Mysterious Dark Energy Played No More Than Bit Part in Early Universe

"If dark energy is a constant, then its density — the amount of dark energy per given area of space — hasn't changed over time. Meanwhile, the density of matter in the universe has changed, becoming lower and lower as the universe has expanded"

If (the amount of) dark energy remained constant as the universe expanded then DE density would go down. wouldn't it?

If (the density of dark energy) remained constant as the universe expanded then the amount of DE would have to increase. wouldn't it?

Sounds like they are saying that DE exists outside the universe.

When I design things, I find that stuff gets tacked on and complicates it. This continues until managing the complications outweighs the utility of the thing. It is good to recognize this as the point where the design has proven itself wrong. Often, when I then start over, something that is so clear and simple emerges that makes me wonder why I ever thought it could be otherwise.
I keep feeling we are at the complication nexus in our deduction of the universe' design.

This is kind if unrelated but I have a question. Is there some where (a blog perhaps) where an ametuer can ask a serious question regarding cosmology, astrophysics, etc.?

perhaps there is no such thing as dark energy ...it could be simply aspect of gravity that we simply do not understand yet..people see the effects of gravity but cannot really explain some parts of it and why its weak in some ways yet strong in others

Great comments, guys! NOt like some of the usual ones on these types of articles. Keep the ideas coming, after all that how mysteries get solved.

Now about the main difficulty... you will have to learn the math. Science, especially physics, can not be understood without a minimum amount of non-trivial math. For physics that "minimum amount" is quite a challenge. You will need linear algebra, multivariate calculus, complex numbers, basic theory of ordinary and partial differential equations and some trivial results from the theory of linear operators (with Fourier transformations as the main application) at the very least. If you want to get into general relativity, you will need some material from differential geometry... it's just something most people will have to WORK their way through before the material starts yielding the most amazing insights.

Eric, before 1920 we also didn't know what holds matter together, so we couldn't really explain what contact forces (what people usually call "force") are microscopically. However, Newton had already a rather complete macroscopic theory for them and how they relate to acceleration of solid objects.

Similarly, before 1915 we didn't have a good explanation for what gravity is, and still, with Newton's theory of gravity we could predict the movement of the solar system and large parts of the universe very, very well.

It does not take a microscopic explanation in physics to have a deep understanding of the PHENOMENOLOGY of physical effect.

With dark matter and dark energy we can observe how they change the dynamics of the universe. If we couldn't observe these obvious effects, we wouldn't be postulating either dark energy or dark matter. However, since every large scale MEASUREMENT we do implies that there have to be at least two, yet unknown, microscopic effects at work, we do assign names to them and try to figure out the details of how they act by observation.

Eventually, it could happen tomorrow or a century and then some from now, someone will come up with a microscopic explanation that satisfies all previous phenomenological observations.

That's how science works. It sees something, in this case the deviations of the large scale dynamics of the universe from what was expected in a theory without dark matter and dark energy, then works out the observational details and assigns preliminary names and then it goes on the hunt for what causes these observed effects. We have done the first two and we are working on the last part.

Since they don't even know what 'dark energy' IS, how can it be 'measured?' Based on all I have read, it appears that 'dark energy' AND 'dark matter' are merely mathematical constructs to 'fill in the inconvenient gaps' in Einstein's theoretical work, and what has been shown to be REAL and OBSERVED (but I am quite sure there will be many who will dispute this, and I am quite ready to concede a lack of expertise in this area!).

In other words, I suspect there is a HUGE reluctance by astrophysicists to return to 'first principles' and come up with a NEW theory, because even though what they have been working with so far simply cannot explain the existence of so much 'anomalous' phenomena, it is the only thing they have to work with at the moment......

Yes: we can measure the effects of dark energy/dark matter without knowing its fundamental nature; this is how we have determined that the concept of dark energy is necessary. If we couldn't measure it, we wouldn't have had any idea that there were anomalies in the standard Big Bang cosmology.

No: physicists aren't reluctant to review first principle ideas, e.g. modifying Einstein's relativity. As a matter of fact, a high percentage of research in fundamental physics is going into developing a theory melding quantum field theory and general relativity. However, there is no reason to suspect that the general conclusions of relativity would be wrong at this scale -- such as the expansion of the Universe -- despite the fact that we know it IS wrong at small distances and extremely high energy.

Yes: we have only vague hypotheses as to what's wrong with it all. It could be something fundamental which will explain everything; it could be something as trivial as measurement bias or "it is the way that it is." Most likely it's somewhere in between. Obviously, changing the whole physical paradigm is very hard to do because the new theory must, in addition to explaining dark energy & dark matter, also account for all the things that Newton, Einstein, and all the quantum mechanists have already explained.

It wouldn't be interesting if we understood it!

robertF, gravity doesn't actually exist under some theories. What is keeping us all on the earth and the earth in one piece is space which is bent around mass so that mass goes to the point of lowest energy potential which is voila what we called gravity attraction. Lot of wonderful math for that, it is still a guess as nobody has every actually detected a gravity wave which should be out there per theory.

