Clumps of rogue Parkinson’s proteins spread to new neurons and seed more clumps | Not Exactly Rocket Science

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There are many things you don’t want gathering in large numbers, including locusts, rioters, and brain proteins. Our nerve cells contain many proteins that typically live in solitude, but occasionally gather in their thousands to form large insoluble clumps. These clumps can be disastrous. They can wreck neurons, preventing them from firing normally and eventually killing them.

Such clumps are the hallmarks of many brain diseases. The neurons of Alzheimer’s patients are riddled with tangles of a protein called tau. Those of Parkinson’s patients contain bundles, or fibrils, of another protein called alpha-synuclein. The fibrils gather into even larger clumps called Lewy bodies.

Now, Laura Volpicelli-Daley from the University of Pennsylvania School of Medicine has confirmed that the alpha-synuclein fibrils can spread. Once they’ve entered a new neuron, they can corrupt the local proteins, changing their shape and gathering them into fresh Lewy bodies. They’re like gangs that travel from town to town, inciting the locals into forming their own angry mobs.

This makes alpha-synuclein a bit like prions, the proteins that cause mad cow disease, scrapie and Creutzfeld-Jacob disease (CJD). Prions are also misshapen proteins that can convert the shape of their normal peers. But there is a crucial distinction. Prions are infectious – they don’t just spread from cell to cell, but from individual to individual. Alpha-synuclein can’t do that. “There is no evidence that Parkinson’s disease or other [diseases related to synuclein] can spread from person to person or from animal to person,” says Virginia Lee, who led the study.

Parkinson’s may be confined to a single brain, but it can spread from one part to another. Thanks to studies like these, we know more about how this happens. “This is an outstanding study,” says Patrik Brundin, who works on Parkinson’s disease at Lund University. “It adds to the string of evidence that prion-like mechanisms play an important role in the development of Parkinson’s disease.”

Others studies have suggested that alpha-synuclein fibrils can seed new clumps of diseases proteins in healthy cells. In 2008, two teams showed that normal fetal neurons develop Lewy bodies if they’re transplanted into the brains of a Parkinson’s patient. A year later, other groups showed that if you can shunt alpha-synuclein fibrils into new cells, they create more fibrils.

But all of these studies either forced the fibrils in, used massive concentrations of them, or exposed neurons to the fibrils amid a cocktail of other chemicals. Volpicelli-Daley wanted to see if the fibrils can spread their corruption under natural conditions that better mimic the brains of Parkinson’s patients.

They could. Neurons will happily absorb alpha-synuclein fibrils at normal concentrations. Once inside, they start gathering the local synuclein proteins into fibrils along the stem of the neuron. After a few days, the fibrils move into the heart of the cell, where they create Lewy bodies (note the spread of the green dye in the image above). The cell fails, and eventually dies. “We never expect that it worked so well,” says Lee.

“I like the paper very much,” says Eliezer Masliah, who studies rogue proteins in Alzheimer’s disease. However, he points out that alpha-synuclein fibrils aren’t normally found in the space between cells, so it’s not clear if neurons would have any fibrils to absorb in real life. “There is a question of physiological relevance,” he says, “but it’s possible that very small fragments of fibrils might be released from dying neurons.”

It’s valuable to get clues about how synuclein fibrils spread, but Vopicelli-Daley has done something far more important – she has developed an easy system for studying that spread in the lab. Her experimental set-up is easy to run at a large scale. She’s now in a good position to look at why neurons absorb the fibrils (no one knows), how the Lewy bodies form, how they kill neurons, and how different Parkinson’s genes influence these events. She can also scan large libraries of chemicals to search for drugs that can stop the spread of synuclein.

More broadly, Vopicelli-Daley’s study supports the idea that the spread of rogue proteins is a unifying feature of many brain diseases. Clusters of misfolded Tau and amyloid beta – proteins involved in Alzheimer’s – can instigate fresh clusters in new cells. And as I’ve written about before, a twisted version of SOD1, which causes Lou Gehrig’s disease, can travel from cell to cell and nudge normal proteins into adopting its malformed shape. All these varied diseases could be caused by molecular evangelism gone wrong.

Reference: Volpcelli-Daley, Luk, Patel, Tanik, Riddle, Stieber, Meaney, Trojanowski & Lee. 2011.  Exogenous a-Synuclein Fibrils Induce Lewy Body Pathology Leading to Synaptic Dysfunction and Neuron Death. Neuron http://dx.doi.org/10.1016/j.neuron.2011.08.033

More on neural diseases:

The House From Pixar’s Up!…in Real Life | 80beats

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Finally! After teasers released in March whetted our appetites, this maker’s dream is now airing: This week National Geographic’s DIY show “How Hard Can It Be?”, the team satisfies your hunger to see Carl Fredricksen’s balloon-propelled house in the flesh—using around 300 technicolor weather balloons and a lightweight cottage that the team was still stapling together just hours before it rose into the sky, to bob along at 10,000 feet. You can’t not root for this spunky bunch (even though this first video ends in a cliffhanger):

Luckily, with a bit of searching on the NatGeo site, you can find the clincher:

When they launched the balloon a few months ago, Wired did some back-of-the-envelope calculations on the physics involved here. Though Wired didn’t address this, we suspect that one reason they couldn’t use party balloons is that the pressure from balloons on the outside of the cluster pushing in on the ones in the center would cause them to burst. What do you think?


