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A five-year survey of 200,000 galaxies, stretching back seven billion years in cosmic time, has led to one of the best independent confirmations that dark energy is driving our universe apart at accelerating speeds. The survey used data from NASA’s space-based Galaxy Evolution Explorer and the Anglo-Australian Telescope on Siding Spring Mountain in Australia.
The findings offer new support for the favored theory of how dark energy works — as a constant force, uniformly affecting the universe and propelling its runaway expansion. They contradict an alternate theory, where gravity, not dark energy, is the force pushing space apart. According to this alternate theory, with which the new survey results are not consistent, Albert Einstein’s concept of gravity is wrong, and gravity becomes repulsive instead of attractive when acting at great distances.
“The action of dark energy is as if you threw a ball up in the air, and it kept speeding upward into the sky faster and faster,” said Chris Blake of the Swinburne University of Technology in Melbourne, Australia. Blake is lead author of two papers describing the results that appeared in recent issues of the Monthly Notices of the Royal Astronomical Society. “The results tell us that dark energy is a cosmological constant, as Einstein proposed. If gravity were the culprit, then we wouldn’t be seeing these constant effects of dark energy throughout time.”
Dark energy is thought to dominate our universe, making up about 74 percent of it. Dark matter, a slightly less mysterious substance, accounts for 22 percent. So-called normal matter, anything with atoms, or the stuff that makes up living creatures, planets and stars, is only approximately four percent of the cosmos.
The idea of dark energy was proposed during the previous decade, based on studies of distant exploding stars called supernovae. Supernovae emit constant, measurable light, making them so-called “standard candles,” which allows calculation of their distance from Earth. Observations revealed dark energy was flinging the objects out at accelerating speeds.
Dark energy is in a tug-of-war contest with gravity. In the early universe, gravity took the lead, dominating dark energy. At about 8 billion years after the Big Bang, as space expanded and matter became diluted, gravitational attractions weakened and dark energy gained the upper hand. Billions of years from now, dark energy will be even more dominant. Astronomers predict our universe will be a cosmic wasteland, with galaxies spread apart so far that any intelligent beings living inside them wouldn’t be able to see other galaxies.
The new survey provides two separate methods for independently checking the supernovae results. This is the first time astronomers performed these checks across the whole cosmic timespan dominated by dark energy. The team began by assembling the largest three-dimensional map of galaxies in the distant universe, spotted by the Galaxy Evolution Explorer. The ultraviolet-sensing telescope has scanned about three-quarters of the sky, observing hundreds of millions of galaxies.
“The Galaxy Evolution Explorer helped identify bright, young galaxies, which are ideal for this type of study,” said Christopher Martin, principal investigator for the mission at the California Institute of Technology in Pasadena. “It provided the scaffolding for this enormous 3-D map.”
The astronomers acquired detailed information about the light for each galaxy using the Anglo-Australian Telescope and studied the pattern of distance between them. Sound waves from the very early universe left imprints in the patterns of galaxies, causing pairs of galaxies to be separated by approximately 500 million light-years.
This “standard ruler” was used to determine the distance from the galaxy pairs to Earth — the closer a galaxy pair is to us, the farther apart the galaxies will appear from each other on the sky. As with the supernovae studies, this distance data were combined with information about the speeds at which the pairs are moving away from us, revealing, yet again, the fabric of space is stretching apart faster and faster.
The team also used the galaxy map to study how clusters of galaxies grow over time like cities, eventually containing many thousands of galaxies. The clusters attract new galaxies through gravity, but dark energy tugs the clusters apart. It slows down the process, allowing scientists to measure dark energy’s repulsive force.
“Observations by astronomers over the last 15 years have produced one of the most startling discoveries in physical science; the expansion of the universe, triggered by the Big Bang, is speeding up,” said Jon Morse, astrophysics division director at NASA Headquarters in Washington. “Using entirely independent methods, data from the Galaxy Evolution Explorer have helped increase our confidence in the existence of dark energy.”
For more information see the Australian Astronomical Observatory
The article could have been better titled. GALEX only managed to refute one idea of what DE could be. So “GALEX Confirms What Most Probably is not the Nature of Dark Energy”. Catchy! Don’t you think? 😀
Science is not about proving theories, but supporting them by verifying their predictions. So the de Sitter spacetime in the Einsteinian framework has been supported and its challenger falsified.
