back to article PHYSICS APPLECART UPSET as dark energy disappears, Universe slams on brakes

In-the-dark astrophysicists now think there's probably less dark energy knocking about than was previously thought – which may suggest that the universe is expanding at a slower rate. That's at least the latest thinking on the subject to come out of the University of Arizona, whose team of astronomers claimed that their …

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  1. This post has been deleted by its author

    1. John H Woods

      Analogy

      I think in the UK you might need a time machine to sample a selection of 100W light bulbs at the hardware store ...

      ... but it seemed like a misquote, because it's really sampling them and finding they fall into two distinct populations, rather than simply that they 'vary'

      1. Elmer Phud

        Re: Analogy

        "I think in the UK you might need a time machine to sample a selection of 100W light bulbs at the hardware store ..."

        Nah, you only have to ask . . .

        1. This post has been deleted by its author

          1. MondoMan
            Thumb Up

            Re: Analogy

            Real men used 25-pin D connectors for their serial connections!

        2. Anonymous Coward
          Anonymous Coward

          Re: Analogy

          "Nah, you only have to ask . . ."

          If you really have a time machine then that should be "you only will have had to have asked"...

    2. Anonymous Coward
      Anonymous Coward

      Science is self-correcting

      They should stop being so adamant that their theory du jour is the ultimate final truth. That's too often how it's presented, almost as if their conclusions can be chiseled into stone tablets...

      Need more "we current have evidence that suggests" and less "is".

      If I want self-confident assurance of ultimate truth, then I'd be checking out my local church.

      1. Mad Chaz

        Re: Science is self-correcting

        I don't think I ever read a scientist's words as saying what you accuse them of. I think you're confusing real scientist with your local "religious scientist" nutter.

        1. Tom 13

          Re: I don't think I ever read a scientist's words

          That is quite the way they've been acting, particularly with respect to dark matter, and estimating the size of the universe. My major started out there before I migrated to the liberal arts. I got the concepts, just couldn't do the math. One thing that was quite clear was that the whole cosmological understanding is quite a house of cards with lots of places for error that are discounted. That isn't to say it isn't our best understanding of the data collected to date, just that everybody acts like certain things are better proven than they are.

        2. Arnold Lieberman
          Black Helicopters

          Re: Science is self-correcting

          @Mad Chaz - you've not been following climate change "science" then? It's been settled for years...

      2. Richard 12 Silver badge

        Re: Science is self-correcting

        Press release != science.

        Then the reporting of the press releases gets even further from the actual results.

        It's primarily shoddy journalists, who simply don't understand science at all, but pretend that it's just like the arts or humanities.

        1. 7

          Re: Science is self-correcting

          Commendable post. Dead on.

        2. P. Lee

          Re: Science is self-correcting

          >Then the reporting of the press releases gets even further from the actual results.

          So true. Yet, much funding comes from people who seek the certainty those press-releases provide and we end up with a cosy conspiracy of misinterpretation and exaggeration.

          I'm not so sure about science being self-correcting either. How do you know it isn't lurching from one misunderstanding of reality to another? Is that being taken on blind faith? Maybe I'm just a sceptic.

      3. TitterYeNot
        Coat

        Re: Science is self-correcting

        Blah blah physics schmysics - all I want to know is where the restaurant at the end of the universe will be and where do I deposit my penny?

    3. alain williams Silver badge

      100 watt bulbs

      The findings are analogous to sampling a selection of 100-watt light bulbs at the hardware store and discovering that they vary in brightness

      I always knew that these low energy bulbs were not what they were cracked up to be. Don't last as long as claimed either.

  2. Anonymous Coward
    Anonymous Coward

    RIGHT!

    In Jimbo's expanding bag of trivia, we read:

    The cosmological constant has negative pressure equal to its energy density and so causes the expansion of the universe to accelerate. The reason why a cosmological constant has negative pressure can be seen from classical thermodynamics; Energy must be lost from inside a container to do work on the container. A change in volume dV requires work done equal to a change of energy −P dV, where P is the pressure. But the amount of energy in a container full of vacuum actually increases when the volume increases (dV is positive), because the energy is equal to ρV, where ρ (rho) is the energy density of the cosmological constant. Therefore, P is negative and, in fact, P = −ρ.

    This sounds like a first-semester argument (a "sophomorism"?) to me, where imagery not really appropriate to the case at hand (in this case, classical thermodynamics and its macroscopic values applied to empty space in a FLRW universe) is used in a handwaving fashion to make a point, which is then underscored with mathematical formulae at high school level. A kind of student party trick, or stuff at second degree of freshness from a cranky paper.

    On what does this pressure act (frankly, it would need to push matter into a direction orthogonal to the recognized three dimensions)?. What's up with the gravitational effect of that nonzero energy (the 73% percent, natch), which would act as a tension on empty space? Why does one have an effect, but not the other?

