Ontology of time

[Cap'n Refsmmat]

"We would fry if we got that much closer to our sun. It simply is not true. Measurement does not make the distance change!"

 

I asked, to no avail, how perspective makes the distance change, and if it changed to 1/8 AU (19 million km) why would we not fry? We don't fry because the actual distance remains 150 million km from the sun and the former is a distortion due to the effects of relativity.

Actually, we don't fry, because of how length contraction works.

 

Let me do a bit of calculation for you to demonstrate. The Sun is a blackbody radiator, roughly, with an effective temperature of 6000 Kelvin. Let's set some approximate constants:

 

[math]\sigma = \text{Stefan-Boltzmann constant} = 5.6704\times 10^{-8}[/math]

 

[math]T_{\text{sun}} = 6000 \text{ Kelvin}[/math]

 

[math]R_{\text{sun}} = 7 \times 10^8 \text{ meters}[/math]

 

[math]R_{\text{earth}} = 6\times 10^6 \text{ meters}[/math]

 

[math]R_{\text{orbit}} = 1.5\times 10^{11} \text{ meters}[/math]

 

[math]\gamma = 1\times 10^8[/math]

 

[math]\alpha = \cos^{-1} \frac {1} {\gamma}[/math]

 

[math]\gamma[/math] is the Lorentz factor, which gives us an idea of relativistic velocity, and [math]\alpha[/math] will come in shortly. A Lorentz factor of the size I gave corresponds to a velocity incredibly close to the speed of light, so the traveler is moving very, very fast.

 

Now, let's calculate how much of the Sun's energy reaches the Earth. According to the Stefan-Boltzmann law, the intensity of energy emitted from the Sun is proportional to:

 

[math]I = \sigma T_{\text{sun}}^4[/math]

 

Multiply by the surface area of the Sun, and you get the total energy emitted:

 

[math]E_{\text{sun}} = 4 \pi \sigma T_{\text{sun}}^4 R_{\text{sun}}^2[/math]

 

Only a fraction of that is intercepted by Earth, of course. That fraction is the surface area of the Earth divided by the total area of the shell with Earth's orbital radius; that is, out of that shell, Earth only composes a small portion. The fraction can hence be represented as:

 

[math]f = \frac{\pi R_{\text{earth}}^2}{4\pi R_{\text{orbit}}^2} = \frac{R_{\text{earth}}^2}{4R_{\text{orbit}}^2}[/math]

 

This means the total energy intercepted by the Earth is [math]E_{\text{sun}}f[/math], or:

 

[math]E_{\text{sun}}f = E_{\text{earth}} = \frac{\pi R_{\text{sun}}^2 R_{\text{earth}}^2 \sigma T^4}{R_{\text{orbit}}^2} = 1.81\times 10^{17} \text{ watts}[/math]

 

If you calculate energy per unit area from this, you get something fairly close to the true value, so it's at least approximately correct. (You'll note I rounded many of the original numbers to make calculation easier.)

 

Now, what happens when the Earth gets vastly closer to the Sun?

 

Well, we must remember that it's not simply a matter of [math]R_{\text{orbit}}[/math] shrinking by a factor of [math]\gamma[/math]. If the traveler is flying from the Earth to the Sun (or vice versa), the length contraction only occurs in the direction of his travel. If he were flying perpendicular to a line connecting the Earth and the Sun, the Earth-Sun distance would not change at all.

 

So the Earth's orbit becomes an ellipse, and the orbital shell becomes an oblate spheroid, with a minor axis of [math]b = \frac{R_{\text{orbit}}}{\gamma}[/math] and a major axis of [math]a=R_{\text{orbit}}[/math]. The [math]\alpha[/math] I mentioned earlier is the angular eccentricity, and is [math]\alpha = \cos^{-1}\left( \frac{a}{b}\right)[/math], which works out as I showed above.

 

And of course the same thing happens to the Sun. I don't have to worry about the Earth because the hemisphere in sunlight does not contract, since its radius is perpendicular to the direction of the traveler.

 

Now we must use the surface area of an oblate spheroid to make this calculation, and the resulting equation is rather nasty, so I have taken a picture of the equation and its calculated result in Mathematica for you:

 

 

So... no difference in the energy absorbed by Earth when length contraction occurs. The magic of physics!

