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. F

    Temperature vs Volume in an expanding gas

    Homework Statement The energy of a gas is given by: E = 3/2*NkT-aN2/V, where E, N, k, and a are held constant (or are just constants). Volume V1 with temperature T1 expands adiabatically into V2. Determine T2. Homework Equations All in part 1. The Attempt at a Solution I'm...
  2. K

    Energy conservation in an expanding Universe

    How is energy conserved in an expanding universe? As space expands between, say, stars in a galaxy, don't they gain potential energy in the gravitational field of the galaxy? Which mechanism lessens the total kinetic energy?
  3. S

    Energy Conservation and Expansion of Space: A Thought Experiment

    Here's a thought experiment with a few questions: Space expands, probably at accelerating rate. We can make a thought experiment like this: there's a star surrounded by billions of light-years of empty space (say 4300 Mpc radius, well beyond the size of what we see - it's a thought...
  4. A

    Debunking the Expanding Universe Theory: Examining Observations and Redshifts

    This has been puzzling my mind for a long time. How do we really know the universe is expanding? Based on observation? Redshifts? Observation based conclusions cannot be made IMO. We have observed the universe for a few hundred years and that is way too little to use to predict 13+ billion...
  5. K

    Is the Earth Expanding and What Does It Mean for Continents?

    Would it matter if Earth was expanding as opposed to Pangea and moving continents? Is there even a difference one way or the other as to what 'it' means?
  6. C

    Universe expanding or time speeding up?

    Redshift measurements show the universe is expanding, and the rate of expansion has been accelerating since 5 (is that the correct number?) billion years ago. It occurred to me that instead of space expanding (a concept with a few unresolved problems such as what is dark energy?), the same...
  7. E

    The Conundrum of the Speed of Light and the Expanding Universe

    The Two Concepts The [PLAIN]http://en.wikipedia.org/wiki/Speed_of_light"[/URL], through expansion and inflation, as one of the fundamental aspects of the model. The conundrum is that these two concepts seem to be mutually exclusive. The purpose of this article is to bring this conundrum...
  8. C

    Question about expanding universe VS gravity pull.

    Hello all. I am a newcomer on the forum and no major math or astronomy knower. But I have often thought about this issue I would like to ask about here. From what I understand the Big Bang happened from a singularity expanding outwards (or exploding). As the speed of light is considered a...
  9. G

    How do we know that spacetime is expanding

    What are the facts by which we believe that it's spacetime itself which is expanding since the big bang and not that it's only the matter-energy in the universe which expands in a pre-existing unchanging spacetime canvas?
  10. M

    Time and the relative speed of an Expanding Universe

    I would appreciate assistance in answering the following. Does the existence of time depend on the universe expanding at an accelerated rate?
  11. A

    Is There Any Difference Between A Stretching or Expanding Universe?

    I have been reading Cosmology related topics for about eighteen-months. The other day I was reading from the following website: http://wmap.gsfc.nasa.gov/site/faq.html Under Item 2. is this sentence. "Astronomers see galaxies moving apart from one another: space in the universe is...
  12. T

    Understanding the Expanding Universe: The Role of Energy and Acceleration

    For those of you accepting singularity, When the big bang occurred there was a massive amount of energy exerted. Did this energy exert a positive acceleration on everything, meaning that it will continue to expand forever? Or did it have a negative acceleration, like throwing a ball up in...
  13. cepheid

    Expanding spherical shell of gas

    Homework Statement I'm considering an expanding spherical shell of gas in the thin shell approximation, in which all of the mass can be considered to be at radius R. This shell encloses a bubble that has been blown out (by a supernova or something) and is expanding into the ambient...
  14. S

    Solving Expanding Problem with Iron and Aluminium Cylinders

    I may write a bit rubbish English since it's not my native language but please ask if something sounds wrong or hard to understand. Homework Statement The inner diameter of an iron cylinder is 80,00 mm (millimeter) and the inner diameter of an aluminium cylinder located inside this iron...
  15. S

    Unraveling the Mystery of the Expanding Universe

    What is it expanding into?
  16. Y

    Regardless of an expanding universe

    In our universe, is the shortest distance between two points a straight line or a hyperbolic curve? (I'm debating this with my teacher) Of course you're going to ask me for the definition of a straight line but I don't think I can define that relative to a curved line without getting...
  17. M

    Work done by an expanding gas with no moving boundary

    Hello, I'm trying to find an expression for the work done by a gas that expands adiabatically from one chamber to another through a controlled opening and closing of a valve. The setup is the following. There is spherical bulb divided inside into to chambers. One of the chambers (A)...
  18. L

