Science says about dark energy: "So the mystery continues"

One of the most amazing scientific facts is how much of the universe is unknown to science. About 95%.

As discussed in the NASA article below (I copied it from a NASA web site), currently about 68% of all the stuff in the universe is considered to be dark energy, and nobody knows what it is. Another 27% is dark matter, and nobody knows what it is. That leaves 5% normal matter, and we do know what that is. 

Except the article says, Come to think of it, maybe it shouldn't be called "normal" matter at all, since it is such a small fraction of the universe.

I love the honest humility of science. On the whole, scientists don't try to pretend that they know something when they're actually clueless about it.

They do this in part because science has some pretty damn good bullshit detectors, so any scientist who claims to know something without evidence to back that claim up likely will be challenged by other scientists. Also, scientists embrace mystery.

That's how they make progress -- by tackling mysteries, large or small, with the goal of making the mysterious less so. You'll see that the article says repeatedly about unproven dark energy possibilities, So the mystery continues.

Contrast this with religions and religious believers.

How often do you hear someone preach from a pulpit on the theme, "When it comes to God, the mystery continues"? How many people would follow a guru who says, "While I'm trying to understand what the cosmos is all about, the mystery continues"?

Illusory certainty gets high marks in religion, but a failing grade in science. Here's the NASA article.

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Dark Energy, Dark Matter

In the early 1990s, one thing was fairly certain about the expansion of the universe. It might have enough energy density to stop its expansion and recollapse, it might have so little energy density that it would never stop expanding, but gravity was certain to slow the expansion as time went on. Granted, the slowing had not been observed, but, theoretically, the universe had to slow. The universe is full of matter and the attractive force of gravity pulls all matter together.

Then came 1998 and the Hubble Space Telescope (HST) observations of very distant supernovae that showed that, a long time ago, the universe was actually expanding more slowly than it is today. So the expansion of the universe has not been slowing due to gravity, as everyone thought, it has been accelerating. No one expected this, no one knew how to explain it. But something was causing it.

Eventually theorists came up with three sorts of explanations. Maybe it was a result of a long-discarded version of Einstein's theory of gravity, one that contained what was called a "cosmological constant." Maybe there was some strange kind of energy-fluid that filled space. Maybe there is something wrong with Einstein's theory of gravity and a new theory could include some kind of field that creates this cosmic acceleration. Theorists still don't know what the correct explanation is, but they have given the solution a name. It is called dark energy.

What Is Dark Energy?

More is unknown than is known. We know how much dark energy there is because we know how it affects the universe's expansion. Other than that, it is a complete mystery. But it is an important mystery. 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 than 5% of the universe. Come to think of it, maybe it shouldn't be called "normal" matter at all, since it is such a small fraction of the universe.

Universe Dark Energy-1 Expanding Universe

This diagram reveals changes in the rate of expansion since the universe's birth 15 billion years ago. The more shallow the curve, the faster the rate of expansion. The curve changes noticeably about 7.5 billion years ago, when objects in the universe began flying apart as a faster rate. Astronomers theorize that the faster expansion rate is due to a mysterious, dark force that is pulling galaxies apart.

Credit: NASA/STSci/Ann Feild

One explanation for dark energy is that it is a property of space. Albert Einstein was the first person to realize that empty space is not nothing. Space has amazing properties, many of which are just beginning to be understood. The first property that Einstein discovered is that it is possible for more space to come into existence. Then one version of Einstein's gravity theory, the version that contains a cosmological constant, makes a second prediction: "empty space" can possess its own energy.

Because this energy is a property of space itself, it would not be diluted as space expands. As more space comes into existence, more of this energy-of-space would appear. As a result, this form of energy would cause the universe to expand faster and faster. Unfortunately, no one understands why the cosmological constant should even be there, much less why it would have exactly the right value to cause the observed acceleration of the universe. 

Dark Matter Core Defies Explanation

This image shows the distribution of dark matter, galaxies, and hot gas in the core of the merging galaxy cluster Abell 520. The result could present a challenge to basic theories of dark matter.

Another explanation for how space acquires energy comes from the quantum theory of matter. In this theory, "empty space" is actually full of temporary ("virtual") particles that continually form and then disappear. But when physicists tried to calculate how much energy this would give empty space, the answer came out wrong - wrong by a lot. The number came out 10¹²⁰ times too big. That's a 1 with 120 zeros after it. It's hard to get an answer that bad. So the mystery continues.

