Reference Definition and 1000 Threads

Reference is a relationship between objects in which one object designates, or acts as a means by which to connect to or link to, another object. The first object in this relation is said to refer to the second object. It is called a name for the second object. The second object, the one to which the first object refers, is called the referent of the first object. A name is usually a phrase or expression, or some other symbolic representation. Its referent may be anything – a material object, a person, an event, an activity, or an abstract concept.
References can take on many forms, including: a thought, a sensory perception that is audible (onomatopoeia), visual (text), olfactory, or tactile, emotional state, relationship with other, spacetime coordinate, symbolic or alpha-numeric, a physical object or an energy projection. In some cases, methods are used that intentionally hide the reference from some observers, as in cryptography.References feature in many spheres of human activity and knowledge, and the term adopts shades of meaning particular to the contexts in which it is used. Some of them are described in the sections below.

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  1. mrnike992

    Speed of Light: What Frame of Reference?

    My apologies for the numerous times this has probably been posted, but I wasn't able to find a great answer through the search tool alone. Please correct me on anything I state incorrectly, and direct me to the answer.. My question is, if the speed of light is 299,792,458 m/s, its speed is...
  2. W

    Worship, Reference Points & Time: A Story of an Old Lady

    Last Tuesday ,I came across an old lady[looking a bit disorientated] in the street who asked me "Is today a Sunday ,I need to go to church?" I said to her "Its a Tuesday" This set me thinking about "phases of the moon","364.25 days for Earth to orbit Sun", 52 weeks made up of 7 days etc etc...
  3. M

    Light angles measured in a moving reference frame

    I've managed to get through all of this question without trouble until part d). The full question is given here: I've calculated the "true" angles of Star A and Star B as 71.57 degrees and 45 degrees respectively in Frame S, and the "light" angles should be the same, since the stars are...
  4. T

    ADC/DAC Sample Rate and Reference Voltage

    I am currently working on a circuit design that is featuring both a ADC and DAC. I'll focus my question on the ADC in this thread. I'm trying to figure out what each pin does. Am I correct in assuming that the Vref pin on the an ADC chip is used as the maximum encoded value for a voltage? Say...
  5. T

    Reference Frames: Up and Down a River

    Homework Statement A water spider maintains an average position on the surface of a stream by darting upstream (against the current), then drifting downstream (with the current) to its original position. The current in the stream is 0.408 m/s relative to the shore, and the water spider darts...
  6. B

    Question concerning speed of light in reference frames

    My friend posed a question to me that I was unable to succinctly answer (or answer at all for that matter). So I thought I'd make an account and ask people who know more about this than I do. Ok. So let's assume that Person A starts at Position 1. Person B is at position 2, which is 1 light...
  7. E

    A little confusion on reference frames

    In college physics 1, I think I'm confusing myself on reference frames, and would like for one of you significantly smarter persons to let me know if I'm on the right path with understanding it, and if not, could point me in the right direction :) We're just beginning inertia and momentum in...
  8. N

    How bad is this? Can't get reference letter from top researcher

    Hello, I'm applying for my phd in field X at the moment. Two years ago I did a 2-month research project on X under guidance of one of the leading figures of that field (Prof Y). Now, he is notoriously hard to get a hold of (even his phd students struggle) and he isn't responding to any of my...
  9. putongren

    Introduction to Tensor Calculus, Relativity Homework

    I already have the solutions emailed to me from a D H Lawden textbook. I have trouble understanding the solution as the solution is not formatted properly, and the answer seems to be a little too advanced for me. I hope that some one can help me understand the problem. 1. Homework Statement...
  10. M

    Reference Frames with Different Origins

    Homework Statement Alex is born in a spaceship and Bill is born on Earth just as Alex’s spaceship passes Earth at 0.90c when t=t’=0 (event A). Planet Z is at rest in Bill’s reference frame (x,ct), where it is 45 light-years (ly) away. Alex, whose spaceship is at rest in the frame (x’,ct’)...
  11. M

    Three Reference Frame Relativity Problem - Velocity Addition or Proper Lengths

    Homework Statement Anna and Bob have identical meter sticks. Anna an observer on Earth, sees Bob traveling in a spaceship at 0.5c away from her. Bob leaves his spaceship in an escape pod, moving away from Earth and the spaceship at 0.1c with respect to the spaceship. How long is Bob's meter...
  12. David Carroll

    Does acceleration change according to inertial frame of reference?

    I apologize if this has been discussed before. I am no physicist, I am just trying to see if I am understanding special relativity correctly. Please be advised I am dumb, so be gentle. If a spaceship (sorry for the cliché, but it's a little bit cumbersome to keep using the phrase "inertial...
  13. A

    How long will it take cars to overtake?

