| Topic: |
Science > Physics |
| User: |
"phoenix" |
| Date: |
06 Mar 2005 12:51:01 AM |
| Object: |
What really is "Light" (assuming SR is correct)?? |
Assuming SR is correct. There is something very
strange about "light".
What really is light??
Light imposes limits on space-time, setting an absolute
limit for the velocity of any object and distorting the
dimensional relations of objects that approach that
velocity. But what does light have to do with how fast
something goes? If light is a thing in space-time, how
can it affect the length, the mass, and the passage of
time of other things in space-time? And why should
the equivalence of mass and energy have anything to
do with the speed, much less the square of the speed,
of light?
P.
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| User: "Bilge" |
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| Title: Re: What really is "Light" (assuming SR is correct)?? |
06 Mar 2005 11:59:56 PM |
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phoenix:
Assuming SR is correct. There is something very
strange about "light".
What really is light??
The carrier of the electromagnetic force.
Light imposes limits on space-time, setting an absolute
No, it doesn't.
limit for the velocity of any object and distorting the
dimensional relations of objects that approach that
velocity. But what does light have to do with how fast
something goes?
Nothing.
If light is a thing in space-time, how
can it affect the length, the mass, and the passage of
time of other things in space-time? And why should
the equivalence of mass and energy have anything to
do with the speed, much less the square of the speed,
of light?
Anything which is massless must propagate at `c'. If maxwell's
equations are correct, then light propagates at `c' and therefore
must be massless. If light has mass, then maxwell's equations are
not correct and light doesn't propagate at `c'.
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| User: "Franz Heymann" |
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| Title: Re: What really is "Light" (assuming SR is correct)?? |
06 Mar 2005 02:30:05 PM |
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"phoenix" <photonixx@go.com> wrote in message
news:1110091861.355984.313130@o13g2000cwo.googlegroups.com...
Assuming SR is correct. There is something very
strange about "light".
What really is light??
Light imposes limits on space-time, setting an absolute
limit for the velocity of any object and distorting the
dimensional relations of objects that approach that
velocity. But what does light have to do with how fast
something goes?
The mass of a photon is zero. This means that it can only ever move
at the speed c of SR. That speed, in turn, is just the unit
conversion needed between ths spce dimensions and the time dimension
of soace-time.
If light is a thing in space-time, how
can it affect the length, the mass, and the passage of
time of other things in space-time?
Light does not do that.
And why should
the equivalence of mass and energy have anything to
do with the speed, much less the square of the speed,
of light?
Keep saying to yourself that c is a universal constant with the
dimensions of a speed. It is the conversion constant between the
units of space and the units of time. Any particle which has no mass
can only move at the speed c. Photons happen to be a particles wqith
zero mass.
--
Franz
"A first-rate laboratory is one in which mediocre scientists can
produce outstanding work"
P.M.S. Blackett
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| User: "Lefty" |
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| Title: Re: What really is "Light" (assuming SR is correct)?? |
06 Mar 2005 08:25:57 PM |
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Keep saying to yourself that c is a universal constant with the
dimensions of a speed. It is the conversion constant between the
units of space and the units of time. Any particle which has no mass
can only move at the speed c. Photons happen to be a particles wqith
zero mass.
This is what confuses me about the Bose-Einstein condensate, where they are
slowing the speed of light to ordinary speeds. Are they still playing with
photons if they are travelling that slowly ? Is it still considered light ?
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| User: "N:dlzc D:aol T:com \dlzc\ N: dlzc1 D:cox" |
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| Title: Re: What really is "Light" (assuming SR is correct)?? |
06 Mar 2005 06:41:41 PM |
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Dear Lefty:
"Lefty" <Ye@h.Right> wrote in message
news:xoudnaoJSuojPbbfRVn-1Q@comcast.com...
Keep saying to yourself that c is a universal constant with
the
dimensions of a speed. It is the conversion constant between
the
units of space and the units of time. Any particle which has
no mass
can only move at the speed c. Photons happen to be a
particles wqith
zero mass.
This is what confuses me about the Bose-Einstein condensate,
where they are
slowing the speed of light to ordinary speeds. Are they still
playing with
photons if they are travelling that slowly ?
This does not, in general, require a BE condensate. The behavior
has been duplicated in much warmer mediums.
Is it still considered light ?
Yes.
David A. Smith
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| User: "Morituri-|-Max" |
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| Title: Re: What really is "Light" (assuming SR is correct)?? |
06 Mar 2005 03:37:19 AM |
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"phoenix" <photonixx@go.com> wrote in message
news:1110091861.355984.313130@o13g2000cwo.googlegroups.com...
Assuming SR is correct. There is something very
strange about "light".
What?
What really is light??
Photons..
Light imposes limits on space-time, setting an absolute
limit for the velocity of any object and distorting the
dimensional relations of objects that approach that
velocity. But what does light have to do with how fast
I think you are starting bass-ackwards.. light doesn't "impose" anything on
anything, any more than fire imposes flammability on you when you are
covered with napalm.
Light is subject to the effects of curved space.
something goes? If light is a thing in space-time, how
can it affect the length, the mass, and the passage of
time of other things in space-time? And why should
the equivalence of mass and energy have anything to
do with the speed, much less the square of the speed,
of light?
If you don't start with a bass-ackwards tortured view of what light "is", it
isn't strange at all.
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| User: "phoenix" |
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| Title: Re: What really is "Light" (assuming SR is correct)?? |
06 Mar 2005 04:08:36 AM |
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Morituri-|-Max wrote:
Light imposes limits on space-time, setting an absolute
limit for the velocity of any object and distorting the
dimensional relations of objects that approach that
velocity. But what does light have to do with how fast
I think you are starting bass-ackwards.. light doesn't "impose"
anything on
anything, any more than fire imposes flammability on you when you are
covered with napalm.
Light is subject to the effects of curved space.
I mean. As you go near the speed of light. Your mass
would increase and time would slow down. When you
hit C, your mass becomes infinite. Why is C so
special? Why can light cause all that or relate to
them if light is just photons?
Pls. illustrate in complete details. Thanks.
I've got to get to the bottom of all these...
Light & Relativity or I can't sleep.
P
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| User: "Bill Hobba" |
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| Title: Re: What really is "Light" (assuming SR is correct)?? |
06 Mar 2005 05:13:54 AM |
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"phoenix" <photonixx@go.com> wrote in message
news:1110103716.231214.134730@o13g2000cwo.googlegroups.com...
Morituri-|-Max wrote:
Light imposes limits on space-time, setting an absolute
limit for the velocity of any object and distorting the
dimensional relations of objects that approach that
velocity. But what does light have to do with how fast
I think you are starting bass-ackwards.. light doesn't "impose"
anything on
anything, any more than fire imposes flammability on you when you are
covered with napalm.
Light is subject to the effects of curved space.
I mean. As you go near the speed of light. Your mass
would increase and time would slow down.
As has been explained many time on this forum mass does not increase with
velocity.
When you
hit C, your mass becomes infinite.
Since a massive object can not travel a c the above is a nonsense statement.
Why is C so special?
It isn't. Its value is simply an artifact of the units used. In natural
units its value is one.
Why can light cause all that or relate to
them if light is just photons?
You are confused . Light causes nothing of the sort. The fact photons have
zero mass (at least as far as we can tell) is why they travel at the
invariant speed predicted by relativity.
Pls. illustrate in complete details. Thanks.
See the following for what is actually happening:
http://arxiv.org/abs/physics/0110076,
and ancient, but I still think excellent post by Tom Roberts
http://groups.google.com/groups?hl=en&lr=&c2coff=1&selm=54jfst%24glp%40ssbunews.ih.lucent.com
and chapter 10 of
http://www.courses.fas.harvard.edu/~phys16/Textbook/
under the heading of Relativity without c.
I've got to get to the bottom of all these...
Light & Relativity or I can't sleep.
Read the references above and if you think about it a bit I am sure you will
understand.
Thanks
Bill
P
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| User: "phoenix" |
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| Title: Re: What really is "Light" (assuming SR is correct)?? |
06 Mar 2005 06:23:18 AM |
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Bill Hobba wrote:
"phoenix" <photonixx@go.com> wrote in message
news:1110103716.231214.134730@o13g2000cwo.googlegroups.com...
