Dark energy Definition and 559 Threads

We understand that for the Universe to be flat, the critical mass of everything that has mass must total an omega of 1.0. At first, with our lack of knowledge regarding dark energy, we thought that the universe that we detected (ordinary matter and dark matter) did not even add up to a third of...

Physicists have observed the cosmic radiation background to conclude that the universe is flat (or within the margin of error of being flat). This means that the Universe contains the critical density needed to keep it flat, which is a mix of ordinary matter, dark matter and dark energy (I...

Is the amount of dark energy in the universe constant or else does it increase as the universe expands? In other words is the "anti- gravitational force" that is believed to be caused by dark energy and results in a accelerating universal expansion, a constant value or will it increase as the...

I have read that the total energy of the universe is zero and that the big bang might have emerged from a quantum fluctuation. Also that there is a chance (extremely low) of another big bang occurring in the quantum vacuum energy fluctuations. As far as I understand the vacuum energy / dark...

To quote http://science.nasa.gov/astrophysics/focus-areas/what-is-dark-energy/, "It turns out that roughly 68% of the Universe is dark energy. Dark matter makes up about 27%. The rest - everything on Earth, everything ever observed with all of our instruments, all normal matter - adds up to less...

If you measure the red-shift of a star 10 million light years away, you measure the velocity of the star 10 million years ago when the stars were traveling faster (if we are willing to accept that the expansion of the universe is slowing down). This not such an outrageous idea since firstly it...

First of I am not a scientist, just a big fan. So I am sorry for any incorrect terminology. A few years back I remember reading a article on the various theories pertaining to Dark energy. I think it may have been in a Scientific American. After the article was done talking about the most...

Hello. I'm not sure if this is an A level thread however I'll just post it here. I have a question that regards dark energy in relation to space time. I've learned that dark energy only affects space and not time. However I've also learned that space and time are intrinsically intertwined as...

So if the universe expansion is accelerating due to dark energy, does that mean that (assuming there is) one end of the universe relative to the other end of the universe will see it moving away at speeds greater than the speed of light? Or is the expansion capped by relativity? Or does the...

Okay so I've been searching the internet for this answer, but I have not yet found it. What is dark matter/dark energy? What is the difference between the two? On a website that I was on earlier, someone described dark matter as a cluster of dark energy, which would make no sense because matter...

Hi. I have no significant pure physics or math education or work experience (retired corporate analyst) but I was wondering what experts here might think about the relations between energy, dark energy and information. My understanding is that dark energy is the expansion of space, with space...

I am doing my undergrad research on Dark Matter and Dark Matter but have only few links of sources. Are there any online info-stores where I can get most of the discovered information on them. All related research papers and the different properties discovered about Dark Matter and Dark Energy...

I had a thought a while ago, but it was removed because I cited a youtube video of physicists talking rather than papers, so I'll have another go. My thought was that the universe could be cyclical and infinite even if heat death is the eventual end of the universe as we know it. During the...

I am wondering what the formula would be for the amount of Dark Energy in the observable universe would be for different time (t). (according to best current theory/data) Would it be this directly proportional to volume? Dark energy (t) = Dark energy (present time)/ (scale factor (t)3) If so...

Inflationary Theory postulates that the inflaton field and its associated particle were responsible for a huge space expansion in the very early universe. Now we observe again positive expansion, albeit at a very moderate rate, which we attribute to "dark energy" / "cosmological constant". Could...

Hi everyone. I am having a few issues completely comprehending dark energy and the expansion of the universe, and I need some clarification on certain aspects of it. Alright, so I believe that my issue lies within what really acceleration is. I am aware than as an object's distance is increased...

I'm not qualified to purpose a theory at all, however I want to ask a question to see what the problem is with my reasoning. Could someone explain why this wouldn't produce the same results as we are observing today? At the big bang, there was an expansion. At first, the rate of the expansion...

What is the expected equation for total dark energy in universe as a function of size of the universe? ie size of universe=D Dark Energy f(D)= (D^n)*constant ; where n=-2,-1,-.5,0,.5,1,2 Dark Energy f(D)= D*constant or Dark Energy f(D)= (1/D)*constant or Dark Energy = constant or Dark Energy...

Hello Friends, I, Arnendu Barman, is a high school last year student. I have much confusion in Dark Energy and Dark Matter. Actually I do not understand them and I also have problem on Negative Mass. So friend please help me . Thank you...

According to this paper not only is Dark Energy part of the field Dark Matter is too http://www.indiana.edu/~fluid/paper/HMW15.pdf In summary, we conclude that the dark matter and dark energy are essentially gravitational effect generated by the gravitational potential field gµν, its dual...

Currently, the favoured explanations for the accelerating expansion of the universe are the cosmological constant, and various scalar fields, most notably quintessence. All of these are mechanisms dependent on mathematical field properties. My question is: do any alternative hypotheses exist...

Hi, I wonder if anyone can help me understand the concept of dark energy better. I understand the very basic concept that the universe is expanding and that the rate of expansion may be speeding up (I've read somewhere that some don't think the rate is actually increasing) but how does that...

In an article called "From big bang to big bounce" published in New Scientist in 2008, author Anil Ananthaswamy outlines two different theories that lead to our universe being cyclic. 1: "Cosmologists are still very much in the dark about dark energy. Some theoretical models speculate that the...

Here is the problem link picture http://i.imgur.com/0BtcXJk.png I know that omega=density/critical density so I know I can find the value of all of those. DE is dark energy and M is matter (I'm pretty sure). I assume I have to sub that formula into equation 1, and then rearrange it to create a...

I have read that very high precision attempts to confirm the constant speed of light in all directions have been successful. For example in 2009, Stephan Schiller's lab was able to achieve a precision level that was one hundred millions times more precise than the original Michelson Morley...

