaviour.
rawa1
1.4 / 5 (11) Dec 09, 2011
In general, the astronomers recognize so called cold and hot dark matter. Cold dark matter appears composed from many very tiny particles, whereas the hot dark matter appears to be composed of smaller amount of heavier ones. From the above mechanism follows, the Kepler spaceprobe couldn't find any cold dark matter, because its origin is widespread over whole observable Universe.

But the Big Bang theory is missing antimatter and most of antimatter can be hidden just in the clouds of dark matter, because of its alleged antigravity behaviour. Because some aspects of dark matter behaviour violate the shielding model apparently (existence of dark galaxies, dark matter rings or dragging effect at the Bullet cluster), it's probable, we still find so-called hot dark matter there. It will be probably present just in the form of antineutrinos, positrons and maybe some antiprotons. These particles are the only "primordial black holes", which do actually exist.
rawa1
1.4 / 5 (10) Dec 09, 2011
The amount of dark matter observed is sufficient to explain all missing antimatter and it probably contains additional normal matter too. It's somehow surprising, such a simple idea was never considered with mainstream physics - it doesn't violate anything what we know about physics. Instead of it, the physicists struggling with finding of many hypothetical exotic particles. For example, during time the following particles were proposed as the probable constituents of dark matter by mainstream peer-reviewed theories. I ordered them by their average rest mass, which differs in twenty(!) orders of magnitude: scalar field, quintessence, mirror matter, axions, inflatons, heavy photons, fat strings, sterile neutrinos, chameleon particles, dark fluid and dark baryons, fotinos, gravitinos and WIMPs, SIMPs, MACHOs, RAMBOs, DAEMONs and micro-black holes. And I probably missed many others...
typicalguy
5 / 5 (9) Dec 09, 2011
rawa1:
The missing antimatter is equal to all matter. All matter does not equal the amount of dark matter so there would have to be massive amounts of additional matter and antimatter. Of all matter (dark and normal), dark matter is over 80% so only roughly 1/5th is normal matter. So if all dark matter is normal matter and anti matter then there should be way more galaxies out there because there would be two and a half times as much normal matter and an equal amount of anti-matter.

I think it's safe to assume that even if normal matter and antimatter are constituents of dark matter, something we have yet to find (weather predicted or not) is also out there.
rawa1
1.3 / 5 (12) Dec 09, 2011
IMO the amounts of normal matter and antimatter in the observable Universe are balanced, but the antimatter is dispersed into dark matter and the dark matter contains additional amount of visible matter dispersed as well (in the form of neutrinos or even heavier particles, like the highly ionized atom nuclei without electrons - their positive charge keeps them from the safe distance from positrons). Which explains, why we can observe more dark matter than the observable matter.

It's just my guess, but we should check the hypothesis, which don't require any new additional particles first. Unfortunately, such down to Earth approach isn't popular in mainstream astrophysics at all, which explains, why nearly every scientist, who deals with dark matter already proposed his own kind of unknown particles for its explanation.
Parsec
5 / 5 (1) Dec 09, 2011
If PBH had been created in large numbers in the big bang, its unlikely they were created with a small range of masses. We should see PBH of essentially all masses be created, in which case, according to Hawking, we would see the smallest holes exploding at a slowly decreasing rate. The signature for these events are pretty easy to calculate, yet they haven't been seen. So they either are not there, or we just are not seeing them for some reason. I suspect they are not there.
eachus
1 / 5 (1) Dec 09, 2011
If Steven Hawking is right, then any black hole in that mass range would long ago have evaporated, except for those far enough away that we see them as they were at the beginning of the universe.


No, black holes with masses less than 10^11 kg would have evaporated by now, but that is about 0.5 x 10^19 solar masses. This is much smaller than the PBH window between 10^-13 and 10^-7 solar masses.

More interesting is to try and explain DM behavior, if DM is PBH. For example, supernova explosions would push PBH away from the center of galaxies as the black holes absorbed both photons and neutrinos. A black hole would have to be extremely close to a supernova to absorb any significant particle flux. The kick from the speed of light particles would accelerate the BH away from the supernova.