    I DEMAND AN EXPLANATION!

    1. Mark 85 Silver badge

      Re: RIGHT!

      I DEMAND AN EXPLANATION!

      The simplest explanation: Magic!*

      *In other words.... I don't think the experts really know.

      1. amanfromMars 1 Silver badge

        Re: RIGHT! ..... Let me fix that for you

        The simplest of explanations rendered with Media and IT for AI is in a type of Kind Magic, for such cosmological speculation appears to be a prime base setting for the creation of universes and that which is generally known of as life and existence.

        And did you misspeak, Mark 85, with .....

        In other words.... I don't think the experts really know

        ..... and actually mean to share ...... In other words ..... I think, and the experts don't really know.

    2. Steve Knox
      Paris Hilton

      Re: RIGHT!

      imagery not really appropriate to the case at hand (in this case, classical thermodynamics and its macroscopic values applied to empty space in a FLRW universe)

      Why would classical thermodynamics NOT be an appropriate analogue to an FLRW universe?

      From http://en.wikipedia.org/wiki/Friedmann–Lemaître–Robertson–Walker_metric#Interpretation:

      The first equation can be derived also from thermodynamical considerations and is equivalent to the first law of thermodynamics, assuming the expansion of the Universe is an adiabatic process (which is implicitly assumed in the derivation of the Friedmann–Lemaître–Robertson–Walker metric).

      So either (a) more than one Wikipedia entry related to physical cosmology is tainted, or (b) the standard model of cosmology is analogous to a classical themodynamic system.

      I'm not an expert on cosmology, thermodynamics, or Wikipedia, but as I've seen, heard, and read physicists use classical thermodynamics to explain cosmology in other media, I'm leaning towards believing that Wikipedia's got this one right, or at least consistent with prevailing theory.

    3. Peddler

      Re: RIGHT!

      First of all, the universe is under no obligation to make sense to you. Second, read A Universe from Nothing, by Lawrence Krauss. There is only about 1% of the amount of normal matter in the universe to explain its gravitational behaviour. Gravitational lensing finds dark matter, bringing us close to 30% of the mass needed. Dark energy, remember (e=mc squared), makes up the rest of the mass and coincidentally, accounts for the acceleration in the expansion of the universe. I don't know how this new info will affect those calculations (perhaps the universe is older than 13.72 billion years?).

      1. Anonymous Coward
        Anonymous Coward

        Re: RIGHT!

        First of all, the universe is under no obligation to make sense to you.

        But the description better had otherwise we are just telling ghost stories to each other.

        makes up the rest of the mass and coincidentally, accounts for the acceleration in the expansion of the universe

        But there is the rub. Mass or Energy means gravitation means deceleration, not acceleration.

        1. Peddler

          Re: RIGHT!

          As matter, it means gravity and deceleration, as quantum vacuum energy, it means expansion. That's why the distinction between dark matter, centred around galactic clusters, and dark energy, in "empty" space. Nobody knows what either is, but their effects are measurable. Read Krauss for details; I have already gone past the end of my knowledge of cosmology and particle physics.

    4. Anonymous Coward
      Anonymous Coward

      Re: RIGHT!

      The pressure acts against gravity, and it is a pressure not a simple force because it acts throughout space (i.e. has a value which is proportional to any enclosed area through which it acts.) So it applies to the three ordinary spatial dimensions.

      Obviously I'm not intelligent enough to perceive that the argument is a sophomorism, so it just makes sense to me. If I was really clever, I wouldn't be able to understand it.

      1. Anonymous Coward
        Anonymous Coward

        Re: RIGHT!

        "Pressure" is a concept that is the statistical result of stuff bumping into each other and exchanging momentum via electrostatic force. Here we have space pressuring against stuff because someone applied a thermodynamic argument about closed containers with constant internal energy to circumscribed volumes in empty space being filled with energy isothermically via a magic energy faucet from nowhere (gridfire, anyone?). How does this make sense?

        So it applies to the three ordinary spatial dimensions.

        Really?

        Obviously I'm not intelligent enough to perceive that the argument is a sophomorism

        You should start then or politicians and their court sycophants will sell you ANYTHING.

        1. Anonymous Coward
          Anonymous Coward

          Re: RIGHT!

          ""Pressure" is a concept that is the statistical result of stuff bumping into each other and exchanging momentum via electrostatic force."

          Now I know you're just trolling. You have it exactly backward.

          Pressure, the concept, is defined as force per unit area. There is nothing in that about electrostatic force or momentum transfer. If I take two diamond anvils and apply force, there is a pressure at the interface but no momentum transfer. The pressure is RESISTED by the electric field of the electrons; the electric field is not the pressure.

