Relativity Explained
- Thread starter Chuckanut
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stepford
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Well, that's a listing of some relativistic phenomena, but explanations are supposed to explain "why" those things happen. I don't mean to rain on your parade, but I've been able to work with the phenomenology of relativity for many years, but the deeper nuts and bolts never felt particularly intuitive.
I suppose the 'why' is just that the speed of light is constant in all (inertial) frames of reference and the rest is all just details, but those details bugged me 45 years ago when I first heard them as an undergrad and still bug me a bit to this day.
I suppose the 'why' is just that the speed of light is constant in all (inertial) frames of reference and the rest is all just details, but those details bugged me 45 years ago when I first heard them as an undergrad and still bug me a bit to this day.
Out-to-Lunch
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I strongly agree with this post!
One addition: the constancy of the speed of light is only the "why" for the Special Theory of Relativity (SR). I would say the closest equivalent "why" for General Relativity (GR) is the Equivalence Principle. Similar to stepford's observation for SR, the trip from the simple-to-understand Equivalence Principle to the full theory of GR is, ummm, difficult.
OP
OP
Chuckanut
Give me a museum and I'll fill it. (Picasso) Give me a forum ...
You're not raining on my parade. I just wanted to start a discussion.
In college I had a good understanding of why chemistry and physics worked as they do. But, this relativity stuff is as you say not 'particularly intuitive' for me. I'll pick up a thing or two, here and there, just enough to be dangerous.
With all due respect, there still is no clear understanding of underlying mechanism of gravity. There are lot of theories.
What bothers me is, whenever something doesn't fit in a theory, proponents of theory introduce a new "constant" to make the math work.. that otherwise wouldn't work with normal physics. Oh.. and lets not even get started with Dark matter. Anything that can't be explained is either dark matter or anti-matter
What bothers me is, whenever something doesn't fit in a theory, proponents of theory introduce a new "constant" to make the math work.. that otherwise wouldn't work with normal physics. Oh.. and lets not even get started with Dark matter. Anything that can't be explained is either dark matter or anti-matter
Ah, "Dark Matter"! I attended a senior center review of this topic (The Learning Tree or something like that). Anyway at the end of 6 weeks it was basically "we have no idea of what the stuff is or how to explain it"
With all due respect, there still is no clear understanding of underlying mechanism of gravity. There are lot of theories.
What bothers me is, whenever something doesn't fit in a theory, proponents of theory introduce a new "constant" to make the math work.. that otherwise wouldn't work with normal physics. Oh.. and lets not even get started with Dark matter. Anything that can't be explained is either dark matter or anti-matter
I completely agree.
Due to that "its just turtles all the way down" approach that modern science has now, I searched for alternative theories. There are some. The one I most agree with is called "The Electric Universe".
If you are interested, this website can be a starting point.
frayne
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I have a really hard time wrapping my head around these concepts and that is why I golf. Golf takes into account all of these factors; time, space and gravity. None of which I have yet to fully understand until the 19th hole.
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aja8888
Moderator Emeritus
It's amazing how gravity on a hit golf ball can send it in a horizontal direction into the thickest part of the woods. Probably has something to do with the density and mass of the tress in that area.
Mark1
Full time employment: Posting here.
If the "Faster you move through space, Slower you move through time", then does that mean that as you approach zero movement, does time speed up to infinity?
I'm sure this must be true if we could only figure out how to stop moving.
I'm sure this must be true if we could only figure out how to stop moving.
Well, if relativity is "mind bending" then what about quantum physics? Given that the speed of light is constant in all frames of reference (why? - no idea) the rest of the Special Theory of Relativity makes sense. As to the General theory of Relativity, I flunked tensor analysis in college so no comment there. And Quantum physics - I honestly don't think any of it makes sense to anybody. Sure, we can understand -sort of- how it works so we have all kinds of neat toys that depend on Quantum mechanics being really the way the Universe works. But why all that is the way it is and works the way it does - numono from a frustrated physics major.
easysurfer
Give me a museum and I'll fill it. (Picasso) Give me a forum ...
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I still can't decide if a tree falls in a forest and nobody hears it, does it make a sound?
stepford
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That's the wonderful thing about science - it's based on observation. The Michelson Morley experiment of the late 19th century showed that the speed of light was the same regardless of the motion of the source. Nobody believed this at first and folks tried to come with other explanations of the results.
Einstein's brilliant stroke (among several others in his career) was to act like a true scientist, take the results at face value and then build his theory up from there. He then did what any good theoretical physicist does: He used this theory to make testable predictions - which later proved out. Theories aren't worth squat unless they can be checked in this way.
Indeed. That is the problem with String Theory that purports to tie everything together and explain everything - no testable predictions thus -so far- no better than that famous cartoon of a physicist in front of a blackboard covered with intricate equations saying "and then a miracle occurs"
One concept which got me a small step closer to wrapping my mind around this stuff (I won't go so far as to say "understanding") was this:
From the vantage point of a photon created in a star millions of light-years away, it landed on your retina the same moment it was created. For that photon, time stood still. Or put another way, didn't exist at all.