Another explanation for dark energy is that it is a new kind of dynamical energy fluid or field, something that fills all of space but something whose effect on the expansion of the universe is the opposite of that of matter and normal energy. Some theorists have named this "quintessence," after the fifth element of the Greek philosophers. But, if quintessence is the answer, we still don't know what it is like, what it interacts with, or why it exists. So the mystery continues.

A last possibility is that Einstein's theory of gravity is not correct. That would not only affect the expansion of the universe, but it would also affect the way that normal matter in galaxies and clusters of galaxies behaved. This fact would provide a way to decide if the solution to the dark energy problem is a new gravity theory or not: we could observe how galaxies come together in clusters.

But if it does turn out that a new theory of gravity is needed, what kind of theory would it be? How could it correctly describe the motion of the bodies in the Solar System, as Einstein's theory is known to do, and still give us the different prediction for the universe that we need? There are candidate theories, but none are compelling. So the mystery continues.

The thing that is needed to decide between dark energy possibilities - a property of space, a new dynamic fluid, or a new theory of gravity - is more data, better data.

What Is Dark Matter?

By fitting a theoretical model of the composition of the universe to the combined set of cosmological observations, scientists have come up with the composition that we described above, ~68% dark energy, ~27% dark matter, ~5% normal matter. What is dark matter?

We are much more certain what dark matter is not than we are what it is. First, it is dark, meaning that it is not in the form of stars and planets that we see. Observations show that there is far too little visible matter in the universe to make up the 27% required by the observations.

Second, it is not in the form of dark clouds of normal matter, matter made up of particles called baryons. We know this because we would be able to detect baryonic clouds by their absorption of radiation passing through them.

Third, dark matter is not antimatter, because we do not see the unique gamma rays that are produced when antimatter annihilates with matter.

Finally, we can rule out large galaxy-sized black holes on the basis of how many gravitational lenses we see. High concentrations of matter bend light passing near them from objects further away, but we do not see enough lensing events to suggest that such objects to make up the required 25% dark matter contribution.

Abell 2744: Pandora's Cluster Revealed

One of the most complicated and dramatic collisions between galaxy clusters ever seen is captured in this new composite image of Abell 2744. The blue shows a map of the total mass concentration (mostly dark matter).

However, at this point, there are still a few dark matter possibilities that are viable. Baryonic matter could still make up the dark matter if it were all tied up in brown dwarfs or in small, dense chunks of heavy elements. These possibilities are known as massive compact halo objects, or "MACHOs". But the most common view is that dark matter is not baryonic at all, but that it is made up of other, more exotic particles like axions or WIMPS (Weakly Interacting Massive Particles).

Dark Matter Goes Missing in Oddball Galaxy

Researchers were surprised when they uncovered galaxy NGC 1052-DF2 which is missing most, if not all, of its dark matter.

 

Comments

[Dungeness]

@ Brian Ji [ How often do you hear someone preach from a pulpit on the theme, "When it comes to God, the mystery continues"? How many people would follow a guru who says, "While I'm trying to understand what the cosmos is all about, the mystery continues"? ]

Few but honest mystics who unhesitatingly say "neti, neti" (not this, not this)
to attempts to describe an absolute reality. They salute material science;
they don't purport to offer a replacement for scientific exploration of the
phenomenological world at all. Instead, they only study consciousness
itself and declare what they've experienced within themselves.

They don't promote exclusivity in searching for truth either. There's no
One and Only One Legitimate Path. No hell or condemnation for alter-
native practices either except the affirmation that for ultimate truth you
must search for answers inside your own consciousness because they
won't be found anywhere else. They remain humble in that pursuit.
Ishwar Puri says his own Guru told him at initiation: "Here's a method
that's worked for me. I hope it'll work for you. But if it doesn't and you
find something better, come back and tell me. I'll follow it too."

[Ron E.]

One aspect of the universe l like is that we are intrinsically linked to it - that is, to everything. I am composed of the same stuff as the universe

Science has made some amazing discoveries re the universe, most of it beyond me - but that's fine.

'Revelations' from religious or spiritual processes can only ever be subjective - fine for the recipient but of small use for anyone else.

[Dungeness]

@ [ 'Revelations' from religious or spiritual processes can only ever be subjective - fine for the recipient but of small use for anyone else. ]

Are the proven health and cognitive benefits of mindfulness practice not revelatory...
beyond merely subjective. Science has acknowledged them so it's inaccurate to
label the results subjective or without proven merit.

