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calling all physicists



 
 
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  #1  
Old September 29th 17, 03:50 AM posted to uk.tech.digital-tv
Bill Wright[_3_]
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Default calling all physicists

Apparently shock waves can travel trough the air at speeds exceeding
that or normal sounds. In that case, if an electromagnetic shock wave
was generated could it travel faster than the speed of light?

Bill
  #2  
Old September 29th 17, 07:41 AM posted to uk.tech.digital-tv
Brian Gaff
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Default calling all physicists

Well not one of those but there are a number of issues here. Sound needs a
medium to make it from one place to another, light as far as we know does
not. Also the accepted wisdom at present suggests that the reason you do not
find anything faster than light is because of the exponential increase in
mass at near light speed.
However if your particle has no mass , then that would seem to me to make
its increase a little dubious.
I suppose a shock wave of broad spectrum is what you get from a nuclear
explosion.


Its a non answer of course because when we are talking about such
fundamental things as particles, one could find, as in entangled systems,
that the alteration of one many millions of miles away from the other having
an instantaneous effect of proof of faster than light travel, but in fact we
measure distance in our dimension we experience and many feel that the
distance is merely there as far as wee can experience it. I'm sur some
budding Quantum scientist will pop in later to clear it all up.
I hate messy particles all around the place.
Brian

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"Bill Wright" wrote in message
news
Apparently shock waves can travel trough the air at speeds exceeding that
or normal sounds. In that case, if an electromagnetic shock wave was
generated could it travel faster than the speed of light?

Bill



  #3  
Old September 29th 17, 10:05 AM posted to uk.tech.digital-tv
Jim Lesurf[_2_]
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Posts: 4,206
Default calling all physicists

In article , Bill Wright
wrote:
Apparently shock waves can travel trough the air at speeds exceeding
that or normal sounds. In that case, if an electromagnetic shock wave
was generated could it travel faster than the speed of light?


Short answer:

Cherenkov

Longer answer:

When I was still in the 'ed biz' and ocasionally wrote for New Scientist I
started getting told about all kinds of journal papers that - one way or
another - implied or claimed FTL. Other academics I knew also started
sending them to me as puzzle-pieces to spot the flaw(s). Sadly, they were
all flawed, hence the implications/claims were bollox. (Technical term
often used by academics.)

Later on I got sent a research council report to assess. This was a final
report on a project they'd given a grant. It was the work of a well known
prof who'd extracted a quarter of a million quid to make a system to try
out his ideas. They implied FTL. One of his co-workers had visited us and
given a talk on the project while it was under way. At the time I had my
doubts. The final results confirmed them. Very fancy complex maths and
loads of graphs and claims. Sadly, again, they were bollox. No idea if they
really believed what they'd written, and simply had made some daft errors,
or couldn't face admitting they'd made a mess and wasted the money.

Sound and light are very different. Beyond that, it drifts into the "it
depends what you mean by" areas when it comes to the speed of light.

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics https://www.st-andrews.ac.uk/~www_pa...o/electron.htm
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  #4  
Old September 29th 17, 11:22 AM posted to uk.tech.digital-tv
Robin[_8_]
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Default calling all physicists

On 29/09/2017 03:50, Bill Wright wrote:
Apparently shock waves can travel trough the air at speeds exceeding
that or normal sounds. In that case, if an electromagnetic shock wave
was generated could it travel faster than the speed of light?


Will physics on a par with BH (Calcutta) (failed) do?

Shock waves in air are (by definition) supersonic waves - ie they move
faster than the speed of ordinary sound waves. But then lots of other
things can also move faster than the speed of sound: eg a high velocity
bullet, a supersonic aircraft.

You can get the equivalent of the bullet with light: a particle which
moves faster than the speed of light in the medium (eg water) - but not
faster than "c", the speed in a vacuum. But I don't know of any EM
"shock" wave.



--
Robin
reply-to address is (intended to be) valid
  #5  
Old September 29th 17, 11:26 AM posted to uk.tech.digital-tv
R. Mark Clayton[_2_]
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Default calling all physicists

On Friday, 29 September 2017 11:22:40 UTC+1, Robin wrote:
On 29/09/2017 03:50, Bill Wright wrote:
Apparently shock waves can travel trough the air at speeds exceeding
that or normal sounds. In that case, if an electromagnetic shock wave
was generated could it travel faster than the speed of light?


Will physics on a par with BH (Calcutta) (failed) do?

Shock waves in air are (by definition) supersonic waves - ie they move
faster than the speed of ordinary sound waves. But then lots of other
things can also move faster than the speed of sound: eg a high velocity
bullet, a supersonic aircraft.

You can get the equivalent of the bullet with light: a particle which
moves faster than the speed of light in the medium (eg water) - but not
faster than "c", the speed in a vacuum. But I don't know of any EM
"shock" wave.


Electromagnetic pulse (from H bomb).



--
Robin
reply-to address is (intended to be) valid


  #6  
Old September 29th 17, 11:35 AM posted to uk.tech.digital-tv
Brian Gaff
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Posts: 6,944
Default calling all physicists

Yes I said that.
The point of the speed of light being constant depends on you measuring it
from the same place. If you have two people heading toward each other at the
speed onf light then any torch they use will be blue shifted in frequency
when viewed by the other. IE the wave function means the wave fronts bunch
up but tthe speed is still the same. However you cannot move that fast due
to the limit of infinite mass.
Mas also produces warping of space/time due to the gravity it creates. This
is where the famous equation comes from.
Its also why we still have not unified gravity with the other forces. We
know they are interlinked but some bits of the final relationship are not
visible to us yet.
The detection of gravitaional waves and the fact they travel at the speed
of light has made a lot of people think a bit harder about this higgs bozon
and how it is used to signify mass in systems.
Brian

--
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This newsgroup posting comes to you directly from...
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"R. Mark Clayton" wrote in message
...
On Friday, 29 September 2017 11:22:40 UTC+1, Robin wrote:
On 29/09/2017 03:50, Bill Wright wrote:
Apparently shock waves can travel trough the air at speeds exceeding
that or normal sounds. In that case, if an electromagnetic shock wave
was generated could it travel faster than the speed of light?