Morituri-|-Max wrote:
Light imposes limits on space-time, setting an absolute
limit for the velocity of any object and distorting the
dimensional relations of objects that approach that
velocity. But what does light have to do with how fast
I think you are starting bass-ackwards.. light doesn't "impose"
anything on
anything, any more than fire imposes flammability on you when you
are
covered with napalm.
Light is subject to the effects of curved space.
I mean. As you go near the speed of light. Your mass
would increase and time would slow down.
As has been explained many time on this forum mass does not increase
with
velocity.
When you
hit C, your mass becomes infinite.
Since a massive object can not travel a c the above is a nonsense
statement.
Why is C so special?
It isn't. Its value is simply an artifact of the units used. In
natural
units its value is one.
Why can light cause all that or relate to
them if light is just photons?
You are confused . Light causes nothing of the sort. The fact
photons have
zero mass (at least as far as we can tell) is why they travel at the
invariant speed predicted by relativity.
I was reading a book by Sam Avery where he stated that light is special
and relate to all that because space and time is inside our mind. Guess
the author is not well acquainted in relativity.
http://www.amazon.com/exec/obidos/tg/detail/-/0964629100/qid=1110111176/sr=8-1/ref=sr_8_xs_ap_i1_xgl14/002-6970964-3477663?v=glance&s=books&n=507846
Thanks for the links anyways.
Are you saying that the structure of time/space is what set the limit
of
the speed of light. In other words, you change the structure of
space/time.
The speed of light would change in value?? I wasnt contemplating how
come
time doesn't slow down to a crawl at 50 feet / second but only near
relativistic speed. What set the rule. It's the structure of
space/time?
Anyway. I'll read the links. Thanks.
P.
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| User: "Bill Hobba" |
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| Title: Re: What really is "Light" (assuming SR is correct)?? |
07 Mar 2005 12:01:26 AM |
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"phoenix" <photonixx@go.com> wrote in message
news:1110111798.863844.123380@o13g2000cwo.googlegroups.com...
Bill Hobba wrote:
"phoenix" <photonixx@go.com> wrote in message
news:1110103716.231214.134730@o13g2000cwo.googlegroups.com...
Morituri-|-Max wrote:
Light imposes limits on space-time, setting an absolute
limit for the velocity of any object and distorting the
dimensional relations of objects that approach that
velocity. But what does light have to do with how fast
I think you are starting bass-ackwards.. light doesn't "impose"
anything on
anything, any more than fire imposes flammability on you when you
are
covered with napalm.
Light is subject to the effects of curved space.
I mean. As you go near the speed of light. Your mass
would increase and time would slow down.
As has been explained many time on this forum mass does not increase
with
velocity.
When you
hit C, your mass becomes infinite.
Since a massive object can not travel a c the above is a nonsense
statement.
Why is C so special?
It isn't. Its value is simply an artifact of the units used. In
natural
units its value is one.
Why can light cause all that or relate to
them if light is just photons?
You are confused . Light causes nothing of the sort. The fact
photons have
zero mass (at least as far as we can tell) is why they travel at the
invariant speed predicted by relativity.
I was reading a book by Sam Avery where he stated that light is special
and relate to all that because space and time is inside our mind. Guess
the author is not well acquainted in relativity.
I suspect not. The real basis of SR is the principle of relativity (POR)
http://www.amazon.com/exec/obidos/tg/detail/-/0964629100/qid=1110111176/sr=8-1/ref=sr_8_xs_ap_i1_xgl14/002-6970964-3477663?v=glance&s=books&n=507846
Thanks for the links anyways.
Are you saying that the structure of time/space is what set the limit
of
the speed of light.
Yes.
In other words, you change the structure of
space/time.
Can you describe to me how you would change the structure of space time to
test your idea? If you can not then it really is a meaningless question.
The speed of light would change in value?? I wasnt contemplating how
come
time doesn't slow down to a crawl at 50 feet / second but only near
relativistic speed. What set the rule. It's the structure of
space/time?
The rules are determined by the Lorentz transformation.
Anyway. I'll read the links. Thanks.
Happy reading. Enjoy.
Thanks
Bill
P.
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| User: "" |
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| Title: Re: What really is "Light" (assuming SR is correct)?? |
10 Mar 2005 11:25:29 AM |
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Light shouldn't be more special than other matter waves. Please see my
post below. it answers the spacetime as related to all waves from a
higher perspective.
http://groups-beta.google.com/group/sci.physics.relativity/browse_frm/thread/04f473ac65543719/37f2a0798be6479d#37f2a0798be6479d
qchiang
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| User: "PD" |
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| Title: Re: What really is "Light" (assuming SR is correct)?? |
07 Mar 2005 10:57:00 AM |
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phoenix wrote:
Bill Hobba wrote:
"phoenix" <photonixx@go.com> wrote in message
news:1110103716.231214.134730@o13g2000cwo.googlegroups.com...
Morituri-|-Max wrote:
Light imposes limits on space-time, setting an absolute
limit for the velocity of any object and distorting the
dimensional relations of objects that approach that
velocity. But what does light have to do with how fast
I think you are starting bass-ackwards.. light doesn't "impose"
anything on
anything, any more than fire imposes flammability on you when
you
are
covered with napalm.
Light is subject to the effects of curved space.
I mean. As you go near the speed of light. Your mass
would increase and time would slow down.
As has been explained many time on this forum mass does not
increase
with
velocity.
When you
hit C, your mass becomes infinite.
Since a massive object can not travel a c the above is a nonsense
statement.
Why is C so special?
It isn't. Its value is simply an artifact of the units used. In
natural
units its value is one.
Why can light cause all that or relate to
them if light is just photons?
You are confused . Light causes nothing of the sort. The fact
photons have
zero mass (at least as far as we can tell) is why they travel at
the
invariant speed predicted by relativity.
I was reading a book by Sam Avery where he stated that light is
special
and relate to all that because space and time is inside our mind.
Guess
the author is not well acquainted in relativity.
http://www.amazon.com/exec/obidos/tg/detail/-/0964629100/qid=1110111176/sr=8-1/ref=sr_8_xs_ap_i1_xgl14/002-6970964-3477663?v=glance&s=books&n=507846
Thanks for the links anyways.
Are you saying that the structure of time/space is what set the limit
of
the speed of light. In other words, you change the structure of
space/time.
The speed of light would change in value?? I wasnt contemplating how
come
time doesn't slow down to a crawl at 50 feet / second but only near
relativistic speed. What set the rule. It's the structure of
space/time?
Anyway. I'll read the links. Thanks.
P.
Change the structure of spacetime to what? Note that in sensible units,
the maximal velocity of causal objects is 1. Consider that number.
There is no number that is both nonzero, positive, and more "natural"
than 1. It seems almost impossible to imagine a maximal velocity that
is different than 1. What would be the alternative number? 16?
PD
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| User: "N:dlzc D:aol T:com \dlzc\ N: dlzc1 D:cox" |
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| Title: Re: What really is "Light" (assuming SR is correct)?? |
07 Mar 2005 12:14:09 PM |
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Dear PD:
"PD" <pdraper@yahoo.com> wrote in message
news:1110214620.560861.71920@o13g2000cwo.googlegroups.com...
....
Change the structure of spacetime to what? Note that in
sensible units,
the maximal velocity of causal objects is 1. Consider that
number.
There is no number that is both nonzero, positive, and more
"natural"
than 1. It seems almost impossible to imagine a maximal
velocity that
is different than 1. What would be the alternative number? 16?
42!
David A. Smith
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| User: "Morituri-|-Max" |
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| Title: Re: What really is "Light" (assuming SR is correct)?? |
06 Mar 2005 01:19:09 PM |
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"phoenix" <photonixx@go.com> wrote in message
news:1110103716.231214.134730@o13g2000cwo.googlegroups.com...
Morituri-|-Max wrote:
Light imposes limits on space-time, setting an absolute
limit for the velocity of any object and distorting the
dimensional relations of objects that approach that
velocity. But what does light have to do with how fast
I think you are starting bass-ackwards.. light doesn't "impose"
anything on
anything, any more than fire imposes flammability on you when you are
covered with napalm.
