I started a thread about the twin paradox and cross-posted it to three
newsgroups. I am grateful to those who discussed it, even though it got a
tiny bit personal at times
I was frustrated by the account of the twin paradox in the FAQ for
sci.physics ([Only registered users see links. ]), because it
resorts to saying that there is assymetry in the situation. One twin has
undergone an acceleration and it is that one which is younger.
That cannot be the case, because time dilation is supposed to explain why a
light beam, travelling from floor to ceiling of a moving spaceship will not
trace out its V-shaped path faster than c. Time must appear to be slowed
down or else the observer, looking through the window will see the beam
travel faster than c.
But if two people pass eachother on skateboards, watching eachother's
bouncing beams, they must both see time dilation in the other, or one of
them will see the beam going faster than c.
Claiming an assymetry based on the acceleration histories of the observer,
overlooks the fact that the time dilation must be real and identical in both
directions at all times or else someone will see the bouncing beam going
faster than c.
If only one skateboard rider is younger, what did this younger one see, the
other getting older? The beam going even faster than expected, much more
It baffles me, that intelligent people, capable of algebra, cannot see that
the assertion that time is slowed in a moving frame is a symmetrical
assertion, because frames move relative to eachother, symmetrically.
Besides which, the formula for time dilation is a function of the velocity
of the observed frame and makes no mention whatsoever of the acceleration of
either frame, before or while the calculation is made.
I was told again and again by several posters, "Do the math. Just plug the
numbers into the formulas and it all works out just fine." These were the
same people who want me to factor in acceleration, which is not mentioned in
the formula, because time dilation is purely a function of the relative
velocity, which is the same in both directions.
Plug the relative velocity of skateboarders A and B into the formula and
find out how much slower B's clock is, than A's. And how much slower A's is,
than B's. I don't need to "do the math" to see that this formula is telling
me two things which cannot both be true.
I suppose it depends on your definition of "working out fine".
Because I constructed my example with two moving twins, to force them to
face the symmetry, the defenders of relativity introduced a new twist:
acceleration causes time to speed up, cancelling out the age difference, in
both skateboarders. This is an new addition to relativity. Einstein never
said anything of the sort.
To say that acceleration makes time run faster, implies that if one of the
skateboarders is accelerating, the time contraction due to acceleration will
at least partially counteract the dilation caused by the velocity (predicted
by Einstein), allowing the other to see the bouncing beam move faster than
Still, though frustrated, I thoroughly enjoyed the thread I started and I am
grateful to all of the people who had the patience to contribute. In return,
I can only assure you that I will continue to post under the name "Stephen
Bint", so as not to undermine your killfile strategies.
And may I say in conclusion, that trying to bring the sweet light of reason
to the proponents of relativity, is like trying to bring salvation to the
"Dan Bloomquist" <[Only registered users see links. ]> wrote in message
news:[Only registered users see links. ]...
Since you suggested it, I did. It stands out as the best post on this
thread. Here's a quote:
And I am to blame for failing to bring the matter to a head. Because I
insisted in my example, to be told what the twins actually see, I have
demanded that Jon mask the time dilation with the doppler effect.
He has reiterated the explanation given in the FAQ, but done a better job of
it. The twins, by his reckoning, have aged less than an Earth-bound
observer. But the formula for time dilation is symmetrical, because the "v"
factor is identical for observers in both frames, looking at the other when
one frame is moving relative to the other. This cannot be reconciled with
the observers in one of the frames being younger .
The problem is not "deciding" which frame is the one running slow, by
clutching at an asymmetry. The problem is that time dilation fails to
prevent witnesses seeing the bouncing beam going faster than light, unless
it works both ways and the Earth-bound observer has also aged less than the
If you say either frame is the slow one, you deviate from what the formula
asserts, which is plainly that both are slow by the same factor.
When you say
you are appealing to me to be open-minded enough to be able to believe it is
possible that I am wrong. I would ask the same of you.
So, like the person who wrote the account of the twin paradox in the FAQ,
you do believe that time dilation affects the rate of aging.
The formula for time dilation is a function of velocity. If I am moving at a
given velocity with respect to you, then you are moving at the exact same
velocity with respect to me. To whatever extent there is time dilation and a
reduction of aging, it is predicted to be the same for you as for me,
because v is the same, and the formula is a function of v. You see me in
slow motion and I see you in slow motion, so both our ages are reduced by
the same amount.
Is that not the case?
"[Only registered users see links. ] (formerly)" <dlzc1.cox@net> wrote in message
"Stephen Bint" <[Only registered users see links. ]> wrote in message
news:3fa09253$0$104$[Only registered users see links. ].. .
Let me say yes, this way: If I travel between here and the store in my car
in different ways, do I show different mileage on my car for each trip?
Yes, the path you travel racks up different "mileage".
Not quite correct.
Not necessarily true. Since one frame does not see time or length the same
as the other, inferred velocities are bumfuzzled. For example a moving
triplet and a stationary triplet will not agree how fast the moving triplet
is moving. (I added a third twin, to merge with your gedanken. I hope
their mom doesn't mind.)
Not the same amount, no. The sign is correct ("slowed"), but the magnitude
Do you see the *sees*? The FoR 'is slow', is not the same as the
observation 'is slow'. From the earth, the observation is that both
clocks are running at the same rate! I think Jon made the distinction
between observations and *is* very clear.
It isn't about being 'open minded'. The math works. The observations are
consistent. Since 1905 there has been no hole found by minds very much
greater than ours. (I'm just a little mind. ) As you muddle through
all the 'paradoxes', (And I still do), learn the principles. When it is
all very clear in your head, then you can look beyond it for something
new. But without a contradictory observation to SR, that something new
will only be an extension of SR.
-- [Only registered users see links. ] [Only registered users see links. ]
The atoms in the one twin are moving faster and hence
due their moving fast, the function of aging,
is slowed. The normal interactions of the atoms
are slowed as opposed to the functions of atoms
in a normal state of rest.
The twin on earth, ages, the twin travelling
does not age at the same rate. Time is not
consistent between bodies at rest and bodies
in accelleration. Simply because atoms act
differently at rest, or under the influence
Time is nothing in and of itself. If it were
then you would say, poppycock. They are the same age.
One just didn't age as well as the other.