LC
So it’s another kick in the ‘family jewels’ department of the “Electric Universe” proponents, then?
yes ivan3man. this entire study was conducted in order to refute EU proponents.
in fact, i just heard that every article posted on UT from now on will be dedicated to the cause
yes ivan3man. this entire study was conducted in order to refute EU proponents.
in fact, i just heard that every article posted on UT from now on will be dedicated to the cause
Just a question from a curious less-than-amateur star interested reader of this blog. This would mean that galaxies would become too distant to see each other long before their last stars burn out, wouldn’t it? And please, no advanced phyics – though i find it interesting i know next to nothing about this stuff 🙂
yes in a distant futere the expansion will go so fast that light from does galaxies can not reach us anymore
I think it’s better to say that we expect their light will be redshifted into invisibility due to the expansion of space-time between receding galaxies.
But won’t their high-frequency emissions be red-shifted into the visible spectrum?
Right. I believe the missing piece is a decreased photon arrival rate, see my comment above.
Though even without it, eventually you run up against Planck energy limits of emitting (or rather all) processes, so redshift is in principle enough AFAIK.
If the relative velocity, after accounting for the expansion of intervening space, is greater than the speed of light, then it is probably better to simply say the light cannot reach us.
Stating it in terms of redshift implies that the photon particles at some point become redshifted through zero energy and start moving backwards. This is equally as wrong as saying the distant object is traveling faster than light.
The light only exists as far as it can propagate. If it cannot reach us, we measure no redshift value because it’s simply not here. It’s stuck somewhere in between, fighting a losing battle.
If you watched a particular galaxy over trillions of years, it would gain redshift until suddenly blinking out of existence as the distance became impassible to light.
Why would that be implied?
Cosmological redshift z (with a defined as in lcrowell comment) obeys 1 + z = anow/athen so as anow goes to infinity z does too.
Since z = (femit – fobs)/fobs we have 1 + z = (fobs + femit – fobs)/fobs = femit/fobs; as 1 + z goes to infinity fobs goes to 0. Then photon energy E = h*fobs goes to 0.
What happens then is the analogous horizon effect as for a black hole. Complementary to what lcrowell wrote, photons will be diluted with the expansion. That is, at the same time as their energy goes down their numbers will gradually decrease into invisibility. No blinking.
No photons will be harmed in this process. =D Specifically they will not be “stuck” but propagate as they always do, at the speed of light.
The take home message here is IMO that physics really dislike discontinuities (no velocity reversal, irradiation blinking, or sticking in spacetime). If these are suggested by your hypotheses, there is either something wrong with them or we need some new physics for a better description.
You are correct that the ratio of the scale factors at different times a(t)/a(t_0) = z + 1 The a(t) is computed from
(a’/a )^2 = 8??/3
for a’ = da/dt and ? the cosmological constant. So this is a first order differential equation of the simplest type, fir
a’ = sqrt{8??/3}a
which has an easily found exponential solution
a(t) = a(t_0) exp(t sqrt{8??/3}).
As we often do things we consider a Taylor expansion of the a(t) for comparatively small times
a(t) /a(t_0) = 1 + sqrt{8??/3}t *****
We then convert the time to a distance ( a radial distance r), which is permissible in this linear approximation t = r/c and we have that
a(r) /a(t_0) = 1 + sqrt{8??/3c^2}r
the first (a’/a )^2 = 8??/3 is also H^2 = (a’/a )^2 and so
sqrt{8??/3c^2}r = Hr.
This is Hubble’s law that he deduced by observational data. Now for hr = v and for v = c it is clear that the radius is r = sqrt{3c^2/8? ?}. Now stick this into equation ***** for t = r/c and you get a(t) /a(t_0) = 2 or z = 1.
So when every you see these UT reports about galaxies with z > 1 and now some are beyond z = 8 those galaxies are on a co-moving frame with a velocity about v = zc — faster than light. The exponential nature of the a(t) solution means that for significant z there are departures from this. The CMB has a z = 1000, but is 45 billion ly out. The expansion of space also means spatial distances at large extend beyond the expected distance based on time.
LC
Thanks for the description!
Ah, right, thanks for the correction.
So we will still see the other galaxies, but the image we see is slowed to a freeze-frame, asymptotically approaching a point in time. (And getting ever dimmer and redder.)
In that case, I don’t like the phrase “into invisibility”…
My suggestion wasn’t that they get stuck, but that the expansion of space outpaces their ability to propagate. This is what happens, but there is no “blinking out.” If you accept the notion of extreme redshift as invisibility, then my description actually is accurate.
