Speed of light

[The Code]

Is that not uniform? our sun is third/fourth generation, we know how long stars live. a star that gives that much energy in a few minutes at that distance? or is there something else going on? is it one that got past the net? does physics change after 12,700 million light years? but it is not just one gamma ray is it? there are thousands of them. would it be a reflection as most matter has a reflective surface? yes i did just say, a reflection from our own big bang.

i,m sure there was a bone round here somewhere.

xx mark

[Doum]

I edit the post i made earlyer. I hope its clearer. Sry for my english but finding the right word is hard.

Doum, where you are from?

Well it's a very long story, but i'll make it short.

At first there was nothingness except may be a singularity, but as soos as the univers get bigger (Like the sise of the planck lenght or bigger) everything start rushing out. It was like a big bang. Wow! Now im from planet earth. If that can be important in this forum.

[harry]

G'day from the land of ozzzz

Time has no matter or energy or any other form of particles or wave forms.

I did not say that GR is wrong or right, just stated that time cannot be changed.

If you can prove one way or another than, what can I say.

Expressing an opinion without science evidence is like asking for a chinese whisper.

Yes I'm open minded but not closed minded to science that can be backed up by evidence and not ad hoc ideas to make models work.

This maybe of interest to some

6. Distance - Time - Relativity
http://www.unitytheory.info/distance_ti ... ivity.html

and



Special relativity theory
Einstein published his Special Theory of Relativity in 1905. Some of the major points are:

Space-time - Space and time are fundamentally interrelated rather than two distinctly different quantities. Time is essentially a fourth dimension complementing the three spatial dimensions.
Simultaneous events - Whether or not two events are simultaneous depends on the observer. One observer might see two events as occurring simultaneously, another as one of the events occurring first, and a third as the other event occurring first.
Lorentz contraction - An object moving near the speed of light will appear shorter as seen by an outside observer at rest. The amount of contraction depends on its speed, and its length approaches zero as its speed approaches the speed of light. To an observer moving along with the object its length appears normal.
Time dilation - As seen by an outside observer at rest, time will move more slowly for an object moving close to the speed of light. At the speed of light, time will stop as seen by an outside observer. To an observer moving along with the object all appears normal
Mass increase - The mass of an object moving close to the speed of light will increase as seen by an outside observer. The mass will approach infinity as the speed approaches the speed of light. Again to an observer moving along with the object the mass remains the same.
Speed of light limit - As an objects speed approaches the speed of light its mass approaches infinity. Therefore it would take an infinite external force to accelerate any object with mass to the speed of light. Therefore light, and anything else with no mass, can travel at the speed of light. But an object with mass can not reach the speed of light. The best it can do is come arbitrarily close. Nothing can travel faster than the speed light travels in a vacuum. The speed of light in a vacuum is the ultimate speed limit in the universe.
E=mc2 - E represents energy, m represents mass, and c2 represents the speed of light squared. According to this famous equation mass and energy are interchangeable. Matter can change to energy and vice versa. The equations is sort of a conversion factor telling us how much matter corresponds to a certain amount of energy. For example, in nuclear reactions some of the mass is converted to energy according to this equation.
These relativistic effects seem strange to us because they only become significant at speeds of at least 10% the speed of light, which is 300,000 km/s. Because we have never traveled anywhere close to these speeds, we have never experienced these effects. However experiments in which subatomic particles are accelerated to these high speeds have so far confirmed all predictions Einstein's from special relativity theory. About a decade later, Einstein published his general theory of relativity.



Read more: "Einstein's Special Relativity: Time Dilation, Lorentz Contraction, and Other Relativity Effects" -
http://physics.suite101.com/article.cfm ... relativity

http://physics.suite101.com/article.cfm ... z0A4w4lSOZ


Space Time and Relativity
http://www.echeat.com/essay.php?t=127
and links to other papers.

If its important for you to think that your opinion is correct than its correct.

[aristarchusinexile]

Okay through a little Wiki searching I answer my own question .. the speed of light is the same to all observers but wavelength is longer or shorter.

