Free planetarium

 
User avatar
DoctorOfSpace
World Builder
World Builder
Posts: 852
Joined: 22 Aug 2016
Location: SpaceX Mars Colony
Contact:

Science and Astronomy Videos

15 Sep 2017 18:09

A-L-E-X, I am rather fond of pilot wave :(

When I view the large scale structures of reality it tells me everything is determined, if the large scale is determined then the quantum scale must be too.  The hints at indeterminism are probably a lack of precise methods of measurement or a misunderstanding of the phenomena.
CPU: Intel Core i7-5820K 4.2GHz 6-Core Processor - RAM: G.Skill Ripjaws V Series 32GB (4 x 8GB) DDR4-2400 - GPU: EVGA GeForce GTX 1080 Ti SC Black Edition
Quando omni flunkus, moritati
 
A-L-E-X
World Builder
World Builder
Posts: 804
Joined: 06 Mar 2017

Science and Astronomy Videos

16 Sep 2017 01:19

Oh I forgot about that one, Doc!  I wanted to look into it more.  I'm in Deutsch's email group, which is why that one came to mind easily.  I heard about pilot wave theory and was intrigued by it but never really investigated it indepth.

Gah- what you said basically underpins the way I view the universe.  Superdeterminism is another name for it.  Basically, the past, present and future all coexist as if on a landscape of time and we journey through it, unaware that time is just like the other three dimensions we know about.  It gets rid of all the paradoxes associated with QM.  Even if there are other timelines, like MWI, they all existed from the beginning of the current cycle of the universe and will collapse back into one at the end of the cycle.
 
User avatar
Watsisname
Science Officer
Science Officer
Posts: 884
Joined: 06 Sep 2016
Location: Bellingham, WA

Science and Astronomy Videos

16 Sep 2017 08:55

A-L-E-X wrote:
Source of the post Basically, the past, present and future all coexist as if on a landscape of time and we journey through it, unaware that time is just like the other three dimensions we know about.

Relativity raises trouble with this idea though, because what events are in the past and what are in the future are not absolute, but rather depend on one's state of motion (the relativity of simultaneity).

Pilot wave theory is one of the ideas that sounds really good and conceptually explains some things like double slit interference, but as far as I'm aware it hasn't reproduced all the precise mathematical predictions of QM.
 
User avatar
DoctorOfSpace
World Builder
World Builder
Posts: 852
Joined: 22 Aug 2016
Location: SpaceX Mars Colony
Contact:

Science and Astronomy Videos

16 Sep 2017 11:36

Watsisname wrote:
Source of the post Relativity raises trouble with this idea though, because what events are in the past and what are in the future are not absolute, but rather depend on one's state of motion (the relativity of simultaneity).

Doesn't it also pretty clearly say that all of time must exist as all of space exists since the two are really one?  If that is the case, then what I am going to eat in 10 years already exists.
CPU: Intel Core i7-5820K 4.2GHz 6-Core Processor - RAM: G.Skill Ripjaws V Series 32GB (4 x 8GB) DDR4-2400 - GPU: EVGA GeForce GTX 1080 Ti SC Black Edition
Quando omni flunkus, moritati
 
User avatar
Watsisname
Science Officer
Science Officer
Posts: 884
Joined: 06 Sep 2016
Location: Bellingham, WA

Science and Astronomy Videos

16 Sep 2017 11:54

It exists, but different observers may disagree whether one event precedes or follows another event, if they are separated more in space than in time.  Time is not a fixed landscape that we pass through in an absolute sense.  The slice of "now" that separates past from future depends on how you are moving.
 
User avatar
DoctorOfSpace
World Builder
World Builder
Posts: 852
Joined: 22 Aug 2016
Location: SpaceX Mars Colony
Contact:

Science and Astronomy Videos

16 Sep 2017 12:53

Watsisname, that sorta sidesteps the question.  Maybe my understanding is wrong, but that seems to suggest to me that an observer elsewhere may have their "present" be my tomorrow, and my today is their yesterday, in which case my tomorrow must exist.