          But, going a step further, what really causes, say, atmospheric pressure? It is caused by the gravitational force acting on the molecules of the air and pulling them inwards towards the centre of the earth. The reason that the air doesn't collapse to a neutron soup is indeed that electric field surrounding the atoms, but the pressure is caused by gravitation. In a neutron star, the gravity is high enough to overcome the electron fields of atoms, and the nuclei condense to a liquid. The matter of the star doesn't collapse to a point because of complex interactions between its baryons, but it has a pressure at every point and the pressure is caused by gravitation, not by the electroweak or strong forces.

          So now we have vacuum energy. Like gravitation it behaves as a field which is not mediated by photons or other particles that feel the EM force. Also like gravitation, its effect is to create a pressure on masses of particles. But, unlike gravitation which is attractive between particles, it causes a repulsion, or by extension a negative pressure. And just as the net force vector on a particle due to gravitation is in the normal three spatial directions, the repulsive force will produce a vector on a particle in the normal three spatial directions.

          I'd say it is hardly rocket science, but of course our rocket science is generally on too small a scale for vacuum energy to affect orbital calculations.

          1. Anonymous Coward
            Anonymous Coward

            Re: RIGHT!

            Now I know you're just trolling. You have it exactly backward.

            Excuse me? You really want to go back to check these physics books and statistical mechanics. But feel free to accuse me of "trolling" if that ups the ego.

            Pressure, the concept, is defined as force per unit area. There is nothing in that about electrostatic force or momentum transfer.

            You may actually start to get into that "reading" thing and find out that I didn't say anything like this. Anyway...

            but it has a pressure at every point and the pressure is caused by gravitation

            Your concepts are very unclear. As you said yourself: pressure is per unit area. Can't have pressure at a "point", captain.

            But, unlike gravitation which is attractive between particles, it causes a repulsion, or by extension a negative pressure.

            You seem to set out with what you want to prove. There is negative pressure because there is something generating negative pressure. This isn't helping.

            the repulsive force will produce a vector on a particle in the normal three spatial directions

            But as the vacuum is everywhere, where exactly is that vector pointing?

            1. Anonymous Coward
              Anonymous Coward

              Re: RIGHT!

              Yes, I've been back to check my physics books (well, actually my collection of back astrophysics papers). But not statistical mechanics because it is irrelevant here.

              You may actually start to get into that "reading" thing and find out that I didn't say anything like this.

              This is the disadvantage of your posting AC. It's possible that I have attributed to you the words posted by another AC.

              Your concepts are very unclear. As you said yourself: pressure is per unit area. Can't have pressure at a "point", captain.

              Well, I agree my terminology was a little sloppy there but this is a blog not a thesis and I think any normal person would understand what I meant. Colloquially when we say "any point on the Earth's surface", or "any point in the universe", we mean a very small defined area or volume, not something of zero size.

              In any case, it being impossible to have a meaningful discussion with an unknown number of AC nitpickers who presumably don't think much of people like Saul Perlmutter, I leave you in possession of the field, though it's a somewhat Pyrrhic victory since your desire to score debating points means that you're missing some interesting science.

              1. Sir Runcible Spoon

                Re: RIGHT!

                My knowledge and understanding of this subject is severely limited by a tiny brain, so I will stick to asking a question.

                Is it possible that there is some form of naturally occurring anti-gravity that pushes the fabric of space apart rather than bringing it together (perhaps at the baryonic level)?

                1. Vector

                  Re: RIGHT!

                  "Is it possible that there is some form of naturally occurring anti-gravity that pushes the fabric of space apart..."

                  Or, to broaden that comment: Is it possible that something besides "dark matter" and "dark energy" are behind these anomalies that have been observed?

                  I am no expert in physics or cosmology, I just have an amateur's fascination with the subject, but every time I hear those terms, I am reminded of Isaac Asimov's essay "The Planet That Wasn't" in which he describes the search by early 20th century astronomers for the planet Vulcan which, based on observed perturbations, they were sure existed inside Mercury's orbit. I don't remember the details, but it turns out something in Einstein's theories explained the anomalies perfectly and eliminated the need for a planet.

                  1. DanceMan

                    Re: RIGHT!

                    Who's the victor, Vector?

            2. This post has been deleted by its author

    5. JeffyPoooh
      Pint

      Re: RIGHT!

      Ask 'Why?' about five times and you'll stump anyone.

      In Cosmology, the five is three.

    6. Tom 13

      Re: RIGHT!

      I won't pretend to understand what some idiot thinks they wrote on Jimmy-Bob's wonder.

      From my time at uni, the simplest explanation is:

      Having calculated the speed at which various objects appear to be moving, and having determined that we all seem to be moving apart (everything observed so far has a red-shifted spectrum), when you calculate the mass of the universe based on our observations, all of the objects exceed escape velocity for the mass density of the universe.

  3. elDog

    And I could be the first one to have an up-vote for a non-sensical comment

    Free beer for you tomorrow if you think this makes any sense.