 

(note to the other physicists around: please correct me if I made any mistakes, since that was rather long and I'm not perfectly certain of my approach)

 

(also, obligatory xkcd: http://xkcd.com/54/)

[md65536]

Actually, we don't fry, because of how length contraction works.

I would have thought that it could also be answered in terms of time dilation.

 

With gamma = 8, the earth would receive "8 minutes worth of radiation in 1 minute of observer's time" (ie. 1 AU's worth of radiation in the time it takes light to travel 1/8th AU) due to length contraction ???,

but the sun would emit 1/8th the radiation per minute of the observer's time, due to time dilation.

Edited June 28, 2011 by md65536

[Cap'n Refsmmat]

Yes, I think that's another approach, but since length contraction doesn't just reduce the Earth-Sun radius but makes an oblate spheroid, I went the long way.

[owl]

Cap ‘n R:

So... no difference in the energy absorbed by Earth when length contraction occurs. The magic of physics!

(my bold)

 

Yes, and especially the magical math of physics, quite literally it seems!

So how does all that math/physics address the (excuse the phrase) reality of the situation as expressed in your statement above:

 

The Earth does not "move" when someone flies past. Anyone sitting on the Earth will not notice anything. (bold this)The voyager at ludicrous speed will see the Earth as being close to the Sun. He will not see it "move"; it's been that way for as long as he's been flying fast. No force acts upon the Earth to "move" it or change its orbit; it's just the orbit is perceived differently by those in different reference frames.

 

In other words, on the one hand you seem to agree that earth does not actually move closer to the sun, as length contracted measurements would have it. On the other hand, all that physics seems to be an argument for the opposite, i.e., that the 19 million km distance, as seen from the fly-by frame is accurate in ‘the real world’ and that, by the above “magic” somehow the heat diminishes with the shorter distance and time of exposure.

 

Again, I do not deny that the voyager “will see the earth as being closer to the sun.” But it still looks like a distortion effect of relativity to me. Same with earth’s diameter. It does not shrink just because extremely high speed frames of reference from which it is measured make it look like a 1/8 sized mini-earth.

 

As admitted many times, I do not understand the advanced math, but I do understand the concepts of closer vs further away and that, in reality, the closer anyone (or anything) gets to the sun, or any other star (or hot object) the hotter it gets. It seems to me (and, I would argue, from the ontological perspective, inquiring into what is real here) that the complex physics in this case is mental magic, smoke and mirrors of the mind, for the reasons just stated.

 

Ps: What did you think of Ross's ontology (if you read it) as an analysis of how non-Euclidean geometry (as basic to relativity) developed?

Edited June 28, 2011 by owl

[mississippichem]

As admitted many times, I do not understand the advanced math, but I do understand the concepts of closer vs further away and that, in reality, the closer anyone (or anything) gets to the sun, or any other star (or hot object) the hotter it gets. It seems to me (and, I would argue, from the ontological perspective, inquiring into what is real here) that the complex physics in this case is mental magic, smoke and mirrors of the mind, for the reasons just stated.

 

I would hardly call the above example "advanced mathematics", definitely not elementary but not advanced. Special relativity has the great property of being able to be understood with relatively little (pardon the pun) math, when compared to general relativity. If you do not understand the above calculation, then you are really not qualified to make many statements about relativity. It doesn't bother me more than slight bewilderment, but you are doing yourself a huge disservice by trying to comprehend these things without the mathematics. It is analogous to trying to understand English literature while only speaking japanese, a hamster wheel type task.

 

Special relativity appears to be magical and mythical to you because you don't understand the mathematical foundation. The human brain is not capable of keeping track of all these factors qualitatively, no one is that intelligent and no one has that much computational power. That's why we have to use the mathematics to understand many of these complex problems of physical science. Cap'n Refsmmat's above calculation was all derived from first principles. Straight out of basic SR, Newton, and simple geometry (except for the Stefan-Boltzmann constant...yeah, yeah) where is the magic?

