Is Light Truly Constant Despite Its Properties?

[smokeee77]

I understand that it makes the relativity theory work nicely, but...


Whether it's a particle or wave, light must have mupltiple speeds.
Light particles can be charged or excited which would increase the speed of the particle.
Light also has different wavelengths, each with different oscillations and travel length.


All this seem to support that light is NOT a constant.

 

[JesseM]

I understand that it makes the relativity theory work nicely, but...


Whether it's a particle or wave, light must have mupltiple speeds.
Light particles can be charged or excited which would increase the speed of the particle.

Higher energy photons have larger frequencies (shorter wavelengths), not different speeds. This is determined by the quantum equation E=hf, where E is the energy, h is Planck's constant, and f is the frequency.

Light also has different wavelengths, each with different oscillations and travel length.

Waves can have different wavelengths but the same speed; wavelength refers to how far apart the peaks of the wave are, speed tells you how fast a disturbance in the form of a wave actually travels (in the case of a wave with a single uniform frequency as opposed to a superposition of multiple frequencies, the speed is just the phase velocity which means it's the speed at which each of the peaks is actually moving).

 

[A.T.]

I understand that it makes the relativity theory work nicely, but...

No you don't understand. Relativity theory was developed because light speed is constant, not the other way around.

 

[DukeofDuke]

Well in a way you are right. Light speeds are not constant.

The speed of light through any given medium is constant (including vacuum).

 

[fluidistic]

Well in a way you are right. Light speeds are not constant.

The speed of light through any given medium is constant (including vacuum).

I don't know if the OP was talking about the speed of light or light itself, as the title and

All this seem to support that light is NOT a constant.

suggest.

Light particles can be charged or excited which would increase the speed of the particle.

I never heard yet of a charged light particle. Do you mean electrically charged?
By the way, how would you excite a photon?

 

[Fredrik]

Well in a way you are right. Light speeds are not constant.

The speed of light through any given medium is constant (including vacuum).

Most people who say "constant" mean "invariant", i.e. the same in all inertial frames. Only the speed of light in vacuum is invariant.

 

[DukeofDuke]

Most people who say "constant" mean "invariant", i.e. the same in all inertial frames. Only the speed of light in vacuum is invariant.

No, most physicists who say constant in this case mean invariant.

Most physicists though, don't assume an increase in wavelength means an increase in speed, most physicists would consider the rather obvious possibility of frequency decrease...I'm going to guess OP is not "most physicists."

Just trying to get the point across that light does have different speeds in some cases.

 

[DukeofDuke]

But yeah, light was measured to be invariant experimentally. So, no matter how much you like or dislike a theory, if nature kills it, She kills it. Light, nature says, propagates through a vacuum at the same speed regardless of frame of reference.

 

[smokeee77]

I never heard yet of a charged light particle. Do you mean electrically charged?
By the way, how would you excite a photon?

I understand that highly charged photons are released by our sun constantly, but
Gamma bursts should release light particles at faster than light speed.

We know through observation that light is affected by gravity and also by heat.
These two variables lead me to believe that light speed is not a set velocity.
Especially when dealing with light from far off traveling through various gravitational and temperature changes, while still remaining in a vacuum.

For example; If light can be sucked into a black hole, then it can also be repelled by an exploding star.

 

[fluidistic]

I understand that highly charged photons are released by our sun constantly, but
Gamma bursts should release light particles at faster than light speed.

Please explain what do you mean by "charged photons".

We know through observation that light is affected by gravity and also by heat.

By heat of what? The medium the light is going through?

These two variables lead me to believe that light speed is not a set velocity.
Especially when dealing with light from far off traveling through various gravitational and temperature changes, while still remaining in a vacuum.

For example; If light can be sucked into a black hole, then it can also be repelled by an exploding star.

I don't know Relativity but from what I've heard light is not "sucked" by black holes. Rather it always follows the same direction which can be curved because the presence of mass. (Anyone correct me if I'm wrong).
Light is emitted from starts, not repelled.
I suppose you believe photons to be electrically charged, right?

 

[smokeee77]

Please explain what do you mean by "charged photons".

