Robittybob1

So what about that request for help in #128, will you help me tomorrow like in 24 plus hours time? We should go through that paper and give the variables some values and see what happens. I find it confusing for they too say it could be a driving force or like the P-R effect a drag, and then one sentence later he says the P-R effect is always > DDE so he had contradicted himself in just two adjacent sentences IMO. It could be that it cancels the P-R effect but never exceeds it, that could be the result (and what he is saying), but either way I want to see for myself using the predicted size and spin rate of the PMS Sun and see why it can never exceed the P-R effect. Did you notice what seemed like an error in the paper? I've never used math on rotating frames of references (RFoR) before. The last YT lecture (before dozing off) on them started talking about fictitious forces are we going to run into those sorts of problems?

Mordred did you access that paper https://www.researchgate.net/profile/Steven_Soter/publication/23871263_Radiation_forces_on_small_particles_in_the_Solar_System_A_re-consideration/links/557c962708aeb61eae236401.pdf In there are some formulas for the calculation of the DDE. Would you be so kind as to help me with them (mainly getting the correct values for the variables? Each equation has a number so we could decide which ones are important and go from there. It will be in a couple of days for I'm busy tomorrow. I understood most of this. The only question I have is about the Sun. "From the reference frame of the Sun" is the Sun spinning on an axis or is it fixed? Is it a rotating frame of reference?

Well can you explain why the DDE adds more momentum to the dust particle when the photon comes from one side of the Sun? Slow down and go to the topic for today DDE please. wikipedia doesn't have much on it. This is not just for the benefit of a single dust particle but just about every photon emitted from the Sun is effected in some degree by this DDE. http://adsabs.harvard.edu/full/1984CoSka..12...99K "Nongravitational effects affecting small meteoroids in interplanetary space" Mentions DDE "The radiation force on small particles" http://www.sciencedirect.com/science/article/pii/0032063381901446 you might have access to that paper. "Radiation Forces on Small Particles in the Solar System" https://www.researchgate.net/profile/Steven_Soter/publication/23871263_Radiation_forces_on_small_particles_in_the_Solar_System_A_re-consideration/links/557c962708aeb61eae236401.pdf I must admit there is a paucity of papers on the effect.

You are now asking questions about things I have no knowledge of. [Mordred - are you a moderator?]

I think you are wrong. It might be "emitting" that wavelength but it takes more momentum away from the Sun for the frequency is increased and a photon's momentum is directly proportional to it frequency. p = E c = h ν /λ ν = h λ

He doesn't need to talk about observers moving because there are no observers as such, for the radiation from the sun shines throughout the solar system , galaxy or universe. It just radiates out into space.

I don't know what you are saying exactly sorry. The "observer" in the case I'm claiming does not move. It is the radiation from the sun that changes, in the prograde direction of rotation the radiation is blueshifted and in the other (retrograde) direction it is redshifted. Do you not understand this? This is the principle behind the Differential Doppler Effect. Are you denying that is a valid effect? Are you saying I have misunderstood the DDE? Don't try and confuse the situation please.

How can you say that? I have provided links all day. Mordred's equation in this post http://www.scienceforums.net/topic/93429-what-dates-are-accepted-for-the-age-of-the-sun/page-6#entry907078 didn'tprove anything so that did not help the discussion. You know how to do LaTex, I don't, so I can't provide formulas sorry.

THE ROTATION PERIOD DISTRIBUTION OF PREÈMAIN-SEQUENCE STARS IN AND AROUND THE ORION NEBULA KEIVAN G. STASSUN,1 ROBERT D. MATHIEU,1 TSEVI MAZEH,2 AND FREDERICK J. VRBA3 So they are saying of the stars they looked at they had periods as short as 0.5 day up to 10 days. This must be compared to our Sun with a rotation period of about a month. .

Prove to me that the blueshifted photons don't have more momentum than the redshifted ones. It doesn't matter that the average is the same because all the blueshifted ones have a similar angular direction, all are prograde. So where does this extra momentum come from. It seems virtually the same physics as the P-R effect but on a much grander scale.

That little bit is nothing of the magnitude we need to account to the difference between young stars and our Sun.

So do you think the Sun orbiting the Earth is uniform motion?

Prove it.

There is some very interesting things happening at the start of the graph. The first 300 million years has a different slope (all 3 parameters) than the rest of the graphs. It says nothing about angular momentum. Surface temp is about the same in the PMS period as it is now from the 300 million mark. Luminosity is rising from the 300 million mark. (but if the size was larger total luminosity could have been higher at the start.) The radius is increasing from the 300 million mark - that could slow the Sun's rotation rate. (it would depend on mass redistribution.)

Does the Sun orbit the Earth?

