Dark energy Definition and 553 Threads

So DESI 3 year study results were revealed and when combined with other data from other sources it revealed a 3-sigma significant results that dark energy evolves with time, more specifically that it has been decreasing in the last 11 billion years or so...

I always thought it was odd that we know dark energy expands our universe, and that we know it has been increasing over time, yet no one ever expressed a "true" size of the universe (not "observable" universe, the ENTIRE universe) by just reversing the process of expansion based on our...

Tomorrow DESI new results from the 3 year study will be released (https://elements.lbl.gov/news/new-measurements-from-desi-shine-light-on-dark-energy/) If they find again, like in their previous release of the 1st year of the study, that dark energy appears to decrease, contrary to the...

I had been thinking the area I wanted to specialize in was theoretical astroparticle physics. After digging deeper into the exact roles of various sub-fields, I realized what I actually want to do lies in theoretical cosmology. Essentially, I want to study dark energy, or dark matter as a...

Well, I am not making any exciting claims or anything, just asking a question that I cannot stop asking myself. WE all know the Quantum theory on spontaneous generation of particles in a vacuum etc and many have asked is this linked to dark energy somehow. I like to try Einstein type Thought...

According to this Sean Carroll article, “https://www.preposterousuniverse.com/blog/2010/02/22/energy-is-not-conserved/ “ And other threads in here, depending on your definition of energy, dark energy does not violate conservation of energy, my questions is if this is true regardless of the type...

https://arstechnica.com/science/2024/04/dark-energy-might-not-be-constant-after-all/ https://www.desi.lbl.gov/2024/04/04/first-cosmology-results-from-desi-most-precise-measurement-of-the-expanding-universe/ Interesting preliminary indications from DESI (which I did not know about until now)...

I would like to ask you some questions I have about some interesting work I was reading (https://arxiv.org/abs/1205.4238 & https://academic.oup.com/mnras/article/527/4/11962/7457744) where the authors analysed the effects of dark energy in the shape and evolution of voids Apparently, they...

I am not a physicist but if someone can answer this question: It seems that there is a dark energy in the universe. Could it be associated with an (unknown) dark force acting at great distances?: I don't quite understand that when we talk about the approach of galaxies we talk in terms of force...

Does the astrophysics community really think dark energy/matter is real, or that we just haven't figured out the actual physics of what is happening and this just makes it work out (to our current understanding).

In the Lamda-CDM model of cosmology, dark-energy is explained by a Lamda like curvature of space-time. In this description, space-time is curved in such a way as to cause a gentle outward repulsive force on the large scale, expanding all of the universe over time. This is one cause of the...

https://arxiv.org/abs/0705.1688 https://ui.adsabs.harvard.edu/abs/2014IJMPD..2350054P/abstract https://www.scientificamerican.com/article/time-s-end-will-be-the-end-of-endings/ According to these references they suggest that dark energy can suddenly change sign and causing the universe expansion...

I had a question about this paper (https://arxiv.org/abs/1401.3742) There, the authors indicate that dark energy competes against gravity in oversdensities and can slow down or even prevent their collapse. I have a simple question about this: Galaxies will in principle evaporate their outer...

I was reading this interesting article about possible effects of dark energy in the formation of large-scale structures which should have an impact on the Sunyaev-Zeldovich effect ("Dark energy imprints on the kinematic Sunyaev-Zel'dovich signal" (https://arxiv.org/abs/1309.1163))There, the...

Why was the Hubble constant assumed to be decreasing and slowing down (decelerating) the expansion rate of the Universe, while at the same time Dark Energy is presumably accelerating the expansion? And to thicken the plot. recent news from NASA indicates that the Hubble constant is now...

Dark Energy puts a constrain on the size of overdensities (like clusters and superclusters of galaxies) and their growth. A higher Dark Energy density would reduce the radius of the zone where matter would be gravitationally bound, because more Dark Energy density would mean that objects would...

Regarding the following statement: "It would appear Dark matter and dark energy are what existed BEFORE the visible universe as we know it came into being. When you look at galaxies what you're seeing could be described as "displacements" in dark matter where ordinary matter formed and took...

I have a question about this work called "Dark energy and key physical parameters of clusters of galaxies"*There, towards the end, the authors talk about the isothermal velocities and tempreature parameters of the gas and particles circulating between galaxies in clusters. In particular they...

I recently found a question in a physics discussion site [1] about whether there was a "distance" between two galaxies where both the gravitational force and the influence of dark energy would be balanced. The answers and comments seem to indicate that there is indeed such a "radius" around a...

I have found some papers (like this one: https://www.aanda.org/articles/aa/full_html/2009/45/aa12762-09/aa12762-09.html) which say that dark energy increases the potential energy in a system of a quasi-stationary gravitationally bound many-body system. It also says that because of this, the...

Václav Vavryčuk has written two articles on replacing the standard FLRW metric in cosmology with what he calls a "conformal FLRW metric", which he claims explains astrophysical and cosmological phenomena traditionally attributed to dark energy and dark matter/MOND, such as the dimming of type 1a...

A group of astrophysicists have developed a method to measure the value of the cosmological constant using the dynamics of the Local Group: Constraining Dark Energy from Local Group dynamics

Is there a way to independently determine the proportion of dark energy density to total energy density of the universe apart from using 1 -(Ωmatter+Ωdark matter )?

