Robittybob1

Thanks but it works! I was wanting Mordred's post on density waves so I used< site:scienceforums.net "density wave" mordred > in Google and it was the third on the list. Fantastic!

@Mordred was it you you suggested looking into "density waves"? I see there are many studies on density waves do you have a particular favourite? Post Script: @Mordred I found the post so no need to reply to this request thanks.

Is there a best way to get "search" to actually locate the topic you desire?

Just to have some idea what that cod word means https://nz.answers.yahoo.com/question/index?qid=20070628162522AAEGiwv I think we get the picture.

But imagine if all the dust has to move outward, and never inward and all the outward paths are blocked by more dust. The clearing of the inner SS could be a much slower process. First study I located seemed to turn up some very surprising figures where the surface rotation speeds of the young stars like the Sun matched that of a planet/debris at the Earth's radius, and far exceeded this speed as the contraction continued to a MS star. So would that even make P-R effect change signs? i.e The inner SS would be cleared outwardly and not inwardly anymore because the angle the photon takes hits the dust particle from behind and always speeds it up. Whereas the current Sun equatorial region moves slower than the dust so it strikes on the leading edge (in the diagrams on P-R at least). [This seems to be supported by what we see in the NASA images of dust discs. I always think it looks like material is flowing outward rather than inward.] http://articles.adsabs.harvard.edu/full/1993AJ....106..372E

That link to the Mossbauer rotor experiment made me think of this effect! https://en.wikipedia.org/wiki/Ives%E2%80%93Stilwell_experiment#M.C3.B6ssbauer_rotor_experiments If the Earth moves around the Sun at = 2.978589 x 10^4 m/s. Surface of the Sun moves at (kilometers per second)…………………………………….….. 1.9 km/sec So how much faster would the young Sun be spinning? http://spacemath.gsfc.nasa.gov/weekly/4Page1.pdf That brings up a whole lot of questions that need to be answered: Does that mean the direction photons emanating from the Sun is not radially but has a element of forward motion for they came out of a moving surface? So does every interaction of a photon on to a particle of dust would have a component of momentum in the forward direction? Could a young sun could be spinning at a rate that far exceeds the current rotation rate? Could this spin rate be due to the infalling matter adding extra angular momentum to the Sun How fast do young stars rotate? Is the Sun losing angular momentum as it radiates its energy and mass? Could these effects nullify P-R drag in the early solar system, but would be effective under the current spin rates? All I was wanting to know was did the Early Solar System have dust obscuring the PMS Sun, thereby allowing a habitable zone closer in? I think this dustiness is a taken and then I'm asking the experts whether the P-R drag would be less likely to clear the inner SS in a situation with a larger faster spinning young Sun? If that was so could it be argued the dust would remain for a longer period than is being predicted using the current Sun parameters?

Is there any actual experimental results which show that photons released from moving material has a higher frequency in the direction of travel? Was this the Ives Stilwell experiment?

This review mentions some terms that could be studied: That is an interesting idea where the disk clears from the inside out as giant planets are forming within the disk. The other idea that the leading edge of the protoplanetary disc is being dissolved away through photoevaporation. In the paper above it also mentions the Yarkovsky Effect. Diagram of this effect on this site.http://earthsky.org/astronomy-essentials/the-yarkovsky-effect-pushing-asteroids-around-with-sunlight It seems that the push is dependent on the object rotating in the right direction. The differential Doppler effect that is from the energy levels from photons from the two hemispheres of the Sun (i.e. the side coming toward you and the half going away. The energy is higher on the approaching side.

