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From time to time when I hear of an exciting astrophysics discovery I wait a day and see it reported on all over the main stream media.

So when I saw that the current theory for Dark Energy had been proven, I was surprised that it wasn't reported everywhere.

My only thought was that it was just too difficult to explain.

So as a personal challenge, here is my explanation:

Back Story One (The Cosmological Constant)

Shortly after publishing his General Relativity Theory, Einstein started checking his work and ran into a sticky problem.  Since gravity is an attraction force only, with no counter acting repulsive force, the Universe should already have collapsed.  

Since all of the scientists of the time believed that the Universe was generally static Einstein assumed there was a serious flaw in his theory and went to work.

The result was a new term in his gravitational equation called the cosmological constant.  This new part of the General Relativity theory states that space is constantly expanding by a force inherent within itself.  Thus the constantly expanding space within the Universe was preventing the Universe's gravitational collapse.

Ten years later Hubble discovered the expanding Universe and Einstein labeled the cosmological constant “his greatest blunder”.

Back Story Two (The Cosmic Microwave Background)

In its first second the Universe “inflated” from the smallest possible piece of space to a size about 1/1000 of its current size.  In that same second the Universe became filled with matter and anti-matter which proceeded to attract and annihilate each other leaving behind a Universe expanding with its own momentum and full of very high energy, short wavelength photons.

Over time, as these photons traveled through an expanding Universe, their wavelengths became longer and longer as the Universe stretched “beneath” them.

If you point a radio telescope in any direction you can record these photons that have been traveling towards us for over 13 billion years and they have very long wavelengths.  (This is the proof of the “Big Bang” theory.)

Back Story Three (A Big Crunch?)

With the “repulsive gravity” (aka “Cosmological Constant”) theory in the trash basket scientist then determined there were only two possibilities for the future of the Universe.  Either the Universe was expanding with enough momentum that it would expand forever (like how the Viking spacecraft has escaped the solar system) or as Einstein feared it would ultimately pull itself back into a “big crunch”.   In either case the expansion of the Universe was slowing down due to the pull of gravity, it was simply a question of how quickly it was slowing down.

A lot of resources and brain power was put in to determining which of these futures was in store.  

One of the side discoveries of this scientific quest was the discovery that 74% of the energy of the Universe was missing.  

In 1998, cosmology was shaken at its foundations as two research teams presented their findings.  They had discovered that while the expansion of the Universe had initially been slowing down, now the expansion is accelerating!  (They won the 2011 Nobel Prize for this discovery).

The good news for scientists was that the missing 74% of the Energy of the Universe had been found.  But what was this “dark energy”?  

Einstein’s biggest blunder, the Cosmological Constant came out of the trash bin.

If space is inherently repulsive (aka growing), then as the Universe grew it would become even more repulsive because there was just more stuff to grow and the expansion of the Universe would accelerate over time just as is observed.

However, a good and reasonable idea is not a proof.

The Proof of Dark Energy

If you made it this far then maybe you are daring enough for the rest.

As we just learned, these photons get longer as they travel through empty space because space is expanding “beneath” them.  

What would happen to these photons if they traveled through an area of space with a lot of mass (like a galaxy cluster) which would be curving space and kind of bunching it up.  (This is called a “gravity well” although I would think a “gravity bowl” would be a better name.)

Imagine yourself on a swing.  At the highest point you are not moving at all, then you accelerate down to the lowest point which is the fastest speed and then slow down until you are at the top on the other side and come to a stop.

The same type of thing happens to these photons.  As they enter the “gravity bowl” they start to “accelerate” (which because of special relativity makes their wavelengths shorter because they can’t go faster).  As they leave the “gravity bowl” they “slow down” (which makes their wavelengths longer).  When it is all done the wavelength should be the same as when they entered the gravity bowl.  Actually a little bit longer because they traveled through some expanding space.

If the “Dark Energy” / “Cosmological Constant” theory is correct then there is something called the “Sachs-Wolfe Effect” (actually the Late-time integrated Sachs–Wolfe effect, aka Rees–Sciama effect).