Agreed.
There’s also a more directly relevant factor to consider, plasma frequency. Once the frequency of light drops below that of the plasma frequency of the medium (a plasma) through which it’s travelling, it will be absorbed.
So, sometime soon (cosmologically speaking), we won’t be able to see the CMB from down here on the surface of the Earth, because it won’t get through the ionosphere (assuming the Earth still has an ionosphere then). Later, even replicas of COBE, WMAP, and Planck wouldn’t be able to detect the CMB – it’d be redshifted beyond the plasma frequency of the interplanetary medium (in the vicinity of the Earth).
Later still, you’d have to go someplace outside the galaxy to detect it, as the interstellar medium becomes opaque to CMB frequencies.
Beyond that, I’m not sure; would the inter-galactic medium’s plasma frequency drop (multiple processes) faster than the rate at which the CMB is redshifted?
Yeah, that occurred to me too.
In the case of the CMB, it would be absorbed and re-radiated, so anisotropy would be lost, but it could still be observed by slightly raising the temperature of everything, or slowing the cooling process, right?
The other factor is what process produces the highest energies that might be observed from an otherwise-dark neighboring galaxy. Since we don’t need to differentiate photons from other particles, and the Oh-My-God Particle doesn’t even represent an upper limit (although we don’t know if it came from our galaxy or not, there must be some chance of things being transmitted over cosmological scales), it should be a very long time before the sky is completely dark :v) .
The CMB radiation will be red shifted from the microwave into the radio frequency band and then the very long wavelength band. Further this will happen in 10 to 20 billion years. Similarly galaxies will be red shifted out of the optical band into the infrared band and then into the millimeter wave band. So any ETI that evolves on some planet around that time, and there will still be plenty of stars then, will not immediately observe other galaxies outside of their local cluster. However, if they observe out in IR or radio they will detect them. They may also find the CMB in the long wavelength band.
There is no real problem of not observing the CMB due to the ionosphere. We can point radio telescopes to the sky and see astronomic objects in that band. In 10 billion years any ETI will have to find the CMB by similar means.
Things will disappear once the radiation these objects emit is red shifted beyond the aperture of any conceivable instrument, or much larger than any possible quarter wave stack. This becomes fundamental once such radiation is stretched beyond the diameter of the Hubble region bounded by the horizon length d_h = sqrt{3/?} ~ 10^{10} light years. These conditions will be met in around 10^{30} years, so the CMB and any other galaxies will truly be invisible. However, there will no longer be any stars either, the last stars will wink out in around 10^{12} years, so I doubt any conscious observer will exist then. By 10^{40} proton decay will have largely erased protons and matter from the universe and all there will be are black holes. 10^{100} years beyond then Hawking radiation will have erased the black holes and the universe will be a de Sitter vacuum. Then that will quantum decay over far more enormous time periods into the future so it asymptotes to an empty flat spacetime.
So the future of the universe is sort of captured by a Pink Floyd song, or maybe Jim Morrison of the Doors, “This is the end, my only friend the end … .” Things are going to get very dark and cold.
LC
What if there’s a future without proton decay?
A universe without proton decay is problematic. What might be the case with that decay channels are predicted in E_6xSU(3) symmetry with larger masses for the mixing gauge vectors. This pushes proton decay to about 10^{35} years or more. In this system there are is a 78-representation which intertwines leptons and quarks.
The expectation of physics is that things which look absolutely separate now, turn out to be special cases of entities that transform amongst each other in generality. This should be expected of the general family structure of quarks and leptons.
The extraordinary time scales in the wiki article are of course without proton decay, os an iron sphere will quantum tunnel into a black hole.
It turns out that neutron stars are extraordinarily long lasting as well.
LC
O.K., and thanks!
There isn’t any proton decay under the Standard Model. (Which isn’t complete, mind.) So, why couldn’t it be that way?
But I hear that it is easier to explain neutrino oscillations together with some observed symmetry breaking (chiral anomalies) if it doesn’t happen. OTOH in current experiments nature doesn’t go for the simplest (say, supersymmetry is on its way out).
“There is no real problem of not observing the CMB due to the ionosphere. We can point radio telescopes to the sky and see astronomic objects in that band.” – not true; here is a good webpage which explains why the sky is opaque to radio wavelengths less than a few MHz: http://ecjones.org/physics.html
Incidentally, this is why Grote Reber moved to Tasmania, Australia; the radio sky there is least opaque to low frequency astronomical signals: http://www.groterebermuseum.com.au/index.html
It may be that the electron density in the ionosphere (and/or solar wind) will fall faster than the CMB redshifts – it is dependent on quite a few physical processes – so the CMB may stay visible for a long while.
