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100 Years of Special Relativity
phrotoma writes "Wikipedia notes in their Selected Anniversaries section that today marks
the 100th anniversary of Albert Eintein's publication of the third of his four Annus Mirabilis Papers entitled On the Electrodynamics of
Moving Bodies; the seminal work that introduced the concepts which would come to be known as Special Relativity. This
event is also being commemorated in a UN endorsed celebration of physics: World Physics
Year 2005 with talks and events at public schools, museums, and universities the world over."
Let the 'redundant' modding and subsequent bitching begin.
1/3 of jokes get modded OT. If you get the joke, mod 1 in 3 insightful/interesting/underrated to restore karma balance.
My theory is just as credible as yours since it's only a theory and not a fact.
Ok, now that that diatribe is over, what's truly interesting is not that what Einstein proposed 100 years ago is still being studied and restudied, it's that one portion of it was recently confirmed. Frame dragging was only confirmed last year.
Certainly other parts have been verified (relative time for example) but this portion, frame dragging, puts things in a whole new light. We're not just bodies in space. Instead, are bodies are changing the space around us!
We will bankrupt ourselves in the vain search for absolute security. -- Dwight D. Eisenhower
Good coverage. For those in the Toronto, Ontario, Canada area, there are events being held @ the UofT. http://www.fields.utoronto.ca/programs/scientific/ 04-05/string-theory/strings2005/
for more info
=)
.. the same laws of electrodynamics and optics will be valid for all frames of reference for which the equations of mechanics hold good. We will raise this conjecture (the purport of which will hereafter be called the "Principle of Relativity") to the status of a, postulate, and also introduce another postulate, which is only apparently irreconcilable with the former, namely, that light is always propagated in empty space with a definite velocity c which is independent of the state of motion of the emitting body. These two postulates suffice ..
The thing that needs explaining to me would be "frames of reference". A difference between two frames can be that they are in motion with respect to each other. For example, take a spaceship accelerating to half the speed of light, starting from our resting position. The 2nd postulate explains that the speed of light can be a constant velocity c, both with respect to the frame of the resting observer and the frame(view) of the spaceship. This leads to the question: if you shoot a light ray(velocity c=the speed of light) from the spaceship moving with half= 0.5 c, how come the light ray moves with 1.0 c from the view of both observers, not with 1.5 c from the resting observer?As Einstein states, he then proceeds to reconcile the two seemingly paradox postulates by formulating laws of electrodynamics that will work.
I'm still trying to figure out what people mean by 'social skills' here.
First of all you're only referring to special relativity here, which ignores acceleration and gravity. Secondly, there were still some leaps of faith to be made, such as assuming c is constant in all frames of reference, which Lorentz showed non-Newtonian transformations that would allow this for Maxwell's equations. And expanding the new energy definition and concluding the zeroth-order term (mc^2) is the rest energy of mass also took another leap of faith (although that paper wasn't published until a few months after this first relativistic one).
But even so, discovering the connection between relativity and E&M is still amazing, in my opinion. For examle, the permittivity (epsilon_0) and permeability (mu_0) of free space are two constants that can be measured in the laboratory rather easily. Yet Maxwell's equations in vacuum describe waves travelling at speeds 1/sqrt(epsilon_0*mu_0), which is exactly the speed of light in vacuum (although in Gaussian units this connection is far more obvious). It's pretty amazing to think how these are related. But you still need to make some assumptions to get the Lorentz transforms between reference frames.
Additionally, even simple special relativity was extremely controversial, it rejected many assumed notions of space/time. There were also many paradoxes that took awhile to get ironed out. Many scientists didn't believe in relativity until it was shown in experiment. And in fact the theories of relativity were so controversial that the Nobel committee didn't want to award Einstein the prize based on these, so went for the safer 'Photoelectric Effect' instead.
And thirdly, general relativity, although again not included in this 100 year anniversary, is total genius, and it took Einstein 10 years to come up with the theory. So don't wave off relativity as just a 'refinement of Maxwell's field equations' because it really is much more than that.
make world, not war
This says it better than I can.
"This indicates that according to the Lorentz transformation, nothing can have the same speed relative to both K and K' unless it is a ray of light"
You then calmly assert that this is nonsense and claim certain mathematical assumptions are to blame. However, even a moment's thought about this indicates that this makes perfect sense - The two frames are in relative motion to one another, and thus for any object the observed velocity would be V = Vframe+Vobject (or it's relativistic correction, for high velocities). So, unless both frames have the same Vframe (i.e they are the same frame), nothing but two rays of light can have the same velocity in both frames - as in the postulates of special relativity.
