About the SA Blog Network

Degrees of Freedom

Degrees of Freedom

The boundless dimensions of math and physics
Degrees of Freedom Home

On the Physics Nobels, The Atlantic Gets Dark Energy All Wrong

The views expressed are those of the author and are not necessarily those of Scientific American.

Email   PrintPrint

Kirk and Shahna

Let's keep it within the galaxy, Jim

The piece run by The Atlantic last week on the Nobel Prizes for Physics, sadly, contained a number of misleading or inaccurate statements on physics and cosmology.

Gregg Easterbrook, the journalist who wrote it, has a storied past as a science writer. He was one of the clear-minded people who saw early on the nonsense behind the space shuttle. The full Rube Goldbergian magnificence and absurdity of it is well detailed in a masterful article by Easterbrook that is practically a history of the whole program, including its cost overruns and its deadly failures—and he wrote that in 1981.

That story makes for a chilly read. You can almost see, unfolding before your eyes, the disasters of Columbia (“The tiles are the most important system NASA has ever designed as ‘safe life.’ That means there is no back-up for them. If they fail, the shuttle burns on reentry”) and Challenger (“Here’s the plan. Suppose one of the solid-fueled boosters fails. The plan is, you die”).

More recently, his criticism of NASA’s priorities, seen for example in Wired, has been (mostly) spot on.

But Easterbrook has also periodically displayed creationist beliefs that are a bit disturbing for a science writer called on to write about the origins of life (also in Wired).

And occasionally he seems to overestimate his ability to understand science. Several years ago, Carl Zimmer took him to task for some nonsensical statements about string theory and other dimensions. Last week, Easterbrook ventured again into cosmology, on the web site od The Atlantic. Unfortunately his piece contains a number of bizarre or outright wrong statements. I don’t mean this blog to engage in character assassination, and certainly not of Easterbrook, as I like the guy, but I would just like to correct his article for the record.

His article’s summary gets it off to a bad start, by talking of “galactic expansion.” But that may be forgivable. Dark energy is often a source of confusion even for physicists. People often ask whether the expansion of space means that galaxies—or perhaps even the solar system, even Brooklyn—are expanding.

S’far as we can tell, they are not. The only thing dark energy seems able to do is make orbits imperceptibly larger than they would otherwise be. Dark energy is so dilute that it only has appreciable effects on larger scales, larger than the millions of light years of galaxy clusters.

But perhaps by “galactic expansion” the editors of The Atlantic meant the motion of galaxies with respect to one another. Let’s move on.

“Some theoreticians,” Easterbrook writes, “predicted the expansion, driven by the momentum of the Big Bang, should be slowing.” Ok.

“Eventually the galaxies would either stop their outward travel and the cosmos become static, or gravity would pull everything back together for a Big Crunch.”

Not really. As far as I know, no one thought that the universe could go from dynamic to static. In standard cosmological models that were prevalent until the end of last century, no matter how far the galaxies spread, they will still “feel” each other’s gravitational tug. The universe either expands for ever or recollapses.

“Other theoreticians felt cosmic expansion would continue at a steady pace essentially forever.”

Perhaps here Easterbrook was referring to the “steady state” universe model of Fred Hoyle. But Hoyle’s whole point was that he didn’t want to believe in a big bang, so his model was not a variant of the big bang models.

“Since the galaxies must long ago have overcome the gravity of the Big Bang in order to be rushing outward, this reasoning went, they’ll simply keep going.”

This is just so wrong I don’t even know how to unwrap it. There is no “gravity of the big bang.” If the galaxies keep going it is because the geometry of spacetime allows them to do so.

“Dark energy appears strong enough to push the entire universe - yet its source is unknown, its location is unknown and its physics are highly speculative.”

Here Easterbrook seems to picture scientists going around with a magnifying lens and saying, “where did I put the dark energy?” In reality, physicists believe that dark energy is everywhere.

“For a century, physicists have elaborately fine-tuned a concept of the natural world in which there are four fundamental forces: gravity, the ‘strong force’ that holds atoms together, the ‘weak force’ that keeps electrons in place around atoms…”

Wait, what?!?

First of all, the “elaborately fine-tuned concept of the natural world,” by which Easterbrook presumably means the Standard Model of particle physics, did not arise until the 1970s. Even wanting to be charitable, the idea that there was a fourth force was proposed 80 years ago at the most. But where Easterbrook goes stupendously wrong is in describing the weak force as holding atoms together. The weak (nuclear, to be precise) force is only involved in nuclear decay, and has nothing to do with keeping electrons in place around atoms. It is the electromagnetic force that does that.

Easterbrook goes on. “Entire academic careers have been made on work refining four-forces thinking.” Fair enough.

“Suddenly there’s a fifth force, dark energy. And although it appears to comprise three-quarters of the universe, nobody’s noticed it till now.”

Actually, although it is seductive to think that dark energy is a fifth force, it does not fairly represent mainstream physicists’ thinking, which is that dark energy is part of the stuff that fills the universe and that its effects on the expansion of the universe are gravitational–that is, entirely predictable within Albert Einstein theory of gravitation. (See Sean Carroll’s Dark Energy FAQ.)

Moreover, physicists had been conjecturing the existence of dark energy (in its incarnation as the “cosmological constant”) long before the accelerating expansion of the universe was discovered.

“It does not appear to be possible to make a vacuum in which there is nothing at all, so it is now assumed that intergalactic space is not a true void.”

But nobody ever assumed that. Space is crisscrossed by a multitude of photons—including those of the cosmic microwave background and those emitted by stars—as well as by neutrinos and by wandering cosmic rays particles such as protons.

And the fields of quantum field theory extend everywhere, so physicists did not really expect the vacuum to be totally empty. The point of the existence of dark energy is not about interstellar “true void.” Anyway dark energy, assuming it exists, would not just pervade the interstices between elementary particles, it would be truly everywhere.