    1. Anonymous Coward
      Anonymous Coward

      Re: And I could be the first one to have an up-vote for a non-sensical comment

      Like is the case in yon JavaScript, we are unsure what you mean with "this".

    2. always a hippie

      Re: And I could be the first one to have an up-vote for a non-sensical comment

      Unlikely. Imo most comments are nonsensical, and even the worst can get up-votes.

    3. Tom 13

      Re: And I could be the first one to have an up-vote for a non-sensical comment

      Have an up vote because I'm in a contrarian mood at the moment and you have two down votes. But give the free beer to some random person. I don't drink the stuff. Much more than half a glass and I'm ready to hurl the technicolor yawn.I much prefer Gin and Tonics. Those I can suck down by the 32 oz Moose cup.

  4. Uncle Ron

    Up and Down

    It is entirely possible that the 'new calculations' will reveal that the Universe is like a roller coaster would be in the absence of friction: Outward to a certain stage, then back in to a singularity, followed by another big bang, and the process starts again, ad infinitum. Huh? I like this scenario much better than entropy.

    1. Lars Silver badge
      Happy

      Re: Up and Down

      I like that too but there still has to be a first big bang (at least in human logic) like with life, if it did not start here it still had to start somwhere. I like the multi universe theory more but sometimes I think we need to know more about the limitations of our brains to have a chance of understanding the universe,

      1. Uncle Ron

        Re: Up and Down

        Thanks. The thing is, we don't understand time. Not entirely. We know it operates at different rates in different places, and there is no privileged position, but--I'm out of my depth here. We probably -are- sitting on a giant's back or some big turtle or something. Maybe the Universe is a big Mobius strip, huh?

      2. Anonymous Coward
        Anonymous Coward

        Re: Up and Down - there still has to be a first big bang

        That is assuming that whatever the successive big bangs and big crunches take place in, "time" is a meaningful attribute of it.

        The fact that there is anything at all is the thing that has to be "explained" but may well be as beyond a human understanding as the world outside its pond is to a goldfish. Given the initial inexplicability of existence, the inexplicability of time is just a footnote.

    2. Peddler

      Re: Up and Down

      Most physicists prefer a "flat" universe, one in which the expansion slows and asymptotically approaches but never reaches zero and subsequent collapse. That way the sum of all the energy is zero and you don't have to figure out where the energy came from to create the universe in the first place.

      1. Sir Runcible Spoon

        Re: Up and Down

        "Maybe the Universe is a big Mobius strip, huh?"

        My personal experiences lead me to believe it is Torus shaped.

        During one very deep meditation on the fabric of space-time I delved into the realm of the very small, at a certain point I realised that the small was representing the large and that I had 'wrapped around' so to speak. As I continued to go smaller I ended up back where I started - only by this time I was 'looking' at the back of my own head*. YMMV.

        *I've never tried this thought experiment by going 'large' first, I expect it would end up like I was looking in a mirror.

    3. Tom 13

      Re: I like this scenario much better than entropy.

      So did Einstein, hence his creation of the "Cosmological constant" which he later called the worst mistake he ever made. The problem is, based on what we think we understand about physics, the observations just don't support it. Of course, from a Cosmological viewpoint, our observation baseline for physics is even worse than the climate baseline is for AGW.

  5. Graham Marsden
    Coat

    Well that sub-heading...

    ... went down like a Bomb!

  6. bachcole

    What?

    This is incredibly old news.

    1. Anonymous Coward
      Anonymous Coward

      Re: What?

      About 10 billion years old.

      Lightspeed is a bitch but sadly supported by postal services union universewide.

      1. Peddler

        Re: What?

        Lightspeed is the limit for going through space but space itself can do whatever the hell it wants, including expanding faster than the speed of light. Eventually, the local galactic cluster is all that will be observable from the milky way. Earth will be long gone by then.

  7. Grikath

    shouldn't the first question be...

    What has changed in the Universe?

    If those supernovae are caused by the same physical phenomena, under the same circumstances, creating the type... What Has Changed?

    Whether we're up for heat-death or contraction, or gravity-pit oblivion is ultimately a minor, if not moot question compared to this, given that it's based on several constants which should be, well.... constant.. as far as current theory goes. If there's two populations based on distance = time, we either measured wrong, or *something* happened around the border between the two.

    1. Destroy All Monsters Silver badge

      Re: shouldn't the first question be...

      Nothing has changed, this is the basic assumption (remember the "alpha changes!" flap around when Bush II went to Afghanistan ... nothing concrete ever came of that - the universe seems set in most ways)

      However these star crackers change their behaviour as the universe ages, kinda like with your bones. There is more metal around at later stages of the evolution for example. So all the physics are the same, but actual behaviours differ. Kinda like you can have hypernovae but only at early stages of the universe.

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