Speed of light .. this will reveal my total lack of physics education but I've revealed that before. If a space ship is travelling at half the speed of light and shoots a beam of light directly ahead of it as well as directly behind it will the beams be measured at different speeds by stationary people directly ahead of and directly behind the ship? Okay, I seem to have found a possible answer on another thread, "Einstein’s theory of special relativity is based on two postulates: - The speed of light is constant for all observers." Can anyone explain how this postulate can be so? Not to discourage anyone from answering, but I must make the observation from Wiki: "In traditional logic, an axiom or postulate is a proposition that is not proved or demonstrated but considered to be either self-evident, or subject to necessary decision. Therefore, its truth is taken for granted, and serves as a starting point for deducing and inferring other (theory dependent) truths." I fail to see how scientists can afford the luxury of taking anything for granted, and fail to see where the human race has the capability to prove the speed of light is constant, considering the vast distances light travels. I do understand according to my reading that it was Einstein who made the decision that speed of light was constant (in a vacuum).

[aristarchusinexile]

This will be old news to the physicists here, but I'm interested in what you know of the followup on this story.
http://www.telegraph.co.uk/scienceandte ... light.html
"Dr Gunter Nimtz and Dr Alfons Stahlhofen, of the University of Koblenz, say they may have breached a key tenet of that theory.The pair say they have conducted an experiment in which microwave photons - energetic packets of light - travelled "instantaneously" between a pair of prisms that had been moved up to 3ft apart. Being able to travel faster than the speed of light would lead to a wide variety of bizarre consequences. For instance, an astronaut moving faster than it would theoretically arrive at a destination before leaving. The scientists were investigating a phenomenon called quantum tunnelling, which allows sub-atomic particles to break apparently unbreakable laws. Dr Nimtz told New Scientist magazine: "For the time being, this is the only violation of special relativity that I know of."

[aristarchusinexile]

Taking into consideration this Wiki definition of light, "In the broader field of physics, light is sometimes used to refer to electromagnetic radiation of all wavelengths, whether visible or not." 'If light has no wavelength, is it still light?'

Can anyone answer, 'if light has no wavelength, is it still light'.

[makc]

Okay, I seem to have found a possible answer on another thread, "Einstein’s theory of special relativity is based on two postulates: - The speed of light is constant for all observers." Can anyone explain how this postulate can be so? Not to discourage anyone from answering, but I must make the observation from Wiki: "In traditional logic, an axiom or postulate is a proposition that is not proved or demonstrated but considered to be either self-evident, or subject to necessary decision. Therefore, its truth is taken for granted, and serves as a starting point for deducing and inferring other (theory dependent) truths." I fail to see how scientists can afford the luxury of taking anything for granted, and fail to see where the human race has the capability to prove the speed of light is constant, considering the vast distances light travels. I do understand according to my reading that it was Einstein who made the decision that speed of light was constant (in a vacuum).

Not quite, Einstein axiom is generalization of experiment results. But, in the end, yes, it is axiom, and is only valid as far as theory predictions match observations.

[aristarchusinexile]

"... Because you still haven't explained what force would cause galaxies to enter voids in the first place. Without such a force, there's no need for a new force ("antigravity") to keep them out.

You answer that question yourself, Chris, when you say Gravity has no limits .. that matter kazillions of googloplexes of light years apart from other matter will still feel each other, and so will be attracted towards each other. What can keep them apart other than anti-gravity? (or stronger attraction in an opposite direction).

[aristarchusinexile]

from Wiki: "A chronon is a proposed quantum of time, that is, a discrete and indivisible "unit" of time as part of a theory that proposes that time is not continuous."

My minutes-old awareness of chronons leads me back to 'Galaxies trailing their spirals', where I propose Galaxies create time, making it appear in photos of spiral galaxies face on that their spirals are trailing behind the nucleus, whereas no edge on photos of spirals galacies exhibit the appearance. You might remember my proposed 'time funnels'.

[JimJast]

I fail to see how scientists can afford the luxury of taking anything for granted, and fail to see where the human race has the capability to prove the speed of light is constant, considering the vast distances light travels. I do understand according to my reading that it was Einstein who made the decision that speed of light was constant.

Scientists don't take anything for granted. They carefully check everything that they can check. Einstein didn't make this decision. He just guessed that speed of light is constant in any frame of reference since it was a sensible solution that could explain the crazy results of experiments.

