Photon?

[Farsight]

1. Farsight asserts that "a field is a state of space"

Yes. See Einstein talking about it here: "The two types of field are causally linked in this theory, but still not fused to an identity. It can, however, scarcely be imagined that empty space has conditions or states of two essentially different kinds, and it is natural to suspect that this only appears to be so because the structure of the physical continuum is not completely described by the Riemannian metric."

2. Farsight admits that "a state of space" is given by a symmetric spacetime metric tensor whose matrix representation has only 10 independent components

That's what Einstein said.

I assume the self-evidently true propositions

3. "Flat spacetime" has a metric that has only 4 non-zero components (in its matrix representation) {this is the so-called Minkowski metric}

4. A metric with 10 non-zero independent components describes "non-flat" spacetime

5. The field in 1) above is the gravitational field

Conclusion - the exact equivalence between the gravitational field and non-flat spacetime.

What's so hard about that?

Nothing. And there's nothing hard about the plot of potential that has to be curved to get off the flat and level. But your pencil doesn't fall down because "the spacetime in the room you're in is curved". Or because "the space in the room you're in is curved". So why does it? Come on Quackhead, we're nearly there. One last push.

 

[paddoboy]

No it doesn't. And you will not find Einstein saying that.

Yes they do. Light/photons always follow geodesics in curved spacetime.
Einstein said a lot of things, mostly still true today, and mostly misinterpreted and taken out of context by you.

 

[QuarkHead]

Nothing. And there's nothing hard about the plot of potential that has to be curved to get off the flat and level.

Note that what you are gaily calling "a plot" has at least 2 elements - the dependent and the independent. To what does your "plot" refer.

Recall that you stated in this thread and in others that spacetime curvature "relates" to the tidal force (whatever that means), whereas gravitation "relates" to the "state of space".

I showed that you are confused at best and corrected you

I regard my task here as finished

Come on Quackhead,

Ya know, on most science/math fora I know of, mutating a member's screen name in a derogatory manner is a banning issue. Not here apparently

 

[Farsight]

Note that what you are gaily calling "a plot" has at least 2 elements - the dependent and the independent. To what does your "plot" refer.

Light clock rates. Come on Quarkhead, I've told you about this enough times. Surely you've read Gravity Works Like This. You place light clocks throughout an equatorial slice of space. The clocks nearer the Earth run faster. Plot your clock rates, and you depict Riemann curvature.

Recall that you stated in this thread and in others that spacetime curvature "relates" to the tidal force (whatever that means), whereas gravitation "relates" to the "state of space". I showed that you are confused at best and corrected you.

No you haven't. When we started these lessons, you didn't even know the difference between spacetime and space.

I regard my task here as finished.

Not until you answer the question. Your pencil doesn't fall down because "the spacetime in the room you're in is curved". Or because "the space in the room you're in is curved". And you know there's no motion in spacetime. So come on Quarkhead, why does your pencil fall down?


PS: as for derogatory, may I remind you of this. If you can't take it, don't dish it.

 

[PhysBang]

Light clock rates. Come on Quarkhead, I've told you about this enough times. Surely you've read Gravity Works Like This. You place light clocks throughout an equatorial slice of space. The clocks nearer the Earth run faster. Plot your clock rates, and you depict Riemann curvature.

If this is the case, please show us with the relevant mathematics. Riemann curvature is an element of mathematics.

So come on Quarkhead, why does your pencil fall down?

Farsight, you seem to forget that I asked you this question and you refused to answer it. Anyone who merely uses Newtonian mechanics can explain the fall of a pencil in mathematical detail, far more than you apparently can do.

Of course, I am not surprised that you dodged the issue of your mistake about Einstein and geodesics.

 

[paddoboy]

No you haven't. When we started these lessons, you didn't even know the difference between spacetime and space.

For all intents and purposes, space is the same as spacetime.
The views of space and time which I wish to lay before you have sprung from the soil of experimental physics, and therein lies their strength. They are radical. Henceforth space by itself, and time by itself, are doomed to fade away into mere shadows, and only a kind of union of the two will preserve an independent reality. – Hermann Minkowski, 1908

Not until you answer the question. Your pencil doesn't fall down because "the spacetime in the room you're in is curved". Or because "the space in the room you're in is curved". And you know there's no motion in spacetime. So come on Quarkhead, why does your pencil fall down?

http://www.askamathematician.com/2010/12/q-why-does-curved-space-time-cause-gravity-a-better-answer/
The curvature of space alone has almost no effect on the movement of objects until they are moving really fast. With the exception of only the most extreme cases (black holes), space is very, very close to flat. For example, the total stretching of space due to the Earth amounts to less than 1cm. The precession of Mercury’s orbit is another example of the tiny effect of the curvature of space (and it is tiny). Literally, there’s a little more space near the Sun than there “should” be, and as a result the direction in which Mercury’s orbit is elliptical moves. It takes a little over 3 million years for it to go full circle.