[Cap'n Refsmmat]

In other words, on the one hand you seem to agree that earth does not actually move closer to the sun, as length contracted measurements would have it. On the other hand, all that physics seems to be an argument for the opposite, i.e., that the 19 million km distance, as seen from the fly-by frame is accurate in 'the real world' and that, by the above "magic" somehow the heat diminishes with the shorter distance and time of exposure.

The point of relativity is that there's absolutely no problem with 150 million km and 19 million km being simultaneously true (in two different reference frames). If you arguing against relativity by saying "but it's 150 million km and that can't change!", you're essentially saying "nuh-uh" without basis.

 

Again, I do not deny that the voyager "will see the earth as being closer to the sun." But it still looks like a distortion effect of relativity to me. Same with earth's diameter. It does not shrink just because extremely high speed frames of reference from which it is measured make it look like a 1/8 sized mini-earth.

You're implying that the motion causes some force upon the Earth which shrinks it. That is not the case. In one reference frame the Earth is different than in the other reference frame. That's it.

 

As admitted many times, I do not understand the advanced math, but I do understand the concepts of closer vs further away and that, in reality, the closer anyone (or anything) gets to the sun, or any other star (or hot object) the hotter it gets. It seems to me (and, I would argue, from the ontological perspective, inquiring into what is real here) that the complex physics in this case is mental magic, smoke and mirrors of the mind, for the reasons just stated.

No. It is not smoke and mirrors. It's fairly easy to follow if you make the effort; let me demonstrate.

 

We can calculate how much energy the Earth receives from the sun by knowing (a) how much energy the Sun emits and (b) what fraction of that energy hits Earth. We can calculate (b) by imagining a large spherical shell whose radius is the same as Earth's orbital radius. The energy the Sun emits is spread equally over this shell, so we just have to find what portion of the surface area is taken up by Earth. That's what I did in my equations.

 

Now, length contraction only happens in the direction of travel. That spherical shell is not contracted into a smaller spherical shell -- it's contracted into an oblate spheroid, because only one dimension of it is contracted. The light traveling from the Sun at a given instant doesn't go outwards in a sphere -- it moves outward in the oblate spheroid shape because of length contraction.

 

So less extra light hits Earth than you'd expect, because of the oblate spheroid shape having so much surface area. It ends up working out to balance out the distance change.

 

Perhaps you could review my math in some detail and get back to me with specific questions on what you don't understand? It would be easier that way.

[swansont]

You're implying that the motion causes some force upon the Earth which shrinks it. That is not the case. In one reference frame the Earth is different than in the other reference frame. That's it.

There is one more thing: there is no physics experiment that will tell you one measurement is correct at the expense of any other. No objective way to claim that one measurement is reality and others are "distortion"

[Cap'n Refsmmat]

There is one more thing: there is no physics experiment that will tell you one measurement is correct at the expense of any other. No objective way to claim that one measurement is reality and others are "distortion"

Yeah, I should've drawn the parallel with my you-and-a-rock-in-empty-space example. After all, from someone else's perspective, the Earth is blazing past at a million miles a minute and is incredibly far from the sun, and we're all crazy for thinking otherwise.

[owl]

me:

As admitted many times, I do not understand the advanced math...

 

Cap ‘n R:

Perhaps you could review my math in some detail and get back to me with specific questions on what you don't understand? It would be easier that way.

 

Is this a snub from the assumption that math trumps conceptual understanding (ontology) and requires no explanation as to how it explains astronomical distances... and their thermodynamic and gravitational ... and mini-sized earth... consequences?

Are you consciously ignoring my statement above and just assuming that math is superior to ontology in the overall perspective and that the subject of the thread is irrelevant and subservient to the magical math/physics you just presented?

These are honest and sincere questions from my 'frame of reference.'

Please answer as honestly as you can.

 

I will study your reply in depth when I have "time", but you can not be seriously implying that relativity is the scientific version of subjective idealism* (see Hume and Berkeley) with the “subject” being “frame of reference”, by which everything shrinks and expands with high speed platforms of measurement.

 

*...Most briefly, that REALITY depends on perception/perspective, with no existence in and of itself (the objective cosmos which for which I always argue.) But of course this is philosophy of science... wrong section... and no one yet will put the thread where it belongs.