Light is subject to the effects of curved space.
I mean. As you go near the speed of light. Your mass
would increase and time would slow down. When you
hit C, your mass becomes infinite. Why is C so
special? Why can light cause all that or relate to
them if light is just photons?
There isn't anything special about C, any more than there is anything
special about water freezing at 0 degrees celsius.
You can't hit the speed of light if you have mass, only massless particles
can do that. One would suggest that you not get so wrapped up in the
concept of infinites. Unless you do the math that will only get you in
trouble with the english language doing some wierd semantic mumbo jumbo on
you.
Pls. illustrate in complete details. Thanks.
For what you are asking, first you need to get the basics down. Details is
what is messing you up as you are starting with false premises in several
things.
I've got to get to the bottom of all these...
Light & Relativity or I can't sleep.
Better take some sleeping meds and enroll in some physics courses fast then.
.
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| User: "Alex" |
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| Title: Re: What really is "Light" (assuming SR is correct)?? |
09 Mar 2005 06:35:43 AM |
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At school we learn Pythagoras' theorem:
h^2 = x^2 + y^2
This describes displacements on a plane.
In school maths we learn how to extend this to 3D:
r^2 = x^2 + y^2 + z^2
Modern Special Relativity (post 1908) is the proposal that the universe
is a four dimensional manifold with a metric (like Pythagoras' theorem)
given by:
s^2 = x^2 + y^2 + z^2 - (ct)^2
Where x, y, z are independent directions in space and ct is the
distance in METRES along the independent time axis (for simplicity a
displacement from the origin has been assumed and the space-time is
assumed to be flat).
The constant 'c' converts time to metres at the rate of approx.
300,000,000 metres for a second. If the universe is four dimensional
then all observers should obtain the same value for s^2 (things cannot
tilt out of the universe). 's' is known as the space-time interval. The
space-time interval is INVARIANT between observers.
If the 3D version of pythagoras' theorem is substituted into the four
dimensional equation:
s^2 = r^2 - (ct)^2
Where 'r' is simply the distance moved in time 't'. If an object is
moving at a velocity 'v' then:
s^2 = (vt)^2 - (ct)^2
and s^2 = t^2(v^2 - c^2)
c is a constant so a given value of s can be obtained by a wide range
of values of v and t. HOWEVER THERE IS ONE VALUE OF s THAT CAN ONLY
OCCUR FOR ONE VALUE OF v. When s=0 then v can only equal c. This means
that all observers will obtain the same value for v when v=c because
the space-time interval of zero is measured by all of them; remember,
the interval is INVARIANT between observers.
The velocity v = c is a universal constant.
If you explore relativity further you will discover that particles with
zero rest mass can move at c metres per second. Light seems to be
composed of such particles and it is for this reason, and historical
reasons, that c is known as the 'speed of light'.
Modern Relativity actually assumes that seconds are a measure of length
and 'c' is simply the conversion factor from seconds to metres (like
factors that convert from inches to centimetres etc.), it does not
assume that that the speed of light is constant. It predicts that the
speed of light is a universal constant.
This newsgroup has a number of contributors with various ideas about
the geometry of the universe, some believe that the universe is three
dimensional (ie: Presentists) some of whom claim time does not exist,
some are Galilean Relativists (who claim there is no geometrical
relationship between space and time), some are Ether Theorists (who
claim there is a preferred reference frame) and some propose other
metrics than the Minkowski metric. Most dissenters from modern physics
believe that the universe has a simple Pythagorean metric (ie: it is
wholly described by r^2 = x^2 + y^2 + z^2 and spatial length is
invariant).
Many of these are worthy points of view but they are not 'mainstream'.
The Minkowski metric is mainstream.
Best Wishes
Alex Green
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| User: "JM Albuquerque" |
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| Title: Re: What really is "Light" (assuming SR is correct)?? |
10 Mar 2005 05:17:38 PM |
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"Alex" <dralexgreen@yahoo.co.uk> escreveu na mensagem
news:1110371743.455127.60010@g14g2000cwa.googlegroups.com...
At school we learn Pythagoras' theorem:
h^2 = x^2 + y^2
This describes displacements on a plane.
In school maths we learn how to extend this to 3D:
r^2 = x^2 + y^2 + z^2
Modern Special Relativity (post 1908) is the proposal that the universe
is a four dimensional manifold with a metric (like Pythagoras' theorem)
given by:
s^2 = x^2 + y^2 + z^2 - (ct)^2
Where x, y, z are independent directions in space and ct is the
distance in METRES along the independent time axis (for simplicity a
displacement from the origin has been assumed and the space-time is
assumed to be flat).
The constant 'c' converts time to metres at the rate of approx.
300,000,000 metres for a second. If the universe is four dimensional
then all observers should obtain the same value for s^2 (things cannot
tilt out of the universe). 's' is known as the space-time interval. The
space-time interval is INVARIANT between observers.
If the 3D version of pythagoras' theorem is substituted into the four
dimensional equation:
s^2 = r^2 - (ct)^2
Where 'r' is simply the distance moved in time 't'. If an object is
moving at a velocity 'v' then:
s^2 = (vt)^2 - (ct)^2
and s^2 = t^2(v^2 - c^2)
Up to here everything is fine and correct.
c is a constant so a given value of s can be obtained by a wide range
of values of v and t. HOWEVER THERE IS ONE VALUE OF s THAT CAN ONLY
OCCUR FOR ONE VALUE OF v. When s=0 then v can only equal c. This means
that all observers will obtain the same value for v when v=c because
the space-time interval of zero is measured by all of them; remember,
the interval is INVARIANT between observers.
The velocity v = c is a universal constant.
WRONG.
If an object is moving at a velocity 'v' then:
s^2 = (vt)^2 - (ct)^2
And that's all.
Stop here.
The subject is about measuring displacements, right?
So if s=0 two physical situations can occur.
1 - The physical situation is static (not evolving in time);
2 - The physical situation is dynamic (evolving in time by means of light
travel required for the observer to do the measurement - The observer must
see by means of light what is happening at distance).
Case 1 applies:
s^2 = x^2 + y^2 + z^2
For case 2 my point is that s=0 is physically impossible,
or else it is a total absurd, since if s=0 nothing happens
at distance so that light speed has to be involved in the
measurement.
Or else, if something is moving at "c" the time interval
for which the observer travelling at "c" can do the
physical measurement that s=0 must be t=0.
(time stops remember?)
The time interval is zero (t=0).
This is a total absurd has I've mentioned.
Time doesn't stop, ever.
Any case:
s^2 = (vt)^2 - (ct)^2
And that's all.
Stop here.
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| User: "Franz Heymann" |
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| Title: Re: What really is "Light" (assuming SR is correct)?? |
11 Mar 2005 01:31:45 AM |
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"JM Albuquerque" <jm.aREM.OVE@sapo.pt> wrote in message
news:39c2cmF618h2nU1@individual.net...
"Alex" <dralexgreen@yahoo.co.uk> escreveu na mensagem
news:1110371743.455127.60010@g14g2000cwa.googlegroups.com...
At school we learn Pythagoras' theorem:
h^2 = x^2 + y^2
This describes displacements on a plane.
In school maths we learn how to extend this to 3D:
r^2 = x^2 + y^2 + z^2
Modern Special Relativity (post 1908) is the proposal that the
universe
is a four dimensional manifold with a metric (like Pythagoras'
theorem)
given by:
s^2 = x^2 + y^2 + z^2 - (ct)^2
Where x, y, z are independent directions in space and ct is the
distance in METRES along the independent time axis (for simplicity
a
displacement from the origin has been assumed and the space-time
is
assumed to be flat).
The constant 'c' converts time to metres at the rate of approx.
300,000,000 metres for a second. If the universe is four
dimensional
then all observers should obtain the same value for s^2 (things
cannot
tilt out of the universe). 's' is known as the space-time
interval. The
space-time interval is INVARIANT between observers.
If the 3D version of pythagoras' theorem is substituted into the
four
dimensional equation:
s^2 = r^2 - (ct)^2
Where 'r' is simply the distance moved in time 't'. If an object
is
moving at a velocity 'v' then:
s^2 = (vt)^2 - (ct)^2
and s^2 = t^2(v^2 - c^2)
Up to here everything is fine and correct.