The problem of how much acceleration a 10^-13 solar mass black hole would get from a nearby supernova is left as an exercise for the reader. ;-)
eachus
3 / 5 (2) Dec 09, 2011
If PBH had been created in large numbers in the big bang, its unlikely they were created with a small range of masses. We should see PBH of essentially all masses be created, in which case, according to Hawking, we would see the smallest holes exploding at a slowly decreasing rate. The signature for these events are pretty easy to calculate, yet they haven't been seen. So they either are not there, or we just are not seeing them for some reason. I suspect they are not there.


Or they are responsible for some gamma ray bursts. The signal from an evaporating black hole would be complicated by the mass already in the area--and there will be some from the earlier evaporation. The final few seconds of a BH evaporating should create an extremely hot plasma, and we would see this, not the black hole evaporation directly.
typicalguy
4 / 5 (2) Dec 09, 2011
A variety of different PBH's would certainly help explain the super massive BH/galaxy chicken and egg problem. I think it's becoming more apparent the. BH's formed first. If you imagine the universe completely filled with matter/energy and a variety of BH's scattered around, they would suck in matter everywhere they went. Eventually the expansion of the universe combined with gravitational clumps created by PBH's lead to voids. The BH's then move towards each other from gravity. Eventually the accelerating expansion moves these BH's and their galaxies away from each other faster leading to chains of primordial BH's seemingly connected by a web. This web obviously just represents the the movement of galaxies when gravity was king. Now that DE has taken over, these chains of galaxies are accelerating away from each other in the same apparent webs they formed billions of years ago. Obviously some clumps are close enough together that they will come together still.
typicalguy
2 / 5 (1) Dec 09, 2011
TLDR version: imagine the big bang creates a bunch of black holes. Inflation pushes them apart. They suck up matter/energy which is everywhere in the universe. They move towards one another with the biggest BH's pulling others towards them like spiders in the middle of webs. Dark energy takes over Nd these webs of galaxies remain in place but are now moviing away and not towards the most massive BH's.
tadchem
5 / 5 (2) Dec 09, 2011
'to detect or rule out'
Excellent empiricism. Decisive measurements are difficult to design because they must be replicable by independent investigators. But it only takes one small fact to cast a huge and complex theory into doubt.
Ironhorse
2.7 / 5 (3) Dec 09, 2011
If Steven Hawking is right, then any black hole in that mass range would long ago have evaporated, except for those far enough away that we see them as they were at the beginning of the universe.


No, black holes with masses less than 10^11 kg would have evaporated by now, but that is about 0.5 x 10^19 solar masses. This is much smaller than the PBH window between 10^-13 and 10^-7 solar masses.


"...masses, including almost the entire mass range from 10-18 to 1016 solar masses, the exception being the mass range between 10-13 and 10-7 solar masses. Scientists call these 5 orders of magnitude the PBH dark matter window."

Note that the window is in masses less than a solar mass by several orders of magnitude. The smaller the black hole, the faster it evaporates according to Hawking.
Mahal_Kita
1.2 / 5 (10) Dec 09, 2011
The Schwarzschild radius is not the event horizon when particles faster than light exist. So real black holes conforming to the Mobius Theory must be in the order of trillions of solar masses in order to escape the Hawking radiation process. The oldest clusters in the Universe will contain such real black holes. This also explains why the Universe is expanding at accellerating speeds. 80% of the universes mass is at its far edges.
Benni
2.7 / 5 (7) Dec 09, 2011
80% of the universes mass is at its far edges.


How did you do that math? Could you submit a calculation? I'm real curious about this because you seem to be implying there is a definable symmetry to the entire Universe.
Shelgeyr
1 / 5 (5) Dec 09, 2011
NASA satellite could reveal if primordial black holes are dark matter


No, it can't/won't.

