Dark energy Definition and 553 Threads

Now two points here. (1) Most Cyclic Universe theories I've heard require the universe to reverse course and fall back into a Big Crunch to recycle again. Now that Dark Energy has been discovered, the chances of a Big Crunch have gone away. (2) Some theories suggest that the universe started...

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?

New claims being made dark energy is not a cosmological constant. http://inspirehep.net/record/1511241?ln=en Any thoughts?

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...

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...

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...

When I read explanations about the early Universe and the oscillations of the photon-baryon fluid before recombination, effects of the cosmological constant and of the curvature of the Universe on the fluid are never discussed. Only dark matter, baryons, and photons are mentionned. 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...

From what I can read on the web, it seems poeple don't agree wether or not dark energy violates conservation of energy. For some, as dark energy density is constant and the Universe expands, the total energy grows. For others, that growing energy is compensated by a growing negative...

Dark energy is still energy so couldn't it also gravitate? The question is how large of a region of space must there be before dark energy could sustain itself at a higher density through self-gravitation? I'm under the impression that dark matter works at a smaller scale than dark energy. Or do...

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...

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?

PLEASE BE ADVISED: I'm a complete ignorant with regards to the details of what I'm about to say and I've never looked at the mathematics of the subject, let alone understand it. So most of what I am about to say comes from pop science. Excuse me in advance if I sound stupid or rhetorical...

William Unruh and co-authors recently published the following interesting paper where they claim to explain the observed value of cosmological constant or dark energy by taking into account the gravity of the vacuum energy of quantum field theory, which they assume is not homogeneous. How the...

https://arxiv.org/pdf/1412.2777.pdf I have always thought that Dark matter and Dark energy do not interact, but this paper says otherwise. Just because both are called Dark as a' place name for them' people think they must be akin to one another, I have always been told this is incorrect One...

After a quick and not fruitful Google Search I leave this question in better minds than my own. Q- Has there been any discussion linking the start of our Universe with a black hole? <Reason behind Question> I feel as if certain phenomenon seems quite similar to one another. A) star dies...

So say I smash a glass plate on a chess board much larger than the plate. Simplistically, say entropy is the number of ways of rearranging the glass pieces across the squares of the board. Over time, it's likely that entropy increases since the glass would spread out, meaning each configuration...

Hello guys, I was reading some models about the topology and size of the universe (always a controversial topic), then a question came to my mind. It is predicted that our universe will expand until it reaches heat death. Can a closed, finite universe also reach heat death and be described by...

Hi everyone, I was thinking of a new theory in physics regarding dark energy, black holes and the accelerating expanding universe. What if most of the matter created by the Big Bang was pushed at the edge of the new created space/time like explosions, the matter is at the edge of the explosion...

Here is a question that has been bugging me for a while… When a star is moving through space it has momentum equal to its mass times its velocity. As the star converts hydrogen into helium it loses mass as that mass is converted to energy (light) and neutrinos. Both of these escape the star...

(I suck at math... but I really like physics. In school, I flunked math on a regular basis and somehow managed to get decent physics grades... in spite of terrible math skills. But what I am good at is getting an image in my head of the physical properties of the universe and how it behaves.)...

so, i love physics, and the more i look the more it seems our understanding of things are wrong. no planet #9, but now a mysterious planet-nine, dark energy, etc etc. so my question probably lies in theory, but getting close to applied physics. planet-nine, from what i have seen, the...

Hi all! I'm new to this forum and, as a matter of fact I only recently rediscovered my interest for physics. I am starting to catch up, yet I find that Wikipedia sometimes falls sort for some basic questions, and I was hopping that this community could gently help me understand some concepts...

In the course of brushing up on my dark energy, https://arxiv.org/abs/astro-ph/0207347, The Cosmological Constant and Dark Energy, I noticed Peebles, et al, raised the possibility of evolving dark energy. Curious, I elected to do some further checking and turned up this rather startling claim...

This paper; https://arxiv.org/abs/1701.03418, Direct Probe of Dark Energy through Gravitational Lensing Effect, addresses a potential means to measure dark energy over cosmological distances. Perhaps I am a bit slow, but, I found the basic idea sufficiently simple and obvious that I am surprised...

Hey guys, I was wandering that, if dark matter and dark energy makes up 68 and 27 percentage of the the universe, then is it justifiable to study these in terms of models of the known parts of the universe which comprises of less than 5 percentage of the universe, also it is clearly evident...

