Debunking the "Jet Effect"?

[Dan O'meara]

   Hi Dan,

     Could you direct me to the bone fragment you mention dealing with?  I was the first point this out to the public several years ago.  This same fragment can be seen toppling to the floor, after striking either Nellie connaly's back, or bouncing off the top portion of her jump seat, which I also pointed out and Paul Seaton years ago, who then made a GIF of it and posted it on hi Website.

Hi Steve,
In Reply#16 I explained my take on the dynamics of JFK's head wound which included this:

"A massive piece of scalp, torn at the crown of the head, is blasted to the right side of the head by the pressure wave and opens up the right side of the head as if it were on a hinge near the right ear. On the inside of this massive piece of scalp there are a couple of very large pieces of skull. On piece remains attached, as can be seen in the Z-film, the other piece comes loose as is thrown forward as the scalp opens up at tremendous speed."

John believes that this piece of skull being blown into the limo is something to do with the Jet Effect (Reply#19). Whereas I believe it is thrown from the massive flap of scalp that is blasted down the right side of JFK's head as a result of the explosion of the top of his head.

So, that was you who spotted the piece of skull bone dancing around in the back of the limo?
That was an excellent find as I remember.
It is the same piece of skull John has highlighted in Reply #19

[Dan O'meara]

In Z313–Z316 (Figure 5) an expulsion of mass (i.e., the “jet”) is observed resulting from an explosion caused in the wake of a high-speed projectile passage. Although the explosion emanates over a range of angles within a roughly conical cloud, the explosion of mass nevertheless is observed to escape from the single large wound on the right front of the President's head (described in the Autopsy Report [3, p. 540] and in Lattimer et al. [12]). Note that this is not a universal occurrence—depending on the firearm, bullet, target, entry and exit locations, etc., different “explosions” can result.8 But in this case a directional expulsion of mass is observed in the Zapruder Film. It is this escape of the explosion from one end of the cavity, but not the other, that creates a directional component to the mass expulsion, and thus a “jet.” In the author's study of the high resolution digital frames, it was noticed that there were particles that maintained their size and shape over adjacent frames, unlike the rest of the material in the cloud. It was subsequently realized that these were in fact solid skull fragments within a cloud of non-solid tissue, and the author has since learned that previous investigators had already ascertained this [52], [12], [7]. But here it is noted that because these solid particles hold together in flight, they can effectively act as tracers, whereby one may estimate the velocity of the ejected mass within the explosion (assuming they travel at the same velocity as the rest of the bulk material).
https://www.sciencedirect.com/science/article/pii/S2405844017331882

In Z313–Z316 (Figure 5) an expulsion of mass (i.e., the “jet”) is observed

There is no "jet" shown in frames z315 or z316

the explosion of mass nevertheless is observed to escape from the single large wound on the right front of the President's head

This is possibly the most important lie and needs to be dealt with as you keep repeating it.
There is no injury to the right front of JFK's head. The injury is clearly to the top of his head. Your famous GIF shows this in graphic detail:



There is no point in getting into some kind of pantomime "oh yes it is, oh no it isn't" routine.
Anyone can see that the injury extends across the top of the head. The right front of the head is perfectly in tact.
It's not up for discussion but I've not the slightest doubt you will see what you want to see.
The pressure wave blasts through the top of JFK's head as seen below:



"It was subsequently realized that these were in fact solid skull fragments within a cloud of non-solid tissue, and the author has since learned that previous investigators had already ascertained this [52], [12], [7]. But here it is noted that because these solid particles hold together in flight, they can effectively act as tracers,"

 
Solid particles that hold together in flight and can be used as tracers?
This is clearly what Alvarez is talking about:



If you believe he's talking about something else please demonstrate what you think it is.
If this is indeed the "solid particles" he is talking about, I would really like to hear about how these are emanating from the front right of the head.
How can he believe this "jet" is coming from the front right of the head?

Yeah no worries Dan, Alvarez and I go way back.
Here following is some simple math to wrap your head around, good luck!



Yes, indeed you are!