It's nice of you to say so.
c is a constant so a given value of s can be obtained by a wide
range
of values of v and t. HOWEVER THERE IS ONE VALUE OF s THAT CAN
ONLY
OCCUR FOR ONE VALUE OF v. When s=0 then v can only equal c. This
means
that all observers will obtain the same value for v when v=c
because
the space-time interval of zero is measured by all of them;
remember,
the interval is INVARIANT between observers.
The velocity v = c is a universal constant.
WRONG.
No right. Go on rereading till you understand.
Don't bother with further comments till you do, lest you heap scorn on
yourself yet again.
If an object is moving at a velocity 'v' then:
s^2 = (vt)^2 - (ct)^2
And that's all.
Stop here.
The subject is about measuring displacements, right?
So if s=0 two physical situations can occur.
1 - The physical situation is static (not evolving in time);
2 - The physical situation is dynamic (evolving in time by means of
light
travel required for the observer to do the measurement - The
observer must
see by means of light what is happening at distance).
Case 1 applies:
s^2 = x^2 + y^2 + z^2
For case 2 my point is that s=0 is physically impossible,
You are talking nonsense, as I predicted.
or else it is a total absurd, since if s=0 nothing happens
at distance so that light speed has to be involved in the
measurement.
No. ds = 0 when dr = d(ct)
Or else, if something is moving at "c" the time interval
for which the observer travelling at "c" can do the
physical measurement that s=0 must be t=0.
(time stops remember?)
No.
The time interval is zero (t=0).
This is a total absurd has I've mentioned.
Time doesn't stop, ever.
Any case:
s^2 = (vt)^2 - (ct)^2
And that's all.
Stop here.
No.
Essentially everything you said was wrong, and all decuctions from
your approach which are amenable to experimsntal observation have
been shown experimentally not to be true.
You know as little abour SR as you know about EM. Why do you bother
to post in the vein you do?
You should be asking questions, not making wrong ex-cathedra
assertions.
--
Franz
"A first-rate laboratory is one in which mediocre scientists can
produce outstanding work"
P.M.S. Blackett
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| User: "JM Albuquerque" |
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| Title: Re: What really is "Light" (assuming SR is correct)?? |
11 Mar 2005 10:14:32 AM |
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"Franz Heymann" <notfranz.heymann@btopenworld.com> escreveu na mensagem
news:d0rhh0$csr$1@nwrdmz04.dmz.ncs.ea.ibs-infra.bt.com...
"JM Albuquerque" <jm.aREM.OVE@sapo.pt> wrote in message
news:39c2cmF618h2nU1@individual.net...
(snip)
For case 2 my point is that s=0 is physically impossible,
You are talking nonsense, as I predicted.
Take it easy Dear Franz Heymann.
I've presented an argument and I've explained why it's impossible.
This subject is the heart, or the most critical point for us to
understand the universe, or not.
Alex Green has presented a very good post and now a very good
reply to mine. I'm trying to understand this subject.
My point is that s=0 is a singularity, or an undefined situation
which must be physically impossible, because it leads to a
situation where time must stop for a photon.
(snip)
No.
Essentially everything you said was wrong, and all decuctions from
your approach which are amenable to experimsntal observation have
been shown experimentally not to be true.
Essentially all you say is "no".
About the usual experimental observation you claim to support the
theory, so far I've been able to understand and argument against
all of them.
And I have a set of facts, or experiments, that looks to contradict
the theory.
Moreover I understand the theory of relativity and the theory is right
within a given set of assumptions that I will try to address in a future
reply to Alex Green.
I'm not against the theory. I'm just trying to grind the imperfections.
My point is that SR applies to all the situation where the observer
must see by means of light travel what is happening at distance.
In other words, SR applies and is 100% correct when the observer
is looking into the past.
Because the speed of light is not infinite, but "c", we are always
seeing the past, never the present.
Nevertheless there are limits and for sure s=0 and t=0 is a
singularity since nothing can stop in time (no past, no present,
no future for it).
You know as little abour SR as you know about EM. Why do you bother
to post in the vein you do?
I don't post in vein.
I always present arguments.
It is up to you to show my arguments wrong and then present your
arguments and show why your arguments are the right ones.
Usually you don't pass step one.
You should be asking questions, not making wrong ex-cathedra
assertions.
Why asking questions for which I already know the answer?
I do know very well what cathedra assertions are, but I don't
belong to the club.
A good physicist, like any good engineer, must be always
looking for situations where something could be wrong.
The good ones never assume everything must be fine and
they are always looking for a better solution.
.
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| User: "Bilge" |
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| Title: Re: What really is "Light" (assuming SR is correct)?? |
11 Mar 2005 05:06:34 PM |
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JM Albuquerque:
"Franz Heymann" <notfranz.heymann@btopenworld.com> escreveu na mensagem
news:d0rhh0$csr$1@nwrdmz04.dmz.ncs.ea.ibs-infra.bt.com...
"JM Albuquerque" <jm.aREM.OVE@sapo.pt> wrote in message
news:39c2cmF618h2nU1@individual.net...
(snip)
For case 2 my point is that s=0 is physically impossible,
You are talking nonsense, as I predicted.
Take it easy Dear Franz Heymann.
I've presented an argument and I've explained why it's impossible.
Experimental data trumps your explanation.
This subject is the heart, or the most critical point for us to
understand the universe, or not.
Alex Green has presented a very good post and now a very good
reply to mine. I'm trying to understand this subject.
My point is that s=0 is a singularity, or an undefined situation
which must be physically impossible, because it leads to a
situation where time must stop for a photon.
What's your point?
No.
Essentially everything you said was wrong, and all decuctions from
your approach which are amenable to experimsntal observation have
been shown experimentally not to be true.
Essentially all you say is "no".
About the usual experimental observation you claim to support the
theory, so far I've been able to understand and argument against
all of them.
If that's the case, how do you explain your post indicating
otherwise?
And I have a set of facts, or experiments, that looks to contradict
the theory.
You mean you've performed an experiment that disproves relativity?
If so, you should be writing it up for publication rather than posting
here.
Moreover I understand the theory of relativity and the theory is right
within a given set of assumptions that I will try to address in a future
reply to Alex Green.
I'm not against the theory. I'm just trying to grind the imperfections.
My point is that SR applies to all the situation where the observer
must see by means of light travel what is happening at distance.
Light is irrelevant to relativity. If you understood the theory, you
would know this.
In other words, SR applies and is 100% correct when the observer
is looking into the past.
Because the speed of light is not infinite, but "c", we are always
seeing the past, never the present.
Nevertheless there are limits and for sure s=0 and t=0 is a
singularity since nothing can stop in time (no past, no present,
no future for it).
That is a very common misconception due to the abundance of
bad popular literature about relativity. There is no substitute
for a real physics textbook.
[...]
A good physicist, like any good engineer, must be always
looking for situations where something could be wrong.
So, why aren't you taking a serious look at newtonian mechanics?
How about arithmetic? It's always possible that 2+2 = 5.
The good ones never assume everything must be fine and
they are always looking for a better solution.
The good ones understand enough to know that a better solution
doesn't lie in trying to disprove mathematics of geometry.
.
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| User: "Franz Heymann" |
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| Title: Re: What really is "Light" (assuming SR is correct)?? |
12 Mar 2005 02:45:36 PM |
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"JM Albuquerque" <jm.aREM.OVE@sapo.pt> wrote in message
news:39dtvdF6184b8U1@individual.net...
"Franz Heymann" <notfranz.heymann@btopenworld.com> escreveu na
mensagem
news:d0rhh0$csr$1@nwrdmz04.dmz.ncs.ea.ibs-infra.bt.com...
"JM Albuquerque" <jm.aREM.OVE@sapo.pt> wrote in message
news:39c2cmF618h2nU1@individual.net...
(snip)
For case 2 my point is that s=0 is physically impossible,
You are talking nonsense, as I predicted.
Take it easy Dear Franz Heymann.
I've presented an argument and I've explained why it's impossible.
You haven't done anything of the kind.