So would that invalidate what I said about all points in time already existing?
CPU: Intel Core i7-5820K 4.2GHz 6-Core Processor - RAM: G.Skill Ripjaws V Series 32GB (4 x 8GB) DDR4-2400 - GPU: EVGA GeForce GTX 1080 Ti SC Black Edition
Quando omni flunkus, moritati
 
User avatar
Watsisname
Science Officer
Science Officer
Posts: 884
Joined: 06 Sep 2016
Location: Bellingham, WA

Science and Astronomy Videos

16 Sep 2017 18:15

DoctorOfSpace, no, I'm telling you that you are right. :)  All events that make up your life from birth to death exist as a world line in space-time.  Your eating something in 10 years is an event which is unambiguously in your future.

The point I'm making is that past and future are not always unambiguous.  Your map of space-time changes depending on your frame of reference, and this can make certain events (those which are space-like separated) change their sequence.  It's not just that one person's tomorrow may be your today.  It's that what what we say happens tomorrow on Kepler-22b and yesterday on Gliese 667Cc may happen in the opposite order according to someone else.  

This aspect of relativity is slightly more subtle and difficult to reconcile for someone who tries to view space-time as a structure where all events exist in some fixed configuration with some global notion of "now" moving through it.

We can make this more extreme by adding in space-time curvature.  Events which occur inside an event horizon exist, but not according to observers who are outside.  Not just because they don't see them, but because that region of space-time never forms in their frame of reference.  That slice of "now" that goes from past to future never gets there.  But it does get there if you choose to fall in soon enough.  Weird!
 
A-L-E-X
World Builder
World Builder
Posts: 804
Joined: 06 Mar 2017

Science and Astronomy Videos

17 Sep 2017 16:06

Watsisname wrote:
A-L-E-X wrote:
Source of the post Basically, the past, present and future all coexist as if on a landscape of time and we journey through it, unaware that time is just like the other three dimensions we know about.

Relativity raises trouble with this idea though, because what events are in the past and what are in the future are not absolute, but rather depend on one's state of motion (the relativity of simultaneity).

Pilot wave theory is one of the ideas that sounds really good and conceptually explains some things like double slit interference, but as far as I'm aware it hasn't reproduced all the precise mathematical predictions of QM.

Yes, I was wondering about that when I saw a quote attributed to Einstein about the past, present and future in those terms.  Then again he also supposedly stated that "reality is an illusion, but a stubbornly persistent one."   Are either of these misquotes or did he actually say them?
If events are not absolute, then doesn't that make time travel to the past possible even with just one timeline?  You'd just erase one set of events and replace them with another and even if you went back to the past and killed your grandfather, the "you" that did that would be a relic of a timeline that was replaced.   So no paradox (although you'd be breaking a conservation law or two by suddenly appearing in a timeverse you were never born in, ah well...........)
 
A-L-E-X
World Builder
World Builder
Posts: 804
Joined: 06 Mar 2017

Science and Astronomy Videos

17 Sep 2017 16:10

DoctorOfSpace wrote:
Watsisname wrote:
Source of the post Relativity raises trouble with this idea though, because what events are in the past and what are in the future are not absolute, but rather depend on one's state of motion (the relativity of simultaneity).

Doesn't it also pretty clearly say that all of time must exist as all of space exists since the two are really one?  If that is the case, then what I am going to eat in 10 years already exists.

So we are talking about the same thing but in different words then?  You could still have multiple timelines in this scenario, but they would have to have existed since the BB.  In my writing, I hypothesized this to be the case and the mechanism for it could be the Inflationary Period of the early universe.  Of course you'd need to add a second dimension of time to make this work.
 
A-L-E-X
World Builder
World Builder
Posts: 804
Joined: 06 Mar 2017

Science and Astronomy Videos

17 Sep 2017 16:14

Watsisname wrote:
It exists, but different observers may disagree whether one event precedes or follows another event, if they are separated more in space than in time.  Time is not a fixed landscape that we pass through in an absolute sense.  The slice of "now" that separates past from future depends on how you are moving.

This could still work with a temporal landscape but the landscape wouldn't be a flat plane.  Blah this is easier for me to visualize than it is to state in words, Wat, so I must apologize for that!  What I'm visualizing though makes me feel that there is a strong link between time and gravity, much more than either has in common with the other dimensions or the other forces respectively.
 
