What is Reference: Definition and 1000 Discussions

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. B

    Is Poincare Symmetry Fundamental to Relativity as Proposed by Einstein?

    I have heard the following oppinion: Whether a reference frame is inertial is completely determined by whether Newton's laws are applicable for particles moving at low (that is, nonrelativistic) speeds in that reference frame. Do you agree with it?
  2. L

    Best Physics Ebooks - Top Recommendations

    can someone recommend some reference books on physics which are available as ebooks?
  3. J

    Gravity anomalies : geoid v reference ellipsoid

    Hi. When reducing the value of measured gravity to produce gravity anomalies, the measured gravity is reduced to it's value on the geoid (conventional interpretation). This is then compared to the value generated by the reference ellipsoid at the ellipsoid surface. I would have thought...
  4. Q

    Good contour integral reference?

    Can anyone recommend a good introduction to contour integrals for someone not taking complex analysis? We are doing these integrals in a physics class and I'm terribly confused. I know that I have to choose contours that "go around" my poles, but I don't understand how to do this (I can't seem...
  5. DocZaius

    According to Alice's frame of reference

    According to Alice's frame of reference, there is a 1kg object moving through space at 1 m/s along the x coordinate. When x = 0 meters, Alice applies 1 Newton of force to the object in the positive x direction. However, Bob simultaneously applies 1 Newton of force in the opposite direction...
  6. K

    Calculation of Velocity in reference to circular motion

    Homework Statement 1. A boy with a mass of 50kg jumps off a 30kg boat, causing the boat to move to the right at 2 m/sec. What did the boy jump with a velocity of? a.-1.2 m/sec b.3.3 m/sec c.1.1 m/sec d.0.2 m/sec e.-3.3 m/sec 2. A 2kg cart moving in a straight line hits a piece of...
  7. K

    Do Moving Reference Frames Affect Event Timing in Special Relativity?

    I picture two reference frames for two different objects moving relative to each other as two coordinate spaces S and S'. My question is, say both spaces start of on top of each other (ie both objects are initially stationary) and then the objects start moving relative to each other, would the...
  8. P

    Inertial Reference Frames in Train Experiments: Correct Statements

    Homework Statement You are conducting an experiment inside a train car that may move horizontally along rail tracks. A load is hung from the ceiling on a string. The load is not swinging, and the string is observed to make a constant angle of with the horizontal. No other forces are acting on...
  9. Q

    Work-Energy Theorem in Inertial Reference Frames

    OK, I'm working on a question regarding IRFs, but I seem to be a little confused. Question: Observer A is on the ground and Observer B in on a train moving with uniform velocity v wrt the ground. Each observes that a particle of mass m, initially at rest wrt the train, is acted upon by a...
  10. B

    Showing momentum will be conserved in moving reference frame

    Homework Statement the question gives me the masses and initial velocities of two balls which collide elastically and asks me to prove that it the momentum will be conserved in both a still reference frame and a moving one. Homework Equations The Attempt at a Solution i know that...
  11. F

    Reference guide for freshman calc. based physics

    i'm not sure if this is the place to ask this, so let me know if I'm in the wrong section. I'm starting a class tomorrow where we're going to be researching how different components of a satellite work. our professor wants us to know what we learned in Electromagnetism and Waves, primarily...
  12. C

    Mechanical Energy and Frames of Reference

    Hello, I've come up with a simple, imaginary situation that bugs me. Could someone help resolve my confusion? Let's say that a spaceship is traveling through space, and two people- observer 1 and observer 2- are watching it. Both observers can monitor the ship's speed and the amount of fuel in...
  13. jtbell

    How two clocks can each run slow in the other's reference frame

    People often have trouble visualizing how time dilation can be "mutual" in special relativity. That is, if you have two clocks moving with respect to each other, in each clock's rest frame the other clock runs slower. The following example illustrates how this can be possible without...
  14. J

    Euler and lagrange frame of reference

    can anybody please clearly explain me the difference between these two frames of reference with few examples. my exames are closing up. please help me.
  15. H

    Understanding Frames of Reference in Relativity

    I'm not going lie I don't know too much about relativity, though I do understand it. I haven't even gone to college yet and from what I've read so far I'm assuming there's much more to know. Anyway, in most of Einsteins thought experiments he speaks about observations in terms of 1 frame of...
  16. N

    Java Java 2 The Complete Reference - Herbert Schildt

    Has anyone here used this book? If you have, how would you rate it. To my surprise many programmers seem to despise Schildt's books. One is usually directed to this page to make the point. I was surprised because I found his beginner's guide on C++ quite easy to read and understand. (And...
  17. C

    Universal Reference point in time

    Can we create a Universal Reference point in time, where I'm defining this as a point in time and space. Imagine an arbitrary reference point, for the sake of illustration let's say Grenich, UK in the Time museum in a display case, on a piece of paper, a single micro dot of ink is marked and...
  18. C

    On the noton of reference frames force and acceleration

    in the definition of inertial frame- a frame in which Newtons law of inertial holds- that a body will continue in its original motion unless impelled to change by a net force my problem is that, how do we know that a force is applied without acceleartion (ie only we conclude there is a force...
  19. S

    Reference for shear modulus vs temperature of glass?