You are totally unfamiliar with SR and you are simply maku=ing a fool
of yourself by attempting to comment on it from the sidelines.
You should be asking questions, not laying down the law.
This subject is the heart, or the most critical point for us to
understand the universe, or not.
Alex Green has presented a very good post and now a very good
reply to mine. I'm trying to understand this subject.
My point is that s=0 is a singularity,
You clearly have no idea of the definition of a singularity.
or an undefined situation
No, it is very well defined. It describes the trajectory of a photon.
which must be physically impossible, because it leads to a
situation where time must stop for a photon.
Balls.
There is no such thing as "for a photon". The photon does not have a
rest frame. In free space it travels at c relative to any inertial
frame whatsoever.
(snip)
No.
Essentially everything you said was wrong, and all decuctions from
your approach which are amenable to experimsntal observation have
been shown experimentally not to be true.
Essentially all you say is "no".
You hit the nail on the head.
About the usual experimental observation you claim to support the
theory, so far I've been able to understand and argument against
all of them.
That would be nonsensical, since *all* the predictions made by SR for
measurable observations have turned out to support the predictions.
And I have a set of facts, or experiments, that looks to contradict
the theory.
You have nothing of the kind.
Moreover I understand the theory of relativity
No, you clearly don't, or you would have understood the nature of null
intervals.
and the theory is right
within a given set of assumptions that I will try to address in a
future
reply to Alex Green.
The dynamics which has been derived from the first principles of SR as
a replacement for Newton's equations have turned out to be spot on in
*all* the cases in which they have been tested, and they are routinely
tested thousands of times daily at every high energy lab in the
world.
I'm not against the theory. I'm just trying to grind the
imperfections.
The imperfections are in your mind, not in the theory.
My point is that SR applies to all the situation where the observer
must see by means of light travel what is happening at distance.
That would represent a negligible fraction of the present day
applications of SR.
All that nonsense of shining lights at moving objects originated
simply as a pedagogical tool used by Einstein a century ago. There
are now much better approaches to the theory.
In other words, SR applies and is 100% correct when the observer
is looking into the past.
Nonsense.
Because the speed of light is not infinite, but "c", we are always
seeing the past, never the present.
That is a quite trite observation, and by itself it has very little to
do with relativity.
Nevertheless there are limits and for sure s=0 and t=0 is a
singularity since nothing can stop in time (no past, no present,
no future for it).
I suggest you have had your mileage about s = 0 for now. You would be
wise to postpone further reference to it until you have actually got
to grips with what SR is about.
You know as little abour SR as you know about EM. Why do you
bother
to post in the vein you do?
I don't post in vein.
THere is a difference between "in vain" and "in the vein you do"
I always present arguments.
No, you don't. You usually present some mishmash of your own
misunderstandings.
It is up to you to show my arguments wrong and then present your
arguments and show why your arguments are the right ones.
Usually you don't pass step one.
The only argument I see you having produced is the one which
encapsulates your lack of understanding of the null interval. I coped
with that.
You should be asking questions, not making wrong ex-cathedra
assertions.
Why asking questions for which I already know the answer?
Oh dear
I do know very well what cathedra assertions are, but I don't
belong to the club.
The word is ex-cathedra
A good physicist, like any good engineer, must be always
looking for situations where something could be wrong.
Ninety percent of the time that would be a total waste of time
It certainly is a waste of time to go on babbling about SR, which,
together with quantum mechanics, are the most soundly based of all
physical theories.
The good ones never assume everything must be fine and
they are always looking for a better solution.
--
Franz
"A first-rate laboratory is one in which mediocre scientists can
produce outstanding work"
P.M.S. Blackett
.
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| User: "Alex" |
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| Title: Re: What really is "Light" (assuming SR is correct)?? |
11 Mar 2005 04:45:18 AM |
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You (JM Albuquerque) wrote: "For case 2 my point is that s=0 is
physically impossible, or else it is a total absurd, since if s=0
nothing happens at distance so that light speed has to be involved in
the measurement. "
You are posing the question: is s=0 physically impossible if 's' is the
space-time interval of a photon? I'll try to answer this.
Take the Minkowski metric: s^2 = x^2 + y^2 + z^2 - (ct)^2 and simplify
it as before for a point object moving at velocity v relative to John:
s^2 = (vt)^2 - (ct)^2
John measures the space-time interval of the moving point to be
composed of BOTH space and time.
Suppose Bill is actually sitting at the point. According to Galilean
relativity or Special Relativity Bill may think he is not moving and it
is John who is moving. Bill thinks he is stationary so he measures the
space-time interval of the same object (himself) as something that ONLY
moves in time (for T secs).
s^2 = (0)^2 - (cT)^2
But these intervals apply to the same object. In a four dimensional
universe 's' would be invariant, apply to the same object and have the
same value for both Bill and John so:
(0)^2 - (cT)^2 = (vt)^2 - (ct)^2
(cT)^2 = (ct)^2 - (vt)^2
So T = t sqrt(1-v^2/c^2)
Which is the SR transformation for time intervals (not to be confused
with the Lorentz transformation for absolute times).
It was shown above that the value v=c is the same for all observers so
t=cx and T=cX are valid for both John and Bill hence:
X = x sqrt(1-v^2/c^2)
This is the SR formula for length contraction. Now lets return to the
question, is s=0 physically impossible if 's' is the space-time
interval of a photon? We will suppose Bill is a photon with v=c. John's
clocks have an interval of 2 secs, John observes Bill's clocks to read
an interval T where:
T = t sqrt(1-v^2/c^2)
T = 2 sqrt(1- 1)
so T =0
John sees Bill's length measurement for distance travelled as
X = x sqrt(1-v^2/c^2)
X = x sqrt(1- 1)
X = 0
So John can only assume that, at the speed of light, Bill finds there
is indeed no separation between two points on Johns x axis in the
direction of motion. Now, I suspect you can allow this with the caveat
that we are just 'trying out' a Minkowski metric. I bet your problem is
with the other point of view, surely John knows that there is indeed a
separation between two points on his OWN x axis. Whatever Bill measures
John is still left with some actual space!
Of course, John DOES have some actual space, if he measures a length,
r, he measures both ends of r at the same time. Both ends are measured
simultaneously so t=0. The space time interval for a length measurement
is:
given r^2 = x^2 + y^2 + z^2
s^2 = r^2 - (ct)^2
But t=0 so:
s^2 = r^2
In this case, of a PURE LENGTH MEASUREMENT s^2 is never zero.
So what is the meaning of s^2 = x^2 + y^2 + z^2 - (ct)^2 for John when
s=0? 's' is not the distance travelled by Bill in his incarnation as a
photon (this is r) and it is not the time occupied by Bill in John's
frame of reference (this is t). It is the length of a combination of
displacements in space and time in the direction of Bill's motion, a
thing that cannot be measured directly with either a ruler or a clock.
The maths tells us that for John, as for Bill this length is zero.
Your comment that a photon could not measure time intervals of zero is
quite true. This brings us back to the theme of this thread - what on
earth is a photon? All we know is that it is an interaction between
two events. We cannot observe it 'in flight', in fact when it is 'in
flight', according to QM and QED, it seems to explore the whole
universe simultaneously!
I can sense from your comments that you are not going to accept this
argument because you have an intuitive idea of time. Physicists have
long been aware of the conflict between our intuitive idea of time and
Special Relativity. As early as 1918 Weyl noted that SR suggests a
block time universe where all events coexist. He proposed that
'becoming' is a property of conscious observation. To put this another
way, there can be no doubt that SR is a provisional theory and equally
little doubt that it applies within the constraints of a simple
Minkowskian universe. It is likely that the universe is far more
complex than the simple Minkowskian case and we will need to understand
this complexity to understand the conscious observer.
In this context the recent 'double slit experiment in time' is of huge
interest because it provides experimental evidence for block time.
Events are indeed laid out so that they coexist with the present. Our
problem is how to account for our observation that intuitive time
passes and to do this we must progress forward from relativity to a
more complete physics. There is no going back.
Best Wishes
Alex Green
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| User: "JM Albuquerque" |
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| Title: Re: What really is "Light" (assuming SR is correct)?? |
11 Mar 2005 01:47:23 PM |
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"Alex" <dralexgreen@yahoo.co.uk> escreveu na mensagem
news:1110537918.814725.203970@f14g2000cwb.googlegroups.com...
