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CraigS
04-11-2010, 02:14 PM
Ok.

I've held off on this one for a long time, because it doesn't matter how many times I read up on it I still don't get it. So perhaps someone else could explain it ??

In the News a particle astrophysicist is attempting to design an experiment at Fermilab (http://www.symmetrymagazine.org/breaking/2010/10/20/fermilab-scientists-to-test-hypothesis-of-holographic-universe/), (no less), to prove that we don't live in a Holgraphic Universe.

(Which is probably good, seeing as I haven't the foggiest on how they came up with this one).

Have fun.

Cheers

snas
04-11-2010, 03:18 PM
If the Universe is a hologram, just call me Arnold Rimmer.

Stuart

CraigS
04-11-2010, 03:52 PM
Ok Stuart .. er 'Arnold' .. you can call me EMH (http://en.wikipedia.org/wiki/The_Doctor_(Star_Trek))
:)

but seriously, this gizmo wil be extraordinarily accurate:

"The holometer will be seven orders of magnitude more precise than any atomic clock in existence over very short time intervals."

that's more accurate than a millisecond pulsar !!

;)

What I don't get is how they can interpret 'spacetime jitter' as 'holographic noise'. Is there a difference between the two ? How can you falsify a hologram hypothesis by measuring jitter of 1 MHz ??

This one loses me, folks !

Cheers

Steffen
04-11-2010, 04:21 PM
A hologram, eh?

"Ah-ha-ha-ha-ha, you think this is the real Quaid? Ha-ha-ha!" rat-tat-tat-tat-tat "...it is!"

Cheers
Steffen.

CraigS
04-11-2010, 04:32 PM
This guy, "Craig J Hogan" (the scientist referred to), is no slouch.

Just looking, he's published 21 papers leading up to this in arXiv.

The holographic theory has been around for a long while.

Leonard Susskind and even Hawking have been involved in it.

Seems to have to do with information theory.

Its a serious quantum mechanical/string theory concept, folks !

Cheers
PS: His detector is very much like LISA to detect gravitational waves. The two concepts are linked somehow.
PPS: Having said all that, I still don't get it !!

Robh
04-11-2010, 07:25 PM
An article I remembered from last year does a better job of explaining the idea.
http://www.sciencedaily.com/releases/2009/02/090203130708.htm

Regards, Rob

CraigS
04-11-2010, 07:46 PM
Yes .. thanks for that Rob. Much appreciated.

I can see that this guy (Hogan) has been thinking about this for a long time. The theory behind it sounds very heavy. I still can't see how the planck scale vibrations are linked to a holographic universe. This would seem to be tied up with String Theory mathematics. I'll keep reading and looking. It seems my answers may not come without a lot of effort on my part, so it could be sometime before the penny drops for me. Oh, well .. we all have our barriers .. looks like I just met up with one of mine !
:)
Thanks kindly for your help .. (I AM a step closer having read it. Need some thinking time, now).

Cheers & Rgds.
PS: Hey .. one of the guys commenting on Hogan's approach in your article is 'Bernard Schutz' .. the same guy who wrote Bojan's book in the 'Relativity and Pressure' thread !

Robh
04-11-2010, 09:19 PM
Craig, this is my interpretation from my limited knowledge ...

The holographic principle basically states that the information contained within a volume can be thought of as being encoded on its boundary. Thus, a 3D holographic image is formed by information via lasers at it's boundary. The description of all objects that have fallen into a black hole is contained within its event horizon. The description of the mass within the Universe is somehow inscribed on the surface of its boundary. In a given volume, there is an upper limit to the density of information it contains, so that matter cannot be subdivided infinitely many times i.e. there must be an ultimate level of fundamental particles which are bits (1 or 0) of information. The Planck scale vibrations you mentioned are indications of the bits or pixels of the Universe big picture- "the graininess of space and time".

Regards, Rob

avandonk
05-11-2010, 10:17 AM
It sounds like information mapping to me. All a hologram is, is a two dimensional recording of a three dimensional object by incorporating phase information of the waves (coherent laser light) reflected from an object and interfered with a reference beam so that when the reference beam is modulated by the recording media you recreate an image of the original object in three dimensions. This is NOT the original object but a mere representation of it.