“but it could still be observed by slightly raising the temperature of everything, or slowing the cooling process, right?” – I don’t think so; the temperature of the ISM (to take just one example) varies far too much, caused by far too many effects, for any such slight heating to be detectable. It may, however, be possible to infer the existence of something like a CMB, in a manner similar to how it was first almost (but not quite) discovered: by McKellar, using interstellar molecules, in 1940:
http://www.astro.ucla.edu/~wright/CMB.html
(replying to myself, to address two comments in one)
“There is no real problem of not observing the CMB due to the ionosphere. We can point radio telescopes to the sky and see astronomic objects in that band.” – not true; here is a good webpage which explains why the sky is opaque to radio wavelengths less than a few MHz: http://ecjones.org/physics.html
Incidentally, this is why Grote Reber moved to Tasmania, Australia; the radio sky there is least opaque to low frequency astronomical signals: http://www.groterebermuseum.com.au/index.html
It may be that the electron density in the ionosphere (and/or solar wind) will fall faster than the CMB redshifts – it is dependent on quite a few physical processes – so the CMB may stay visible for a long while.
“but it could still be observed by slightly raising the temperature of everything, or slowing the cooling process, right?” – I don’t think so; the temperature of the ISM (to take just one example) varies far too much, caused by far too many effects, for any such slight heating to be detectable. It may, however, be possible to infer the existence of something like a CMB, in a manner similar to how it was first almost (but not quite) discovered: by McKellar, using interstellar molecules, in 1940:
http://www.astro.ucla.edu/~wright/CMB.html
(replying to myself, to address two comments in one)
yes in a distant futere the expansion will go so fast that light from does galaxies can not reach us anymore. So we will not see any of does galaxies anymore.
I’m pretty much like you, pretty amateur. But my understanding is that the universe was already expanding due to the big bang, and now dark energy is taking over the repulsion, making everything expand even faster than before. So in the future, the expansion will be even faster. It really depends on the speed of the repulsion already, and I don’t know that, so I’m left as clueless as anyone not a scientist, I suppose. Hope this helps, even a little.
I have been hearing a lot about this on the news. I have found it annoying and misleading, as it is being reported as if scientists have only just discovered that this is occurring. This was discovered back in around 1998 by Hubble was it not?
Am I right in saying that this is just a more widespread confirmation of this fact? Or is this actually the first proof that this is occurring?
I think you are right in saying that this is more confirmation. Science doesn’t really deal with proof. Theories are either sustained by evidence – or they are not.
However, IMHO this is more confirmation that the universe is expanding at a uniformly accelerating rate. It does not confirm anything much about the nature of what drives this phenomenon. There is no particular reason to conclude that the accelerating expansion is driven by a mysterious form of ‘energy’.
These days, science spends a long time verifying something before it feels comfortable publishing it as scientific fact. A theory or idea can drop into the news cycle from time to time, especially when it gets a major validation. This would be one of those occasions.
But yes, a lot of “laymen” news organisations tend to report a scientific discovery as having happened in the same week the paper was published – they often don’t understand that it comes after years of poring over data and even more years after the idea or theory was first proposed.
Some galaxies may already be beyond this threshold for us (which I believe is called our cosmic horizon). However I’m not certain about that.
In any case, since Andromeda is actually moving to collide with us, that galaxy at least will always be visible in our sky.
That is until it’s all supplanted by the Andromeda Way galaxy.
That is until it’s all supplanted by the Andromeda Way galaxy.
The CMB is beyond the horizon, but we can see it. I laid more of this out the other day on this blog entry. The cosmological event horizon is a boundary beyond which we are not able to communicate a signal to. Yet we can receive signals from things from beyond that region. It is a bit like observing the outside world from within a black hole.
Galaxies will just simply appear more red shifted with time. In 10 billion years galaxies outside our local group will only be observable in the infrared or longer wavelengths. They will still be technically observable. In several 10s of billions of years beyond then they will only be observable in the microwave region. The CMB will similarly red shift from the microwave to the radio wave and then to long wavelength radio waves.
LC
The CMB is beyond the horizon, but we can see it. I laid more of this out the other day on this blog entry. The cosmological event horizon is a boundary beyond which we are not able to communicate a signal to. Yet we can receive signals from things from beyond that region. It is a bit like observing the outside world from within a black hole.