You (JM Albuquerque) wrote: "For case 2 my point is that s=0 is
physically impossible, or else it is a total absurd, since if s=0
nothing happens at distance so that light speed has to be involved in
the measurement. "
You are posing the question: is s=0 physically impossible if 's' is the
space-time interval of a photon?
Yes.
I'll try to answer this.
Take the Minkowski metric: s^2 = x^2 + y^2 + z^2 - (ct)^2 and simplify
it as before for a point object moving at velocity v relative to John:
s^2 = (vt)^2 - (ct)^2
John measures the space-time interval of the moving point to be
composed of BOTH space and time.
Yes.
I assume John is stopped and the point object moving at
velocity v relative to John, so that:
s^2 = (vt)^2 - (ct)^2
Suppose Bill is actually sitting at the point.
Let me see if I understand it correctly.
I assume that Bill is actually sitting at the object moving at
velocity v relative to John.
We have John and also we have Bill glued with the moving
object.
Both John and Bill are taking measurements of the
distance between both, or what are they measuring ?
I presume that John is trying to measure its distance
relative to the moving object:
s^2 = (vt)^2 - (ct)^2
And Bill is also measuring its distance to the object
where it is sited? Is Bill trying to measure its speed
relative to himself? That's is absurd.
According to Galilean
relativity or Special Relativity Bill may think he is not moving and it
is John who is moving. Bill thinks he is stationary so he measures the
space-time interval of the same object (himself) as something that ONLY
moves in time (for T secs).
s^2 = (0)^2 - (cT)^2
I don't think so.
Bill is sitting on the moving object, but Bill thinks he is stationary
and it is John who is moving.
Bill still wants to measure its distance relative to John.
So Bill sees John moving at v by means of light, so that:
s^2 = (vt)^2 - (ct)^2
Both see s^2 = (vt)^2 - (ct)^2
Something must be wrong.
Where did I went wrong?
I guess I cannot understand your following statement:
«««Bill thinks he is stationary so he measures the
space-time interval of the same object (himself) as
something that ONLY moves in time (for T secs).
s^2 = (0)^2 - (cT)^2 »»»
Both John and Bill are trying to measure distance
relative to each other I presume, and there is a
relative speed between both. None of them can
tell whom is moving and whom is stopped
The argument is circular and you cannot say that
Bill's vision is different from John's vision, so that
one measures distance composed by space and
time and the other only sees the same invariant
distance composed by time.
The measurement of a distance must be made
in no time so that both can measure the same value.
If the measurement of a distance takes for instance
one second to be made the distance error will be
of 300,000 km.
Please enlighten me.
But these intervals apply to the same object. In a four dimensional
universe 's' would be invariant, apply to the same object and have the
same value for both Bill and John so:
(0)^2 - (cT)^2 = (vt)^2 - (ct)^2
(cT)^2 = (ct)^2 - (vt)^2
So T = t sqrt(1-v^2/c^2)
Which is the SR transformation for time intervals (not to be confused
with the Lorentz transformation for absolute times).
Nonsense.
Bill is sitting on the object and he must always measure s=0 between himself
and the object, just because Bill is sited on the object (obvious and
irrefutable).
On the contrary John sees the object at distance, by means of light travel
and so there is always a non-zero distance between John and the object,
except in the precise moment where they all crash against each others.
It was shown above that the value v=c is the same for all observers so
t=cx and T=cX are valid for both John and Bill hence:
X = x sqrt(1-v^2/c^2)
This is the SR formula for length contraction. Now lets return to the
question, is s=0 physically impossible if 's' is the space-time
interval of a photon? We will suppose Bill is a photon with v=c. John's
clocks have an interval of 2 secs, John observes Bill's clocks to read
an interval T where:
T = t sqrt(1-v^2/c^2)
T = 2 sqrt(1- 1)
so T =0
John sees Bill's length measurement for distance travelled as
X = x sqrt(1-v^2/c^2)
X = x sqrt(1- 1)
X = 0
So John can only assume that, at the speed of light, Bill finds there
is indeed no separation between two points on Johns x axis in the
direction of motion.
At speed of light time stops, distance don't exist and nothing could
possible make any sense at all. No past, no present, no future.
Now, I suspect you can allow this with the caveat
that we are just 'trying out' a Minkowski metric. I bet your problem is
with the other point of view, surely John knows that there is indeed a
separation between two points on his OWN x axis. Whatever Bill measures
John is still left with some actual space!
Of course.
That is obvious.
Of course, John DOES have some actual space, if he measures a length,
r, he measures both ends of r at the same time. Both ends are measured
simultaneously so t=0. The space time interval for a length measurement
is:
given r^2 = x^2 + y^2 + z^2
s^2 = r^2 - (ct)^2
But t=0 so:
s^2 = r^2
In this case, of a PURE LENGTH MEASUREMENT s^2 is never zero.
Of course.
That is obvious.
So what is the meaning of s^2 = x^2 + y^2 + z^2 - (ct)^2 for John when
s=0? 's' is not the distance travelled by Bill in his incarnation as a
photon (this is r) and it is not the time occupied by Bill in John's
frame of reference (this is t). It is the length of a combination of
displacements in space and time in the direction of Bill's motion, a
thing that cannot be measured directly with either a ruler or a clock.
If cannot be measured directly with either a ruler or a clock it has
no physical meaning at all.
The maths tells us that for John, as for Bill this length is zero.
Maths is nothing for me.
All I care is about physics.
Your comment that a photon could not measure time intervals of zero is
quite true.
Indeed.
Believe me, it's quite true.
This brings us back to the theme of this thread - what on
earth is a photon? All we know is that it is an interaction between
two events. We cannot observe it 'in flight', in fact when it is 'in
flight', according to QM and QED, it seems to explore the whole
universe simultaneously!
Of course we cannot observe a photon 'in flight'.
Time intervals and distances for a photon 'in flight' are always zero.
A photon has no past, no present and no future.
I can sense from your comments that you are not going to accept this
argument because you have an intuitive idea of time. Physicists have
long been aware of the conflict between our intuitive idea of time and
Special Relativity. As early as 1918 Weyl noted that SR suggests a
block time universe where all events coexist.
Indeed.
I agree 100%.
All events must coexist for a photon 'in flight'.
He proposed that
'becoming' is a property of conscious observation. To put this another
way, there can be no doubt that SR is a provisional theory and equally
little doubt that it applies within the constraints of a simple
Minkowskian universe.
No doubt that SR is a provisional theory.
History teach us that no theory is forever.
It is likely that the universe is far more
complex than the simple Minkowskian case and we will need to understand
this complexity to understand the conscious observer.
Of course the Universe is much more complex.
In this context the recent 'double slit experiment in time' is of huge
interest because it provides experimental evidence for block time.
Events are indeed laid out so that they coexist with the present. Our
problem is how to account for our observation that intuitive time
passes and to do this we must progress forward from relativity to a
more complete physics. There is no going back.
I'm starting to think that Physicists are nuts or simple parrots,
I don't know for sure.
Now I'm thinking about two facts that contradict SR and the said
Minkowskian universe.
1 - Pioneer 10/11 anomalous acceleration equal to Hubble's
constant, even with the wrong sign, that can explain the all
misconception when one explains how to convert the wrong
sign into the right sign.
2 - Non aberration of gravity between Sun and Earth, that
will exist and will cause the Earth to slow down, if one assumes
that gravity waves exist and they travel at the speed of light,
for starters.
Best Wishes and congratulations for your clear mind.
Best Wishes
Alex Green
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| User: "Alex" |
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| Title: Re: What really is "Light" (assuming SR is correct)?? |
12 Mar 2005 05:47:41 AM |
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You (JM Albuquerque) wrote: "And Bill is also measuring its distance to
the object where it is sited? Is Bill trying to measure its speed
relative to himself? That's is absurd.
In a four dimensional universe an object that is not moving in space
can be moving in time relative to a conscious observer so Bill can
measure how far he moves along his own time axis. Bill can measure the
time that elapses after John flashes past him by looking at a clock.