How Booze Can Make You Sick—and Not Just While You’re Drunk | 80beats

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Booze inhibits more than just your judgement: it impairs your immune system’s ability to fight off pathogens, according to a study published last week in the journal BMC Immunology. Researchers exposed human monocytes, a type of white blood cell vital for a functioning immune system, to an amount of alcohol equivalent to a blood alcohol concentration of 0.1 (around the legal level in most states). Compared to booze-free cells, monocytes exposed to both short- and long-term levels of alcohol produced significantly less type 1 interferons, chemicals the help recruit immune cells to stage an antiviral response (and also have anti-tumor activity). Excessive drinking has long been thought to interfere with the body’s ability to fight disease, and boozing is an important risk factor for hepatitis C and barrier to treatment in HIV. But not much had been known about the mechanisms behind the effect.

But the findings of the study weren’t all so cut and dry. For instance, cells bathed in alcohol for only a few hours showed a notable decrease in the production of tumor necrosis factor-alpha, an chemical that’s helpful in fighting pathogens but is also associated with inflammatory-related chronic conditions like rheumatoid arthritis and inflammatory bowel syndrome. Monocytes exposed to near constant levels of alcohol for a week, however, showed the opposite: a significant increase in TNF-a. More research will be required to pin down the health-related effects of these chemical fluctuations.

Reference: Maoyin Pang, Shashi Bala, Karen Kodys, Donna Catalano and Gyongyi Szabo. Inhibition of TLR8- and TLR4-induced Type I IFN induction by alcohol is different from its effects on inflammatory cytokine production in monocytes. BMC Immunology, 2011. DOI: 10.1186/1471-2172-12-55

Image: Kirti Poddar / Flickr 


Like asteroid, like moon | Bad Astronomy

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The other day I posted a great picture of Saturn and its rings taken by Cassini. While digging around in my archives looking for other posts about the rings, I found one from earlier this year that had a picture of the icy moon Enceladus with the rings in the background. When I saw the picture, I got a jolt: there was a crater chain on the surface that looks just like the one on the asteroid Vesta!

Here’s a side-by-side comparison:

Enceladus is on the left, Vesta on the right (click those links for higher-res shots). Pretty cool, huh? You can see both have two big overlapping craters of roughly the same size, and a smaller third one roughly aligned on top. The set on Vesta is nicknamed — for obvious reasons — "Snowman".

Craters like this form when the impacting object is not a single body; for example, many asteroids are known to be binaries, with both objects about the same size. Getting hit by that would leave two craters either very close together or overlapping, depending on the sizes, distances, and velocities of the impacting bodies.

Sometimes, too, there are long chains of many craters, sometimes dozens. We see those on the Moon and Mercury, for example, and they may be from comets that have disintegrated into many pieces before they hit, like the comet Shoemaker-Levy 9 did before it whacked Jupiter over and over again in 1994.

The impacts on Vesta and Enceladus look remarkably similar. But I wonder. The two big craters on Vesta both have lots of shared characteristics: size, sharp rims, and so on. They’re the two biggest craters on Vesta, so it would be very unlikely to get them so close together unless they were from the same event. But the third crater has a softer rim (implying greater age due to erosive forces like the solar wind and smaller impacts over eons), is smaller, and doesn’t quite line up with the other two. There are also several craters that size on the surface. It’s possible it’s unrelated to the other two, and coincidentally nearby.

Enceladus, though, looks like all three are related. Even though one is smaller, it lines up pretty well with the other two and has similar features. Maybe this really was a triple-system that hit. The asteroid Kleopatra, for example, has two moons (though I must note Kleopatra is big, which helps it hold on to two moons; an impact from something like that would come close to shattering a moon like Enceldaus).

I have no real scientific conclusion to draw here, except that multiple-body asteroids and comets are certainly more common than we might have thought 20 years ago. It’s amazing that the evidence for their existence was literally carved into the surfaces of other big bodies out there. With all of this new and marvelous imagery we’re getting from our robots plying the solar system, I wonder what other things we’ll learn as we build up this huge database of pictures?

Related posts:

- Icy moon and distant rings
- Vesta’s double whammy
- kaBLAMBLAMBLAM
- WHAM! Bulls-eye!


Beast of Skeptic Check | Bad Astronomy

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Every month or so I sit down (virtually) with my buddy Seth Shostak, and we record a short interview for Skeptic Check, part of the Big Picture Science podcast/radio show. Seth’s on the road right now, so they’ve put a "Beast of Skeptic Check" online, featuring some of Seth’s favorite segments. You can also just hear the part I’m in (talking Moon Hoax) on the Big Picture Science blog.

Related posts:

- Big Picture Science: climate change denial on Fox News
- Are We Alone, Little Ice Age edition
- Are we headed for a new ice age?
- The Sun may be headed for a little quiet time
- Are We Alone Skeptic Check: Tyche, or not Tyche
- Are We Alone of DEATH


Dark Energy FAQ | Cosmic Variance

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In honor of the Nobel Prize, here are some questions that are frequently asked about dark energy, or should be.

What is dark energy?

It’s what makes the universe accelerate, if indeed there is a “thing” that does that. (See below.)

So I guess I should be asking… what does it mean to say the universe is “accelerating”?

First, the universe is expanding: as shown by Hubble, distant galaxies are moving away from us with velocities that are roughly proportional to their distance. “Acceleration” means that if you measure the velocity of one such galaxy, and come back a billion years later and measure it again, the recession velocity will be larger. Galaxies are moving away from us at an accelerating rate.

But that’s so down-to-Earth and concrete. Isn’t there a more abstract and scientific-sounding way of putting it?