    Expanding universe or shrinking space(-time)

    Hi all, I was watching some online video lectures from the Quantum to Cosmos festival, where they discussed the expansion of the universe and the problems this brings in physics. Problems like the need of dark matter and what the mysterious force is that accelerates this expansion. I've been...
  19. Z

    Expanding f(z) with Known Moments: m_k

    given the set of moments m_k obtained from the known measure w(x) \int _{-\infty}^{\infty}dx w(x) x^{k} = m_k now if we define the moment generating function f(z)= \sum_{k=0}^{\infty} m_{k}(-1)^{k}z^{k} , which have the integral representation f(z)= \int _{-\infty}^{\infty}...
  20. UseAsDirected

    Expanding universe and light detection

    Sorry if this question has been reproduced elsewhere. If the universe expands greater than the speed of light, c, will a light ray from a distant object never reach us? Lawrence Krauss gave a nice presentation and commented about this, but this has thrown my nose out of sorts because I think...
  21. O

    What is the universe expanding into?

    Hi I understand that the universe is expanding due to hubble's constant and the proof that this can show that the universe is expanding, i just would like to know what physicists suggest the universe is expanding into? Thanks
  22. S

    Related rate expanding rectangle

    Homework Statement The length of a rectangle is increasing at a rate of 8cm/s and its width is increasing at a rate of 3cm/s when the length is 20 cm and the width is 10cm, how fast is the area of the rectangle increasing? Homework Equations V=LW The Attempt at a Solution dL/dt=8...
  23. S

    How fast is the area of the oil spill increasing when the radius is 30 m?

    Homework Statement a) if A is the area of circle with radius r and the circle expands as time passes, find dV/dt in terms of dr/dt b)Suppose oil spills from a ruptured ranker and spreads in a circular pattern. If the radius of the oil spill increases at a constant rate of 1 m/s, how fast is...
  24. R

    Expanding Equations: Simplifying 1/(x√(1-2cosθ/x)) for Higher Order Solutions

    Homework Statement Hello, I'm in the middle of a question and I need to expand 1/(x√(1-2cosθ/x)) in powers 1/x up to order of 1/x^3 Homework Equations The Attempt at a Solution This is my attempt to the more complicated question. To get to the final answer, I need...
  25. R

    Expanding Universe: Galaxies & Matter Explained

    When people say the universe is expanding, do they mean that the galaxies etc are moving farther apart from each other (i wonder how fast o.O)? or does that mean that more matter is being produced somewhere in the universe, causing it to expand...
  26. B

    The expanding universe isn't in our neighborhood

    The 'measurement' of the radial expansion of the moon's orbit is 3.8 cm/yr http://curious.astro.cornell.e...uestion.php?number=124 but that measurement is only slightly more than the Hubble constant (the rate that the universe is expanding) Here is my calculation: Hubble expansion...
  27. S

    Another expanding universe question

    I know there are a lot of these questions, but please bear with me, I couldn't really find these precise scenarios elsewhere. First of all, am I correct in saying that if we took a distant galaxy that was highly redshifted, and had it emitting light pulses to us once every second from its...
  28. A

    How Does an Ideal Gas Sphere Expand in a Vacuum?

    I thought of what seems to be a very classical problem but I can't find a solution for it. At t=0 you have a sphere of radius, R, made up of an ideal gas at a temperature, T, and pressure, P. The sphere is sitting in an infinite vacuum. At t>0 you allow the sphere to expand freely outward...
  29. M

    Is space warped, or is matter expanding?

    Why do physicists say that space is warped in with the presence of mass? Wasn't the whole concept of spatial coordinates supposed to make measuring distance easier? I think it would be easier to say that matter expands outwards in the presence of space. Also, because of the second law of...
  30. M

    Are There Alternative Theories to Explain Redshift and Universal Expansion?

    Are there any alternative theories/explanations of why light from distant galaxies is redshifted by an amount proportional to the distance away from us, other than the popular universal expansion explanation? Maybe some theory about light losing energy when traveling over such large distances...
  31. J

    Redshift of Far Galaxies: What Causes It?

