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DoctorOfSpace
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18 Sep 2017 08:31

Watsisname wrote:
Source of the post Science is concerned with constructing models and testing how well they agree with observation...


I don't think you realize just how great this is as a quote of what science is.
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18 Sep 2017 16:27

Newton may have been the first to say something along those lines explaining what science is and isn't, though he actually strongly rejected what science now uses, the hypothetico-deductal method, but favoured pure induction (i.e. strictly collect all observations, then generalise).  A translation that I found online:

But hitherto I have not been able to discover the cause of those properties of gravity from phaenomena, and I frame no hypotheses. For whatever is not deduc’d from the phaenomena, is to be called an hypothesis; and hypotheses, whether metaphysical or physical, whether of occult qualities or mechanical, have no place in experimental philosophy. In this philosophy particular propositions are inferr’d from the phaenomena, and afterwards render’d general by induction. Thus it was that the impenetrability, the mobility, and the impulsive force of bodies, and the laws of motion and of gravitation, were discovered. And to us it is enough, that gravity does really exist, and act according to the laws which we have explained, and abundantly serves to account for all the motions of the celestial bodies, and of our sea.
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21 Sep 2017 09:00

"Exploration is in our nature. We began as wanderers, and we are wanderers still"
-carl sagan
 
A-L-E-X
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21 Sep 2017 21:39

Watsisname wrote:
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.

Wat, the idea of a second temporal dimension just seems intuitively right to me (actually an infinite number of dimensions of both space and time just allocated differently in different universes.  Dimensions can be mathematically be described as the domain area of a set of functions.)
First heard of this from Hawking's excellent work A Brief History of Time and this is how I envision it.  F-theory is actually the model I've been using in my writing.  Interesting you mentioned the forces.  In the Epkyrotic model, gravity is weaker because it leaks through from another brane.  Black holes consist of strings that "tap" into this brane- just another way of explaining them I suppose.  Another interesting thing (especially with regards to two-way time travel) is that in some models the hypothetical sterile neutrino is thought to be able to travel in time in either direction because it can only be influenced by gravity and not the other three forces.  Another interesting connection between time and gravity.

Mid- I love your analogy with Plato it's one I use myself.  Plato and Aristotle were both extremely enlightened and this was before specialization ruined the thinking professions (I've read research that humans achieved peak intelligence between 2,000 and 5,000 years ago and have been slowly declining since.)  I don't think we are forever trapped in the cave though as we see hints of other dimensions.  One such hint is that unification of the forces becomes much easier and intuitive when additional dimensions are added.  Einstein himself was working on unifying the forces right up until his death and he saw that additional dimensions would be needed to make it happen.  We also have the holographic principle which shows us that the universe can be described as the 3D projection of a 4D black hole in a higher universe.   Nothing wrong with using mathematics and metaphysics to get us beyond where science can go (as long as you can come up with compelling evidence that makes the cosmos more easily explainable in an elegant manner)- I really love math because of how it teases the mind and I love theoretical physics especially for these reasons.  We could also play around with toy models of different universes or even one day use a particle collider of sufficient strength to create universes ourselves (perhaps that's how our own universe came into being?)

https://en.wikipedia.org/wiki/Imaginary_time
If we imagine "regular time" as a horizontal line running between "past" in one direction and "future" in the other, then imaginary time would run perpendicular to this line as the imaginary numbers run perpendicular to the real numbers in the complex plane. Imaginary time is not imaginary in the sense that it is unreal or made-up — it simply runs in a direction different from the type of time we experience. In essence, imaginary time is a way of looking at the time dimension as if it were a dimension of space: you can move forward and backward along imaginary time, just like you can move right and left in space.

Imaginary time is also used in cosmology. It is used to describe models of the universe in physical cosmology. Stephen Hawking popularized the concept of imaginary time in his book A Brief History of Time.

The concept is useful in cosmology because it can help to smooth out gravitational singularities in models of the universe (see Hartle–Hawking state), where known physical laws do not apply. The Big Bang, for example, appears as a singularity in "regular time." But, when visualized with imaginary time, the singularity is removed and the Big Bang functions like any other point in spacetime.

https://en.wikipedia.org/wiki/F-theory

A Two-Time Universe? Physicist Explores How Second Dimension of Time Could Unify Physics Laws

http://www.physorg.com/news98468776.html


Different universes could easily have different arrows of time (but still forward with respect to the objects in that universe) similar to conveyor belts and what moves on those belts.
 