I'll look at that paper today, but last night I drifted off to sleep again thinking about the analogy of a shooter positioned on the back of a speeding truck. If he fires forward the bullet is said to add the muzzle velocity to the speed of the truck, but if he fires to the rear the bullet might have the same muzzle velocity but you have to subtract the speed of the truck to the effective speed of the bullet. The bullet has different speeds (note I realise light changes frequency rather than speed) but the analogy still holds. Which direction has the most magnitude change in the momentum of the situation? I'll leave that question with you guys while I read that paper. In your explanation above does the "narrow range" of particles affected by PR drag have no effect on the physical appearance of the clearing of the inner solar system of the debris dust? Pavelcherepan did say the clearing was from the "inside out". I take that to mean the majority of the mass is moving away from the star. Yet PR drag is meant to clear the solar system in the other direction. The article is great and goes into a lot of detail, strangely enough I liked the last sentence of the summary "....until these problems are solved, the life history of a typical member of the interplanetary complex will remain obscure." This work must have been lost on the majority of the others for they are still on about the P-R effect. It is definitely not a paper I can digest in an hour or two! I was looking for an argument against my concept that the incident photon increased the gravitational potential of the particle. Maybe I was wrong about that .... grrr! If photons produce a drag so will the effects of the neutrinos. I have hunch the physics will be identical yet I was hoping neutrinos to be the mechanism that contributes to the separation of the protoplanetary dust disc from the PMS star. But they seem to be produced too late for the separation has already occurred long before the Lithium fusion occurs. I wonder what the technical term is used for that separation so I can look it up? That is a particularly important stage in the Sun's development, it should have a name! Is this the point from which we say "the Sun has formed"? Is the P-R drag contributing to this separation if so the Sun moves away from the disk faster than the infall of the disk or is the infalling of the disk arrested by radiation pressure so the disc slows and the Sun slips away? These are just ways I'm trying to understand the physics of the situation - so it might seem childish but truly it is important to understand the cause of this separation.

This is what I have been reading all day, paper after paper saying the same thing but when you look at any image of a debris disk the material seems to be clearing in an outward motion rather than in toward the star. Go back to physics: So something happens inside the particle to release a photon, why would it have more energy in one direction as opposed to another. Is there some other physics situation that has a similar effect? If it is some quanta of energy say due to an electron orbital change, why would the energy change with direction? I appreciate the photon will be blueshifted to the forward and redshifted to the rear, but the energy given to that photon must be the same for it is just one event within an atom. I'm struggling yet no one else seems to.

One of the better images for the day was the picture of B Pictoris. http://www.nasa.gov/sites/default/files/thumbnails/image/hs-2015-06-a-print.jpg That star is in the main sequence stage and yet is still surrounded by the dust disk. The cross sectional view definitely has the appearance of particles flowing outward rather than inward as was predicted by Poynting-Robertson Drag (PR drag). I feel that even though just about every paper I looked at today mentioned the PR drag none could really explain it fully. Most of the particles some way or another end up in belts of gravitational resonance and stay there until attracted to a planet or become sublimated. These belts of dust definitely could shield a planet as is found in Beta Pictoris. So I still feel that the situation for the planets during the PMS phase, even though the Sun was larger and produced more illuminance the terrestrial planets could quite well have been protected by residual dust from the debris disk and from the abundance of comets in the early stages of the Sun's development, and this was even before the Late Heavy Bombardment (LHB).

Thanks for that analysis.

This science paper discusses and examines the evolution of the dust disk and goes into the physical processes in section 2 "Physical Processes acting on Dust" http://arxiv.org/pdf/1203.0005.pdf Is that paper peer reviewed? "Dusty Planetary Systems" It seems very logical and well written but what do the experts say?

