Author Topic: Thoughts About Relativity  (Read 1423 times)

Offline SGOS

Thoughts About Relativity
« on: January 27, 2018, 02:54:14 PM »
I often hear what seem like complaints about the theory of Relativity, such as it doesn't explain the physics of what happens at the quantum level.  Einstein tried to include an explanation for gravity and included a gravitational constant in his calculations to fix a perceived problem with his theory.  It was later taken out, and I think I recall that it was later put back in.  I don't know if it's in or out at this time.  It has also been said that Einstein wasted the later part of his life his searching for a unifying theory.  I can't recall what that was.  Maybe because there is no unifying theory, but I'm thinking it had something to do with explaining particle physics that were unknown or disregarded when he came up with relativity.

But what dawned on me recently is that why does there have to be a unifying theory?  Particles don't act the way things do on a big scale.  They seem to pop in and out of existence like they are following some other laws, but why should they be subject to the same laws as big scale physics?  Maybe they are and we don't yet understand it, but so what if they don't?  Maybe there are laws we don't know about.  We have theories of different things.  Evolution is probably the most understood, cross referenced, and explains what it needs to explain.  That didn't seem to bother Einstein.  I don't think he talked a lot about evolution in regards to relativity, but then evolution is part of things in the big scale, so why would he worry about it?

But it seems to me that people are bothered by the lack of a unifying theory, whatever that may be.  I know little about this stuff, but I'm not seeing what the problem is.  Here's a good unifying theory:  God did it, and that explains everything.  Unfortunately, it can't be measured or verified, and it doesn't seem necessary anyway.

Online Cavebear

Re: Thoughts About Relativity
« Reply #1 on: January 27, 2018, 02:59:53 PM »
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I often hear what seem like complaints about the theory of Relativity, such as it doesn't explain the physics of what happens at the quantum level.  Einstein tried to include an explanation for gravity and included a gravitational constant in his calculations to fix a perceived problem with his theory.  It was later taken out, and I think I recall that it was later put back in.  I don't know if it's in or out at this time.  It has also been said that Einstein wasted the later part of his life his searching for a unifying theory.  I can't recall what that was.  Maybe because there is no unifying theory, but I'm thinking it had something to do with explaining particle physics that were unknown or disregarded when he came up with relativity.

But what dawned on me recently is that why does there have to be a unifying theory?  Particles don't act the way things do on a big scale.  They seem to pop in and out of existence like they are following some other laws, but why should they be subject to the same laws as big scale physics?  Maybe they are and we don't yet understand it, but so what if they don't?  Maybe there are laws we don't know about.  We have theories of different things.  Evolution is probably the most understood, cross referenced, and explains what it needs to explain.  That didn't seem to bother Einstein.  I don't think he talked a lot about evolution in regards to relativity, but then evolution is part of things in the big scale, so why would he worry about it?

But it seems to me that people are bothered by the lack of a unifying theory, whatever that may be.  I know little about this stuff, but I'm not seeing what the problem is.  Here's a good unifying theory:  God did it, and that explains everything.  Unfortunately, it can't be measured or verified, and it doesn't seem necessary anyway.

Relativity is both in and out, and that isn't a Heisenberg joke.  Sometimes it works well and sometimes it doesn't.  I hate the whole idea myself and suspect that we will get beyond timespace some day. 
Atheist born, atheist bred.  And when I die, atheist dead!

Re: Thoughts About Relativity
« Reply #2 on: January 27, 2018, 03:08:15 PM »
Well, the two most successful theories of nature that have so far been put forward are completely incompatible, and physicists would much prefer that their two greatest successes were not so contradictory. Their incompatibility means that at least one of them can't be completely correct, or maybe even both of them are wrong. But if either of them are wrong then why do they both work so well?

An analogy might be: What if my mother and father never met each other? And yet here I am, so they must have met. But they both claim not to have ever met, since they lived in different countries. But here I am, so how could they not have met?
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Online Cavebear

Re: Thoughts About Relativity
« Reply #3 on: January 27, 2018, 03:18:22 PM »
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Well, the two most successful theories of nature that have so far been put forward are completely incompatible, and physicists would much prefer that their two greatest successes were not so contradictory. Their incompatibility means that at least one of them can't be completely correct, or maybe even both of them are wrong. But if either of them are wrong then why do they both work so well?