From the vantage point of a photon created in a star millions of light-years away, it landed on your retina the same moment it was created. For that photon, time stood still. Or put another way, didn't exist at all.
timbervest
Recycles dryer sheets
Actually time is another dimension not necessary the fourth dimension.
If length is the first dimension, width the second (yielding 2D) and height is the third dimension (making things 3D), then another spacial dimension perpendicular to the other three is the fourth dimension -- totally non-perceivable to us (quickly consults "Flatland" by Edwin Abbot). There are theoretically an infinite number (x) of directions perpendicular to all previously defined dimensions (x-1).
I'll let myself out now.
If length is the first dimension, width the second (yielding 2D) and height is the third dimension (making things 3D), then another spacial dimension perpendicular to the other three is the fourth dimension -- totally non-perceivable to us (quickly consults "Flatland" by Edwin Abbot). There are theoretically an infinite number (x) of directions perpendicular to all previously defined dimensions (x-1).
I'll let myself out now.
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martyp
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For those of you with strong math/science backgrounds I highly recommend the YouTube classes by Stanford professor Leonard Susskind. He has several years of classes on Special and General Relativity so search for the most recent ones.
OP
OP
Chuckanut
Give me a museum and I'll fill it. (Picasso) Give me a forum ...
If you have read "The Three Body Problem" trilogy, multiple dimensions turn out to be a significant problem for humanity in the the 3rd book.
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Out-to-Lunch
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Does this theory make any testable predictions?
Clocks at the bottom of a mountain run (relatively) slower than clocks at the top of the mountain. They have clocks so accurate now they can actually measure it.
There is no absolute "now". The ordering of events can differ depending where you are. Relativistic simultaneity.
If you really want to bake your noodle read up on the Double Slit Quantum Eraser. Very disturbing in its implications.
There is no absolute "now". The ordering of events can differ depending where you are. Relativistic simultaneity.
If you really want to bake your noodle read up on the Double Slit Quantum Eraser. Very disturbing in its implications.
ncbill
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I remember deriving E=mc^2 back in physics class in undergrad.
And using partial differential equations in many classes.
Couldn't do either now if you held a gun to my head.
And using partial differential equations in many classes.
Couldn't do either now if you held a gun to my head.
This thread - and its underlying subject matter - remains a constant source of fascination and interest to me. Primary reason is that I often understand the concepts, but the understanding lasts about 5 seconds and I'm back to being [-]befuddled[/-] fascinated. Quantum physics is at least one full-confusion-level above, for me. I think it was derived by some physicist who was on a hallucinogenic drug.
stepford
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Or maybe just some physicists who saw that light interfered like a wave, but arrived in little energy bundles rather than a continuous flow when you turned things down enough. Both are readily observable phenomena that you don't need particularly fancy equipment to see. So particles behave like waves.
Like relativity, QM is just what you get when you connect the dots following this simple (but non-intuitive) observation. Yes, there's all sorts of bizarre seeming results, but it's actually the simplest explanation that fits the data.
Koolau
Give me a museum and I'll fill it. (Picasso) Give me a forum ...
The fact that experiments have proven relativity had to be gratifying to Einstein (though I'm sure he wasn't surprised.) My favorite was the bending of a distant star's light by the gravity (or warping of time/space) by the sun. That took some effort back in the day as total solar eclipses don't happen every day and typically not in convenient places either. IIRC virtually all of Einsteins predictions have been proven. So, it's real even if it doesn't make a lot of sense.
Then again, I still recall learning that the world was round! My older sister told me about it, and of course, I didn't believe her. I might have been 5. Anyway, I talked to this guy who did some carpentry work for my dad. The guy was able to draw me a picture of the world and show how the sun changed position as the world turned. To prove it, he placed a wood chip (maybe a match) on a shadow and had me watch it as the shadow slowly moved away from the piece of wood. It was mind expanding.
Imagine what must have gone through Einstein's mind when he realized the consequences of a constant light speed. I love reading about his thought experiments. I have done that sort of thing throughout my life. I recall imagining shooting a canon with more and more gun powder such that the ball eventually would come back around the Earth and hit me. Of course, wind resistance (and tree/mountains/tall buildings and bulging of the Earth at the central latitudes) were ignored. I think I might have been 15 when this came to me. I hope I hadn't read it somewhere. As always YMMV.
Then again, I still recall learning that the world was round! My older sister told me about it, and of course, I didn't believe her. I might have been 5. Anyway, I talked to this guy who did some carpentry work for my dad. The guy was able to draw me a picture of the world and show how the sun changed position as the world turned. To prove it, he placed a wood chip (maybe a match) on a shadow and had me watch it as the shadow slowly moved away from the piece of wood. It was mind expanding.
Imagine what must have gone through Einstein's mind when he realized the consequences of a constant light speed. I love reading about his thought experiments. I have done that sort of thing throughout my life. I recall imagining shooting a canon with more and more gun powder such that the ball eventually would come back around the Earth and hit me. Of course, wind resistance (and tree/mountains/tall buildings and bulging of the Earth at the central latitudes) were ignored. I think I might have been 15 when this came to me. I hope I hadn't read it somewhere. As always YMMV.
