Is causality a neccessary part of relativity?

[ianke]

While it seems to me that causality is a logical part of the way science deals with the facts we can know, is it an intrinsic value or law that must be followed in all cases? Does our modern understanding of physics need causality to explain all things or can there be other ways of looking at things?<br /><br />While I have spent my life and career as a chemist in the camp that says that a cause must occur before hand to yeild a predictable effect, is this an unbreakable law when it comes to time? As of late the issue of causality has been brought up and disputed in several threads lately. This has left me somewhat confused on the issue.<br /><br />I would welcome any opinions from either camp (pro, or con on the causality issue) Please keep it scientific though.<br /><br />Thanks to all ahead of time.<br /><br />Ianke <div class="Discussion_UserSignature"> </div>

 

[emperor_of_localgroup]

Ianke, strangely you read my latest mind on Time. I have been thinking exactly the same thing about Time for the last few weeks. <br /><br />Time as we know and perceive is causing a major a problem in 'starting point' of anything because of causality issue. If we trace things back in time, sooner or later we'll be forced to break causality requirements to get an acceptable answer. <br /><br />If that's the case then why not drop the current perception of Time and redefine the nature of Time. No, I have no suggestion on how to redefine time. I'm just pointing out a new definition of Time is necessary. Because we are seeking an answer to a quesion which cannot be answered with the current concept of time.<br /><br />Though it not clear to me how will relativity causality solve this problem. <div class="Discussion_UserSignature"> <font size="2" color="#ff0000"><strong>Earth is Boring</strong></font> </div>

 

[SpeedFreek]

I look at it like this.<br /><br />Causality seems to reign supreme <i> within </i> our universe at the macroscopic scales. Everywhere we look, we see cause and effect at work. From the atomic to the molecular to the formation of stars and galaxies to the expanding universe we see causality.<br /><br />In this context, causality only breaks down when we trace the history of the universe back to the initial cause. After that, causality rules!<br /><br />At least, that is what we see on the <i> outside. </i> When we look deeper we find the quantum world, a place where causality seems to lose its grip. Suddenly things seem to pop in and out of existence with no apparent cause. This is somewhat similar to the 'initial' event of the universe, if there was one.<br /><br />So the macroscopic universe works using causality as described by relativity, but the framework upon which it works, the quantum level, is not causal. If that framework doesn't need causality, then neither does it's existence in the first place. <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

 

[ianke]

A lot of people seem to be bending towards the direction you have just stated. I on the other hand do not know which way to bend on the issue. For our everyday use causality seems pretty much boiler plate in the way we deal with the phisical world. There does seem to be issues with it when it comes to things like the Big Bang, or the paradoxes of light speed and time.<br /><br />I tend towards being old school in thinking that the speed of light is an absolute brick wall you can not exceed, however, there seems to be some convincing arguements as to how to beat it. In this instance causality becomes an issue. (Reading the message before it is sent type of thing, or reversing the flow of time, or any number of hypotheses tend to stick their nose up at causality) <br /><br />Or is it Causality that thumbs its nose at the rest? <br /><br /><br />Anyone want to chime in for the old school "causality rules" side? <div class="Discussion_UserSignature"> </div>

 

[ianke]

Sorry speedfreek. I type way too slow. <div class="Discussion_UserSignature"> </div>

 

[vandivx]

I would just point out that in those areas where causality suffers (or seems to suffer) are precisely those of which we don't have enough understanding (that's even understatement or is it overstatement)<br /><br />I can see that we would probe into reality beyond our current ability to make sense of it and full understanding might have to wait several centuries even, to make judgement now on the basis of QM which nobody still understands at all is foolish, I'd say we know enough to know where our limits are<br /><br />I also feel that our energies should be put into making sense of QM and other areas of physics instead of spending our ingenuity on fruitless speculations because they are done on definitely shaky basis<br /><br />it is not inconceivable that the speed of light will increase in the future, say it will increase to 1.1c and in that case we still wouldn't have FTL travel because then we wouldn't be able to buck this new speed of light, so in such case the causality would still hold<br /><br />vanDivX <div class="Discussion_UserSignature"> </div>

 

[emperor_of_localgroup]