Assuming dark energy is fairly, uniformly distributed through out the cosmos, how strong is it, or how much energy is associate with it, out in the deepest, emptiest voids in space? I'm specificlaly refering to the great voids in between the great walls of galaxy clusters. I'm making the...

[FONT=arial]Observational evidence for cosmological coupling of black holes and its implications for an astrophysical source of dark energy [FONT=arial] Comments?

It asked for a snappy title so don’t judge! I’m here for the physics not the BS. And I’ve checked my Dunning-Krugerness & Confirmation Bias at the door! In a way I’ve always been fascinated by physics and the biggest of questions but recently I thought I’d jump in and actually participate as...

Quote from NASA: My understanding of dark energy is based on NASA's report: https://science.nasa.gov/astrophysics/focus-areas/what-is-dark-energy; were NASA state as follows: "It turns out that roughly 68% of the universe is dark energy. Dark matter makes up about 27%. The rest - everything on...

The integrated Sachs-Wolfe effect occurs when a photon goes through a gravitational potential that changes due to spacetime expansion (presumably caused by dark energy). For that reason, a photon going through a gravitational well would gain energy (blueshift) when entering and it would lose...

There is an article written by astrophysicist Edward Harrison [1] which defends that energy could be extracted from attaching an imaginary cosmologically long string to a receding object from us in an expanding universe. He says that the energy extracted is potentially limited (in decelerating...

Imagine we attach an imaginary cosmological scale rope to an object that is very far away from us. Before attaching the string, the object would be receding from us due to spacetime expansion. After attaching it, tension would form in the string and we would eventually stop the object. After...

About a year ago, I heard Leonard Susskind discussing how entangled black holes could create spacetime. As I was listening to Prof. Susskind describe the mechanisms for creating entangled black holes, and how these black holes might create their own spacetime, it occurred to me that if we were...

Currently, dark energy is described as a being that exerts a negative pressure while having a positive energy density. {\rho _\Lambda } + 3{P_\Lambda } = {\rho _\Lambda } + 3( - {\rho _\Lambda }) = - 2{\rho _\Lambda } However, there seems to be a problem with the negative pressure assertion...

If we insert the values from (2.9), (2.10), (2.11) into (2.5) & (2.6) how can we get (2.13) & (2.14) ?? I need to see the calculations step by step.

since the cosmological constant observed is that there is a small amount of energy in empty space, and in general relativity anytime there is energy there is curvature and therefore gravity, how to calculate gravitational field with dark energy and does it have any observable effects on matter...

When it comes to explaining some phenomena, I think in terms of mechanisms whereas physics explains through mathematics. With this in mind, I'm trying to compare and contrast the differences between the candidate explanations for dark energy, as nicely summarised on the NASA website...

As I understand, the main theoretical virtue of Guth's inflation hypothesis is that it explains a bunch of otherwise hard-to-account-for phenomena under the standard big bang model without inflation: the Horizon Problem, the Flatness problem, the Monopole problem, and also the problem of how...

With the latest view that free space has virtual particles constantly popping in and out of existence, is it now rational to argue that light can electromagnetically travel through free space for ever and ever without the slightest energy loss? Edwin Hubble found that the general red shift of...

By analyzing 91,742 reported extra-galactic distances and their one sigma uncertainties for 14,560 galaxies, it was found that pairs of reported extra-galactic distances of the same galaxy differ from each other by 2.07 the reported uncertainties on average. In my opinion, this indicates that...

I can't see that this recent news has been discussed on PF, but the XENON1T dark matter detection collaboration is now suggesting that it has instead detected dark energy. They openly note speculation about what may have caused these results in the paper, but I'm more wondering if it adds weight...

A few days ago a new dark energy map was published, which some claim "strays from Einstein's theory of relativity". To quote from the BBC News website: "Dr Niall Jeffrey, of École Normale Supérieure, in Paris, who pieced the map together, said that the result posed a "real problem" for...

Hi, I was reading the following article. Source: https://www.forbes.com/sites/startswithabang/2019/01/31/dark-energy-may-not-be-a-constant-which-would-lead-to-a-revolution-in-physics How come the density of dark energy remains constant? Yes, if it's intrinsic to the space itself and more...

In an article published in Scientific American, authors Adam Riess and Mario Livio wrote: Why negative pressure? I would think the pressure would be positive, thus making gravity repulsive.

Here are the quotes https://www.symmetrymagazine.org/article/show-your-affection-with-physics-valentines , I find them funny except for the last one is hurtful, I shouldn't say such a thing for someone on a valentine's day because they would care about the valentine's day, personally I find it...

Hey peeps, Ok, so I need some help here. I've just been watching some videos explaining the existence of dark energy and dark matter - something which has always fascinated me. These videos pose the theory that for the first 9 billion years of the universe dark matter ruled but, for the last...

I have often read that dark matter and dark energy are now thought to comprise 94% of the total mass of the Universe. Just now I was reading an article which says that dark energy comprises 74% of the total. So, I'm confused about how energy can comprise mass. Dark matter, I can understand -...

The speed of star on the outer of are solar system is not according to the visible mass. Change the law of gravitation F = 1/r^2 to fix this. Galaxies far away are moving away with increasing speed. Change the law of gravitation F = 1/r^2 to fix this, include a repulsive force to fix. Would this...

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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...

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