Unless of course the math is "add enough fudge factors together and you get a kludge", in which case OK.
sandler
1 / 5 (3) Dec 10, 2011
According to Big Bang theory there was an explosion which caused the stars to form and fly apart, stretching the vacuum between them and baloon like either which is beyond. These stars then fuse hydrogen they inherited and give out heat and light which eventially disapates since all of them have an expiration date at the end of which they turn to ash and inherit absolute zero temperature of the vacuum they live in. But what happens then? May be the universe expands because of the heat of stars and when it dies down it will collapse on to itself. This what black holes do too and possibly on outside the either is a blackhole which absorbs all heat and light of our expanding universe. It is getting ready to launch another big bang and form the blackhole but now with the sides inversed.
Callippo
4.2 / 5 (5) Dec 10, 2011
The attack of this spammer not only inserts silly (and apparently dysfunctional) ads to many threads, but it even ruins down the PO servers for a while. It's rather DoS attack, than the spam attack.
Nanobanano
1 / 5 (2) Dec 10, 2011
Eachus:

Good observation on the supernovas thing.

That would imply many PBH exist in intergalactic space traveling on hyperbolic trajectories away from their parent galaxy.

I have an alternate theory, which is simply that primordial black holes are what we THINK stellar black holes are.

Imagine, a primordial black hole is captured in a stable orbit in the photosphere of a Star. This happens due to a VERY close collision in when the PBH passes through the outer surface of the star and picks up material along the way. Due to frame dragging, over time the PBH falls into the star, and EATS the larger star's mass, becoming what we know as a "Stellar Mass Black Hole".
Callippo
1 / 5 (2) Dec 11, 2011
A much more probable scenario is, that the primordial black holes are composed of dark matter, than the vice-versa.
vidyunmaya
1 / 5 (4) Dec 11, 2011
Sub: In search of Prime Concepts
Where lies the Basic Concepts- Source,Fields, Flows, Reflectors and protective Index leave alone Prime functional
Cosmology Definition.
There must be a limit for psychology of Black-holes.
NASA should wake up in time -see its own sDO data
Plasma Regulated Electromagnetic Phenomena in magnetic Field Environment
Cosmology needs best of brains trust.
Search: Vidyardhicosmology [dot] blogspot [dot] com
Shootist
1 / 5 (2) Dec 11, 2011
A much more probable scenario is, that the primordial black holes are composed of dark matter, than the vice-versa.


Uh huh. You're want to create a hypothetical object out of hypothetical matter/mass?

A little lex parsimoniae.

WTF is dark matter? Matter that cannot be seen, that has gravitational effects upon its surroundings.
What is a black hole? Matter that cannot be seen, that has gravitational effects upon its surroundings.

Q.E.D.

Dayam.
Nanobanano
1 / 5 (2) Dec 11, 2011
WTF is dark matter? Matter that cannot be seen, that has gravitational effects upon its surroundings.
What is a black hole? Matter that cannot be seen, that has gravitational effects upon its surroundings.


So if 80% of galactic mass is supposedly Dark Matter, then where the hell are all the black holes, if Dark Matter is microscopic black holes?

If there was a "fog" or "halo" of microscopic black holes throughout the galaxy, as Dark Matter theory would then be claiming, wouldn't it be obvious when you look at other stars or galaxies?

There would need to be 4 stellar masses of PBH for every 1 stellar mass of ordinary matter, and they'd pretty much need to be EVERYWHERE within the galaxy, and they'd have to be spaced PERFECTLY so that they never collide with one another or odinary matter, else the galaxy would be consumed, and there'd be 400 billion stellar mas black holes floating around.

How come that doesn't happen if DM is PBH?

BS...
Seeker2
1 / 5 (2) Dec 11, 2011
"As the scientists explain, PBHs have been considered as a candidate for dark matter since the 1970s. These black holes are thought to have formed during the early universe from density perturbations that may have resulted from a variety of factors, such as inflation, phase transitions, and possibly even the collapse of string loops."

