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Supernovae May Not Be Standard Candles; Is Dark Energy All Wrong?
StartsWithABang writes: The accelerated expansion of the Universe — and hence, dark energy — was discovered by taking the well-understood phenomenon of type Ia supernovae and measuring them out to great distances. The results indicated that they were fainter than expected, and hence more distant, and hence the Universe's expansion must be accelerating. But new results have just come out, showing that supernovae may not be standard after all. Does this mean dark energy may not be real, or that it may just be slightly weaker than we previously thought?
To me it seems to be used to explain the unexplainable, much like the aether of former times.
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"We" being nutcases, right?
No, the aether doesn't exist. If you're going to claim "the vacuum of empty space is the aether", then you'd be just as well calling it the FSM, and then claiming the same thing. Words are supposed to mean something. If you're gong to use a private language definition of the word, please stop talking to anyone.
According to Ethan Siegel, dark energy isn't written off, we just know a bit more about it.
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On the internet, apparent aether refers to whatever people want when they want to sound disparaging about a particular idea they don't like. Within physics, it pretty specifically refers to a medium for electromagnetic waves, that for most of its versions in history was a fluid of some type. If people on the internet want to redefine it to mean anything permeating space so they can treat things like dark energy, they should at least be consistent then and acknowledge things like gravity and wavefunctions that also permeate space, among a whole bunch of other physics concepts. In that sense, we've known the "aether" to be real since components of Maxwell's equations started coming together with ever present electric and magnetic fields.
The summary has a link to a paywalled article (silly Ethan). The full article is freely available to all on the arXiv preprint server:
http://arxiv.org/abs/1408.1706
I'm peripherally involved with the supernova field, though I study only the nearby examples. There has been for years the understanding that IF a difference should arise between the nearby events that we can study well, and the distant events which appear dimly and vaguely, AND if we did not realize that such a difference existed, THEN we could reach incorrect conclusions.
Scientists in the field have worried about this for years. It's not a sudden new realization.
It's very pleasant to see that a space telescope -- SWIFT -- which was built to study one type of object (gamma ray bursts) has turned out to provide vital information on a different type (supernovae). Since it is in space, it can detect ultraviolet light, and so show us that some nearby supernovae emit different amounts of ultraviolet light, even though they appear similar in the optical region. This UV difference hints at differences in chemical composition between supernovae, which may indeed be significant when we try to study very distant events with other telescopes.
Fortunately, light from those distant events is redshifted into the optical regime, so we can use very large ground-based telescopes to see the same UV light and compare it to the nearby events.
It's a very interesting field to follow: things change on timescales of 3-5 years. And yes, we are more aware of the uncertainties in the business than some news articles might imply.
Michael Richmond "This is the heart that broke my finger."
mwrsps@rit.edu http://stupendous.rit.edu
*If* this result holds up, it doesn't sink dark energy - it will only be a small correction to the measured value using this particular probe. We have multiple, independent measurements of the existence of dark energy, from the early-universe Cosmic Microwave Background, to the late-universe feature in the galaxy distribution called the Baryon Acoustic Oscillation. In fact, for quite a few years supernova haven't been the principle method of measuring dark energy, because we've suspected issues such as this.
*If* this result hold up, and corrected measurements of dark energy from supernovae are in tension is all other measurements, then that will be interesting and require further study. However, despite having the confirmation of the existence of dark energy for several years, we haven't measured its exact properties very well yet. These corrections will probably shift things around inside known error bars.
For all the aether-claimers: we don't know what dark energy is. We've observed an acceleration to the expansion of the universe and called it "dark energy". This is a name given to an observed phenomena. The Nobel Prize was awarded to the original supernovae groups because it has been *repeatedly, independently* verified, using completely different sets of cosmological probes. This is like observing and measuring the observational reality of gravity without having a theory to explain it, but that doesn't mean that gravity doesn't exist.
I find your lack of faith disturbing.
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The aether theories made some specific predictions, and even after several revisions to that, every single one was found to disagree with observation. Even if you attempt to rebrand some different new concept as an aether theory, that is just a semantics trick and doesn't change that original set of theories were found wrong.
No, science has never disproved the aether. It was ruled out for social reasons. When that social reality changes, science will probably bring it back. Yves Couder's experiments with silicon "walkers" bouncing on a liquid substrate, with which he can recreate Young's double-slit experiment on a macroscopic scale, would fit nicely with aether theory. But that fit is ignored by physics, because of the social ramifications of bringing back aether theory.
I don't know who's modding this up, or where you got the idea that Couder's experiments fit nicely with aether theory. The experiments have nothing to do with aether theory, other than showing some mechanical analogues of particular systems. They don't show a fluid basis for all of quantum mechanics, just a particular experiment. While the experiments are nice, this shouldn't be surprising considering the basis of quantum mechanics is wavefunctions, which do show a lot of similarity to waves in general (wave equations are a common solution in a lot of areas of physics, because it is such a simple and common differential equation). Heck, the Schrodinger equation and variations of it are used heavily in modeling water waves in certain regimes.
