What is Expanding: Definition and 635 Discussions

The expanding Earth or growing Earth hypothesis asserts that the position and relative movement of continents is at least partially due to the volume of Earth increasing. Conversely, geophysical global cooling was the hypothesis that various features could be explained by Earth contracting.
Although it was suggested historically, since the recognition of plate tectonics in the 1970s, scientific consensus has rejected any significant expansion or contraction of Earth.

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  1. J

    Photon wavelength in expanding universe

    Let us say we have a universe permeated with a monochromatic photon gas of wavelength L0 at time t0 and the universe is expanding (say for simplicity with a constant rate H, Hubble's Constant). If I sit there and measure the wavelength of the photons as a function of time, what does it look...
  2. E

    Why the universe is expanding faster and faster

    it seems the big bang can't explain it
  3. C

    An expanding universe, part of a bigger leading edge?

    The mathematics passes me by, so please be patient. I have an idea that may have been posited before, but I've not seen it. Could it be that the expansion of the universe as we see it is only a relatively minescule fraction of the whole expansion? I have a mental image of the gaseous...
  4. wolram

    Cosmography: Measuring Universe Expansion via Supernova Data

    http://arxiv.org/abs/gr-qc/0703122 Cosmography: Extracting the Hubble series from the supernova data Authors: Celine Cattoen (Victoria University of Wellington), Matt Visser (Victoria University of Wellington) Comments: 38 pages, 6 figures, 7 tables, uses iopart.cls We perform a number...
  5. C

    The universe may not be expanding

    Greetings all! This is my first time at this forum. Any old pals here from our ruined playpen, pmb, kieth, bruce, sam, hector, nudnik, etc.? It has occurred to me that the universe may not be expanding! Perhaps the "clock" for the universe speeds up as time moves forward. This may be why...
  6. C

    How do we really know the universe is expanding?

    I know about the blue shift of all the galaxies that we see, but does that really prove that galaxies are expanding, or just that something in the intergalactic space is causing a blue shift in the light from distant galaxies to ours? Thanks, and I hope this is the correct forum!
  7. T

    The Expanding Universe: Why Stretching is the Only Explanation

    I recently read in my "10th grade" physics textbook that the universes is constantly streaching making solarsystems farther apart, yet for some weird reason all objects still stay intact. This explination included ireverence for such fundimental concepts as the cartisian coordinate system. I...
  8. P

    Expanding (cosx)^-1/2: Simplifying with Binomial Expansion

    I have the series (cosx)^-1/2 (so it's square-rooted and on the bottom) And I need to get the first few terms. My idea has been to do this: [1 + (cosx - 1)]^-1/2 But I have no idea how to take the binomial expansion of that. Do I: Take the BE first, substituting "cosx - 1" as just X...
  9. K

    Expanding f(x,y) with Double Taylor Series

    Let be an analytic function f(x,y) so we want to take its Taylor series, my question is if we can do this: -First we expand f(x,y) on powers of y considering x a constant so: f(x,y)= \sum_{n=0}^{\infty}a_{n} (x)y^{n} and then we expand a(n,x) for every n into powers of x so we have...
  10. T

    Work done by expanding gas in a gun on a bullet

    A 135 g bullet is fired from a rifle having a barrel 0.590 m long. Assuming the origin is placed where the bullet begins to move, the force (in Newtons) exerted by the expanding gas on the bullet is 20000 + 8000x - 22000x2, where x is in meters. (a) Determine the work done by the gas on the...
  11. P

    Expanding Universe (an interestin mind experiment)

    Try thinking about measuring the expansion of the universe based on relativity. That is to say that depending on where you are located in the universe you might measure expansion or you might measure contraction! Think about this. The observer is placed anywhere inside of a giant ball of...
  12. W

    Red Shifts and the expanding universe

    I have a question about the light observed from galaxies that are moving away from us due to the expansion of the universe. I understand that we can tell they are moving away because the light from these galaxies is red shifted. I was wondering how this red shift is generated, exactly. Is the...
  13. G

    Is the time dimension expanding?

    A thought has been bother me for a while. Is the universe expanding in the time dimension? Let me explain. The future does not exist yet, the future is a concept, an artifact of the human mind. The past (from the time perspective) don't exist anymore, yet we can see the evidence of its passage...
  14. I

    Black holes & expanding universe

    Hello everyone. I'm a beginner with questions :rolleyes: Can someone tell me what happens with black holes in an expanding universe? If the fabric of the universe is expanding wouldn't this result into weaker interactions inside the black hole up to the point when the black hole cannot hold...
  15. A

    Expanding universe and Conservation of energy.

