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Mordred

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Everything posted by Mordred

  1. Essentially correct. If you look at the clocks on that link and when the red signal is sent you can see both aspects affected. It's great to try to mathematically seperate each effect but all the effects occur. Dilation, delay in signal and contraction. If you think about that the observer sees all three. Regardless of who the observer is Alice or Bob observing their opposite signal.
  2. Yes speed of light is invariant, for all observer's. It appears what your missing is relativity of simultaneity. Ie when the events are observed to occur. "In physics, the relativity of simultaneity is the concept that distant simultaneity whether two spatially separated events occur at the same time is not absolute, but depends on the observer's reference frame." https://en.m.wikipedia.org/wiki/Relativity_of_simultaneity Look at the graphs and the line "Event B is simultaneous with A in the green reference frame, but it occurred before in the blue frame, and will occur later in the red frame." If you send just one signal the signal will occur later or sooner depending on the observer. In other words the two observers won't agree on when the clicks occur.
  3. The problem your having is thinking multiple body problems should all share a common centre of mass. In point of detail the use of CoM becomes impractical in multibody problems. Place five dots on a sheet of paper (random). Draw as many lines connecting those dots. (You should have four lines per dot) Now assume each dot represents objects of the same mass. So devide each line in half. Each of these points represent a different CoM. The net effect you end up with more Centre of mass relations than the actual number of objects. Now ask yourself How many different centres of mass relations are involved in the solar system? Count every individual planet/moon system if two moons influence each other count them too. Then count planet/sun, if two planets influence each other count them too. Far too many to mathematically describe under a single Keplar style calculation.
  4. Oh I agree there is some agreement with possible influences. There is a decent list in this arxiv article. Including Potential coincidence with ice ages and sunspots. http://www.google.ca/url?sa=t&source=web&cd=5&rct=j&q=LONG-TERM%20VARIATIONS%20IN%20THE%20GALACTIC%20ENVIRONMENT%20OF%20THE%20SUN&ved=0CCUQFjAEahUKEwjqqPCYt5HIAhXCOIgKHcsyDMA&url=http%3A%2F%2Farxiv.org%2Fpdf%2Fastro-ph%2F0601356&usg=AFQjCNEFruciU7uMVzqOOUr70mxLLD3VHQ&sig2=dyrkswouqIWiOo56vY6lrg Honestly though in my opinion we still need more data on the effects and possible influences. ( granted Shaviv did an excellent correlation to the ice age cycles with the data he had available) http://link.springer.com/chapter/10.1007/1-4020-4557-3_5 Last link is the pertinant chapter by Shaviv. I bought a copy few years back By the way +1 for an interesting discussion. ACME Though if we wish to further discussion the extinction events and possible influences we should start a seperate thread. We're running the risk of hijacking this thread from the OP
  5. I understand that, I'm speaking of numerous other related papers I've read on the subject, albeit other forums. If you dig into it there are dozens of articles. They all usually include the solar winds and the Oort cloud. Some include the DM disk hypothesis. Many include extinction events. All of The above isn't strongly supported. The movement itself isn't debated. The effects it has on our solar system, in particular to the extinction events is debatable. However a bit off topic.
  6. Yeah that's what I understand as well on the frequency. I've seen no counter argument on those figures
  7. ( The bobbing action itself isn't that mysterious. The problem is that there was a rash of correlations to extinction events proposed due to this passing through the galactic plane etc. That got everyone's attention on it.). Not always rational lol.
  8. I've seen this come up on other forums. The hypothesis is that a dark matter disk is involved. Also that this passing through the galactic disk also coincides with the extinction of the dinosaurs. Etc etc etc. I've yet to see any strong support of a DM disk, current profiles suggest a halo profile. However that's just a side note as all were interested in is the inclination bobbing action to the galactic disk mass. Try this thought experiment. Start with our solar systems momentum which has an inclination to the galactic plane. As it approaches the galactic plane it will gain momentum. When it crosses the galactic plane it's momentum carries it past the galactic plane. Then the mass tried to overcome that momentum. The result is it starts losing momentum until it starts heading back towards the plane. (Sinusoidal arc). Then when it passes the galactic plane the same process continues. So yes gravity does alter its course both above and below the galactic disk. However we also need to account for how gravity interacts with the solar systems momentum and direction. (Conservation of energy/momentum) That being said theoretically the sinusoidal behavior should gradually decrease in amplitude and the solar systems movement will become more and more aligned with the galactic disk. How long that will take? No idea without more accurate data and records of decrease in amplitude per cycle.