As all matter is just wave functions before they are observed and then collapse to a localised reality I cannot see what the problem is.

Reality is just self referential waves that we perceive as reality.

All your perceptions are just signals interpreted by your brain that originate in your senses. Your senses were stimulated by signals 'outside' yourself.

Where do you really begin and end?

Does reality have no strings attached?

Bert

CraigS
05-11-2010, 11:11 AM
Ok. Before we get into the philosophical side of it (which IS very interesting .. but should we follow CraigS' Law: That philosophy at IIS always comes at the end of an IIS thread ?.. :) )

So, following on from Rob's message, I've reverted to Susskind to fill in some gaps:



the last statement is reassuring for me.

.. a big quote but I'm starting to get it.

The bits I've underlined would seem to relate it all to looking for planckian sized vibrations. One big question left is: Why should we assume its all imposed from a boundary condition ? Or is this just the paradigm of the thought experiment ? Once again Susskind says:



I'll have to read on to find out what the far reaching conclusion is. Hopefully, it'll be some kind of prediction .. presumably what Hogan is now testing !
Thanks for the help, everyone .. I'm getting there (I think).

Cheers

CraigS
06-11-2010, 04:34 PM
Ok .. so ..

Hubble's Law:

So, if you look out far enough in an expanding universe, you come to a point where the galaxies are moving from you at the speed of light. Amazingly, the distance to that point never changes!
So, at a distance of ~15 billion light years, things are moving away at the speed of light, BUT also, it will always be that way, for all time!!
In every direction, galaxies move beyond the point where they recede faster than the speed of light. We are thus surrounded by a 'Cosmic Horizon'. No signals can ever reach us from beyond that horizon.

Its just like we live inside a black hole !

Apparently, the mathematics of cosmic horizons are similar to those of black holes !!

Just as black holes radiate (and allow information to escape), so do cosmic horizons. However, their radiation, (or information bits), is inward .. not outward .. and that's where the hologram bit comes in !!

Amazing ! .. Formally, this would be called the "Cosmic Principle of Complementarity"



I think I get it, now. Absolutely amazing !! Very cool. I think I'm just about done !!

Comments welcome .. am I loosin' it ?
:)
Cheers

Robh
06-11-2010, 11:44 PM
The whole concept is amazing!
The Universe is comprised of both separate and overlapping bubbles, each bounded by their own cosmic event horizon. Our perception of the whole Universe is confined to the sample of our own bubble universe. Intelligent life in exclusive bubble universes have no known communication line.
Effectively, we have become the centre of our own observable universe. As expansion continues and more galaxies cross the boundary of the cosmic event horizon, we will eventually end up living in a rather empty bubble.
If the cosmic event horizon is the boundary of our holographic universe, this of course means we have ever-decreasing mass in our bubble and the boundary encoding needs less memory space. So, is our bubble universe becoming more grainy with time?

Regards, Rob

CraigS
07-11-2010, 07:57 AM
Hi Rob;

Boy, this is tricky. From our perspective, it seems that as galaxies move closer to the horizon, they are heated and radiate back as photons. As they cross the horizon, they don't notice anything. We must notice the photon radiation, (being directed inwards, as they pass the horizon) and it must be equal to the radiation of the escaping galaxy. It would take 15 billion years for us to notice it, though.

What do we notice after they've gone ?
Whether the escaped galaxy is real, and how they fit into our description of the universe, has got to be unknown to us. what they left behind when they departed must linger because information is never lost (this is the laws of entropy in action).

In short, I'm not sure how would effect the graininess (??).

Cheers

CraigS
07-11-2010, 08:06 AM
Back to some humour .. this one's getting way heavy (again)

Armed with this new knowledge, I intrepidly decided to wade into the Hogan paper, foolishly thinking I might actually be able to begin to comprehend the Abstract at least !! He's the first paragraph: .



:lol::lol::rofl::rofl:

Need I say more ???
(Looks like something you'd see on that snarXiv (http://snarxiv.org/vs-arxiv/) ( a test for those who think they possess PhD levels of scientific knowledge !!)