    It is accepted that the universe is expanding yes? and it is also expanding at a slower rate than the speed of light. therefore what happens when light hits "the edge of the universe"? where does this energy go? and i know that the universe is "everything" but if the universe is 'expanding' then...
  16. O

    Black holes and the expanding universe

    In another thread 'Entropy, information and Omphalos cosmology' I commented on a strange fact (which I think many are aware of): namely that to which there was an interesting reply: This subject seems to me not to have an immediate bearing on questions of entropy (or Omphalos cosmology...
  17. M

    Objects faster than light because space is expanding

    I have seen the argument many times that objects can travel faster than the speed of light because space is expanding. Now, what I understand from SR and GR is that no object with mass can travel at or above the speed of light. So how can this be? Moderator: feel free to move this to...
  18. A

    Why is my computer not moving away from me in an expanding universe?

    Hi Im new here so please be kind :smile: . I just wondered, since we live in an "expanding" universe, why is my computer not moving away from me as i type this message? Light from most of the stars/galaxies in the sky is redshifted so they are moving away from me (or so I am told), why not...
  19. T

    Gravity in the expanding universe.

    If the universe is isotropic and the gravitational properties, which we observe in small objects such as planets, stars and even neutron stars and black holes, apply to large objects such as galaxies and even the universe as a whole. Can we then assume that as the universe is expanding it is...
  20. H

    Expanding Universe: Metaphysics & Consciousness

    Hi! Do you know how theories in Metaphysics explain the expanding and accelerating universe? Intuitively i think of expanding consciousness but then what is consciousness? The "thing" that i observe my own thoughts with? :smile:
  21. A

    Could the expansion of space impact the distance between the Earth and the sun?

    I have 2 questions: 1. Since space is expanding, shouldn't the distance between the Earth and the sun be getting greater? And shouldn't that affect the orbit of the Earth (greater distance between the Earth and sun ->> less gravitational attraction)? 2. Is it possible that the speed of...
  22. S

    Exploring the Expanding Universe: Understanding the Concept of Space Expansion

    I want to start with a question that is universe is really expanding? According to my view it is to be like this: (To get this one should be well versed in Doppler’s effect) Suppose we had gone to Mars & placed a light source there & came back. Now we...
  23. U

    How do they know the universe is expanding

    How do they know the universe is expanding when all the evidence pointing to that fact is millions or even billions of years old.
  24. V

    Are explosions soley the result of expanding gas?

    It's being said that the explosive property of nitrogen-containing compounds comes mainly not from release of heat, but from the fact that a few molecules of solids convert to many molecules of gas. And molecules of gas tends occupy so much more space than the solid. What I'm wonder about is...
  25. U

    How Do You Correctly Expand Trigonometric Equations Involving Sine and ArcTan?

    hello.. I've been having some trouble with expanding this: (B^2+C^2)^(1/2) X sin (omega*t +(taninverse B/C) (read as: square root of (b squared plus c squared) times sin times the quantity omega times t plus taninverse of B divided by C) apparently, the answer is supposed to be B cos...
  26. D

    How Does Work Done Compare in Isothermal and Adiabatic Expansion of Gases?

    I've been trying to tackle the following problem, but I can't seem to get it right. An ideal monatomic gas expands quasi-statically to twice its volume. If the process is isothermal, the work done by the gas is W_i. If the process is adiabatic, the work doen by the gas is W_a. Show that 0 <...
  27. S

    How to Expand Log(a+b) for Best Fit Analysis?

    anyoen know how to expand this? i can't think of any obvious way...
  28. L

    Exploring the Impact of Expanding Universe on Particle Attraction

    the universe is expanding. The space between particles of an object is also expanding. So will the force of expanding eventually break the attractive force between particles? stupid question.. help me please anyway thanks
  29. S

    Is the universe still expanding?

    When the HST looks out into the far off regions of space, the data it receives (the light from distant galaxies etc.), has been traveling for millions of light years. When this data shows red shift, and therefore that the source of the light is moving away from us, does this mean that at the...
  30. T

    Shrinking and Expanding Space?

    Where can I find information on shrinking and expanding space as a form of travel?
  31. quantumdude

    Logic, Metaphysics, and the Idea of an Expanding Universe

    This thread is an offshoot of https://www.physicsforums.com/showthread.php?t=83978&page=1&pp=20. Hmmmm, OK... ex·pand v. intr. 1. To become greater in size, volume, quantity, or scope: Air expands when heated. This critic's influence is expanding. 2. To speak or write at length or...
  32. A

    Solving Low T, High B Behavior of (deltaE)^2 = C*[sinh(a*B)]^-2

    I'm studying for the qualifying exam and I came across a problem that I'd be able to do in a snap if I had a computer running mathematica in front of me, but regretably I am having trouble with using good old paper and pencil and a reasonable amount of time. I want to look at the low and high...
  33. U

    Expanding Universe + Rotation - Lost it somewhere

    I am quite confused... I'll state that up front to make it simple. ^_^ Here is my question, though: Assuming that the universe at some point started from a singularity, err... or even that, assuming that the universe is expanding at a rate that has varied over time... I assume that it's...
  34. G

    Exploring 12 Dimensions of Local Universe with Leibniz's Monadology

    i have a strange idea dimensions are a sort of address to define something as distinct from anyother thing in the local universe you must arbitrarily assign some start point then say so far forward or backward so far left or right and so far up or down but then you have to say at five...
  35. wolram

    Entanglement in expanding spacetime

    http://arxiv.org/PS_cache/quant-ph/pdf/0506/0506113.pdf Title: Entanglement in an expanding spacetime Authors: J. L. Ball (Oxford U.), I. Fuentes-Schuller (Oxford U. and Perimeter Inst.), F. P. Schuller (Perimeter Inst.) Comments: I. F-S published previously under Fuentes-Guridi We show...
  36. ?

