Speed of light

[JimJast]

... Nature does not see any forces acting in the univese causing those movements. It sees only forces like those that press us against the Earth, but not any moving the Earth around or a stone thrown into the air. ...

Huh?!

You think there is a force pressing "us" to the earth, but that this force does not have any effect on a stone thrown into the air?

OMG!

Strange, Isn't it? Even stranger is the fact that Einstein discovered it almost a century ago (in 1915) and it is still not taught neiter in high schools nor even in graduate physics courses in universities (that's why "physicists don't understand gravitation"). One has to take a postgraduate two semeter general relativity course to learn physics that is detectable to all living organisms as "gravitation". Since you are surprised by this "strange" behavior of nature, and I took such a GR course, I'm trying to explain this physics to you. If you don't catch something, ask.

First of all it is not quite true that the free falling stone does not feel gravitational force. If its greater than just a point if feels the weight of its parts, but it is so small that for the purpose of this explanation we may threat it as negligible (not worth talking about). So we may start the story from noticing that (small) stone does not feel any forces when it is free falling (except when it is moving and then it feels the air resistance but no "gravitational force"). So why it is moving at all?

The reason is so called "gravitational time dilation". It is an effect of time running slower near some mass, like eg. near the Earth. When time runs slower all the particles of any given object move slower inside it. Shake slower and rotate slower, and as a result the object contains less energy, it has smaller internal energy. Now, any object if left alone always moves to its position of smaller energy, with speed limited only by its inertia, until it hits some obstacle that has enough strength to stop the object from moving. Usually it is the surface of the Earth (that's why everything tries to fall on Earth). And if those objects are us, we are pressed against the surface of Earth with a force that is called "gravitational force".

A stone which is free, thrown into the air, keeps moving. It doesn't feel any force that we are feeling walking on the surface of Earth (until the stone too hits something and stops moving). So you may see that "gravitational force" is a force that show up only when an object is immobilized by some obstacle from following its natural path of free movement. And it is a force that pushes the object with its inertia against the obstacle.

That's why it is not an attractive force as people imagined before Einstein but an inertial force coming from "gravitational time dilation". A relativistic effect, part of "curvatures of spacetime" (there is also an effect of curvature of space involved adding half of the force to this effect but I hope this explanation is enough to see how Einstein's gravitation works). Do you think it is too complicated to explain it in school instead of pretending that there is a "fundamental gravitational force" acting at a distance through vacuum as it is done now in all schools now?

[JimJast]

Scientists from the Evangelical Center For Faith-Based Reasoning are now asserting that the long-held "theory of gravity" is flawed

[The Code]

I read it again... and had to delete my post..... thanks for the info jim jast

mark

[rstevenson]

Thanks for the explanation JimJast. I have two thoughts about it:

1. I think you have simply redefined pull as push. That is, you've said that there is not something pulling us down by acting at a distance, but there is something pushing us down by acting at a distance. Redefining words is a clever way to debate but is not very helpful in the long run.

2. I think there are things which cannot be adequately explained in a spoken language like English. Gravity is surely one of those things which require the use of mathematics to say anything sensible and accurate and reliable. Trying to reduce the equations (whether you call them math equations or physics equations) to a spoken language is not going to work very well, because of the slippery nature of langauage where words can be redefined to mean almost anything (as you just proved so marvellously.)

Please be aware that I don't mean that your explanation is wrong in any cosmic sense, only that it does not actually explain anything. To take a different example: if you and I were moving away from each other without any visible reference frame, we could express in words our opinion that one of us is moving and the other is not, but it would not change the reality one bit, nor would it adequately explain the reality to a third party. Only an equation could do that.

Rob

[astrolabe]

Hello JimJast,

This, I do believe, is the first time that your arguments have become clear. I read EVERYONE'S post and I read them carefully. It's the only way because sometimes responses indicate that a mind set has not allowed a poster to understand a point and so responds incorrectly because of misinterpreting the comment. I have been guilty of that very fault in the past and have learned my lesson sometimes the hard way but now at least (for the most part) members don't have to repeat themselves in order to clarify for poor ole' astrolabe whose only downfall lies in trying to catch up. Also the original subject posted may be stated as to be somewhat muddy and some replies miss the mark for lack of precision at the outset of the thread.