In almost all cases the vast majority of an object’s movement is tied up in its forward movement through time. The curvature of spacetime (not just space) is responsible for gravity. Literally, near heavy objects, the “future direction” points slightly down. So anything that moves forward in time will find its trajectory pointing down slightly. This takes the form of downward acceleration. This acceleration (time pointing slightly down) is entirely responsible for the motion of the planets, and every other everyday experience of gravity.
http://www.askamathematician.com/2010/12/q-why-does-curved-space-time-cause-gravity-a-better-answer/

 

[OnlyMe]

PS: as for derogatory, may I remind you of this. If you can't take it, don't dish it.

If you did not hide your links it might be easier to sus out what you refer to. If what you were referring to was the word, moron.., while it can be either descriptive or derogatory, it is not the same as intentionally altering a screen name as you did!

Farsight, it seems to me you do as much if not more of the former kind of name calling as anyone else, so it would not seem to be something you can complain about. Again, changing a screen name in a derogatory manner.., that is a whole different level of childish behavior. There it is.., childish can also be a descriptive or derogatory comment. Here I think of it as descriptive!

 

[Dr_Toad]

It seems to be very difficult for the moderators to remove this obscenity. I was awarded 5 infraction points for speaking the truth, so be careful! Idiocy seems to be protected here. Or maybe it just cries to moderators every time its garbage is rejected by the thinking few...

By the way, how can we see our infractions? I can find no links in my profile or elsewhere.

 

[Beer w/Straw]

Maybe I should start asking physics questions.

I'm a student.

 

[Dr_Toad]

As we all are, if we wish to find wisdom.

 

[quantum_wave]

No, I can't rule it out. But I can tell you that Ethan has a bit of a habit of presenting speculation as hard scientific fact, and he doesn't engage with anybody who points this out.

I've been reading up on the CMB dipole and what they call hemispherical anisotropy. There are many papers, and I can only really understand parts, so when I found the following article in layman's language, I thought I would pass it on. It confirms the wide angle anomaly from WMAP and Planck surveys, and expresses the consensus that it is as yet unexplained:

Sky and Telescope
http://www.skyandtelescope.com/astronomy-news/planck-best-map-yet-of-cosmic-creation/

Findings:

"The universe isn’t as uniform on the largest scales as expected. Previous work had hinted that the northern and southern hemispheres of the sky don’t look as much like each other (statistically speaking) as they should, and that there’s an anomalous cool spot in the CMB. (Anomalous in terms of shape, not temperature or overall size). Planck upholds these results. Furthermore, you get slightly different values for the fundamental six parameters when you fit each half of the sky separately. Assuming these effects are real, they may hint at unpredicted structure that's larger than our cosmic horizon and originating before inflation, even before the Big Bang."

 

[Farsight]

I remember reading something about this. See Planck's Mystery Cosmic 'Cold Spot' Could be an Error:

"One of the more exotic explanations for the cold spot is that it could be observational evidence for the “multiverse” — a hypothesis with roots in superstring theory where our universe exists in an ocean of other universes — and the cold spot is caused by a neighboring universe pushing up against ours. Unfortunately, the feature might not even be real".

 

[Farsight]

For all intents and purposes, space is the same as spacetime.

Wrong. See Quarkhead, who will tell you that there's no motion in spacetime. Yes yes, we've all seen the Minkowski quote, but sadly he died before he could restate his view. We can see space and motion. We can't see time. A clock "clocks up" some kind of regular cyclical motion.

http://www.askamathematician.com/2010/12/q-why-does-curved-space-time-cause-gravity-a-better-answer/
The curvature of space alone has almost no effect on the movement of objects until they are moving really fast. With the exception of only the most extreme cases (black holes), space is very, very close to flat. For example, the total stretching of space due to the Earth amounts to less than 1cm. The precession of Mercury’s orbit is another example of the tiny effect of the curvature of space (and it is tiny). Literally, there’s a little more space near the Sun than there “should” be... In almost all cases the vast majority of an object’s movement is tied up in its forward movement through time. The curvature of spacetime (not just space) is responsible for gravity. Literally, near heavy objects, the “future direction” points slightly down...

Paddoboy, this is abject trash. If you don't believe me, go and present this explanation elsewhere and ask them if it's right. You'll get short shrift.