Galaxies will just simply appear more red shifted with time. In 10 billion years galaxies outside our local group will only be observable in the infrared or longer wavelengths. They will still be technically observable. In several 10s of billions of years beyond then they will only be observable in the microwave region. The CMB will similarly red shift from the microwave to the radio wave and then to long wavelength radio waves.
LC
Science is about measurement and this result improves the best current accuracy by a significant degree. The result confirms the existence of dark energy by a new method and we may learn more about the nature of dark energy from slight differences between this method and others. I think the headline however has more to do with what it says about the nature of dark energy. Two competing models are a “cosmological constant” which was included by Einstein in GR and “quintessence” which varies over time. The significance of the Galex result seems to be that it shows little time variation hence is suggestive that “quintessence” is not a good model. Science works by falsifying alternatives by showing they are inconsistent with measurements until there is only one model left that fits all the observations.
😀 You mixed up two things here (at least in my interpretation, as I realise, now). Edwin Hubble found in 1928 (+/- a few years) that galaxies were mostly receding from us, that is to say that the universe expands. In 1998 two different groups found simultaneously that the universe’s expansion accelerates. (This might have involved the Hubble Space Telescope, which would make your statement correct, again. 😉 )
What this research did is to compare what we call radar distance with ruler distance. The radar distance is a distance determined by the path of light beams in spacetime. It is called a radar distance because radio or microwave beams were used to first measure it. The other distance is a ruler distance. What is the difference between them? We start with the distance in spacetime, sometimes called the interval or metric interval. We ignore two of those dimensions and consider a spacetime distance with time and radial coordinate. This spacetime distance is the proper time of a clock on a path in spacetime. This is
ds^2 = dt^2 – a(t)dr^2.
The factor a(t) is a scale factor expansion which determines how much space is stretched out with time, which can for certain model involve a contraction as well. The negative sign difference between the time and radial parts reflects the pseudo-Euclidean structure of spacetime. If ds^2 = 0, which is the distance along which a photon travels, then the radial dstance measure obtains is dr = dt/sqrt{a(t)} Now if we know what a(t) is then we can integrate both sides of that and measure the distance. This is the radar distance. The ruler distance is the distance obtained for a constant time on our watch. So we set t = constant, or dt = 0 and we then measure dr = ds/sqrt{a(t)}, taking absolute value to avoid sqrt{-1}, and low and behold this is the same as the radar distance for this type of metric.
The redshift of galaxies is a measure of the radar distance. The ruler distance is measured by this comparison between nearby galaxies. This latter part is clearly the most difficult, for it clearly involves pain staking link ups of individual galaxy data. The metric above preducts that the two measures should be equal. The data confirms this prediction.
So what is this scale factor a(t)? Given a radial distance r the scale factor a(t) gives a new radial distance r’(t) = a(t)r. I will use Hewtonian mechanics and gravity, for it turns out that this gives the same thing as general relativity for flat space, but curved spacetime. General relativity is somewhat complicated to work with. We have for Newtonian mechanics with gravity that the kinetic energy of a moving object is (1/2)mv^2 and that the potential energy is -GMm/r. The total energy is the sum of these. The velocity is determined for our situation by the scale factor so that r(t) = a(t)r and v(t) = (da/dt)r. A little bit of calculus is entering in here. So the total energy we can set to zero, and we have
(a’)^2 = 2GM/a, a’ = da/dt
We then have M = (4?/3)d (ar)^3, for d = density of matter in a spherical region of radius r’ = a(t)r. We then write this dynamical equation as
a’^2 = 8? Gd a^2/3,
where the Hubble factor is H = a’/a. Now if I assume that the density is constant then this is a differential equation a’ = Ka, for H = sqrt{8?Gd/3}, and the solution is
a(t) = (1/H}exp(Ht).
So the scale factor expands exponentially. This is approximately a de Sitter spacetime configuration.
The Hubble factor for small time gives v = Hr, for r a small radius out related to a time t. For v = c one can compute the radius where that occurs and we have r = c/H which is the cosmological horizon distance
R = 1/sqrt{8?Gd/3c^2} = sqrt{3//}
Where / is the cosmological constant. This horizon distance is about 10 billion light years.