I experienced the latter with you, not for lack of your passion, but because the math was beyond me and your (Einstein's) gravitation concept was moving to quickly. That is not to mean I think it incorrect! Your post actually is a welcome relief in that I was beginning to think I was failing at some key point in your dialog and for some reason couldn't quite put it together. Almost as if this, to me anyway, should've been your first post introducing the gravitation/time dilation idea. It's like steam heating systems where high pressure goes to low pressure ALWAYS in an attempt for water molecules to gain rest. I now have a much firmer image to run with and so needless to say- Thank you.

[astrolabe]

Hello rtstevenson,

I think you have simply redefined pull as push. That is, you've said that there is not something pulling us down by acting at a distance, but there is something pushing us down by acting at a distance. Redefining words is a clever way to debate but is not very helpful in the long run.

Sorry to be piping up here but I don't necessarily agree. If I was to consider a black hole as an object that was in the most restful state as opposed to the most gravitationally vigorous it would not be the same thing. I don't get the impression that something is pushed to a state of rest, it can, however, fall to that state as bodies and their constituent parts lose energy; by emitting heat or light or some other method. It would not require any action from a distance except the idea of falling into the deepest "well" in the locale.

[astrolabe]

Hello JimJast,

Can the idea be carried to something like a permanent magnet even though free falling bodies and magnetism are not the same thing?

[The Code]

So is gravity a finger print from each layer from What came before? which can not be removed from each kind of matter?

1 A Gold particle is its gravitational mass because of where it was created deep inside a star? and that force takes a long time to leave it?

2 A helium particle was created in a different way which makes gravity act in a different way on it?

3 Or are we talking speed round the nuke? The particles different speed round the nuke has the difference? *

Mark

[astrolabe]

Hello mark swain,

Good questions all! I think though at the quantum level which, like most everything else is not my strong suit, the idea of gravitation gets a different twist to it. For instance, a helium particle and a gold particle on the periodic table are, as you already know, at opposite ends, helium being the lighter of the two by far; hydrogen vs. lead being another example. The number of protons and neutrons in the respective nucleii are the deciding factors that result in the various atomic wts. Bonding of atoms of course coming from the sharing of electrons between atoms (valences). Having said that, I was wondering if gravity was what you meant in your sample questions because it would seem that strong force/weak force would be more at work at the QM level where particles are discussed. I also may be missing the essence in your post entirely in which the late Gilda Radner would say- Nevermind.

[harry]

G'day from the land of ozzzz


I think if you read up on
P process
S process
R process

Wikipedea is good for a start

as to the formation of the elements

I'm off to pick up the kids

Be back later if you want futher information.

Don't blame it on the rain for the reading. Its Nereid's fault for directing me to read more.

[harry]

G'day from the land of ozzzzzzzz

On the impact of intergalactic dust on cosmology with type Ia supernovae

http://arxiv.org/abs/0903.4199

Authors: Brice Ménard, Martin Kilbinger, Ryan Scranton
(Submitted on 25 Mar 2009 (v1), last revised 27 Mar 2009 (this version, v2))

Abstract: Supernova measurements have become a key ingredient in current determinations of cosmological parameters. These sources can however be used as standard candles only after correcting their apparent brightness for a number of effects. In this paper we discuss some limitations imposed by the formalism currently used for such corrections and investigate the impact on cosmological constraints. We show that color corrections are, in general, expected to be biased. In addition, color excesses which do not add a significant scatter to the observed SN brightnesses affect the value of cosmological parameters but leave the slope of the color-luminosity relation unchanged.
We quantify these biases in the context of the redshift-dependent dust extinction suggested by the recent detection of intergalactic dust by Menard et al. (2009). Using a range of models for the opacity of the Universe as a function of redshift, we find that color-magnitude-stretch scaling relations are virtually insensitive to the presence of cosmic dust while cosmological parameters such as Omega_M and w are biased at the level of a few percent, i.e. offsets comparable to the current statistical errors.
Future surveys will be able to limit the impact of intergalactic extinction by observing at larger wavelengths. In addition such datasets will provide direct detections of intergalactic dust by cross-correlating SN colors and the density of foreground galaxies, which can be used as a consistency check on the cosmic dust extinction correction. Alternatively, such biases could be avoided by correcting the colors of supernovae on an object-by-object basis with accurate photometry.