I'm glad Hogan knows what he's doing .. I wonder how many others do ?

Cheers

cwjohn
07-11-2010, 04:08 PM
Firstly, the cosmic event horizon as you have named it is not 14 billion years. It is much larger than that as clearly demonstrated in the paper by Lineweaver and Davis.

Secondly, for a moving observer this horizon would move with them, so it would not be possible that an observer pass through this horizon. They could pass through the cosmic event horizon of an observer on earth, but this would be of no significance whatsoever.

The comparison to a black hole is like comparing apples and oranges. Completely different phenomena and completely different math.

As to the proposed experiment is it any wonder that congress is reducing funding to astronomy with this sort of nonsense taking place.

Chris

adman
07-11-2010, 07:03 PM
as galaxies pass through our own cosmic horizon and go over to the 'other side' - should we be able to observe this process. Shouldn't we be able to see galaxies in the throes of disappearing from our bubble?

Shano592
07-11-2010, 09:32 PM
No, just call ME Arnold Rimmer ... or Iron Balls, if you like. Or just plain old Ace will be fine.

cwjohn
08-11-2010, 07:24 AM
Through gravitation attraction the galaxy will tend to all move at the same speed. Expansion of space will result in the galaxy moving at c relative to our timeframe at sometime in the future, thus when the photons reach us it should appear as if the entire galaxy blinks out. Of course it will be many tens of billions of years until those photons reach us, so dont hold your breath that you will see galaxies disappearing any time soon.

CraigS
08-11-2010, 11:19 AM
Chris;

Some comments follow:



Lineweaver and Davis: “Expanding Confusion: Common Misconceptions of Cosmological Horizons and the superluminal Expansion of the Universe”, (accepted, 2003, October), paper, provides a finer detail of definition of the term ‘Cosmic Horizon’. They introduce the concept of the ‘Hubble Sphere’, the ‘Particle Horizon’ and they apply these to recessional velocites from Proper and Comoving Distance perspectives. I have no problems with adding more clarity to the definition of the ~15 billion light years I mention in my post, and refining it further, with their additions. (Ie: the ~15 billion was an estimate cited for the purposes of introducing the concept).



.. as I mentioned in post #11.



It would be of no significance to the observer on the galaxy moving through the earth observer’s cosmic horizon. But the earth bound observer would most likely observe many effects as the velocity difference approaches, and exceeds, c. This topic is still hotly debated by many theorists today. I am not one of those theorists, so its not worth debating here.



“The properties of cosmic horizons seem to be very similar to those of black holes. The mathematics of an accelerating, (exponentially expanding), universe imply that as things approach the cosmic horizon, we see them slow down … If we could send a thermometer attached to the end of a long cable, to the vicinity of the cosmic horizon, we would also discover that the temperature increases eventually approaching the infinite temperature at the horizon of a black hole … But our own (earth bound) observations, supplemented with some mathematical analysis, would indicate that they are approaching a region of incredible temperature.”

- Leonard Susskind, “The Black Hole War” , (page 439), originally published July 2008. (He’s spent a career on this stuff).

He goes on to say, from a theoretical perspective, there are other effects observed from the earth frame of reference. He says these depend on the theoretical flavour you choose .. Quantum Field Theory or String Theory.



An opinion ? .. that’s Ok .. I have ‘em too. I think its worthwhile. IMHO, regardless of the finding, the prospects of falsification or confirmation always justify the effort.

Cheers

CraigS
08-11-2010, 11:23 AM
Could you please explain this ? (I'm not sure I understand where you're coming from).



Interestingly, we already see many galaxies moving at, or greater, than c. The fastest observed so far is UDFy-38135539 z = 8.55, discovered in 2010, it is the most remote object known.
It has been calculated, (as of October 2010), to have a light travel time of 13 billion years, with a present comoving distance of around 30 billion light-years. The galaxy is thus the most distant object yet identified in the universe. It may be possible to observe galaxies up to redshift of 10 with the current generation of telescopes.

(A generally accepted cosmo model shows that galaxies beyond a redshift of z=1.46, recede faster than c).



As I mentioned in my previous post, the things we should see is still up for debate amongst theorists. I’d like to keep my mind open about this one. Especially as the technology isn’t ready yet to confirm it, one way or the other.