The Sachs-Wolfe Effect says that if space is always expanding, then the “bowl” is expanding over time also.

Image a large clay bowl on a potter’s wheel.  

If there is no friction and you release a marble at the lip of the bowl, the marble will travel up to the lip of the bowl on the other side stop, return back to the center and up to the exact place where the marble was released.

However, if after the marble is released you start widening the bowl, the bowl will become shallower.  The marble instead of traveling to the top of the bowl on the far side and stopping, it travels over the edge of the now shallower side.  This would look like something was accelerating the marble as it traveled through the bowl.

This is exactly what happens with a photon traveling through a “gravity bowl”.  It appears to be accelerated compared to its twin traveling through empty space.

This effect can only happen (we think) because the space itself is expanding and the “Dark Energy” / “Cosmological Constant” theory is correct.  And it has been proven to happen with an error possibility less than .004%

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Comment Preferences

  •  As a mathematician... (6+ / 0-)

    ...I would have to say this is a little less than satisfying as a "proof".

  •  Three cheers for physics! (4+ / 0-)

    We're 99.99999% empty space - or so I've heard. Fucking amazing! I love the Zen of it all.

    "Whenever I get the urge, I lie down 'til it passes." - Mark Twain on exercise.

    by mkor7 on Tue Oct 16, 2012 at 05:39:31 AM PDT

    •  Me too. (2+ / 0-)
      Recommended by:
      Wee Mama, mkor7

      Knock, knock...who is there? -- One more vote for Obama.

      by NCJim on Tue Oct 16, 2012 at 06:21:10 AM PDT

      [ Parent ]

    •  Actually empty space is not all that empty. (3+ / 0-)
      Recommended by:
      Wee Mama, mookins, mkor7

      Even in the emptiest of space virtual matter and anti-matter pairs are materializing and disappearing all of the time.  

      Knock, knock...who is there? -- One more vote for Obama.

      by NCJim on Tue Oct 16, 2012 at 06:28:00 AM PDT

      [ Parent ]

    •  Ever wonder if we have it all backwards...?? (1+ / 0-)
      Recommended by:

      What if space were 'full' (like a fluid) and matter was a void that space flowed into.  After all, the force of gravity can be viewed as the 3-dimensional conservation of flow applied to a fluid flowing into a point, and mass would then simply be the size of the flow (i.e. size of the void)....

      ... anti-gravity would then be a 'void' space is flowing out of ....


      and their contempt for the Latin schools was applauded by Theodoric himself, who gratified their prejudices, or his own, by declaring that the child who had trembled at a rod would never dare to look upon a sword.

      by ban48 on Tue Oct 16, 2012 at 08:35:37 AM PDT

      [ Parent ]

  •  Proof that life exists (6+ / 0-)

    On Daily Kos even during elections.

    You did an admirable job of putting this in lay terms.

    And now, I'm going to apologize for the next comment I'm going to post, because it is election time, it's what popped into my head when I read you diary title and ... well, SORRY.

    What about my Daughter's future?

    by koNko on Tue Oct 16, 2012 at 05:42:32 AM PDT

  •  Proof that skid marks exist (0+ / 0-)

    Paul Ryan's "I'm with Stoopid" boxer shorts after the debate with Joe Biden.

    What about my Daughter's future?

    by koNko on Tue Oct 16, 2012 at 05:43:46 AM PDT

  •  Dick Cheney is proof of Dark energy. (4+ / 0-)
    Recommended by:
    NCJim, tundraman, david78209, drewfromct
  •  One nice thing about being older (2+ / 0-)
    Recommended by:
    david78209, Wee Mama

    I no longer worry about appearing to be smart. So I can ask some pretty dumb questions and still feel good!

    1) Is this universe unlimited or does it expand like a balloon because of all the pieces expanding? If so, then what pushes it out?

    2) What was before the big bang?

    3) Is the dark matter actually a framework for the matter that we see? (Maybe like the string theory only strands of that string are dark matter and provide structure for the rest?

    4) If there are dimensions, is it possible that the dark matter actually provides the boundaries between?

    5) If the universe is expanding, how is it that galaxies collide?

