Ask a physicist anything. (6)

[Wiccan_Child]

From what I do understand, yes, you are interacting with your computer screen by observing it. Photons of light are being fired/bounced from the screen to your eyes, meaning that the Heisenberg principle applies, and hence so does the Copenhagen interpretation (assuming it's true).

The photons are hitting my eyes, certainly, but how does that constitute a physical interaction between my body and the screen? The process is exactly the same as when I look through my telescope - light is hitting my eyes. But I'm not physically interacting with the stars, not least because they could be long dead by the time I see their light. Similarly, once the photons have left my computer screen, they are completely divorced from the quantum mechanical system that bore them.

If that were the case then an omniscient God would not ever observe the universe, and derive all of knowledge of it from his non-observing omniscience. Do you think that's what's happening?

No, as I don't think God exists at all, omniscient or otherwise .

 

[Chalnoth]

What is that stuff you see on PBS on TV about String Theory, Parallel Universe and so on. Is that really Physics? Do they really learn that stuff if you study Physics at the univeristy?

Well, yes, but the vast majority of physicists don't do stuff like that. By far the majority of physics is strongly observation-driven, with a relatively small number of people working on pure theory like this. Even among theorists, the majority try to work as much as possible with experimentally-testable ideas.

As far as how much you learn about this stuff in physics classes, well, that's going to depend upon what classes you take, what school you go to, and so on. For the most part, these sorts of pure theory ideas are covered little if at all in classes, and when they are covered they are in specialty classes that are completely optional and only offered occasionally. Most of the time physicists that want to learn about these things do so by going directly to the literature and reading scientific papers, as well as attaching themselves to an advisor that is working in the field and can give them direction as to what sorts of things within the field are interesting to learn about.

 

[Chalnoth]

The photons are hitting my eyes, certainly, but how does that constitute a physical interaction between my body and the screen? The process is exactly the same as when I look through my telescope - light is hitting my eyes. But I'm not physically interacting with the stars, not least because they could be long dead by the time I see their light. Similarly, once the photons have left my computer screen, they are completely divorced from the quantum mechanical system that bore them.

Well, I wouldn't go quite that far. The interaction between the photon coming from a distant star and between a photon passing between two electrons right next to each other is, from the view of quantum field theory, exactly the same. The tremendous distance, however, minimizes the quantum effects so much that they can be completely disregarded.

 

[Wiccan_Child]

Well, I wouldn't go quite that far. The interaction between the photon coming from a distant star and between a photon passing between two electrons right next to each other is, from the view of quantum field theory, exactly the same. The tremendous distance, however, minimizes the quantum effects so much that they can be completely disregarded.

Aye, but the interaction is already so small after a few feet that it's practically the same as a few lightyears. For all intents and purposes, I'm no more interacting with my computer screen than I am with a distant star. As you say, since we're not considering two adjacent electrons, quantum weirdness can be disregarded.

 

[mzungu]

Since gravity plays no role at the plank level then physics will continue to entertain various theories such as string and parallel universes theories. The Main problem is G. Once we come to fully understand it then physics will take such a leap ahead that this world will enter the age of "magic becoming reality"!

I can't wait!

 

[Chalnoth]

Since gravity plays no role at the plank level then physics will continue to entertain various theories such as string and parallel universes theories. The Main problem is G. Once we come to fully understand it then physics will take such a leap ahead that this world will enter the age of "magic becoming reality"!

I can't wait!

Huh? I'm sorry, but this post is just wrong.

First of all, gravity certainly plays a role at the planck scale. The difficulty is that in order to say what role that is, we would need a theory of quantum gravity. We have two candidate quantum gravity theories at present (string theory and loop quantum gravity), but don't know which one (if either of them) is correct, so we can't really say what goes on at those scales.

Secondly, in no way, shape, or form will a fuller understanding of quantum gravity lead to "magic becoming reality". We already know all of the basic physics that is in any way relevant to our everyday lives, or is likely to be relevant for the forseeable future. Nearly all advancements in technology moving forward will not take place because of new understanding of fundamental physics, but instead learning to apply the physics we already know in new ways.

 

[mzungu]

Since we have yet to unify gravity with quantum mechanics and general relativity; then suffice it to say our capabilities in physics is restricted to either QM or GR. You cannot be serious when you dismiss the leap physics will take should we unify QM with GR! The possibilities of such a profound advancement will have on our technological capabilities is beyond anything we have today. With a unified theory at hand we can put to practical use such things related to harnessing energy in unimaginable ways all the way to astro-engineering.

When I say Gravity plays no role at the planck scale I mean to say that its role has theoretical effect on QM at present but without a unifying theory its effects have little to no applicable value. Once we understand fully the role it plays then we can unleash the potential this knowledge will give us.

For example: A micro tremor in San Francisco plays no practical role to a seismologist in Beijing simply because seismology has not advance enough to include such micro tremors as an influencing variable. In fact such micro tremors theoretically do play a role as cause and effect worldwide but not at our present level of knowledge!