By heat of what? The medium the light is going through?

I don't know Relativity but from what I've heard light is not "sucked" by black holes. Rather it always follows the same direction which can be curved because the presence of mass. (Anyone correct me if I'm wrong).
Light is emitted from starts, not repelled.
I suppose you believe photons to be electrically charged, right?

*Example of a charged particle from the sun hitting our atmosphere is the Aurora Borielis.
All electromagnetic radiation has particle-like properties as discrete packets of energy, or quanta, called photons. The frequency of the wave is proportional to the particle's energy. Because photons are emitted and absorbed by charged particles, they act as transporters of energy. The energy per photon can be calculated from the Planck–Einstein equation:
where E is the energy, h is Planck's constant, and f is frequency.

*I stated that the medium was a vacuum, the heat & gravitational forces would come from nearby stars.

*Mass does produce gravity, but gravity is the force that will cause light to bend.
The gravity of a black hole is so great that any light traveling too close will be drawn into the singularity, never to escape. Reguardless of direction of travel.
Hence the reason I said the black hole "sucked up light".

 

[jambaugh]

Whether it's a particle or wave, light must have mupltiple speeds.

This is your conclusion, what is your justification?

Light particles can be charged or excited which would increase the speed of the particle.

Charged with what? Not electric charge as light carries no electrical charge. You can "boost" light i.e. increase its frequency. It sounds like you are confusing speed with energy or momentum.

Or maybe you are confusing amplitude with speed. If you are talking about a mass on a spring or vibrating string then yes increasing frequency and energy will "speed up" the transversal motion. But the speed of light is not how it moves transversally but how fast the wave moves through the medium (propagation).

Imagine a long heavy string stretched out horizontally. You strum is lightly at one end and the pulse moves down the string at a given propagation speed. If you watch a point on the string as the wave passes you'll also see a transverse (up and down) speed of the string itself while the wave goes by. Strum harder and you'll get faster transverse speeds but the propagation speed will generally be about the same.

With light the transverse "motion" is not in any measurable dimension but rather a more abstract degree of freedom. There's no way to speak of the "transverse speed" only the amplitude of the transverse component (how strong the electromagnetic fields get at that point). (Note you can create an imaginary model of what is happening so that so that the EM field is a motion of some extra dimension [look up Kaluza-Klein theory] but again this gets far away from the usual meaning of speed of light as the speed of propagation.)

Light also has different wavelengths, each with different oscillations and travel length.

Wavelength multiplied by frequency gives the speed. Double the frequency and halve the wavelength and you get a wave traveling at the same speed. Here you are implicitly assuming frequency is fixed when you assert changing wavelength implies changing speed and assuming wavelength is fixed when you assert different "oscillations" (which I take to mean frequency) implies changing speed.

Assume instead that the speed is constant and you get that increasing the frequency implies decreasing the wavelength and vis versa.

All this seem to support that light is NOT a constant.

You can't argue the speed of light, you measure it. Go out and measure the speed of light you'll see it is a constant (in a vacuum). That's what makes it science and not religion. This has been done to the degree that we really can't measure distances precisely enough to test any further.

One gets another version of the above three-way comparison. To measure a speed we must also measure a distance and a time. Saying one is constant is only meaningful relative to the other two. Since theory and practical measurement seem to agree with respect to the speed of light in vacuum we now adopt this as a mathematically fixed value and define distances in terms of how long it takes light to travel them. So now basically the speed of light (in vacuum) is defined to be a constant. This is a good definition so long as no dispersion occurs in vacuum which I explain next:

Now some (actually most) mediums are called dispersive which means that different frequencies will travel at (slightly) different speeds through the medium. This is why for example a prism separates light into different frequencies. The different frequencies refract different amounts. The amount they refract is determined by the difference in speeds as they cross into/out of the medium. Since different frequencies change speeds by different amounts they refract at different angles.

Dispersion is a problem for making good camera lenses and telescope lenses because you want the "red" "green" and "blue" frequencies to all focus at the same distance. Dispersive lenses will have different focal lengths for different frequencies. (Notice the infrared mark on camera lenses indicating where they focus relative to visible light.)