    Homework Statement A car starts from rest and accelerates uniformly at 3.0 m/s2. A second car starts from rest 6.0 s later at the same point and accelerates uniformly at 5.0 m/s2. How long does it take the second car to overtake the first car? Homework EquationsThe Attempt at a Solution So let...
  14. Pezz

    Special Relativity - Events and Frames of Reference

    Hello everyone :). I'm new here and wasn't sure where to post my physics question so here I am in the homework help section as my question is homework related... The problem I'm having is of very basic nature however I might have some trouble wording it. I understand an event is something that...
  15. B

    Looking for best reference in statistical physics

    Hi, I am looking for a reference book in statistical physics which comprising any possible aspect of statistical physics. Can anybody help? Thank you
  16. aditya ver.2.0

    Query regarding to the frame of reference

    If a metallic ball is place inside a giant hollow top, and the top starts to rotate. Along with the top, the metallic ball will also start to rotate. Thus my question is the ball motion is under inertial frame of reference or non-inertial ?
  17. aditya ver.2.0

    Query regarding to the state of frame of reference for the ball

    If a metallic ball is place under a giant hollow top, and the top starts to rotate. Along with the top, the metallic ball will also start to rotate. Thus my question is the ball motion is under inertial frame of reference or non-inertial ?
  18. M

    Best book reference for studying quantum physics

    Dear mates: Please recommend me the best book for studying quantum physics. With all the best Marco Uscanga
  19. C

    Basic trig question: reference angles

    Hello, Preparing for a test, I've had to go through some very basic trigonometry and I've got to thinking why reference angles "work". I've gone through my study material and through another trigonometry book I have around the house and references angles are never proven, the theorem is just...
  20. Diploria

    Hafele-Keating with the plane as reference frame?

    Hello, I noticed quite a few questions on the Hafele-Keating experiment here, but I believe none that have my exact question. I understand the explanation given for "a frame of reference at rest with respect to the center of the earth", as in the Wikipedia article. But what happens if...
  21. T

    Ph.D Physics (UK) with a potentially bad reference

    Hey guys, I finished my MSci degree (Physics with Theoretical Physics from the University of Nottingham) back in June achieving an average of 67% over the entire 4 years. My grades in 2nd year were extremely high (78%) and my grades dipped in 3rd and 4th year (though I did get some nice grades...
  22. S

    Need some reference books on machine design

    Dear all, I am following Shigley's Mechanical engineering design as a textbook for my course of machine design.But i would be very thankful if anyone gives me some references books of machine design in pdf format containing more and more problems.It will be helpful also if you can provide any...
  23. Scardino

    What books should I consider as a reference for design engineering?

    I am looking to be a design engineer and I was waning some recommendations on what books are good reference books for this. The two books that I have been able to find are Mark's Calculations For Machine Design and Machine Designers Reference by J. Marrs.If anyone knows anything about these or...
  24. schrodingerscat11

    Recommended Reference Manager Software

    Hello everyone. I like to ask for suggestions for an efficient reference manager software. Hm, here are the characteristics I am looking for. -Has an online counterpart where I can save articles that I want to download someday -Has a tagging system (i.e. I can attach certain keywords to an...
  25. J

    Good reference on multi-variable calculus of variation

    I am looking for a good and easy access reference on multi-variable calculus of variation with many examples and demonstrations. Although I have many books and references on the calculus of variation, most are focused on single-variable. Any advice will be appreciated.
  26. K

    Path Integrals in QFT: Beyond Peskin's Reference

    Can anyone suggest me a good reference for path integrals (QFT), apart from peskin.
  27. F

    Conservation of energy/momentum and difference reference frames

    I managed to confuse myself with a simple thought experiment. I have a spaceship that uses mechanical springs loaded with balls for thrust. We start in a reference frame O where the ship isn't moving and fire one spring, which gives the ship a velocity v. Pick a new frame O', moving at v in...
  28. M

    The Earth: An Inertial Frame of Reference

    How Earth is considered to inertial frame of reference?
  29. D

    Does the Existence of the Axis of Evil Mean a Special Frame of Reference?

    Does the existence of the "Axis of Evil" observed by WMAP and Planck mean that there is a special frame of reference in the universe?
  30. D

    Good reference book for U.S. constitution?

    I'm looking for some kind of reference/guide book for the U.S. constitution. I actually don't know exactly what I'm looking for, but I envision something which contains the full document and all the ammendments, but also information about the people and history behind the document - facts and...
  31. X

    Relativistic speeds within a relativistic frame of reference

    Astronauts on a long space journey are playing golf inside their spaceship, which is traveling away from the Earth with speed 0.6c. One of the astronauts hits a drive exactly along the length of the spaceship (in its direction of travel) at speed 0.1c in the frame of the spaceship. What is the...
  32. S

    Reference Request: Split-Complex Numbers

    What's a good book on split-complex numbers? If it also covers dual numbers or the relation between split-complex numbers and special relativity or Minkowski 4-space or some analysis of split-complex numbers then all the better, but that's just gravy. I really just want a good reference for...
  33. P

    Is Holding an Object Work in Different Frames of Reference?

    If I stand on the surface of the Earth holding an object from my frame of reference I do no work because the object is at rest and the displacement is zero. However from the frame of reference of a second object moving toward the Earth the first object would be moving up and I would be doing...
  34. M

    Velocity of light and it's frame of reference.

