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. S

    Local Reference Frame: Explaining What It Is?

    According to this, if someone spins around at 2 revs per second when the moon is in the horizon, the moon seems to move at 4 times the speed of light. And this implies the moon is not in our local reference frame. And per this, local inertial frame applies to "small regions of a gravitational...
  2. M

    Reference Electrode: Choosing & Principal Mechanism

    How to choose an adequate reference electrode and what is the principal mechanism?
  3. C

    Different gravitational fields from different reference points

    Hello. I am new to the idea of Special Relativity. From what I have read, based on what speed something is traveling it experiences an increase in mass. Let's say I am standing on the earth. I am experiencing a gravitational force of (me(m))/r^2. Now let's say I am the same person that somehow...
  4. H

    Relativistic Rocket: Find Δv in Earth Frame

    Homework Statement I a little lost on how to use the relativistic velocity addition formula to determine the increase in speed "v" over a short time interval in the Earths frame of reference, for a rocket having left Earth at rest and traveling through space accelerating at constant acc. of...
  5. K

    Find a reference frame where momenta of electron and proton are equal

    Homework Statement The electron is traveling at a speed of β=.9999999, γ=1957, with mass mc^2=.51099 MeV. The Proton is traveling at a speed of β=.9, γ=2.29, with mass mc^2=938.27 MeV. They are heading in opposite directions, directly towards each other on the x-axis Find the reference...
  6. M

    Problems with Inertial Reference Frames

    The initial presentation of Newton’s Laws of Motion (NLM) to students often proceeds as follow: 1. The 3 laws are presented, 2. The caveat that the laws are only valid in Inertial Reference Frames (IRFs) is (sheepishly) mentioned, 3. An attempt is made to define an IRF, and 4. Some examples...
  7. R

    Reference frame for harmonic motion.

    If you a mass being accelerated by a force which is acting upon a spring attached to the mass it will exhibit harmonic motion. However unlike a fixed harmonic oscillator there is no explicit solution to the equation which describes the motion of the mass in a reference frame outside of the...
  8. J

    Light in local reference frames in extreme gravitational fields.

    As I understand in SR light is always c in it's local reference frame regardless of a present gravitational field. Light would appear to be traveling slightly less than c in a gravitational field otherwise known as the Sharpio Delay in all non-local reference frames. Now, light must be traveling...
  9. B

    Reference in the origin of species

    reference in "the origin of species" I've been reading Darwin's "The Origin of Species". It turns out the benefit isn't so much seeing a familiar theory in original form, although there is a fascination in seeing evolution described without knowing Mendellian inheritance. The best benefit is...
  10. K

    Conceptual Question about reference frames

    Homework Statement Do objects same kinetic energy in all inertial reference frames? For objects interacting, is energy conserved in all inertial reference frames? Homework Equations None The Attempt at a Solution I think the answers are No for the first one, and Yes for the...
  11. H

    Determine the velocity of a reference frame S

    Can someone give me a clue/hint to finish this question? "In a reference frame S, the electric and magnetic fields of an electromagnetic wave E and B are perpendicular to each other. Determine the velocity of a reference frame S' in which (a) E' = 0 and (b) B' = 0"
  12. Saladsamurai

    C/C++ Pass by Reference Function Build Error

    Hello all :smile: I am trying to sort out how to use pass by reference properly and I am getting a Build error related to my pass by reference function. Perhaps someone could help me out here. I thought I was doing this correctly by reading my text, but apparently not. Maybe someone can...
  13. J

    KE of system / different reference frames question

    I am re-posting this question here in a new thread as Humber mistakenly posted it in a two year old thread.
  14. N

    Existence according to reference frames

    Is it possible for a particle to exist according to one reference frame and simultaneously not exist according to another? If energy is relative, can a collision between two particles have enough energy to produce new particles according to its own reference frame but not have said amount of...
  15. @

    This question is not about a moving clock, but about the frame of reference.

    I found out that Proxima Centauri is 4.2 light years away from earth. If someone was on a voyage to this star via space ship, would this person measure the time to be shorter than 4.2 years if their spaceship was traveling 99.99999 percent the speed of light, assuming that the 4.2 years is...
  16. G

    A question about stationary reference frame

    Is this correct? There are two clocks on Earth that are synchronized. One clock goes out on a spaceship at .8c. Now according to the stationary or Earth FOR one year goes by for its clock but he sees that only .6 of a year has gone by on the clock of the spaceship. Now the spaceship...
  17. T

    Difference Between Inertial & Non-Inertial Frames | Practice Numericals

    i came over the terms 'inertial' and 'non-inertial' frames during the study of rotational motion...pls clarify the difference...! plus can anyone give me a link from where i can practice numericals of angular momentum, moment of inertia, torque..
  18. S

    Velocity of a photon from its own reference frame

    So what will it see it self as?? At rest or moving a velocity c? Either way it seems to be a contradiction, so does that mean a photon can't be reference frame?
  19. U

    Observation from Single reference frame and STR

    Last thread that I initiated was titled `Simultaneity is directional while Time Dilation is not', which presented a scenario for the Non-directional property of Time Dilation in STR. Which I think, needs to be reconsidered. And I believe this is the reason why `STR can only be worked out when we...
  20. C

    Discussion of Inertial Frames of Reference

    Post any thoughts or ideas here.
  21. S

    The speed of light, the term light year , and reference frames.