The relative distance between far-flung galaxies can be summed up in a single quantity called the “scale factor,” often written a(t) or R(t). The scale factor is basically the “size” of the universe, although it’s not really the size because the universe might be infinitely big — more accurately, it’s the relative size of space from moment to moment. The expansion of the universe is the fact that the scale factor is increasing with time. The acceleration of the universe is the fact that it’s increasing at an increasing rate — the second derivative is positive, in calculus-speak.

Does that mean the Hubble constant, which measures the expansion rate, is increasing?

No. The Hubble “constant” (or Hubble “parameter,” if you want to acknowledge that it changes with time) characterizes the expansion rate, but it’s not simply the derivative of the scale factor: it’s the derivative divided by the scale factor itself. Why? Because then it’s a physically measurable quantity, not something we can change by switching conventions. The Hubble constant is basically the answer to the question “how quickly does the scale factor of the universe expand by some multiplicative factor?”

If the universe is decelerating, the Hubble constant is decreasing. If the Hubble constant is increasing, the universe is accelerating. But there’s an intermediate regime in which the universe is accelerating but the Hubble constant is decreasing — and that’s exactly where we think we are. The velocity of individual galaxies is increasing, but it takes longer and longer for the universe to double in size.

Said yet another way: Hubble’s Law relates the velocity v of a galaxy to its distance d via v = H d. The velocity can increase even if the Hubble parameter is decreasing, as long as it’s decreasing more slowly than the distance is increasing.

Did the astronomers really wait a billion years and measure the velocity of galaxies again?

No. You measure the velocity of galaxies that are very far away. Because light travels at a fixed speed (one light year per year), you are looking into the past. Reconstructing the history of how the velocities were different in the past reveals that the universe is accelerating.

How do you measure the distance to galaxies so far away?

It’s not easy. The most robust method is to use a “standard candle” — some object that is bright enough to see from great distance, and whose intrinsic brightness is known ahead of time. Then you can figure out the distance simply by measuring how bright it actually looks: dimmer = further away.

Sadly, there are no standard candles.

Then what did they do?

Fortunately we have the next best thing: standardizable candles. A specific type of supernova, Type Ia, are very bright and approximately-but-not-quite the same brightness. Happily, in the 1990′s Mark Phillips discovered a remarkable relationship between intrinsic brightness and the length of time it takes for a supernova to decline after reaching peak brightness. Therefore, if we measure the brightness as it declines over time, we can correct for this difference, constructing a universal measure of brightness that can be used to determine distances.

Why are Type Ia supernovae standardizable candles?

We’re not completely sure — mostly it’s an empirical relationship. But we have a good idea: we think that SNIa are white dwarf stars that have been accreting matter from outside until they hit the Chandrasekhar Limit and explode. Since that limit is basically the same number everywhere in the universe, it’s not completely surprising that the supernovae have similar brightnesses. The deviations are presumably due to differences in composition.

But how do you know when a supernova is going to happen?

You don’t. They are rare, maybe once per century in a typical galaxy. So what you do is look at many, many galaxies with wide-field cameras. In particular you compare an image of the sky taken at one moment to another taken a few weeks later — “a few weeks” being roughly the time between new Moons (when the sky is darkest), and coincidentally about the time it takes a supernova to flare up in brightness. Then you use computers to compare the images and look for new bright spots. Then you go back and examine those bright spots closely to try to check whether they are indeed Type Ia supernovae. Obviously this is very hard and wouldn’t even be conceivable if it weren’t for a number of relatively recent technological advances — CCD cameras as well as giant telescopes. These days we can go out and be confident that we’ll harvest supernovae by the dozens — but when Perlmutter and his group started out, that was very far from obvious.

And what did they find when they did this?

Most (almost all) astronomers expected them to find that the universe was decelerating — galaxies pull on each other with their gravitational fields, which should slow the whole thing down. (Actually many astronomers just thought they would fail completely, but that’s another story.) But what they actually found was that the distant supernovae were dimmer than expected — a sign that they are farther away than we predicted, which means the universe has been accelerating.

Why did cosmologists accept this result so quickly?

Even before the 1998 announcements, it was clear that something funny was going on with the universe. There seemed to be evidence that the age of the universe was younger than the age of its oldest stars. There wasn’t as much total matter as theorists predicted. And there was less structure on large scales than people expected. The discovery of dark energy solved all of these problems at once. It made everything snap into place. So people were still rightfully cautious, but once this one startling observation was made, the universe suddenly made a lot more sense.

How do we know the supernovae not dimmer because something is obscuring them, or just because things were different in the far past?

That’s the right question to ask, and one reason the two supernova teams worked so hard on their analysis. You can never be 100% sure, but you can gain more and more confidence. For example, astronomers have long known that obscuring material tends to scatter blue light more easily than red, leading to “reddening” of stars that sit behind clouds of gas and dust. You can look for reddening, and in the case of these supernovae it doesn’t appear to be important. More crucially, by now we have a lot of independent lines of evidence that reach the same conclusion, so it looks like the original supernova results were solid.

There’s really independent evidence for dark energy?

Oh yes. One simple argument is “subtraction”: the cosmic microwave background measures the total amount of energy (including matter) in the universe. Local measures of galaxies and clusters measure the total amount of matter. The latter turns out to be about 27% of the former, leaving 73% or so in the form of some invisible stuff that is not matter: “dark energy.” That’s the right amount to explain the acceleration of the universe. Other lines of evidence come from baryon acoustic oscillations (ripples in large-scale structure whose size helps measure the expansion history of the universe) and the evolution of structure as the universe expands.

Okay, so: what is dark energy?