How accurate is Redshift data?

Its kind of funny that everything is expanding from one point called Earth as per the Reshift Data.

What common error could give us such a result?

How could top scientists make such an error?

If it is an error.

[harry]

G'day from the land of ozzzzzzz

"IF" was initiated and seeded by an observer seeing Steven Hawking falling.

From there on it has become more religion than science.

Hey! Most of the world is religious.

[makc]

Do you think it is too complicated to explain it in school instead of pretending that there is a "fundamental gravitational force" acting at a distance through vacuum as it is done now in all schools now?

yeah.

[neufer]

While free falling stones don't actually feel gravity they do have a intuitive "6th sense" about it.

[JimJast]

1. I think you have simply redefined pull as push. That is, you've said that there is not something pulling us down by acting at a distance, but there is something pushing us down by acting at a distance.

It isn't just redefining pull acting at a distance as push acting at a distance since the push is not acting at a distance. It is push from within the stone itself at the place where the stone is right now. It is stone's own diminishing energy that pushes it down its path. Stone's internal energy is not acting at a distance. There are also a subtle differences in predictions of Newtonian mechanics and Einstein's mechanics and physicists checked many of them and (as Feynman said) "whenever the predictions o Einstein have been found to differ from ideas of Newtonian mechanics Nature has chosen Einstein's".

Additional comment:

The Newton's math can't answer a question "what and how pulls things towards the Earth through vacuum?". Impossibility to answer this question made Newton opposing the possibility that his theory explains physics of gravitation. So Newton didn't believe in "Newtonian pull" since he (as Einstein as well) didn't believe in action at a distance. He believed only in possibility that something may be pushed by something else and he didn't see what might be pushing things towards the Earth. To make something that he could understand he invented an idea of "gravitational energy" that is diminishing somehow along the stone's path, pushing it along it's path, but it was an ad hoc idea without any physical backup. So for centuries physicists used this mysterious "gravitational" (a.k.a. "potential") energy without knowing where it actually is located. Only Einstein, by explaining the mechanism of gravitation through curvatures of spacetime (time dilation and the curveture of space) gave this mysterious "gravitational energy" a concrete physical meaning.

So in the real world there is no action at a distance which made Newton non believing in physicality of his own equations. It is important since nowhere else we observe action at a distance. That's why physicists think that action at a distance is not possible at all. Bad news for all who believe in supernatural being acting at a distance. And that's why Einstein called action at distance "spooky". The gravitation was the last suspected case of action at a distance and that's why it bothered Einstein so much that he tried to explain it, since he didn't believe that math is enough to explain physics. As the matter of fact he didn't believe that math is any good for explanation of physics. He even said: You do not really understand something unless you can explain it to your grandmother. And Faynman said: "Let me also say something that people who worry about mathematical proofs and inconsistencies seem not to know. There is no way of showing mathematically that a physical conclusion is wrong or inconsistent. All that can be shown is that the mathematical assumptions are wrong. If we find that certain mathematical assumptions lead to a logically inconsistent description of Nature, we change the assumptions, not nature."

2. I think there are things which cannot be adequately explained in a spoken language like English. Gravity is surely one of those things which require the use of mathematics to say anything sensible and accurate and reliable. Trying to reduce the equations (whether you call them math equations or physics equations) to a spoken language is not going to work very well, because of the slippery nature of langauage where words can be redefined to mean almost anything (as you just proved so marvellously.)

I hope that after reading the additional comment above, especially remarks of Einstein about the grandmother (who presumably does not know any math) and Feynman about the value of math in physics your opinion on those matters might have changed so I won't comment any more, just wait what concrete arguments you may show to oppose the above opinions. Only then I'll try to argue against your opinon with which I don't agree.

[JimJast]

While free falling stones don't actually feel gravity they do have a intuitive "6th sense" about it.

This "6th sense" is called "quantum mechanics".

[JimJast]

Hello JimJast,

Can the idea be carried to something like a permanent magnet even though free falling bodies and magnetism are not the same thing?