It seems to me density perturbations would be the source of all matter/antimater. Since most of matter is dark matter I expect dark matter came first. Since perturbations come in the form of lower density as well as higher density I should think there would be an equal amount of dark anti-matter out there but we don't see it because lower density areas are repulsed to the outer edges of spacetime like bubbles coming up from carbonated water.
Seeker2
2 / 5 (4) Dec 12, 2011
The only primordial black holes existing so far are the atom nuclei.

I'd think atomic nuclei would be stripped apart on entry to the BH. I doubt the nuclei itself has enough gravitation to form a BH.
Callippo
1 / 5 (3) Dec 12, 2011
You're want to create a hypothetical object out of hypothetical matter/mass?
Such objects aren't hypothetical, they're called dark galaxies and observed occasionally. In dense aether model (Aether Wave Theory, AWT) the universe is steady state and the galaxies are gigantic density fluctuations of hypothetical dense gas, forming the vacuum. These fluctuations slowly evaporate into radiation (photons and neutrinos) and condense somewhere else from the clouds of dark matter (usually in the free space between galaxies). The dark matter clouds are therefore the first stage of galaxy formation. The existence of these object was conjectured a long time before I introduced the AWT in various forms aka gravastars (Mazur, Motola) or dark energy stars (Laughlin). These guys suppose, they formed the first stage of hadronization of matter after Big Bang. In AWT the formation of matter occurs all around us, but the principle remains the same.
Seeker2
1 / 5 (2) Dec 12, 2011
lower density areas are repulsed to the outer edges of spacetime like bubbles coming up from carbonated water.

In this regard the U is sort of like a black hole. The denser elements sink and the lighter ones are pushed out. However if the black hole has spin it acts like a centrifuge and the denser areas get pushed to the outer edges. So I don't think the U has very much spin.

Callippo
1 / 5 (2) Dec 12, 2011
I doubt the nuclei itself has enough gravitation to form a BH.
The point is, the BH cannot exist in strictly general relativity sense, as the quantum mechanics prohibits the formation of singularities. But very dense artifacts which can still be formed are effectively equal to the atom nuclei. Inside of atom nuclei the particles are held together with their surface tension (represented with strong nuclear force) instead of gravity, but the appearance and behavior of these artifacts is very similar.
In this regard the U is sort of like a black hole
The FLRW metric used in L-CDM model is reversed Schwarzschild metric of black hole.
Callippo
1 / 5 (3) Dec 12, 2011
In dense aether model the event horizon of black holes is formed with the same dispersive mechanism, like the particle horizon of observable Universe. It doesn't mean, the Universe itself is black hole, because the infinitely large black holes are losing behavior of black holes: their event horizon is very fuzzy and their gravity field is very weak. It means, I don't expect the event horizon of Universe exists - it moves with observer, when he travels around it in similar way, like the the visibility scope inside of fog. If the Universe would be real black hole, there would be nonzero chance, we will find its outer surface soon or later. The observable Universe exhibits features, which can be interpreted like the jet of black holes (WMAP cold spot). But I presume, this location of this cold spot will travel together with us too. It's the feature of dispersive geometry, rather than real artifact at the Universe scale. It's localizable only for smaller structures inside it.
Benni
1.8 / 5 (5) Dec 12, 2011
In dense aether model the event horizon of black holes is formed with the same dispersive mechanism, like the particle horizon of observable Universe. It doesn't mean, the Universe itself is black hole, because the infinitely large black holes .