Glad you asked! Dark energy has three crucial properties. First, it’s dark: we don’t see it, and as far as we can observe it doesn’t interact with matter at all. (Maybe it does, but beneath our ability to currently detect.) Second, it’s smoothly distributed: it doesn’t fall into galaxies and clusters, or we would have found it by studying the dynamics of those objects. Third, it’s persistent: the density of dark energy (amount of energy per cubic light-year) remains approximately constant as the universe expands. It doesn’t dilute away like matter does.

These last two properties (smooth and persistent) are why we call it “energy” rather than “matter.” Dark energy doesn’t seem to act like particles, which have local dynamics and dilute away as the universe expands. Dark energy is something else.

That’s a nice general story. What might dark energy specifically be?

The leading candidate is the simplest one: “vacuum energy,” or the “cosmological constant.” Since we know that dark energy is pretty smooth and fairly persistent, the first guess is that it’s perfectly smooth and exactly persistent. That’s vacuum energy: a fixed amount of energy attached to every tiny region of space, unchanging from place to place or time to time. About one hundred-millionth of an erg per cubic centimeter, if you want to know the numbers.

Is vacuum energy really the same as the cosmological constant?

Yes. Don’t believe claims to the contrary. When Einstein first invented the idea, he didn’t think of it as “energy,” he thought of it as a modification of the way spacetime curvature interacted with energy. But it turns out to be precisely the same thing. (If someone doesn’t want to believe this, ask them how they would observationally distinguish the two.)

Doesn’t vacuum energy come from quantum fluctuations?

Not exactly. There are many different things that can contribute to the energy of empty space, and some of them are completely classical (nothing to do with quantum fluctuations). But in addition to whatever classical contribution the vacuum energy has, there are also quantum fluctuations on top of that. These fluctuation are very large, and that leads to the cosmological constant problem.

What is the cosmological constant problem?

If all we knew was classical mechanics, the cosmological constant would just be a number — there’s no reason for it to be big or small, positive or negative. We would just measure it and be done.

But the world isn’t classical, it’s quantum. In quantum field theory we expect that classical quantities receive “quantum corrections.” In the case of the vacuum energy, these corrections come in the form of the energy of virtual particles fluctuating in the vacuum of empty space.

We can add up the amount of energy we expect in these vacuum fluctuations, and the answer is: an infinite amount. That’s obviously wrong, but we suspect that we’re overcounting. In particular, that rough calculation includes fluctuations at all sizes, including wavelengths smaller than the Planck distance at which spacetime probably loses its conceptual validity. If instead we only include wavelengths that are at the Planck length or longer, we get a specific estimate for the value of the cosmological constant.

The answer is: 10120 times what we actually observe. That discrepancy is the cosmological constant problem.

Why is the cosmological constant so small?

Nobody knows. Before the supernovae came along, many physicists assumed there was some secret symmetry or dynamical mechanism that set the cosmological constant to precisely zero, since we certainly knew it was much smaller than our estimates would indicate. Now we are faced with both explaining why it’s small, and why it’s not quite zero. And for good measure: the coincidence problem, which is why the dark energy density is the same order of magnitude as the matter density.

Here’s how bad things are: right now, the best theoretical explanation for the value of the cosmological constant is the anthropic principle. If we live in a multiverse, where different regions have very different values of the vacuum energy, one can plausibly argue that life can only exist (to make observations and win Nobel Prizes) in regions where the vacuum energy is much smaller than the estimate. If it were larger and positive, galaxies (and even atoms) would be ripped apart; if it were larger and negative, the universe would quickly recollapse. Indeed, we can roughly estimate what typical observers should measure in such a situation; the answer is pretty close to the observed value. Steven Weinberg actually made this prediction in 1988, long before the acceleration of the universe was discovered. He didn’t push it too hard, though; more like “if this is how things work out, this is what we should expect to see…” There are many problems with this calculation, especially when you start talking about “typical observers,” even if you’re willing to believe there might be a multiverse. (I’m very happy to contemplate the multiverse, but much more skeptical that we can currently make a reasonable prediction for observable quantities within that framework.)

What we would really like is a simple formula that predicts the cosmological constant once and for all as a function of other measured constants of nature. We don’t have that yet, but we’re trying. Proposed scenarios make use of quantum gravity, extra dimensions, wormholes, supersymmetry, nonlocality, and other interesting but speculative ideas. Nothing has really caught on as yet.

Has the course of progress in string theory ever been affected by an experimental result?

Yes: the acceleration of the universe. Previously, string theorists (like everyone else) assumed that the right thing to do was to explain a universe with zero vacuum energy. Once there was a real chance that the vacuum energy is not zero, they asked whether that was easy to accommodate within string theory. The answer is: it’s not that hard. The problem is that if you can find one solution, you can find an absurdly large number of solutions. That’s the string theory landscape, which seems to kill the hopes for one unique solution that would explain the real world. That would have been nice, but science has to take what nature has to offer.

What’s the coincidence problem?

Matter dilutes away as the universe expands, while the dark energy density remains more or less constant. Therefore, the relative density of dark energy and matter changes considerably over time. In the past, there was a lot more matter (and radiation); in the future, dark energy will completely dominate. But today, they are approximately equal, by cosmological standards. (When two numbers could differ by a factor of 10100 or much more, a factor of three or so counts as “equal.”) Why are we so lucky to be born at a time when dark energy is large enough to be discoverable, but small enough that it’s a Nobel-worthy effort to do so? Either this is just a coincidence (which might be true), or there is something special about the epoch in which we live. That’s one of the reasons people are willing to take anthropic arguments seriously. We’re talking about a preposterous universe here.

If the dark energy has a constant density, but space expands, doesn’t that mean energy isn’t conserved?

Yes. That’s fine.

What’s the difference between “dark energy” and “vacuum energy”?