[Cap'n Refsmmat]

The assumption is that the mathematics explains the consequences. The same explanation could be written up in text, as I have attempted to do in summarized form in post #161, but if you follow the mathematics you will understand why this works.

 

Furthermore, I couldn't get from "it becomes an oblate spheroid" to "and so the energy is exactly the same" without using mathematics, since that kind of depends on the mathematical behavior of oblate spheroids.

 

Relativity does not advocate that "reality" depends on perception/perspective. It states that what you perceive to be the universe at this "instant" depends on your frame of reference.

 

Perhaps I can make a more satisfactory explanatory analogy for you. Imagine I have a movie camera and I am filming the motion of objects on a flat (two-dimensional) surface. I print each frame of the movie on transparencies (like for an overhead projector) with the objects in black and the background surface as transparent space.

 

Now I stack each frame of transparent film together to make a flipbook. If I flip open to a specific frame, I'm looking at the state of the objects at one specific point in time -- the time at which the camera captured that image. If I close the flipbook, I have a thick chunk of transparencies and I can look through and see objects at different points in time. Right?

 

Now I stick the transparencies in the oven so they all melt together into one block of plastic, retaining their shape and relative positions but stuck together as one.

 

Now I take a small guillotine and slice the transparencies into pages again, but at a slight angle. Each transparency has one instant's worth of objects on it, but it might have portions of objects from the frame before it or after it, since I cut at an angle.

 

So if I cut at different angles, I see different versions of the same motion, where different events occur simultaneously or not, in different sequences, and so on.

 

This is analogous to reference frames in relativity. However, if you want to extend the analogy to reference frames, you must use a camera that takes three-dimensional images, you must print them in three dimensions, and you must stack them together in the fourth dimension. You can see the difficulty in visualizing it.

[owl]

Cap 'n R:

you must stack them together in

the fourth dimension. You can see the difficulty in visualizing it.

Yes. More like the impossibility of "visualizing" a fourth spatial dimension, since three axes fully describe "space" as a 3-D matrix. (What direction is signified by a fourth axis?... not "time" as a fourth spatial dimension.))

This will make little sense until you understand the ontological debate about space and time.

I have provided links (many times) to the ontology of the spacetime debate. Little response. The International Society for the Advanced Study of Spacetime has presented many scientific/philosophical papers on the subject over the last decade of conferences on the subject. Mostly ignored as I have presented links in this forum.

 

I suggested that you read my favorite author on this Euclidean/ non-Euclidean debate, (as pertains to relativity) but you have not commented on the paper linked above. Too busy to read new information? I don't know. Just guessing. You must be busy as a science website administrator.

Please put this thread in the philosophy section where it can be formally ignored by physicists who don't care about the ontology of time.. or space.. or "spacetime."

Thanks.

[md65536]

In other words, on the one hand you seem to agree that earth does not actually move closer to the sun, as length contracted measurements would have it. On the other hand, all that physics seems to be an argument for the opposite, i.e., that the 19 million km distance, as seen from the fly-by frame is accurate in 'the real world' and that, by the above "magic" somehow the heat diminishes with the shorter distance and time of exposure.

 

Again, I do not deny that the voyager "will see the earth as being closer to the sun." But it still looks like a distortion effect of relativity to me. Same with earth's diameter. It does not shrink just because extremely high speed frames of reference from which it is measured make it look like a 1/8 sized mini-earth.

What you are talking about is known as "rest distance".

You are arguing that rest distance is more definitive of the concept of distance, than is relativistic distance.

You can argue for that, except that it leaves the distance between moving objects undefined, which is not very useful.

It might be okay for describing a static universe, or ideas that we've known for 100 years to be false.

 

In fact, all of your "ontological studies" seem to advocate a return to early 1800s understanding of time and space, back when the metre was defined as a fraction of the Earth's circumference. Your ontological arguments involve undoing 200 years of understanding and progress, but I don't see anywhere that they offer a means forward beyond what was known back then.

 

 

Edit: Erased discussion-stifling comments.

Edited June 29, 2011 by md65536

[swansont]

Yes. More like the impossibility of "visualizing" a fourth spatial dimension, since three axes fully describe "space" as a 3-D matrix. (What direction is signified by a fourth axis?... not "time" as a fourth spatial dimension.))