Will physics on a par with BH (Calcutta) (failed) do?

Shock waves in air are (by definition) supersonic waves - ie they move
faster than the speed of ordinary sound waves. But then lots of other
things can also move faster than the speed of sound: eg a high velocity
bullet, a supersonic aircraft.

You can get the equivalent of the bullet with light: a particle which
moves faster than the speed of light in the medium (eg water) - but not
faster than "c", the speed in a vacuum. But I don't know of any EM
"shock" wave.


Electromagnetic pulse (from H bomb).



--
Robin
reply-to address is (intended to be) valid




  #7  
Old September 29th 17, 11:56 AM posted to uk.tech.digital-tv
Robin[_8_]
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Posts: 466
Default calling all physicists

On 29/09/2017 11:26, R. Mark Clayton wrote:
On Friday, 29 September 2017 11:22:40 UTC+1, Robin wrote:
On 29/09/2017 03:50, Bill Wright wrote:
Apparently shock waves can travel trough the air at speeds exceeding
that or normal sounds. In that case, if an electromagnetic shock wave
was generated could it travel faster than the speed of light?


Will physics on a par with BH (Calcutta) (failed) do?

Shock waves in air are (by definition) supersonic waves - ie they move
faster than the speed of ordinary sound waves. But then lots of other
things can also move faster than the speed of sound: eg a high velocity
bullet, a supersonic aircraft.

You can get the equivalent of the bullet with light: a particle which
moves faster than the speed of light in the medium (eg water) - but not
faster than "c", the speed in a vacuum. But I don't know of any EM
"shock" wave.


Electromagnetic pulse (from H bomb).


Can you point to evidence they travel faster than the speed of other EM
waves?

If you have in mind that the high-energy particles produced in the
explosion (and which can account for much of the peak energy through
synchrotron radiation) might exceed the local speed of light, (a) is
there evidence that and (b) so what given that would not be an EM shock
wave but particles.




--
Robin
reply-to address is (intended to be) valid
  #8  
Old September 29th 17, 12:06 PM posted to uk.tech.digital-tv
Robin[_8_]
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Posts: 466
Default calling all physicists

On 29/09/2017 11:36, Huge wrote:
On Friday, 29 September 2017 11:22:40 UTC+1, Robin wrote:
On 29/09/2017 03:50, Bill Wright wrote:
Apparently shock waves can travel trough the air at speeds exceeding
that or normal sounds. In that case, if an electromagnetic shock wave
was generated could it travel faster than the speed of light?


Will physics on a par with BH (Calcutta) (failed) do?

Shock waves in air are (by definition) supersonic waves - ie they move
faster than the speed of ordinary sound waves. But then lots of other
things can also move faster than the speed of sound: eg a high velocity
bullet, a supersonic aircraft.


You may find this, and the cited references, useful;

https://en.wikipedia.org/wiki/Phase_velocity


I'm unclear what I was meant to take from that. But if you had in mind:

"The phase velocity of electromagnetic radiation may – under certain
circumstances (for example anomalous dispersion) – exceed the speed of
light in a vacuum"

then yes indeed. But it does continue:

"but this does not indicate any superluminal information or energy
transfer".

I cannot envisage what might be called an "EM shock wave" that does not
carry energy or information


--
Robin
reply-to address is (intended to be) valid
  #9  
Old September 29th 17, 12:32 PM posted to uk.tech.digital-tv
Jim Lesurf[_2_]
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Posts: 4,206
Default calling all physicists

In article , Robin
wrote:
I'm unclear what I was meant to take from that. But if you had in mind:


"The phase velocity of electromagnetic radiation may - under certain
circumstances (for example anomalous dispersion) - exceed the speed of
light in a vacuum"


then yes indeed. But it does continue:


"but this does not indicate any superluminal information or energy
transfer".


The above seems a round-the-houses way to 'explain' something, so the wiki
might need editing.

Under normal (i.e. non-dispersive uniform media, etc) circumstances the
speed of light has a simple relationship to the wavelength and frequency.
You can then use the standard school textbook formula to relate them.

But in dispersive or otherwise non-linear/uniform situations that may not
give you the actual velocity of propagation of anything. You then need to
take the details into account to understand what is really happening.

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics https://www.st-andrews.ac.uk/~www_pa...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

  #10  
Old September 29th 17, 12:38 PM posted to uk.tech.digital-tv
Jim Lesurf[_2_]
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Posts: 4,206
Default calling all physicists

In article , R.
Mark Clayton wrote:
You can get the equivalent of the bullet with light: a particle which
moves faster than the speed of light in the medium (eg water) - but
not faster than "c", the speed in a vacuum. But I don't know of any
EM "shock" wave.


Electromagnetic pulse (from H bomb).


Not sure that is correct. A shock wave tends to depend on propagating in a
nonlinear medium, and alters the local behaviour to get a change in
propagation velocity. (e.g. in 'high' explosives).

EMP weapons would probably be detonated in space above the atmosphere to
get maximum coverage. The intent is to generate very large fields and
rates-of-onset, etc, to toast electronics as a result of the effects
produced. The wavefront probably would interact with the materials in the
atmosphere, but probably not change the velocity much. However if someone
has checkable figures, I'd be interested to see them. Trying to publish
them might get you shot, first, though. :-)

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics https://www.st-andrews.ac.uk/~www_pa...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

 




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