Split from Gravitational waves Discovered

[Robittybob1]

Well for starters I read a buttload of articles and textbooks. In CMB measurements the speed of interactions is particularly stressed. This includes the speed of gravity. You'll often hear this expressed as sound waves. The speed of sound being the speed of light in a vacuum. It's of fundamental importance in Cosmology applications.

 

Any papers I've ever read apply the speed of gravity=c in the medium they are examining in CMB measurements.

 

Connect the dots,, gravity affects mass density. Density affects temperature... by looking at temperature anisotropy rate of change we are

If the speed of sound in a vacuum is "c" maybe that is what we are talking about but once again I have never heard that said before either.

(Can you give me a clue as to where this idea "speed of sound in a vacuum" came from please? )

Edited February 13, 2016 by Robittybob1

[Mordred]

Google baryon accoustic oscillations.

 

"Imagine an overdense region of the primordial plasma. While this region of overdensity gravitationally attracts matter towards it, the heat of photon-matter interactions creates a large amount of outward pressure. These counteracting forces of gravity and pressure created oscillations, analogous to sound waves created in air by pressure differences"

 

I should have clarified the speed of sound bit, as referring to the pressure oscillations not sound itself.

 

 

https://en.m.wikipedia.org/wiki/Baryon_acoustic_oscillations

[Robittybob1]

Well if anyone can explain "Aberration and the Speed of Gravity" by S. Carlip you are most welcome to give a simple version of it so we can all read the paper with a bit more understanding.

Thanks

∗

[Mordred]

Well the simplest way to explain the paper is to distinquish what is meant by instantaneous and retarded position.

 

So to do so we will set an example scenario. For simplicity we will use signals. Exact nature of the signal is not important, but the signal propogates at the speed of light.

 

Take a stationary measuring a good visualizer is one with a direct arrow. That direction arrow pointing in the direction it receives the signal from.

 

Now take the emitter and move the emitter at relativistic speed. This emitter sends a series of signals via the shortest path to the receiver.

 

In Euclidean flat space the shortest path being a straight line, but in relativity it is determined by its worldline. Which for massless particles is the null geodesic.

 

Now the instantaneous position is basically the 3d case . The retarded position is the 4d case where we add the time coordinate.

 

 

So starting with known positions, the emitter starts transmitting. After establishing its coordinates to the receiver. We move the emitter. In the instantaneous case the arrow would point to the new position. However the receiver hasn't recieved the new position yet, it's still pointing to the retarded position ( position where it last received a signal).

 

Essentially this is what the math breaks down to. What it is stating that information concerning an event follows the worldline that worldline determined by spacetime curvature.

 

If we did receive the signal faster than the speed of light this would be a causality violation. According to GR. Reason being time is defined as ct.

 

To fully appreciate the paper study the geodesic equation, lightcones and worldlines.

Edited February 14, 2016 by Mordred

[Robittybob1]

I did a search for discussions on Carlin's paper and came across another explanation by Carlin without the math and it is just about comprehensible

http://math.ucr.edu/home/baez/physics/Relativity/GR/grav_speed.html

"Does Gravity Travel at the Speed of Light?"

 

It is worth a read if you really want to understand the connection between the speed of gravity and the reason gravitational radiation.

 

The argument is that G-Rad implies gravity operates at the speed of light for if it was instantaneous the G-Rad would not be needed.

Only orbital decays were known to exist at the time.

[Mordred]

Not a bad read, better than my oversimplification.

[Robittybob1]

Not a bad read, better than my oversimplification.

It has helped me too and I will never ask for proof that gravity acts at the speed of light ever again.

 

Did you notice it implied that because the signal is "late" there is a dampening of the orbital motion (energy lost to G-Rad) but in the case of the Earth it is such a small and insignificant amount we don't think about it, but in cases of orbiting pulsars and black holes or stars close to and orbiting around black holes the loss of orbital energy is significant and the orbit decays.

I would still like to know the physics of what is happening within matter itself to explain how the mismatch in the gravity signal initiates the loss of energy and that then results in a loss of mass.

(in the case of the merging black holes 3 sun masses were converted to energy in just 0.3 seconds.)

E = MC^2 applied means the gravitational radiation has come from matter but without fusion or fission so where is this reduction in mass coming from? This is a most interesting question. Do you see it?

Edited February 14, 2016 by Robittybob1

[Mordred]

Start with the full formula

 

[latex]e^2=pc^2+(m_o^2)^2[/latex]

 

P being momentum, m_O being rest mass

 

Then think about how mass is defined but more importantly what type of mass. (Rest or inertial mass). Mass and energy are in essence two sides of the same coin. Both are properties both depend upon the other.

 

Rest mass, can be contributed via the strong force, the electromagnetic (electromagnetic mass)force and atomic force. (Atomic mass) Though most commonly the strong force.

 

Then on top of this you have mass gained via inertia. See above equation.

 

Rest mass tells us the mass of an object as though it was at rest. However you need the above equation to describe the total energy an object has.

 

 

Here is a good example particle accelerators collide two protons at 0.99 c. Rest mass of a single proton is 938.272046 MeV. Yet the collision can produce 123 Gev particles. (Higgs Boson). The mass gain is due to mass gained via inertia

Edited February 14, 2016 by Mordred

[Robittybob1]

Start with the full formula

 

[latex]e^2=pc^2+(m_o^2)^3[/latex]

 

P being momentum, m_O being rest mass

 

Then think about how mass is defined but more importantly what type of mass. (Rest or inertial mass). Mass and energy are in essence two sides of the same coin. Both are properties both depend upon the other.

 

Rest mass, can be contributed via the strong force, the electromagnetic (electromagnetic mass)force and atomic force. (Atomic mass) Though most commonly the strong force.

 

Then on top of this you have mass gained via inertia. See above equation.

 

Rest mass tells us the mass of an object as though it was at rest. However you need the above equation to describe the total energy an object has.

 

 

Here is a good example particle accelerators collide two protons at 0.99 c. Rest mass of a single proton is 938.272046 MeV. Yet the collision can produce 123 Gev particles. (Higgs Boson). The mass gain is due to mass gained via inertia

Very good, I forgot that even though the infalling BHs would have been gaining kinetic energy they would have been losing angular momentum. I think you possibly use the word inertia in the wrong way. Can you explain why you use "inertia" rather than "momentum" as in "The mass gain is due to mass gained via inertia"?

Edited February 14, 2016 by Robittybob1

[Mordred]

Definition of inertia. "Inertia is the resistance of any physical object to any change in its state of motion (this includes changes to its speed, direction or state of rest). It is the tendency of objects to keep moving in a straight line at constant velocity."

 

Momentum is the quantity of motion of a moving body, measured as a product of its mass and velocity.

 

Inertial mass is a mass parameter giving the inertial resistance to acceleration of the body when responding to all types of force.

 

Mass. In physics, the property of matter that measures its resistance to acceleration.

 

Changes in velocity and/or direction is acceleration.

 

The formula above only concerns itself with momentum p not acceleration.

 

Oops had to correct the typo in the formula

Edited February 14, 2016 by Mordred

[Robittybob1]

I'm going to have to learn how to use the word inertia properly. Thanks for the lesson.

Do we say "Inertial mass decreased as the BH's merged" or shall we just say the mass decreased?

Do you accept that the G-Rad removes mass as in energy (E=mc^2)

Does this radiation depend on the amount of matter at the EH? I've never heard of that if you think it does, so can you keep an eye out for information regarding this?

Edited February 14, 2016 by Robittybob1