Dark energy Definition and 553 Threads

I'm wondering if any of the physics Jedi out there might know of any credible papers that suggest big G and/or the cosmological (dark energy) aren't constant through time?

Mass has an effect on the surrounding space which causes two massive objects within the extent of this effect to fall towards each other by crossing the space between them. There is a point source and a direction for the field. The effect of Dark energy causes an expansion of space itself and...

Hello. My current understanding (please correct, if wrong) is that the expansion of the universe is observed to be accelerating, rather than coasting or slowing down. The tentative cause of this acceleration has been given the placeholder name of 'Dark Energy'. One line of evidence for this...

Moderator's note: Spun off from another thread due to topic change. Isn't Dark Energy a continuous creation theory?

Here is a link to the Phys.org article: New evidence shows that the key assumption made in the discovery of dark energy is in error Is this going to affect the estimated age of the universe?

The reference in the summary refers to an article which has been recently accepted by The Astrophysical Journal. A draft version of the article dated December 10, 2019 is https://arxiv.org/pdf/1912.04903.pdf . The content of the draft article is way over my head, so I am hoping that...

I have come across some online references to Generic Objects of Dark Energy (GEODEs). They are briefly described in this Wikipedia article: https://en.wikipedia.org/wiki/Generic_object_of_dark_energy The only reference from that article that I have been able to find online is this paper...

Forgive my naive understanding of these topics. I have a layman's interest in science and follow all the popular science I can, but I'm certainly not a physicist and even my degree in mathematics is now all but forgotten in the past. But I have two questions (the other I'll post in another...

After watching a two-part program Everything/Nothing, a thought occurred to me when the discussion turned to particles popping in and out of 'empty' space. Could these particles be numerous enough in the vast space between stars to be responsible for the gravity holding stars together in...

Consider a particle traveling near the speed of light towards a planet- relativity states that the space according to the particle shrinks between the particle and the planet as the particle accelerates toward the planet. My question is - would the space behind the particle expand relative to an...

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?

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

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?

Ok, this question is prompted by watching a TV program on the Big Bang - sorry! Right after inflation, there was a flood of matter/anti-matter. The matter/anti-matter went through a period of annihilation but there was a residual amount of (anti-)matter left that has become our physical...

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...

Recent observations report w < -1.3 for z > 1.5. What was the dark energy density compared to matter density during that time? Was the universe briefly accelerating?

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 ...

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...

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...

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?

From the rotation curve of spiral galaxy it is found that the entire mass is not concentrated at the centre but for large distance from the central core it varies linearly with r for which the velocities(rotational) of the objects far from the central core remains nearly constt. and near to the...

Recently I have studied that from the rotation curve of spiral galaxies, the nearly constt. behaviour of velocity of the stars situated far away from the central core suggests mass(r) ~ r ,rather than 1/√r as expected. Are there any other theory which proves the existence of dark energy ??

Is Dark Energy the best term for a phenomenon that shares little resemblance to Energy as we understand it? Dark Energy seems to be a mysterious force that expands the spatial fabric of the universe over long distances, has little or no effect on gravitationally bound objects (except on a...

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...

What is the easiest way to calculate dark energy and matter density at any given age of the universe?

So I know that we believe that most galaxies are moving with a high velocity away from us. We also know that the galaxies are accelerating away from us (not only that, but they are jerking away from us as well, as in the value of the acceleration away from us is increasing), and we use dark...

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...

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...

Dark energy density at this time is a constant and our universe is expanding (accelerating). This is expected to continue indefinitely. What would happen, if for some unknown reason, dark energy density started to decrease? If over time, in billion of years or longer, dark energy density...

Although I am unable to judge this paper it should make an interesting read to toughs that can. https://arxiv.org/abs/1810.00269

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...

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...

How does the expansion of space cause light to lose energy?

So, this is a bit of an odd question, but something I was curious about. I recently learned in layman's terms that the universe is considered flat because of how we measure triangles in 3D space, in particular the CMB. I've also learned that the cosmological constant that was derived from GR...

I’m only an interested layman and my math is pretty basic so please excuse my lack expertise in this subject but I was wondering how to calculate the threshold distance an object of mass m would have to be to a system of mass M to overcome the effects of dark energy and not be receding?

So I recently had a conversation with a mathematician friend of mine who studies Einstein's equations, and he asked me this: Why do physicists call it "dark energy"? It isn't like the dark matter problem, where there is almost certainly some massive "stuff" out there gravitationally influencing...

@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...

Articles refer to white holes being associated with dark energy. What if dark energy is a larger version of the following process? Black holes banish matter into cosmic voids Some of the matter falling towards the [supermassive black] holes is converted into energy. This energy is delivered to...

Why do we need the theory of dark energy? I know the it is claimed that dark-matter has no affect on the electromagnetic spectrum. How do we know the affects attributed to dark-energy aren't affects caused by dark-matter? Dark-energy is claimed to be causing the universe to expand at an...

Do dark matter and energy affect on red shift phenomena? If yes, what, and what is the consequence of it?

Ordinarily a black hole’s Schwarzschild 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...

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.

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?

What is the dark energy which apparently is causing the expansion of the universe to accelerate?

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...

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...

I'm not quit sure whether we had this paper here already, since it is a couple of weeks old. I've seen it here https://phys.org/news/2017-12-dark-energy-mathematicians-alternative-explanation.html and I'm somehow fascinated by the idea to get rid of dark energy as only explanation of current...

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...

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

As I understand it, if you were to inject lots of dark energy into the molten core of a planet, the planet would inflate like a bubble over time until the forces of dark energy and gravity were in balance or until the bubble popped. If you were to inject dark energy into the interior of a black...