The 'space-time interval' due to a path through time is:
if: s^2 = R^2 - (cT)^2
and x=0, y=0, z=0 then
s^2 = (0) - (cT)^2
This expresses the space time interval traversed by an observer holding
a clock in his lap. The interval is only composed of time for observer
Bill. To another observer, John, Bill may appear to be traversing space
as well as time. Suppose the start of the interval occurs as John and
Bill meet, if t is the interval on John's clock then John measures
Bill's space-time interval as:
s^2 = r^2 - (ct)^2
You wrote that "Bill is sitting on the object and he must always
measure s=0 between himself and the object, just because Bill is sited
on the object (obvious and irrefutable). "
Bill does indeed measure 0 distance between himself and the object but
time still progresses so he measures T seconds between the start of the
interval and its end. Although spatial distance is zero the space time
interval has the value -cT seconds Furthermore, when John looks at Bill
he thinks Bill is an idiot because he seems to be regarding his path as
purely a path through time whereas, to John, Bill is going through both
time and space.
You wrote: "On the contrary John sees the object at distance, by means
of light travel and so there is always a non-zero distance between John
and the object, except in the precise moment where they all crash
against each others"
The spatial distance between John and Bill is as you say. Which brings
us back to the nature of the space-time interval. When there is no time
component to the interval it is simply a length. When there is no space
component it is simpy a time interval. But what is the space-time
interval when it is a mixture of time and space components? In fact
this was an active topic of debate between 1908 and the mid 1920s. The
conclusion of this debate seems to have been 'shut up and calculate'.
However, I think the four dimensionalists are quite clear, if never
explicit, about the space-time interval. Spacetime is a manifold of
PATHS. Every space-time interval is a completed path from one place
and time to another. Consider someone walking 10 metres at 1 m/sec,
the space time interval is:
s^2 = (10)^2 - (300,000,000 * 10) ^2
So:
s^2 ~ - (300,000,000 * 10) ^2
Hence the space-time interval is very nearly 10 seconds or 3000,000,000
metres. It is pointless to ask "how long would it take to travel along
this 3000,000,000 metres?". The answer is already known, it takes 10
seconds for the walker. Space-time intervals are already paths, they
have already been travelled. Most importantly they are unique, the path
traversed by the walker cannot be traversed by anyone or anything else,
it is a unique 'world line' of the walker.
Returning to photons, the space-time interval of a photon is, as far as
is known, zero for all observers. This zero length might stretch from
an observer to a place a light second away. How long does it take to
travel along this this zero length interval, a path that extends from
time=0, x=0 to time=1, x=300,000 km? The answer is already in the path,
it takes 1 second in the observer's space-time.
So how can a zero-length interval connect two places that are a real
spatial distance apart? Imagine a line drawn along a length of one
light second, if we rotate this line downwards infinitessimally into
the time axis it becomes a PATH from about 1 light second away to the
origin. If the line is rotated so it has one end at 0,0 and the other
at 1,-1 it is the path of a photon aimed diagonally through space-time
at the observer. In this direction and this direction ONLY, it has a
length of zero metres.
You wrote about such an interval that "If (it) cannot be measured
directly with either a ruler or a clock it has no physical meaning at
all." I am inclined to agree with you. What we must do is send
something with rulers and clocks along a path that goes from (almost)
1,-1 to 0,0. This has been done in particle accelerators. As expected
the results suggest that a thing that (nearly) follows the path of a
photon measures this path to have no length and take no time!
The four dimensional approach has been very successful and the
insights of the Dirac equation, QED, QCD etc. have all sprung from
these calculations. In fact, until the 1980s theoretical physics was
like an unstoppable express train using the twin pillars of Relativity
and QM as impetus. What about previous theories?
Galilean relativity simply suggests that time and space are unrelated
and does not propose any 'ether' etc. The relationships of modern
physics simply cannot be derived from Galilean relativity alone.
Ether theory can coexist with either Galilean Relativity or Special
Relativity. A whale would, quite rightly, believe in an ether theory
of light propagation because the oceans would be an ether. This is not
incompatible with SR.
Ether Theory plus Galilean relativity plus a set of assumptions about
electromagnetism can generate Lorentz transformations but needs clumsy
extra assumptions at every step to predict the Dirac equation etc. The
chief motivation for this combination is to preserve the prejudice of
'presentism'. There are powerful motivations for presentism, such as a
belief in free-will and Augustinian theology (God is eternal, man is in
the present). Unfortunately there is no evidence for presentism. If
free-will exists we will find the rationale for it as physics evolves
towards ever more accurate descriptions of the universe.
You wrote: "Now I'm thinking about two facts that contradict SR and the
said
Minkowskian universe.
1 - Pioneer 10/11 anomalous acceleration equal to Hubble's
constant, even with the wrong sign, that can explain the all
misconception when one explains how to convert the wrong
sign into the right sign.
2 - Non aberration of gravity between Sun and Earth, that
will exist and will cause the Earth to slow down, if one assumes
that gravity waves exist and they travel at the speed of light,
for starters. "
These could indeed be evidence for amendments to physical theory.
However the last century of physics does 'hang together', it is an
integrated whole. QM, QED and QCD are derived from SR (not GR). There
are many everyday observations including kinetic energy, magnetism, the
properties of dielectrics, and electron microscopy that support QM and
SR. It is possible that some combination of ether theory and SR might
be needed or that there is a fifth extensive time dimension accessible
to consciousness etc.... but these would all leave SR in place.
Best Wishes
Alex Green
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| User: "Franz Heymann" |
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| Title: Re: What really is "Light" (assuming SR is correct)?? |
10 Mar 2005 02:19:44 AM |
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"Alex" <dralexgreen@yahoo.co.uk> wrote in message
news:1110371743.455127.60010@g14g2000cwa.googlegroups.com...
At school we learn Pythagoras' theorem:
h^2 = x^2 + y^2
This describes displacements on a plane.
In school maths we learn how to extend this to 3D:
r^2 = x^2 + y^2 + z^2
Modern Special Relativity (post 1908) is the proposal that the
universe
is a four dimensional manifold with a metric (like Pythagoras'
theorem)
given by:
s^2 = x^2 + y^2 + z^2 - (ct)^2
Where x, y, z are independent directions in space and ct is the
distance in METRES along the independent time axis (for simplicity a
displacement from the origin has been assumed and the space-time is
assumed to be flat).
The constant 'c' converts time to metres at the rate of approx.
300,000,000 metres for a second. If the universe is four dimensional
then all observers should obtain the same value for s^2 (things
cannot
tilt out of the universe). 's' is known as the space-time interval.
The
space-time interval is INVARIANT between observers.
If the 3D version of pythagoras' theorem is substituted into the
four
dimensional equation:
s^2 = r^2 - (ct)^2
Where 'r' is simply the distance moved in time 't'. If an object is
moving at a velocity 'v' then:
s^2 = (vt)^2 - (ct)^2
and s^2 = t^2(v^2 - c^2)
c is a constant so a given value of s can be obtained by a wide
range
of values of v and t. HOWEVER THERE IS ONE VALUE OF s THAT CAN ONLY
OCCUR FOR ONE VALUE OF v. When s=0 then v can only equal c. This
means
that all observers will obtain the same value for v when v=c because
the space-time interval of zero is measured by all of them;
remember,
the interval is INVARIANT between observers.
The velocity v = c is a universal constant.
That is the cleanest deduction of the invariance of c to have been put
explicitly in thisg for a long time.
No endless, boring, farting around switching torches on and off in
trains and on the stations.
It is the deduction which I used for a decade in my lectures.
Alex,
Why do you think this intuitive
s^2 = dr^2 + (ict)^2
which connects so easily with Euclid's geometry
has been replaced by
s^2 = (ct^)2 - r^2 ?
which has a horrible built-in asymmetry and reverses the role of r ?