    American Television is a vast sea of stupid. -xxdr zombiexx

    by glitterscale on Tue Oct 16, 2012 at 05:56:23 AM PDT

    •  I teach cosmology (7+ / 0-)


      1) The universe is probably infinite (if not, it is so much bigger than 14 billion light years that as a practical matter it doesn't matter).   The "expansion" just means that the distance between all points is getting bigger.   If it is infinite, there is certainly no edge or center (that's also true if it's finite, but that's a detail I'd rather not get into).

      2) This is a theological question, since it is untestable.  Yes, there are some ideas that some physicists have that might lead to testable predictions, but I don't think we can ever know.  I might be wrong...

      3) No, the dark matter basically doesn't interact with visible matter, and thus can't act as a "framework".

      4) I don't understand this question.  Of course there are dimensions (3 space, 1 time).  

      5) Time scales.  The universe is expanding slowly, and galaxies are moving around relatively quickly, so they can easily collide.  But eventually, as the expansion rate gets faster and faster, the number of collisions will drop.

      Hope this helps.

    •  I'll try (5+ / 0-)

      1)  Tough concept to visualize.  There is nothing "outside" of the Universe.

      2) TBD.   The earliest theory can track it is to a "piece" of space time ten to the minus 34 mm cubed and very hot.

      3) Dark matter is likely a type of matter that doesn't interact with radiation (light) in any manner.   Might be "super symmetry" particles.  Don't mix up Dark Energy with Dark Matter, they are two very different things.

      Actually in a way yes, dark matter is a framework for the matter we see.  In the very early universe radiation trapped normal matter, but Dark Matter was allowed to move and Dark matter established the gravitational web the normal matter fell into.

      4)  I don't believe Dark Matter is that unique.  It just doesn't interact with radiation.

      5)  The gravitational pull between galaxies is stronger than the expansion of space .  

      Knock, knock...who is there? -- One more vote for Obama.

      by NCJim on Tue Oct 16, 2012 at 06:20:07 AM PDT

      [ Parent ]

  •  The question isn't IF, the question is WHAT (1+ / 0-)
    Recommended by:
    Wee Mama

    A very nice explanation to show that dark energy exists.

    What is it?

  •  Thank you (3+ / 0-)
    Recommended by:
    highacidity, Wee Mama, NCJim

    I really enjoyed this diary.   Very nice break from election mania.


  •  I Don't Understand (1+ / 0-)
    Recommended by:
    Wee Mama

    I reread this journal but as they say, it's over my pay grade.

    •  Too easy an answer. (0+ / 0-)

      What don't you understand?

      To enjoy this kind of thing one needs a mind that likes large spaces.

      I know many people who like closed spaces and this kind of thing bothers them.  If you have a mind like that than give up.

      If not, then you have to start giving up the idea that the Universe acts the same and you experience it on the day to day level.

      We only see visible light, but we know that x-rays and microwave ovens exist.

      Did you understand that light is a wave?  If you drew an "S" on a balloon what would happen?

      Knock, knock...who is there? -- One more vote for Obama.

      by NCJim on Tue Oct 16, 2012 at 06:36:28 AM PDT

      [ Parent ]

  •  "an error possibility less than .004%" (2+ / 0-)
    Recommended by:
    One Pissed Off Liberal, mkor7

    Pffft. And you expect me to believe that? Now, on the other hand, Mitt Romney's tax plan is waaaaay more credible.

    But seriously, as an interested non-mathematician I appreciate your verbalizing this for such as I. Thanks.

    The GOP can't win on ideas. They can only win by lying, cheating, and stealing. So they do.

    by psnyder on Tue Oct 16, 2012 at 06:29:18 AM PDT

    •  You welcome. (3+ / 0-)
      Recommended by:
      psnyder, Wee Mama, mkor7

      I needed something to get my mind off of the fact that Obama is merely likely to win rather than certain to win.

      It is 99.996 certain that light waves traveling through a gravity well end up with more energy than light traveling through the same amount of empty space end up with.

      Now if it was 99.996% certain that Obama would win in November then I would only be .004% worried, but I would not stop working even then.

