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Frank DiMeglio: on 12/26/09 at 22:10pm UTC, wrote Hi Amedeo. How would your essay ideas account for/address the following? ...

NN: on 10/25/09 at 12:01pm UTC, wrote Te author seems to be short of time to respond to the postings here as well...

Frank DiMeglio: on 10/24/09 at 20:48pm UTC, wrote Hi Amedeo. What are your thoughts on the increased...

Peter Jackson: on 10/24/09 at 14:42pm UTC, wrote Hi Amedio Loved the essay, deserved higher rating so gave you one. If...

Amedeo Balbi: on 10/23/09 at 19:11pm UTC, wrote Dear Phil thanks, I am flattered by your comments. As for the point you...

Philip Fellman: on 10/22/09 at 18:26pm UTC, wrote Hello Amedeo: Thank you for an exceptionally well stated and thoughtful...

Amedeo Balbi: on 10/15/09 at 16:29pm UTC, wrote Thank you all for reading and discussing my essay. I really appreciate...


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CATEGORY: What's Ultimately Possible in Physics? Essay Contest (2009) [back]
TOPIC: The limits of cosmology by Amedeo Balbi [refresh]
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Author Amedeo Balbi wrote on Oct. 2, 2009 @ 15:03 GMT
Essay Abstract

What can we know about the universe? I outline a few of the fundamental limitations that are posed to our understanding of the cosmos, such as the existence of horizons, the fact that we occupy a specific place in space and time, the possible presence of dark components, the absence of a reliable physical framework to interpret the behaviour of the very early universe.

Author Bio

Amedeo Balbi is assistant professor in cosmology at the University of Rome `Tor Vergata', Italy. He obtained a PhD from the University of Rome `La Sapienza', working at UC Berkeley on the MAXIMA experiment; currently, he is involved in ESA's Planck satellite mission. He is the author of "The Music of the Big Bang", a non-technical book on cosmology and the cosmic microwave background.

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Narendra Nath wrote on Oct. 4, 2009 @ 09:33 GMT
Dear Amedeo,

i have yet to go through the text of your just posted essay but your abstract has clearly hinted at the problems in physics for the cosmos. May be you find my essay on the forum providing support to your own ideas. may be you grow further on your own ideas and bring us all out of the complexities we may have ourselves created by the physics we have done thus far.There was another essay by me in the last year fqxi essay forum site ' Mysteries of the Universe- some perspectives '.

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Mark Stuckey wrote on Oct. 4, 2009 @ 14:20 GMT
Dear Amedeo,

I enjoyed your essay. One rarely reads of the observational limits and theoretical assumptions which qualify cosmological results in the popular overviews. My astronomy lecture notes include the observational indeterminancy principle in cosmology for that very reason (Michael Heller, Theoretical Foundations of Cosmology, World Scientific Press, Singapore, 1992, pp. 81-82). Along those lines, thanks for providing a recent value for Omega, which I will use to update my notes :-)


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Author Amedeo Balbi wrote on Oct. 4, 2009 @ 19:51 GMT
Dear Narendra,

thanks a lot, I will read your essay(s) with interest.

Dear Mark,

I'm glad you liked my essay, thanks!

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Narendra Nath wrote on Oct. 5, 2009 @ 12:49 GMT
Thanks, Amedeo. i look forward to see you on my site!There are however a few things i wish to point out.

1. The velocity of light is limiting only in the homogeneous space. If the space is inhomogenous, it can well exceed this value.

2. Some time back, on the internet site may be daily galaxy i noted a measurement of c in Australia where they have huge apertures radio telescopes. A distant object about 10 billions away was looked for. The speed of light signal collected from it was measured and it came out to be distictly higher than the accepted value.

3. If aspace vehicle can codense space in front and expand it behind, it can well move with speeds far in excess of c.

4. tachyons have remained thus far only theoretically. Howver, the relativity does not set the limit of speed to be c for objects that are always moving with higher than the value of c. It is the barrier at c that can't be crossed!

About the dark matter/energy i have given some possible perspectives in my essay and have also indicated how the primordial matter got trnsformed into visible and dark matter componnets in the very early universe while in nascent stage on extremely fast evolution, following Big bang.

It is difficult to theorize the close to Big Bang period, as Physics of extreme pressures and temperatures prevalent then is simply not available, nor it can possibly be simulated in machines like HEC accelerators.

