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Mordred

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Everything posted by Mordred

  1. Ok well the first question you have to ask is what property is invariant of a vector? In other words what property will remain the same regardless of coordinate rotation or point of origin? Remember vectors has two components magnitude and direction. No I am not going to simply apply your example above. Instead I'll help guide you to the above. This question alone should provide a clue, In regards to your example above. In particular you've chosen a coordinate system. Yet ignore the arbitrary choices involved. Which does not describe the purpose and functionality of a tensor.
  2. The last post gives you some of the tools on tensor conversion. Look through the link.
  3. Yes but that's not the same as stating an object travels (which implies momentum).
  4. So time doesn't pass for an object at rest? At rest meaning no momentum. How do you accurately describe an object at rest as travelling through time? It is the time coordinate that changes, yet the object doesn't move.
  5. Well it all boils down to coordinate and metric choice. Take for example a straight line in two coordinate systems In Cartesian coordinates its easy to visualize a straight line. However in polar coordinates this isn't so easy. A good example being the path of a photon following a null geodesic. To answer how a direction is determined you must first understand the coordinate system in use as well as the coordinate position. For example describing direction in 4d with components ct,x,y,z isn't as straightforward as simply describing a direction using just spatial components x,y,z. Either way there is no hard and fast choice of coordinate system, nor axis. The choice is made in the chosen reference point/frame and coordinate system your using. Direction must have a comparison factor. It is never the same for all observers performing the measurement. No two observers will measure the same direction unless they use the same reference point and coordinate system. For example I can choose to say the vector field is moving in the positive x direction. Then compare object a to that field. However this is a choice. As long as the comparison correctly describes the direction compared to the reference system then it's accurate. I could just as easily state the vector field flows north. Then compare. I don't know how well your math skills are but here is some of the math involved in converting Cartesian to polar coordinates. http://www.brown.edu/Departments/Engineering/Courses/En221/Notes/Polar_Coords/Polar_Coords.htm
  6. Describing an object as travelling in time is a poor choice of wording. As time passes regardless of whether or not the object is moving.
  7. It might help to better understand Studiots post if you look at the four theorems in vector calculus. http://mathinsight.org/fundamental_theorems_vector_calculus_summary The fundamental theorems are: the gradient theorem for line integrals, Green's theorem, Stokes' theorem, and the divergence theorem. The hyperlinks will give a basic intro into each
  8. Why would you need to do the above? Let's take a vector field for example. You don't care which direction the "current" is travelling you only care what direction the stick moves compared to that current. (Let's assume the stick floats) You don't need to have a specific coordinate system. The above can be accurately described in 2d, 3d or 4d coordinates. This is one of the uses of tensors which describes vector and scalar relations independant on a coordinant system. Here is a good example similar enough to your above post. http://www.feynmanlectures.caltech.edu/II_31.html For example the coordinate system you described works well in Euclidean space or Minkowskii (Special relativity). However it is inadequate in curved polar coordinate metric systems such as The Schwartzchild metric. Or for example some of the dimensions in string theory where the coordinate metric is a rotating vector field. (Which is an application of circular vectors Studiot mentioned above) PS a vector isn't restricted to 2d. You can have n dimensions in a vector component.
  9. Ok first off cosmology and universal applications involve the cosmological principle. Which essentially states no preferred direction or location. This is also true for the Einstein field equations. So in these examples direction is compared to a homogeneous and isotropic field from a coordinate. There is however metrics that involve direction compared to a bulk flow, such as direction compared to a current. Either way it doesn't change the fact that direction requires a comparison. That comparison can be a coordinate system such as a vector field, or a scalar field. The example you gave can be modelled as a vector field.
  10. Just for the record. This site does a good job helping those who are asking honest questions. It's often difficult to gauge the skills of the OP when answering those questions. The main problem is many posters with little understanding on the subject matter will make declarations that this is how it is. Those are the posters that get into trouble. Posters that genuinely desire to learn, will ask rather than declare how something works etc.
  11. It is a comparison, in order to define a direction you need a position to refer the direction compared to. It makes no sense in defining direction as a property. For the comparison requirement. When we describe direction of travel you need to have a point of reference. So how can you have direction as an intrinsic property when that direction value can change depending on the reference point? Properties of say for example a particle are intrinsic. Every particle of that type will have the same properties. Ie all electrons will have the same rest mass, spin etc. However the direction varies Perhaps it may help to define how physics defines the word Property. physical property - any property used to characterize matter and energy and their interactions property - a basic or essential attribute shared by all members of a class; "a study of the physical properties of atomic particles" http://www.thefreedictionary.com/physical+property direction is shared by all members of a class example electrons.
  12. Thanks for the catch, gotta love auto corrects. Correction applied.
  13. If your going to use Newtons law then at least show you properly understand it. Mass is resistance to inertia. The statement you made that inertia is resistance to motion makes absolutely no sense. Ether theories have been proved to be incorrect. The rest of your post is too garbled to decipher
  14. You definitely have numerous misconceptions on Einstein vs SR. He didn't throw out SR. SR is perfectly valid in Euclidean space. It's been incorporated into GR, and is an essential aspect within GR which is designed to handle curvature.