    If light has a maximum speed of c, what frame of reference is that speed determined from? For example, if you were to turn on a light bulb moving at a constant rate and measured when the light in every direction got to one light year away from it's source, wouldn't some of it reach that...
  35. B

    Reference point of voltage for an electric field

    When you are told that V is the voltage at a given point in an electric field and voltage is the difference in potential energy between two points/charge, where is the other point supposed to be? Thanks
  36. T

    What is the best book for solving PDEs?

    Hi, I need a book that I can use for reference to solve any Partial Differential Equation imaginable, if it has a solution of course. Can you suggest me any?
  37. N

    How Do You Solve a Rotating Reference Frame Problem in Physics?

    Homework Statement I have attached the problem as a picture on this post, am really really unsure on how to start! so far the only thing i can think of doing is using this equation (\frac{d^{2}r}{dt^{2}})_{s} = ( \frac{d^{2}r}{dt^{2}})_{s'} + 2ω \times (\frac{dr}{dt})_{s'} + \dot{ω}...
  38. anorlunda

    Establishing a Mutual Coordinate System for Interstellar Communication

    I apologize for posting this question on a physics forum because it has a science fiction origin. However, I thought that real astronomers may have a real science answer to the question, so here goes. Imagine two parties from distant parts of the galaxy in communication with each other...
  39. P

    Transformation of acceleration between two reference frames

    hello i want to derive the Transformation of acceleration between two reference frames i searched in internet and found a book but i don't understand just one step i attach a picture so you can see what i found in the internet my problem is eq. (1.10) \begin{align}du=\frac{dU}{\gamma...
  40. Feodalherren

    Relativity - time in different reference frames

    Homework Statement An astronaut is traveling in a space vehicle moving at 0.500c relative to the Earth. The astronaut measures her pulse rate at 75.0 beats per minute. Signals generated by the astronaut’s pulse are radioed to the Earth when the vehicle is moving in a direction perpendicular to...
  41. A

    Calculus Reference Textbook Request

    Hi, Background: I'm a junior self-studying Calculus, and I want to study from a rigorous textbook. I've seen many threads comparing and contrasting the textbooks of Apostol and Spivak. I have access to the online versions of both author's textbooks, but I find it difficult to concentrate...
  42. M

    Inertial Frame of Reference: Why Space Selects a Non-Inertial Frame

    Why does one particular 'frame of reference' have fictitious forces (like inertia) whilst another one doesn't. I understand the basics, but more interested in 'why' space seems to have magically chosen specific frame to be the 'non inertial frame'. Could space be more absolute than we...
  43. W

    Relative motion of two reference frames

    Homework Statement Two clocks located at the origins of the K and K' systems (which have a relative speed v) are synchronized when the origins coincide. After a time t, an observer at the origin of the K system observes the K' clock by means of a telescope. What time does the K' clock...
  44. A

    Fortran Array Reference is out of bounds error? Fortran

    So, I have a bunch of errors which need resolving here but majority are based on the "out of bounds" error and hence the topic title :). Would be great if you are able to help me resolve the errors. Quite a newbie with fortran. So please bear with any silly questions that I may throw at you...
  45. L

    How would you define an inertial frame of reference?

    I've researched about it and watched a few videos, but I can't seem to get my head around it. Would saying that "it's a marker that is fixed relative to your position, in which Newton's first law holds" be an accurate way to define it?
  46. Y

    Spring potential Problem Reference Point

    Hi, I uploaded the problem and the solution's manual answer. There is something wrong in it I think. For this problem: "A 20.0-kg block is connected to a 30.0-kg block by a string that passes over a light frictionless pulley. The 30.0-kg block is connected to a spring that has negligible...
  47. V

    Two bodies problem in other reference system

    Hello, I would like to try to "model" motion of two gravitationally interacting bodies. But from some "separated" point. I can find the trajectory of mass point to orbits around some other mass point from point of view one of them (using binets formula). But in this reference frame I am...
  48. mishima

    Spectrophotometric Reference for Inorganics?

    I am looking for absorbance spectra and extinction coefficients (molar absorptivities) for common inorganic substances like potassium and sodium salts. I am only finding this information for biological substances. Am I misinterpreting what the spectrophotometer can do? I would like to, for...
  49. S

    What is a pseudo-force and how does it relate to non inertial reference frames?

    So I was told that a pseudo-force acts on a body when its's motion is analysed with respect to a non inertial reference frame. I'm a bit confused. Does that mean the reference frame is accelerating with respect to the body, or with respect to the earth? And why does there have to be any sort of...
  50. A

    Reference for Learning About Waves

    I recently looked at the reference in an article I am reading, and subsequently checked "Oscillations and Waves in Linear and Nonlinear Systems" my Rabinovihc and Trubetskov from the local library. https://www.amazon.com/dp/0792304454/?tag=pfamazon01-20 Great book, but unfortunately as a...
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