An analogy might be: What if my mother and father never met each other? And yet here I am, so they must have met. But they both claim not to have ever met, since they lived in different countries. But here I am, so how could they not have met?

Neither is correct entirely.  And it is unlikely that we will ever know physics down to the last detail. 
Atheist born, atheist bred.  And when I die, atheist dead!

Offline Baruch

Re: Thoughts About Relativity
« Reply #4 on: January 27, 2018, 04:02:38 PM »
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Neither is correct entirely.  And it is unlikely that we will ever know physics down to the last detail.

The last detail, is the Planck limit, and that takes more energy than we have as a species.

Hey, I can't speed-chess this kind of topic.  I can respond more, on another occasion.  Y'all are keeping me from my nap, and my cats are not amused.
« Last Edit: January 27, 2018, 04:05:17 PM by Baruch »
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Offline Baruch

Re: Thoughts About Relativity
« Reply #5 on: January 28, 2018, 08:34:01 AM »
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Watch out for corrections in the video.  The animation is overly simplified.

The time contraction part is about light bouncing at right angles to the direction of motion aka relative time.

The length contraction part is about relative space contraction in the direction of motion aka relative space.

When you combine the two in the general case of steady motion at all angles relative to an observer, that is where you have to combine the two ...
which is where the space-time idea comes from.  Dr Minkowski thought that up initially, he was an enthusiast for the ideas of a former student of his, Herr Einstein (who wasn't a PhD yet).

Einstein wrote three Nobel-Prize-winning-type papers when he was only 26 (1905).  And E=Mc^2 was just an addenda to one of them.  Special Theory of Relativity (space-time dilation), Brownian Motion (proof of existence of atoms) and Photon Theory (continued development of QM after Dr Planck started it).  So both matter and light were shown to be particles.  And the behavior of light was shown to have logical implications for matter physics.  Working out the consequences further, 11 years later, produced the General Theory of Relativity (theory of gravity) ... which has also been mostly proven as well, most recently gravity waves from colliding neutron stars.
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Offline Baruch

Re: Thoughts About Relativity
« Reply #6 on: January 28, 2018, 08:47:22 AM »
Here is another elementary explanation, with more math ...

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Unfortunately, scifi has destroyed the popular understanding of science.  As a political agenda, scifi basically is an extension of the idea of the "free lunch", a meme that political parties love to sell to the voters.  Specifically, to reach the speed of light, as ordinary matter (not light) you have to expend infinite energy, regardless of the rest mass of the object you start with.  With photons, the rest mass is zero, so it is an exception.  If energy costs money of non-zero amount per unit, then it takes infinite money for ordinary matter to reach the speed of light from a standing start.  No wonder that Star Trek is socialist, and has to cheat physics with non-sensical warp drives.
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Offline Baruch

Re: Thoughts About Relativity
« Reply #7 on: January 28, 2018, 09:05:59 AM »
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I often hear what seem like complaints about the theory of Relativity, such as it doesn't explain the physics of what happens at the quantum level.  Einstein tried to include an explanation for gravity and included a gravitational constant in his calculations to fix a perceived problem with his theory.  It was later taken out, and I think I recall that it was later put back in.  I don't know if it's in or out at this time.  It has also been said that Einstein wasted the later part of his life his searching for a unifying theory.  I can't recall what that was.  Maybe because there is no unifying theory, but I'm thinking it had something to do with explaining particle physics that were unknown or disregarded when he came up with relativity.

But what dawned on me recently is that why does there have to be a unifying theory?  Particles don't act the way things do on a big scale.  They seem to pop in and out of existence like they are following some other laws, but why should they be subject to the same laws as big scale physics?  Maybe they are and we don't yet understand it, but so what if they don't?  Maybe there are laws we don't know about.  We have theories of different things.  Evolution is probably the most understood, cross referenced, and explains what it needs to explain.  That didn't seem to bother Einstein.  I don't think he talked a lot about evolution in regards to relativity, but then evolution is part of things in the big scale, so why would he worry about it?

But it seems to me that people are bothered by the lack of a unifying theory, whatever that may be.  I know little about this stuff, but I'm not seeing what the problem is.  Here's a good unifying theory:  God did it, and that explains everything.  Unfortunately, it can't be measured or verified, and it doesn't seem necessary anyway.

