What is Expanding: Definition and 634 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. P

    The Mystery of Expanding Space: Uncovering the Truth Behind Dark Energy

    Why "expanding space"? When the "faster with distance" view was first discovered the natural assumption was that this movement was ballistic. As far as I am aware, this remained the case for most of the rest of the 20th century. Nowadays this movement is said to be due to the expansion of...
  2. H

    Explaining the Expanding Universe: A Discussion

    A common misconception from friends studying outside a Bsc. is the impression that our universe is expanding out in space, that space is infinite and that simply matter traverses into voids. They seem to have a hard time understand that the expanding universe is space itself expanding and that...
  3. E

    Explaining Expanding Universe: Galaxies Moving Away

    Hello, I am trying to understand that in order for the universe to be expanding that galaxies at further distances must be moving away from us at faster speeds than galaxies closer to us. It seems enough that all galaxies are moving away from us (or each other if observed from another galaxy)...
  4. S

    Expanding ArcSin[x+y] into Sin/Cos/ArcSin/ArcCos

    is there a way to expand ArcSin[x+y] into sin cos Arcsin and/or Arccos? it looks like a Tan curve, but then so does Arcsin[x+y]-Tan[x+y] thanks
  5. D

    Spacetime - infinite or expanding?

    Excuse my ignorance on this topic but it's not exactly my main topic of study, just a curiosity that came to mind. As I understand it: Big Bang happened, spewing space-time into existence (and if I remember correctly, according to Dr. Kaku, apparently tearing our 4-space out of 10-space). My...
  6. 8

    Where is the energy coming from to push space apart?

    I was reading http:/arxiv.org/abs/0810.0153 by Yu and Baryshev on expanding space and a question came to mind. The far galaxies are accelerating away from us. The amount of space that’s “created” each day, causing this acceleration, is much more than was needed the day before to cause the...
  7. D

    Universe Expanding: Forces That Speed & Slow It Down

    What allows the universe to expand faster than the speed of light? What force will slow it down, causing it to start contracting on itself?
  8. C

    Space is NOT expanding. Where are the holes in this simplistic view?

    No expansion of space, per se? Sure, all galaxy groups appear to be traveling away from ours. But does that mean the universe is inexplicably expanding, like a loaf of raisin bread, as some have likened it? I think not exactly. I think it is expanding, in that all objects appear to be moving...
  9. S

    Expanding a small oscillation potential in taylor series

    I was wondering if someone could help me with Goldstein's equation 6.3 (3rd Edition). It is the chapter of oscillations and all that he has done in the equation is to expand it in the form of a Taylor series. I can't seem to get how all those ni's come to get there.
  10. 8

    Liveweaver's Paper On Expanding Confusion Is Confusing

    arXiv:astro-ph/0310808v2 paper by Lineweaver dated 13 Nov 2003 entitled "Expanding Confusion: common misconceptions of cosmological horizons and the superluminal expansion of the universe" has a sentence in the second paragraph on page 4 that I find confusing. The sentence is: "However, since...
  11. T

    Is the Universe's Expansion Constant or Accelerating?

    reading thru some of the posts I havn't really found the answer. The universe is expanding but is it a constant rate or is it an accelerating rate?
  12. D

    Expanding universe & relativity

    As we know we see the universe at points in its infancy when the universe was born however for us to be here to see the light we must have either 1) Gone faster than the speed of light and 2) always existed here somehow. Is there a general consensus that space actually expanded faster than...
  13. B

    Could it be possible that gravity is the reason why the universe is expanding?

    Could it be possible that gravity is the reason why the universe is expanding? When stars die and some create gravity waves, those waves are expanding at/around the speed of light. The waves then are traveling faster than a planets'/suns' gravity. Therefore the wave would pull in until it...
  14. C

    Entropy Change of an expanding gas

    Two moles of an ideal gas undergo a reversible isothermal expansion from 1.97×10−2 m^3 to 4.82×10−2 m^3 at a temperature of 20.0 C. What is the change in entropy of the gas? WORKING: Using \DeltaS = nRIn(V2/V1) = 2(8.31*ln(4.82*10^-2/1.97*10^-2) ANS = -138.20 J/K Is this...
  15. R

    Unit of Measurement: Arbitrary or Dependent on Physical Laws?

    Just a thought I literally just came up with sitting here on a Sunday morning after having joined this site about a minute ago (first timer). Reading some of these posts about the expanding universe and thinking about the idea of relative positions, I thought of this angle on things. Now, this...
  16. A

    Expanding Universe: Doubts & Questions

    I have certain doubts about the notions of expanding universe: 1. Are both space and time intervals expanding or only the space interval expanding? According to FRW model, only space is expanding. Is that correct? 2. At what rate is this expansion taking place? When I talk to my friend, I...
  17. R

    Is the Universe Expanding from a Single Point and Can We Observe Its Center?