This event horizon is not a barrier to our ability to observe things. It is similar to the event horizon of a black hole, but it is analogous to looking out into the exterior world from inside a black hole. It is a barrier to our ability to send a signal to anything beyond this distance. A galaxy with a z > 1 is beyond this event horizon, and the CMB has z ~ 1000. What happens with galaxies disappearing is that they will accelerate away and become highly red shifted. In about 10 billion years all galaxies outside our local group will be red shifted out of the optical band. An intelligent life form could observe other galaxies if they use IR or microwave instruments. The CMB will recede into the radio wave band and to long wavelength frequencies.
LC
That seems to be correct AFAIK, the universe without dark energy would essentially be in a free-wheeling expansion after initial inflation, braking due to gravity of mass content to different degree. Instead we have a “runaway expansion”.
The researcher who first reported this was Perlmutter. The data was collected by ground based telescopes. The Hubble telescope got into the action after this report. Perlmutter found that supernova Ia had a relative luminosity that scaled downwards at a rate faster than expected. SNIa are due to the accretion of matter onto a white dwarf which then exceeds the Chandreshankar limit and causes it to implode like a hydrogen bomb core. The result is a sort of cosmic hydrogen bomb that can be seen across billions of light years. They all have about the same absolute luminosity, and so they serve as a standard candle. This was the first clue that the universe was accelerating outwards.
LC
The supposed acceleration of the supposed expansion is not taking place now – it is based upon observations of stars at very large distances and thus in the very far past – because of the long time for the observations to reach us now. If it occurred it was in the far past.
The distant observations imply that expansion was at a lower rate 6 to 8 billion years ago than it is now hence it appears to be accelerating.
The distant observations imply that expansion was at a lower rate 6 to 8 billion years ago than it is now hence it appears to be accelerating.
One of the scientists involved in this, Michael Drinkwater, is my physics lecturer. He was really excited to announce this in the lecture today. and its only fueling my own interest in astrophysics research.
“Dark energy is thought to dominate our universe, making up about 74 percent of it. Dark matter, a slightly less mysterious substance, accounts for 22 percent. So-called normal matter, anything with atoms, or the stuff that makes up living creatures, planets and stars, is only approximately four percent of the cosmos.
The idea of dark energy was proposed during the previous decade, based on studies of distant exploding stars called supernovae. Supernovae emit constant, measurable light, making them so-called “standard candles,” which allows calculation of their distance from Earth. Observations revealed dark energy was flinging the objects out at accelerating speeds.”
The above two paragraphs are quotes from the article above. I believe they could have researched and addressed other alternative theory possibilities concerning the observed data rather than just one single alternative hypothesis:
This was not a small study. According to the article above it was a five-year survey of 200,000 galaxies, certainly a vast undertaking with great effort. Their conclusions concerning a single alternative hypothesis may be correct but as others comments here have rightfully mentioned, their conclusion does not address alternative hypotheses as a whole.
“Dark energy is thought to dominate our universe,” their statement above is certainly a valid statement concerning the beliefs of most theorists in present day cosmology. Probably few in this study and the mainstream in general however have thought to seek out, investigate, and consider the countless other possibilities, some of which are simpler theory/ hypotheses/ alternatives such as the Hubble formula could be somewhat inaccurate (roughly as much as 10%), leading to the dark energy hypothesis in the first place. If so dark energy accordingly would not be needed and their conclusions inaccurate.
Another example I believe is that General Relativity may also need to be altered concerning galactic distances as well as the whole warped space concept of gravity. In both cases dark energy and dark matter might be replaced by more accurate and functional formulations that could do away with not only dark energy and dark matter, but the presently unknown models that might replace them might also replace the complicated expanding universe concept and the Big Bang model as a whole which has evolved into a model which I think is far from simple and straight forward.
To discover different and sometimes simpler possible explanations, I think more alternative theory needs to be evaluated, many of which can only be found in alternative rather than mainstream journals and publications. To limit ones considerations to only what is bantered in mainstream circles and is well-known, in time will be realized as a mistake.
Oh no, not you again!
So, according to your philosophy, we should do away with the “complicated” General Relativity-based GPS system and navigate around the world with a more “simple and straight forward” lodestone suspended from a piece of string(!).
