Speed of Light

Well, light travels at the same speed everywhere, so it doesn't really need a reference point other than its point of origin; even in a totally empty void, the light must have come from someplace. So it's not really an empty void. Now, if you want to start changing the laws of physics then most anything can be possible. Without a frame of reference though, no measurement is possible.

Your are correct, speed, like position, needs to be referenced to something else.

But, believe it or not, the velocity of light will always be measured as c, regardless of your motion with respect to the light's source.

We assume, without question, that speeds add and subtract. If you walk at 1 mph through a train car that is traveling at 60 mph with respect to the earth, then your speed with respect to the earth is 61 mph. This is only approximately true, although a very good approximation at slow speeds.

Two things happen between two reference frames in motion:

1. The length of the other reference frame appears shorter.

2. Time passes more slowly in the other reference frame.

These two effects conspire to make it so that velocities don't strictly add and the velocity of light will always be measured as the same value.

Here is a good example: Muons are created in the upper atmosphere when cosmic rays hit a nucleus in a molecule of gas. A muon in captivity only lives about 2.2 microseconds, far short of the time for the muons to reach the ground. Yet, they do.

What is happening is that the muons are traveling close to the speed of light, so the muon's time passes more slowly and they can thus reach the ground. From the muon's point of view, their lifetime is still about 2.2 microseconds but the earth is traveling close to the speed of light. The thickness of the atmosphere is foreshortened to the small distance that they can travel before they decay.

"When a cosmic ray proton impacts atomic nuclei in the upper atmosphere, pions are created. These decay within a relatively short distance (meters) into muons (their preferred decay product), and muon neutrinos. The muons from these high energy cosmic rays generally continue in about the same direction as the original proton, at a velocity near the speed of light. Although their lifetime without relativistic effects would allow a half-survival distance of only about 456 m (2.197 µs×ln(2) × 0.9997×c) at most (as seen from Earth) the time dilationeffect of special relativity (from the viewpoint of the Earth) allows cosmic ray secondary muons to survive the flight to the Earth's surface, since in the Earth frame the muons have a longer half life due to their velocity. From the viewpoint (inertial frame) of the muon, on the other hand, it is the length contraction effect of special relativity which allows this penetration, since in the muon frame its lifetime is unaffected, but the length contraction causes distances through the atmosphere and Earth to be far shorter than these distances in the Earth rest-frame. Both effects are equally valid ways of explaining the fast muon's unusual survival over distances."

https://en.wikipedia.org/wiki/Muon

Recommended reading: "Why does E-mc², and why should we care" by Drs. Brian Cox and Geoff Forshaw.

Send ralfcis a PM about this, and he can tell you more than you would ever want to know.

No comprende satire?

The speed is referenced to 4-dimensional spacetime. That's it.

Bistromathics itself is simply a revolutionary new way of understanding the behavior of numbers. Just as Einstein observed that space was not an absolute but depended on the observer's movement in time, and that time was not an absolute, but depended on the observer's movement in space, so it is now realized that numbers are not absolute, but depend on the observer's movement in restaurants.

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So, everything is in the mind of everybody? Nothing exists but the human life.

Speed of light is constant no matter what speed your travelíng... the light wave may be contracted or shorter wave lengths (blue shift) or expanding, longer wave lengths or red shift creating the dopler effect.

here's an interesting thing I found about 2 months ago, it the fastest camera with over a trillion frames a second, it can actually see a photon traveling. in other word, actually seeing the speed of light moving... and this as when light is as a particle, not as a wave.

Yes the speed of light in Oak is zero....
But I think we all knew that
Del
But what about the speed of heavy ?

I was referring to gas clouds in space, not in England.

The speed of chubby is slightly slower the a fast wálk...

I saw an experiment about 5-6 years ago?... on a video that they passed a pulsed light through a cloud and was able to slow it down, where you could see as the light pass through the cloud. I don’t beleive it was real time, but captured on high speed film.

the post basically showed how far cameras have come.

I hear this no longer hold True.

If a tree falls in the woods and there is no one there to hear it.........?

For the sake of hypothetical discussion, suppose you are traveling at 299,700 km/sec with a full spectrum head light shinning in the direction of your travel and a similar tail light shinning back to your point origin. As you observe both light beams they would be moving at the speed of light right? But what would a stationary observer in the direction of your destination, or in the direction of your origin, see as they observed you? I think it would be far beyond a red or blue shift. Beyond a shift to gamma rays and micro waves even. Not only is the wave length far beyond that of visible light relative to them, the velocity is too. So would they even observe light at all? And if so, what would they measure the speed of it to be? Would anyone observe mass? And who would detect what energy? Would anyone see some particle other than a photon? Could we on Earth be subject to some form of altered light continuously, and maybe be observing it even if we don't know it?

Also consider the behavior of light at the event horizon of a black hole. If light can't escape gravity beyond that point, it would seem it could only be because it is accelerating light inward due to massive gravitational pull. Although it clearly accelerates light's relative velocity, it accelerates it none the less and C is no longer constant at that point. Has the physical properties of light been changed when this happens?

Point being, C truly is relative but there are bounds to its relativity beyond which we don't yet understand.

As i understand it, If the observer is traveling at the same speed as the subject, looking at the subject, nothing unual because It would be relative,... but the suroundings would have a blue shift, same as the subject.

QUESTIONS and ANSWERS

• If one were traveling in a totally empty void, at a constant speed, how could you tell you were even moving at all?