This will make little sense until you understand the ontological debate about space and time.

I think the opposite is true. People who study physics (and therefore math) can "visualize," or at least are not bothered by more than three dimensions and by understanding the physics, see the difficulties in the ontology arguments.

 

Not understanding the physics would tend to prevent one from seeing the problems, for example, the insistence that there is one frame that represents reality and other frames are distortions. Such a misunderstanding may make the meaning/nature of time seem clear, but since it is based on a misconception, the conclusion is invalid.

[Cap'n Refsmmat]

Indeed. I should hope that one's ontological inquiries are informed by accurate physics, rather than being based on an invented, more convenient version of physics.

[mississippichem]

I think the opposite is true. People who study physics (and therefore math) can "visualize," or at least are not bothered by more than three dimensions and by understanding the physics, see the difficulties in the ontology arguments.

 

Not understanding the physics would tend to prevent one from seeing the problems, for example, the insistence that there is one frame that represents reality and other frames are distortions. Such a misunderstanding may make the meaning/nature of time seem clear, but since it is based on a misconception, the conclusion is invalid.

 

That, and it is much easier to write down a matrix in 4-space, or to find a linear combination of 4-vectors than it is to try and visualize 4 dimensions. It would be faster to just take a linear algebra course than it would be to sit here now and try to visualize four dimensions. Our intuition is based on our experience. All our experience takes place in [math] \mathbb{E}^{3} [/math] at [math] \vec{v} <<c [/math] so intuition doesn't help much in relativistic situations. Once again math becomes the key to understanding. I could write a book...

 

Even though math seems cryptic to many, it really makes life much easier.

Edited June 29, 2011 by mississippichem

[owl]

Indeed. I should hope that one's ontological inquiries are informed by accurate physics, rather than being based on an invented, more convenient version of physics.

The reason I was trying to get you and the forum to read the ontology sources referenced above is because they do often focus on what seems "invented" about time, space, and spacetime since the non-Euclidean revolution in physics (and geometry and cosmology.)

 

For instance the fundamental departure from Euclidean geometry was based on tossing out his fifth postulate on parallel lines.

Can anyone here explain what it means to say that parallel lines do eventually intersect "in infinity?" I get that math can easily deal with the latter, but how is it that if those lines are extended far enough (to "infinity") that they do actually intersect (at which point they are no longer parallel lines, by definition?)

 

Maybe just a baby step at a time as above will get the focus back on ontology here. Then maybe someone will eventually answer how relativity convinces folks that a 1589 million km (1/8 the established figure) measure of earth's diameter, as measured from the near 'C' fly-by frame of reference, the "mini-earth" above is just as accurate as the well established 12756 million km polar diameter.

 

I just can't believe that anyone thinks earth shrinks to accommodate the "accuracy" of such a measure. If it does not, then the 12756 million km diameter is accurate, and the 1589 million km is in error.

[Cap'n Refsmmat]

For instance the fundamental departure from Euclidean geometry was based on tossing out his fifth postulate on parallel lines.

Can anyone here explain what it means to say that parallel lines do eventually intersect "in infinity?" I get that math can easily deal with the latter, but how is it that if those lines are extended far enough (to "infinity") that they do actually intersect (at which point they are no longer parallel lines, by definition?)

They are still parallel lines, by definition. They just have a different definition because we're not using Euclidean geometry.

 

Maybe just a baby step at a time as above will get the focus back on ontology here.

I think you need to understand the physics before you can approach the ontology and reach reasonable conclusions.

 

Then maybe someone will eventually answer how relativity convinces folks that a 1589 million km (1/8 the established figure) measure of earth's diameter, as measured from the near 'C' fly-by frame of reference, the "mini-earth" above is just as accurate as the well established 12756 million km polar diameter.

 

I just can't believe that anyone thinks earth shrinks to accommodate the "accuracy" of such a measure. If it does not, then the 12756 million km diameter is accurate, and the 1589 million km is in error.

Fortunately, physicists base conclusions on evidence rather than personal incredulity.

