So, are these things that make you go hmm? or just bunk?
So, are these things that make you go hmm? or just bunk?
Quick, someone tell A.Dim.Astronomers call this boundary the Kuiper cliff, because the density of space rocks drops off so steeply. What caused it? The only answer seems to be a 10th planet. We're not talking about Quaoar or Sedna: this is a massive object, as big as Earth or Mars, that has swept the area clean of debris.
Actually, I've never heard of the "Kuiper Cliff" before. I think I'll do some googling . . .
A mix. Some are simply experimental results that, while anomalous, may yet be explained by mundane causes or by mild adjustments to current theories (Pioneer anomaly, tetraneutron, the wow signal). Others are theoretical ideas that may or may not survive as more data is accumulated (dark matter, dark energy).Originally Posted by N C More
Some are simply junk science that refuses to go away (homeopathy, cold fusion). Despite what David Nagel of GWU says at the end of the article, the experimental case for cold fusion is is far from bulletproof. It's more like bullet-ridden. The comparison to superconductivity is especially egregious. Superconductivity was a well established effect with a strong phenomenological basis even though there was no complete theory that explained it until Bardeen, Cooper, & Schrieffer. Cold fusion has nowhere near the same status. While it didn't slam the door on CF research, the recent DoE review of the last 16 years of of work in the field found that "the effects are not repeatable, the magnitude of the effect has not increased in over a decade of work, and ... many of the reported experiments were not well documented." Doesn't sound like a ringing endorsement to me.
:-? :-k ](*,) :-s
I'm sure junk science will go away with its tail between its legs once it has been properly refuted.Originally Posted by Eta C
I admire your optimismOriginally Posted by Eroica
Hmm, I'm no rocket scientist, but if light were travelling for 14 billion years in opposite directions, wouldn't the distance between them equal 28 billion light years?Originally Posted by From Article
I found it very interesting what Michael Martin Neito had to say about the "Pioneer anomoly"...
Of course I hope it is due to new physics-how stupendous that would be. But once a physicist starts working on the basis of hope, he is heading for a fall.
That was my first question when I entered this board. It turned out I was wrong, as in the meantime the fabric of spacetime is stretching (at least, that's what I understood of it). So the size of the universe is now 70 (or was it 170) billion lightyears across. I wonder if one day, the fabric will rip apart and we will end up with two universesOriginally Posted by Metricyard
I have a couple of questions about #2 The horizon problem. The website says:Originally Posted by Metricyard
“OUR universe appears to be unfathomably uniform. Look across space from one edge of the visible universe to the other, and you'll see that the microwave background radiation filling the cosmos is at the same temperature everywhere. That may not seem surprising until you consider that the two edges are nearly 28 billion light years apart and our universe is only 14 billion years old.”
That puts us in the dead center of the universe. Do they now believe we are in the center? The last I heard regarding the most distant Hubble galaxy photos, there is no “edge” to be seen in any direction, so why does New Scientist think there is an outer “edge” to the universe and that we are in the center?
Also, how do they know that “the microwave background radiation” fills the entire universe? All we can detect is the local radiation that hits our own satellite detectors. There is nothing that can tell our detectors if the same kind and frequency of radiation is hitting other satellite detectors circling another planet that is 10 billion light-years away from us.
No, Sam5, that puts us in the dead centre of the VISIBLE universe. Things that are farther away are invisible to us, as their light just hasn't gotten the tilme to reach us yet. Logically, as it all started at the same time (Big Bang, remember), the visual horizon is the same in every direction, placing us precisely in the middle.Originally Posted by Sam5
When you are on a raft in the middle of the ocean, you can see the same distance in every direction. Does that mean that you're in the middle of the ocean?
Originally Posted by Fram
Ok, I see. I misread their sentence. I see now that they said “the visible universe.”
What about the background radiation? Why do they think that this is not a local radiation phenomenon of our own particular galaxy or local group, and why do they think that satellites in a galaxy 10 bly away would observe exactly the same frequency of background radiation?
You have a point in that this is an inference and not a direct observation, but it is a pretty good inference insofar as we have a pretty good understanding of how electromagnetic radiation works.Originally Posted by Sam5
If the radiation were coming from our local group or galaxy then we would expect there to be a correlation between the intensity of the microwave background and the mass distribution of our group or galaxy. No such correrlation is seen.
Item 7 - Tetraneutrons
I can not comment on this item itself, but the last sentence makes me wonder about Michael Brooks' knowledge:
"And there is other evidence that supports the idea of matter composed of multiple neutrons: neutron stars. These bodies, which contain an enormous number of bound neutrons, suggest that as yet unexplained forces come into play when neutrons gather en masse."
In regards to the 'Kuiper Cliff' I was wondering if anyone could look up these papers for me and see what they have to say. I found a source that references them:
Allen, R. L., Bernstein, G. M., & Malhotra, R. 2001, ApJ, 549, L241
Trujillo, C. A., & Brown, M. E. 2001, ApJ, 554, L95
Maybe you can tell me something else. In the most recent Hubble photos of distant galaxies, located about 10-12 billion light years away, the telescope received regular light waves from them, waves of normal visible frequencies. So where does this “background radiation” come from?Originally Posted by CharlesEGrant
It may not be junk science.Originally Posted by Eta C
In 2002, another lab reported highly controversial evidence that acoustic cavitation in deuterated acetone induces deuterium-deuterium fusion (C&EN, March 11, 2002, page 11). "Our results involve such a different set of experimental parameters that they can neither confirm nor deny" that earlier claim of fusion, Suslick tells C&EN.