Quote from link below:
“The Operational Control System (OCS) of the Global Positioning System (GPS) does not include the rigorous transformations between coordinate systems that Einstein’s general theory of relativity would seem to require – transformations to and from the individual space vehicles (SVs), the Monitor Stations (MSs), and the users on the surface of the rotating earth, and the geocentric Earth Centered Inertial System (ECI) in which the SV orbits are calculated. There is a very good reason for the omission: the effects of relativity, where they are different from the effects predicted by classical mechanics and electromagnetic theory, are too small to matter – less than one centimeter, for users on or near the earth.”
http://www.conservapedia.com/Theory_of_relativity
Although it has been claimed that the considerations of General and Special relativity have been programmed into the GPS system, it is also true that there are self correcting algorithms within the system that have been a fundamental part of the system since it went up and all contradictory calculations/ information concerning incoming data coming from one or more satellite or ground unit, become self-corrected by these automatically refined algorithms by their continuous application and feedback from the designed multiple check systems.
The built-in correction is around 35us per day. The clock corrections applied are of the order of 4ns per day so the argument on the web site is nonsense by four orders of magnitude.
Thanks, your comment is noted.
You linked to Conservapedia(!) as the source of your information?!
ROTFLMAO!
ROTFLMAO indeed! Referring to Conservapedia as proof of the veracity of crap is like the standard practice (eek!) of referring to the christian bibles as proof of the veracity of the christian bibles.
The discussion ends there, FF is just parroting without understanding, well, anything of the world.
See my comment to that reference below. Although I think the wording of what I quoted is totally correct, as I said below — I now realize that there is a political agenda to the site and will not site it as a reference again. This was the first and last time.
“Remarkable bird, the Norwegian Blue, idn’it, ay? Beautiful plumage!”
You linked to Conservapedia(!) as the source of your information?!
ROTFLMAO!
It is a bit like “Chucky’s back,” if you remember those silly Chucky doll movies. The Conservapedia article Forrest links lists black holes, dark matter moral relativism and wormholes as “liberal pseudo-science.” Gotta love that stuff! It is filled with inaccuracies, and called Dicke a critic of general relativity. No, he proposed a scalar field addition to GR as a test bed for GR. We test theories, we don’t believe them! Dang, what a bunch of crapolla. It even has some creationist stuff in there. Check out the counter examples to relativity
http://www.conservapedia.com/Counterexamples_to_Relativity
#22 illustrates the writer has no understanding the spacetime thermodynamics of black holes. You have to like the action at a distance of Jesus Christ — bound to be a canon of physics in a future fundamentalist Christian America..
LC
Yeah, I saw that when Dr. Phil Plait mentioned it on his Bad Astronomy blog last August; the number of counter-examples then was 29!
Also, the entire entry in Conservapedia for the “Rocket” article is:
Note the first line: “A rocket is an object which gains thrust by expelling a hot gas out of its back.”
Yeah, just like a creationist/conservapedian when talking about ‘science’.
A man may break a word with you, sir; and words are but wind; Aye; and break it in your face, so he break it not behind
William Shakespeare — A Comedy of Errors
Heh. The Bard was, indeed, a master of eloquent words!
Heh. The Bard was, indeed, a master of eloquent words!
There is also the Bard with, “Blow winds, and crack your cheeks! Rage! Blow!
W. Shakespeare King Lear
And another writer I tend to admire wrote:
Our purpose in life is to fart around, and don’t let anyone tell you otherwise —- Kurt Vonnegut
LC
I see there has been quite a few replies to my question. Most seem to confirm what i understood of the article, thanks a plenty to all of you. It is a kind of scary thought, really.. It gives the phrase ‘vast and empty void of space’ a whole new meaning!
“To discover different and sometimes simpler possible explanations, I think more alternative theory needs to be evaluated, many of which can only be found in alternative rather than mainstream journals and publications”.
What the authors have done is show that the observations place a limit on the time variation of a parameters. That result is not theory-specific, it argues against all theories which predict variation outside those limits, conventional or otherwise.
The trouble with what you suggest is that many of the “theories” in alternative publications are nothing more than vague ideas. Unless they have worked out the maths, it’s not possible to evaluate them because they make no numerical predictions.
Proponents of any theory must of course be responsible for doing their own work to show that these observations do not falsify their model.
Thanks for your comment,
“…..many of the “theories” in alternative publications are nothing more than vague ideas. Unless they have worked out the maths, it’s not possible to evaluate them because they make no numerical predictions.”
I agree, but also there are at least a half a dozen mainstream alternatives as to the cause of dark energy, none of these ideas were discussed either. Even if the maths are worked out few have the expertise to analyze and understand it, even mainstream practitioners will not take the necessary time to analyze the math even when published. It’s where that it is published that controls the volume of readership that can give a model recognition. I know since my own model has the math which much better matches observed reality, makes many new predictions, and does away with the dark energy idea. Take a look if you wish: pantheory.com, view the category “technical papers.”