 

I have already explained that Earth does not "shrink" to "accommodate" measurements. There is no force applied. From the perspective of any single observer, the Earth does not change size, shape, or distance from the Sun. There are two fundamental principles: (1) From different frames of reference, the universe appears to be different. (2) All frames of reference are equally good.

 

(2) is true for the same reasons as the example I gave earlier about a rock in empty space. Furthermore, we might base our measurements of Earth's orbital radius from a perspective where the Sun is stationary, but it isn't -- it's moving. And the galaxy is moving. And other galaxies are moving. It's impossible to assign an absolute velocity to Earth, and because of length contraction and time dilation, it's impossible to assign absolute times. They're all determined by your choice of reference frame.

 

And of course (1) is true because we've tested relativity in almost every way we can think of and found it's right. Frame dragging, time dilation, gravitational lensing, and so on.

[swansont]

For instance the fundamental departure from Euclidean geometry was based on tossing out his fifth postulate on parallel lines.

Can anyone here explain what it means to say that parallel lines do eventually intersect "in infinity?" I get that math can easily deal with the latter, but how is it that if those lines are extended far

Longitudes are parallel at the equator — all are perpendicular to the equator — yet they intersect at the poles. That's what happens in a spherical geometry. You can't expect Euclidean postulates to necessarily hold in non-Euclidean geometries.

[owl]

swansont:

Longitudes are parallel at the equator, yet they intersect at the poles. That's what happens in a spherical geometry. You can't expect Euclidean postulates to necessarily hold in non-Euclidean geometries.

Lines that intersect are not parallel lines. Non-Euclidean geometry "re-invents" the meaning of parallel. Lines drawn on a sphere and intersecting at the poles (longitudinal lines) are not "parallel at the equator." They are widest apart at the equator and steadily converge until they intersect at the poles.

You might try actually reading Ross's paper on the Ontology and Cosmology of Non-Euclidean Geometry. The focus of this thread is, after all the ontology of time as an aspect of the ontology of relativity.

 

Cap ,n R;

They are still parallel lines, by definition. They just have a different definition because we're not using Euclidean geometry.

Parallel lines, by definition, do not intersect. Non-Euclidean geometry "re-invents" the definition of parallel lines... which was my point above as to who is re-inventing what in reply to your "inventing" comment.

I think you need to understand the physics before you can approach the ontology and reach reasonable conclusions.

 

Ontology is the inquiry into what exists in the real world, not just in the minds of mathematicians/physicists. I asked you, for instance, to explain what a fourth spatial dimension is in the real world, since the three axes of 3-space already have volume covered... a line being one dimensional, a plane being two dimensional, and volume (my understanding of space, being three dimensional. Ontology asks what referent a "fourth spatial dimension" has in the real world. You refuse to answer or explain. Math is not the explanation. Ross covers this in detail. Have you read him?

 

 

Fortunately, physicists base conclusions on evidence rather than personal incredulity.

 

As above, what is the evidence for a forth spatial dimension.

 

I have already explained that Earth does not "shrink" to "accommodate" measurements. There is no force applied. From the perspective of any single observer, the Earth does not change size, shape, or distance from the Sun. There are two fundamental principles: (1) From different frames of reference, the universe appears to be different. (2) All frames of reference are equally good.

 

Again (and again)... so which is the correct measurement of earth: the 1589 million km diameter mini-earth or the 12713 million km diameter earth, if "all frames of reference are equally good.

 

Do you think that there is any possibility that flying by at near light speed and depending on light to convey the image of earth might possibly distort the image to a 1589 million km diameter earth, or do you insist that the very small earth is an equally correct determination of earth's size. This is a valid ontological question. I am asking for a clear and straight forward answer. Same for the diminished distance between earth and sun and the obvious catastrophic consequences of a 1/8 AU distance, if "equally valid."

 

Your extensive math/physics reply totally avoided the ontological questions I keep raising here. The extensive equations you worked up do not address the reality questions above. The math does not address the meaning.

[Cap'n Refsmmat]

Again (and again)... so which is the correct measurement of earth: the 1589 million km diameter mini-earth or the 12713 million km diameter earth, if "all frames of reference are equally good.

They're both correct, in their respective frames of reference.

