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    Physics Nobel Prize For Einstein’s Greatest Blunder
    By Sascha Vongehr | October 4th 2011 09:40 AM | 18 comments | Print | E-mail | Track Comments
    About Sascha

    Dr. Sascha Vongehr [风洒沙] studied phil/math/chem/phys in Germany, obtained a BSc in theoretical physics (electro-mag) & MSc (stringtheory)...

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    This year’s Nobel Prize in physics goes to Saul Perlmutter, who shares it with Adam Riess and Brian P. Schmidt, all having been vital in the discovery of that the universe’s expansion is speeding up; research that was done during the 1990s.

    Several science bloggers opined that maybe work on quantum entanglement was more deserving, and they have a point, but if the wider impact of scientific issues is at play in the considerations that lead to awarding the Nobel Prize, the decision today was a good one in that regard.



    Saul Perlmutter receiving the Shaw Prize for astronomy in 2006 with Brian Schmidt and Adam Riess.


    The public and even most physicists (!) totally confuse dark energy with dark matter, the first being an established observational fact; only the second one being a perhaps somewhat dubious assumption (read more about this vital distinction in “Dark Energy, Dark Matter, Dark Force: Not Afraid Of The Dark”).


    Now with this Nobel Prize, dark energy, aka the cosmological constant*, aka Einstein’s greatest blunder, aka the accelerating expansion of the universe, has gotten its recognition via a Nobel Prize, once more clearly saying for all to take note:


    The accelerated expansion of the universe (and thus dark energy) is proper science of the highest quality, period!



    Two independent teams - the High-Z Supernova Search Team (headed by Riess) and the Supernova Cosmology Project (Perlmuter) - found that a group of star explosions called Type Ia supernovae were dimmer and therefore farther from Earth than expected.


    The light from more than 50 distant stars that went supernova was investigated and turned out far weaker than expected from gravity theory after Einstein tossed the cosmological constant out. Thus, this research touches on another important issue: That one should be very careful with the among lay-philosophers so popular Occam’s (Ockham’s) razor.


    Occam’s razor states that given two equally powerful theories, the more parsimonious one with less assumptions should be favored. If aspects are hidden, like for example preferred reference frames in relativity, they could be unnecessary assumptions. Occam’s razor is a popular argument and relates to for example Leibniz equivalence, the parsimony of identifying indiscernible states. Occam’s razor is also one of the most misapplied ideas around, especially considering the ever improving ability to discern previously hidden or ‘unnecessary’ aspects.


    Perlmutter, Riess, and Schmidt being awarded the 2006 Shaw Prize in Astronomy.





    Occam’s razor must be sparingly applied in order to avoid cutting important aspects, like the cosmological constant (or dark energy term), that further progress may require again and may get you the Nobel Prize! You don’t want to throw a million bucks away, do you?



    Also important: This discovery was totally unexpected and the researchers thought for a long time that the finding must be a mistake. They were basically just looking into what went wrong (pretty much like the guys with the faster than light neutrinos are doing as we speak, thinking that the data must be a systematic error).



    Perlmutter, Schmidt and Riess were trying for a long while to make the accelerated expansion disappear, but the more they analyzed the data, the surer they became that indeed, the universe will expand ever faster, taking all galaxies away from each other, leaving a totally dark and cold sky.


    So, in conclusion, I am happy about this year’s choice, because people being afraid of the dark is a little pet peeve of mine. If you would like to know more about why the accelerated expansion of the universe and dark energy are not “modern science losing it and going nuts” but instead down to earth physics that just gotten somewhat of a bad name (literally), I tried my best to explain it also here:

    · Not Afraid Of The Dark: Dark Energy As The Ultimate Sisyphus

    ---------------------------
    * Remark: Einsteins cosmological constant was constant of course and thought to just hold the universe stable while the dark energy term may conceivably depend on time and is also larger, so that the universe is not just stable against its own gravity, but actually "blows up". Nevertheless, these are all the same term inside the Einstein equations. The observed accelerated expansion is simply telling us how large that term actually is and perhaps even how it depends on time (with better observations).

