Perils of theoretical physics

[PB666]

http://www.scientificamerican.com/article/is-string-theory-science/

This particular article uses string theory as an example of great chasm can grow between experimental and theoretical phyicist, calling in scienc philosophers to modulate. The problem with theorectical physics is observations set boundaries, that either have to be obeyed or observationally explained. Once niether of these can be done tolerances in application can result in a variety of possibilites, as has been suggested by multiverse opponents, there could be universe with laws different from our own. Occamic reasoning applies to limit unneccesary complexity in theories, and only observations can ultimately found a basis for more complexity. 

[K^2]

String theory got over-hyped early on, leading to it turning into a buzz word, which is why so much pop-sci has been devoted to it. The reality is that interest in string theory among actual particle physicists has been winding down since the late 90s. By now, it is largely considered a mathematical curiosity. While useful dualities can be constructed, they are rarely more convenient than standard model.

And the reason for this change has been lack of experimental support. String Theory makes few predictions that can be tested, and these that potentially could be, have not been verified. So while I can see how excitement over string theory can look alarming to an outsider, it's been a very minor setback in the actual field.

[lajoswinkler]

1 hour ago, K^2 said:

String theory got over-hyped early on, leading to it turning into a buzz word, which is why so much pop-sci has been devoted to it. The reality is that interest in string theory among actual particle physicists has been winding down since the late 90s. By now, it is largely considered a mathematical curiosity. While useful dualities can be constructed, they are rarely more convenient than standard model.

And the reason for this change has been lack of experimental support. String Theory makes few predictions that can be tested, and these that potentially could be, have not been verified. So while I can see how excitement over string theory can look alarming to an outsider, it's been a very minor setback in the actual field.

So why the hell is it called a theory if it lacks empirical evidence? Seems that theoretical physicists think so high of themselves so that they can skew definitions. It's a hypothesis. Always was and could stay like that indefinitively...

[Temstar]

17 minutes ago, lajoswinkler said:

So why the hell is it called a theory if it lacks empirical evidence?

What else would you call it? When Einstein first published General Relativity he had zero experimental proof either. He actually had to go beg astronomers to do eclipse photography so that his theory had grounds to stand on.

Or alternatively think about it this way: how do experimental physicist know what machines they should design if they don't know what they should be looking for?

[Elrond Cupboard]

3 minutes ago, Temstar said:

What else would you call it?

A hypothesis, he already did, and strictly speaking, he's right.

[lajoswinkler]

29 minutes ago, Temstar said:

What else would you call it? When Einstein first published General Relativity he had zero experimental proof either. He actually had to go beg astronomers to do eclipse photography so that his theory had grounds to stand on.

Or alternatively think about it this way: how do experimental physicist know what machines they should design if they don't know what they should be looking for?

When Einstein published it, it wasn't a theory. It was a hypothesis. Nowdays it's a theory because it has evidence to support it and serves to predict stuff, too, as a bonus.

It's funny how it's usually the physicists that are rabid about the whole theory/hypothesis/law terminology, and yet as if all of that gets ignored when team Sheldon is on the stage. IDK, it just annoys me. I don't call a theory.

Now, some might say it's math, and theories in math are something else. Boo hoo, make up your mind, people.

It's a mathematical theory and a physical/scientific hypothesis. Nothing more, nothing less.

[AngelLestat]

There are some definitions differences between Theory and Scientific Theory. The same for Evidence and Scientific Evidence.

If your hypothesis is base on a mathematical model that can describe any particle in the universe, and you tested and it works for each particle, then; it is evidence that supports your theory.

It can not be called a Scientific Theory, but for sure can be called a Theory.    

[K^2]

3 hours ago, lajoswinkler said:

So why the hell is it called a theory if it lacks empirical evidence? Seems that theoretical physicists think so high of themselves so that they can skew definitions. It's a hypothesis. Always was and could stay like that indefinitively...

It's a theory in a mathematical sense, not a scientific one. As in, "Set Theory," "Group Theory," etc. The mathematical portion of String Theory is solid, so it's fair. The hypothesis part was, "All this math has something to do with reality." And that's the bit that didn't seem to have panned out.

[Findthepin1]

Said the user with 666 reputation. XD

Edited December 25, 2015 by Findthepin1

[magnemoe]

http://xkcd.com/1621/  is pretty relevant 

 

[ouion]

Einstein-Rosen Bridges are valid by mathematical calculations, but wormholes are never observed. So theoretical physics is the mathematical part of physics and can validate certain phenomenon by mathematical equations. Experimental Physics are trying to validate some theoretical physics concepts using the scientific method. Yes, of course there are some theoretical physics concepts are validated and observed by Experiments.    