A-L-E-X
World Builder
World Builder
Posts: 804
Joined: 06 Mar 2017

Science and Astronomy Videos

17 Sep 2017 16:18

Watsisname wrote:
DoctorOfSpace, no, I'm telling you that you are right. :)  All events that make up your life from birth to death exist as a world line in space-time.  Your eating something in 10 years is an event which is unambiguously in your future.

The point I'm making is that past and future are not always unambiguous.  Your map of space-time changes depending on your frame of reference, and this can make certain events (those which are space-like separated) change their sequence.  It's not just that one person's tomorrow may be your today.  It's that what what we say happens tomorrow on Kepler-22b and yesterday on Gliese 667Cc may happen in the opposite order according to someone else.  

This aspect of relativity is slightly more subtle and difficult to reconcile for someone who tries to view space-time as a structure where all events exist in some fixed configuration with some global notion of "now" moving through it.

We can make this more extreme by adding in space-time curvature.  Events which occur inside an event horizon exist, but not according to observers who are outside.  Not just because they don't see them, but because that region of space-time never forms in their frame of reference.  That slice of "now" that goes from past to future never gets there.  But it does get there if you choose to fall in soon enough.  Weird!

You can analogize to space fairly easily though.  The planet is round (contrary to what some may think lol), so one observer's west could be another observer's east.

What you said about space-time curvature also makes a lot of sense.  I think of an event horizon like a closed door.  Things that can happen behind the closed door that we would never know about.  But just because we don't know about them doesn't mean they didn't happen :P
 
User avatar
Watsisname
Science Officer
Science Officer
Posts: 884
Joined: 06 Sep 2016
Location: Bellingham, WA

Science and Astronomy Videos

17 Sep 2017 22:23

A-L-E-X wrote:
Source of the post If events are not absolute, then doesn't that make time travel to the past possible even with just one timeline?

No.  Events are absolute in the sense that one, and only one, event specifies a location in space-time.  (In other words, a particular point of space-time is that event).  What I was saying is that a region of space-time may or may not be accessible to you depending on where you are and the space-time geometry.

So this still doesn't allow backwards time travel.  An event in the future cannot affect an event in the past, or an event in elsewhere (regions of space-time that require FTL speeds to reach from the source event).  Causal influence must be limited to the future light cone.

There's a pretty good walkthrough of why this must be the case on PBS Space-time. 
I also discuss some of the details on the old forum, though I dunno how clear my explanations are. :)

A-L-E-X wrote:
Source of the post So we are talking about the same thing but in different words then?  You could still have multiple timelines in this scenario, but they would have to have existed since the BB.

Possibly.  We're all saying that all points in time and space exist, I'm just saying they're not in a structure that appears the same to everyone.  The thing that is the same to everyone is the distance (in space-time, or "space-time interval") between all events.  Distances in space, intervals of time, and even the relative order (which event happens first) are all relative, but the space-time interval is not.

Now if we say that an event has several possibilities, all of which occur (as in the Many Worlds Interpretation), then the space-time is everywhere proliferating into new, causally disconnected space-times.  However, this still doesn't allow time travel into the past within or across those space-times.  The causal structure forbids it.

On the other hand, literally adding a second time dimension to the space-time would have dramatically different effects.  What that does is cause every event to have causal effects in two distinct time dimensions, yet those dimensions are not causally separated, so very quickly you end up with closed time-like curves -- paradoxes.  This is one of the common reasons for excluding theories with multiple time dimensions from physics, though there are actually many others.

The only way to get multiple time dimensions to work nicely is to have all but one of them be so chaotic (as in a having an enormous temperature for particle motions in that time dimension) that there can be no information propagated along a closed time-like curve, thus ensuring no causal paradoxes.  (A good paper about this can be found here by Foster et. al).  I think this is a pretty weird way to do physics though -- it's interesting, but doesn't have a compelling motivation or provide much explanatory power.  I don't think it's a good way to describe how nature works.

