Science a GoGo's Home Page Forums General Discussion Physics Forum Does Time Exist

The impression I had from reading Bell’s article, and from wading through Yourgrau’s disappointing book, was that Godel was saying that relativity permitted past directed time travel, via CTCs, but in a universe with CTCs time could not exist.

This struck me as being a bit unsatisfactory, and I wondered if others shared the same impression.

Remember Godel was trying to prove Relativity/Einstein wrong that was the whole point of his work

What he showed was that Einsteins equation allowed CTC's .. we agree even today.
That the presence of CTC's basically renders relativity unworkable ... we agree even today.
Godel noted his model wasn't a model of our universe ... we agree even today

What you are forgetting is we have more than relativity, we have QM ... and CTC's are completely incompatible with QM.

Ok I am going to have work up a complete proof for you this one isn't easily covered in layman media.

Wikipedia bluntly sucks and is out of date: https://en.wikipedia.org/wiki/Closed_timelike_curve

They sort of agree CTC's and QM don't mix but not forcefully.

The most recent semi-believable paper I know of on the subject is
http://phys.org/news/2013-02-spacetime-violate-heisenberg-uncertainty-principle.html

You will note they discuss all the background on how CTC's are incompatible with QM and how they were playing with special versions called OTC's to reignite the debate.


Science media actually accurately got current status correct .. someone did there homework.

I ignored the paper because what they don't discuss is you would need to rewrite half of QM for all that to be true. In the article they describe it as extending QM

I mean it only violates HUP, the no cloning principle and then even better they have things called "dispersion-free states" in which all observables vanish but that state can't even be described in QM. Hey this is a really good theory so far I was just waiting for the pink unicorn's to dance on in.

Thanks Orac. the Phys.org article is something I must make time to read. So far I've read the first two paragraphs, and have found the answer to the next question I was going to ask you.

You say is semi-believable, so I guess I'll be looking for guidance as to which bits to "believe".

Let’s start with the illustration. To my untutored eye the difference between CTCs and OTCs is that someone has arbitrarily decided one should involve interaction with a past self, and the other shouldn’t. I’m sure there must be more to it than that. Have I missed it, or is it not demonstrated?

Nope you got it correct if you travel backwards in time for like to interact with yourself, you enter a different universe. So implicit in the OTC is a multiverse like Everett form. That is the sense it is open and discrete from a CTC where you come back to this universe.

I think all you missed is OTC's require a multiverse.

I was wondering why I didn't pick that up but they said "Deutsch model's" so I knew straight away what they were doing.

Ok that took some finding strangely it isn't under his name entry in wikipedia but it is here
https://en.wikipedia.org/wiki/Quantum_mechanics_of_time_travel

Read the section "Deutsch's prescription"

Strange place to put it and I left a note with wiki.

It surprises me that so many people seem to assume that skipping into into another universe solves problems like the "grandfather paradox". The more you think about it, the less likely a solution becomes; unless you can put people into a superposition of states.

I have no issue with people being put into superposition state that will likely be tested and shown to be true in the far future. As I commented a bacteria will be the first "living organism" to have it done to them and there are groups lining up to try just send money.

http://phys.org/news/2015-09-pair-superposition-state.html

The problem with MWI is it just fails badly and all MWI proponents do is lots of handwaving. The problems are listed and discussed here under common objections
https://en.wikipedia.org/wiki/Many-worlds_interpretation

Unless MWI can give answers to the problems it is little better than witchcraft and certainly isn't science.

http://phys.org/news/2015-09-pair-superposition-state.html#jCp




Should one distinguish between quantum states and physical locations?

http://phys.org/news/2015-09-pair-superposition-state.html#jCp




Should one distinguish between quantum states and physical locations?

I’m having a job to get my head round what is going to happen here. At the moment it seems like they are going to conduct an experiment on an organism frozen to close to 0K, which may, or may not, survive. After which they will assure everyone that at some point in the experiment, which no one can observe, the unfortunate creature was both dead and alive (or was that in two physical locations?) at the same time.

We would do it with you if we could but your cells definitely won't survive

They only need to do the experiment at near 0K to get rid of the noise so they can get a defined QM measurement, it plays no other roll in the test. Wheeler's delayed choice experiment itself can be done at any temperature but it's hard to measure QM statistics on a macro object without control of temperature.


You sort of miss the point play terrorist with the lifeform stick a bomb on it detonated by radio control. If a self interference pattern exists the lifeform lives, if not it gets blown up.

Now look at the quantum eraser and work out when your lifeform lives or dies and when his fate was decided

refresher: https://www.youtube.com/watch?v=SzAQ36b9dzs

I have given you a physical meaning cats who go thru both slits live, cats who go thru a single slit die. Any experimental implication can have a real world physical implication.

The reason the lifeform is important is not for any of this but a thought experiment called Wigner's friend (https://en.wikipedia.org/wiki/Wigner's_friend).

Specifically what it is probing is the role of a conscious observer if any.

https://www.youtube.com/watch?v=SzAQ36b9dzs

Thanks, that was a great link. It' has already improved my understanding of quantum erasers, and I'm going to have to see it again, before commenting.

Remember the point is not what you "see", you can never see the cat thru both slits it is that time elapses after the slits and many things can happen in that time. Then some time later you can do something that dictates which slot the cat went thru and that time can be billions of years.

The best layman version I know of is
http://www.bottomlayer.com/bottom/basic_delayed_choice.htm

The problem is zone 3 which could be any event and 13 billion years old and increasing

http://www.bottomlayer.com/bottom/basic_delayed_choice.htm

Interesting link.

You are well aware of my crackpot thoughts about infinity/eternity, and you may well recall my suggesting that QM gives us a “window” into infinity.

Let’s take the crackpottery a step further, and "test it experimentally".

The cosmos is infinite, there is no change or time, nor is it possible to differentiate in terms of location. To say that everything is here and now is probably as close as we can get with our terminology.

Our Universe, which is a shadow of the cosmos, is characterised by space, time and progression, otherwise it would not be possible for us to maintain intelligent existence.

In the reality of the cosmos our double slit experiment exists in a static state in which (what we perceive as) a photon, or other particle, exists timelessly in every part of the set-up (and everywhere else).

Because, in our Universe, the experiment is carried out in linear time we are unable to see the complete picture, so we interpret different aspects of the experiment as demonstrating different outcomes.

In the same way that multiverse theories maintain that conflicting outcomes are all realised in different universes; an infinite cosmos theory, if there were such a thing, might suggest that what we perceive as different outcomes are all realised, eternally and changelessly, in the cosmos. Classical physical experiments cannot display the underlying reality, but QM can, and does.

Can I come back to this one you have a lot of different themes running and I would like to see your answer on others first.

I have some problems with this idea but I and science in general don't have an answer either so don't get concerned. You are in good company

All I am really doing is connecting your answers up in a first principles method and see what problems fallout in your idea.