Dark Energy; origin and evolution I have read the threads but I still have some unanswered questions about the origin and evolution of dark energy. Has dark energy existed since the big bang? If so, why did it remain dormant for billions of years. Or did it spontaneously jump into existence...

Is it possible that the cosmic microwave background is actually evidence of dark energy, and is driving the accelerating expansion of the universe? It seems that CMB has - and dark energy is hypothesised to have - similar properties of being uniform and all-pervasive; perhaps the theoretical...

How is ~73% of the universe made up of Dark Energy if energy doesn't take up physical space?

If everything in the universe is moving away from everything else in the universe, how can Andromeda collide in the distant future with the Milky Way?

https://en.m.wikipedia.org/wiki/Vacuum_energy And it is this type of energy dark energy or a form of it?

universe is expanding since the bigbang so therefore space is expanding, but apparently dark energy remains constant, it apparently isn't getting diluted as the universe expands is energy being created, specifically the energy in vacuum?

Hi everyone, I got the basic ideas quintessence (minimally coupled) and derived the KG equation for scalar field: $$ \ddot{\phi} + 3 H \dot{\phi} + \frac{\partial V(\phi)}{\partial \phi} = 0 $$ where $$H=\frac{\dot{a}}{a}$$ and $\phi$ is the scalar field. There are various models depending...

Imagine you could jump in space/time from Earth to a point in deep intergalactic space smack dab in the middle of a void, those regions where dark energies are at their strongest. What would the view be like? Of course it's not total dark. You still have the light of distant galaxies. Would the...

Firstly, let me apologise if my questions below are a bit elementary, stupid or if the answers are obvious. But I was curious and wanted to understand a bit more about dark energy from a very layman's point of view. So I had some fundamental questions around dark energy I wanted to ask: 1)...

I am doing a thought experiment. Keep in mind that I am not a mathematician and have never taken a physics class, so excuse me if this comes off as a "dumb" question. Is it possible that mass could cause space to spread, instead of bend/stretch? So, for instance, gravity could be like water in...

I had questions concerning the Hubble Sphere and while researching why the Hubble sphere doesn't shrink as the universe accelerates someone informed me that the universe isn't truly accelerating in its expansion as we might conventionally think. They informed me that the universe was...

Is dark energy an actual thing that can be collected or is it more like gravity, is exists but it's not really an object? Is there anything about dark matter / energy that is agreed upon by scientists or has nothing about it been confirmed at all?

I have a question. Please excuse me if this seems naive as I am not a physicist. This thing dark energy has been proposed to explain the acceleration of the expansion of the universe. From what I understand, it is everywhere. Could it be possible that dark energy really does not exist, but the...

My understanding is that one explanation of dark energy is that it is linked to vacuum energy, which is linked to virtual particles that pop in and out of existence. What I don't understand is that it space is continually expanding then the vacuum energy would also seem to be growing as...

Hi. I was wondering if someone could tell me whether there is any reason to believe that one might eventually (distant future) draw power from dark energy or dark matter as a power source for spaceships. Thanks.

What is meant by the statement by Harvard scientist Lisa Randall that dark matter carries five times the energy of ordinary matter? Does E=mc2 not apply to dark matter? Does the statement refer to ordinary energy or to dark energy?

The tital pretty much explains it all? Why would this be impossible or not explain everything?

What is dark matter? What are the effects of both dark matter and dark energy?

It is often said that dark energy is fine tuned to 120 orders of magnitude. What I understand from this is that if you use quantum field theory to predict the energy of the vacuum and compare it to observations then you are off by 120 orders of magnitude I have a few questions regarding this...

Hi all, A naive question: My understanding is that dark energy drives the expansion of space - that is, the distance between two points in space increases over time - with the important note that it is space itself that is expanding. However, when talking about gravity (where one says that...

Dark Matter is every where and always passing threw us right? It apparently hold everything in place in our universe. We know it there but can't detect it. We see the results, but we don't really see who's responsible. What If dark matter was basically a different type of gravity? And the...

If dark energy density were to be very slowly decreasing, how will the fate of the universe be any different from the energy density being constant? Would not the energy density be completely dominant in the future even if it were to be very slowly decreasing?

Greetings, I am slightly curious as to whether the LCDM model may require a slight tweaking. The reason I am curious is because I recall reading a while back that removing the homogeneity assumption from our current models could assist in accounting for some of the large-scale structures, and...

Many have claimed that if dark energy was not so small then the universe would fly apart and we wouldn't be here. However what if you increased the value of lambda and at the same increased the value of the gravitational constant ( or perhaps the amount of matter or dark matter in the universe)...