[K^2]

53 minutes ago, ouion said:

Einstein-Rosen Bridges are valid by mathematical calculations, but wormholes are never observed. So theoretical physics is the mathematical part of physics and can validate certain phenomenon by mathematical equations. Experimental Physics are trying to validate some theoretical physics concepts using the scientific method. Yes, of course there are some theoretical physics concepts are validated and observed by Experiments.    

With exception of some murky corners of certain String Theory interpretations, none of the field theories, including General Relativity, predict a mechanism for topology of space-time to vary. Which means, as far as we know, and this is one of the few things that are definitely subject to change, the total number of wormholes in all of the universe is a conserved quantity. That quantity can be very low. It can even be zero.

So us not observing any wormholes has a very simple explanation. There aren't enough of them in the universe to make proximity to one to observe sufficiently likely. This is very different from things like Supersymmetry and String Theory predicting buckets of new particles, with none to be found.

 

To put this in more precise and general terms, what scientific theory needs is to withstand a test of critical experiments. Looking for wormholes does not satisfy criteria of a critical test, because we aren't necessarily expecting to find any. String Theory fails critical experiments designed specifically to test it. It leaves loopholes, sure. But with each experiment, validity of that theory becomes less and less likely.

[PB666]

On December 25, 2015 at 1:56 PM, magnemoe said:

http://xkcd.com/1621/  is pretty relevant 

 

Funny, but impertinent

1 hour ago, ouion said:

Einstein-Rosen Bridges are valid by mathematical calculations, but wormholes are never observed. So theoretical physics is the mathematical part of physics and can validate certain phenomenon by mathematical equations. Experimental Physics are trying to validate some theoretical physics concepts using the scientific method. Yes, of course there are some theoretical physics concepts are validated and observed by Experiments.    

Wormholes convieniently explain long range interactions on the quantum scale, unfortunately for the rest of the world these are not called wormholes but entanglement. 

[K^2]

The only connection between wormholes and entanglement are the names of Einstein and Rosen and some half-baked mathematical constructs that aren't even fully fledged hypotheses yet. For starters, no-communication theorem does not apply to wormholes.

[PB666]

And wormholes are a fantasy and entanglement is not, if we extend the logic then ftl communication is a fantasy.

[K^2]

That's not how extending the logic works. In fact, that's not how logic works.

[monstah]

On ‎24‎/‎12‎/‎2015 at 9:26 AM, K^2 said:

String Theory makes few predictions that can be tested, and these that potentially could be, have not been verified.

Question: do you mean not verified as in, no conclusive experiment has been realized, or as in, experiments have concluded those predictions false?

[PB666]

3 hours ago, K^2 said:

That's not how extending the logic works. In fact, that's not how logic works.

'IF' being the key word.  Its no more of a fantasy than wormhole hypothesis. Fantasies after all open up all kinds of logical possibilities, for example if I can say focus the plasma of a star into a planet, then I can beam that plasma to blow up 5 planets at once, and sell a billion in a movie theater on one night. You cannot really argue that one persons fantasy is more logical than the nexts. Fantasies sell, reality is less palatable.

As for theoretical physics, if you want to set a practical limit then this is one of the goalpost. https://en.wikipedia.org/wiki/Vacuum_catastrophe,

Lol. String theories problems are small in comparison. Albeit, we can just put these things on the table and just say what they are:

Alcubierrie drive (tachyons and the like)
Wormholes, wormhole travel
Traveling backward in time
Quantum based transporters applied to larger than Planck's scale objects.

I for one do not believe that entanglement intrinsically limits communication, as the latest experiments seem to demonstrate, the limit may be on space-time (IOW how long-far that it can be done). So for example say I created a billions pairs of entangled particles which I then separated into two identical boxes, I then send one on a ship to a distant world, say 400 hundred years in the future the sent unit is resolved on a timed schedule, followed by observation of the stationed unit, there is nothing to per-say prevent communication as long as the resolution occurs before observation. I could theoretically used this to create a bit map and instantly create an image elsewhere at some later point. Then the question is how to create and keep pairs without their states being modified. Light for instance is difficult to store in situ, electrons are similarly difficult. The extrinsic factors may limit its use in communication. As the latest quantum computing experiments demonstrate that as long as a process does not interfere with other process that 'have go back in time affects' they can proceed along independent lines.

If all the wormholes in the universe are preordained, then I could travel back in time using a wormhole to a point when inflation stops, drop a grain of sand at a certain point, and cause a huge sector of the known universe to evolve in a completely different way.