Then it has been confirmed with experiments that the speed of light is really constant in any frame which surprised folks a lot. But one can't argue with facts. So this constant speed of light is an observational fact guessed by Einstein. And it was not easy to guess, as you have noticed yourself.

Then, the explanation has been thought out: It turns out that the whole thing hangs on two facts: that the time is not absolute: clocks don't tick at the same speed in every moving spaceship. They tick slower when the spaceship moves faster (the time runs slower). Also space is not absolute: lengths along the dirction of velocity get shorter in moving spaceships, by the the same relative amount as clock tick slower (everything gets flatter). Those two effects take part in measurment of speed of light and that's why it always comes out the same since from outside the spaceship the distances that the beam travels e.g. forward takes less time but also the distance the light travels is shoter and so the ratio of both (the speed of light) is always the same. This is what Einstein figured out, it just turned out to be true as it has been checked millions times by now.

And that's why it is impossible to measure the absolute velocity. So we have to say that there is no such thing as absolute velocity. In other words if there is, it doesn't matter what it is since it can't influence anything. There is no way of noticing it, so we may say that for us it doesn't exist, and then it really doesn't matter if it exist once we know how it works and may predict what happens: namely that regadless of our velocity we won't see any difference in our ecperiments (luckily) since then we may predict them regarless of our velocity. We may be sure that speed of light, and the results of other experiments, will come out always the same. That's the famous principle of relativity: we'll see the same physics around us, regardless of our state of motion.

[bystander]

A little learning is a dangerous thing; drink deep, or taste not the Pierian spring: there shallow draughts intoxicate the brain, and drinking largely sobers us again.

Two things are infinite: the universe and human stupidity; and I'm not sure about the former.

You always admire what you really don't understand.

The greatest obstacle to discovery is not ignorance -- it is the illusion of knowledge.

So long as the mother, Ignorance, lives, it is not safe for Science, the offspring, to divulge the hidden causes of things.

Wonder is the foundation of all philosophy, research is the means of all learning, and ignorance is the end.

You can swim all day in the Sea of Knowledge and still come out completely dry. Most people do.

If the blind lead the blind, both shall fall into the ditch.

All opinions are not equal. Some are a very great deal more robust, sophisticated and well supported in logic and argument than others.

[Chris Peterson]

Okay, I seem to have found a possible answer on another thread, "Einstein’s theory of special relativity is based on two postulates: - The speed of light is constant for all observers." Can anyone explain how this postulate can be so?

It's not a postulate. It started out as an axiom for the development of SR. It has since been verified experimentally under many conditions that the speed of light is constant. It is possible to actually test in the lab that light doesn't travel faster from a moving emitter than from a stationary one, and to verify that two observers travelling at different speeds see the same value for the speed of light from a single source.

The ability to verify the constancy of c by experiment is an important part of the evidence supporting SR and GR.

[Chris Peterson]

"... Because you still haven't explained what force would cause galaxies to enter voids in the first place. Without such a force, there's no need for a new force ("antigravity") to keep them out.

You answer that question yourself, Chris, when you say Gravity has no limits .. that matter kazillions of googloplexes of light years apart from other matter will still feel each other, and so will be attracted towards each other. What can keep them apart other than anti-gravity? (or stronger attraction in an opposite direction).

I didn't say that gravity has no limits. It has the same limits that everything else has: causality is limited by the finite speed of light. An object can't be affected gravitationally by another if there hasn't been enough time for the gravitational effects to reach it.

As far as voids are concerned, distant (but still causal) material would have nearly identical influence over all the shell material- distinctly non-tidal. So it wouldn't significantly alter the shape of the structure. You only need ordinary gravity to explain the shell-like structure of the large scale Universe. Any other shape is what would require a different explanation.

[aristarchusinexile]

A little learning is a dangerous thing; drink deep, or taste not the Pierian spring: there shallow draughts intoxicate the brain, and drinking largely sobers us again.

"One sip at a time lad, lest ye drown y'rself in that green beer" - L.E. Prechaun

Two things are infinite: the universe and human stupidity; and I'm not sure about the former.

"Well I am damned sure about human stuipity!" Cas Ualobserver

You always admire what you really don't understand.

"Beautiful young ladies especially." A. Noldguy

The greatest obstacle to discovery is not ignorance -- it is the illusion of knowledge.