Finally, Easterbrook’s concluding remark personally offended me as a Trekkie. “Intercourse between galaxies will become unimaginable,” he writes, “even if Captain Kirk’s warpdrive is invented.” But as far as I recall, Kirk never ventured much outside of the galaxy.

For reliable information about dark energy, I recommend Sean Carroll’s wonderfully clear and thorough Dark Energy FAQ.

About the Author: Davide Castelvecchi is a freelance science writer based in Rome and a contributing editor for Scientific American magazine. Follow on Twitter @dcastelvecchi.

The views expressed are those of the author and are not necessarily those of Scientific American.

Comments 11 Comments

Add Comment
  1. 1. rohlf 12:01 pm 10/16/2011

    Some things you mention are forgivable being at the frontier of cosmological knowledge, but the statements about the forces are not. However, your statement “The weak (nuclear, to be precise) force is only involved in nuclear decay…” is also not correct, for all quarks and leptons interact by the weak force, e.g., quark + antiquark –> W –> electron + neutrino, or electron + positron –> Z –> neutrino + antineutrino, etc.

    Link to this
  2. 2. KWillets 2:24 pm 10/16/2011

    There was one episode of Star Trek where the Enterprise was taken over by something or other and forced to travel towards another galaxy, with a 300-year travel time. However the journey was abandoned once intercourse was achieved.

    Link to this
  3. 3. Torbjörn Larsson, OM 5:37 pm 10/16/2011

    “I like the guy”.

    Very few does.

    As common among evolution science deniers, Easterbrook goes on to deny climate science and writes as we can see here the most incompetent* pieces on other sciences. Tim Lambert of Deltoid has been made to make a tag exclusively for Easterbrook: “Gregg Easterbrook is an idiot”.

    FWIW, even his former employment at Brookings Institute has been canceled. Remains his safe “tenure” as mouthpiece for the throwbacks of the world.

    I wouldn’t waste my time with him.

    * He looks like the typical Dunning-Kruger incompetent: too incompetent to place his lack of competence.

    Link to this
  4. 4. outsidethebox 11:13 am 10/17/2011

    Let me propose a simpler explanation of dark energy. Its a fudge factor to make a cosmological theory work when the evidence doesn’t back it up. No more complicated than that.

    Link to this
  5. 5. Will_in_BC 12:17 pm 10/17/2011

    Thanks for posting the link to the Dark Energy FAQ. I wasn’t familiar with Sean Carroll but he writes extremely well.

    Link to this
  6. 6. jtdwyer 3:02 pm 10/17/2011

    outsidethebox – Precisely.

    Even presuming all of the standard assumptions used in observational studies of type Ia supernovae that effectively established the accelerating universe hypothesis within the astrophysics community, there are still several issues regarding their critical luminosities that have not been definitively determined.

    One uncertainty is the effect of temporally varying metalicity on type Ia supernovae peak emission luminosity, used to precisely derive their distances that (for more distant supernovae only) conflicted with standard cosmological models presuming deceleration. It is currently presumed to have no effect, but the metalicity of more distant type Ia SNe should be different from that of nearer type Ia SNe and its effect has not yet been determined. Please see:

    Link to this
  7. 7. poeteye 6:38 pm 10/17/2011

    — James Ph. Kotsybar

    Could inflation have done more than we know,
    shortly after the Big Bang’s first salvo,
    and created a dense matter halo
    beyond the horizon where we can go?

    Beyond the horizon that we can see,
    is there a remote possibility
    of a most massive field of gravity
    that pulls the strings of our reality?

    Perhaps it’s just dense matter that’s the source,
    accelerating expansion perforce,
    and not some new and mysterious force,
    or change of gravity’s attractive course,
    as though we are bound by a black hole’s skin,
    that stretches space to surface dimension.

    Link to this
  8. 8. caleb_scharf 8:45 pm 10/17/2011

    Just to be clear, although the SNIa surveys have provided the best/cleanest evidence thus far for an accelerating universe there are other independent observations that have for a long time indicated that a flat but low density cosmology (hence one with a vacuum energy density to get flatness) is the best fit to what we see – from galaxy large-scale structure surveys to the growth of galaxy clusters with time, to the angular diameter variation (and hence global geometry of spacetime) of clusters. So while it’s true that there may still be a few questions about the SNIa as standard candles the overall picture is definitely one in which matter does not dominate the total energy content of the universe. It takes the SNIa though to see the transition from deceleration to acceleration at high redshift as the vacuum energy (dark energy if you want) density – which is a constant – begins to exceed the mass energy density – which is dropping as spacetime expands.

    Link to this
  9. 9. caleb_scharf 9:00 pm 10/17/2011

    ..oh, and yeah, Easterbrook sounds like he has absolutely no understanding, or apparent willingness to do research before putting pen to paper….

    Link to this
  10. 10. Postman1 8:42 pm 10/18/2011

    “What we see is that thirteen billion years ago galaxies were moving away fast, but ten billion years ago, they weren’t moving quite as fast. At eight billion, even slower, and so on until, in the recent past (close objects), they aren’t moving away at all. In fact the Andromeda galaxy is moving towards us. This seems totally contradictory to the accelerating expansion theory” We don’t have any way to know what is happening now, 13.7 billion light years away from here.

    Link to this
  11. 11. Donzzz 4:57 pm 10/21/2011

    Galaxies are simply falling outward towards the boundary of a finite universe powered by a mysterious attractive force located at the boundary causing the galaxies to accelerate toward it. This force could be called “dark energy” or the “5th force”.

    Link to this

Add a Comment
You must sign in or register as a member to submit a comment.

More from Scientific American

Email this Article