But the degree to which the vacuum is free of dispersion has been confirmed to the limits of current measurements. See the wikipedia article http://en.wikipedia.org/wiki/Speed_of_light" for references.

 

[fluidistic]

*Example of a charged particle from the sun hitting our atmosphere is the Aurora Borielis.

From wikipedia :

Auroras are produced by the collision of charged particles from Earth's magnetosphere, mostly electrons but also protons and heavier particles, with atoms and molecules of Earth's upper atmosphere (at altitudes above 80 km (50 miles)).

, although it agrees with your statement, it clearly does not say that photons are charged particles like you previously said.

*I stated that the medium was a vacuum, the heat & gravitational forces would come from nearby stars.

Ah ok. So you say that heat by radiation can excite photons? (you exactly said :

We know through observation that light is affected by gravity and also by heat.

). I'll wait for someone else to confirm/infirm your statement but as far as I know you won't affect photons by radiating them with other photons.

I prefer letting others to answer in details your questions. I'm sincerely not qualified enough.

 

[jtbell]

*Example of a charged particle from the sun hitting our atmosphere is the Aurora Borielis.

I think you may be confusing protons (which are charged) with photons (which are not charged).

 

[fluidistic]

Thanks jambaugh for the good explanation.

I think you may be confusing protons (which are charged) with photons (which are not charged).

I don't think he is. He considered "photons" as light and having wave-like properties. I think he believes photons are electrically charged particles, like he said twice.

 

[smokeee77]

As a photon is absorbed by an atom, it excites an electron, elevating it to a higher energy level. If the energy is great enough, so that the electron jumps to a high enough energy level, it may escape the positive pull of the nucleus and be liberated from the atom in a process called photoionisation.
Conversely, an electron that descends to a lower energy level in an atom emits a photon of light equal to the energy difference. Since the energy levels of electrons in atoms are discrete, each element emits and absorbs its own characteristic frequencies.

 

[Integral]

As a photon is absorbed by an atom, it excites an electron, elevating it to a higher energy level. If the energy is great enough, so that the electron jumps to a high enough energy level, it may escape the positive pull of the nucleus and be liberated from the atom in a process called photoionisation.
Conversely, an electron that descends to a lower energy level in an atom emits a photon of light equal to the energy difference. Since the energy levels of electrons in atoms are discrete, each element emits and absorbs its own characteristic frequencies.

What has that got to do with this thread?

 

[Vanadium 50]

That's true. And plagiarized from the New World Encyclopedia. And unsupportive of your claims.

 

[smokeee77]

Look I'm trying to think outside of the box here, not quibble about semantics.
Forgive me if I am not up to speed on fermion's and gluon's and everything in quantum mechanics as I have only completed the 7th grade.

In my opinion physics is common sense, as long as you can identify all of the components and variables.

We've all been taught that light travels at 186,000 miles per second.
As does all electromagnetic radiation, including: radio waves, microwaves, terahertz radiation, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays.

It's so fast that we can really only estimate the speed. Even if there are infinitesimal differences, say between red and blue light, it may not matter in the grand scheme of things. As we can really only guestimate the speed of white light.
Such is the case with Pi commonly being shortened to two decimal places. You can have round and rounder... but it's close enough for most work.


Maybe light is only affected by heat while in a medium, and the wavyness or mirage's occur because of refractive changes, which means the effect I witnessed is only optical and not actual.

Gravity however does essentially "bend" the trajectory of light without a medium or phase change. Does that mean that light could have a mass? Maybe not, but how exactly does gravity affect light?
Could enough gravity actually pull light in faster, could the force be strong enough to cause light to accelerate?
Or could a massive stars outbound velocity of light be slowed until it breaks free of the gravitational waves? Sortof like going through a medium, but the medium is actually gravity in a vacuum.

Conversly, why couldn't a super nova push EM energy or even mass out faster than 186,000 mps?

It seem that special relativity says that not matter how fast I am going light will still travel 186,000 mps away from me.
So if could be traveling near 186,000 mps and shine a flashlight in from of me. Would that light be traveling at twice the speed of light to a third party stationary observer?