    Homework Statement I'm doing some preliminary research for a potential IB extended essay topic. It involves thermal stresses in fused glass; details aren't that important right now. But I need to find a table, equation, or SOME sort of reference that gives me the relationship between the...
  20. D

    Simple Reference Frame problem

    Problem If you throw a ball with velocity v at a wall, it rebounds with the same speed, v. What happens if you throw it at speed v towards a wall which is traveling towards you at speed w? What is your answer in the limit in which w is much larger than v? Answer Let us work in the frame of...
  21. M

    I need big good reference wiht pucter

    i need big good reference wiht pucter forbiochemistry where can i find it
  22. F

    How can the Second Law of Motion be stated in a non-inertial reference frame?

    [SOLVED] Non-inertial Reference Frames Homework Statement State Newton's Second Law of motion in a non-inertial reference frame. Homework Equations In an inertial frame F=ma If S and S' are two reference frames, the same point is related by r=A(t)r'+b(t) where A is an orthogonal...
  23. putongren

    Newton said that all frame of reference are equally valid

    I'm not sure if either Einstein or Newton said that all frame of reference are equally valid. That from my point of view, the laws of physics is the same from your point of view. All frame reference can be put on an equal footing. I was wondering, can one consider the geocentric view that the...
  24. S

    Electrochemistry: Stability test of reference electrode

    Dear subscribers Re: Stability test of reference electrode One of the important properties of reference electrode is its stability during measurements or potential scan. How one can check its stability in a certain electrochemical system? One of the way is to use internal reference...
  25. C

    Switching between frames of reference

    hey :) So, I'm trying to switch between from one frame of reference to another, for a rotation of a 3d object. First of all, the object is rotated, through 2 perpendicular axis. Now, I need to model that rotation in another set of predefined Euler rotations. In other words, imagine a...
  26. S

    Interstellar space travel and reference frames

    Homework Statement A spacecraft with its astronaut has a total mass at rest of 10^5 kg. The astronaut is to travel to a star 10 light years away at a speed such that she only ages 1 year in her frame of reference a) the quantity 1-v/c where v is her speed with respect to Earth is? b)...
  27. S

    Does the Cosmic Background Radiation Provide an Absolute Frame of Reference?

    According to Einstein, there is no absolute frame of reference; no such thing as 'absolute rest'. But does not the Cosmic Background Radiation provide an absolute frame of reference? An object for which this radiation is totally isotropic is at absolute rest; I gather we move relative to it at...
  28. A

    Many-Worlds of Hugh Everett - a Sci Am reference

    Just a Sci Am reference: http://www.relativitycalculator.com/articles/multiple_universes_hugh_everett/page_98.html
  29. S

    What is Ann's final position in different reference frames?

    Hi, I'm quite new to relativity and I'm just going through some problems from past exam papers to prepare for an upcoming subject. The following question has me a little stumped: Betty is at the origin of her frame of reference. At a certain point in time, this also corresponds to the...
  30. H

    Defining Inertial Reference Frames in General Relativity

    How can you have an inertial reference frame in which a body can remain at rest or move with constant velocity unless you postulate the disappearance of the universe? In the Michelson Morley experiment the Earth is not moving with constant velocity, it is accelerating. So the postulates of...
  31. 2

    Frames of reference question

    Homework Statement A smooth level table is centered on a platform which rotates. - The uniform rotation is at: one revolution in 12 seconds - Two perpendicular lines are drawn through the centre of the table, intersecting a circle of 1.20m radius at points: A', C', B' & D'. - Two men, H'...
  32. R

    Q: Special Relativity: Moving Light w/ Mass & Reference Frames

    I have a very basic question about Special Relativity. I am very limited on my knowledge of physics and math and even more so on SR so please keep that in mind when answering. I have read the basic example many times of two spaceships traveling towards each other with a constant velocity. The...
  33. D

    True/False Help: Index of refraction and Reference Frames

    Which of the following statements are true? 1. The index of refraction is the ratio of the vacuum speed of light to the speed inside the medium. 2. The index of refraction is independent of the wavelength of the light. 3. If a light beam is incident perpendicular to the surface of another...
  34. S