No there are problems of accessing the original papers, then they cover quite a narrow topic in extreme detail. I feel that after a few more years I might be fluent in all the vocabulary they use so that they will have a total meaning. Wikipedia represents the current state of knowledge. OK the articles can be revised but at least it is all referenced at the end of the article. These sites have the information at the level of complexity that I am able to understand ATM. I am mostly interested to understand the logic of their arguments. I am also interested to know what the people on the forum are thinking, like in this discussion what is the event that confirms to you the Sun has formed? At least Pavelcherepan has responded but the rest of you have not said anything. There seems to be that very important event of the Lithium burning which is one of the most violent events in the Sun's history. I think that is the event that I had been timing events from, i.e. prior to that event or after that event but there is no timing for that event in the general sites. They just say the Sun formed after a million years after the nebula collapse, so without a doubt most events in the Solar system happened after the Sun formed but what were the events that happened between that and the end of the pre-main sequence stage? For that is the stage we are in now, and I think when people think of the Sun forming they think of it as it is now. I intend to look at scientific papers but I need to understand the basics and the common concepts first. The other thing that needs more research is the time involved in the clearing of the inner solar system (SS). For it would not be such a clear correlation between the illuminance of the PMS sun and the temperature on the inner SS planets if there was significant dust blocking the radiation. It would take a considerable time for the dust to clear, and in the meantime dust would scatter light into space. Would planets like Mercury and Venus have been within a habitable zone if that factor was taken into account yet it is not mentioned in this talk on the habitable zones of PMS stars. Thirdly there maybe some value in following up on the possible effect of the Solar Neutrinos. Probably beyond my scope and expertise.

By "hotter" I mean that to be the effect on neighbouring planets. If the PMS sun is brighter and bigger one study seemed to suggest the inner 2-3 planets would have been too hot for life during the PMS stage. Can you have bigger and brighter without being hotter? Or are you just saying the total amount of light from the larger surface although dimmer (on a watts per square meter basis) will produce more light because of the increased area? That will still make neighbouring planets hotter will it not?

Call it evolution. You know I always treat your posts with the respect due to them. I can never fully agree with you though for I have been working on this 'alternative' set of hypotheses and if one fails the whole lot fail. Parvelcherepan has introduced an idea in this thread that has stumped me "hopefully not fatally" and that was about the size and brightness of the pre-main sequence Sun being bigger, brighter and hotter than the main sequence Sun. Will I survive? I had only woken up during the night concerned I had made a mistake in what I had written just before retiring and I hadn't got back up to Parvel's post yet. But I have now read it and appreciate what Parvel has said but I wonder why the margin of error is not more often discussed along with the date. For example we get told 4.57 billion year but not 4.57 +/- 100 million years. I'd be surprised if there really needs to be such a wide margin of error though. In #27 http://www.scienceforums.net/topic/93429-what-dates-are-accepted-for-the-age-of-the-sun/page-2#entry905016 The Wikipedia reference gives a 50 million year margin of error i.e. +/- 50 million years, is that what Parvel intended to say?

I did make an unintentional typing error there I'm sorry. I was supposed to say 4.6 rather than the outlier 4.7. I was more concerned not to have hints of speculation in my writing so much so I was distracted from the facts I was trying to say. Now is the 4.6 billion years the same as 4.57 billion years used in #3 by Pavelcherepan?

@Pavelcherepan - we are on a similar track now. So this pre-main sequence stage can go on for up to 100 million years. So it seems that when they say when the sun forms they are talking about events that happened prior to the start of the pre-main sequence phase (PMS), that is up to 100 million years prior to the start of hydrogen fusion. With Lithium burning at the end of this PMS phase. When do you think the first 4 planets formed in our solar system in this time sequence? During the protostar, pre-main sequence or Main sequence stages? So in your opinion you date the Sun from the time it became a pre main sequence star. The dating of the Sun is based on dating the age of meteorites. They seem to add about 10 million years to the oldest samples found. I don't doubt the dating of the meteorites but how do they know to add time to that date and call it the date of the Sun? Could meteorites be formed before the Sun separated from the protoplanetary disk? What degree of accuracy has your date got? For you haven't got much time to play with for the stage prior to that was just 1 million years long. http://hyperphysics.phy-astr.gsu.edu/hbase/nuclear/meteorrbsr.htmlgives a figure of 4.7 billion year for old meteorites. That seems to be well before the age of the Sun in your post. Do those figures seem right to you?