 

[Vanadium 50]

Look I'm trying to think outside of the box here... I have only completed the 7th grade.

Son, before you "think outside of the box" you have to know where the box is.

You've made a bunch of claims that are completely unsupported by evidence and observation. Doesn't it make sense to learn how the universe works first, before going around telling people that have studied this for longer than you've been alive that they are wrong?

 

[Fredrik]

In my opinion physics is common sense, as long as you can identify all of the components and variables.

"Common sense" isn't very useful in relativity, since we all have the same intuitive ideas about what the properties of space and time should be, and those ideas have been proved wrong.

We've all been taught that light travels at 186,000 miles per second.
As does all electromagnetic radiation, including: radio waves, microwaves, terahertz radiation, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays.

We usually call all those things "light". They are just different wavelenghts, but you know that already.

Even if there are infinitesimal differences, say between red and blue light, it may not matter in the grand scheme of things.

There's no such difference in any of the current theories (classical electrodynamics, quantum electrodynamics, general relativity). It's of course possible that there's a (very small) difference in the real world, which would then have to be explained by some future theory. (I think loop quantum gravity has already predicted a difference),

Gravity however does essentially "bend" the trajectory of light without a medium or phase change. Does that mean that light could have a mass? Maybe not, but how exactly does gravity affect light?

It doesn't affect light directly. It affects the geometry of spacetime, changing what curves through spacetime we have to consider "straight". Light travels along those "straight" lines.

Could enough gravity actually pull light in faster, could the force be strong enough to cause light to accelerate?

Something that's traveling along one of those "straight" lines (they're actually called "geodesics") is by definition not accelerating. Proper acceleration is (in special relativity and general relativity) a measure of the deviation from geodesic motion. Note however that a geodesic is a straight line through spacetime, but its projection onto "space" (which is a certain 3-dimensional subspace of 4-dimensional spacetime) is a curved path. "More gravity" would curve that path even more, but that doesn't mean that light can be accelerated. (You can always define a coordinate system on spacetime in which its speed is changing, but that doesn't mean that it's accelerating in an objective sense).

Conversly, why couldn't a super nova push EM energy or even mass out faster than 186,000 mps?

Because massless particles (light) travels along null geodesics, and massive particles along timelike geodesics. This can be taken as the definition of "massive" and "massless". The energy required to accelerate a massive particle to speed v goes to infinty as v goes to c.

It seem that special relativity says that not matter how fast I am going light will still travel 186,000 mps away from me.

Right.

So if could be traveling near 186,000 mps and shine a flashlight in from of me. Would that light be traveling at twice the speed of light to a third party stationary observer?

No. Velocites in special relativity "add up" according to the rule

u\oplus v=\frac{u+v}{1+\frac{uv}{c^2}}

assuming that they're in the same direction or opposite directions. Otherwise the formula gets much more complicated. The \oplus notation isn't standard. It's just what I like to use.

 

[matheinste]

Look I'm trying to think outside of the box here.

It seem that special relativity says that not matter how fast I am going light will still travel 186,000 mps away from me.
So if could be traveling near 186,000 mps and shine a flashlight in from of me. Would that light be traveling at twice the speed of light to a third party stationary observer?

When it comes to thinking outside the box Einstein gets 10 out of 10.

You are traveling at just below light speed, as well as any other sub luminal speed, relative to some objects in the universe. You are also stationary relative to others. The word relative is important and necessary.

Matheinste.

 

[DaveC426913]

In my opinion physics is common sense, as long as you can identify all of the components and variables.

Dead wrong.
"Common sense" requires you to have experienced it before, for it to be common (you must have something to compare it to). When is the last time you hung out near a black hole or exploding star are few in a spaceship at the speed of light? Using your daily Earthly experiences to form your "common sense" will reap only tears and heartache.

It's so fast that we can really only estimate the speed. Even if there are infinitesimal differences, say between red and blue light, it may not matter in the grand scheme of things. As we can really only guestimate the speed of white light.
Such is the case with Pi commonly being shortened to two decimal places. You can have round and rounder... but it's close enough for most work.