      Knock, knock...who is there? -- One more vote for Obama.

      by NCJim on Tue Oct 16, 2012 at 06:40:51 AM PDT

      [ Parent ]

  •  I am obsessed with stuff I can't comprehend... (2+ / 0-)
    Recommended by:
    Wee Mama, One Pissed Off Liberal

    I was never strong enough in math to read AND comprehend the scientific works that fascinate me.  Lately I'm stuck on quantumn entanglement and wondering about how interconnected this crazy place really is.  If any of you could explain/debunk/enlighten me on the subject I would be most appreciative.  

    Thanks for the exhale-diary.  Sometimes during election season I forget to breathe.

    "What is being noticed is only an indication of what is being done." Albert Einstein 1954

    by tundraman on Tue Oct 16, 2012 at 06:37:09 AM PDT

    •  Your sig line is a good place to start. (2+ / 0-)
      Recommended by:
      tundraman, Wee Mama

      Everything except space time is a wave/particle substance.

      Everything is a wave until it is required to interact and then it becomes a particle.

      You tundraman are actually a wave, but you are big enough so that you are interacting with the world all of the time so you appear to be a particle all of the time.

      Because everything you interact with is a particle (if you are interacting with it then it must be a particle), then the wave nature of things is very strange and not really comprehensible.   We just don't have any real life experience with the wave nature of the Universe.  

      There was no way and no need to evolve as beings that understood the wave nature.

      So a thing that is not interacting with anything can be very strange to us.

      Knock, knock...who is there? -- One more vote for Obama.

      by NCJim on Tue Oct 16, 2012 at 06:53:46 AM PDT

      [ Parent ]

  •  expanding vs accelerating expansion (0+ / 0-)

    I think you may have crossed two different lines here:
    1) The universe is expanding.
    2) The rate at which the universe expands is accelerating.

    Dark Energy is not an explanation for 1, it's an explanation for 2. The expansion of the universe has been understood by astronomers for a little under a century. But the acceleration of that expansion was not predicted by theory, it was detected via 'standard candle' measurements of type 1a supernovas, and more recently backed up by baryonic acoustic oscilations observed in the cosmic background microwave images.

    Previously, it was thought that gravity would slow the expansion, so an accelerating expansion required something new. This something new happened to match Einstein's cosmological constant, but there's no good explanation for why that is. Particle and theoretical physicists are starting to piece together an explanation, possibly from virtual particles/vacuum energy, but they are still a good ways from connecting the dots and having the number work out.

    •  I didn't know about the (1+ / 0-)
      Recommended by:
      Wee Mama

      baryonic acoustic oscilations.  Thanks.

      I know I crossed a few lines in the effort to make it understandable.

      There is some wonderful new science coming out about the causes of type 1a supernovas.

      Dark Energy is a vacuum energy by definition, like the Higgs field.  

      And yes there is a lot of wonderful stuff left to enjoy.

      Knock, knock...who is there? -- One more vote for Obama.

      by NCJim on Tue Oct 16, 2012 at 06:59:33 AM PDT

      [ Parent ]

  •  A question (2+ / 0-)
    Recommended by:
    drewfromct, The Jester

    The universe starts as a 'pin-point' of all that is:
    1) How long was it in that state?
    2) If any time at all, what triggered the big bang?

    Here's what my pea brain imagines. The whole process has to be cyclical. It's tough for me to think this only happened once. But after a gajillion years, maybe due to mass black holes combining, everything compresses back down to that 'pin-point' and BANG! Starts all over again.

    Your thoughts...

    Either you're wit' us or a Guinness -- Brilliant!

    by Unforgiven on Tue Oct 16, 2012 at 06:58:45 AM PDT

    •  It was in that state (1+ / 0-)
      Recommended by:
      Wee Mama

      For something like:


      of a second.

      At a certain "temperature" space doubles in size.

      It was at that "temperature" for about:


      of a second and doubled about 160 times during that fraction of a second which made it very big.

      It is depressing, but the Universe is going to drift apart and "evaporate".

      What caused that pinpoint of hot space happening again is our only hope.  There are many theories, none yet widely accepted.

