Photon?

[PhysBang]

You do talk some nonsense PhysBang. The issue I was hinting at is that SR is built on two postulates, one of which is the speed of light is constant. But Einstein retracted that when he was doing GR, see this for example. The speed of light is NOT constant. If it was, light wouldn't curve and your pencil wouldn't fall down.

So you exactly agree with my analysis!

All: now PhysBang will squawk "cherry picking" and "out of context" and try and get you to dismiss and ignore what Einstein said. Bizarre.

On the contrary, I urge you all to read what Einstein wrote, including the mathematics. There one will find how Einstein intended his theory to be used and exactly how Einstein intended us to determine the speed of light.

I also urge you to read Farsight's details on how to use the speed of light and its changes to calculate the trajectory of a falling object. Then you can compare this to measurements of falling objects to see how his ideas compare to the world as observed. If you can't find Farsight's details, please ask him, I'm sure he will happily provide you with the evidence you need.

 

[quantum_wave]

I wasn't going to respond to post #315. But since you asked: what primordial dipole?

To me, it would mean it was a part of the CMB, without regard to our motion relative to the CMB. It would be something intrinsic to the CMB itself, much like preconditions to the Big Bang.

Siegel says, in regard to the dipole pattern, "This corresponds to a speed of about 670 km/s, or 416 miles-per-second; just over 0.2% the speed of light. This is a totally typical and reasonable peculiar velocity, although it’s fair to say that we are uncertain as to what gravitational structure is causing it. (About 20 years ago, people assumed it was a mass known as the great attractor; that appears now to be ruled out as the cause of our peculiar motion.)"

I don't know what came about to rule it out.

He also said, "there actually is a primordial dipole (l = 1) component to the cosmic microwave background’s fluctuations, but we are unable to measure it because of our own peculiar motion. In fact, if we’re at all imperfect in subtracting it out, it could artificially lower the quadrupole moment, something which was heatedly discussed in the community about a decade ago."

There seems to be more to the story, primordial dipole might be part of it. Can you rule it out somehow? I'm not sure yet what the conclusion in the following link are telling me:
http://www.ictp-saifr.org/wp-content/uploads/2014/05/cmb.dipole.ICTP-SAIFR-2014.pdf

 

[Farsight]

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. And groan, the latest post on his blog is by Sabine Hossenfelder, saying this:

"Because electric charge must be conserved, virtual particles can only be created together with their anti-particles that carry the opposite charge. Energy too must be conserved, but due to Heisenberg’s uncertainty principle, we are allowed to temporarily borrow some energy from the vacuum, as long as we give it back quickly enough. This means that the virtual particle pairs can only exist for a short time, and the more energy they carry, the shorter the duration of their existence".

This relates to what I was saying to James on another thread. Virtual particles aren't short-lived real particles that pop in and out of existence. That's just a popscience myth for kids. They're field quanta. Like you divvy up the field into little chunks and say each is a virtual particle. A virtual particle isn't a real particle. The clue to this is in the word virtual.

 

[QuarkHead]

Farsight, you are either stupid, or have some evil agenda. What Einstein is saying in your reference is exactly what PhysBang and I have been saying. The equivalence of acceleration and gravitation holds only locally in Einstein's spacetime manifold

"........ It is, for instance, impossible to choose a body of reference such that, as judged from it, the gravitational field of the earth (in its entirety) vanishes".

Notice the "in its entirety" qualification. This indicates that E. is accepting that there exists no global coordinate system for which there exists a coordinate transformation that "cancels" gravitation globally, unlike acceleration which is defined relative to a globally defined Minkowski space (globally defined means "flat" in this context)

 

[krash661]

quarkhead,
are you ever going to answer post #229 ?
i expected farsight to sidestep it, but not you. what ever.

 

[Farsight]

Farsight, you are either stupid, or have some evil agenda.

It's neither. You must be thinking of PhysBang.

What Einstein is saying in your reference is exactly what PhysBang and I have been saying. The equivalence of acceleration and gravitation holds only locally

Yes, and when you're measuring the speed of light, "locally" refers to an infinitesimal region. It doesn't refer to the room you're in. Hence Einstein said "the constancy of the speed of light no longer holds, according to the general theory of relativity, in spaces that have gravitational fields. As a simple geometric consideration shows, the curvature of light rays occurs only in spaces where the speed of light is spatially variable". Have you got this yet?

globally defined means "flat" in this context

And do you now understand the difference between 1) flat-and-level 2) flat-but-tilted and 3) curved yet? In the first situation the speed of light is constant. In the second it isn't, and it appears to vary in a linear fashion. In the third situation it varies in an inverse-square fashion, whereupon you've got spacetime curvature and tidal force. You can't detect this in the room you're in, but you know it's there because if it wasn't, the force of gravity wouldn't diminish with distance.

 

[OnlyMe]

why is it referred to as a continuum ?
also, explain the difference of space and cosmos.

Spacetime and spacetime continuum are the same thing. They refer to a model that combines space and time. I think you could add, in a 4D geometry.

Space is just space, that which lies between astronomical objects. Cosmos refers to the universe as a whole.

I did not search back to see who first used these terms in the thread, but if it was Farsight, who knows what he meant!

 

[Farsight]

quarkhead, are you ever going to answer post #229 ? i expected farsight to sidestep it, but not you. what ever.

Whoa! A physics question from the troll! Let's have a look then:

why is it referred to as a continuum ?