Among other things, GPS tracking systems currently in use in cars are dependent on us knowing the speed of light to a very fine degree. They can pinpoint a location within metres - a distance light can travel in a few billionths of a second. And that's just a $100 application. There are applications that cost billions; their precision requirements will be proportionate.

Gravity however does essentially "bend" the trajectory of light without a medium or phase change. Does that mean that light could have a mass? Maybe not, but how exactly does gravity affect light?
Could enough gravity actually pull light in faster, could the force be strong enough to cause light to accelerate?

No. Light is not "pulled" or "sucked" by gravity. Gravity bends space. Light follows straight paths through bent space. No matter how tortuously you bend the space, it will not alter the speed with which light travels through it.

Conversly, why couldn't a super nova push EM energy or even mass out faster than 186,000 cmps?

It seem that special relativity says that not matter how fast I am going light will still travel 186,000 mps away from me.
So if could be traveling near 186,000 mps and shine a flashlight in from of me. Would that light be traveling at twice the speed of light to a third party stationary observer?

This is better. Asking questions, not making claims, is the way to enlightenment. Ask more questions. Make fewer claims.

why couldn't a super nova push EM energy or even mass out faster than 186,000 mps?

It would require an infinite amount of energy to accelerate any mass to the speed of light, let alone beyond it.

So if could be traveling near 186,000 mps and shine a flashlight in from of me. Would that light be traveling at twice the speed of light to a third party stationary observer?

The light would travel away from you at exactly c as measured by you. The light would travel away from you just slightly faster than you are moving as measured by an external observer. The difference in observations is due to time dilation due to differing frames of reference. This is Einstein's legacy.

 

[Austin0]

=DaveC426913;2349794]Among other things, GPS tracking systems currently in use in cars are dependent on us knowing the speed of light to a very fine degree. They can pinpoint a location within metres - a distance light can travel in a few billionths of a second. And that's just a $100 application. There are applications that cost billions.

Hi Do you know if the GPS system applies the same speed evaluation for up signals as it does for down signals?

No. Light is not pulled by gravity. Gravity bends space. Light follows straight paths through bent space. No matter how tortuously you bend the space, it will not alter the speed with which light travels through it.

Does this mean that the time dilation in a lightclock at a low gravitational altitude, say approaching a black hole would be the result of curvature?
Would this somehow mean that the bending of spacetime would actually increase the distance of the reflection?
Thanks

 

[Dale]

It's so fast that we can really only estimate the speed.

While that is technically true it is also true for any measurement. You always obtain an estimate. The real question is how close is the estimate.

In 1979 the speed of light was measured by Baird and Whitford to be 299792458 m/s with an error (standard deviation) of only 0.2 m/s. That is a error (coefficient of variation) of 0.00000007%. That is a REALLY good estimate!

In fact, it is such a good estimate that there was much more uncertainty in previous standards of the meter, so in 1983 c was defined to be exactly 299792458 m/s meaning that there is no uncertainty in the speed of light and there was instead a 0.00000007% uncertainty in the length of the meter. Further improvements in our ability to measure the speed of light have reduced the uncertainty in the length of the meter to about 0.0000000025% in typical laboratory settings.

Even if there are infinitesimal differences, say between red and blue light, it may not matter in the grand scheme of things.

Differences in speed are usually easier to detect than actual speeds, so these types of experiments typically have even higher accuracy. As of 1999 Schaefer measured them to be equal to within a few parts in 10^21 using 30 keV and 200 keV light.

 

[Naty1]

Smokee: it's sometimes helpful to remember that light does NOT travel the same way as, say, water waves which require a transport medium. Your comments about speed and other's comments about amplitude (wave height) are quite relevant regarding water waves...you can find formulas relating the variables for water waves with wave speed online. However, "common sense" (logic) does not require that light obey any of those formulas.

Since water has phases states (solid, liquid,gas) would you expect light to as well? Regardless of your answer, you'd want some verification rather than a pure guess...(I hope)...that's also physics...