“Dark energy” is the general phenomenon of smooth, persistent stuff that makes the universe accelerate; “vacuum energy” is a specific candidate for dark energy, namely one that is absolutely smooth and utterly constant.

So there are other candidates for dark energy?

Yes. All you need is something that is pretty darn smooth and persistent. It turns out that most things like to dilute away, so finding persistent energy sources isn’t that easy. The simplest and best idea is quintessence, which is just a scalar field that fills the universe and changes very slowly as time passes.

Is the quintessence idea very natural?

Not really. An original hope was that, by considering something dynamical and changing rather than a plain fixed constant energy, you could come up with some clever explanation for why the dark energy was so small, and maybe even explain the coincidence problem. Neither of those hopes has really panned out.

Instead, you’ve added new problems. According to quantum field theory, scalar fields like to be heavy; but to be quintessence, a scalar field would have to be enormously light, maybe 10-30 times the mass of the lightest neutrino. (But not zero!) That’s one new problem you’ve introduced, and another is that a light scalar field should interact with ordinary matter. Even if that interaction is pretty feeble, it should still be large enough to detect — and it hasn’t been detected. Of course, that’s an opportunity as well as a problem — maybe better experiments will actually find a “quintessence force,” and we’ll understand dark energy once and for all.

How else can we test the quintessence idea?

The most direct way is to do the supernova thing again, but do it better. More generally: map the expansion of the universe so precisely that we can tell whether the density of dark energy is changing with time. This is generally cast as an attempt to measure the dark energy equation-of-state parameter w. If w is exactly minus one, the dark energy is exactly constant — vacuum energy. If w is slightly greater than -1, the energy density is gradually declining; if it’s slightly less (e.g. -1.1), the dark energy density is actually growing with time. That’s dangerous for all sorts of theoretical reasons, but we should keep our eyes peeled.

What is w?

It’s called the “equation-of-state parameter” because it relates the pressure p of dark energy to its energy density ρ, via w = p/ρ. Of course nobody measures the pressure of dark energy, so it’s a slightly silly definition, but it’s an accident of history. What really matters is how the dark energy evolves with time, but in general relativity that’s directly related to the equation-of-state parameter.

Does that mean that dark energy has negative pressure?

Yes indeed. Negative pressure is what happens when a substance pulls rather than pushes — like an over-extended spring that pulls on either end. It’s often called “tension.” This is why I advocated smooth tension as a better name than “dark energy,” but I came in too late.

Why does dark energy make the universe accelerate?

Because it’s persistent. Einstein says that energy causes spacetime to curve. In the case of the universe, that curvature comes in two forms: the curvature of space itself (as opposed to spacetime), and the expansion of the universe. We’ve measured the curvature of space, and it’s essentially zero. So the persistent energy leads to a persistent expansion rate. In particular, the Hubble parameter is close to constant, and if you remember Hubble’s Law from way up top (v = H d) you’ll realize that if H is approximately constant, v will be increasing because the distance is increasing. Thus: acceleration.

Is negative pressure is like tension, why doesn’t it pull things together rather than pushing them apart?

Sometimes you will hear something along the lines of “dark energy makes the universe accelerate because it has negative pressure.” This is strictly speaking true, but a bit ass-backwards; it gives the illusion of understanding rather than actual understanding. You are told “the force of gravity depends on the density plus three times the pressure, so if the pressure is equal and opposite to the density, gravity is repulsive.” Seems sensible, except that nobody will explain to you why gravity depends on the density plus three times the pressure. And it’s not really the “force of gravity” that depends on that; it’s the local expansion of space.

The “why doesn’t tension pull things together?” question is a perfectly valid one. The answer is: because dark energy doesn’t actually push or pull on anything. It doesn’t interact directly with ordinary matter, for one thing; for another, it’s equally distributed through space, so any pulling it did from one direction would be exactly balanced by an opposite pull from the other. It’s the indirect effect of dark energy, through gravity rather than through direct interaction, that makes the universe accelerate.

The real reason dark energy causes the universe to accelerate is because it’s persistent.

Is dark energy like antigravity?

No. Dark energy is not “antigravity,” it’s just gravity. Imagine a world with zero dark energy, except for two blobs full of dark energy. Those two blobs will not repel each other, they will attract. But inside those blobs, the dark energy will push space to expand. That’s just the miracle of non-Euclidean geometry.

Is it a new repulsive force?

No. It’s just a new (or at least different) kind of source for an old force — gravity. No new forces of nature are involved.

What’s the difference between dark energy and dark matter?

Completely different. Dark matter is some kind of particle, just one we haven’t discovered yet. We know it’s there because we’ve observed its gravitational influence in a variety of settings (galaxies, clusters, large-scale structure, microwave background radiation). It’s about 23% of the universe. But it’s basically good old-fashioned “matter,” just matter that we can’t directly detect (yet). It clusters under the influence of gravity, and dilutes away as the universe expands. Dark energy, meanwhile, doesn’t cluster, nor does it dilute away. It’s not made of particles, it’s some different kind of thing entirely.

Is it possible that there is no dark energy, just a modification of gravity on cosmological scales?

It’s possible, sure. There are at least two popular approaches to this idea: f(R) gravity , which Mark and I helped develop, and DGP gravity, by Dvali, Gabadadze, and Porati. The former is a directly phenomenological approach where you simply change the Einstein field equation by messing with the action in four dimensions, while the latter uses extra dimensions that only become visible at large distances. Both models face problems — not necessarily insurmountable, but serious — with new degrees of freedom and attendant instabilities.