Now onto the specifics.  Scientists noticed that as we develop more powerful explanations, the explanation covers more and more seemingly unrelated phenomena.  So why not reverse that, come up with a unification, that produces a more powerful explanation?  So electric charge and electric current were unified making the theory of electricity.  Then the theory of electricity was united with the theory of magnetism ... which incidentally explained what light was, but also all sorts of new EM waves of shorter or longer wavelength.  The consequences of EM theory were enormous.  Further experimentation showed that light was strange in other ways, producing Relativity Theory and QM Theory, and that this had consequences for ordinary matter physics.  The physics of particles of zero rest mass, and particles of positive rest mass, are different, but have to be somehow consistent with each other.  Working out what this consistency would amount to, along with new experimental data, produced 20th century physics.  BTW - the X-ray, the electron and radioactivity were all discovered in the late 19th century.  This presages QM Theory by less than 10 years.  QM Theory starts with Dr Planck who was trying to develop a more efficient incandescent light bulb in 1900.

So in practice, a given theory, is used as necessary, to do engineering.  Approximation is your friend, if done right.  In most cases Newtonian physics is sufficient.  It isn't necessary to understand biology, to design buildings for example.  You can keep these separate (aside from some basic knowledge of people's body size and motion).  However given H-Vac systems in buildings, and germ theory, you get the explanation for Legionaire's Disease or "sick buildings".

So far this idea has worked particularly well, that unification, up front, produces results, at least put until 1983 (Standard Elementary Particle Theory) ... and then again in 2014 (Higgs Bosons) and 2017 (Gravity Waves).  There was a hiatus in results, because it is harder and harder to do new experiments, and harder and harder to come up with novel unifications.  Not all unifications have proven useful ... String Theory for example.  The practical effect of Higgs Bosons and Gravity Waves however, is almost nil.  This was first noticed with Relativity Theory (which has limited practical use).  Fortunately QM Theory was of tremendous practical value ... this computer I am using would be impossible without it.

In practice, the patchwork gets the job done.  But scientists are curious and ambitious.  We have run up against practical limitations on large experiments.  From this point forward ... the experiments have to become more clever, not bigger, to produce interesting results.  After all, Dr Planck only needed a light bulb ;-)
« Last Edit: January 28, 2018, 09:09:20 AM by Baruch »
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Offline SGOS

Re: Thoughts About Relativity
« Reply #8 on: January 28, 2018, 10:43:53 AM »
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Here is another elementary explanation, with more math ...
One of those was linked to this, which is quite helpful:
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The last few minutes explain the incompatibility between quantum mechanics and relativity.

Offline Baruch

Re: Thoughts About Relativity
« Reply #9 on: January 28, 2018, 12:01:13 PM »
Right.  Originally QM Theory was only valid for low energy/speed situations.  But already in element spectra, there was a problem with matching prediction with measurement.  The electrons were moving at relatively high energy/speed.  So for elements heavier than Hydrogen, the electrons are more energetically bound by the larger number of protons (which determines element, not isotope).  The higher the energy, the more particle-like the phenomena is.  In ordinary light, the energy isn't so high, so waves are a good description.  With more energetic EM waves, say gamma rays, particles are a better description.  But already the particle aspect was detected in the photoelectric effect, as explained by young Einstein.

Later, with Dirac, an explanation was found that applies to fermions (electrons) ... the Dirac Equation.  The slightly earlier Klein-Jordan equation is for high energy bosons.  This made QM Theory even more confusing than it was already.  But it did explain the spin of the electron, magnetic field of the electron, and predicted the existence of antimatter (positrons).  Applying the Dirac equation to the field, not just the particles, was even worse.  This took until 20 years later, to explain (Feynman etc).  The first Standard Theory is Quantum Electrodynamics.  Later the Weak Force and the Strong Force were explained similarly.  This brings us up to the present version of the Standard Theory.

So ... the current version of the Relativity/QM problem is ... reconciling the unobserved graviton (but we have detected gravity waves) and the observed Higgs boson.  And there may be more than one Higgs boson in some extensions of the Standard Theory.  It takes colliding neutron stars to detect gravity waves ... it takes even higher energy to produce gravitons.  Again, given non-free energy, generating a single graviton, even if they exist, takes a cosmic amount of money.  BTW - tachyons are theoretical particles that ONLY move faster than light.  These seem to be ruled out in nature ... also magnetic monopoles seem to be ruled out (a N field by itself, or a S field by itself).  Other exotic theoretical particles have been devised.