I could be totally wrong! But anyway I have to go to the Syntagma Square protest now! We have serious economic problems to sort out.

 

[Chalnoth]

Since we have yet to unify gravity with quantum mechanics and general relativity; then suffice it to say our capabilities in physics is restricted to either QM or GR. You cannot be serious when you dismiss the leap physics will take should we unify QM with GR! The possibilities of such a profound advancement will have on our technological capabilities is beyond anything we have today. With a unified theory at hand we can put to practical use such things related to harnessing energy in unimaginable ways all the way to astro-engineering.

Actually, we can be quite sure.

One of the things to keep in mind with our understanding of physics, as with science in general, is that even though there are things that we do not know, there are a lot of things that we do know. And one of those is that the amount of energy required to produce a machine that accesses physics beyond the standard model makes it completely unfeasible to make the use of such a machine economical for any use but learning more about physics beyond the standard model.

I could be totally wrong! But anyway I have to go to the Syntagma Square protest now! We have serious economic problems to sort out.

Well, I do wish you the best there! You guys are having a really difficult time, and it would be nice for those protests to have some positive impact.

 

[mzungu]

Well, I do wish you the best there! You guys are having a really difficult time, and it would be nice for those protests to have some positive impact.

Thank you! 42 days and still going strong! (writing this on my phone). They have thrown so many chemicals at us that it would kill an elephant. But perseverance and non violence keeps us going!

 

[chris4243]

The photons are hitting my eyes, certainly, but how does that constitute a physical interaction between my body and the screen? The process is exactly the same as when I look through my telescope - light is hitting my eyes. But I'm not physically interacting with the stars, not least because they could be long dead by the time I see their light. Similarly, once the photons have left my computer screen, they are completely divorced from the quantum mechanical system that bore them.

What if you observe entangled photons?

 

[Wiccan_Child]

What if you observe entangled photons?

Observing in what sense? By the time the photon reaches my eye, its been absorbed and re-emitted trillions of times, so any entanglement would be long since shattered. Observation in my mind would mean that the photon has been absorped by countless other photons to generate a single action potential, which is then interpreted by my brain as a single speck of light (rather than a multitude of individual photons). So, in either sense of the word, 'observing' an entangled photon is neither problematic nor all that plausable.

 

[razeontherock]

No. An omniscient God can know in advance what decisions we will make, but they are still our decisions to make. That he knows what they are in advance doesn't determine what they're going to be; what determines which decision we make is still up to us, regardless of whether an omniscient being is aware of them.

Heh. There is a thread in which an atheist is trying to prove that Omniscience removes free will Wish I had the link handy to sick you on her

 

[razeontherock]

One day I will look like this man, and I will do science!

Yeah but your flasks still won't look like dilithium crystals (as pictured)

 

[mzungu]

YouTube - ‪New Discovery about the Fabric of Space-Time‬‏

 

[razeontherock]

Surely his omniscience is an inherent trait, not a phenomenological experience?

Hey, who asks the questions in this thread?

I think the question you ask here is valid, and the answer should not be assumed. No recognized revelation of G-d actually says He's omniscient. That term has gotten bandied about a lot, w/o ever really being defined what in the heck they think they're talking about.

The trait of human closure in action does not revelation make.

 

[razeontherock]

They have thrown so many chemicals at us that it would kill an elephant. But perseverance and non violence keeps us going!

Carry on - hope you get 'er done! (Somebody sure needs to) Wish people recognized the gravity of our financial crises over here ...

 

[impblack]

A superconducting solenoid is mounted on a plastic disc that is free to rotate on a frictionless axle. Around the periphery of the disc are embedded small, charged spheres. A constant current initially circulates in the solenoid. The disc is initially at rest. There is a magnetostatic field. At some temperature the current begins to drop toward zero. dB/dt is nonzero as the current drops, and a circulating E field is induced. Each charged ball experiences a tangential electric force. There is a nonzero torque, and the disc begins to rotate. But the problem is that the initial angular momentum is supposedly zero, and hence the final angular momentum should also be zero.

 

[impblack]

BTW, there is no spacetime

 

[impblack]

because it is self-referential

 

[Chalnoth]

A superconducting solenoid is mounted on a plastic disc that is free to rotate on a frictionless axle. Around the periphery of the disc are embedded small, charged spheres. A constant current initially circulates in the solenoid. The disc is initially at rest. There is a magnetostatic field. At some temperature the current begins to drop toward zero. dB/dt is nonzero as the current drops, and a circulating E field is induced. Each charged ball experiences a tangential electric force. There is a nonzero torque, and the disc begins to rotate. But the problem is that the initial angular momentum is supposedly zero, and hence the final angular momentum should also be zero.

If I recall, this sort of problem can be resolved by taking into account the angular momentum of the electromagnetic fields themselves.