  9. ACG52 answered the first. As to the second the correct answer is ALL mass contributors of which Stars is just one. Source. Plasma which the stars are made up of is another. Their movement and gravitational influence combined contribute to how galaxies develop into into disks. Think about it. How do stars form? They form from plasma. So in order to form a star there must be sufficient plasma. I'm not positive on the exact % of mass the plasma is currently. Though it would have been higher in the past. This is why galaxy rotation curves are based on mass density, not star distribution. ( if you want to understand current star distribution, you need to understand the contribution due to plasma). Dark matter doesn't contribute to why the disk is flat. It does affect rotation curves though. Pop 1 stars are found typically in the disk. Population 2 stars are in random eccentric orbits in the bulge and halo. The categories are seperated by the elements that went into their formation. Hydrogen and helium is primary in pop 2 stars. Elements above helium are considered metals and are part of the pop 1 stars. Insofar as pop 1 stars have a higher Abundance of metals. Another aspect is the newer stars have the highest abundance of metals and reside closer to the galactic plane than older pop 1 stars with less metal abundance.
  10. As to the first question Why does the disk exist? All the mass started as a cloud yet later on forms a disk. The answer is rotation. Your understanding of the Earth/moon system is accurate. What I'm trying to get you to consider is that our galaxy started as a cloud, due to rotation flattens into a disk. The plasma flattens first. (Lighter material). However stars formed while the galaxy was a halo cloud. Not all those older stars have migrated to the disk. The same thing happens to the spiral arms. The stars cannot keep up with the plasma. Hence older stars are typically outside the arms and newer stars forming in the arms. When you look at where stars are currently you also need to consider where were they formed and the galaxy dynamics at the time of their formation. ( this includes the available composition of plasma) For example the majority of red dwarf stars we can't see. They are too dim. What is their distribution? "formation timescales to be placed upon the structures within the Milky Way, namely the Galactic halo and Galactic disk." https://en.m.wikipedia.org/wiki/Red_dwarf
  11. The only way to explain this is look at the Earth moon system. Ask yourself why does the Earth have a greater influence upon the moon's orbit than the Sun? Localized gravity can be greater than the global gravitational influence. Same with stars local clusters can overpower the outer regional influences. Creating locally bound systems whose collective mass is greater. Again due to f=ma they will accelerate at a slower rate than smaller clusters. The dark matter halo surrounds the galaxy, however the greater concentration of plasma is on the plain. However that plasma wasn't ALWAYS on the plane. Prior to becoming a spiral disk galaxy, the plasma was a halo cloud. Forming older stars outside of the disk.
  12. Not necessarily, stars do move into an out of spiral arms. Higher concentrations of mass certainly inhibit the tendency. However stars are not the only sources of mass. You also have mass due to plasma and the dark matter halo. The other aspect is not everything moves due to a force at the same rate. Remember f=ma, so larger mass objects will accelerate slower than smaller mass objects. Particles will obviously gain greater acceleration than stars. Hence density waves and the traffic jam analogy The reason the spiral arms are brighter isn't necessarily due to a greater number of stars within the arm. It's due to a higher concentration of plasma causing reflective and refraction of the light emitted by those stars. A good example is take a flashlight and blow smoke through the beam. Which is more visible? The region with no smoke or the region with smoke? The density wave causes higher concentrations of plasma, which aid star formation. However the wave moves faster than the stars, so it leaves those stars behind. Catching up to previously created stars.