  15. The latter part is describing null geodesics which apply to photons. Photons don't interact with gravity. Look at the interactions list on the wiki page I posted earlier. Massless particles aren't dragged per se. Geodesic relations can be tricky when verbally describing them. For example wiki describes it as "Certain types of world lines are called geodesics of the spacetime straight lines in the case of Minkowski space and their closest equivalent in the curved spacetime of general relativity." That description applies to geodesics in general. There being three main types. https://en.m.wikipedia.org/wiki/Spacetime#Spacetime_intervals_in_flat_space PS another thing to keep in mind is often verbal descriptions can be misleading and can vary upon coordinate systems being described. An excellent article describing numerous artifacts of coordinates is the lecture notes by Mathius Blau. http://www.blau.itp.unibe.ch/newlecturesGR.pdf "Lecture Notes on General Relativity" Matthias Blau This last link is roughly 900 pages, but details numerous coordinates. In many ways it's near a textbook in style.
  16. A handy statement was made in this Master-Geodesic article. Geometry=energy. http://www.google.ca/url?q=http://www.physics.usyd.edu.au/~luke/research/masters-geodesics.pdf&sa=U&ved=0ahUKEwjJkf3tuNHMAhVB52MKHVpUAtwQFggRMAA&sig2=FXfhVBHku5zK1fjW-tkXWw&usg=AFQjCNEr4WEHhcvoL-LVhqBLVIcgBRFdkQ Its an excellent article but takes a bit to understand the math behind it. An old relativity perspective is the "River model of blackholes". This particular article provides me numerous clues when I was first studying relativity. http://www.google.ca/url?q=http://arxiv.org/pdf/gr-qc/0411060&sa=U&ved=0ahUKEwiz1KubvNHMAhUD4WMKHXNRD0MQFggZMAI&sig2=KMwrVt094ZmEpor3wKz94w&usg=AFQjCNFI8GTbcqya0j0qAbhzraDu9VmS6w Here is the River model of space. http://www.google.ca/url?q=https://arxiv.org/pdf/1204.0419&sa=U&ved=0ahUKEwiR0Iaxv9HMAhUT42MKHYPbBg0QFggRMAA&sig2=U3lt-9TLseeVW-NNxLJLZA&usg=AFQjCNE5KQpW-SbSZ4Sqg_jkHLGfemxynQ Keep in mind these papers are helpful but do not imply an eather
  17. The diagonal term is detailed somewhat in equation 5.4. I have a better breakdown in one of my textbooks Sort of the weak force is mediated byThe w+,w- and z bosons. Those bosons interact with the Higgs field which has four components. [latex] \phi_1,\phi_2,\phi_3,\phi_4[/latex] The interaction essentially uses up the last three components leaving the first. This results in the non zero Higgs field Now look at the interactions of Say a photon compared to a neutrino. https://en.m.wikipedia.org/wiki/Photon keep in mind the photon mediates the electromagnetic field but does not have a charge. (No binding energy) or doesn't couple to the electromagnetic field. Neutrinos interact with the weak force via the weak gauge bosons. So indirectly they gain mass via the Higgs field but in an indirect manner. The majority of the mass of objects is electromagnetic mass. Ie your table. The strong force loses strength as a function of radius extremely quickly so it's influence is limitted to within composite particles. Ie protons and neutrons. Inertial mass is essentially energy gained due to inertia which also correlates to a mass gain. So when your calculate say the mass of a proton, what your calculating is how strong the particle couples to its interaction field. For a proton 1% roughly is the Higgs field the other 99% is its coupling strength to the strong force. Now if gravity is a force then the mediator boson would be the graviton. However gravity may very well be just the result of curvature relations. We still don't know for sure as we can't fully quantize gravity at the particle level. It's influence one particle to another is too weak
  18. Keep in mind I posted a single field example above. When it comes to mass you must involve all fields and their coupling constants that are present. For example you can have electromagnetic mass or mass due to the strong force interaction. The stress energy tensor is the term that describes the energy and momentum relations in the EFE. Tensors take some considerable time to learn. Each position has its own unique derivative. Which will depend on what that is being related to ie the curvature tensor. I'll dig up some examples once I unpack my textbooks( just finished moving) However in the meantime this article may help. http://www.google.ca/url?q=http://mathreview.uwaterloo.ca/archive/voli/2/olsthoorn.pdf&sa=U&ved=0ahUKEwjY1ceOqdHMAhVU3WMKHegsCW8QFggUMAE&sig2=cKOZEEemRIw0wylOMc0lYQ&usg=AFQjCNEOA2zinwqJc_O4wdiLvAirH1GfqQ