    Hi, I have a question about the redshift caused by the expanding universe. I am not a physicist and reading books and articles about physics is just a hobby so I apology if this is obvious to most of you. I have read somewhere that the light from far away galaxies is redder than light...
  32. J

    The Expanding Universe: Understanding Hubble's Law

    As I understand things, the following are true: The further away in space we observe, the further back in time we are looking The further away in space we look, the faster galaxies are receding from us If these are true, doesn't it indicate that the rate of expansion of the universe...
  33. B

    Is the moon is moving away from us? or is the universe just expanding?

    is the moon is moving away from us?...or is the universe just expanding? The 'measurement' of the radial expansion of the moon's orbit is 3.8 cm/yr http://curious.astro.cornell.e...uestion.php?number=124 but that measurement is only slightly more than the Hubble constant (the rate that...
  34. G

    Universe Expanding: Space or Matter?

    When it is referred that the Universe is expanding/accelerating outward, do they mean to say that space is expanding or that matter is accelerating outward through space?
  35. D

    The Expanding Earth Hypothesis

    Before you leap up and down on my virtual corpse: no I don't give much credence to it For some reason amongst some (a very few) geophysicists and field geologists, a hypothesis that plate tectonics is wrong and that the Earth is expanding in radius has been in vogue (I have no real idea why)...
  36. T

    If space is expanding (moving) then does relativity change?

    Or maybe we can apply relativity to space itself? (I'm just saying that because it's moving although it sounds like it makes no sense)
  37. B

    Universe expanding +c. +c impossible?

    can anybody explain this to joe public?
  38. T

    Is the rate at which the universe expanding increasing?

    I was thinking of an idea in my head about a week ago, but it would need the rate of the expansion of the universe to increase over time (this is different from it just expanding at a constant rate). Today, i was reading about dark matter and it had stated that it might be the reason why the...
  39. camilus

    Universe expanding faster than light

    I read it is possible for the universe to be expanding faster than the speed of light. What would be the implications of this?
  40. J

    Expanding Universe: What Drove Early Universe Expansion

    Why the early universe started expanding
  41. S

    Slowing time or expanding space?

    Anyone familiar with a theory that the universe is not expanding, but that time is accelerating, resulting in an apparent red shift of light emitted under an earlier and slower universal clock?
  42. N

    Misconceptions about expanding space

    Much has been written in the debate about whether the space between galaxies is "really" expanding, or whether on the other hand the motion of galaxies is a kinematic recessional motion through space. The equivalence principle strongly suggests that it is impossible to detect any observational...
  43. ChrisXenon

    Expanding Universe & Red Shift

    We hear that the universe is expanding, and this accounts for red shift as all objecsts are accellerating away from each other. But I have also heard that it is the space itself, of which the universe made, that is expanding - not that things are moving in that space. If so, then the...
  44. C

    Expanding A Taylor series.

    [b]1. Hi, I am new to taylor series expansions and just wondered if somebody could demonstrate how to do the following. Find the Taylor series of the following functions by using the standard Taylor series also find the Radius of convergence in each case. 1.log(x) about x=2...
  45. V

    Expanding Light: Wave's Radius Increase - Why Not Dim?

    here it goes you know how from the origin of a light wave in space i.e a star when the waves of light travel outwards, the radius of that wave increases right? dosen't that mean that the wave loses energy at those infinite points along the wave as the circumference of that wave...
  46. P

    Expanding space versus gravity.

    The first reply in the thread "Why expanding space?", says that it was thought that gravity would slow the rate of expansion. Why? If it is the expansion of space that is moving matter apart, then presumably 'twas ever thus. And if it was able to overcome the gravity of the early universe, when...
  47. Feeble Wonk

    Virtual Particle Density in Expanding Space Time

    Please have pity on a poor ignorant layperson struggling for understanding... and keep in mind that I am mathematically impotent. I am trying to wrap my mind around the concept of expanding space-time with regard to quantum foam. Could someone please explain whether the "density" of quantum...
  48. wolram

    Expanding Space: How Do We View It?

    With this idea that space is expanding every where, i assume that every unit of expanding space has a shape, and must have some limit as to how far it can expand, the shape must be very uniform for all, unless fuzzy edges are allowed, how do people view expanding space?
  49. E

    Doppler effect and expanding universe

    Astronomers believe that the universe is expanding because of the measured doppler effect redshift of light emitted from distant stars in other galaxies, correct? Do they have other reasons for believing that the universe is expanding? The stars in our own galaxy are known to not be traveling...
  50. D

    Expanding universe and solar system

    I wonder how the expansion affected the solar system. Yes, I know that gravitationally bound objects had already "adapted" to the expansion. But it had adapted to the linear expansion - this assumption is valid only when we analyze a limited period of time. But the rate of the expansion...
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