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22 Sep 2017 05:40

More Simulation Theory

"Space is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space." - Douglas Adams
 
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22 Sep 2017 13:20

Thanks, I love these! :-)
 
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22 Sep 2017 13:43

I suspect if we are a simulation all of these people are wrong.  It seems more likely that we are similar to our own universe simulations than a video game, feed values you want to simulate into a computer, let the computer simulate billions of years over days/weeks/months, and then review the data after.  There would be no interactions from the simulation creators, it would simply be a runaway universe in a box.
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22 Sep 2017 14:25

DoctorOfSpace wrote:
I suspect if we are a simulation all of these people are wrong.  It seems more likely that we are similar to our own universe simulations than a video game, feed values you want to simulate into a computer, let the computer simulate billions of years over days/weeks/months, and then review the data after.  There would be no interactions from the simulation creators, it would simply be a runaway universe in a box.

Yes I think Andre Linde stated that we could create universes in this same way and that the universe would curve into itself and "wink" out of existence from our own universe.  So our universe could be considered a quantum computer in itself?
If the dimensions of the superverse are different from the universe created within it, how does the computer determine how many dimensions to make and how they would work?
 
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23 Sep 2017 12:46

Plato's cave allegory again! :)
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24 Sep 2017 14:36

Religion makes people believe and its very strong to compete with anything but wheres science nerd are confused and they have some issues... take any famous man hes believe in something so believe is excellent IMHO..im just saying
I recommend using this mt4 expert advisor for self-earnings
 
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24 Sep 2017 15:34

Thomasnwav

Better by far to embrace the hard truth than a reassuring fable.
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24 Sep 2017 17:05

Belief is to think that something is true because someone told you, or you read it somewhere, or because other people think it is true, and you decide to think that it is true as well.

Science teaches us to question a belief.  "Is that conclusion supportable by evidence?"  "Are the predictions of that model consistent with observation?"  

We don't believe something just because "that scientist said so", or "well, it is written in this textbook".  We test it, through the scientific method, by checking if the conclusion can be confirmed by observation and experiment.  I don't believe that moving charges produce magnetic fields.  I know that they do because I measured the effect and found that it agrees with the predictions made by the formulas in the textbook.

If science reports something that I can't test for myself, I can still distinguish it from belief if that finding is testable in principle, and if there are other people out there who are equipped to test it.  I cannot hope to test the existence of gravitational waves myself, but there are several laboratories out there that can.
 
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26 Sep 2017 01:02

With that said, I do find that some scientists tend to be egostistical and give their fellow scientists a hard time when they make discoveries or come up with theories that challenge the paradigm (I hear this complaint quite often.)  There is also the question of monetary influence (this mostly applies to industry rather than "pure" science.)

Still science is far better than religion,  I like to say that science would be perfect if you could remove the humans out of the equation.
 
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26 Sep 2017 11:42

Yes, scientists are people and are not infallible.  Some try to follow untestable ideas thinking that they must be testable, others stubbornly try to hold on to a model long after it is falsified.
 
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27 Sep 2017 12:23

Watsisname wrote:
Yes, scientists are people and are not infallible.  Some try to follow untestable ideas thinking that they must be testable, others stubbornly try to hold on to a model long after it is falsified.

I think that is completely understandable.  What I don't find excusable is when a corporate interest tries to taint science- a la Merck and the Vioxx scandal.  To the credit of the Journal of the American Medical Association, and the New England Journal of Medicine, they both called out Merck for publishing fake research and using ghost writers to boost sales of their drugs (and also trying to blacklist doctors who wouldn't do it.)  The fact that members of said pharma company actually worked on the FDA is another highly concerning matter.
Another thing (which also has to do with corrupt corporate and government influence) is when- as an example- Bristol-Squibb-Myers was infecting 774 Guatemalans with needles tainted with syphilis to test drugs on them or when scientists/doctors with the CIA were testing torture drugs on mental patients or assisting in torture themselves.  To their credit, the rest of the scientific community condemned them and I would hope they lost their privilege to practice.

And of course there are the fossil fuel and tobacco industries......
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