  13. Your missing one key aspect of neutrinos they can decay into other forms of neutrinos. For example muon neutrinos can decay into tau neutrinos. Here http://home.web.cern.ch/about/updates/2015/06/opera-detects-its-fifth-tau-neutrino. Google neutrino oscillations The funny part about neutrino oscillations is an electron neutrino can decay into a muon neutrinos then the muon neutrino into the tau neutrino, but the reverse process is also true. https://en.m.wikipedia.org/wiki/Neutrino_oscillation When it comes to decay its total energy not just rest energy. For example a proton to proton collision produced the heavier Higgs boson by increasing the inertial mass of the two protons. https://en.m.wikipedia.org/wiki/Higgs_boson Another good example is production of top quarks. "Because top quarks are very massive, large amounts of energy are needed to create one. The only way to achieve such high energies is through high energy collisions. These occur naturally in the Earth's upper atmosphere as cosmic rays collide with particles in the air, or can be created in a particle accelerator." https://en.m.wikipedia.org/wiki/Top_quark In both cases proton to proton collions at extremely high energy states produce particles larger than their invariant (rest mass)
  14. If it helps a good analogy example is shockwaves from an Earth quake. The mechanical force from the epicentre is transmitted outward at the speed of sound through a medium. Variations in the waves speed through the medium vary depending on the type of wave. https://en.m.wikipedia.org/wiki/Seismic_wave same basic physics apply to force through a medium ie rigid rod.
  15. No force propogates at maximum c, if you want good mathematic detail I suggest reading this arxiv paper. Relativistic elasticity of rigid rods and strings http://arxiv.org/abs/1406.0634 It helps to understand the rigid rod if you treat force as being transferred via particle/object to particle/object interactions. Keeping in mind the rod is made up of particles.
  16. I removed the neg point on that post
  17. Your adding unnecessary confusion. If different cars are moving at different velocities, they are in different inertial frames and must be calculated seperately for each car. However all the cars can also be moving at the same velocity. Then they can be included in the same calculation. The formula for length contraction rely on the velocity. Not the acceleration. If you have an accelerating object you can use the same formulas I posted by using the accelating objects instantaneous velocity. Force isn't particularly useful in relativity the amount of force will vary depending on the reference frames [latex]F=\frac{dp}{dt}=\frac{d}{dt}\gamma mv[/latex]. One reason why the force to accelerate an object will vary in different reference frames is due to changes in inertial mass.
  18. Simple folk like I hadn't heard that one before. For one thing Swansort is a professional physicist. Secondly not a single statement you have made this thread has made any sense whatsoever. Length contraction. [latex]L=\frac{L_o}{\gamma (v)}=L_o\sqrt{1-v^2/c^2}[/latex] Those are the length contraction formulas according to GR. Your formulas are nonsense. To put it mildly. GR is extremely well tested. Your formulas are not. The amount of force is already applied in achieving relativistic velocity. Force applies to changes in velocity. Newtons three laws of inertia. An object can already be at a relatistic velocity and have length contraction without additional forces exerted upon it at the time of measurement. Secondly the above equations apply to whatever length of measurement you apply. This talk of tail end/ front end is nonsense. The ship is defined by front to back end. A to B. Even if you decide to devide the ship into individual portions. The same equations above apply to whatever measuring rod you choose to measure. The ratio of measurement/length contraction between whatever you set as L and [latex]L_o[/latex] does not change from the ratio of source to observer defined in the above equations. Deviding the ship into seperate measurement rods DO NOT affect the ratio above Let's put this to math. Define your ship length a to c with b being the centre. Replace L and [latex]L_o[/latex] with a,b,c and [latex]\acute{a}\acute{b}\acute{c}[/latex] respectively. Lets see [latex] a,b=\frac{\acute{a}\acute{b}}{\gamma (v)}[/latex] as the ship is devised in two the same ratio applies to the second measuring rod therefore.. [latex] b,c=\frac{\acute{b}\acute{c}}{\gamma (v)}[/latex] this means that [latex](a,b)+(b,c)=(a,c)[/latex] and respectively [latex](\acute{a},\acute{b})+(\acute{b},\acute{c})=\acute{a},\acute{c}[/latex] This means [latex] a,c=\frac{\acute{a}\acute{c}}{\gamma (v)}[/latex] If you wish to check read. https://en.m.wikipedia.org/wiki/Length_contraction You can devide the ship into however many chunks as you want. The ratio of change on the measuring stick follows the same relations. As the velocity is the same for every portion The problem you seemingly have and this is only a guess, is that you are confusing velocity and acceleration. "A non-inertial reference frame is a frame of reference that is undergoing acceleration with respect to an inertial frame. An accelerometer at rest in a non-inertial frame will in general detect a non-zero acceleration." The above formulas apply to inertial frames. Ie velocity not acceleration.
  19. to expand on Mathematic's response. Particle decay is the spontaneous process of one elementary particle transforming into other elementary particles. During this process, an elementary particle becomes a different particle with less mass and an intermediate particle such as W boson in muon decay.