    The speed of light, the term "light year", and reference frames. Hi everyone. This is my first post, and I post out of desperation. A friend of mine and I were casually discussing Time Dilation, interstellar travel, etc. when we came to a point we fundamentally disagreed upon. Neither of us...
  22. G

    Motion in a Rotating Reference Frame

    Homework Statement A particle moves in a rotating reference frame along the x-axis as x(t) = xo eat (xo and a are positive constants). The frame rotates with a time-dependant angular frequency ω(t) about the x-axis. The true physical force is in the x-direction of the rotating frame. Break up...
  23. K

    What is the reference frame the earth rotates relative to?

    Please excuse my ignorance - I am a biologist by training - but this is one of those questions that just keeps bothering me and I can't find the answer with Google/Wikipedia. Take as our example the ocean currents on the Earth caused by the Coriolis Effect of the Earth turning. When I read up...
  24. C

    Travel faster than speed of light. According to what reference frame?

    I have been reading Einsteins Relativity and a simple concept in special relativity is tripping me up. I have heard that an object can never reach the speed of light. To which observer is this speed limit seen by. I know your answer will be "By all observers" but that is what I don't get...
  25. T

    Inertial reference frames and Newton's Laws of Motion

    The first law of motion says that it takes force to accelerate something. The second law of motion says that F=ma. So now my teacher says that the first law is for inertial reference frames, while the second is for non-inertial reference frames. This really annoys me because I don't...
  26. E

    Simple question about time dilation in accelerated reference frames

    If one wants to calculate the elapsed time from the perspective of an object A moving at velocity, v, for time, t, relative to a stationary object B, all you have to do is calculate: \int_{t_o}^{t_f}\frac{t}{\gamma} Of course, \gamma has no dependence on t because v is constant, so we get...
  27. Y

    Is there any good reference on Riemann Surface and Riemann Theta Function?

    Hi, Currently, I need to read some reference about Integrable System, but I am stuck in Riemann Surface, genus, divisors, and Riemann Theta Functions. This makes me anxious. Is there introduction or pedagogical reference on this topic? I think I can spend some time read it during winter...
  28. D

    Time Dilation - Relative to Light Speed or Reference Point - I'm Confused?

    Hi, I've been listening to a Professor Jim Al-Khalil's scipod on time travel. I think this guy is bloody excellent by the way. http://reader.mac.com/mobile/v1/http%3A%2F%2Fwww.jimal-khalili.com%2Fpodcast%2Fjim.rss Anyway, He said to an observer on the Earth a clock on a...
  29. M

    Frame of Reference: Constant Velocity & Inertiality

    a frame of reference is moving with a constant velocity with respect to a inertial frame of reference,then moving frame will be inertial itself?
  30. W

    What is the Top Reference for Particle and High Energy Physics?

    Hello; I'am asking about the best textbook or refrence in particle & high energy physics ?
  31. E

    Universe Age: Exploring the Reference Frame & Relativity

    The experts say the age of the universe is known with considerable accuracy. What frame of reference are they using and why doesn't it violate the idea of relativity to claim to have a preferred frame?
  32. J

    Torque (changing reference frames and adding)

    Hello there I have 2 questions: 1. Can one change the coordinate system of torque vectors through a homogeneous transformation matrix with both rotation and displacement? 2. What's the procedure to add two torque vectors about different axes? Thanks in advance, João
  33. J

    Are You an Inertial Observer on a Constantly Moving Turntable?

    An inertial frame is one which is not accelerating. i.e if I'm sitting in an accelerating bus or plane I'm not an inertial observer however if I am in a bus or train traveling at a constant velocity i.e zero acceleration then I am an inertial observer. One thing Id like to ask here is that...
  34. Rasalhague

    Momentarily Comoving Reference Frame

    - http://www.physicsinsights.org/glossary.html I'm often unsure whether people are using "frame" to mean a chart, or a basis field of tangent vectors, or a basis for an individual tangent space. Have I got this (more or less) right? (1) A MCRF of a pointlike object is a function that...
  35. P

    Is there really an absolute reference frame?