Modified gravity is certainly worth taking seriously (but I would say that). Still, like quintessence, it raises more problems than it solves, at least at the moment. My personal likelihoods: cosmological constant = 0.9, dynamical dark energy = 0.09, modified gravity = 0.01. Feel free to disagree.

What does dark energy imply about the future of the universe?

That depends on what the dark energy is. If it’s a true cosmological constant that lasts forever, the universe will continue to expand, cool off, and empty out. Eventually there will be nothing left but essentially empty space.

The cosmological constant could be constant at the moment, but temporary; that is, there could be a future phase transition in which the vacuum energy decreases. Then the universe could conceivably recollapse.

If the dark energy is dynamical, any possibility is still open. If it’s dynamical and increasing (w less than -1 and staying that way), we could even get a Big Rip.

What’s next?

We would love to understand dark energy (or modified gravity) through better cosmological observations. That means measuring the equation-of-state parameter, as well as improving observations of gravity in galaxies and clusters to compare with different models. Fortunately, while the U.S. is gradually retreating from ambitious new science projects, the European Space Agency is moving forward with a satellite to measure dark energy. There are a number of ongoing ground-based efforts, of course, and the Large Synoptic Survey Telescope should do a great job once it goes online.

But the answer might be boring — the dark energy is just a simple cosmological constant. That’s just one number; what are you going to do about it? In that case we need better theories, obviously, but also input from less direct empirical sources — particle accelerators, fifth-force searches, tests of gravity, anything that would give some insight into how spacetime and quantum field theory fit together at a basic level.

The great thing about science is that the answers aren’t in the back of the book; we have to solve the problems ourselves. This is a big one.


Let’s Fund "The Astronaut’s Secret"

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The Astronaut's Secret, Kickstarter

"What is "The Astronaut's Secret"? "The Astronaut's Secret" will be a 30 minute documentary about the life of Astronaut Rich Clifford. It will uncover how he and NASA kept his Parkinson's Disease a secret for 17 years, explore the impact of the end of the Shuttle Program on Rich's life, and follow him as he speaks nationwide about the importance of Early Detection of Parkinson's Disease."

The Astronaut's Secret, official website

Keith's note: NASA Watch readers need to fund this project. I just donated $100. Rich has a compelling story to tell. If every NASA Watch reader donated just $1.00 on Tuesday, when everyone at NASA gets back to work after the three day weekend, we'd reach their funding goal well before COB.

C'mon folks. You - WE - have the collective power to do good things. THIS is a good thing. Let's do it.

NASA, Google, and Lenovo Team Up for ISS Educational Project

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Keith's note: In the very near future NASA, Google, and computer manufacturer Lenovo are set to announce an interesting educational project. As I understand the gist of the effort from various sources, students will be asked to come up with ideas for experiments that can be performed on the ISS and submit a video via YouTube that describes their idea. Winners will be selected and the experiments described in the videos will actually be performed aboard the ISS. This is an interesting way to get novel ideas onboard the ISS - and possibly to spark careers. Moreover, it is a way to show that the ISS has utility beyond the experiments proposed by a small cadre of insiders.

The odd thing about this, however, is that the largest shareholder of Lenovo is an agency of the Chinese government. According to Wikipedia: "50.4% of Lenovo is owned by public shareholders, 42.3% by Legend Holdings Limited ... Because the Chinese Academy of Sciences, a Chinese government agency, owns 65% of Legend Holdings, effectively the Chinese government owns about 27% of Lenovo and is the largest shareholder." As such, this announcement is certain to gain attention from members of Congress (such as Rep. Frank Wolf) who are constantly putting NASA on the spot vis a vis any interactions with China - direct or by proxy. One would have thought that NASA would have found a way to work with a sponsor without such an overt link to the Chinese government.

Reader note: "I received an email invite to a Lenovo / YouTube webcast on the 10th about an "interesting" and "educational" project. I'm not sure why it's embargoed until Tuesday, but I'm guessing that it relates to this post. The email I received didn't mention NASA at all though."

Keith's 7 Oct update: Here is the Space Act Agreement between NASA and Space Adventures that outlines this competition. What is odd about this Space Act Agreement is that it has milestones for this project starting in June 2011 - yet the agreement was only signed a few weeks ago in September 2011. Also, "YouTube" appears in the title of this Space Act Agreement yet no one from YouTube (or Google who owns YouTube) signed this agreement. How can they be bound to this agreement if they are not a party to it? Also, the contest is supposed to be announced in October 2011 and students only have one month to come up with an experiment. And then "certified hardware [will be] provided to NASA for launch" in March 2012 with a launch to the ISS in May 2012. Wouldn't you want to give students more time so as to have more experiments submitted - and more thought put into the preparation of the proposals? These students also have their regular classwork to do. Also, since when does NASA have an expedited process whereby payloads can go from zero to flight in 6 months? Why isn't this capability more widely advertised?

Keith's 7 Oct update: NASA PAO just issued this press release: "NASA Performs Student Experiments For Whole World To See". In this release there is a link is provided to a YouTube site called "SpaceLab" where you will see a countdown clock that says "SpaceLab Launching with Lenovo" that reaches zero at noon on Monday. Why they picked a federal holiday to announce this is a little odd.

There is some disparity between the Space Act Agreement that formally enables this project and what this press release says. The press release says "Contest entrants may submit up to three experiments in either life sciences or physics. They must submit a two-minute video application by Dec. 7 via YouTube.com." However the Space Act Agreement says "entry deadline November 2011". The press release says "Six regional finalists will be selected in March 2012. Regional finalists will receive get a flight on a ZERO-G aircraft." but the Space Act Agreement says "finalists announced January 2012".