Why light travels at an invariable speed is one of nature's many mysteries. As for thinking outside the box, that IS what Einstein did. But he also had several ideas "outside the box"...How did he pick the one we all know?? He picked the theory that he believed would be experimentally verified... He trusted his own "logic" but not beyond what experiment would confirm...

Finally, you will find that everyday "logic" is ok for most of (classical) physics through high school. But when you get into cosmology and quantum theory, for example, you'll need to develop a different set of logic...some new rules that don't apply to everyday things around you...a simple example: how many dimensions do you perceive? Might there be others??

Good luck with your studies...

 

[DukeofDuke]

The whole thing between the flashlights...is very interesting. Here is why your notion of "seeing" velocities add up is wrong.

In our world, information seems to reach us instantly. There's no lag a car for a onto the road, and you seeing that car, which is why you don't crash into him. If you ever play video games, you know what I mean by lag...but in our world, because of how fast light travels in comparison, we see things practically in "real time." No lag.

The problem is, once you are going at very fast speeds close to light, you can't rely on this near instantaneous transmission of light/information. So even if you were going near the speed of light and flashed a light and a third observer saw, the basic reason why he won't see it going at c+your speed is because of that lag (because now it takes time for the light from him to reach us, significant amounts of time). So basically, you just can't see things, even know things, instantaneously anymore, and that creates major problems with what two people at relativistic speeds perceive.

As you can guess, time, space, and velocity are all tied into one another.

You can do the actual math calculations by doing some basic Lorentz transformations, but the intuitive reason why the work, at least to me, is because in our normal lives we assume we can see everything instantaneously. But at relativistic speeds, there is always an information lag, which screws with what we perceive to be other people's speeds, locations, and times. (location and times actually melding into spacetime but you get the picture).

Don't let the physicists get you down as an undergrad myself, I ask a lot of "wait wtf" questions too. The only thing I'd suggest is, as the guy above said, don't make as many claims when you're actually trying to understand something because that annoys people and gets in the way of you understanding it...

once you DO understand something, (and that takes a lot and a lot of hard thought), maybe THEN you and I can make some claims =)

 

[matheinste]

The whole thing between the flashlights...is very interesting. Here is why your notion of "seeing" velocities add up is wrong.

In our world, information seems to reach us instantly. There's no lag a car for a onto the road, and you seeing that car, which is why you don't crash into him. If you ever play video games, you know what I mean by lag...but in our world, because of how fast light travels in comparison, we see things practically in "real time." No lag.

The problem is, once you are going at very fast speeds close to light, you can't rely on this near instantaneous transmission of light/information. So even if you were going near the speed of light and flashed a light and a third observer saw, the basic reason why he won't see it going at c+your speed is because of that lag (because now it takes time for the light from him to reach us, significant amounts of time). So basically, you just can't see things, even know things, instantaneously anymore, and that creates major problems with what two people at relativistic speeds perceive.

As you can guess, time, space, and velocity are all tied into one another.

You can do the actual math calculations by doing some basic Lorentz transformations, but the intuitive reason why the work, at least to me, is because in our normal lives we assume we can see everything instantaneously. But at relativistic speeds, there is always an information lag, which screws with what we perceive to be other people's speeds, locations, and times. (location and times actually melding into spacetime but you get the picture).

Don't let the physicists get you down as an undergrad myself, I ask a lot of "wait wtf" questions too. The only thing I'd suggest is, as the guy above said, don't make as many claims when you're actually trying to understand something because that annoys people and gets in the way of you understanding it...

once you DO understand something, (and that takes a lot and a lot of hard thought), maybe THEN you and I can make some claims =)

All relativistic observations take into account and allow for light transmission times. These transmission times are not the reason for the observed relativistic effects.

Matheinste.

 

[jambaugh]

Look I'm trying to think outside of the box here, not quibble about semantics.
Forgive me if I am not up to speed on fermion's and gluon's and everything in quantum mechanics as I have only completed the 7th grade.

In my opinion physics is common sense, as long as you can identify all of the components and variables.