But this has nothing to do with the idea that mechanically there is a fluid providing the mechanism behind electromagnetism or quantum mechanics. At best you get to an interpretation of some aspects of quantum mechanics, but it doesn't make any observable difference and remains an interpretation.
This is rather unlike aether theories of yore which made predictions, predictions that turned out to fail. If after multiple revisions & variations, with multiple follow up experiments to each revision of theory resulting in disagreement and lower bounds, is a "social reason," then so be it. But that doesn't sound like what you are saying. Considering the famous Michelson–Morley experiment wasn't the start or the end of it, with many experiments both in the decades before and decades after, that wasn't just a group of theories failing for social reasons.
If it can't be falsified nor verified, then it does not exist.
A lot of people are not getting why Quantum "phenomena" can be explained as a wave on a medium (like water) and they think it's just happenstance and wave functions just crop up everywhere (yeah, sure, like the Golden Rule!).
If there are waves -- what do they propagate through? A particle doesn't lose mass propagating EM fields -- only energy, or more exactly; inertia or heat. Sound does not transfer in space, because it is a vacuum. But that's only because sound is a wave function that passes along molecules.
Shouldn't it be proved that there IS NO MEDIUM for waves like light to propagate through? Seems to me that the Photon as more than a "point at which a specifically tuned field collapses" is a more reasonable answer than making one band of EM field have a particle and not finding particles in microwaves (for instance). And as an exercise -- can someone explain WHY they oscillate back and forth as waves on an ocean do if there is not a medium? I can only come up with a way to explain oscillations in a vacuum by looking at a straight line in 8 dimensions -- which still doesn't rule out a medium in a co-incident dimensional group (another 4 dimensions).
Anyway, I'm frustrated because I can conceptualize most of what is said in Quantum Mechanics, and other than the math -- it sounds like they are describing a Platypus and not a beast that could actually live. There are indeed simple explanations that can satisfy the double slit experiment with waves alone, and also Quantum Mechanics -- as long as EVERYTHING is really a wave. And particles are waves -- they just fold in on themselves in our 4 dimensional space.
The thing I've pondered for the longest time is "why physics is a law"? -- meaning; why do things HAVE to be equal and opposite? We've observed that, and Newton and a few others have proved that it happens -- but I want to know why. And "how do things move" based on Einstein's theory of Relativity because, when I was 12, sure, I spent three days wrapping my head around the basic concept -- but it didn't make sense with a lot of different vectors. It took me years to realize it was another concept that people nodded their heads and echoed "E=MC2" without really understanding. You've got people who can't get beyond the accomplishment of understanding that two photons don't hit at twice light speed, and after that, they take a nap.
The idea that Space/Time stretches for two photons colliding but shrinks if they separate starts to break down if you think of a star where it's often the case that a photon is both arriving and leaving another at relativistic speeds. It means that EITHER; each particle has it's own relativistic space/time or motion takes place in a higher and lower dimensional group. And what does it mean to shrink and stretch space in such a small area?
However, if we say that SPACE is a thing and is moving; then relativity is the "pressure on space/time" -- and it works out a lot nicer conceptually to think of velocity and gravity as pressure. So as the Gravity goes up in a star, it takes more energy/speed to reach light speed -- and it works out a lot like turbulence. As a bonus, we can say that gravity on a planet or a star may have less effect on local objects than on the galaxy itself -- and thus, noting that a lot of galaxies are MUCH HEAVIER than predicted, we can be OK with the fact that gravity may be a lot more powerful than predicted -- but it's pushing on SPACE itself. Where there is a lot of matter and light -- there's more pressure and turbulence, so the objects are not being forced towards other objects. I mean, why don't electrons merge with protons and why didn't the Universe get all clumpy after the Big Bang? Math models predict what we see because they are tweaked that way. But If I've got a room full of magnets and toss them around, they clump up because ALL they do is attract each other. If Gravity is JUST an attractive force -- it's pretty lazy about it.
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No, science has never disproved the aether.
Inas much as you can't disprove anything. However, the isotropy of the speed of light essentially suck the ether as a theory, because the anisotropy of the earth moving relative to the ether was one of the big predictions, especially given Maxwell's laws. Then along came relativity and stuck the boot in.
The aether made predictions which didn't come true. The theory was modified to fir the observations, which is not ususual. However in the case of the aether it became more and complex and eventually, all of the phenomena were explained without the aether. That left the luminiferous aether as a really cool name but lacking any predictive or explanatory power, so it was dropped.
I think it's very unlikely the aether will return, because physics has moved on very far since the aether was the best explantion for the physics.
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