YouTube has started its viral prelaunch marketing by tweeting "T-minus 3 days and counting... What's a @YouTube Space Lab? #SpaceLab" today and tweeting this yesterday "There's going to be a BIG launch in four days time... Subscribe at http://goo.gl/5hWYC #spacelab". No mention on the Space Adventures, YouTube, Google, or Lenovo websites though.

Keith's 8 Oct update: According to a retweet by @LenovoEducation "RT @YouTube T-minus 3 days and counting... What's a @YouTube Space Lab? #SpaceLab". A tweet from @Lenovo_ANZ "There's going to be a BIG launch in a few days time @YouTube ... Subscribe at http://goo.gl/5hWYC #spacelab". Still nothing from @SpaceAdventures

IG Asked To Do Investigation on Political Bias Inside NASA

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Rep. Lamar Smith Seeks Investigation on the Politicization of NASA

"Congressman Lamar Smith, the vice-chair of the Space & Aeronautics Subcommittee of the House Science, Space and Technology Committee, today called for NASA's inspector general to investigate the politicization of the agency. This stems from a NASA-internal report showing that Obama Administration political appointees "focus on Democratic political goals, not national goals," creating a dysfunctional and hostile work environment for NASA's career civil servants."

Keith's note: Yawn. And when Republican political appointees at NASA where doing the exact same thing that has Lamar Smith all hot and bothered, he never uttered a peep. And who works on Smith's staff? Former NASA political appointee Chris Shank (R). Pot, Kettle, Black.

NASA OIG: Investigative Summary Regarding Allegations that NASA Suppressed Climate Change Science and Denied Media Access to Dr. James E. Hansen, earlier post

"...it is our conclusion that the NASA Headquarters Office of Public Affairs' actions were inconsistent with the mandate and intent of NASA's controlling legislation--the National Aeronautics and Space Act of 1958 (Space Act) and NASA's implementing regulations--insomuch as they prevented "the widest practicable and appropriate dissemination" of information concerning NASA's activities and results. While we could not substantiate that Administration officials employed outside NASA approved or disapproved or edited specific news releases, we do, however, find by a preponderance of the evidence that the claims of inappropriate political interference made by the climate change scientists and career Public Affairs Officers were more persuasive than the arguments of the senior Public Affairs officials that their actions were due to the volume and poor quality of the draft news releases."

Internal NASA documents portray a dysfunctional, political agency, Houston Chronicle

"[Rep. Smith's] request was prompted by NASA internal documents that date to February, 2010. They come from briefings on Team Development Assessment Reports. Essentially center directors, non-technical leaders at NASA HQ and technical leaders at NASA HQ were surveyed at the time about the morale, and concerns about the agency. The briefing chart below reflects a summary of the survey results for center directors (such as Johnson Space Center's Mike Coats)"

NASA HEOMD Ignores White House Open.gov Policies

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Keith's note: I have posted questions for Beth Beck at HEOMD, sent email requests, and yet no one has responded. Based on previous dysfunctional interactions with HEOMD (SOMD and ESMD) I have to conclude that my requests are being ignored - on purpose. Yawn. Oh well, this is not exactly a new behavior on NASA's part. So much for the openness and transparency policies established by the White House that the Open.gov folks love to brag about. NASA seems to think it is exempt. I guess it is time for a bunch of old-fashioned FOIA requests.

And yes Beth, I will FOIA your complaints about me to the OGC, etc.

- NASA, Google, and Lenovo Team Up for ISS Educational Project, earlier post
- Yet Another Stealth Website NASA Can't Coordinate, earlier post
- Questions for Beth Beck Regarding FragileOasis.org, earlier post

An Amazing NASA Photo You Won’t See on NASA.gov (Update)

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Keith's 5 Oct note: What an amazing photo (larger). I found it on the FragileOasis Facebook page. But is it online at the official NASA Expedition 29 photo gallery? No. This is just insane. HEOMD EPO Lead Beth Beck doesn't even coordinate these things with other HEOMD websites, to say nothing of ignoring NASA PAO and the vastly larger audience this image would otherwise get at NASA.gov.

I am tired of watching [SOMD + ESMD = HEOMD] absolutely bungle the utilization and awareness of the vast potential of the ISS - simply because their mediocre staff are incapable of coordination with the rest of the agency with the greater good as the ultimate intent. Amateurs are not what is called for. NASA can - and must - do MUCH better.

Questions for Beth Beck Regarding FragileOasis.org, earlier post

Keith's 7 Oct note: So, Beth Beck, HEOMD EPO Lead, why isn't this utterly astonishing photo - indeed, an image that is ethereally transcendental in terms of its colors and what it depicts - an image that simply takes one's breath away - not on spaceflight.nasa.gov and http://www.nasa.gov/mission_pages/station ? What is it that you do any way? If your job is to promote ISS activities, well, you have failed. NASA.gov is not carrying your stuff and promoting it to the public.

Video: Start Your Day With A Cosmic Bang

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Keith's note: This time lapse film by Dustin Farrell is best viewed in HiDef. First noticed on Gizmodo. The music on this video is from the soundtrack of the film "Sunshine". Crank up the audio. Wake up the person in the cubicle next to you. Savor the moment. Relish the planetary and celestial goodness. NASA creates similar stuff on a daily basis - yet they stumble when it comes to doing so a coordinated way to leverage their websites and brand visibility so as to get things out to the widest audience possible.

Have a look at this photo and this photo taken by this photographer at NASA Desert RATS. I am certain the video will be amazing.