But the macroscopic universe is built upon the elements of microscopic or quantum universe. The transition from QM universe to macroscopic universe seems to be continuous. In such case how can QM universe violate causality but the our visible universe exhibits zero cases of causality violation? <br /><br />At this point in time my wild guess is it is because of our poor technology. As our verification technology improves someday (I mean some century) we'll find instead of a chaotic environment a smooth ordered environment also exists in QM universe where macroscopic causality is still obeyed faithfully . <div class="Discussion_UserSignature"> <font size="2" color="#ff0000"><strong>Earth is Boring</strong></font> </div>

 

[alkalin]

Math does not require causality, but reality does. What more should be said? Everything has a cause, but if math cannot express that cause, then we need to look elsewhere for further answers. It is certain that we cannot yet know many of the causes of reality, but it is important that we keep trying. It is not likely that the full complexity of reality will ever be expressed mathematically.<br /><br />

 

[robnissen]

<font color="yellow">Causality seems to reign supreme within our universe at the macroscopic scales. Everywhere we look, we see cause and effect at work.</font><br /><br />I think that is a massive overstatement. Regular matter and regular energy make up about 5% of our known universe. Dark matter about 25% and Dark Energy 70%. But we have no idea what those are. We simply have NO IDEA why galaxies don't fly apart, so we assume there must be 5 TIMES as much dark matter, as known matter, otherwise causality would be violated. Similarly we have NO IDEA why Super Nova are increasing their acceleration away from us, so we assume that DARK ENERY exists and that it is over 18 TIMES as much dark energy as known matter. We ASSUME that Dark Matter and Dark Energy exist, because without those Causality would be violated. But maybe Causality IS VIOLATED and Dark Energy and Dark Matter do not need to exist.

 

[why06]

You Said:<br /><blockquote><font class="small">In reply to:</font><hr /><p><font color="yellow"><i> Regular matter and regular energy make up about 5% of our known universe. Dark matter about 25% and Dark Energy 70%.<blockquote><font class="small">In reply to:</font><hr /><p><font color="yellow">But maybe Causality IS VIOLATED and Dark Energy and Dark Matter do not need to exist.</font></p></blockquote></i><font color="white"><p><hr /></p></font></font></p></blockquote><br /><br />What is causalty? As I understand it is simply a law of cause and effect. The cause is dependant on the input. The effect is dependant on the output, but the inpu always has to equal the output. The universe works like this, well as as far as I know (at speeds STL). Personally I don't see the problem. Is something wrong? <img src="/images/icons/wink.gif" /><br /><br /><br /> <div class="Discussion_UserSignature"> <div>________________________________________ <br /></div><div><ul><li><font color="#008000"><em>your move...</em></font></li></ul></div> </div>

 

[SpeedFreek]

<font color="yellow"> <i> We ASSUME that Dark Matter and Dark Energy exist, because without those Causality would be violated. But maybe Causality IS VIOLATED and Dark Energy and Dark Matter do not need to exist. </i> </font><br /><br />Or... maybe there is another <i> cause </i> for the observation that the motion of stars in galaxies is inconsistent with our theory of gravity. Maybe there is another <i> cause </i> for the apparent acceleration of the metric expansion of space.<br /><br />The possible non-existence of dark matter and energy doesn't neccessarily violate causality. It might just mean we don't know the true cause yet!<br /><br />Perhaps our theory of gravity is wrong at larger scales - this could affect the status of both dark matter and dark energy. If that were the case, causality would still rule in the macroscopic universe! <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

 

[robnissen]

<font color="yellow"> maybe there is another cause for the observation that the motion of stars in galaxies is inconsistent with our theory of gravity. Maybe there is another cause for the apparent acceleration of the metric expansion of space. <br /><br />The possible non-existence of dark matter and energy doesn't neccessarily violate causality.</font><br /><br />I agree completely. I would have been more clear, however, if I had said causality "might" be violated, not "would" be violated. My point was, when we don't have a fricken clue what 95% of the universe is, we can not say that causality exists through-out the macro universe. Although it seems logical that causality exists at the macro level, until we know what that other 95% is, we have no way of KNOWING.

 

[why06]

Casualty exists at the microscopic level too. It is space-time itself that is disobeying its own laws... But matter still functions the same way. <div class="Discussion_UserSignature"> <div>________________________________________ <br /></div><div><ul><li><font color="#008000"><em>your move...</em></font></li></ul></div> </div>