Whenever I see someone use the term "infinity" when talking about something, the red flags just stsrt going up all over the place. Nothing is infinite, & black holes are not "nothing", only thing I can think of that is infinite is "nothing" itself. Maybe I'm getting a little meta-physical here but that word word "infinite" can be a mighty big trap for unsuspecting people, especially when introduced within the context of quantum mechanics.
Seeker2
2 / 5 (4) Dec 12, 2011
It seems the infinite problem hits GR and the L-CDM model with the idea that the energy density of spacetime is constant as the U expands. Where does all that (dark) energy come from?
rawa1
1 / 5 (5) Dec 12, 2011
Where does all that (dark) energy come from?
The wavelength of ripples collapse with distance from observer. This is the analogy of red shift.
http://people.rit...4565.jpg
But as we can see, this collapse is non-linear and its speed accelerates with distance. This is dark energy.
Nothing is infinite
In AWT the universe is infinite, density of aether is infinite. Fortunately these things can be never seen in its entirety, because we are limited object. Limited object can observe / interact with only limited portion of its environment. Best of all, this interaction has even its own rules, from which the appearance of observable Universe can be deduced. For example, at the very boundary of our visibility scope everything can be observed via longitudinal waves only, from this the quantum mechanical behaviour of Universe at smallest and largest scales follows.
rawa1
1 / 5 (5) Dec 12, 2011
In dense aether model the red shift is reversed effect of dark matter in gravity field. The gravity field is condensing space-time and this attenuation of red shift appears like area of less or more dense matter around massive objects. Even better insight provides the old Duillier-LeSage model of gravity. In this model the gravity is shielding effect of tachyons (gravitational waves) by massive objects. After then the dark matter is the shielding effect of this shielding, i.e. the shielding of gravitational waves with all other massive objects in the Universe. But because this effect is limited at the boundaries of observable Universe (no other massive objects can apply outside of it), it leads to acceleration of red shift toward boundaries of observable Universe and its speed rises to the infinity at its boundaries (the inflation). It enables to understand gravity, dark matter and energy just with geometry of shielding of tachyons by observable objects inside of observable Universe.
Seeker2
1 / 5 (2) Dec 12, 2011
The wavelength of ripples collapse with distance from observer. This is the analogy of red shift.
http://people.rit...4565.jpg
But as we can see, this collapse is non-linear and its speed accelerates with distance. This is dark energy.

We're not talking about variation in space relative to an observer, but variation in time of the energy density of all space. This is directly shown by the redshift - the energy density of space decreasing with time as the U expands.
Note the passing of time as we perceive it is actually expansion of spacetime in the time dimension. If the ratio of spatial expansion to the passage of time (time expansion) remains the same, as we should think from SR, the speed of light remains constant. It seems redshift is direct evidence that the energy density decreases with time.
Seeker2
1 / 5 (3) Dec 12, 2011
Note if GR is true and the energy density of spacetime remains constant there would be no redshift.
rawa1
1 / 5 (3) Dec 12, 2011
We're not talking about variation in space relative to an observer, but variation in time of the energy density of all space.
But is the dark energy really related to the energy density of all space? IMO it's just your interpretation of it - what we are observing is just the energy density of incoming light. After all, Occam's razor leads us to into consideration of less demanding explanation first - why to consider the change the density of space-time, if just subtle change of tiny amount of energy density of incoming light would be enough? Such interpretation of dark energy apparently violates the Copernician principle too - why the property of the whole Universe should change so drastically with respect to just us, negligible silly human observers? It would introduce the geocentric model of Universe again. Isn't it a much easier to consider the dispersive mechanism? Inside of fog the observer is always at the centre of the observable reality automatically.
rawa1
1 / 5 (3) Dec 12, 2011
Inside of fog the observer always sees the neighbouring area clearly, which would indicate, the density of fog is lowest just at the place of observer. But as we know, it's just an illusion given by integrative effect of fog absorbance. The density of fog can be equal at all places and yet the above dispersion effect can manifest clearly.
Note if GR is true and the energy density of spacetime remains constant there would be no redshift.
GR derives the gravitational red shift just with consideration of variable energy density due the variable gravity field.
Seeker2
1 / 5 (2) Dec 12, 2011
But is the dark energy really related to the energy density of all space? IMO it's just your interpretation of it - what we are observing is just the energy density of incoming light.
Certainly the energy density of incoming light is diminished by spatial expansion. Accelerating expansion requires force. Force exerted over a distance performs work. Work requires energy. My interpretation is this energy comes from the dark energy. If anyone has a better idea tell us. This expansion causes the redshift, not gravitational fields.
Shootist
1 / 5 (3) Dec 12, 2011
WTF is dark matter? Matter that cannot be seen, that has gravitational effects upon its surroundings.
What is a black hole? Matter that cannot be seen, that has gravitational effects upon its surroundings.