During that “previous decade” the useful alternative theories there was were rejected by the data. The article is perfectly fine, lest you argue that we should continue to address phlogiston theory every time we discuss redox reactions.
We know that the standard cosmology works, we don’t take that as “belief”. Now, if you have ideas that you claim ar as successful for explaining data, by all means publish them and let first peer review and then consensus be the judge.
But a science blog is a poor place to discuss such speculation.
Also, the reason some of these theories are accepted is precisely _because_ they are simple. A universe are either expanding or contracting or, unlikely, finetuned. Observers would only exist in the former. It also explains the thermodynamical arrow of time, so what is not to like about it?
“…a science blog is a poor place to discuss such speculation.
Also, the reason some of these theories are accepted is precisely _because_ they are simple. A universe are either expanding or contracting or, unlikely, finetuned. Observers would only exist in the former. It also explains the thermodynamical arrow of time, so what is not to like about it?”
I think observers could exist in any type of universe you mentioned. Dark energy and dark matter are generally unknowns and unrecognized as to their character, if they exist at all. A cosmology that explains all facets of observed reality as well or better than the standard model, and one that needs the fewest hypotheses (such as Inflation, dark matter and dark energy for instance) — all else being equal, is probably a better model.
The arrow of time can be equated with change. Changes cannot be reversed without making new changes. In this way your arrow of time analogy I believe is totally correct. I believe accordingly that Time has no other meaning to it than “an interval of change.” Without changes in the universe, time has no meaning to it and cannot progress or have existence.
You still don’t point to published theory.
[As a technical point, contracting universes are possible in eternal inflation. But they are brief excursions at the local end of inflation, which do not expand much outside of a Planck volume AFAIU. So no observers.
Finetuned universes are unlikely, modulo we do not yet know how to measure probabilities over infinite universes.
Expanding universes are, to the best of our knowledge, it.]
“You still don’t point to published theory.”
My own model is a universe that is generally a steady-state model which is at least a thousand times older than the BB model but still is finite in age. There is expansion to it but probably not in the observable universe and no accelerated expansion or dark matter. The book is also published online free in its entirety at pantheory.com.
The model needs no fine tuning since my own model of gravity accordingly is a pushing force that works in a non-linear manner for rotating bodies and in a vortex fashion at galactic scales. All the math is also at the link indicated above if you are interested.
I think here we can discuss dark energy and be on track but for other questions or discussions if you wish, anyone can e-mail me at [email protected]
If I’m not mistaken we have had several in-depth discussions several years back when you were granted the O.M. (order of merit) designation following your name — or was it somebody else?
best regards, forrest noble
The nature of dark energy I outline above. Using Newtonian analysis it turns out this captures the basic features one may calculate in general relativity. There is an absence of the –k/a^2 term in the Newtonian analysis, but since space is observed to be essentially flat setting k = 0 is acceptable. The curvature of spacetime has flat spatial surfaces, but in a foliation the expands each one relative to the other in the future time direction.
The comments about GPS are strange. I worked on this for some time. There are a series of corrections introduced to recalibrate the large scale time calculated from atomic clocks. If this were not performed the location of regions on the Earth would drift.
Conservapedia is not a particularly reliable source for any scientific information. This is a politically loaded website that passes itself off as a credible alternative. Even this page on relativity is peppered with negative statements and political nonsense that are either factually not correct or irrelevant to the actual physics.
General relativity is a classical theory, and where it probably exhibits divergences from reality is on the quantum level. This may connect with cosmology on the large because the vacuum structure emerged from a quantum amplitude in the most early time of the spacetime cosmology.
LC
Although the quote that I took from this web location seems correct, on review and also based upon your comments, I realize that there is a political agenda to this site so if I use this site again it will be only for my information and I will find references from other sources. Contrary to others opinions and changing the subject :), I find wiki as one of the most informative locations anywhere on the web since I have contributed to its text :).
Wiki requires total references for all which is posted. If an editor cannot follow your information posted based upon you references they will delete your comments within a few days until you can show all the details of your sources if not adequately explained in your reference text that is not published. Sometimes the explanations of how and why references are used is much longer than the text itself. Wiki is entirely based upon mainstream published papers and published information from acceptable sources.
After maybe a year of successful addendum’s to Wiki you get the total “hang” of it and your material will be judged with less rigor. After a couple of years if you wish so, you might become an editor for others. I think it’s a very good system totally based upon academic references.