For example, UDFy-38135539 presently looks like a ‘smudge’ (http://en.wikipedia.org/wiki/File:UDFy-38135539.jpg).

… Interesting stuff ..

Cheers
PS: The CMBR is z~1100. The recessional velocity is 3.2c. At the time of CMBR emission, the recessional velocity was 58.1c (there are some model assumptions in these figures). [Reference: Lineweaver and Davis]
Also, looks like the James Webb telescope should be able to detect galaxies more than 13.4 billion light years away (Wiki).

Brian W
08-11-2010, 07:20 PM
I just figured out it is not possible to find the centre of the universe for lots of reasons not the least of which is that the centre expanded with everything else so in one way we are all in the centre due to expansion and now you all lay this before... this may take a wee bit of thought.
Brian

CraigS
09-11-2010, 07:00 AM
G'Day Brian;

I think its all still fairly consistent with our previous discussions (?)
(I hope so, at least) . :)

The key here, is to separate the 'Observable Universe' from 'The (total) Universe'. The 'boundary' of the Observable Universe is a 'Cosmic Horizon', (which can be more accurately defined by a Hubble Sphere and a Particle horizon). These are then analogous to a black hole's Event Horizon which is used to predict the behaviour of things furthest away from us (moving at or greater than speed of light).

The hologram bit is where it gets complicated because this shifts into an Information Model paradigm, and it is definitely non-intuitive.

Have fun.

Cheers

cwjohn
09-11-2010, 07:23 AM
CraigS

Some brief comments.

I have the greatest of admiration for Leonard Susskind, expecially as a gifted writer and lecturer, but clearly he is not afraid to let his imagination run a little wild as Woit and Smolin have pointed out in their respective books. Let us remember that these theories are based on assumption after assumption with no prospect of verifiability and thus by any basic analysis no longer qualify as scientific. This is not to say they are not valuable and thought provoking, and one may, after some considerable contemplation accept them as likely or not, but they need to be put in a separate class to what we would call normal scientific discourse.

I would disagree strongly that the prospects of falsification or confirmation always justify the effort. This argument could be used to justify any research on any matter irrespective of ethics, cost or just plain triviality. There is only a certain amount or resource available and that resource needs to be allocated on merit.

In regard to velocities I think you know well I was not referring to recessional velocity this being a property of the received redshifted photons. It is misleading to say "We see many galaxies moving at, or greater than c as this is a comoving velocity relative to our reference frame. Yes, they are theoretically receding from us at greater than c mainly due to the expansion of space, but the velocity that they are actually moving at would be a matter of some debate depending on your reference frame.

CraigS
09-11-2010, 12:47 PM
Chris;
Interesting comments and thank you for them.
A couple of my own follow:


Susskind was a big party-goer from the seventies, I believe !
The battle between Susskind and Smolin/Woit kind of ended up as a stalement, I think (?).


I would see this as a bit of an over simplification. Theoretical assumptions (of the type we're discussing usually have a sound basis of foundation).
Whilst String Theory may not be directly verifiable at present, the predicted effects and behaviour of strings may, (or may not), be observed in other, (perhaps), unrelated phenomena. Knocking it all on the head, one way or another would seem to be a good idea, (if it is at all achievable).

Whether these matters are scientific or not, is a philosophical/intellectual debate. No one wins in these.



Aha .. I agree we need another name for it all ! :)
I would say they have value because they are highly logical and have a very high degree of internal integrity. To me, this demonstrates the quality of what they have to say.



That's cool .. I agree that's a complex issue ... I'll leave all that up to governments who make the funding decisions. Looks like Hogan succeeded in convincing someone !



Actually, no .. I didn't understand where exactly you were coming from. I guessed you were coming from metric expansion of space. I guess if we're dancing around these concepts, we should be clearer about the orientation when we shift from a mainstream, scientific concensus view.

Its all very interesting.
We have many folk who drop in here in the Science Forum and I think I'd have to say, that very few have a common perspectives on all these matters. Some folk completely reject Metric Expansion, some believe gravity is communicated by 'push' particles, some believe plasma is responsible for Pulsars, Quasars, Neutron Stars and that Black Holes have no place in their thoughts. These conversations usually result in frustration due to a break down in logical discussion flows.