    Comments

    Hank
    The folks at KQED/Quest Science Series sent over this video of Saul Permutter so I am embedding it in a comment here, rather than write another article about this.  Nice work!

    Quentin Rowe
    You know, that's the first I've personally heard of a physicist describing the universe as infinite. Seems it's loosing it's taboo status. Great!

    Thanks for the link Hank, very interesting.

    vongehr
    I thought by now almost all physicist do that - at least all those that think eternal inflation is likely, but also those with Milne model special relativistic universes and flat (uncompactified) or open GR solutions and all that.
    Quentin Rowe
    Well, I knew they must be - I've just been surprised that it rarely (in my case not till now) shows up in public forum / popular presentations. Mainstream in other words.

    I asked at a public lecture on cosmology here in Christchurch NZ (2 year ago) what the current consensus was regards to the size of the universe. The lecturer outright avoided answering the question, which struck me as dodgy. Sorry, I can't provide the guys name, but he was visiting from UK is all I remember.
    vongehr
    The lecturer outright avoided answering the question
    Well, there is some crappy public outreach for you, ha ha. What does it tell the public if a physicist's talk is all "look we know so much and are so fine" but the actual interaction is like "I am above caring about what you actually want to know". I wasn't there, but this sounds like the type of outreach that leaves a bad aftertaste.
    Quentin Rowe
    It did, but then I discovered Science2.0 - now I get a science all-you-can-eat buffet!  ;-)
    MikeCrow
    Sascha,
    How does the topology of the Universe (open, closed), give insight into the size of the Universe beyond the CMB?
    Isn't it possible to have an finite Universe (that's still larger than the visible Universe) that's expanding or contracting?
    Never is a long time.
    Rick Ryals
    Yeah, a lot of things are possible if you stick to what we actually know without assuming that the conclusions of incomplete theories haven't been fundamentally distorted by an as yet unidentified flaw.  The fact that the further extension of incomplete theories typically leads to physical absurdities that get worse the farther that they are extended, is, to me at least, a very telling red flag.  Others have thrown all such conservative approaches out the window having achieved partial successes with incomplete theories.

    It is also still possible that we live in a mostly flat spherical k=-1 universe that is expanding at an accelerating rate, depending on whether or not the geometry changing effect of accelerated expansion is somehow being counter-balanced by an equal increase in positive gravitational pressure.
    vongehr
    This is a very difficult topic indeed. First of all, "open" and "closed" often describes the global curvature and not whether it is topologically open or closed. After that, the fun starts. What you want, namely a finite universe, may be something that doesn't actually make sense. Finite I guess means here a finite piece of space that is now, but in curved space-time, such is far from meaningful. Look at the Milne model - it is finite and infinite at the same time. Also in modern eternal chaotic inflation do you have in a sense finite bubbles with however infinite universes inside. For me personally all these issues are anyway beside the point. These are all hang ups about direct realism. All this becomes no more than a consistent theory in terms of modal realism, which is what quantum mechanics tells us is the superior way to think about such issues.
    MikeCrow
    Since your blog was about models of cosmic expansion, that was the open/closed I was referring to in that context. But you're right it could also be the curvature.

    If I followed your series on modal realism, what you describe is, as you zoom in stuff becomes probability, this probability eliminates the need for quantum multi-worlds.

    So no parallel Quantum Universes.

    Our Universe, some blob of Space-Time, within it is a small bubble that's our visible universe, which is bounded by what we see as the cmb.

    Beyond our blob in the bulk, there could be any number of other blob Universes.

    Beyond our visible part of the universe, we only have suggestions of what might actually be there. I think with the z of the cmb being near 1100, and the most distant galaxies having a maximum z~10, there a good likely hood our universe spatially continues beyond the cmb, is the inside of our blob spatially infinite, maybe maybe not, but IMO it's a lot bigger than we can see.