"I drank from the dry oasis, and 'twere not sweet." Wi Neo

So long as the mother, Ignorance, lives, it is not safe for Science, the offspring, to divulge the hidden causes of things.

"Perhaps, but keep the mother alive, and perhaps the second birth will bear better fruit than that worthless son of mine!" Aty Picaldad

Wonder is the foundation of all philosophy, research is the means of all learning, and ignorance is the end.

"Mike y'r off y'r blinkin' rocker lad!" Kind Dergartengraduate

You can swim all day in the Sea of Knowledge and still come out completely dry. Most people do.

"How'd we get back to this damned mirage?" Wi Neo

If the blind lead the blind, both shall fall into the ditch.

"I'd have to be a complete atheist to argue that one, Bystander." Sputnick

All opinions are not equal. Some are a very great deal more robust, sophisticated and well supported in logic and argument than others.

"Aye, and just as wrong as a wild guess!" G. Ambler

[aristarchusinexile]

Okay, I seem to have found a possible answer on another thread, "Einstein’s theory of special relativity is based on two postulates: - The speed of light is constant for all observers." Can anyone explain how this postulate can be so?

It's not a postulate. It started out as an axiom for the development of SR. It has since been verified experimentally under many conditions that the speed of light is constant. It is possible to actually test in the lab that light doesn't travel faster from a moving emitter than from a stationary one, and to verify that two observers travelling at different speeds see the same value for the speed of light from a single source.

The ability to verify the constancy of c by experiment is an important part of the evidence supporting SR and GR.

I can easily picture the two beams of light (one emitted from a moving instrument, the other from a staionary instrument) travelling at the same speed, but the question was, "can anyone explain how this ( ) can be so?

[aristarchusinexile]

"... Because you still haven't explained what force would cause galaxies to enter voids in the first place. Without such a force, there's no need for a new force ("antigravity") to keep them out.

You answer that question yourself, Chris, when you say Gravity has no limits .. that matter kazillions of googloplexes of light years apart from other matter will still feel each other, and so will be attracted towards each other. What can keep them apart other than anti-gravity? (or stronger attraction in an opposite direction).

I didn't say that gravity has no limits.

I can't verify that you did say it, so I won't argue the fact that you did; and now that you have clarified your opinion it's okay .. I won't get upset that you're saying you didn't when you did .. not that I would get upset .. but I won't even if I could have .. which I can't. Besides, I could be mistaken, perhaps I only thought you did, in which case I won't get upset with myself either.

It has the same limits that everything else has: causality is limited by the finite speed of light.

Do you have a comment on the two Germans who claim to have broken the speed of light?

An object can't be affected gravitationally by another if there hasn't been enough time for the gravitational effects to reach it.

As far as voids are concerned, distant (but still causal) material would have nearly identical influence over all the shell material- distinctly non-tidal. So it wouldn't significantly alter the shape of the structure. You only need ordinary gravity to explain the shell-like structure of the large scale Universe.

I thought the universe was flat? Or is is that space is flat, and the universe is a shell. And if so, how can those differences exist unless space exists in a dimension separate from the universe?

Any other shape is what would require a different explanation.

So it remains to be measured why some galaxies and groups of galaxies are drawing closer to each other and why some are separating. I just can't get over the thought that if simple gravity were at work, the universe would be very homogenous, no voids, no dense lumps. I have read that I am not alone in that question, and many possible answers are put forth, none of those answers being necessary until the discovery of the huge voids which did not fit the models, which led me to think of anti-gravity creating the voids.

[bystander]

Thanks for making my point, I expected no less.

[aristarchusinexile]

Thanks for making my point, I expected no less.

My pleasure, bystander, if you aren't making fun of me that is.

[bystander]

My pleasure, bystander, if you aren't making fun of me that is.

not me, no need

[aristarchusinexile]

Okay .. I'll post a reply to that.

http://www.zulenet.com/see/nyt.html

by James Glanz

"The speed at which light travels through a vacuum, about 186,000 miles per second, is enshrined in physics lore as a universal speed limit. Nothing can travel faster than that speed, according to freshman textbooks and conversation at sophisticated wine bars; Einstein's theory of relativity would crumble, theoretical physics would fall into disarray, if anything could.