It can be carried as fas as "magnetic energy" is concerned since any energy included into E=mc^2 counts, but you might mean something else, and then I don't know what it is.

[JimJast]

So is gravity a finger print from each layer from What came before? which can not be removed from each kind of matter?

1 A Gold particle is its gravitational mass because of where it was created deep inside a star? and that force takes a long time to leave it?

2 A helium particle was created in a different way which makes gravity act in a different way on it?

3 Or are we talking speed round the nuke? The particles different speed round the nuke has the difference?

In gravitation it doesn't matter what things are included in the energy of the particle since this energy (its E=mc^2) that is seen outside of the particle depends only on its m (regadless of where and the kind of way it was created in, and what is speed of whatever around its nuke).

[Chris Peterson]

How accurate is Redshift data?

Extremely accurate. Spectral measurements are essentially absolute- you measure the wavelength of known peaks. There is really no opportunity for error in doing this (other than a small statistical measurement error). What is less accurate is the corroborating distance measurement, which is usually based on standard candles. When you measure intensity, you have things that can introduce errors, such as absorption of light, scatter of light, or simply failing to understand the physics sufficiently well to know what the intrinsic brightness actually is. The paper you linked is suggesting that the most common sources of error, absorption and scatter, only have small effects, and that they can be compensated for. So this paper adds support for the current redshift/distance relationship.

Its kind of funny that everything is expanding from one point called Earth as per the Reshift Data.

What is funny about it? This is exactly what the best supported cosmology model predicts. However, it would be more accurate to say that everything is expanding from any point. The way you've stated it makes it sound as if an observer somewhere else in the Universe would see something different, which isn't the case.

What common error could give us such a result?

Nothing comes to mind.

How could top scientists make such an error?

What error?

[JimJast]

Please be aware that I don't mean that your explanation is wrong in any cosmic sense, only that it does not actually explain anything. To take a different example: if you and I were moving away from each other without any visible reference frame, we could express in words our opinion that one of us is moving and the other is not, but it would not change the reality one bit, nor would it adequately explain the reality to a third party. Only an equation could do that.

The point is that an equation is only as good as our understanding of the situaton. And our understanding we are better able to explain to our grandma. If we can't it means that we don't understand the situation, just pretend understanding and describing it with an equation which we don't know how to explain So the conclusion is that first we understand something with just a back-of-envelope math then we describe it with math. Not the other way around.

E.g. Misner, Thorne, and Wheeler's "Gravitation" uses over 1200 pages of math to convince us that the universe is expanding. What if it is not for one of the reasons that thay overlooked? Which can be stated with 3 words after some astronomer does some relieble onservaton or someone finds an error in this sophisticated math. Then all 1200 pages of very sophisticaed math, times number of books sold around the world, are good for nothing.

Since one can't prove anything with math (see Feynman quote), but one may prove with one sentence in plain English that this math is wrong. That's why physicists don't believe in math and rather try to falsify any silly statements by inventing physical principles that when violated disqualify any math based on their violation. Since checking the math against principles takes much less effort than trying to understand some silly math. And that's why one does not need to understand any theory to be able to abolish it. That's why Patent Office didn't allow patenting perpetual motion machines. And yet very sophisticated math of MTW book relies on possibility of constructing such machines. Imagine the feelings of Patent Office clerks.

[JimJast]

Do you think it is too complicated to explain it in school instead of pretending that there is a "fundamental gravitational force" acting at a distance through vacuum as it is done in all schools now?

yeah.

Which part is too complicated?

[makc]

what can be easier than "it moves because a force makes it to"? a = f / m?

[JimJast]

what can be easier than "it moves because a force makes it to"? a = f / m?

This is easy, but the tough part is "where is this force coming from?" It took a lot of time to find out. In the meantime it was even thought that angels (invisible of course) are pushing the planets around. It was even easier but not everybody was happy with such a solution. People for some reason like to know the truth. And luckily Einstein was thinking hard enough to discover it otherwise we might not know till today.

[bystander]

If free falling objects don't feel gravity, what caused that apple to hit Newton in the head?

[BMAONE23]

If the "Free Falling Apple" isn't aware of gravity during it's fall, it will become painfully aware of it during it's sudden stop at the bottom.