Does this paper give us the clue https://www.researchgate.net/profile/Keivan_Stassun/publication/249224572_The_Rotation_Period_Distribution_of_PreMain-Sequence_Stars_in_and_around_the_Orion_Nebula/links/53e11aaf0cf24f90ff60df92.pdf New stars are spinning much faster than the Sun. Where does this momentum go? The DDE could be one of many causes of the Sun's momentum loss, photons released in the forward direction on average take away more momentum than the photons coming from the backwards directed ones. That might just be one of many factors. But our work on the DDE in this thread has already been evidenced and can't be ignored.

I know that, but even the Earth has gone from something like a 5 hour day to a 24 hour day over the last 4 billion years. So how much has the Sun slowed down? What I'm saying is that any calculation using today's Sun parameters could be an underestimate of what was happening 4.6 billion years ago. Well it was already proven by the study on the spin rates of PMS stars. I'll edit the post when I get the link again but I'm sure I've already posted it in the thread. (It wasn't this one but says something similar) http://spacemath.gsfc.nasa.gov/weekly/4Page1.pdf I don't know why the Sun could have slowed its rotation rate. (Moderators: Another thread maybe? But in some ways it is quite within the scope of this one too. Can we discuss the loss of the Sun's angular momentum in this thread please?)

No I believe it to be different. They spin faster as they shrink but somehow that momentum has been lost now. (We will need to look into this again and clear it up, for I want to be accurate and sure.). I covered that earlier (in this thread) the Sun's rate of rotation appears to be slowing, for it was faster early on in the PMS. The temperatures are right up there Pavelcherepan has given some estimates of the surface temperature of the PMS sun. I can't remember exactly but they were in the order of 5,000 - 10,000 degrees C. It was being heated by gravitational compression, energy has to be lost to allow it to collapse. (we will have to revise this as well).

I've been looking for papers that compare The differential Doppler (DDE) effect to the P-R effect in pre main sequence stars. DDE has many uses but there was nothing so far that I saw on it function in PMS dust disk. I am thinking if the dust disk is thick the star are harder to see and harder to study for there was a study on the debris disk of MS stars where the dust remaining is called the debris disk. But the two effects P-R and DDE both move the particles in opposite directions so that could contribute in the overall slowing the clearing of the dust in the inner parts of the dust disk once separation from the PMS star has occurred. As it was pointed out earlier the PMS sun would be much larger and spinning a lot faster so from the way that the DDE works the distances it operates at would be proportional greater and the strength of the blueshift greater. i.e. I'm not sure how much larger the PMS sun was but if it was 12 times as wide as one estimate (but that was too early IMO) you could estimate that the distance it operates at could be 12 times as far (I'm not sure now whether the size was volume or diameter, sorry, but the concept remains true the wider it is the more distant will its effect be). There is such a vast size reduction of the protosun in that period (starts off 1000 AU as a nebula and ends up PMS <1 AU just as rough concept). Then what is the size reduction rate in the PMS stages? Do you know the rate of contraction of the PMS sun during the PMS stage? Does anyone know of these estimates please?

So did you agree with both statements in #91? Wavelength and frequency are inversely related -- so yes Averaged the red and blue shift with be the same regardless of spin rate - I think you're right. Unfortunately we are not considering long distances but the region between the Sun and the first few planets. True or false? "The higher energy photons will becoming from the point behind the dust for the dust and the star are rotating in the same direction. so the radiant pressure will be higher driving the dust to higher orbits." The name of the effect is the differential Doppler effect. thanks wikipedia: https://en.wikipedia.org/wiki/Differential_Doppler_effect

The idea of postulates comes close. Thanks to Google

Not only that but they seem to be tackling the most difficult of questions. So we are bound to come up wrong at times but it doesn't become a dogma until it is thoroughly evidenced.

Is this a true statement? If you are firing forward and rotating in the same direction, since the speed of light is limited to c, those photons (that leave the gun and hit a particle directly overhead) are going to be blueshifted compared to those fired straight up or worse still fired backward. There was a name for this effect, i'll see if I can find it again, but it relates to the hemispheres of the sun. The side coming toward you produces blueshifted light compared to the light coming from the side going away from you. So would this be a true statement? "That the degree of blueshift is dependent of the orbital speed (and particularly the tangential speed on the surface) of the Sun".

Thanks. I remember those demonstrations now. @Swansont - So does the position (distance from the center) and the rotational speed of the thrower make no difference to the path it takes? (Especially in a situation where the rotational speed of the thrower (not at the true center) can be varied independently from the carousel.) If I said "Increasing the thrower's rotational velocity is the same as changing the angle of firing the laser" i.e. firing it further ahead. Is that true? Note: I had not rejected Pavelcherepan's suggestion and I definitely wasn't sure of mine but now I recall the demonstrations of what you mention and the balls would definitely take a straight path but they looked curved to the thrower who was sitting on the carousel.

How can you tell? I know it is not true inertial motion but how can one tell whether they need to take the acceleration into account? (That is how can you tell from within the thought experiment) Did you try and figure out what direction one would fire the laser from the Sun to hit the dust particle to get the P-R effect to work? Later we will see what happens when the dust is not heliocentric, does that make any difference if the Sun is spinning faster, does it get somewhat harder to hit the target?