# If photon is mass-less why can it be pulled into blackhole?

Discussion in 'Physics & Math' started by Saint, Aug 7, 2017.

1. ### QuarkHeadRemedial Math StudentValued Senior Member

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You know, one could be forgiven for thinking you don't read even your own posts. I quote you
When I disagreed to the extent that even I understood the metric, you responded with link that pointed that there is at least one non-metrical theory of gravitation. And this is not Einstein's, which you refer to above

Answer me this: If a valid non-metric theory of gravitation exists, why is there any need to "understand the physical reality of the metric"?

3. ### The GodValued Senior Member

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Rest all is an attempt to drag on your trivial metric attempt despite the fact that in very first response (#17) I clarified and pointed out the context.

5. ### Write4UValued Senior Member

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IMO, movement from one spacetime coordinate to the adjacent coordinate is a function of QM.
A photon cannot travel faster than c, because it needs to renew itself as a discreet particle. This function requires time and is what restricts even a massless particle from traveling at infinite speed.
At superluminal speed a particle is no longer a discrete energetic packet but becomes a set of "enfolded" virtual entities, a probabilistic potential.

Last edited: Aug 12, 2017

7. ### DaveC426913Valued Senior Member

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W4U, I have reported this post with a request to remove it; it is an unsubstantiated opinion. It might be fine for other subfora, but it does not belong in a hard-science forum, where people should be able to expect science-based information about their questions.

8. ### Write4UValued Senior Member

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I fundamentally agree with your argument, but my posit was not based on pure speculation, but rather a probative statement, based on the following;
and

To me these examples demonstrate a relationship between QM and SOL. (EMR)
If this is completely outside the parameters of the discussion, I'll be happy to sit back and just follow the arguments from "learned fellows".

9. ### SchmelzerValued Senior Member

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I see there has not really been an answer yet.

In Einstein's GR, it is not the mass which attracts (and is attracted) via the gravitational field, but the energy-momentum tensor.

If the velocities are small, the main contribution to the energy-momentum tensor comes from energy, and the energy is roughly defined by the mass. Roughly, the energy is $E = m c^2 + \frac12 m v^2 + \ldots$. If the velocity is small, you can ignore the part which depends on the velocity and get the famous $E=mc^2$. (Which is today only a rough approximation - at Einstein time, a notion of "relativistic mass", which depends on the velocity, was defined, and with this variable mass the formula was exact. Today that "relativistic mass" is no longer used, the only mass used today was, at that time, called "rest mass". And for the "rest mass", the formula $E=mc^2$ is correct only if the body is in rest.)

The exact relativistic formula would be $E^2 - p^2c^2 = m^2c^4$. So, neither energy nor momentum is zero if the mass is zero. The momentum of a photon is defined by $p=2\pi\hbar\nu$ via the frequency. With nonzero energy and momentum it is attracted by gravity and attracts other things too.

10. ### Confused2Registered Senior Member

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I don't despise maths and have 'some' differential calculus and I'm interested - if you choose to reply please could you keep it as simple as possible even at the expense of strict accuracy.

11. ### hansdaValued Senior Member

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Which part of GR, do you think is a field? Is it spacetime? or The math of spacetime? Do you think this field (of GR) is similar to magnetic field or electrical field?

12. ### hansdaValued Senior Member

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My understanding of Einstein's GR, is that spacetime curves due to mass and movement of mass is due to curvature of spacetime. The concept of attraction is perhaps not used in GR model but it is used in Newtonian model.

Isn't it due to curvature of spacetime?

'Attraction by gravity' - Is it GR concept or Newtonian concept?

13. ### hansdaValued Senior Member

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Particle photon's trajectory is alongwith the spacetime. Curvature of spacetime around a blackhole is very high. The spacetime can not escape the blackhole. So, particle photon also can not escape the blackhole.

14. ### Write4UValued Senior Member

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As I understand Hawking Radiation, the theory posits that this happens near the event horizon of a BH and it is a quantum function, i.e. a change of energy state so large that some electrons not only change orbit, but completely break away from the internal strong gravity of an atom itself and escape into space.
http://math.ucr.edu/home/baez/physics/Relativity/BlackHoles/hawking.html

Is this not already a sign that atoms are being pulled apart and the lightest sub-particles (electrons with zero mass) escape while most of the heavier sub-particles continue down into the hole?

Last edited: Aug 15, 2017
15. ### DaveC426913Valued Senior Member

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No.

Hawking radiation occurs with virtual particles.

The quantum vacuum seethes with energy, and frequently a bit of neutral vacuum can spontaneously split into a particle/antiparticle pair (think of positive/negative charges or positive/negative mass). The net effect of thee two particles is still zero, so nothing has been created - net charge is zero and net mass is zero.

Not that it matters, because they immediately annihilate each other, going back to non-existence -just another flavor of zero charge/mass.

But if this happens so close to the BH EH that one of them gets trapped and the other does not, the lone virtual particle, having no counterpart, becomes real (it now has a net effect, since its canceling counterpart can no longer cancel it), and escapes from the BH, resulting in a net energy loss in the form of a real particle being emitted from the BH.

Last edited: Aug 15, 2017
16. ### Write4UValued Senior Member

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Interesting.
Would that indicate that the Higgs field near a BH becomes so condensed that it spontaneously creates virtual Higgs (and other) bosons, somewhat similar like we did at Cern?

17. ### river

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This is nonsense .

Retracted .

In simple terms Schmelzer.

Last edited: Aug 15, 2017
18. ### James RJust this guy, you know?Staff Member

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Write4U:

Dave is right.

This thread is in our Science sections of the forum. It is not appropriate to post unsupported speculation that is non-scientific. By which I mean this kind of thing:
This is a vague idea you have, which apparently has no basis in established science. A better forum would be our "Alternative Theories" section, if you have anything to flesh out your ideas. Otherwise, this is little better than a just-so story or guesswork.

Enfolded virtual entities are not part of physics, to my knowledge. Again, this idea seems to originate with you. It would be fine in the Science sections if you had an actual scientific argument to make about it, but apparently you do not.

19. ### James RJust this guy, you know?Staff Member

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How do you account for the orbits of stars around Saggitarius A*? What kind of object do you think they are orbiting, if not a black hole?

20. ### river

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Hmm... I guess it is a matter of perspective .

Are stars being attracted to the core , drawn in towards the galactic core or are stars being thrown out by the galactic core ?

21. ### Write4UValued Senior Member

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I admit I cannot defend QM on scientific grounds.
It is my take on Bohmian Mechanics but again I cannot defend it scientifically.

I hope that I'll be allowed to pose an occasional question, if only to get a reference or link from reliable sources so I don't have to search the net for hours trying to find something which doesn't exist....

22. ### SchmelzerValued Senior Member

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Replace "mass" with "matter". Massless matter fields (like the EM field) also curve spacetime, and their movement is also influenced by curvature.
Yes, the spacetime interpretation does not use it. The notion of force requires some standard of motion without force, which was the inertial motion. But inertial motion is straight line motion relative to a flat background which does not exist in GR.
In GR, it is not mass but energy, momentum and pressure (which define, together, the energy-momentum tensor) which create some nontrivial gravitational fields.

For the difference, think about some piece of matter together with antimatter. Two equal masses. They would create a large gravitational field in Newtonian theory. Then they meet each other, and all the mass is transformed into something without mass, like radiation. So, once the mass disappeared, did the gravitational field disappear too? In GR, not, the energy remains the same.

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