So if 80% of galactic mass is supposedly Dark Matter, then where the hell are all the black holes, if Dark Matter is microscopic black holes?


What if they are unassociated and macro-scopic? Not quantum, at all, just free floating stellar mass singularities awash in the Universe?

That article asking if DM matters posits enormous mass residing outside of galaxies . . .
Shootist
1.3 / 5 (3) Dec 12, 2011
I'd ask what was the fate of the Quasars from the early Universe. Articles suggest they possessed masses in excess of anything closer in. Did their galaxies finally cease star formation, age, and become too dim to see? Certainly that mass still factors in somewhere along the line.

Yet, I see a problem, I think. Too many of these former Quasars and the effects of their gravity would be apparent on more than Galactic rotation rates.

What is the size/mass cutoff before gravitational lensing becomes readily apparent?

Benni
1 / 5 (1) Dec 12, 2011
Nothing is infinite
In AWT the universe is infinite, density of aether is infinite. Fortunately these things can be never seen in its entirety, because we are limited object. Limited object can observe / interact with only limited portion of its environment. Best of all, this interaction has even its own rules, from which the appearance of observable Universe can be deduced. For example, at the very boundary of our visibility scope everything can be observed via longitudinal waves only, from this the quantum mechanical behaviour of Universe at smallest and largest scales follows.


And you phycisists wonder why the engineering profession thinks you guys are "a bit whimsical". I don't understand one iota of what you just said above, but damn if it doesn't sound good. Next time I talk to my boss about getting a raise, I'm gonna talk like this, and trust he'll be so snowed with the magic of my words that he'll just get out of his chair & turn it over to me.
tadchem
not rated yet Dec 14, 2011
Hawking Radiation would have evaporated all of the smallest black holes. Larger ones in a 'swarm' would have inelastic interactions with each other, quickly consolidating into even larger black holes. GR mandates radiative emissions from accelerated charges, and black holes *do* have charges.
These interactions would emit EM radiation, negating any 'blackness'.
Blakut
1 / 5 (1) Dec 19, 2011
Primordial African-American Hole, please.
Seeker2
1 / 5 (2) Dec 22, 2011
What if they are unassociated and macro-scopic? Not quantum, at all, just free floating stellar mass singularities awash in the Universe?
I think free floating stellar mass singularities would be black holes.
Shelgeyr
1 / 5 (2) Dec 28, 2011
Part 1:
My earlier comment where I quoted the headline and then said:

No, it can't/won't.(snip)


...was greeted with such acclaim that I just have to elaborate. "Dark Matter" is merely hypothetical - not even theoretical. "Black Holes", while far more accepted (which is not in itself evidence of existence), are only barely on firmer theoretical ground.

Thus the following statement SEEMS to be comparing an unknown to a known, but in fact is just comparing two unknowns:

The nature of the dark matter is one of the biggest unsolved problems in all of science and so an answer would be extraordinary, Griest told PhysOrg.com. If it turns out to be primordial black holes...

(continued...)
Shelgeyr
1 / 5 (3) Dec 28, 2011
Part 2:
We have only calculations and models, both of which we know to be incomplete, to "tell" us anything (if you'll forgive the phrase) about black holes (PBHs or otherwise), but no actual evidence. Ditto for dark matter. Thus the phrase "However, previous experimental and theoretical work has eliminated most PBH masses..." is patently false. They have done no such thing, except possibly in terms comparable to "we've ruled out the following directions to Fantasyland".

We don't know the nature of dark matter or black holes, if they exist. So even granting their existence, in light of this lack of knowledge it isn't so much like shooting without knowing where the target it, but more like shooting without knowing WHAT a target is.

We might as well say we're sending up satellites to try to read God's facial expressions.