Two new experiments have demonstrated how wrong that comfortable wisdom is (although physicists say Einstein's theory survives).

In the most striking of the new experiments a pulse of light that enters a transparent chamber filled with specially prepared cesium gas is pushed to speeds of 300 times the normal speed of light. That is so fast that, under these peculiar circumstances, the main part of the pulse exits the far side of the chamber even before it enters at the near side."

[aristarchusinexile]

My pleasure, bystander, if you aren't making fun of me that is.

not me, no need

The lady with the spare chronons thinks you're cute .. so you're not welcome to come to the bridge with us.

[aristarchusinexile]

G'day from the land of ozzzz

If its important for you to think that your opinion is correct than its correct.

Harry, where you tired when you wrote that?

[aristarchusinexile]

I edit the post i made earlyer. I hope its clearer. Sry for my english but finding the right word is hard.

Doum, where you are from?

Well it's a very long story, but i'll make it short.

At first there was nothingness except may be a singularity, but as soos as the univers get bigger (Like the sise of the planck lenght or bigger) everything start rushing out. It was like a big bang. Wow! Now im from planet earth. If that can be important in this forum.

Yeah .. most things in physics are maybes. You're from planet earth? What a coincidence. So am I. I'm not sure about many of the Apodians though. But wherever they're from, they seem to be nice people, if they're people, which they might not be if they're not from Earth, so I guess I should say they seem to be nice beings, whom I set up as role models regardless of what they might look like.

[Chris Peterson]

I can easily picture the two beams of light (one emitted from a moving instrument, the other from a staionary instrument) travelling at the same speed, but the question was, "can anyone explain how this ( ) can be so?

We clearly see the Universe from different perspectives, so I don't really understand what such an explanation would look like to you. For me, the observation that c is constant is explained completely by SR and (more broadly) by GR.

[Chris Peterson]

I didn't say that gravity has no limits.

I can't verify that you did say it, so I won't argue the fact that you did...

I expect it is some confusion over an earlier discussion on the limits of gravity's influence. The gravitational field never goes to zero, but there are places where fields from one mass haven't had time to reach another. This is analogous to EM: the light intensity from a continuous source never reaches zero, no matter how far away you get... assuming the two locations are causally connected. Beyond that, there is no signal (which is different than the signal reaching a level of zero).

Do you have a comment on the two Germans who claim to have broken the speed of light?

I'm not aware of any such claims. People have modified the phase velocity of light to be both faster and slower than c, but that doesn't break any rules because no energy or information is traveling faster than light.

I thought the universe was flat? Or is is that space is flat, and the universe is a shell. And if so, how can those differences exist unless space exists in a dimension separate from the universe?

Space probably is flat, although that's not certain. But I don't understand your question.

So it remains to be measured why some galaxies and groups of galaxies are drawing closer to each other and why some are separating. I just can't get over the thought that if simple gravity were at work, the universe would be very homogenous, no voids, no dense lumps.

No, that's not the case. It all depends on initial inhomogeneities, and on initial motion. Gravity doesn't automatically make things homogeneous. Two objects that are moving apart at their escape velocity or greater will move apart forever, despite the fact that gravity is providing a never ending attractive force between them. Most things in the Universe are moving apart from each other for the same reason- they exceed each other's escape velocity. Gravity is a very weak force, and only weakly binds distant masses. So clumping happens mainly on a small scale (like galaxies). The interesting thing about large scale clumping around voids isn't the clumping itself, which is totally understood in terms of ordinary gravitational theory, but what mechanism in the very early Universe provided the rather specific sort of inhomogeneity required to end up with the structure seen today.

I have read that I am not alone in that question, and many possible answers are put forth, none of those answers being necessary until the discovery of the huge voids which did not fit the models, which led me to think of anti-gravity creating the voids.

As noted, the questions are not with respect to the forces that maintain the voids, but to the early structure of the Universe. Naturally, there was no need to answer any such questions (or indeed, to even ask any) until those observations were possible. The existence of voids and large scale shell structure now provide one of the stronger pieces of evidence for dark matter- something that was discovered in an entirely different way- since dark matter's influence very early in the Universe appears to just the sort of structure we now see (and find difficult to explain in any other way).