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Frank Martin DiMeglio wrote on Oct. 11, 2009 @ 19:15 GMT
Greetings Amedeo. I am reviewing and considering your essay.

You raise various points about the possible existence of "dark matter"/"dark energy", including the contradictions and inconsitencies that relate thereto.

The following is relevant to your essay discussion, as it goes to the core of the inconsistencies/contradictions that you point out. Also, regarding what we can know about our world of experience, there are serious limitations. The world requires and involves man.

The ability of thought to describe or reconfigure sense is ultimately dependent upon the extent to which thought is similar to sense.

Astronomical observations are interactive creations of thought, to a significant extent. Astronomical observations involve a relative detachment, disintegration, and contraction of vision/visual experience as they relate to space, experience, and thought generally. Astronomical observations have significant similarities with dreams. Astronomical observations and dreams involve a narrowing/"telescoping" of vision. The redshift is indicative of increased gravity due to increased transparency/invisibility of space. Consider how the the setting Sun appears at a 90 degree angle in relation to gravity (overhead) -- red and in a transparent sky. Astronomical observations necessarily increase the size of what is seen, or nothing could be seen at all. The red shift is a reduction in energy/brightness; since an object that is farther away, and yet larger/visible, necessarily involves higher gravity.

Now consider the blackness of outer space, the position of red light on the visible light spectrum, and transparent/clear space. Consider this in relation to the black and clear/invisible spaces of the eye. Consider all of this in relation to "dark matter/"dark energy".

I would appreciate it if you would carefully review and rate my essay. It is fourth from the top. Please read my three comments under the essay before commenting. Thanks.

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Anton W.M. Biermans wrote on Oct. 12, 2009 @ 01:34 GMT
‘ … limitations in physics, … the finiteness of the speed of light … ‘

‘ … this also means that we can observe the universe at different epochs (..) thus tracking and reconstructing cosmic history…’

The speed of light isn’t even a velocity but just a number which says how many meters correspond to how many seconds, so you can never travel a greater spacedistance...

view entire post

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Terry Padden wrote on Oct. 12, 2009 @ 08:58 GMT

Your essay provides an excellent insight into the real issues of Cosmology, and makes very clear what some of the limiting factors are.

I think your conclusion is too pessimistic. Based on your essay I think we can conclude that there is no limit to physics as the study of the Universe - because with new data arriving every second/day/epoch we always have a new universe to study.

Your essay is notable for being effectively maths free, but whenever we do formulate theories to explain our (current) universe we need to express them mathematically - even in Cosmology. My essay explores issues resulting from physics's dependence on maths. The views of a Cosmologist may provide me with fresh insights.

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Stee Dufourny wrote on Oct. 13, 2009 @ 09:52 GMT
Hello dear Mr Amedeo Balbi,

Nice to know you .

It's beautiful explaination around some ideas in cosmology .The Inflation ,the relative perception of our past ,the critical points ,the dark energy ,the expansion,the radiations's indeed difficult to encircle the whole due to our limits .We search and always search where are we ,a real topology exists ,inside a finite sphere for me .

I liked your essays ,it's very interesting .I think the essay could insert the thermodynamics and the evolution ,of course in a finite system where the mass is correlated with the curvature ,the pression and the volume too.The time builds sperical systems with codes of centers .This evolution increases the mass ,the density .The cosmological space is relevant in an evolution point of vue,this space too becomes mass perhaps if we consider them like quantum spheres without rotation thus any mass ,the thermodynamic activates the space near gravity centers like cosmological spheres ,stars ,planets ,moons ,asteroids ,BH super BH ....inside a finite sphere.Our datas are often falsed by a bad perception .It exists a specific dynamic ,a specific sequence ,with its specifics numbers and all this unique system evolves towards the perfect balance between spheres .....on the line time .....

Congratulations for your essay

good luck too for the contest,regards


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Steve D wrote on Oct. 13, 2009 @ 10:08 GMT
I d like add something .

To know the real dynamic since the Big Bang for exemple ,even the sequence of time must be corectly analysed .When we see our past ,we must consider an universal axiom it seems to me .Thus imagine the first step an acceleration towards maximum volume,let's consider that like an expansion ,thus a deceleration towards this max after,after the contraction is probable thus an acceleration and a deceleration towards ultim harmony between spheres .