EVIDENCE: When travelling at “C” speed you will see 2 passing places as reference (distance) which was done in a time frame. So, speed = distance/time.

• If there were no reference points: other objects to compare to, how would the speed be determined?

EVIDENCE: Speed will maximum when you and the light travel in opposite directions (at 180 deg)

• To measure speed, you must have a reference point; or do I have this all wrong?

You are not wrong at all. This answer is equal as to previous one.

"... If there were no reference points: other objects to compare to, how would the speed be determined?
EVIDENCE: Speed will maximum when you and the light travel in opposite directions (at 180 deg)..."

..

..so the fastest I ever go is at night when I back out of the driveway with my headlights on?

Please refer that he is assuming traveling at light speed.

I don't see any stated assumption that he was traveling at light speed.

Regardless, what do you mean by traveling fastest when 180 degrees from the light?

It means travelling in opposite direction of the light.

For any real observer a beam of light will speed away from us at the same light speed, whatever our velocity might be relative to anyone else.

You aren't going to get light traveling away from you faster than the speed of light, even backing out of the driveway really fast with your headlights on.

You'd have no way to know how fast you'd be going ... and time wouldn't exist. This assumes that the 'totally empty void' has no light in it.

If it's a totally empty void, you're not in it.

Perhaps I misunderstood it,but did not Einstein state that communication faster than the speed of light was not possible,due to the speed limit of light?

Things could be moving faster,but we would not be able to observe them due to the constraints of C,which I consider to be one of the boundaries of our dimension.

Consider entangled particles,able to affect each other instantly regardless of distance.We do not know how this happens,but apparently faster than C.

Might there be dimensions where C is the minimum speed?

When you get this all sorted, maybe you can help me with the age of the Universe. 13.7 billion years, right? But only as measured from our speeding perspective. And what about those stars and galaxies estimated to be 90+ billion light years away???

"Consider entangled particles,able to affect each other instantly regardless of distance.We do not know how this happens,but apparently faster than C."

The people I have encountered on the Physics Forums say that the entangled particles are already set before you look at one of them (that they don't change each other). It is a bewildering place to visit sometimes. You can't discuss your own "theories", but you can discuss others if they are published in a University website. And that is only if you don't speculate too much.

As you approach the speed of light, your mass increases... from his equation E=mc²

Only to someone who measures you approaching the speed of light from their perspective. You can't perceive your motion and you would measure your own mass (and length) the same as always.

My favorite thought experiment. Parlor games were one of Einstein's favorite pastimes, no internet or such. He proposed questions to get answers, and to promote wider thinking.

Our current reference to speed is the Earth, which is moving relative to the rest of space. If we happen to be moving at half the speed of light, and another planet is moving at more than half the speed of light directly away from us, relatively, the speed of light between us is exceeded, no? Relativity was also one of Einstein's favorite words.

While here, another thought experiment of mine involves the wave/particle issue. Consider a particle orbiting a line, moving down that line. Viewed from the side, it would be seen as a wave. A photon could easily be that particle, set in motion by energy on it's way at light speed. It would have gyroscopic properties due to the orbit, and it would pass other tests for light properties, like the double-slit experiment.

"... the speed of light between us is exceeded, no?..."

.

No.

MORE SPECULTION: In a previous post I have made reference to relative size. So to recap, If the mass of a observer and an object are equally reduced, then there relative size remains the same, but, the distance between them relatively increases. So if the speed of light is constant, then, as mass and distance varies, then so must the time for the relative distance travelled by light to remains constant.

So the greater the speed of an object, the greater it’s mass. And as that object approaches the speed of light, our observed speed of light in front and behind, remains the same? So to speculate, how is this possible?

So too speculate a solution, imagine mass to be a sphere of energy, with a pulsating centre. With the radius of the mass, being its size, and its pulses its atomic signature, so as motion takes place imagine it’s centre is displace, with the leading edge radius increasing, resulting in the pulses being reduced by the increased radial distance, which in turn results in time being slowed down. Thus the reduction in time when referencing the speed of light confirms it’s a constant. But the lagging mass radius reduces, results in the impulses increasing, which in turn results in time increasing, thus the increase in time when referencing the speed of light confirms it’s a constant.

Just something too think about,

The perception of the speed of light may be different for every individual, as the amount of time it takes for the signal to be observed by the brain can differ. I'm not sure this is a factor, but I thought I would throw it in for what it is worth. Let me know if I am indeed full of s##t.

"... is time a constant. ..."

.

To roughly the same degree (though probably inverse) that length or distance is a constant.

Thanks to whoever gave me the OT, it draws more attention to the post. The original question involves distance and time, something usually termed 'speed'.

If you have trouble comprehending my point, unmask yourself and I will happily elaborate. Feeding tolls is, guess what, a waste of time. Hopefully you will appreciate the irony. When your right hand is free, we can maybe discuss time dilation and such.

Since when is time a constant, rather than a variable?

It depends upon who you ask. The point is, can a person prove that anything is a constant. You need a point of reference, and that point of reference must be proven as absolute. In reality we make assumptions that work for practical purposes. That they work does not make the assumptions fact. The OP raised this issue, and I am playing devil's advocate. Debate involves parties presenting alternate views.

C'mon people, my earlier post only needs another 2 OT's and I'll depart this discussion.

Speed of light is same everywhere.

"Speed of light is same everywhere."

You are mistaken, pri. The speed of light varies when it passes through different, transparent materials. This is how we define the refractive index of those materials.

Here is some reading for you:

https://micro.magnet.fsu.edu/primer/java/speedoflight/index.html