    The universe is expanding & the universe is infinite

    "The universe is expanding" & "the universe is infinite" can someone explain how these two statements fit together? They seem to be in contradiction to me.. How can you expand upon something infinite?
  37. Adrian Baker

    Expanding universe expanding atoms

    I'm trying hard to find a decent explanation for someone that an expanding universe doesn't mean that galaxies get stretched out and made bigger; that the planets won't get further away from the sun; that we don't grow bigger etc. I've googled and searched about but a decent explanation of...
  38. V

    Nothing expanding into nothing.

    From what I've heard, the university consists of nothing, except for the planets, stars, and the stars "output". (And of course also some other smaller objects). If universe consists of nothing, how would it then expand. How would nothing, expand into nothing? If the outside of the...
  39. Z

    The thread thread: Strangeness of the expanding space paradigm

    Let a floating thread span the distance between two galaxies fast receding from each other due to space expanding between them. Eventually the thread must break. Expanding space forces apart adjacent particles of the thread all along the thread. The thread breaks at an arbitrary spot. Then any...
  40. T

    Question regarding the expanding universe

    When Big Bang occurred everything was thrown in different directions at high speeds. Is this speed constant or are the speed at which galaxies travel slowing down? Since the general theory seems to be that Big Bang is a neverending procedure, galaxies should be slowed down by the gravity of...
  41. S

    Expanding Metals: Copper & Aluminum Equilibrium Temperature

    A 38.0 g copper ring has a diameter of 2.54000 cm at its temperature of 0°C. An aluminum sphere has a diameter of 2.54508 cm at its temperature of 108°C. The sphere is placed on top of the ring as in the figure, and the two are allowed to come to thermal equilibrium, with no heat lost to the...
  42. A

    What is the final temperature of the expanding monatomic gas?

    We start with 5.00 moles of an ideal monatomic gas with an initial temperature of 127C. The gas expands and, in the process, absorbs an amount of heat equal to 1220 J and does an amount of work equal to 2180 J. I fouind out the change in U, which is -960. I'm just not sure how to calculate...
  43. K

    Kinetic energy of expanding ice

    Where does the Kinetic energy of the expansion of freezing ice come from? For example, say you had a gram of water inside a piston. The water freezes and the expansion of ice pushes the piston up. Since the heat of fusion of water is 80 calories per gram, let's say to initally melt that ice to...
  44. I

    My Body Expanding? A Frightening Thought

    I'm possibly being a little naive here, but if the universe and everything in it is expanding, does that mean that all the particles in my body are expanding (if perhaps at a negligible rate)? Quite petrifying... :bugeye:
  45. C

    Proving the Expansion of the Universe

    Before asking a qusetion let me put first the statement of big bang cosmolgy: "These are not galaxies which are going away from us in a fixed space, this is the space between galaxies which is opening up or stretching." Now my question is: In both the cases (either space stretch or galaxies...
  46. S

    Understanding the Expansion of Space: A Scientific Perspective

    This brought me to the question: How can space expand? Does it mean that i can push off the vacuum? Is space some kind of aether of energetic particles? Do we really know what gravity is (i mean except the curvature of spacetime by mass-energy)? If space has a finite shape but is unbound then...
  47. O

    Subsonic diffuser is an expanding pipe

    Anyhow books says Subsonic diffuser is an expanding pipe. In a picture it shows A -> B the radius of pipie decreases. I was under the impression that subsonic and expanding pipe meant radius getting larger. please clarify .. thanks again
  48. O

    Expanding Universe: Is everything really getting bigger?

    First let me thank you for allowing me to attend your forum. Two queries actually, but I'll begin with this one. Once again I saw a graphic depiction of the expanding universe in a news article. The usual one of course, the expanding balloon with the galaxies tattooed upon it's surface. One...
  49. S

    Expanding Power Series: (1- $\frac{2n}{(n+1)^2})^2$

    can someone tell mehow to expand (1 - \frac{2n}{(n+1)^2})^2 into power series or at least direct me to the formula!
  50. J

    Conservation Principle Related to Expanding Space?

    Could someone comment on this: Since space has been expanding since the Big Bang, does this mean there is a conservation principle such that some other property of the universe must be declining? If so, what is that principle and what would be declining? Thanks.
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