In effect, you have proved that Lorentz transformations are the ones which are consistent with SR.
I agree with the central message in your post. However, SR does include acceleration, jerk (the third derivative of position with time), and in principle all orders of positional change with time. You can also apply gravity as "just another force" in Newton's Second Law F=dp/dt, where F is the net force and dp/dt is the instantaneous rate of change of the momentum in time. Relativistically, p=gamma*m*v where gamma=1/sqrt(1-v^2/c^2). SR is an essentially complete package of kinematics and dynamics just like Newton's Laws. You can do (highly) accurate rocket science with it and certainly don't have to stop with velocity!
What SR does not develop fully is the "equivalence principle" which says, in brief, that gravitational acceleration and "kinematic" acceleration (e.g. sitting in an accelerating frame) are indistinguishable. When fully developed, this concept intimately links space-time to the gravitational force in a non-trivial way -- and is what makes GR fundamentally different than Newton's Laws and SR.
i\hbar\dot{\psi}=\hat{H}\psi
Regarding the photoelectric effect, Planck had already proposed the notion of discrete quanta of radiation a few years prior in order to get a consistent statistical-mechanical description of blackbody radiation that wasn't susceptible to the 'ultraviolet catastrophe'. Einstein extended this theory to explain the bizarre frequency-dependence of radiation to get above the work function of the metal. Was this a tippy-toes process or was it standing on the shoulders of giants? In both our opinions, in this case it was a stroke of genius. I also believe SR was a similar stoke of genius.
make world, not war
Theories of Relativity
Five specially commissioned short stories to mark the centenary of Einstein's discovery. Listen to them for next few days only here .
Share and Enjoy!
Artificial intelligence is the study of how to make real computers act like the ones in the movies.
There is no relavistic mass effect!!!
This is an oversimplification to the point of becoming myth - and the numbers don't even work out.
f = ma
The oversimplification is to suggest that if F produces less acceleration than expected, mass must be growing, but that's BS, because:
KE = (mv^2)/2
The relavistic correction for kinetic energy is the square of the correction for acceleration, *not* the same correction. Mass isn't changing at all, time is. Put Newton's law in the form Newton did, and this becomes ore clear:
f = d(mv)/dt
If your clock is moving slower (from an observer's point of view) then the same force produces less change in momentum, because that force is acting for less time.
No imaginary extra mass needed! Your *momentum* effectively increases, but that's *not* because your mass gets larger, it's because your time slows down, so it takes longer for a given force to affect you by to a given degree. All from a stationary observer's point of view, of course: from your point of view nothing has changed, and it's *their* clocks that have slowed!
Socialism: a lie told by totalitarians and believed by fools.
Special relativity only applies in inertial frames (i.e., no acceleration or gravity). General relativity was developed to handle non-inertial frames.
Don't get confused by the twin paradox and spaceships that have to accelerate. The twin paradox cheats on these issues as usually presented.
Professor of Astronomy, Author of Spider Star & Star Dragon (Tor)
Even in the example you cited, relativistic mass still has a place. Specifically, if we choose not to use relativistic mass, we can no longer simply express momentum as mv, because using the rest mass and speed measured from the rest frame, we would obtain incorrect results, since as you say the momentum has effectively increased.
While you're right to say that there is no 'extra mass', it is true to say that the energy of a body affects its inertia (See Einstein's 4th 1905 paper, I believe), which can be expressed as a modified mass term, if we so desire.
All five articles from Einstein (and many more important articles since 1799) have been published in the Annalen der Physik, the leading scientific journal at that time.
Thanks to the French digital national library Gallica, you can now access ALL (or nearly all) pages of the Annalen der Physik: on-line and from 1799 - 1930.
Obviously: to understand this publication, it helps a lot to read German, the former lingua franca of the science.
What are you talking about? Sci-Fi with integalactic travel almost never (never in my experience, but I'm sure there are some) has ships that go faster than light by just accelerating conventionally. They usually have some explanation for how they get around relativity (wormholes, shifting to diminsions with different rules etc).
It's rarely good science, but almost all Sci-Fi authors and fans do know about it.