 

Do you think that there is any possibility that flying by at near light speed and depending on light to convey the image of earth might possibly distort the image to a 1589 million km diameter earth, or do you insist that the very small earth is an equally correct determination of earth's size. This is a valid ontological question. I am asking for a clear and straight forward answer. Same for the diminished distance between earth and sun and the obvious catastrophic consequences of a 1/8 AU distance, if "equally valid."

There is certainly interesting distortion that relativistic effects cause -- relativistic beaming, various weird bendy effects, and so on. But in relativity, length contraction is real, and the contracted earth is just as correct.

 

Parallel lines, by definition, do not intersect. Non-Euclidean geometry "re-invents" the definition of parallel lines... which was my point above as to who is re-inventing what in reply to your "inventing" comment.

Perhaps you would accept the possibility that Euclidean geometry, while very convenient for flat sheets of paper, does not in fact describe how the universe works?

 

As above, what is the evidence for a forth spatial dimension.

A popular interpretation of relativity has a fourth dimension as time -- not a spatial dimension but a temporal one, but connected with space nonetheless. Hence the term "spacetime." The mathematics that arises out of this is what has described the behavior of the universe so well.

[owl]

The following basic question has not been answered, and it is the take-off point for non-Euclidean geometry.

From post 166:

I get that math can easily deal with the latter, but how is it that if those lines are extended far enough (to "infinity") that they do actually intersect (at which point they are no longer parallel lines, by definition?)

 

Or, in a nutshell, what about extending parallel lines “far enough” makes them converge and intersect? (Ontology.)

 

Then, regarding a mini-earth as equally accurate with what I am calling the real, full sized earth:

Cap ‘, R:

They're both correct, in their respective frames of reference.

 

How is this different from the philosophy of subjective idealism (applied to relativity), as I asked before, referencing Berkeley and Hume?

Summary: There is no objective reality independent of perception/measurement from different reference frames. Perception/measurement creates reality.

An aside for illustration:

(Cliche' ref): "If a tree falls in the forest and no one hears it, does it make a sound?" Of course it makes sound waves in the air whether or not they strike human ears. And the actual at- site decibel level will not change with various distances from the tree from which it is measured.)

This is where ontology as part of the philosophy of science is absolutely relevant to the questions at hand.

 

A mini-earth of diameter 1/8 th “actual size” is just as correct as the size of the earth we all know and love? I really can’t imagine a more absurd assertion calling itself science.

 

But in relativity, length contraction is real, and the contracted earth is just as correct.

 

Regarding the previous conversation about whether length contraction applies to objects in the macro-world (beyond the subatomic results from particle accelerators): DrRocket said that a planned experiment on the above has not yet been done. Is your statement above based on faith alone or experimental evidence not yet published?

 

 

Perhaps you would accept the possibility that Euclidean geometry, while very convenient for flat sheets of paper, does not in fact describe how the universe works?

 

I hope you don’t actually believe that Euclidean geometry is confined to 2-D planes. So why dismiss it as if it were so confined?

 

A popular interpretation of relativity has a fourth dimension as time -- not a spatial dimension but a temporal one, but connected with space nonetheless. Hence the term "spacetime." The mathematics that arises out of this is what has described the behavior of the universe so well.

 

Actually, one faction in non-Euclidean geometry does assert this mystery forth spatial dimension. Yet it remains a concept without a referent in the “universe.”

I have no problem with 3-Space plus time as the movement factor as “it takes time” for stuff to move around in 3-D space.

Then there is malleable spacetime (as a math/physics *concept*) with time and space combining into something that gravity curves... that without a definitive answer to what either or both combined is in the first place. (Ontology. See reference sources earlier in the thread.)

Edited June 30, 2011 by owl

[Cap'n Refsmmat]

Or, in a nutshell, what about extending parallel lines “far enough” makes them converge and intersect? (Ontology.)

Curvature in space-time. It's analogous to swansont's analogy of parallel lines on the equator. One can mathematically imagine a universe which is ever-so-slightly curved, such that parallel lines remain parallel except when they travel exceedingly long distances.

 

How is this different from the philosophy of subjective idealism (applied to relativity), as I asked before, referencing Berkeley and Hume?