      Knock, knock...who is there? -- One more vote for Obama.

      by NCJim on Tue Oct 16, 2012 at 07:15:53 AM PDT

      [ Parent ]

      •  See, I know (1+ / 0-)
        Recommended by:

        I understand that the universe could only stay in that 'pin-point' state for 10*10^mega sec. But it had to be something before that. And something that put it in that state.

        Because if this only happened once, you almost have to go with the god version (not the biblical one though). And I can't go there.

        So I vote cyclical. Can't explain it - can't get away from it.

        Either you're wit' us or a Guinness -- Brilliant!

        by Unforgiven on Tue Oct 16, 2012 at 07:31:58 AM PDT

        [ Parent ]

  •  I get it...I think. (1+ / 0-)
    Recommended by:

    On a related line, is it known why inflation happened, or is it, as my husband likes to say, just one of those things that happens from time to time?

    Is it true? Is it kind? Is it necessary? . . . and respect the dignity of every human being.

    by Wee Mama on Tue Oct 16, 2012 at 07:10:21 AM PDT

  •  Do you have a link to when this story broke? (0+ / 0-)
  •  There is no Dark Energy, or Dark Matter.... (1+ / 0-)
    Recommended by:

    Both are a mathematical construct to try to explain how observed reality fails to comply with a flawed theory.

    There was no "big bang". It was a "big whoosh" and is part of a cycle, on a local level (300-600 billion ly radius) within what is an infinite universe, in both time and distance.

    The "event" of flash-over that is the whoosh, occurs at speeds far in excess of the speed of light.

    The cycle runs from "nothing", where a region reaches ABSOLUTE ZERO and all energy has dissipated and all matter has ceased to exist. Allowing this universe/dimension to collide with a neighboring universe/dimension, the collision of which causes a flash-over to pure energy. This happens on a scale of hundreds of billions of light years instantaneously.

    The energy transitions to matter over time, the matter has gravity and it clumps over time and cools and forms gas clouds, which clump to form stars, which clump to form galaxies, and so on, and so forth.

    As time goes on, the entire region cools and energy dissipates until once again all the stars die and the temperature eventually reaches ABSOLUTE ZERO and matter ceases to exist, and universe/dimensions collide.... rinse, repeat FOREVER.

    The only place in the observable universe that true ABSOLUTE ZERO exists is at the center of a black hole. Where matter is crushed so completely that it mimics matter at the moment of absolute zero, where it ceases to exist.... poof. Black holes eventually evaporate back to visibility.... eventually.

    Hawking's proved it, and when his peer's realized the ramification of what he proved.... that at the boundary conditions matter/energy is NOT conserved, but is in fact destroyed.... they called him a nut, said that he had lost it, and the shame of being ostracized had him off working out all manner of ways to fix the explanation to placate the pinheads, like "oh, there are WHITE HOLES" in some other universe to balance out the BLACK HOLES in our universe, yeah that's the ticket.

    PS: Extra added bonus..... Gravity is the manifestation in our universe of the equal-but-opposite-reaction of the repulsive force between universe/dimensions due to the presence of matter/energy. At absolute zero, energy/matter ceases to exist, nothing pushes them apart, and universe/dimensions collide.... BANG. This is why you can't find gravity in quantum mechanics. It is NOT an attribute of matter, it is a reaction to an outside force as experienced in our universe.

    For the record, "Theory of Everything" copyright 2010, James Allen

  •  I Knew It!!! (0+ / 0-)

    No, seriously, I had no idea.

    Please do not be alarmed. We are about to engage... the nozzle.

    by Terrapin on Tue Oct 16, 2012 at 10:37:03 AM PDT

  •  Trying to understand this: (0+ / 0-)

    So we're mostly empty space. As I understand it the reason we can't walk through walls is because repelling nature of the negatively charged electrons that surround the atoms of our body and the wall.
    Then what accounts for the bruise on my forehead?

    "Whenever I get the urge, I lie down 'til it passes." - Mark Twain on exercise.

    by mkor7 on Tue Oct 16, 2012 at 11:49:42 AM PDT

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