 

[CHRIS.Q]

I think the photon energy will not be reduced, because the quality is zero
So no matter under any conditions, .................

 

[quantum_wave]

I remember reading something about this. See Planck's Mystery Cosmic 'Cold Spot' Could be an Error:

"One of the more exotic explanations for the cold spot is that it could be observational evidence for the “multiverse” — a hypothesis with roots in superstring theory where our universe exists in an ocean of other universes — and the cold spot is caused by a neighboring universe pushing up against ours. Unfortunately, the feature might not even be real".

As a layman, and in regard to a lot of layman level research in the last couple of days, from the papers I am reading, there are several avenues under study, but the issues of wide angle (hemispherical) asymmetry still seems to concern some professionals. Look at all the papers since 2013 that address the WMAP/Planck data. Those corrections to remove the wide angle anisotropies often skew the small angle date beyond recognition.

Of course there is the peculiar velocity, and how to accurately quantify it relative to the rest frame of the CMB, distant galaxies, relative redshift, Hubble's constant, etc. Then there is the masking used to mask out things like the plane of the Milky Way and large sturcture, dust, etc. Also there is the issue of the small angle anisotropy that is disproportionately affected by the sharp edges of the masking, which when smoothed can eliminate some of the anomalies at the larger angles. When all of these things are quantified, after a series of "if this, then that", the dipole asymmetry and cold spot can be explained away with, they say, 95% confidence.

I'm still working on getting and keeping up with the latest consensus, but my guess is that there is more data that has to be analyzed, and future sky surveys that might bring new data, so I will keep looking over time. There is the old saying, "What you see is what you get", but we must keep asking ourselves how we define "seeing".

The bottom image and the second from the bottom are the same data, smoothed for all the adjustments. The large scale anomalies are highlighted in the second from the bottom image, to show that there is still some remnant of them in the smoothed data, as I understand it.

 

[quantum_wave]

There seems to be a consensus that there are unexplained anomalies in the data from WMAP and Planck. This supports the possibility that there were preconditions to the Big Bang. It is certainly worth keeping an eye on.

From Physics Forums thread:
https://www.physicsforums.com/threads/cmb-hemisphere-of-evil.685850/#post-4980290
Today at 6:31 PM #10
bapowell

NEW
TEFLing said: ↑
That seems very interesting and potentially important

Would you elaborate ?
bapowell said:
There are several curious statistical anomalies in the CMB temperature spectrum which have been explored over the last decade or so in many, many papers. The best place to go for an update is probably the 2013 Planck release: http://www.aanda.org/articles/aa/abs/2014/11/aa21534-13/aa21534-13.html.

Abstract

The two fundamental assumptions of the standard cosmological model – that the initial fluctuations are statistically isotropic and Gaussian – are rigorously tested using maps of the cosmic microwave background (CMB) anisotropy from the Planck satellite. The detailed results are based on studies of four independent estimates of the CMB that are compared to simulations using a fiducial ΛCDM model and incorporating essential aspects of the Planck measurement process. Deviations from isotropy have been found and demonstrated to be robust against component separation algorithm, mask choice, and frequency dependence. Many of these anomalies were previously observed in the WMAP data, and are now confirmed at similar levels of significance (about 3σ). However, we find little evidence of non-Gaussianity, with the exception of a few statistical signatures that seem to be associated with specific anomalies. In particular, we find that the quadrupole-octopole alignment is also connected to a low observed variance in the CMB signal. A power asymmetry is now found to persist on scales corresponding to about ℓ = 600 and can be described in the low-ℓ regime by a phenomenological dipole modulation model. However, any primordial power asymmetry is strongly scale-dependent and does not extend toarbitrarily small angular scales. Finally, it is plausible that some of these features may be reflected in the angular power spectrum of the data, which shows a deficit of power on similar scales. Indeed, when the power spectra of two hemispheres defined by a preferred direction are considered separately, one shows evidence of a deficit in power, while its opposite contains oscillations between odd and even modes that may be related to the parity violation and phase correlations also detected in the data. Although these analyses represent a step forward in building an understanding of the anomalies, a satisfactory explanation based on physically motivated models is still lacking.

 

[Beer w/Straw]

Physics Forums is bullshit people telling wrong answers and pretending to be smart.


PUKE!

 

[Dr_Toad]

Sometimes, so is this...

 

[Farsight]

There seems to be a consensus that there are unexplained anomalies in the data from WMAP and Planck. This supports the possibility that there were preconditions to the Big Bang. It is certainly worth keeping an eye on...

Agreed. All I'd say is don't get so preoccupied by this such that you end up ignoring the easy stuff.

 

[Beer w/Straw]

Just what is the easy stuff?