Summary: There is no objective reality independent of perception/measurement from different reference frames. Perception/measurement creates reality.

An aside for illustration:

(Cliche' ref): "If a tree falls in the forest and no one hears it, does it make a sound?" Of course it makes sound waves in the air whether or not they strike human ears. And the actual at- site decibel level will not change with various distances from the tree from which it is measured.)

This is where ontology as part of the philosophy of science is absolutely relevant to the questions at hand.

Perception and measurement do not "create" reality in relativity, though one may argue the point in quantum mechanics. Reality is merely different in different reference frames.

 

The trouble with using the word "reality" is that it implies there is one absolutely correct version of how the universe is, and anything which diverges from that is invalid. That is a faulty assumption.

 

A mini-earth of diameter 1/8 th “actual size” is just as correct as the size of the earth we all know and love? I really can’t imagine a more absurd assertion calling itself science.

That's not an argument.

 

Also, you must have missed the bits when I explained that it only appears to shrink in one axis, so it's not simply 1/8th the diameter.

 

Regarding the previous conversation about whether length contraction applies to objects in the macro-world (beyond the subatomic results from particle accelerators): DrRocket said that a planned experiment on the above has not yet been done. Is your statement above based on faith alone or experimental evidence not yet published?

Length contraction falls out of relativity as a natural consequence, and many of the principles required have been tested.

 

Particularly interesting are tests of time dilation, since in relativity, time dilation in one frame is length contraction in another. Time dilation is explained through length contraction in the reference frame of the dilated object.

 

I hope you don’t actually believe that Euclidean geometry is confined to 2-D planes. So why dismiss it as if it were so confined?

Because there is no reason to assume that the universe must behave according to Euclidean rules. It is quite plausible that the universe is fundamentally curved, for instance, such that two parallel lines eventually intersect and then wrap around to their starting places.

 

Then there is malleable spacetime (as a math/physics *concept*) with time and space combining into something that gravity curves... that without a definitive answer to what either or both combined is in the first place. (Ontology. See reference sources earlier in the thread.)

Physicists tend not to care what things like time and space really "are," since it has no bearing on our understanding of physical phenomena. What time "is" cannot be determined by experiment. How time behaves, whatever "time" might be, can be.

[owl]

Back later with a full reply.

Just a quick reply to your last statement:

 

Physicists tend not to care what things like time and space really "are," since it has no bearing on our understanding of physical phenomena. What time "is" cannot be determined by experiment. How time behaves, whatever "time" might be, can be.

 

That is why this thread belongs in the philosophy of science department as the ontological inquiry it is. I've asked and practically begged, just because it is what it is, ontology. "Thanks" for nothing.

 

Even saying "How time behaves..." assumes that everyone already knows what time is! "It" doesn't "behave" at all if it is, as I've argued simply the event duration of physical processes. They "behave" by slowing down and speeding up in various environments. That does not make time something which expands (dilates.) That, however is about the ontology of time... the subject of this thread, if reminders are required.

[Cap'n Refsmmat]

That is why this thread belongs in the philosophy of science department as the ontological inquiry it is. I've asked and practically begged, just because it is what it is, ontology. "Thanks" for nothing.

As I've said, you're bringing up questions of physics and doubting accepted theory, you can't move onto the philosophy until that's resolved.

 

Even saying "How time behaves..." assumes that everyone already knows what time is! "It" doesn't "behave" at all if it is, as I've argued simply the event duration of physical processes. They "behave" by slowing down and speeding up in various environments. That does not make time something which expands (dilates.)

If time is just EDPP, than physics just measures how EDPP behaves. It doesn't really matter. We're limited to what can be empirically observed, and at the present that does not include the nature, or lack thereof, of time.

[swansont]

That is why this thread belongs in the philosophy of science department as the ontological inquiry it is. I've asked and practically begged, just because it is what it is, ontology. "Thanks" for nothing.

 

I would like to remind you that "this thread" originated as a hijack of a science thread and as Cap'n just pointed out, you keep bringing up science (and keep getting it wrong). If you had wanted to discuss philosophy, you could have started a thread on it there, but you chose another path. Stop pretending that this is somebody else's doing.