Hi everyone I have been told that gravitational lensing affects CMB power spectra (TT, TE, EE) for high values of l (i.e. the least, low peaks on the right, say l>1000). But how? Isn't the effect of the varying gravitational potential along the line of sight the cause of Integrated Sachs-Wolfe...

Does the E8 theory that offered and posted by Antony Garrett Lisi,can explain the qualities and the source of the dark matter and dark energy in the universe?

This is just a short question, it might have been asked already but I couldn't find anything. I read that we have attempted to reconcile the Casimir force with the observed expansion of the universe, doing this, we get a number 10^120 times too big. This is obviously a bad number to say the...

Hello everyone. I am having some problem with dark energy and the cosmological constant. The cosmological constant is a proposed form of dark energy. Alright, now the cosmological constant is is estimated by cosmologists to on the order of 10^-26 kilograms per cubic meters. But the density of...

Hello everyone. I'm pretty new here, and I kinda joined this forum just to post this question. I have read many books on physics and cosmology, and although I have no scholastic training in it currently, I plan to study physics in college. Anyway, I get all sorts of ideas in my head, but this...

I'm not too well read in cosmology, but I know the universe is presumed to be homogeneous in space but not in time, therefore the curvature of the universe can essentially be calculated under one mean. I just have a few questions about how the universe expands and whether some proportions are...

Assuming the most common Dark Energy models, it's density remains constant even with the universe expansion. As new space volume is created, it contains the same amount of dark energy as the previously existing space for the same volume unit. If we assume that at a certain epoch of cosmic time...

The entire observable universe is contained rather graciously in this wonderful picture, for your admiration.

If we look at our own solar system, our sun is pushing gasses outwards as solar winds. Our Galaxy has what around 100 billion stars? All which most likely follow suit expelling their own atmospheres outwards as solar winds. The ratio of stars being born to stars dying is something like 350:1...

I believe this is the proper forum for this question... More properly perhaps it should be posted under the forum "Crazy ideas that are a waste of time" :-) So, basically when I first learned of the mysterious phenomenon of dark energy, this sort of occurred to me as being an "obvious"...

I am currently a physics major at UIUC. I find dark matter/energy extremely fascinating. I do not know what would be the best path to take in order for me to pursue dark energy as a career. I am sure I would need to go to graduate school, but what division of physics does dark energy fit into...

Dear PF Forum, Thanks readers for giving me so many explanations about space expansion in my previous thread. However, I've forgot to ask 2 things that I'd like to know the answer. Space is expanding. According to Hubble Law? What cause space expands? 1. Dark Energy? 2. Does space its own have...

1/2 mv2 kinetic energy of expansion and force will beΩ m(dv/dt)=m((dH/dt)D+H2D). Thats the force of expansion. But have can we describe the force of dark energy ? I thought F=P/S P=ωρc2 then force will be F=-ρc2/R2 am I right ? (ρ=dark energy density)

What If the universe has a spin, was it causing the similar results like dark energy?

This paper seems to be saying so. can the universe be logotripic, whatever that is? arXiv:1504.08355 [pdf, other] Is the Universe logotropic? Pierre-Henri Chavanis Comments: Submitted to EPJPlus Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum...

I am trying to wrap my brain around the evidence for accelerating expansion of the universe from type 1a supernovae. From what I understand, it was first realized that the universe was expanding at an increasing rate from discrepancies between the calculated distances to type 1a supernovae using...

I know there has been a lot of threads on the forum about this topic, but my question is slightly different from the others. I have recently read this article by Sean Carroll (http://www.preposterousuniverse.com/blog/2010/02/22/energy-is-not-conserved/); now, I'm completely aware (& convinced)...

I have read a number of explanation for Dark Energy. To me, it looks like the evidence has been misinterpreted. When you look very deep into space you are looking back in time to near the beginning. It makes sense that that matter will be moving away at very high velocity and as we look closer...

Physical cosmology and astronomy, dark energy is an unknown form of energy which permeates all of space and tends toaccelerate the expansion of the universe. Dark energy is the most accepted hypothesis to explain the observations since the 1990s indicating that the universe is expanding at an...

Dealing with CMB, people sometimes refer to the shift parameter; R = \sqrt{\frac{\Omega^0_m}{\Omega^0_k}}sinh(\sqrt{\Omega^0_k}\int^{z_{dec}}_{0}{\frac{dz}{E(z)}}) I know that it is related to the position of the first acoustic peak, however, the amount is around 1.7. What does this mean?! does...

Is Dark Energy a constant ? arXiv:1503.04923 [pdf, ps, other] Is there evidence for dark energy evolution? Xuheng Ding, Marek Biesiada, Shuo Cao, Zhengxiang Li, Zong-Hong Zhu Comments: 8 pages, 2 figures. Accepted for publication in the ApJL Subjects: Cosmology and Nongalactic Astrophysics...

Wondering if it's possible that black holes create dark matter and dark energy from the matter and energy they consume. Then, inflation might slow when supply is low. This would support author Tarō Gomi's theory that "everyone poops." What role would time dilation play if that's what's...

So the Universe expanded very rapidly in its very first moments (inflation). The Universe then slowed down and is speeding up again, and Dark energy is supposed to be responsible for this accelerated expansion. The cosmological constant might as well be dark energy, but why is it still being...

Why does dark energy increase along with the expansion of the universe ( I'm not even sure it does but if it dosen't please correct me :))

<<Mentor note: Edited for readability.>> <<Follow-up: futher edited to fix LaTeX tags>> Context: FRW Metric /universe, perfect comological fluid , dark/vacuum energy So the equation of state ## w \rho=p, w=-1, \rho=-p## so this clealy implies either ##p## or ##\rho## is negative. Am I correct...