The mainstream consensus perspective has a high degree of interconnecting logic, which is why I attempt to steer conversations towards these perspectives, as a common basis from where to go in those conversations.

I agree with what seems to be your stance, (if you'll allow me to paraphrase .. correct me if I'm overstepping the mark here, just trying to get where you're coming from so I don't tread on any (more) toes)
"Don't believe any of it .. but do attempt to understand it"

(Oh well .. at least that's my view on it all).
:)
Cheers (& thanks for your conversation).

avandonk
09-11-2010, 02:23 PM
Can someone explain to me what the term holographic universe means as I think it is another cop out as to our fleeting reality.

So far I have seen pathetic attempts at Plank noise to explain the "WHAT".

It is drivel as then our reality is just moved to a projector!

Bert

CraigS
09-11-2010, 03:18 PM
Bert;
My best efforts are on posts #10 and #11.

Seems to me its just a different way to envisage our universe (and thus explain our reality). It seems the term is formally "The Holographic Principle" as distinct from the term you use: 'Holographic Universe' (I'm not sure what this is).

IF we picture the observable universe as information bits on our Hubble or Particle Horizons, then we can explain some observations of the behaviour of Galaxies, matter, etc it/they approach this 'boundary' or 'horizon' (or holographic 'film').
The mathematics of Event Horizons (String Theory) around black holes can be used to describe this.

I'm not at the point of understanding of how it may be used to explain our 'reality'. Maybe that's not what the Holographic Principle is about at all (ie: perhaps the title of this thread is a misconception on my part .. I didn't understand any of it when I started the thread).

Happy to hear from others on this bit.

Cheers
PS: The bits radiate 'inwards' (via the Hawking Radiation descriptions/mechanisms). I think this explains the 'projector' bit (?)

cwjohn
09-11-2010, 04:51 PM
Just so - paraphrased perfectly.

As a side issue I see a researcher has just received an ARC grant for $26 million to verify the feelings of those suffering the plague 500 years ago. This amply illustrates my point that falsification and / or verfication is not the only necessary precondition for funding with our hard earned tax dollars.

Cheers

avandonk
09-11-2010, 06:16 PM
How many of you have seen a hologram in a real laser laboratory?

Let alone a full colour one.

Thought so.

Bert

CraigS
09-11-2010, 06:43 PM
Gee Bert;

I've seen a hologram.

And it looks nothing like our reality.

Does that mean I should trash the whole concept, forget about the whole thing and not bother to try and understand where these guys are coming from?

If I did that, I'd never learn anything !

Cheers

avandonk
09-11-2010, 06:58 PM
OK before you postulate reality is a hologram even if it is a three dimensional projection. The projector has no control over the image.

Who is the projector! God?

Some wanker discovers Plank noise and Quantum Mechanics and he has orgasmic prophesies.

The whole trick with reality as I have explained before is that it is totally self referential.

Bert

CraigS
09-11-2010, 07:26 PM
Ok .. I'm not sure that these guys are trying to get tied up in an implied relationship between reality and a hologram. (Neither am I).

It seems to be more like a thought experiment .. a model.

They may learn more about QFT and String Theory, by doing the experiment that Hogan's on about.

It looks more like a gravity wave detector to me.

:)
Cheers

avandonk
11-11-2010, 10:17 PM
A gravity wave detector needs two arms in the order of a few kilometers long. The whole device would need to be kept at very low constant temperatures.
We are looking for about a differential of a very small part of a nucleus of an atom. A very big ask!
Interferometry is good but not that good yet!

Bert

CraigS
12-11-2010, 06:40 AM
Ok .. just re-read the original news articles.
It appears all this started because of an unaccountable noise phenomenon in the GEO600 gravity wave detector in Germany. Enter Hogan


Evidence (?) maybe until someone else comes up with a better hypothesis.
;):)
This is totally reminiscent of Penzias and Wilson stumbling across the CMBR. I guess we'll see how it all pans out. Should be working sometime next year.

Cheers