    Assuming we are not at the center of the universe: If V is the vector from the center of the universe to us, then -V would be the vector from the center of the universe in the direction away from us. Wouldn't a star (or whatever) on the -V vector be accelerating away from us at a larger rate...
  18. U

    MATLAB Expanding a number in matlab and getting rid of e+003 how ?

    [SOLVED] Expanding a number in MATLAB and getting rid of e+003 how ? heres my code: Sysms x f=(my function) Y=int(f,11,16) --> Results in a fraction answer Double(y) --> To get rid of the fraction The answer is 1.6050e+003 how do i let it show 1605 straight away ?
  19. T

    Expanding Exponent Expressions

    Hi, I don know how to go about expanding things such as 3x\sqrt{3x-1} apparently that equals 12x^{2} - 4x i know that 3x\sqrt{3x-1} can be written as 3x(3x-1)^{\frac{1}{2}} but i don't know what to do. I can't remeber. Thanks :)
  20. W

    Why is space expanding and matter including galaxies not shrinking?

    I know it probably looks like a completely stupid question.. But I can't find the answer. Hopefully you all can help me out here. Essentially, all galaxies are moving further apart, from each other.. each spot in the universe is said to have the same effect of everything moving further apart...
  21. N

    Tired light vs. expanding universe

    I was wondering if anybody knows of any experiments that differentiates between tired light and an expanding universe?
  22. W

    Alternative idea on expanding universe

    This may be a little crazy of an idea, and I am posting it just for fun, so don't take it too seriously. What if the universe was not expanding, but instead we along with all other objects are shrinking?
  23. A

    Expanding a function in Gaussian-Hermites

    Expanding a function in "Gaussian-Hermites" This isn't homework or coursework, but seeing as it's most like a homework problem, I figured this would be the best place to ask. Note that I'm using the physics Homework Statement I would like to expand a function (let's take a gaussian for...
  24. A

    What is the force of a shockwave expanding 100 fps in fluid

    I posted a few days ago . . . I think the point of my question has been missed. It was generally about ballistics. I elected not to go into any specifics because this is a physics forum not the FiringLine forum. So, I will specify and simplify . . . Here is my question. If a sphere is...
  25. R

    On Pressure/Gravity/The Expanding Universe

    Now, It is has been derived from GR that the pressure within a substance contributes to it's gravity just as it's mass density does. But I had a thought Suppose you have negative pressure. A simple example I can come up with would be when a solid object is stretched to support a hanging...
  26. K

    Which conserves energy better? Expanding space or Shrinking matter?

    How would we ever tell the difference between a universe that has expanding space and a universe that has shrinking matter? How do we reconcile our beliefs about the conservation of energy with the notion of expanding space? Wouldn't it be easier to account for energy if it involved shrinking...
  27. A

    Is the whole Universe expanding, or just the Observable Universe?

    I know the Observable Universe (OU) is Expanding, and I think this is (by now) beyond dispute. However, there is no evidence at all to show that every part of the Universe is expanding. Perhaps the Universe as a Whole (UAW) is not expanding at all. What if it was contracting? What if...
  28. W

    Red Shift = Expanding Universe?

    Has anyone ever considered the possibility that the perceived Doppler effect of light from distant stars/galaxies is not caused by movement of the emitting bodies, but rather a side effect of light traveling extraordinarily long distances under the week gravitational force of the entire...
  29. V

    Blackholes and expanding universe

    Dear all, i'm very new to cosmology/astronomy branches of physics. i've one simple question. it's known that the universe is expanding and i suppose the measurement was made by Hubble for which he won the nobel prize. but also, i recently learned that there're black holes at the centre of...
  30. Q

    Gravity's Effect on Universe Expansion: Dark Energy?

    Does gravity create a wake in subspace? If so would this wake produce a undetectable energy source or negative pressure in subspace which would indirectly lead to the expansion of all atoms in normal space that sit upon it? If the universe's expansion is accelerating then could this be...
  31. Q

    Calculating Force of Expanding Compressed Gas

    Hello, is it possible to figure out how much force in Newtons is created when a compressed gas expands?
  32. S

    Universe Expansion: Understanding the Speed of Light and Galaxies Far Away

    didn't know where to post this. i recently learned that the universe is expanding and it is doing this symmetrical... and all points are accelerating away depending on their distance in space. ok this is ok but then i thought about it alittle bit... doesn't this imply that a galaxy far enough...
  33. B

    Expanding Universe: Empty Space, Gas Mass & Galactic Expansion

    Empty space contains a surprising amount of matter in the form of gas. I couldn't tell you the number because I can't find it online but it is there. Has anyone thought that the universe might be expanding because this gas in empty space far outnumbers the mass of galaxies and that the gas is...
  34. H