--
Franz
"A first-rate laboratory is one in which mediocre scientists can
produce outstanding work"
P.M.S. Blackett
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| User: "Alex" |
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| Title: Re: What really is "Light" (assuming SR is correct)?? |
11 Mar 2005 06:06:34 AM |
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Franz, Kip Thorne addresses this issue in his new book:
http://www.pma.caltech.edu/Courses/ph136/yr2004/0401.1.K.pdf
"One approach, often used in elementary textbooks [and also used in
Goldstein's (1980) Classical Mechanics and in the first edition of
Jackson's Classical Electrodynamics], is to set x0 =3D it, where i =3D
sqrt(-1)and correspondingly make the time basis
vector be imaginary, so that ~e ~e =3D (scalar product a.b=3D delta
ab). When this approach is adopted, the resulting
formalism does not care whether indices are placed up or down; one can
place them wherever one's stomach or liver dictate without asking one's
brain. However, this x0 =3D it approach has severe disadvantages: (i) it
hides the true physical geometry of Minkowski spacetime, (ii) it cannot
be extended in any reasonable manner to non-orthonormal bases in at
spacetime, and (iii) it cannot be extended in any reasonable manner to
the curvilinear coordinates that one must use in general relativity.
For this reason, most advanced texts [including the second and third
editions of Jackson (1999)] and all general relativity texts take an
alternative approach, which we also adopt in this book. This
alternative approach requires introducing two different types of
components for vectors, and analogously for tensors: contravariant
components denoted by superscripts, and covariant components denoted by
subscripts."
I am unhappy with Thorne's analysis because he has not considered the
case where the metric tensor could be the result of either a truly
non-euclidean space-time with both space and time being real OR a
euclidean space-time where the observer's coordinate system contains
imaginary time and the classical physical universe that is being
observed has real time. Such a dichotomy between the coordinate system
within the observer and that available to measuring instruments might
even be expected if Classical measurements are selected from a an
underlying QM reality. It would also allow the conscious observer to
be a point observer of its own brain (from 0 =3D r^2 + (ict)^2 where 0 is
truly no distance).
As you point out, imaginary time is a symmetrical, geometrical concept
whereas real time is just plain weird and appeals to people who have
reconciled themselves to the idea that physics has gone beyond
intuitive understanding. This is perhaps a result of the power of the
idea of mathematical symmetry in theoretical physics which allows us to
judge whether a physical principle occurs in a theory without having
any idea of the physical reality that is implied.
Best Wishes
Alex Green
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| User: "Franz Heymann" |
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| Title: Re: What really is "Light" (assuming SR is correct)?? |
11 Mar 2005 08:48:12 AM |
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"Alex" <dralexgreen@yahoo.co.uk> wrote in message
news:1110542794.114362.248160@z14g2000cwz.googlegroups.com...
Franz, Kip Thorne addresses this issue in his new book:
http://www.pma.caltech.edu/Courses/ph136/yr2004/0401.1.K.pdf
"One approach, often used in elementary textbooks [and also used in
Goldstein's (1980) Classical Mechanics and in the first edition of
Jackson's Classical Electrodynamics], is to set x0 = it, where i =
sqrt(-1)and correspondingly make the time basis
vector be imaginary, so that ~e ~e = (scalar product a.b= delta
ab). When this approach is adopted, the resulting
formalism does not care whether indices are placed up or down; one can
place them wherever one's stomach or liver dictate without asking
one's
brain. However, this x0 = it approach has severe disadvantages: (i) it
hides the true physical geometry of Minkowski spacetime, (ii) it
cannot
be extended in any reasonable manner to non-orthonormal bases in at
spacetime, and (iii) it cannot be extended in any reasonable manner to
the curvilinear coordinates that one must use in general relativity.
For this reason, most advanced texts [including the second and third
editions of Jackson (1999)] and all general relativity texts take an
alternative approach, which we also adopt in this book. This
alternative approach requires introducing two different types of
components for vectors, and analogously for tensors: contravariant
components denoted by superscripts, and covariant components denoted
by
subscripts."
I am unhappy with Thorne's analysis because he has not considered the
case where the metric tensor could be the result of either a truly
non-euclidean space-time with both space and time being real OR a
euclidean space-time where the observer's coordinate system contains
imaginary time and the classical physical universe that is being
observed has real time. Such a dichotomy between the coordinate system
within the observer and that available to measuring instruments might
even be expected if Classical measurements are selected from a an
underlying QM reality. It would also allow the conscious observer to
be a point observer of its own brain (from 0 = r^2 + (ict)^2 where 0
is
truly no distance).
As you point out, imaginary time is a symmetrical, geometrical concept
whereas real time is just plain weird and appeals to people who have
reconciled themselves to the idea that physics has gone beyond
intuitive understanding. This is perhaps a result of the power of the
idea of mathematical symmetry in theoretical physics which allows us
to
judge whether a physical principle occurs in a theory without having
any idea of the physical reality that is implied.
Hello Alex,
I understand the arguments you gave.
However, I am in the lucky position in which I am too old to bother to
extend the concepts of SR into GR, so for my simple applications, the
ict approach gives the right answers.
--
Franz
"A first-rate laboratory is one in which mediocre scientists can
produce outstanding work"
P.M.S. Blackett
.
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| User: "Tom Potter" |
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| Title: Re: What really is "Light" (assuming SR is correct)?? |
09 Mar 2005 10:57:02 PM |
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"Alex" <dralexgreen@yahoo.co.uk> wrote in message
news:1110371743.455127.60010@g14g2000cwa.googlegroups.com...
At school we learn Pythagoras' theorem:
h^2 = x^2 + y^2
This describes displacements on a plane.
In school maths we learn how to extend this to 3D:
r^2 = x^2 + y^2 + z^2
Modern Special Relativity (post 1908) is the proposal that the universe
is a four dimensional manifold with a metric (like Pythagoras' theorem)
given by:
s^2 = x^2 + y^2 + z^2 - (ct)^2
Where x, y, z are independent directions in space and ct is the
distance in METRES along the independent time axis (for simplicity a
displacement from the origin has been assumed and the space-time is
assumed to be flat).
The constant 'c' converts time to metres at the rate of approx.
300,000,000 metres for a second. If the universe is four dimensional
then all observers should obtain the same value for s^2 (things cannot
tilt out of the universe). 's' is known as the space-time interval. The
space-time interval is INVARIANT between observers.
If the 3D version of pythagoras' theorem is substituted into the four
dimensional equation:
s^2 = r^2 - (ct)^2
Where 'r' is simply the distance moved in time 't'. If an object is
moving at a velocity 'v' then:
s^2 = (vt)^2 - (ct)^2
and s^2 = t^2(v^2 - c^2)
c is a constant so a given value of s can be obtained by a wide range
of values of v and t. HOWEVER THERE IS ONE VALUE OF s THAT CAN ONLY
OCCUR FOR ONE VALUE OF v. When s=0 then v can only equal c. This means
that all observers will obtain the same value for v when v=c because
the space-time interval of zero is measured by all of them; remember,
the interval is INVARIANT between observers.
The velocity v = c is a universal constant.
If you explore relativity further you will discover that particles with
zero rest mass can move at c metres per second. Light seems to be
composed of such particles and it is for this reason, and historical
reasons, that c is known as the 'speed of light'.
Modern Relativity actually assumes that seconds are a measure of length
and 'c' is simply the conversion factor from seconds to metres (like
factors that convert from inches to centimetres etc.), it does not
assume that that the speed of light is constant. It predicts that the
speed of light is a universal constant.
This newsgroup has a number of contributors with various ideas about
the geometry of the universe, some believe that the universe is three
dimensional (ie: Presentists) some of whom claim time does not exist,
some are Galilean Relativists (who claim there is no geometrical
relationship between space and time), some are Ether Theorists (who
claim there is a preferred reference frame) and some propose other
metrics than the Minkowski metric. Most dissenters from modern physics
believe that the universe has a simple Pythagorean metric (ie: it is
wholly described by r^2 = x^2 + y^2 + z^2 and spatial length is
invariant).
Many of these are worthy points of view but they are not 'mainstream'.
The Minkowski metric is mainstream.
A very reasonable, well developed post Alex!
After I get through dealing with the GTR worshippers,
I'll try to respond to your rational, cogent post.
As it is rational and cogent and well developed,
naturally it will require thought on my part.
As can be seen from many of my posts to sci.physics,
I agree 100%
that <time intervals> are measures of <space>
and 'c' is simply the conversion factor from <time intervals> to <spaces>.
--
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