    Then we get around to whether our universe is an open or closed expanding universe, and is it's curvature flat or curved.
    Never is a long time.
    vongehr
    Thanks Hank. Loading darn slow over here. If you like, just embed it into the article.
    The Stand-Up Physicist
    If this unexpected acceleration is written in terms of our own experience with gravity here on Earth, 9.8 m/s2, I believe this acceleration is tiny weanie, something like 10-10g. The scale and masses involved are as big as they can get, but 10-10g sounds darn subtle. I believe Milgrom of MOND fame is one person who points this issue out.
    vongehr
    What is your point? Not sure what measurement you are exactly talking about, but whatever it is, somebody coming from a neutron star that was about to collapse into a black hole may say something similar about your tiny tiny 9.8 m/s2 here. Does that mean all of a sudden we have no gravity on earth or something?
    The Stand-Up Physicist
    This is a size question. There is an an acceleration of the Universe we do not understand. How big is the unexplained acceleration? The unexplained acceleration is something like 10-9 m/s2. This in in the ballpark of the factor a that shows up in MOND. It is my observation that folks who discuss dark matter often do not know this way of describing the issue.
    vongehr
    Still not sure what acceleration exactly you are talking about, but I think it is beside the point. That MOND may describe dark energy in a certain way just proves that it exists once again. And mentioning dark matter I think is again confusing issues. Energy always means a certain term in a theory; matter on the other hand is a hypothesis that has many "strings" attached.
    The Stand-Up Physicist
    Dark energy is a hypothesis. When people discuss the problem dark energy resolves, it appears that good old "meters per second squared" does not appear in the technical literature. Milgrom was the only person I know who has described the acceleration on this graph in terms of meters per second squared. I asked a similar question of someone well read in the dark energy literature at the last Eastern Gravity Meeting, and he also was unable to answer what to me looks like a direct question.
    Halliday
    Doug:

    It is not too difficult to talk about "meters per second squared" within a system like MOND, since it involves a fixed Newtonian space, and separate, universal time.  General Relativity (GR), on the other hand, is decidedly different:  There is no fixed background (except, perhaps, within an Einsteinian aether like formulation); the coordinate system is highly arbitrary (general coordinate transformations, not just linear coordinate transformations such as found in Galilean and Special relativity); there is, in general, no universal time; so trying to define a "meters per second squared" sort of thing is extraordinarily difficult (it can even be truly impossible, just as it is impossible to create a good definition for the energy of the gravitational field, within GR).

    Now, within relatively simple cosmologies, within GR, one can have something akin to "universal time", and one can often relate the rate of separation between objects, within that cosmology, as a function of distance (perpendicular to that "universal time").  However, even with no "dark energy" (or cosmological constant), various cosmologies will have "velocity" like features that will change with time.  So, even without "dark energy", or such, one will have "accelerations" ("meters per second squared").

    Furthermore, since in relativity there is no fundamental distinction between the units of time and the units of space (c being the conversion factor), the units of "meters per second squared" really become simply units of inverse time or inverse distance.  So, since the units of the cosmological constant are inverse squared distance or time, we can consider the cosmological constant to be a squared acceleration like term.

    I wouldn't recommend it, but you could then translate the square root of the absolute value of the cosmological constant into "meters per second squared".  Unfortunately, that really won't tell you much of anything about what it actually means, or the ultimate "shape" of the universe (as illustrated in the diagram you've included in your post).

    Anyway, I hope this helps, at least a little.

    David
    The Stand-Up Physicist
    Hello David:

    Your comments help quite a bit. It explains why meters per second squared is not showing up in the technical literature on the subject at hand. It also makes sense that Milgrom would go through the necessary hoops to calculate a value. He is an expert in a completely different subject (MOND to explain velocity profiles in galaxies), one of whose technical goals is to measure the value a0 in meters per second squared. He applied his physics skills to do the calculation for this cosmological problem. I only heard about Milgrom's 10-10g characterization of dark energy when reading about his work. I did not delve any deeper into his calculations to see what assumptions he needed to make to arrive at that number.

    OK Sascha, I will drop this line of questions :-)
    Doug