    Exploring Exotic Matter and the Expanding Universe

    Am I right in saying that exotic matter or energy is responsible for the accelerating expansion of the universe? If so, would that mean that it's getting further and further away from us? Could a civilization in the future somehow get their hands on exotic (or dark, or negative) matter...
  35. X

    Entropy Change of an Expanding Gas

    Homework Statement Two moles of an ideal gas undergo a reversible isothermal expansion from 3.34E-2 m^3 to 4.80E-2 m^3 at a temperature of 25.7C What is the change in entropy (ΔS) of the gas? Homework Equations ΔS = Q/T The Attempt at a Solution first I think I need to calculate...
  36. N

    Unraveling the Mystery of the Expanding Universe

    I know it's been proven beyond all doubt that the universe is expanding but one thing is bugging me. Why isn't the Earth (and the other planets for that matter) moving away from the sun due to this expansion? Maybe this is a daft question but I can't think of an answer. Can somebody please explain?
  37. I

    Expanding and Accelerating Space in Layman's Terms

    Expanding and accelerating space in layman’s terms. First, Einstein: You and I buy two really nice watches. They are accurate to within a billionth of a second per year, and will calculate to the trillionth of a second. You and I are standing next to each other as we synchronize our new...
  38. D

    What Does Expanding Universe Mean?

    Hi everyone, just signed up to forum so not too sure of what to expect but can I ask one question that has probably been thrashed to death in the past and it is: Taken that the UV is expanding, what is it expanding into? I was told once that it created space as it expanded but that does not...
  39. N

    What Does It Mean When We Say Empty "Space" is Expanding?

    This was moved from another thread in the relativity forum, as it isn't about relativity - pervect. Hi, I understand your question and your frustration. The problem arises by misinterpreting a mathematical description of reality (General Relativity) by reality itself. The "pure relativists"...
  40. G

    Entropy and expanding universe

    If I remember right, I have on several occasions read that the second law of thermodynamics is a consequence of the very unlikely initial state of the universe, and that it is this "potential" that drives the universe. I would rather give the credit to the fact that the universe can expand...
  41. D

    U think that the univers is realy expanding? think again

    u think that the universe is really expanding?? think again well i readed recently in a physics magazine that the scientist are trying to find if the neutrino has any mass , if it is true then the universe will be contracting and not expanding and the big bang theorie is false.. what is the...
  42. J

    Expanding surface of sphere

    a spherical balloon expands when it is taken from the cold outdoors to the inside of a warm house. if its surface area increases 19.4%, by what percentage does the radius of the balloon change? I've tried this several times but I am not sure how to go about beginning the work
  43. E

    Expanding Wavefunction in Infinite Well: Fourier Analysis

    I have an infinite well from -a to with a particle in its ground. The initial wavefunction is then \psi(x) = u_1^+(x;a) = cos(\pi x/ 2a)/\sqrt{a} for |x| < a. In order to get the wavefunction for this particle when box that is instantaneously expanded to [-b,b] should I apply Fourier...
  44. Robert100

    What is our universe expanding into?

    First, a quick note to explain why this question is being posted in the "Beyond the Standard Model" forum, as opposed to the relativity forum. Many studies of relativity discuss the expansion of our universe, but I haven't seen many which explicitly target the question of what our universe is...
  45. Robert100

    Is energy conserved in an expanding universe?

    "General Relativity teaches us that Space is expanding." Ok, so as we discussed in a previous thread, a literal interpretation of this is nonsense. "Empty space" does not expand. Rather, objects move apart. Fine, but the universe as a whole is expanding, right? (Of course, we have little...
  46. marcus

    Expanding Space: the Root of all Evil?

    thoughtful paper on how to convey an idea with least confusion http://arxiv.org/abs/0707.0380 Expanding Space: the Root of all Evil? Matthew J. Francis, Luke A. Barnes, J. Berian James, Geraint F. Lewis 8 pages, accepted for publication in PASA (Submitted on 3 Jul 2007) "While it remains...
  47. moe darklight

    Doppler effect / expanding universetrouble uniting both concepts?

    doppler effect / expanding universe . trouble uniting both concepts? Ok, I think I understand both; I just don't understand their relationship. As I understand the doppler effect, in short, its cause by the difference in velocity (movement through space). And as I understand the expansion...
  48. P

    Comp Sci Trouble Expanding an Array of pointers in C++

    Homework Statement I am working on a program that reads in names (strings), sorts them, and then later is searchable. The problem I am having is this. When I enter the first 20 elements of the array, everything works fine. When I enter the 21 element (when it goes into the if loop) I get...
  49. C

    Expanding Universe: Cosmologists Observations & Questions

    Hey guys, I've been wondering a lot about this Big Bang Theory, as I think it is terribly constructed. Anyways, I realize that cosmologists have observed that the universe is expanding and even accelerating in it's expansion. However, I don't see how this can be possible with the laws of...
  50. 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...
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