Singularities & Quantum Mechanics

[vlaiv]

59 minutes ago, joe1950 said:

Good explanation Vlaiv. Points I hadn't considered.

I'm thinking, though, that coming to a scientific conclusion, or an acceptable scientific theory that (ex.) the universe is infinite in size or that the density at a singularity is infinite is not possible since neither would be testable. If you can't measure an infinite universe, you could never falsify a theory that it's infinite, I would think.

It's as string theory is but more so. Some say to have empirical data that string theory is an accepted scientific theory would require a nearly impossible technology - from what I understand. Presently, there is no way to test it as a theory. A theory of something infinite would be beyond that, indeed completely impossible to test. So any idea that the universe is infinite, or a singularity has infinite density would remain an untestable idea, with no supporting experimental data.

I may not be clear in my thinking...or my thinking may not be clear! 

Thanks Vlaiv!! 

Not all aspects of theory need to be testable. Theory needs the following to be accepted: Does better job at explaining observations than any other theory including future observations (ie predictions that can be tested) and does not fail on current data. It is general consensus that if two competing theories both have stated properties, one that is simpler and/or more elegant has the upper hand until one of them gives way due to new observations. Therefore there could be "side effect" to theory that we will never be able to test - but if theory is right about everything else there is no reason to dismiss something on grounds that few odd things it predicts cannot be tested. We should all be aware of distinction: theory is there to explain how stuff behaves and why, not what stuff is. So if theory states that universe is infinite and theory works for every case we tried so far, we might as well state: for all intents and purposes from our knowledge so far, we believe that our universe is infinite. Nothing wrong with that.

[joe1950]

True, Andrew.

It's a slippery slope. As with string theory, it doesn't make it a scientific theory even though in principal, had we a large enough collider, tests could be conducted that would yield some evidence of it being valid or no evidence of it being valid.

I would just wonder why, if a physicist tended to believe that the universe is infinite or that the singularity in a black hole has infinite density, what, other than a fitting mathematical model, would they base that belief upon? What experiments or observational data would lead one to that conclusion?

I'm sure the question has been posed numerous times and I'm thinking on the most basics of levels. I hesitate to purchase books on these kinds of topics after reading some of the recent texts that criticized the science of their assertions.

Thank you, Andrew. A good day!

 

Added: Just saw your post Vlaiv. Very good explanation. I see the distinction you emphasize. Thank you also and everyone for taking the time to clarify the issue.

[Islander]

On 3/5/2016 at 23:01, joe1950 said:

Well done, Rudd! That certainly gives one pause (no pun intended). I'm certainly not qualified to critique the idea but I have read several accounts where to the outside observer, the particle would never enter the event horizon. So why wouldn't the same be true from the particles point of view but for the opposite effect of time dilation?

Very compelling. Thank you.

 

*For some reason your final statement puts me in mind of a TV advert here, where a doctor in an operating room is operating on a patient and very professionally and effectively giving orders to his staff at the end of the operation. He finally says, "That should do it, finish up." The lead nurse next to him says something to the effect, "That was absolutely brilliant surgery, Doctor!" He replies, "Oh, I'm not a doctor, but I did stay at a Holiday Inn Express last night."

There are others in the series and they are excellent.

So I have to ask you, Rudd, did you stay at a Holiday Inn Express?

It can be a bit mindboggling getting to grips with why time differs for the observer and the subject and one of the clearest and best explanations I've seen in a long time was given by Brian Cox at the RA to a bunch of celebs - hard physics dressed up as 'The Science of Doctor Who'.  Don't be put off by the title - the physics is solid and based on Einsteinian principles.  There's a copy on YouTube here:

The subject does cross the event horizon, become 'spaghettified' (brilliant term ) and joins the singularity.  For the observer the subject appears to be frozen at the event horizon for all time.

 

[joe1950]

Very informative and entertaining, Islander. I really enjoy Brian Cox and his presentations.

Anything of that nature is difficult to understand since we don't experience it in the 'normal' realm. 

 

I don't know if it happens as you watch YouTube, but I will never enjoy or understand why they are now putting pop-up adverts over the videos! Is nothing spared the constant annoyance and intrusions of these ill-timed messages? Is one expected to click on the pop-up and leave the video? I know they support the sites with income, but really - in the middle of a video? 

Sorry. Had to get that off my chest.

[Tiki]

On ‎3‎/‎6‎/‎2016 at 14:33, Ruud said:

 

.... Maybe the error lies in ignoring that the black hole itself also experiences extreme time dilation so that the probe and the black hole have their clocks running in sync.

Exactly. A free-fall frame's clock (ie. the probe) is momentarily in sync with everything it passes.

[goodricke1]

On 08/03/2016 at 23:10, joe1950 said:

I don't know if it happens as you watch YouTube, but I will never enjoy or understand why they are now putting pop-up adverts over the videos! Is nothing spared the constant annoyance and intrusions of these ill-timed messages? Is one expected to click on the pop-up and leave the video? I know they support the sites with income, but really - in the middle of a video? 

I hear ppl complaining about these adverts, yet I've never seen them myself. I have Adblock, maybe that does the trick.

[joe1950]

My browser has an option to block pop-ups, but it doesn't seem to work on YouTube. I'll have to write an email expressing my displeasure.

I mean, here we are trying to figure out the workings of the universe and our concentration is compromised by "Do you know the seven warning signs of ___________?" 

I'll have to check in to Adblock. Thank you for the info goodricke1.

Sorry folks. Back to the probe falling into the black hole!  

[JB80]

Just curious as to what people with more knowledge than I make of this... http://phys.org/news/2015-02-big-quantum-equation-universe.html

No need for a singularity and it does away with dark energy too. I must admit the papers at the end are a bit out of my depth but find it interesting.

[joe1950]

That is very interesting, Jarrod. And I too would need the Cliff Notes for a fuller understanding.

Personally, and this, of course, shouldn't enter into the evaluation, but not being a scientist I'm allowed some leeway I suppose, eliminating the need for singularities would be a good thing. And if you can get rid of dark energy, all the better.

As I say, I'm a complete outsider and only know what I know from reading several popular books. I just get the sense that some of the postulates... singularities, inflation, dark energy, multiverses, parallel realities and so on are ideas that may explain something else, but are inexplicable themselves!

However, I concede the final outcome, if one is found, to the professionals.