JohnM

I've read somewhere that in his calculations Alvarez never included the dominant acting force - that of the bullet as it flattened and fragmented against the skull driving JFK's head forward. He never accounted for a piece of the fragment travelling along the skull in a tangential manner imparting even more forward momentum to the head and he never accounted for the second interaction with the skull as the bullet fragments exited, creating even more forward momentum. He completely forgot to include the dominant acting force, the silly Nobel prize winner doing a study funded by the government.
This is what causes JFK's head to shoot forward, as you've so ably demonstrated:



But note, in none of the images you've posted showing the Jet Effect in action do we see this initial rapid forward movement.
So, they don't really show us what you would like to believe they do.
They're not really equivalent to what we see in the Z-film:





It's all a bit of smoke and mirrors really.
But if you want to carry on believing that JFK's head acted like a balloon released then you crack on.

PS: Why does the link you posted take me to a paper by Nicholas Nalli?

[John Mytton]

In Z313–Z316 (Figure 5) an expulsion of mass (i.e., the “jet”) is observed

There is no "jet" shown in frames z315 or z316

the explosion of mass nevertheless is observed to escape from the single large wound on the right front of the President's head

This is possibly the most important lie and needs to be dealt with as you keep repeating it.
There is no injury to the right front of JFK's head. The injury is clearly to the top of his head. Your famous GIF shows this in graphic detail:



There is no point in getting into some kind of pantomime "oh yes it is, oh no it isn't" routine.
Anyone can see that the injury extends across the top of the head. The right front of the head is perfectly in tact.
It's not up for discussion but I've not the slightest doubt you will see what you want to see.
The pressure wave blasts through the top of JFK's head as seen below:



"It was subsequently realized that these were in fact solid skull fragments within a cloud of non-solid tissue, and the author has since learned that previous investigators had already ascertained this [52], [12], [7]. But here it is noted that because these solid particles hold together in flight, they can effectively act as tracers,"

 
Solid particles that hold together in flight and can be used as tracers?
This is clearly what Alvarez is talking about:



If you believe he's talking about something else please demonstrate what you think it is.
If this is indeed the "solid particles" he is talking about, I would really like to hear about how these are emanating from the front right of the head.
How can he believe this "jet" is coming from the front right of the head?

I've read somewhere that in his calculations Alvarez never included the dominant acting force - that of the bullet as it flattened and fragmented against the skull driving JFK's head forward. He never accounted for a piece of the fragment travelling along the skull in a tangential manner imparting even more forward momentum to the head and he never accounted for the second interaction with the skull as the bullet fragments exited, creating even more forward momentum. He completely forgot to include the dominant acting force, the silly Nobel prize winner doing a study funded by the government.
This is what causes JFK's head to shoot forward, as you've so ably demonstrated:



But note, in none of the images you've posted showing the Jet Effect in action do we see this initial rapid forward movement.
So, they don't really show us what you would like to believe they do.
They're not really equivalent to what we see in the Z-film:





It's all a bit of smoke and mirrors really.
But if you want to carry on believing that JFK's head acted like a balloon released then you crack on.

PS: Why does the link you posted take me to a paper by Nicholas Nalli?

There is no injury to the right front of JFK's head.

You can't be serious, your so wedded to your fantasy that you can't see reality.

The Dealey Plaza eyewitnesses who were actually there, all describe the exact same explosion on the right side.



The Zapruder film shows a giant exposed bone flap on Kennedy's right side.



The Autopsy photo shows a huge wound on the right side

 

The injury is clearly to the top of his head. Your famous GIF shows this in graphic detail:

Yes, no one ever denied that there is a wound at the right front part at the top Kennedy's head but as shown above, the wound wraps around to the front right side. Kennedy was not shot from behind and below, he was shot from high and behind therefore the main momentum of the bullet went forward and exited on the front right side as seen by the Dealey Plaza eyewitnesses shown above and the Zapruder film and the autopsy photos.
I really don't believe that this needs to be spelt out.

But note, in none of the images you've posted showing the Jet Effect in action do we see this initial rapid forward movement.
So, they don't really show us what you would like to believe they do.

Huh? We aren't talking about the original impact but the subsequent effect cause by the jet effect.

In closing, you see a couple of bone fragments which exploded forward out the top of the right side and somehow equate that with what you perceive to be the main driver of the jet effect and while these bone fragments would have a vector force, the overwhelmingly main vector force exited the front right side. Alvarez himself says and I agree that there was an "explosion that emanates over a range of angles within a roughly conical cloud, the explosion of mass nevertheless is observed to escape from the single large wound on the right front of the President's head"

Btw since you obviously agree that Kennedy was shot from behind, what do you believe caused Kennedy's back and to the left motion?

JohnM

[Dan O'meara]

You can't be serious, your so wedded to your fantasy that you can't see reality.