Because it's smooth and continuous. It isn't made out of atoms or any kind of chunks or lumps. See continuum mechanics which "is a branch of mechanics that deals with the analysis of the kinematics and the mechanical behaviour of materials modelled as a continuous mass rather than as discrete particles".

also, explain the difference of space and cosmos

Space is this ghostly gin-clear elastic continuum. The cosmos is that plus the things made out of waves in space, which we call light and matter et cetera.

 

[PhysBang]

Yes, and when you're measuring the speed of light, "locally" refers to an infinitesimal region. It doesn't refer to the room you're in. Hence Einstein said "the constancy of the speed of light no longer holds, according to the general theory of relativity, in spaces that have gravitational fields. As a simple geometric consideration shows, the curvature of light rays occurs only in spaces where the speed of light is spatially variable". Have you got this yet?

This is the opposite of the position you held a month ago. So do you now admit that the speed of light is constant at every point?

And do you now understand the difference between 1) flat-and-level 2) flat-but-tilted and 3) curved yet?

Not as you use the terms. Please do a gravitation problem to demonstrate the difference.

 

[krash661]

Spacetime and spacetime continuum are the same thing. They refer to a model that combines space and time. I think you could add, in a 4D geometry.

Space is just space, that which lies between astronomical objects. Cosmos refers to the universe as a whole.

I did not search back to see who first used these terms in the thread, but if it was Farsight, who knows what he meant!

close, but no.
and it was me who first used these terms. there's a point to it. and it shows , for me anyways, who actually understands.

 

[PhysBang]

Because it's smooth and continuous. It isn't made out of atoms or any kind of chunks or lumps.

Bzzzzzt! Incorrect! It's a reference to specific mathematical properties, not material construction.

See continuum mechanics which "is a branch of mechanics that deals with the analysis of the kinematics and the mechanical behaviour of materials modelled as a continuous mass rather than as discrete particles".

Bzzzzzzt! Nope, that's the mechanics of objects in spacetime, not of spacetime.

 

[krash661]

Whoa! A physics question from the troll! Let's have a look then:

what you actually mean {decoded~~>} a physics question that i have not sidestepped, but will answer incorrectly.

Because it's smooth and continuous. It isn't made out of atoms or any kind of chunks or lumps. See continuum mechanics which"is a branch of mechanics that deals with the analysis of the kinematics and the mechanical behaviour of materials modelled as a continuous mass rather than as discrete particles".

hilarious. but no. try again. this question of mine pertains to higher levels of physics, which you just made clear, you are clueless on , as you attempted to pretend in an obvious manner.

Space is this ghostly gin-clear elastic continuum. The cosmos is that plus the things made out of waves in space, which we call light and matter et cetera.

no.

 

[OnlyMe]

close, but no.
and it was me who first used these terms. there's a point to it. and it shows , for me anyways, who actually understands.

Why did you not quote the reference you wanted explained rather than a post by number that contained only a question?

Sounds a little like trolling.

Both of my answers came straight out of a Google search for definitions. My answer if I had given one may have been different if you had referenced the use you wanted explained.

 

[Billy T]

quarkhead,
are you ever going to answer post #229 ?...

I went back to see what this was about. You first asked it more specifically in post 227. I could not find his use of "continuum" but he did, for me, make clear his difference between "Euclidian space" (a math idea I think that assumes the "parallel lines do not cross" postulate / axiom.) and "the cosmos" (the universe).

However glad I went back as I saw quarkhead has not answered the question I asked at end of post 238. Not even with a simple "yes" or "no" but the "no" answer should have a few words as to why.

 

[Farsight]

what you actually mean {decoded~~>} a physics question that i have not sidestepped, but will answer incorrectly.

Er, no. It's a physics question I didn't see because you're on ignore. I only saw it because every now and then I do a "show ignored content" to see if anybody deserves to be taken off ignore.

hilarious. but no. try again. this question of mine pertains to higher levels of physics, which you just made clear, you are clueless on , as you attempted to pretend in an obvious manner.

I gave you the right answer. And you clearly don't deserve to be taken off ignore. Bye.

 

[krash661]

farsight, part of my point is, you claim to be an expert when in fact, you have no clue about higher levels. you only touch on basic physics. [which is elementary to higher levels] and can not grasp that. it's the higher levels that you have to at least explore just to have a grasp on 98% of what comes out of your mouth. this is why all your post are a pathetic joke, and nothing more.

 

[Farsight]

However glad I went back as I saw quarkhead has not answered the question I asked at end of post 238. Not even with a simple "yes" or "no" but the "no" answer should have a few words as to why.

You have to do an F5 or a page refresh before you see the rendered latex.

 

[krash661]

Sounds a little like trolling.

sounds like to me you're backpedaling from pretending to know, because you are embarrassed from the pretending and got caught.

 

[Billy T]

You have to do an F5 or a page refresh before you see the rendered latex.

Thanks, but that was not my question at end of post 238.

 

[krash661]

Er, no. It's a physics question I didn't see because you're on ignore. I only saw it because every now and then I do a "show ignored content" to see if anybody deserves to be taken off ignore.

I gave you the right answer. And you clearly don't deserve to be taken off ignore. Bye.

hilarious, this is an obvious backpedaling diversion , because you know yourself i just shown you to be fictitious and immature in your so called expert knowledge. this is the only reason you put individuals on ignore. thanks for confirming this. move along now.