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Cosmic Mitosis?Originally Posted by Fram
These "Big unanswered questions" articles are always interesting. But I'd like to also see a "Big questions now answered" article, featuring some of the big discoveries of long previously unanswered questions of the last 5-10 years. What have there been? I'd put water on Mars on there.
The background is in the microwave spectrum and was originally observed with a microwave horn antenna such as is commonly used in microwave communications. These antenna are directional (though with a very coarse angular resolution) and the signal they picked up had the same intensity in all directions and didn't change over time. Because these early anntena had such a coarse angular resolution they were actually averaging the background radiation with radiation from point sources like galaxies and quasars. However most of the sky is empty, so the average was mostly from the cosmic microwave background.Originally Posted by Sam5
Later experiments had a much finer resolution and they could narrow down the field of view to individual regions of the sky that were "dark" (containing no point sources). No matter which dark patch they looked at they found microwave radiation with a spectral distriubtion matching the spectral distribution of a black body radiator at 3K to within experimental error.
As for where the microwave background comes from, I'm getting a long way away from my expertise, but I think the standard model is that the microwave background represents photons emitted during the first few minutes after the "big bang", and which then became thermally isolated from the rest of the universe, and now suffuse it as a kind of gas. The thermal isolation comes out of detailed calculations from quantum mechanical theory of the interaction of matter and light.
You may find this reference helpful: CMBR FAQ
Originally Posted by CharlesEGrant
Thank you for the information and the link.
Originally Posted by TriangleMan
"The problem of the ‘‘Kuiper Cliff ’’ — a sudden decrease in the surface density of planetesimals outside 50 AU—has been discussed extensively in the literature (see, e.g., Jewitt, Luu, & Trujillo 1998; Gladman et al. 1998; Chiang & Brown 1999; Allen, Bernstein, & Malhotra 2001; Trujillo & Brown 2001). We regard the statistical significance of the observed edge of the belt as still marginal at best (see Allen et al. 2001)."
Where the telescope ends, the microscope begins. Which of the two has the greater view?
From the linked article: "The trouble is that no one knows what could have made [cosmic inflation] happen."
No, the physics of 'false vacuum' actually predated Alan Guth's inflationary theory.
Guth realized that the physics of this false vacuum, this 'mathematical curiousity,' would naturally result in a universe which expanded at an exponential rate. The physics also mandated that when/if the state collapsed or transitioned to a lower-energy regular vacuum it would release a burst of non-localized energy, creating the conditions for a quark-gluon plasma -- the initial big bang hot quark soup.
One can ask why the nascent universe was in a state of false vacuum soon after it existed, but that's not really the same thing as saying that no one knows what made inflation happen. We DO know: the physics of the false vacuum forced inflation.
Sonoluminescence, which you are referring to above, is quite a different phenomenon than the so-called "cold fusion". And besides, you left out the most imporant part of the quote above:Originally Posted by Jim
Although a plasma must exist for fusion to occur, there must also be neutron emission, and "we have not yet detected neutrons," he points out.
IIRC(?) the "ambiguous at best" neutron results was the biggest objection to the initial publication of sonoluminescence-based fusion claims in Science a couple of years back. The original ONRL/RPI group did a follow-up experiment and that was also covered somewhere here on the BABB.
"Not as improbable as tetraneutrons, some might say, because in the standard model of particle physics tetraneutrons simply can't exist. According to the Pauli exclusion principle, not even two protons or neutrons in the same system can have identical quantum properties."
Hmmmmm. #-o Unless I'm remembering QM wrong, the pauli exclusion principle doesn't apply to bosons. Can anyone tell me who's wrong? The article or me?
Well, protons and neutrons are both fermions (spin 1/2), so the Pauli exclusion principle should apply.Originally Posted by Sock puppet
As a matter of fact, I remember theories of atomic nuclei that treat protons as a Fermi gas or apply the nuclear equivalent of the Hund rules.
BUT, the Pauli exclusion principle cannot be applied, strictly speaking, if the particles are interacting (I do not think that it can be applied to the quarks that compose the nucleons).
EDIT to add: If you have two nucleons strongly bound (which is possible, if I remember correctly), the pair form a bosonic particle. So, putting to of these pairs together does not violate the Pauli exclusion principle.
Thanks Sam5. It does appear that KBO density drops off significantly at around 50AU. The first paper briefly discusses four possible reasons for the 'cliff', including interactions with a star or large planet long ago clearing out the area beyond Neptune's gravitational influence. I didn't read anywhere that they thought it was a planet in orbit around the solar system though.Originally Posted by Sam5
KG034 is correct. When I refer to "cold fusion" I specifically mean attemtps to reproduce the work of Pons & Fleischman with electrolysis of heavy water and palladium (or other metallic) electrodes. That is the work that was recently reviewed by DoE and found wanting (claims of its adherents notwithstanding.) The sonoluminesence work Jim refers to is unrelated and, while still preliminary, has a plausible mechanism and may prove to be correct. Another "cold" fusion technique is muon catylized fusion which has been proven to exist, but does not proceed at a high enough rate to be an energy source. While these last two processes take place at low temperatures compared to traditional plasma-based fusion research and could be called cold fusion, that epithet should be reserved for the discredited work of Pons, Fleischman, and their adherents.Originally Posted by kg034
Surely homeopathy and cold fusion are not junk per se, but concepts which we may or may not understand? Junk science is surely nothing more than poor science method, by any second-rate scientist?Originally Posted by Eta C