"Common sense" or intuition only works well if you hone it with disciplined study.
For much of history it was "common sense" that the Earth was flat.
Very often to understand new physical concepts we must fight our "common sense", accept what careful observation has shown, and study in careful detail what the new theories predict.
Eventually as you master the subjects your intuition will fall in line with the physics and you can trust your "common sense" again.

As for "quibbling about semantics", words mean things. More especially in science words have exact formal meaning and if in a discussion one does not use a concept correctly one gets into serious confusion.

We've all been taught that light travels at 186,000 miles per second.
[...]
It's so fast that we can really only estimate the speed. Even if there are infinitesimal differences, say between red and blue light, it may not matter in the grand scheme of things. As we can really only guestimate the speed of white light.
Such is the case with Pi commonly being shortened to two decimal places. You can have round and rounder... but it's close enough for most work.

We can observe the speed quite accurately. Foucault's experiment got it to 5 decimal places.

And again we now take the speed of light to "infinite precision" because its value is now defined by convention instead of as an observed value. It is basically now a unit conversion constant like 12 inches per foot. We did this because the common convention defining a standard meter became less precise than the level of precision we had for the definition of one second and for measurements of the speed of light.

As to the rest of your post and questions... what are you looking for here? If you would like to fully understand Einstein's Special Theory of Relativity you will need a bit of math... more than you get in the 7th grade.

If you just want to get a sense of it well I suggest you do some reading. There have been many good threads on this forum discussing time dilation, length contraction, etc. There are some good on-line references, check out wikipedia.

I'd be happy to go through each concept as well. Some find I'm pretty good at breaking things down to make them understandable. But you need to do some homework as well. There are no shortcuts to understanding. You need math ... at least at the level of trigonometry and analytic geometry that you get in high school. Calculus would be very good too. You should study basic Newtonian mechanics so you understand the hard mathematical meaning of: Force, Energy, Momentum, Mass, Velocity, and Acceleration.

Before you go disagreeing with things you need to fully understand what is said and why. Your "common sense" will not always be helpful. The starting point is to understand what Science, and Physics is all about. The distinct characteristic of science is that "what we know" is based on "what we systematically and repeatably observe". We can't argue away the results of an experiment. We can't ignore experiments which contradict "common sense". We must formulate theories which are consistent with what happens in the lab or the observatory.

You should read up on various experiments confirming SR and especially you should understand why what they measured is important.

I don't want to discourage you. It takes work but you get great return on that investment.

 

[smokeee77]

Very good points!

I can imagine the logic and of course it makes sense! But just as was mentioned, many people once believed the Earth to be flat, because that's was the popular opinion.

The current speed of light was estimated at least 150 years ago by a guy with mirrors measuring minute angles, and that popluar opinion has remained the same ever since.
Don't mean to be a doubting Thomas, but I do like to play the deils advocate occaisionally.
Mainly because I fear that accepting what everyone else has already taken for granted may cloud my ability to identify hidden truths.

I can visualize the spacetime model as a sheet stretched out with large depressions formed by the stars, ect. In this model I can see how the path of light would dip from the plane with the curve created by a depression, causing the light to essentially bend to follow the spacetime model.
In this model the light would actually travel further because of the stretch in the spacetime, and should cause an observer a mirage of some sort. For the same reason you see a mirage of sorts when light changes meduim. Such as observing a pencil sticking out of a bowl of water. Which to the observer, the light(pencil) appears to bend.
If lights' speed doesn't change; then the light must be traveling a longer distance through the denser meduim. Just as it appears to do near a celestial body.

This seem more like common sense once I add in the right variables.

 

[DaveC426913]

I can visualize the spacetime model as a sheet stretched out with large depressions formed by the stars, ect. In this model I can see how the path of light would dip from the plane with the curve created by a depression, causing the light to essentially bend to follow the spacetime model.

...and should cause an observer a mirage of some sort.

Yes. Google "Einstein rings" and "gravitational lensing".

For the same reason you see a mirage of sorts when light changes meduim. Such as observing a pencil sticking out of a bowl of water. Which to the observer, the light(pencil) appears to bend.
If lights' speed doesn't change; then the light must be traveling a longer distance through the denser meduim. Just as it appears to do near a celestial body.