The whole idea was from the quote: http://www.scienceforums.net/topic/93429-what-dates-are-accepted-for-the-age-of-the-sun/#entry904859 that said neutrinos will be coming out from the Sun for 170,000 years before the light does, so that might be the early stages of main sequence rather than the T Tauri stage. It wasn't clear in the original quote and backs the purpose of this thread: to work out precisely when the various events occur rather than just saying "when the Sun formed" The question is did the Sun go through the T Tauri phase? It has the right mass to be a T Tauri star but the Lithium burning is during the late pre-main sequence stage which can last up to 100 million years. The fusion reaction in Wikipedia has a neutrino (I think) there is a "v" which I think is the symbol for neutrino. https://en.wikipedia.org/wiki/T_Tauri_star#Characteristics So any thought that it takes just a million years for the Sun to form seems rather a massive underestimation.

I wasn't expecting you to do the calculations I was seeing if anyone has done it. There was one forum that looked into this. So I will divide that by the number of square meters of the Sun' surface. That will give me flux per m^2. I'm too tired to go on today sorry.

The energy level discussed by Imatfaal was lower than what I saw in Wikipedia http://www.scienceforums.net/topic/93429-what-dates-are-accepted-for-the-age-of-the-sun/#entry904968, and also Swansont seemed to suggest they were low too. The flux of neutrinos near the Sun could be significant. I have no complete idea and will need to think about it and even try and put some figures on it. Neutrino flux per square meter at surface of Sun. Get an estimate of the mass of the dust disk per meter in contact with the protosun. Assume that the dust disk is primarily in orbit around the Sun. Calculate what sort of pressure could be expected if 100% of neutrinos absorbed by the dust disk within each 1 m^2 segment

Thanks for trying. So you end up with some bits that move inward, some that don't move, and others that get blown to the outer reaches. That still means that there is only partial clearing at best unless all particles are of a specific size. Let's move on and we'll tackle this again sometime. I'm learning about neutrinos and I've just heard they are involved in supanova explosions so they seem to have the power to move stuff around alright. Do you think we've missed a phase of Sun formation where the neutrinos are forcing the matter in the dust disk back against the infall motion that was part of the nebula collapse? Since the Sun is all intents not shining (maybe just glowing hot) is this a phase during the late protosun period or the beginning of the T Tauri period? How do we define the start of the T Tauri period?

From Wikipedia https://en.wikipedia.org/wiki/Solar_neutrino But as I understand it the PR drag makes the dust fall toward the star. That seemed to go against my perception of solar winds etc. I can't see how moving dust inward clears the inner region for there will always be more coming in from further out. So how does it clear from the inner going outwards using the PR drag? Can you really understand that? I personally find it difficult. Maybe I need someone to explain it in another way. But I do think you are right for the volatiles and gas they go outward, and really when I imagine a wind made of gas and volatiles I can't see why that wind doesn't blow the dust outward as well. It seems illogical to have wind in one direction and the dust moving against the wind. But that is said just from my confused state trying to understand the Poynting Robertson drag.

Is it the aberration explanation or don't you accept that the Poynting Robertson Drag has got anything to do with the clearing of the inner solar system? https://en.wikipedia.org/wiki/Poynting%E2%80%93Robertson_effect I found it difficult to accept in anycase. I'll see if I can confirm your other ideas re the contraction stopping once the main sequence starts. So you would not expect a stage of Sun expansion during this heating stage. Still could add up due to the share number of neutrinos so close to the Sun. But thanks for converting that momentum into a change in velocity (which in the case of the dust disc is converted to an increase in the orbital radius (more gravitational potential energy, I think??) I'll have to think it through a bit more. So what is the energy range of the neutrinos emanating from the Sun? We'll need to see if this has been measured. So in the experiment did you get a change in the position of the "parent nuclide"?

Chlorine reacts with neutrinos producing Argon Does this logic work? 37Cl is a very common isotope. All the neutrinos coming from the Sun would have a momentum heading in the outward direction (away from the Sun), but the neutrino released after the de-exiting would presumably be in random directions. This would suggest there is a local net change of position of the chlorine atoms