Perhaps you mean religious/spiritual processes have never -unlike Science's-
facilitated "amazing discoveries re: the universe". IMO, the mystic would object
that consciousness is part of the universe and deserves urgent study. Further
that a disclplined mindful practice can enhance greater understanding of our
universe.

Subjective only though? Not really. The revelations and cosmologies of serious
mysticism are remarkably similar and invite research themselves. A tantalizing
topic, but returning to what's known, why are there cognitive and health benefits
to their practices? What's the mechanism? Can discoveries re: consciousness
be leveraged for even greater progress... personal and scientific?

[Ron E.]

D'ness. Indeed, mindfulness and meditation can help in reducing stress and to manage various mental and physical ailments – which has more to do with psychology. That is far different from the claims of mystics who basically claim to have had revelations of a personal experience of the absolute or divine. A mystic defines mystical experience as consciousness of The Absolute, Ultimate Reality, or God. This cannot be proved by science so remains subjective.

The mystical interpretations of their own experiences certainly do not accord with science. Except, where research has shown that such experiences can be reproduced in the laboratory by various methods of brain stimulation. Ingesting chemicals and brain illnesses also can produce such states.

Science generally understands that consciousness is a product of the brain and is mostly interested in finding out the brain processes that are responsible. They do not dismiss the mystics experience but conduct measured research into how such experiences emanate from the brain and how this can be beneficial to the physical and mental well-being of people.

Just like the various mysteries that science has rescued from the supernatural over many years, consciousness and the mystic experience may some day also be shown to be a natural occurrence of the evolving universe.

[Appreciative Reader]

Dungeness, surely you see that the incidental health benefits to meditation, while real, are just that, incidental, where mysticism is concerned? It's like someone claiming that if only he could run at a certain speed at some particular time at some spot and in some direction, all the while breathing in a certain rhythm and rate, then he'd be able to fly; and then you find that all the running has made the man fit and healthy. Great and all, and objective as well; but all of it a non sequitur, no? Nothing to do with mysticism per se?

[Dungeness]

@ [ The mystical interpretations of their own experiences certainly do not accord with science. Except, where research has shown that such experiences can be reproduced in the laboratory by various methods of brain stimulation. Ingesting chemicals and brain illnesses also can produce such states. ]

Again IMO the mystic would demur with the dismissive assessment that he's
merely "interpreting" haphazard experiences. There's a disciplined path to re-
experience the same inner trajectory. It's far from "reproducing" them unreliably
via lab tests or "ingesting chemicals and/or attributing them to brain illness".
Tellingly, the same argument isn't made to explain away those "incidental"
cognitive and health benefits of mindfulness.

Also, the mystic reports -doesn't "interpret"- only what is experienced in his
consciousness. If he sees evidence of a creative power, he may term it "God"
for brevity to communicate with the masses. By the way, it's the overzealous
followers who tend to conjure up the most outlandish interpretative claims. As
for the word "God", please summon the blog police only for the more serious
semantic crimes.

[Appreciative Reader]

Amazing. Didn't you understand my very simple, and very simply presented, argument, Dungeness? You talk about what I said; you seem to want to appear to be addressing what I'd said; yet you don't, in fact, actually address the meat of what I'd said. I don't directly address the mystic claim here. That claim, generally speaking, I'm agnostic about (80% on Dawkins's scale, not half and half). But what I'm saying is the health benefits to meditating have nothing at all to do with the actual and more dramatic mystic claims. To speak of those health benefits, when discussing mystic claims, is to essentially change the subject. Whether deliberate or inadvertent, it is, in essence, a form of misdirection.

[Dungeness]

@ [ But what I'm saying is the health benefits to meditating have nothing at all to do with the actual and more dramatic mystic claims ]

Again, t think a mystic might well demur because his aim is not to
segregate mystic 'claims' into tidy little compartments for unending
argumentation. Rather, the goal is simply to testify about what he's
experienced within, the methodology he's used, and offer help to
others in that pursuit. So the mystic would prefer to discuss health
benefits supportive of the ultimate meditative aim rather than get
mired in parsing 'claims'.

A mystic 'claim' is essentially an aspiration that the mystic had
some measure of success fulfilling and wants to share. Depending
on the language, customs, and audience backgrounds, the message
presentation may differ considerably or even appear contradictory.
But context is everything and real understanding only comes with
advancement in the practice. However, overzealous followers can
and do blindly try to codify a mystic's specific words and apply them
as general rules. It inevitably becomes a confusing diversion when
only meditative experience really matters in the end.