The Dealey Plaza eyewitnesses who were actually there, all describe the exact same explosion on the right side.



The Zapruder film shows a giant exposed bone flap on Kennedy's right side.



The Autopsy photo shows a huge wound on the right side

 

Yes, no one ever denied that there is a wound at the right front part at the top Kennedy's head but as shown above, the wound wraps around to the front right side. Kennedy was not shot from behind and below, he was shot from high and behind therefore the main momentum of the bullet went forward and exited on the front right side as seen by the Dealey Plaza eyewitnesses shown above and the Zapruder film and the autopsy photos.
I really don't believe that this needs to be spelt out.

Huh? We aren't talking about the original impact but the subsequent effect cause by the jet effect.

In closing, you see a couple of bone fragments which exploded forward out the top of the right side and somehow equate that with what you perceive to be the main driver of the jet effect and while these bone fragments would have a vector force, the overwhelmingly main vector force exited the front right side. Alvarez himself says and I agree that there was an "explosion that emanates over a range of angles within a roughly conical cloud, the explosion of mass nevertheless is observed to escape from the single large wound on the right front of the President's head"

Btw since you obviously agree that Kennedy was shot from behind, what do you believe caused Kennedy's back and to the left motion?

JohnM

I suppose I just have to keep explaining it to you over and over again.
When JFK's head exploded we see pieces of skull being blown from the very top of his head, not the front as you and Alvarez (or Nalli) keep insisting. In an earlier Reply you posted this:

This high contrast image of Zapruder frame 313 shows a clear expulsion of matter out the front.



It is your (and Alvarez's) understanding that this image is showing an expulsion of matter "out the front".
It does not.
As I have clearly demonstrated with the graphic below, the expulsion of matter, that you believe is coming "out the front" is actually coming out of the top of JFK's head, AND FROM THE BACK HALF OF HIS HEAD. The yellow line is the center-line of JFK's head:



You're insistence that this expulsion of matter is "out the front" is ludicrous.
You have to concede that you are completely mistaken about this point.
It is also clear that Alvarez is making exactly the same mistake you are, even though it is patently incorrect.

When the pieces of bone/matter exit the top of JFK's head they rip the scalp at the same place - the top of his head.
The pressure wave, caused by cavitation, explodes through the top of JFK's head and as it does it blows a massive piece of scalp down the right side of his head.
This massive piece of scalp, which still has bone attached to it and can clearly be seen in the Z-film, is still attached to JFK's head near his right ear. This attachment acts as a 'hinge' and, as the right side of JFK's head is blown open, the massive piece of scalp and bone is left hanging downwards. This is what we see in the Z-film.
As the scalp/bone/right side of the head is ripped open there is a massive spray of blood in all directions but particularly to the front. That is the "explosion" witnessed at towards the front of JFK's head.

There is a simple fact that seems to have flummoxed both you and Alvarez - at the moment of impact JFK is looking down. His head is tilted forward.
In the image below the yellow lines give an idea of the orientation of JFK's head at the moment before the bullet impacts. The red line is an approximation of the bullet trajectory agreeing with the damage shown in the autopsy pictures:



You have fooled yourself that the injury to JFK's head extends to the front of his head and hold this picture up as evidence. However, the diamond-shaped cut extending down to JFK's forward is clearly that...a cut. It is clearly some kind of incision.



This same incision is NOT present in your renowned GIF:



All you need to do is use your eyes to see that this incision is NOT present in the GIF. The extent of the injury is exclusively contained to the top of the head.
Just use your eyes.

Btw since you obviously agree that Kennedy was shot from behind, what do you believe caused Kennedy's back and to the left motion?


Physics.

[Dan O'meara]

The dangers of sucking up to someone just because they've got a shiny prize:

Chapter 9 covers the involvement of Nobel prize winner Dr. Luis Alvarez, who also assumed he had a PhD in assassination “science.” Alvarez, a blatant Warren Commission apologist, is known for shooting melons, thus trying to create a reverse jet effect to explain the rearward component of JFK’s double head motion. Alvarez is one of many scientists, like Vincent Guinn, in the governmental and academic circles to have used their prestige when approaching the assassination from their individual field of expertise. Thompson recounts a long period of contentious personal communication between he and Alvarez, mainly over Alvarez’s “jiggle analysis” of the Zapruder film and “reproducing” the reverse jet effect. Critics had immediately pounced on Alvarez’s claim that a single frame horizontal blur seen at 313 reflected Zapruder’s reaction to a rifle shot, as a muzzle blast from the TSBD would not have even reached his ears yet. Ironically later in Chapter 14, a same horizontal blur will be viewed as a reaction to a shot from the Grassy Knoll, with a similar lack of success based upon similar principles. Alvarez’s attempts at shooting various objects, plus his publications, are revisited. During the writing of the book, Paul Hoch provided the author with photos and notes from the actual melon shooting sessions, which almost invariably showed objects moving forward in the direction of the bullet as had the Warren Commission tests. Thompson details the intellectual dishonesty and despicable behavior exhibited by this Nobel prize winner. I do not think the author adequately describes the enjoyment he found after obtaining Alvarez’s materials, provided by Hoch, which are now conserved at the Sixth Floor Museum.

Proof that Alvarez faked his results?
D'oh!

[Andrew Mason]

I've read somewhere that in his calculations Alvarez never included the dominant acting force - that of the bullet as it flattened and fragmented against the skull driving JFK's head forward. He never accounted for a piece of the fragment travelling along the skull in a tangential manner imparting even more forward momentum to the head and he never accounted for the second interaction with the skull as the bullet fragments exited, creating even more forward momentum. He completely forgot to include the dominant acting force, the silly Nobel prize winner doing a study funded by the government.

Alvarez certainly included the forward momentum of the bullet in his analysis.  On page 819-820 of his article in Am. J. Phys Vol. 44, No. 9 Sept. 1976 he states:

• When I studied the graph
  showing the changing position of the President's head relative
  to the moving car's coordinate system, I was finally
  convinced that the assassination buffs were right; there had
  to be a real explanation of the fact that the President's head
  did not fall back, but was driven back by some real
  force.
• I concluded that the retrograde motion of the President's
  head, in response to the rifle bullet shot, is consistent with
  the law of conservation of momentum, if one pays attention
  to the law of conservation of energy as well, and includes
  the momentum of all the material in the problem. The
  simplest way to see where I differ from most of the critics
  is to note that they treat the problem as though it involved
  only two interacting masses: the bullet and the head. My
  analysis involves three interacting masses, the bullet, the
  jet of brain matter observable in frame 313, and the remaining
  part of the head. It will turn out that the jet can
  carry forward more momentum than was brought in by the
  bullet, and the head recoils backward, as a rocket recoils
  when its jet fuel is ejected.
• ... As we shall now see, the momentum carried
  forward in this way can be much larger than the momentum
  brought in by the bullet.

This is what causes JFK's head to shoot forward, as you've so ably demonstrated:



But note, in none of the images you've posted showing the Jet Effect in action do we see this initial rapid forward movement.
So, they don't really show us what you would like to believe they do.
They're not really equivalent to what we see in the Z-film:





It's all a bit of smoke and mirrors really.
But if you want to carry on believing that JFK's head acted like a balloon released then you crack on.

The forward motion results from the time delay between the bullet impact in the back of the head and the outward ejection of matter from the head.

The rear-and-to-the-left reaction is due to the explosive ejection of blood and brain tissue from the head.  But that ejection occurs as the skull opens up which is a finite amount of time after the bullet strikes the back of the skull.  So the head goes forward from the bullet momentum imparted to the head before the head opens up and spews matter from the head in a forward-right cone which then imparts rear-left momentum to the head. This explosive ejection then slows, stops and then reverses the forward movement of the head. 

The Bell & Howell camera ran at 18.3 frames/sec (55 ms/frame) with an exposure time of 1/40th of a second (25 ms).  So the time between the bullet impact and the beginning of exposure of z313 could be as much as 30 ms. 

If the moment impact occurred immediately after the end of the exposure of z312 there would be 30 ms for the head to move forward before the beginning of exposure of z313.  For the centre of mass of a 5 kg head to move 3 cm in 30 ms. (average speed .03/.03=1 m/s) the head acquired an average momentum of 5kg x 1 m/s =5 kg m/s. We know the momentum of the incoming bullet: p_b=m_bv_b=.01kg x 610 m/sec. = 6.1 kg m/sec or 6.1 N.sec.  So if the bullet imparted most of its forward momentum to the head which then erupted sending a jet of matter forward and to the right, that would explain why the head moved forward first.

In the examples of firing at a light plastic membrane milk jug or thin membrane balloon, there is almost no delay for the exit wound to open up to expel matter from the container. So the rearward impulse begins before the target has any time to move forward.  It is different with the container is strong, rigid bone that has mass. It takes time for that matter to move away to allow the pressurized brain matter to explode out.