  20. Lol good catch I'm surprised I, and everyone else missed that. Title error fixed. +1
  21. That doesn't mean we can't determine the age of the universe. You determine the universe age by understanding the universe expansion history.
  22. Aging isn't a good descriptive. Yes neutrinos do decay. Though their mean lifetime varies. http://ned.ipac.caltech.edu/level5/Bowyer/Bowyer6_1.html not sure what your referring to by artifacts of creation. Figuratively speaking everything we see and measure today is a result of the beginning. Albeit in different states.
  23. I don't have too many tensor books however one I enjoyed is Bishop, R. L. and Goldberg Tensor Analysis on Manifolds Sean Carroll has a decent article on GR. " Lecture Notes on General Relativity" http://arxiv.org/abs/gr-qc/9712019 I found it well written, Another online resource being the Feyman lectures. http://www.feynmanlectures.caltech.edu/ You May find "Elements on Astrophysics" handy. It's not a textbook, however it has a huge coverage of numerous metrics used in Cosmology and astrophysics. I use this as a handy look up resource. http://www.ifa.hawaii.edu/~kaiser/lectures/elements.pdf (Lol that should give you a few months of study at least) With your software background, you might want to study N Body codes. I bought the tools and algorithm book sometime back, however never got around to actually developing N Body codes. ( note,The book is rather tricky to follow through) http://www.amazon.in/gp/aw/s//ref=mw_dp_a_s?ie=UTF8&i=stripbooks&k=Sverre+J.+Aarseth Refers primarily to Fortran. Though doesn't have any complete codes Off topic but I highly interesting. Here is a brief simulation of our universe. ( an excellent test of current models.) http://www.cfa.harvard.edu/news/2014-10 http://www.illustris-project.org/ Here is the peer review on the simulation. http://arxiv.org/ftp...5/1405.1418.pdf So this begs the question? Although you admit your model has flaws... does the dark matter distribution reflect on your model compared to the simulation you just saw? The video does an excellent job of approximating observational evidence. This is something any good model eventually needs to do. PS numerous models were tested in that simulation. You might want to Google the Navarro Frenk White profile. https://en.m.wikipedia.org/wiki/Navarro%E2%80%93Frenk%E2%80%93White_profile PS.. it's covered in Elements of astrophysics and no I don't expect your practice model to cover the details in the simulation. However it does show an example of needing to expand upon and incorporate various aspects outside of SR. ( on the textbooks I mentioned, Matt Roose does a good job on filament and large structure formation) It is fun, but you need more than SR for dark matter lol.Up to a challenge, write a FAQ on time. Don't include DM or DE Start it as a new topic, this forum could use a good SR descriptive on time. Some of your descriptives are to the point and accurate. I would be curious to see what you come up with. If your up to it you might want to read. Particularly if you want to cover multiverses in regards to time. "Time before time" http://arxiv.org/pdf/physics/0408111 ( PS overall, albeit a few side points your time descriptives are reasonably accurate. Hence I would like to see you help us out with a FAQ.) Hint... define time as a measure of rate of change or duration Not all change involves momentum.
  24. No problem, I understood that you didn't have the background details in Cosmology applications and I treated your model as a "toy universe". While providing you the tools to increase your knowledge on Cosmology. Little hint, you will find the FLRW metric surprisingly easy to understand compared to GR. Even though The FLRW metric can be derived via the field equations. Out of the numerous textbooks in terms of the FLRW metric, that I've read. Probably the best one specifically covering the FLRW is Barbera Rydens "Introductory to Cosmology" In terms of GR, I like General relativity by Wald. Good intro texts into QM and particle physics are the Introductory books by Griffith. Physical Foundations of Cosmology by Muchanov does one of the better jobs covering nucleosynthesis. Modern Cosmology by Scott Dodelson does a good job on inflation. Introductory to Cosmology by Matt Roose I found good in taking each aspect and simplifying it. I mention the above as outside of formal training the best way to learn is to invest in the right textbooks. If you can't afford textbooks, I always liked dissertations and pedagonal review papers ( lol I'm a bit of a physics textbook collector. I never have enough) Forgot to add Quarks and Leptons is also excellent for modern day particle physics intro, including the Higgs field. As far as inflation goes I've learned a ton in discussions with Brian Powell.
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