    Is there really an absolute reference frame?? According to mechanics as we understand today, all reference frames are equally valid in analysing in the universe, whether measurements are taken relative to the earth/sun... However if all reference frames are equal, why can't we take...
  36. E

    Inertial frame of reference of light speed (And beyond)

    Hi All! I found discussions on this here while researching the subject to see if anyone else has attempted to explore the subject. I saw that several people asked questions pertaining to this, but the question was never really answered. It seemed unanswerable. While many discussions of...
  37. I

    Mathematical Notation/Symbol Reference Sheet?

    Hey all! For awhile, I have been looking for a .pdf version of a math notation sheet, similar to these sites: http://www.rapidtables.com/math/symbols/Basic_Math_Symbols.htm http://en.wikipedia.org/wiki/List_of_mathematical_symbols I like the way they have the notation in LaTeX, have a meaning...
  38. A

    Calculating Time Period for Simultaneous Relativity in All Ref Frames

    Homework Statement Challenge: a rather eccentric group of astronomy students wanted to celebrate the impact of the Shoemaker-Levy comet on Jupiter by holding a party of sufficiently long duration that their celebrations were simultaneous with the impact of the comet in all inertial reference...
  39. A

    What Equation Should Be Used for Accelerating Frames in Relativity?

    Homework Statement A frame is accelerating uniformly along the x-axis relative to an inertial frame (x,y,z) with acceleration a.Find the transformation between the frames given that the origins concide at t=0. Homework Equations The lorentz transformations cannot apply here ,but what...
  40. N

    Reference for the Temperature Dependent Speed of Sound in Common Solids

    Hi friends, I need the average speed of sound in some common solids, such as Si, Cu and Al, over temperature ranges from 100K to 500K. After 5 hours of surveying acoustic and physical properties handbooks and googling the web, what I find is almost nothing. Does anybody know a...
  41. N

    Test if 2 transformations produce equivalent relations to a reference

    Hello -- I have some reference object R (e.g. a protein), and I've got two transformations t1 and t2 (e.g. a transformation = quaternion + translation). In my case, t1 and t2 were obtained from symmetry operations. So after applying t1 to R I get object T1, and after applying t2 to R I get...
  42. Y

    Two dimensional collision. Center of mass reference frames?

    Homework Statement [PLAIN]http://online.physics.uiuc.edu/cgi/courses/shell/common/showme.pl?courses/phys211/oldexams/exam2/sp10/fig3.gif A 4.0 kg circular disk slides in the x-direction on a frictionless horizontal surface with a speed of 5.0 m/s. It collides with an identical disk that is...
  43. C

    Engineering Electric circuit with negative reference voltages and diodes

    Hi I am having trouble figuring out what to do with negative reference voltages in my circuit. I attached my problem(Problem 3) and I know that some current will be drawn out of the ground and I think all of the diodes will be on but I am unsure how to approach this problem.
  44. X

    Why Gold is the Reference Element for XPS: XRF & LIBS Alternatives

    Hi, guys! Gold is usually used as reference element to calibrate the detector in XPS due to the charge effect, why is Gold so specific? So what element can be the reference element for XRF and LIBS? Thanks a lot!
  45. C

    Why is light speed constant in all reference frames?

    Hey, this is my first post. I am a biology major so I know pretty much nothing about physics, yet sometimes it interests me way more than chromosomes do. So, given that I know nothing about physics, this is probably going to sound like a stupid question. But I've always wondered how it is...
  46. jegues

    Confusion about the potential reference point

    Homework Statement See figure attached for problem statement, solution provided and my solution. Homework Equations The Attempt at a Solution I'm getting confused about the reference point for the potential. First find the potential at point z with reference at infinity...
  47. B

    Time dilation in a non-inertial reference frame

    Hi! :smile: Need some help here. Can we perceive time dilation and length contraction in a non-inertial reference frame? If we observe a reference frame experiencing acceleration close to c, do we see the same effects as in an inertial reference frame?
  48. R

    Comparing Sidereal & Synodic Reference Frames

    This website has an animation that shows the difference between sidereal reference frames and synodic. http://www.sumanasinc.com/webcontent/animations/content/sidereal.html The motion of the moon is circular about the earth, yet apparently the moon has an apogee length that is 50,000 km...
  49. S

    Noninertial Frames of Reference Question

    Homework Statement A mass of 2 kg lies on a horizontal table that is placed in the back of a truck. The mass is held in position by a string and a force of 6 N acts on it in the -y direction. The truck then accelerates in the +x direction. As a result, an observer in the truck sees that the...
  50. S

    Choice of reference frame in conservation of momentum/energy problems

    Problems related to conservation of momentum/energy can be solved by taking reference frame which is stationary to center of mass or which is stationary to ground/observer. So when to use what frame or which frame is beneficial in which case/type of problems? I m confused !:confused:
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