For those who really care about physics, there are some nice resources online. MIT OpenCourseware is one. They have a few pretty good entry level courses on physics. I would recommend watching them and working through the materials. Once you do that, you basically get the very same education the MIT students can have... without the fraternities, the tests and the diploma, of course.

There are a bunch of Susskind's lectures from Stanford online... I don't know if it's the complete series. Worth watching, for sure.

I have seen plenty of lectures from Indian universities being posted online. Judging by the few minutes of material I looked at, they may be not quite as high profile as the US university products, but most likely quite useful to learn the basics.

Dark Energy: A man made fictional thing that was created just as was the now debunked Dark Matter in order to try to rationlize and explain the mathmatical discrepencies in the theories all based upon the assumption that the theory of the Big Bang is indeed fact.

If you cannot measure it, detect it, observe it directly, all you have is an idea. Is it true? You just don't know until you prove it by detecting it, observing it, etc.

Anything else is just speculation. Speculation based upon sound deductive reasoning with what we know at the moment? Perhaps, but its all just conjecture and speculation until you can detect it/observe it directly.

You know my theory? Because all galaxy exert gravity, it is only natural that when the big bang happened, everything was pulling on one another. Thus the slow expansion. When everything became farther apart due to the energy exerted when the big bang happened was/is stronger than the gravity pull, it was harder for galaxy's gravity to tug on one another. Thus more rapid expansion.

In easier terms, bang happens planets/galaxy's close together tug one another = slow expansion.

As expansion happens, gravity plays lesser a role in slow expansion which = fast expansion.

Very interesting. I might even say 'fascinating';-)
Perhaps it's ironic that Einstein's infamous 'fudge factor', literally added to keep the universe static, (Otherwise his GR predicted ultimate collapse into his most dreaded black hole/singularity) might turn out NOT to be his 'biggest blunder'.
Perhaps the 'cosmic Chesire cat might be as good a term-for it appears the 'cosmological constant' is almost as immortal and invulnerable.
For if you look at the original equation for general relativity the 'cosmological constant' is literally an addition.
As a property of space itself therefore when the universe was small it was too.
BUT, as space expands/gets larger so does the CC.
Until it becomes...what we're seeing now!

Eric1, they are not actually measuring dark energy. They are measuring variation in the microwave background intensity that under most current models is assumed to be the remnants of the big bang when matter condensed from the quarks assuming this is how matter appeared, again another guess. The problem that this article glosses over it is all a guess with a lot of very beautiful math to support the guess.

Dark matter may be the space itself that mass matter exists in. As dark matter may be the binding blocks that help keep atoms/material bind together to create an object.

Oh #$%$ I don't think these guys have any idea what they're talking about. First it was "dark matter", which was required to hold the universe together and now, in addition, theres "dark energy" which is required to explain the universal expansion. This theory makes about as much sense as the silly fairie tale espoused by Christians.

"Horatio, have you heard of any research looking for the origins of dark energy/matter"

There are many actual and proposed experiments like CDMS, XENON etc that are searching for different types of (possible) dark matter... see e.g. the paper "Direct searches for dark matter" by Bernard Sadoulet. There is a whole physics industry out there focused on this topic.

Dark energy is a different matter, entirely. It is, at this moment (and to my best knowledge), more of a problem for theoretical physics than one for experimentalists. They are going through the different self-consistent models for dark energy on the GR side and from the viewpoint of quantum field theory.

As for the "moment or process of creation of dark matter", one of the ways to look at is through the lens of mass/energy conservation. Dark matter contains most of the mass energy of the universe, so if it has been or is being created from ordinary matter (or can turn into ordinary matter itself), that will change the (thermodynamic) equations of state for both the early universe, stars, the matter distribution in galaxies etc. So you can basically ask if something unexpected has been observed about e.g. the equations for ordinary stars. If those observations were inconsistent with physics that contains only ordinary matter, one would then try to make the equations work with ordinary matter plus some amount of dark matter to get better fits. That would be indirect means of dark matter detection.

As far as I know, neither nuclear/particle physics (i.e. decay processes and high energy particle interactions observed in the lab and the computational dynamics of stars) suggests that there are strong interactions between ordinary matter and dark matter. The visible universe and its back-projected evolution to early phases of the big bang can, so far, can be modeled quite nicely with ordinary matter PLUS some additional gravitational interaction from the dark matter component. That, of course, requires some assumptions about the absence of e.g. catalytic processes that could have induced much stronger direct interactions in the early universe. But that line of reasoning is basically ruled out by Occam's razor UNTIL there is some observational evidence that requires that such strong interactions existed in the past.

It's like the big bang was meant to encounter dark energy/matter since there was so little of it when the big bang occured. Weird is a good word but does it get weirder?
If the dark energy/matter is in another dimention invading our dimention
then we will never know what the universe would be if dark energy/matter was not there.

Aethon, the best way to get your questions answered is by reading textbooks (the ones with math, not the silly ones for laymen, no matter who the authors are!) and by watching lectures. Thankfully there are ever more professional lectures online.