A-L-E-X wrote:
Source of the post This could still work with a temporal landscape but the landscape wouldn't be a flat plane.  Blah this is easier for me to visualize than it is to state in words, Wat, so I must apologize for that!  What I'm visualizing though makes me feel that there is a strong link between time and gravity, much more than either has in common with the other dimensions or the other forces respectively.

Haha, that's okay. :)  These things are often difficult to describe (or visualize, for that matter).  

There is a link between time and gravity (time passes more slowly in stronger gravity field), but also space and gravity (straight lines deviate, areas and volumes work differently, etc).  That's just general relativity of course -- gravitation is a distortion of space-time geometry.  But other forces participate, too.  A strong electromagnetic field distorts space-time, as do large fluctuations of any other field.  Energy itself bends space and time.  Or another way of saying this is that all forms of mass-energy produce gravitation.

This may or may not be related to what you're describing but there's a popular idea that gravitation is weaker than the other forces because it "leaks" into other dimensions somehow.  I'm guessing you're familiar with it, though I don't know much detail about how it would work.

A-L-E-X wrote:
Source of the post What you said about space-time curvature also makes a lot of sense.  I think of an event horizon like a closed door.  Things that can happen behind the closed door that we would never know about.  But just because we don't know about them doesn't mean they didn't happen


I like that!  I never thought of a door analogy before, but that actually works pretty well.  Imagine there is a house somewhere, and you try sending a bunch of packages.  You get the notifications that they were delivered, but nobody took them inside.  They just sit there and form a pile right outside the door.  Eventually you decide to go there yourself to see if anyone's home.  As you walk up to the door you discover that there is no pile of packages at all.  Before you have the chance to ponder that the door opens and someone yanks you inside and kills you.  :o

So were the packages delivered?  (Did events occur inside the horizon?)  Yes, but the price of discovering them is your doom!

Another visualization I like, and one which you can demonstrate pretty easily in nature, is to make ripples in a stream or river.  If you can find a place where the water is flowing quickly enough, the whole ripple gets carried downstream with the flow.   You might even be able to find a rapid where the flow stars out slower than the speed the ripple spreads, but then gets faster.  Then if you make a ripple at the right spot, the part of it spreading upstream just sits there, while the rest gets sucked downriver.  This is a very good analogy to a pulse of light emitted at an event horizon.
 
User avatar
midtskogen
Pioneer
Pioneer
Posts: 369
Joined: 11 Dec 2016
Location: Oslo, Norway
Contact:

Science and Astronomy Videos

18 Sep 2017 03:38

Reading this discussion it's hard not to think of Plato's allegory of the cave.  All observable phenomena are projections on the cave wall, projections which we believe to be reality. Discussing what these are projections are is very much philosophy as it is science (that division is fairly recent also, and perhaps philosophy and science haven't quite parted after all).
Last edited by midtskogen on 18 Sep 2017 07:26, edited 1 time in total.
NIL DIFFICILE VOLENTI
 
User avatar
Watsisname
Science Officer
Science Officer
Posts: 884
Joined: 06 Sep 2016
Location: Bellingham, WA

Science and Astronomy Videos

18 Sep 2017 05:00

Just so.  For example, on some level we don't know what stars are.  They're just lights in the sky that "behave nicely" in the sense that our knowledge of other phenomena (gravity, thermodynamics, nuclear physics, etc) happen to make sensible, testable models about how they appear and on their role on the rest of the stuff we observe like planets and so forth.

Science is concerned with constructing models and testing how well they agree with observation, not what the "truth" behind the observation "really" is.  It studies the behavior of the projections on the wall so that others might compare with their own observations of them.  We might get confidence that we understand what causes the projections, but that's still just a model and the truth might be a bunch of demons.
 
User avatar
midtskogen
Pioneer
Pioneer
Posts: 369
Joined: 11 Dec 2016
Location: Oslo, Norway
Contact:

Science and Astronomy Videos

18 Sep 2017 08:28

Yes, we might have to get used to the idea that we're forever trapped in the cave,  There's no hint that we somehow can transcend out of spacetime to get a view of it from the outside, seeing everything everywhere, the past, present and the future, becoming omniscient as seen from the inside.  That's purely metaphysics.
NIL DIFFICILE VOLENTI

Who is online

Users browsing this forum: No registered users and 2 guests