NASA employee advice: Walk down the hallway and tell the bureaucrat jerk who stands in your way of telling taxpayers what it is you do - and tell them to go pound sand. If NASA does not start to promote things like this - then others will. NASA does not have an exclusive license on promoting what is cool ... NASA runs the risk of becoming irrelevant - despite its accomplishments.

NASA and ESA Can’t Agree on Mars Strategy

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NASA, ESA: No Agreement on Mars Mission, Aviation Week

"NASA Administrator Charles Bolden and his European Space Agency counterpart, Director General Jean-Jacques Dordain, failed to settle their differences on restructuring the two agencies' joint robotic Mars exploration program at a meeting Oct. 3, and now hint that it may be time to bring Russia or another partner into the mix. At issue is how much of the joint program that was worked out when the two agencies had a brighter fiscal outlook can be salvaged in today's tougher economic environment."

Yet Another Stealth Website NASA Can’t Coordinate

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Keith's note: An interesting new website International Space Station Live!, hosted at JSC, is now online. It displays a variety of telemetry and data feeds from the ISS. But NASA is not telling anyone about this website. If you go to NASA's ISS home page there is no mention of this website. Nor is there any mention at spaceflight.nasa.gov, NASA.gov, the ISS National Laboratory page, the HEOMD home page, or the NASA Office of Education (a sponsor).

Once again, one has to ask who is actually in charge of NASA's communications activities? Clearly people at NASA's centers, directorates, and missions seem to feel that they can do anything they want - and not bother to coordinate with anyone else including NASA PAO. Now if only HEOMD's crack EPO squad can find a way to couple this real time ISS telemetry website with the Google/YouTube/Lenovo/NASA student science contest and FragileOasis.org and you could have something very, very cool to engage the public. Alas, this is unlikely to happen.

Questions for Beth Beck Regarding FragileOasis.org

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Keith's 4 Oct note: Astronaut Ron Garan recently returned to Earth. While he was on the ISS he was a rather active, creative, and effective communicator. However, the vast majority of what he sent back to Earth did not appear on a NASA.gov website. Instead, it appeared on his own effort - the officially semi-official "Fragile Oasis". Beth Beck from HEOMD runs this site. The site is operated independent of NASA PAO and of any oversight by NASA's office of communications. Contrary to established agency policy Beck decided to run it outside of the NASA portal and makes little if any effort to coordinate with the way that the rest of the agency coordinates with NASA PAO. Indeed, if you even try to find who owns the domain fragileoasis.org you are unable to do so since that information is hidden.

Now this effort has created a project wherein a Fragile Oasis Prize which is apparently going to be given out to people. Prize medals were even flown in space. According to the website: "By becoming a Fragile Oasis Crewmember, you will be able to nominate and vote on projects that you believe are making the world a better place. You can encourage those that you feel are making a difference and receive encouragement from others. You can discover people and organizations with similar goals and interests and get involved with beneficial projects."

Ron Garan did a wonderful job while he was in space as he reached out to people back on Earth - one that is worthy of emulation by future crews. It is unfortunate that Beth Beck chose to implement this project in a way that diminished its reach via the vastly more popular NASA.gov web audience.

Questions for Beth Beck:

- How much has the FragileOasis.org effort cost NASA HEOMD to date? What is the budget for this entire project?
- How long will this project continue?
- Who owns the content on this website? Who actually owns the domain FragileOasis.org?
- Which contractors have been paid to run FragileOasis.org and how much has each of them been paid?
- How were the contractors that operate FragileOasis.org selected and how is their performance on this activity tracked?
- What are the metrics you use to track FragileOasis.org effectiveness?
- What are your web traffic numbers? What is the age and geographical break down of your web traffic?
- How much web traffic did fragileoasis.org send (refer) to NASA.gov? How much web traffic did nasa.gov send to fragileoasis.org?
- What information do you retain for people who visit and join your website and is this being done in accordance with NASA/government requirements?
- How many people have signed up to "join" your website?
- What target audience(s) is this project designed to reach?
- How many times have FragileOasis.org Tweets been retweeted or mentioned?
- How many of the images and videos that Ron Garan sent back to Earth were published on a NASA.gov website?
- Why is this official (is it official?) NASA website not hosted within the NASA.gov portal?
- What are the criteria for evaluating and selecting Fragile Oasis prize winners? Who are the judges?
- How long does this FragileOasis.org competition last? How many prizes will be awarded?
- Why have there been no NASA press releases about this prize?

One last thing. Beth Beck does not like public scrutiny when it comes to questions like the ones I have asked. Not at all. Sources inside the agency report that she has formally complained to the NASA Office of General Counsel about my repeated public comments and formal inquiries about how she does her job and how her projects accomplish their intended purpose. You will recall that her disastrous NASA Buzzroom efforts were featured on NASA Watch.

Any communications or outreach person with skin this thin is most certainly in the wrong job.

Ron Garan's Earth Gazing - Who Is Actually In Charge of NASA Public Affairs?, earlier post

Keith's 5 Oct update: I haven't heard anything from Beth Beck or anyone at HEOMD or FragileOasis.org. I did not really expect to hear anything. They also deleted the link I put to this posting on the FragileOasis Facebook page. So ... I guess I'll just submit a FOIA request - and then wait for months as they drag their feet developing a non-answer to my request.

HEOMD Management Update

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Keith's note: Several months ago Assistant Associate Administrator for the International Space Station Mark Uhran had been telling people that he was going to leave NASA on or around 1 October. Those plans have apparently changed. Former Deputy Associate Administrator for NASA Exploration Systems Mission Directorate Laurie Leshin's departure led to a change in the new HEOMD management structure (due to the fusion of ESMD and SOMD) and Uhran is staying. Stay tuned.