  19. I don't need to wonder why mass curves spacetime. If you think carefully about my last post the clues are provided. First define mass. Then define what is truly meant by spacetime curvature. (Mathematically) Remember space is just volume, spacetime is simply any metric system that involves volume and time as a coordinate. Then look at the diagonal terms under the stress tensor. (rho,p,p,p) [latex]T_{\mu\nu}=\begin{pmatrix}-\rho&0&0&0\\0&p&0&0\\0&0&p&0\\0&0&0&p\end{pmatrix}[/latex] You have mass density and various types of pressure relations. So lets use a simplified analogy. Two particles that interact with each other (attraction) has binding energy. That binding energy is related as a resistance to inertia. (Mass) So lets say we have a Higgs field. This field supplies a binding energy to Say just the w+ bosons. The more w+ bosons you have in a unit volume the more mass that volume has. (This applies to all fields, electromagnetic, strong and albeit via the Higgs field the weak force) Now recall that neither mass, nor energy exists on its own. These two terms are properties. In order to measure a property you need to measure a particle or object. Now if you think about binding energy and mass being related, then realize that spacetime metrics is a coordinate system. Time dilation and length contraction becomes easier to understand. For gravity you can use a field of test particles. Each coordinate being the location of a test particle. Then add your mass influence upon that field. Voila the measured amount of influence upon each test particle will have a curved distribution in strength of attraction. As we're using coordinates (ct,x,y,z) this means spacetime is curved due to mass( resistance to Inertia). ( keep in mind the equivalence principle). It might help to also understand that all interactions are usually described by a coordinate system. For example when you measure a frequency we use the x,y coordinates. X being the amplitude, y being the period or wavelength... Spacetime curvature is no difference, we simply add the z, coordinate but as time also varies we need a time coordinate. An analogy I often found useful is to think of a massless field of test particles. As there is no mass there is no resistance to inertia. Everything moves at c... Now add mass via some binding energy you have resistance to inertia so those particles can no longer travel at c. To get to coordinate b from a will take more time. Now given the above this quoted section should make more sense
  20. If cold fusion was a feasible reality it would have been marketed and announced world wide. Plain and simple. You have no idea how many times I've heard these arguments on forums over the past 15 years or so. I've heard nearly every argument on cold fusion, and every argument ends up in pointless bicker and endless skew of links both for and against... If cold fusion is found to be a conclusive reality then you would literally hear it on the News. Plain and simple. If I recall correctly Mossier Boss work was countered by Prof. Paul Padleys. It's been a while but if I recall the problem Padley showed that Boss couldn't provide any believable theoretical explanation of how a fusion process could occur in condensed matter systems under such experimental conditions. However that's off memory as I lost interest in the cold fusion debate years ago. Just a sidenote.. years ago I ran into a professor who claimed to have built a salt water carburetor. He even showed me his patent and manuscript. That was back in 1990, to this day we still use gas primarily. If you wish to believe in cold fusion feel free. My only objection is stating there is conclusive proof or evidence. Which is false.
  21. There hasn't been 20 years of overwhelming proof... there has been 20 years of crackpot/con artist trying to suggest overwhelming proof. Overwhelming proof would have strong support by the scientific community by being readily replicated beyond reasonable doubt. That type of proof would earn a Nobel prize. The most common argument against this is typically conspiracy theory related... Here is a related review http://www.google.ca/url?q=http://lenr-canr.org/acrobat/DOEusdepartme.pdf&sa=U&ved=0ahUKEwiF9PDXotDMAhVC-mMKHQhEC6oQFggRMAA&sig2=w0HGg-YO8dihuCaUTObOow&usg=AFQjCNHohRR7dvRULT2pXO69WsIUJaXT3Q
  22. We don't throw out SR, because in many circumstances it still works out accurately. It is also not possible to understand GR without a firm understanding of SR. Much of your last post is so scattered I can't make any sense of it. It reads like random thoughts thrown together without any effort to apply a logical sequence to your post. Although it is evident that your math skills may be lacking on the relations involved. In particular the choice of coordinate systems.
  23. You would be far more accurate in mass curving spacetime. Matter applies to fermionic particles. When you think in terms of Mass-density and keep in mind the definition of mass. (As resistance to inertia) GR becomes easier to understand. However you also have to throw away pop media visualization aids to spacetime curvature and switch your thinking to a geometric distribution of influence. (Ie variation of strength of influence at a given coordinate) Given the above one can recognize that it is the stress energy/momentum term in the Einstein field equation that tells space how to curve. https://en.m.wikipedia.org/wiki/Stress%E2%80%93energy_tensor
  24. No nothing here is conclusive enough to be considered as conclusive. All the articles mention is the possible viability and details some of the research. Conclusive proof would hit the news in this subject.
  25. While I don't work the biotech industry. Never forget to search the related industries. Myself having my own degrees. I can relate to completion of a strong acedemic level to work correlation. Take some advice, " DON'T ignore the stepping stones to a strong profession.". !!. Look for related channels of related fields that can use your knowledge pertaining to your field.
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