Read about dark energy | 172 Discussions | Page 1

  1. D

    B The Relationship of Gravity and Dark Energy

    What gravity is, as pointed out by Newton and Einstein, is still a mystery. Adding to that conundrum is dark energy which continues to inflate the cosmos. Both Newton and Einstein, and every one else as far as I am able to discern, assume that gravity works by drawing massive bodies together...
  2. DuckAmuck

    I Universe Expansion

    So the universe is expanding, and galaxies are getting farther apart from one another on average. Does this motion count the same as ordinary motion, in that if a galaxy is being expanded away from us at 0.5c, that clocks in that galaxy would appear to tick slower at 0.866 the rate of clocks here?
  3. Ken Lehn

    B Question concerning dark energy

    Was all dark energy "born" at the moment of the Big Bang? Or does it "spring" into existence continually?
  4. Vamsi9955

    B How can string theory be proved

    The fundamental building blocks of the universe is thought of super strings, if proved can solve the mysteries of the universe but if proved than how? And how can it solve the mysteries of dark energy &dark matter and black holes?
  5. Y

    I What will eventually happen to all EM waves / photons?

    I'm not an expert in this matter, and at best only aware of some superficial facts and a layman's understanding of them. So please forgive me for any ignorant mistakes in my thoughts, and kindly point them out to me. Going by the Lambda-CDM model, the expansion of the Universe will eventually...
  6. R

    A Question About Conservation of Energy, the Cosmological Constant and Dark Energy

    I am confused about the cosmological constant and dark energy. In the most accepted theory, energy is created as the vacuum of space expands. This contravenes the conservation of energy. The law of conservation of energy does not hold in curved spacetime but isn't our universe flat spacetime ...
  7. cHaRLie Bi0NiC

    B Quantum entanglement mechanics

    I should clarify, I am a linux administrator by trade and I have no physics or scientific background outside of working at a medical institute, So if my ideas are off and seem wild and misguided, please forgive my ignorance, and while you are at it be grateful for a fresh perspective. (joke) So...
  8. Brunolem33

    B Questions regarding energy in the universe

    As I am watching the current season of How the Universe Works, I am a bit confused when listening to physicists talking about energy as if it was a thing. The way I understand it, energy doesn't exist by itself, but is rather the result of interactions involving matter. Energy is released...
  9. Ranku

    I Variable dark energy

    If dark energy density were to vary with time, in the equation of state w = p/ρ, would p remain constant and only ρ vary?
  10. Chris Ian Burkinshaw

    A Unification of dark energy and dark matter

    Dr James Farnes of Oxford's e-Research Centre recently proposed a new model which unifies dark energy and dark matter into a single phenomenon - a fluid which possesses "negative mass". https://news.sky.com/story/mystery-of-dark-matter-may-have-been-solved-by-oxford-scientists-11572089 The paper...
  11. DLeuPel

    I Experiments on dark energy

    I’m thinking about modifying some force related equations to include dark energy in them for an essay on physics. My reasoning is that if it can separate galaxies the objects in our day to day lives must also have a small tendency to move apart. To do so, I have to dispose of an already done...
  12. Andy_K

    B Galaxy Expansion or Attraction?

    First of all, sorry for my naive question here which likely doesn't make sense. The universe is currently expanding with galaxies receding from each other at increasingly faster pace. Is it possible that the universe is a closed hypersphere system, where galaxies are actually not actively...
  13. Inani Schroedinger

    I Is the expansion actually accelerating? Or does it just appear so?

    I pulled this quote from an article on the Hubble Constant: "...for example, if the Hubble Constant was determined to be 50 km/s/Mpc, a galaxy at 10 Mpc, would have a redshift corresponding to a radial velocity of 500 km/s." In this illustration provided from the article, if this was the...
  14. M

    A Interpreting hubble data

    this graph: http://www.pnas.org/content/pnas/112/11/3173/F1.large.jpg?width=800&height=600&carousel=1 from: http://www.pnas.org/content/112/11/3173 can be found on many sites. the origin is D=0 and t=0. cosmology claims the universe is accelerating over time. the graph shows acceleration over...
  15. T

    I Why does the expanding universe redshift light?

    How does the expansion of space cause light to lose energy?
  16. Peter Morgan

    A Generalized free fields as dark matter?