    Questioning Zero Reference and the Expansion of the Universe

    I have a question about zero reference. Let us assume the expansion of the universe is due to the expansion of space-time. The analogy I have heard is sort of an expanding foam to account for the faster expansion of the perimeter. Here is the question, if we assume our Earth reference, within...
  35. gabee

    Velocities in rotating and inertial reference frames

    Can someone help clarify this equation from classical dynamics? It doesn't seem to make sense. Here's my textbook's explanation. A particle has position vector \vec{r} in a non-rotating, inertial reference frame (the 'un-prime' frame). Suppose we want to observe the motion of this object in...
  36. W

    Need reference for 'mass tensor'

    Hi, I'm a grad student in computer engineering and my research involves a fair amount of mechanics (forward/inverse dynamics). I'm working with rigid multibody systems with many DOFs (40 to 50) representing human characters. I've come across this...
  37. R

    Dynamics - frames of reference

    Homework Statement here: http://img144.imageshack.us/img144/7518/26700576ok1.gif Homework Equations The Attempt at a Solution well, I tried to solve the motion equation from the inside table. I think there should be a d'elambertian force to the left, and friction force to the...
  38. P

    Velocity of Raindrops: Car & Earth Reference Frames

    A car travels due east with a speed of 35.0 km/h. Raindrops are falling at a constant speed vertically with respect to the Earth. The traces of the rain on the side windows of the car make an angle of 65.0° with the vertical. Find the velocity of the rain with respect to the following reference...
  39. C

    What are the implications of rotational reference frames?

    It occurred to me that, as far as calculating the position or movement of objects a reference frame can be rotational, see the http://en.wikipedia.org/wiki/Rotating_reference_frame" . So instead of seeing the Earth as orbiting the sun you could say that the Earth is stationary and the rest of...
  40. W

    Is a rotating system considered inertial?

    Hi All, I'm a bit confused about the definition of an internal reference system! I know that a system can be considered inertial if there is no acceleration relative to the background stars. In other words, a system moving at constant velocity. What about the rotation of such a system...
  41. T

    Particle in non-inertial reference frame

    Homework Statement particle moves in a xy plane, force F is actiong on it, proove that there exists a frame rotating with angular velozity w.z in which the equations of motion of this particle will be x''=2wy' y''=2wx' Homework Equations m-mass xy-plane in which object moves F=-kr k=constant...
  42. T

    What are some sources for reference data on POD pressure distribution?

    Dear all, I am working on a thesis right now and looking for the reference data regarding to the pressure distribution on this kind of pod (or similar structure) under the fuselage. Is there any people can give me some hints to find those data? Thanks a lot~...
  43. N

    Understanding Reference Frames: Generality & Abstractions

    I am wondering about the generality of reference frames, and how abstract they can be. Is it possible for a vector in one reference frame to not exist in another frame? Or is there always a relation between two reference frames? Also, are two reference frames like two different sets of...
  44. P

    LaTeX Latex Reference for New Users: Integral Help

    Is there a Latex reference for new users? I was unable to figure out how to post an infinite integral with which I need help. I got the integral sign to post and also the upper boundary but could not get the integrand or lower boundary to appear correctly. thanks
  45. W

    What would the universe look like from the perspective of a photon observer?

    According to Einstein's relativity theories, each observer is afforded a frame of reference which can be considered central and stationary. What would the universe look like to the frame of reference associated with a photon observer. Would all things be moving past the photon at the velocity...
  46. F

    Weight of the whole earth with reference to an apple

    I don't know the answer to this question but it may only require common sense: Let's say an apple on the surface of the Earth weighs 0.25 Kg. Imagine the apple as the little Earth and the whole Earth on top of it. What is the weight of the Earth with reference to that apple? I suspect...
  47. M

    Must measurement of time reference light?

    My question is about time-space. It seems to me that special relativity measures time based on light and derives its conclusion on that base. If my understanding is correct, why should we rely on light to measure two moving clocks? Must we involve light when talking about time? What if light...
  48. P

    Entanglement Effects in Relativistic Reference Frames

    Hello all - New to the forums so let me start by saying hi to everyone. ;) Something has always bugged me about considering entanglement effects as "instantaneous." As we all know from SR, moving observers do not agree on simultaneity between two space-separated events. If we...
  49. K

    Falling body in a non-inertial reference frame

    Homework Statement Consider a body falling from a tower in the northern hemisphere at approx 40 degrees latitude. The body is seen to have a displacement to the east. Explain the origin of this displacement qualitatively from the point of view of a non-inertial observer. What local effect is...
  50. N

    Reference to a peer reviewed paper

    Hello I am new to this forum and I just wanted to post about a paper that I found in Physical Review Letters. It is in Volume 90, number 20, 201102 (2003). It is titled "Traversable Wormholes with Arbitrarily Small Energy Condition Violations", by Matt Visser et al. In this paper, it is...
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