We must consider the real sequence and its variables of volume ,pression ,density ,mass ,temperature,.....and all that in the line time .The mass spherical systems are on specific coded dynamic where all evolves ....the big polarisations in fact .Now of course after 13.7 billions years what is our actual dynamic ,perhaps we are still in expansion perhaps we are already in the contraction ,.....acceleration deceleration ,constants.....

We can know our actual system and where we are going could be well too if we knew where is the center of our Universe and the limit ,probably a pure light ,of our Universe ,like a membran which envelops our sphere and its spheres built by quantum spheres .

Best Regards


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Author Amedeo Balbi wrote on Oct. 15, 2009 @ 16:29 GMT
Thank you all for reading and discussing my essay. I really appreciate that. I do my best trying to keep abreast of new posts, although I am not always able to answer in detail to all your comments because of my time constraints. Keep it up!

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Philip Vos Fellman wrote on Oct. 22, 2009 @ 18:26 GMT
Hello Amedeo:

Thank you for an exceptionally well stated and thoughtful essay. I particularly enjoyed your clear delineation of the fashion in which current cosmological theory is limited by the structure of our theoretical arguments as much as by difficulties of observation in the idiosyncratic or limited cases which we often mistakenly interpret as being naturally generalizable. In this context, I'm curious how you view C.J.S. Clarke's argument that while we cannot, as you also point out in your paper, view the entire universe, in the local view, the primordial singularity appears to be Friedmann, and it may be reasonable to assume that the larger universe would have singularities which are Friedmann or Friedmann-like. I would guess that you would raise the objection that we don't have a scientific basis for making this kind of generalization or extension, but would like to hear you address this point directly.



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Author Amedeo Balbi wrote on Oct. 23, 2009 @ 19:11 GMT
Dear Phil

thanks, I am flattered by your comments.

As for the point you raise, I believe it is fair to say that, if inflation is correct, then the conclusion that each bubble in the larger universe is Friedman-like is basically inescapable (see, e.g., the recent paper by Linde The problem then -- besides the obvious fact that we cannot look beyond the horizon of our bubble -- boils down to: is inflation testable (or falsifiable, if you like) at all?



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Peter Jackson wrote on Oct. 24, 2009 @ 14:42 GMT
Hi Amedio

Loved the essay, deserved higher rating so gave you one.

If you're interested in new horizons and have time do have a look at mine 'Perfect Symmetry'. But the posts may tell you as much as the essay!

Best wishes

Peter Jackson

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Frank Martin DiMeglio wrote on Oct. 24, 2009 @ 20:48 GMT
Hi Amedeo.

What are your thoughts on the increased transparency/invisibility of space in astronomical/telescopic observations?

Please see, and rely to, my prior post as well. Thanks.

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NN wrote on Oct. 25, 2009 @ 12:01 GMT
Te author seems to be short of time to respond to the postings here as well the desire to visit other essay sites promised. Perhaps, time is in short supply relative to space for present day humans. May be we physicists need to have a relook at these important concepts we have developed painstakingly!

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Frank Martin DiMeglio wrote on Dec. 26, 2009 @ 22:10 GMT
Hi Amedeo. How would your essay ideas account for/address the following?

This goes to the core of cosmology.

The increased invisibility/transparency of space is a requirement of these astronomical/telescopic observations. Importantly, there is a "telescoping"/narrowing of vision in dreams too. (Dreams make thought more like sensory experience in general, including gravity and electromagnetism/light.)Astronomical/telescopic observations have significant similarities with dream vision. Dream vision is constantly active/shifting/variable. Similarly, telescopic/astronomical observations are "activating " what would otherwise be the [basically] unmoving stars at night (as seen by the unaided eye). Astronomical/telescopic observations are interactive creations of thought to a significant extent. Red borders black and transparent. Supernovas and the red sun both only last so long, as well. Witness the clear space around the red [larger] setting sun. Telescopes are known to function as a sort of "big eye". Note the clear and black parts of the eye. Astronomical/telescopic observations make objects larger, or they could not be seen. Yet they are in a smaller space, and dreams are in/involve a smaller space. The earth may also be considered to be in a smaller (and transparent) space. THINK! Dreams involve how a larger space is made smaller, and also how a smaller space is made larger.

Essay Author Frank Martin DiMeglio

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