    @vanhees71 reminds us that which suggests something I've wondered about for a while, whether dark matter might be adequately modeled by generalized free fields, which do not have asymptotic free states. Ray Streater, in Rep. Prog. Phys. 1975 38 771-846, "Outline of axiomatic relativistic...
  17. A

    I Black Holes and Dark Energy

    Ordinarily a black hole’s Schwarzchild radius is linearly proportional to its mass. However, wouldn’t there be a deviation from this rule for extremely large black holes? Suppose we assume dark energy is due to a cosmological constant, whose value is the same everywhere (including inside the...
  18. The Big Picture: From the Big Bang to the Meaning of Life - with Sean Carroll

    The Big Picture: From the Big Bang to the Meaning of Life - with Sean Carroll

    The talk, given at the Royal Institution in October 2016, will take us on a breath-taking journey from the origin of the Universe, through the evolution of life and consciousness, to the eternal question of what it all really means.
  19. Q&A The Big Picture - with Sean Carroll

    Q&A The Big Picture - with Sean Carroll

    Dr Sean Carroll is an astrophysicist at the California Institute of Technology. He has written a variety of popular science books along with textbooks and has long been interested in the biggest questions in astronomy: Where does probability come from? How does time work? What is dark matter?
  20. sergiokapone

    I Stress–energy pseudotensor of gravitation field for DE

    Suppose we have Einstein equation for *Universe free of matter* in form \begin{equation} G_{ik} = \chi T_{ik}, \end{equation} where the cosmological constant $\Lambda$ is transferred to the RHS of equation and written in the form of stress–energy tensor of Dark Energy...
  21. pixelperfect

    I If Dark Matter and Dark Energy exist, what produces them?

    My query is really to find out what everybody thinks about 'empty space'. Does dark matter/energy exist and if so, it fills all voids in the universe? Where does it come from? Is it produced by some force? Without DM/DE, does space even exist? Say the supernovas, the collision of neutron stars...
  22. C

    I Dark Matter and Dark Energy Conundrum

    Question 1: Do the calculations/models for galactic structure, the basis for the missing 6x mass problem that created the notion of "Dark Matter," include any factor/variable or set of variables that account for space-time dilation due to relativistic effects caused by the super-massive black...
  23. P

    I Dark matter and energy may not exist?

    https://www.sciencedaily.com/releases/2017/11/171122113013.htm How plausible does this seem?
  24. D

    B What is dark energy in the fabric of space-time?

    I know that according to Einstein's theory of relativity, space-time is like a fabric which can be pliable. Gravity is the shape, or the warping of that fabric. In this analogy, what would dark energy (the unknown form of energy that is causing the universe to expand) be?
  25. caters

    I Can gravity be negative?

    Now, I know that it is theoretically possible for negative mass to exist and for negative energy to exist. But any gravity would act on all objects and all energy, no matter if that mass and energy is positive or negative. So negative gravity would for example, pull a person upwards. Now yes, I...
  26. A

    What should I learn?

    Hello, I don't know if this is the right place to post this topic, I could not figure out the right one. I have recently finished my Masters in Condensed Matter. Now I want to follow a PhD where I can work/research on the dynamics of the Universe especially on dark energy, modified gravity...
  27. durant35

    I Expanding universe and quantum wavefunctions

    In a dark energy dominated universe, it seems that all the particles get away from each other and that the final state will be one with one or zero particles per horizon. This sounds very intuitive, but it is based on classical physics and GR. Particles have wavefunctions and this is whar...
  28. ohwilleke

    I Less gravity vs. dark energy

    One way to get the universe to expand is with dark energy that pulls at the matter of the galaxy separating it or equivalently for space-time to not be perfectly flat. An alternative, in principle, would be for the gravitational pull between objects like galaxies and galactic clusters to be...
  29. I

    B Can this be another reason for dark energy?

    Suppose the initial force and energy bursting out during big bang was very huge . The matter just after big bang would have been very close , so the gravitational attraction would have been very high , which would have caused the acceleration produced by big bang to decrease . As time increased...
  30. John M

    B Dark matter and energy creation

    If space is expanding and at the same time speeding up, something must be driving it. It also appears to be self perpetuating, as something cannot continue to expand, speed up and backfill at the same time? Could the driving force be dark matter/energy?
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