Relativity, both general and special, are theories and describe the universe as we understand it at the moment. But increased knowledge will place boundaries on Einstin's theories just as Einstein framed Newton, and showed the limits of his theories. That is the way of science. Newton was not wrong, but his theories and laws have limits, so to will relativity.
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Letty
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Sat 18 Sep, 2004 02:23 pm
Thank you, au. I had forgotten that I turned off the updates on this thread. I am searching for predictions that fell flat, one of which was an Einstein thing.
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Brandon9000
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Sat 18 Sep, 2004 05:36 pm
Re: thanks
kctech wrote:
Brandon9000
You are correct I mispoke. My apologies. I am less than a layman on this subject to be sure. It has been a long time since I read the theory. I may not remember the details but I recall something of the appearance of time differences. Now that you have correctly pointed out my not describing the theory properly - and I am guilty of that - would you mind addressing the apparent time shift? I would really appreciate the opinion of someone that unlike me actually understands the theory. Is the apparent time shift real or an illusion as I believe? I admit I know nothing of this so I would like someone to explain it. I will not be surprised to be shown to be wrong in my thinking just as I was shown wrong in my description of the theory itself. Thanks.
Observers moving at different speeds measure the passage of time differently, and it is absolutely real, not illusion. An illustration of both time dilation and the length contraction occurs in the decay of mu mesons created high in the atmosphere by fast cosmic rays. The mesons travel at nearly the speed of light, and only for this reason last long enough to reach the ground. Relative to these mesons, the distance through which they travel gets shortened while their life spans get increased. Hence, despite their brief life-spans, it is possible for them to reach the ground from the considerable altitudes at which they are formed.
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Letty
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Sat 18 Sep, 2004 05:46 pm
Oops, make that Acquiunk.
I am amazed this thread which started as a "double-dog-dare" has gone as far as it had.
Brandon, although I don't understand what you say, I will defend your right to say it, or something like that.
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Acquiunk
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Sat 18 Sep, 2004 06:06 pm
Major theories rarely fall flat, they just offer answers that are not completely satisfying or have nothing to say on the phenomena at all. In Einstein's case his theories of Relativity work better in the macro universe of stars and galaxy's than they do in the micro world of subatomic particles, where the theory of Quantum Mechanics works best. Combining those two is the next big step. It will not replace Relativity but extend it as Einstein did Newton.
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Brandon9000
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Sat 18 Sep, 2004 09:28 pm
Letty wrote:
Oops, make that Acquiunk.
I am amazed this thread which started as a "double-dog-dare" has gone as far as it had.
Brandon, although I don't understand what you say, I will defend your right to say it, or something like that.
People moving with respect to each other, disagree about the measurement of elapsed time. This effect is known as time dilation. Some unstable particles formed in the upper atmosphere ought not to live long enough to reach the surface of the Earth, yet they do, because of the fact that time is passing more slowly for them.
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Vengoropatubus
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Mon 20 Sep, 2004 12:25 pm
Isn't there something in relativity suggesting that time stops at the speed of light? If so, why would light take any amount of time to reach the earth?
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Steve 41oo
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Mon 20 Sep, 2004 12:41 pm
Was he right?
Relatively speaking, yes.
Welcome to a2k vengoropatubus. That is the first time and last, I will use your full name. Glad to have you aboard, vennyboy.
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blueSky
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Mon 20 Sep, 2004 12:48 pm
constant c
Relativity postulates that speed of light c is constant. There are many recent works contradicting that postulate.
No, Einstein said that if any observer in a non-accelerated reference frame sees some particular object travelling at the speed light travels in vacuum, all observse in all non-accelerated frames will measure the same speed for it. This has nothing whatever to do with light, just the speed at which light and massless particles travel.
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blueSky
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Mon 20 Sep, 2004 02:03 pm
One of the postulates
Quote:
if any observer in a non-accelerated reference frame sees some particular object travelling at the speed light travels in vacuum, all observse in all non-accelerated frames will measure the same speed for it
That is correct, the principle of equivalence, it is one of the postulates of general relativity.
if any observer in a non-accelerated reference frame sees some particular object travelling at the speed light travels in vacuum, all observse in all non-accelerated frames will measure the same speed for it
That is correct, the principle of equivalence, it is one of the postulates of general relativity.
Looks to me like your postulate #3 in the first link is merely stating that observers in inertial frames agree about the speed of objects propagating at the speed of light.
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blueSky
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Mon 20 Sep, 2004 02:50 pm
Quote:
3. The Speed of Light is Constant
Statement: "The speed of light c is a universal constant, the same in any inertial frame".
says c is UNIVERSAL constant. Doesn't mention any agreement of observers on that.
A lot of conclusions and relativity calculations hinges on that.
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Brandon9000
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Mon 20 Sep, 2004 03:00 pm
blueSky wrote:
Quote:
3. The Speed of Light is Constant
Statement: "The speed of light c is a universal constant, the same in any inertial frame".
says c is UNIVERSAL constant. Doesn't mention any agreement of observers on that.
A lot of conclusions and relativity calculations hinges on that.
"the same in any inertial frame"
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blueSky
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Mon 20 Sep, 2004 03:29 pm
Quote:
New experiments show that some things can travel faster than the speed of light.
But the Universe always manages to ensure that we can never use the effect for anything useful, like building a faster-than-light starship or travelling back in time.
It is a fundamental law of physics, a fact that is built into the architecture of the Universe and taught to every student, that nothing can travel faster than light which is roughly 300,000 km a second (186,000 miles).
Well not exactly. The Universe does have this speed limit but recent experiments would seem to suggest that in certain circumstances something can travel a bit quicker.
According to Einstein's special theory of relativity, a faster-than-light signal would violate the "causality principle," which states that "causes" always precede "effects."
The recent experiments are not especially new. Physicists have been making light pulses that travel faster than c (the speed of light in a vacuum) for years. They key point however, is that none of the experiments could be used to send information faster than c.
No, actually, we welcome them. Typically they turn out not to contradict the theory, e.g. nothing is actually propagating faster than c. Speaking only of Special Relativity, in the hundred years since the theory was published, no one has come up with an objection that adds up to anything. Not only that, but its predictions have been verified over and over again experimentally. All you've done is post a link to an article which you decline to analyze or discuss the specifics of in any way. If you like, I'll post five links to articles that say that Relativity is correct.
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blueSky
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Tue 21 Sep, 2004 08:52 am
Yes, it is a good theory. Does it mean it is there are no contradictions? Newton's theories were good enough for 300 years, and had plenty of holes in them. And it is not even 100 years for special relativity, not yet.
Are you a professional physicist? This forum is too limited to discuss specifics, calculations and conclusions. Considering competitiveness of science these days, if I were a physicist, I wouldn't discuss them here or expect others to do it. I am merely referring to possibilities suggested/expressed by works of some scientists. I understand your position that you don't agree with them.
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jacko
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Tue 21 Sep, 2004 05:40 pm
I dont know alot about the topic but reading these threads, the theory states that nothing can travel at the speed of light! Why then can light, having mass, travel at these speeds. ??
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blueSky
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Tue 21 Sep, 2004 06:29 pm
It is a postulate. A lot of past experimental evidence supports its validity. But some recent observations are beginning to suggest otherwise, which are being scrutinized.