[John Mytton]

Alvarez certainly included the forward momentum of the bullet in his analysis.  On page 819-820 of his article in Am. J. Phys Vol. 44, No. 9 Sept. 1976 he states:

• When I studied the graph
  showing the changing position of the President's head relative
  to the moving car's coordinate system, I was finally
  convinced that the assassination buffs were right; there had
  to be a real explanation of the fact that the President's head
  did not fall back, but was driven back by some real
  force.
• I concluded that the retrograde motion of the President's
  head, in response to the rifle bullet shot, is consistent with
  the law of conservation of momentum, if one pays attention
  to the law of conservation of energy as well, and includes
  the momentum of all the material in the problem. The
  simplest way to see where I differ from most of the critics
  is to note that they treat the problem as though it involved
  only two interacting masses: the bullet and the head. My
  analysis involves three interacting masses, the bullet, the
  jet of brain matter observable in frame 313, and the remaining
  part of the head. It will turn out that the jet can
  carry forward more momentum than was brought in by the
  bullet, and the head recoils backward, as a rocket recoils
  when its jet fuel is ejected.
• ... As we shall now see, the momentum carried
  forward in this way can be much larger than the momentum
  brought in by the bullet.

The forward motion results from the time delay between the bullet impact in the back of the head and the outward ejection of matter from the head.

The rear-and-to-the-left reaction is due to the explosive ejection of blood and brain tissue from the head.  But that ejection occurs as the skull opens up which is a finite amount of time after the bullet strikes the back of the skull.  So the head goes forward from the bullet momentum imparted to the head before the head opens up and spews matter from the head in a forward-right cone which then imparts rear-left momentum to the head. This explosive ejection then slows, stops and then reverses the forward movement of the head. 

The Bell & Howell camera ran at 18.3 frames/sec (55 ms/frame) with an exposure time of 1/40th of a second (25 ms).  So the time between the bullet impact and the beginning of exposure of z313 could be as much as 30 ms. 

If the moment impact occurred immediately after the end of the exposure of z312 there would be 30 ms for the head to move forward before the beginning of exposure of z313.  For the centre of mass of a 5 kg head to move 3 cm in 30 ms. (average speed .03/.03=1 m/s) the head acquired an average momentum of 5kg x 1 m/s =5 kg m/s. We know the momentum of the incoming bullet: p_b=m_bv_b=.01kg x 610 m/sec. = 6.1 kg m/sec or 6.1 N.sec.  So if the bullet imparted most of its forward momentum to the head which then erupted sending a jet of matter forward and to the right, that would explain why the head moved forward first.

In the examples of firing at a light plastic membrane milk jug or thin membrane balloon, there is almost no delay for the exit wound to open up to expel matter from the container. So the rearward impulse begins before the target has any time to move forward.  It is different with the container is strong, rigid bone that has mass. It takes time for that matter to move away to allow the pressurized brain matter to explode out.

Thank you Andrew, having someone who actually understand physics explain some of these concepts is refreshing, because arguing with Dan like trying to argue with Moon Landing Hoaxers or the Flat Earthers, even though they mean well, their knowledge is minimal and their evaluation of the visual record is frankly embarrassing.

JohnM

[Dan O'meara]

Thank you Andrew, having someone who actually understand physics explain some of these concepts is refreshing, because arguing with Dan like trying to argue with Moon Landing Hoaxers or the Flat Earthers, even though they mean well, their knowledge is minimal and their evaluation of the visual record is frankly embarrassing.

JohnM

"...their evaluation of the visual record is frankly embarrassing."

Let's see whose evaluation of the visual record is embarrassing.
It was you who posted this:

This high contrast image of Zapruder frame 313 shows a clear expulsion of matter out the front.



A child can see that you're wrong.
Your evaluation of this image is genuinely embarrassing.
I don't have the slightest doubt that you will avoid this observation like the plague as it demonstrates your true grasp of the issues.
You can pretend to "understand the physics" all you want but your inability to understand a basic image tells us all we need to know.
Alvarez also believed this matter was being expelled out the front. It makes me cringe that you have simply swallowed this down (as, it seems, has Andrew).
If you can't even understand the basics how trustworthy do you think your assessment of the physics is.

Just for laughs - Andrew, do you think the image above shows matter being expelled out of the front of JFK's head?
Let the  begin.