The teleportation issue ... is related to the notion as to what identity is.  Is there one identity for two people who are even closer than identical twins?  Depends on if materialism is correct.  I am not a materialist, so teleportation would be a special case of murder.  There is no necessity, if you have teleportation, that the original needs to be deleted, in fact, the buffer of data can be used to make many copies of you.  And of course, that would be a Star Trek version of the Clone Wars in Star Wars.  One could generate many thousands of copies of Commander Spock.  No wonder Dr McCoy didn't like teleportation!
« Last Edit: January 28, 2018, 12:11:03 PM by Baruch »
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Offline Baruch

Re: Thoughts About Relativity
« Reply #10 on: January 28, 2018, 12:27:43 PM »
A little more advanced analysis of Special Relativity ... plus General Relativity

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The section at 10 minutes mentions how relative to the fast spaceship, any finite size of the universe reduces to zero as you approach the speed of light.  So in fact, relative to the photon, there is only the initial singularity, the Big Bang hasn't happened yet, and will never happen.  We only experience temporal time and spaciousness .... because we are heavy (have rest mass).  Or if you prefer, it is a side effect of the Higgs boson field.
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Offline trdsf

Re: Thoughts About Relativity
« Reply #11 on: January 28, 2018, 10:49:57 PM »
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Well, the two most successful theories of nature that have so far been put forward are completely incompatible, and physicists would much prefer that their two greatest successes were not so contradictory. Their incompatibility means that at least one of them can't be completely correct, or maybe even both of them are wrong. But if either of them are wrong then why do they both work so well?

An analogy might be: What if my mother and father never met each other? And yet here I am, so they must have met. But they both claim not to have ever met, since they lived in different countries. But here I am, so how could they not have met?
Basically, both General Relativity and Quantum Mechanics fail to be able to account for the observed universe at all levels.  GR is great on large scales, and QM on small, and within their respective error bars, they're both correct enough for most purposes.

What physics is looking for is a more general explanation that takes both into account as well as observations that neither can explain properly, in the same way that GR superseded Newtonian gravity.  NASA doesn't need anything more than Newtonian physics to get a probe to Pluto.  Newton wasn't wrong, he was just incomplete.  In the same way, GR and QM aren't wrong, they're just incomplete.
Sir Terry Pratchett, on being told about the theory that the universe is a computer simulation: "If we all get out and in again, would it start to work properly this time?"

Re: Thoughts About Relativity
« Reply #12 on: January 29, 2018, 09:20:33 AM »
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But what dawned on me recently is that why does there have to be a unifying theory?

There doesn't.

But when you look at the way that certain physical theories overlap with each other, it certain looks like there should be.
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tragedy of life is when men are afraid of the light. -Plato

Re: Thoughts About Relativity
« Reply #13 on: January 29, 2018, 09:21:20 AM »
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And it is unlikely that we will ever know physics down to the last detail. 

And we never will with that attitude! :p
Winner of WitchSabrinas Best Advice Award 2012


We can easily forgive a child who is afraid of the dark; the real
tragedy of life is when men are afraid of the light. -Plato

Offline trdsf

Re: Thoughts About Relativity
« Reply #14 on: January 29, 2018, 10:18:38 AM »
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And it is unlikely that we will ever know physics down to the last detail. 
And we never will with that attitude! :p
I got to back up Ursus Major here, just a little -- it's entirely possible, and entirely consistent with the history of scientific advance, that there might not be a final Theory of Everything, just ever better approximations.  General Relativity told us ahead of time where it would fail, so we knew it couldn't be complete from the beginning.  The Standard Model, underpinned by Quantum Mechanics, took a little longer to reveal its gaps.

Also, the Uncertainty Principle is unlikely to be eliminated by a better theory, so there's an inbuilt and inescapable fuzziness to the limits of our knowledge.  At the particle level, reality is statistical.  We can only minimize the limits that puts on our detailed knowledge of the universe, but we can't eliminate it.

Personally, I think there probably is an ultimate Theory of Everything... but it might be 22nd or even 23rd century science, not 21st.  Every time we look at the universe in more detail, it surprises us—hell, we hadn't even gotten a handle on dark matter before it threw dark energy at us.
Sir Terry Pratchett, on being told about the theory that the universe is a computer simulation: "If we all get out and in again, would it start to work properly this time?"

 

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