This seem more like common sense once I add in the right variables.

Don't confuse refraction through a medium with bending of space-time. While they may seem similar, they are not the same things. That is where your common sense will get you into trouble.

 

[DukeofDuke]

All relativistic observations take into account and allow for light transmission times. These transmission times are not the reason for the observed relativistic effects.

Matheinste.

Aren't Lorentz transformations based on the fact that light has a maxed out speed, that is, information cannot go faster than c?
Yeah, once you establish your Lorentz transformations and do an actual problem, you don't need to consider light transmission times- that is because its built into your transformation.

But, is it not true that the base reason relativistic effects are noted is because you approach speeds that are "noticeable" by c and thus you create distortions to account for why c doesn't notice them?

What I'm saying is, I know light transmission times are taking into account, but are these transmission times also motivation for creating the new system in the first place?

 

[smokeee77]

BWT... Accurately calculating angles of light reflected from 150 year old mirrors sounds about as difficult as how ancient egyptians moved the stone to build the pyramids.

Link to religious dogma deleted.

Integral

 

[matheinste]

Hello DukeofDuke.

Light transmission was known to be not instantaneous long before special relativity was required to solve other problems. The postulate of the same constant speed of light for all inertial observers is really the cornerstone of special relativity. What that speed happened to be is immaterial.

It is of course true that relativistic effects are only significant at very high velocities, but they apply at any subluminal velocity.

Matheinste.

 

[Dale]

The current speed of light was estimated at least 150 years ago by a guy with mirrors measuring minute angles, and that popluar opinion has remained the same ever since.
Don't mean to be a doubting Thomas, but I do like to play the deils advocate occaisionally.
Mainly because I fear that accepting what everyone else has already taken for granted may cloud my ability to identify hidden truths.

No reason to take anything on faith. Go ahead and read the evidence for yourself. The FAQ section on http://www.edu-observatory.org/phys...ents.html#Measurements_of_the_Speed_of_Light" is a good place to start.

Btw, I would not say that the speed of light measurements have remained the same for the last 150 years. The precision has increased by many orders of magnitude over that time.

 

[f95toli]

The current speed of light was estimated at least 150 years ago by a guy with mirrors measuring minute angles, and that popluar opinion has remained the same ever since.
Don't mean to be a doubting Thomas, but I do like to play the deils advocate occaisionally.
Mainly because I fear that accepting what everyone else has already taken for granted may cloud my ability to identify hidden truths.

Before the re-definition of the meter in the SI 1983(?) several NMIs put a LOT of effort into acuratelly measuring the speed of light. This means that extremely accurate indepdendent measurements were done in labs all over the world over a long period of time; needless to say they all got the same value (with some the error bars). Some labs even built dedicated facilities to do this; meaning a lot of money and many man-hours went into this project.
It might perhaps be worth pointing out that it is not at all "obvious" that they would get the same value; measurements at this level are extremely complicated and small errors can cause a lot of problem; but a change in the SI is only done if ALL labs agree to within some agreed accuracy.

(right now the two best measurments of Planck's constant do NOT agree which is why the SI won't be modified to take these values into account this time round)

The point is that we can be VERY sure that the speed of light is constant and that the current value is extremely good (although we can of course never be 100% sure about anything in science).

 

[statdad]

"But just as was mentioned, many people once believed the Earth to be flat, because that's was the popular opinion. "

this is actually not true: the notion of the Earth being essentially spherical (decidedly not flat) occurred long ago: Aristotle reasoned the Earth wasn't flat by considering how the constellations appeared to rise earlier when sailors were headed south than when they were headed north. that was about 330 BC.

Pliny the Elder asserted, in approximately 1AD, that people should be in agreement that the Earth was spherical.

Indian astronomers reached the same conclusion later, and Jesuits had a hand in spreading the idea of a round Earth in parts of china in the 17th century.

Why do I mention this? To indicate that it doesn't make sense to make a scientific assertion that runs counter to theory and evidence, and fall back on "well yes, but for many years scientists thought the Earth was flat, and look how that turned out" as your defense.

I'll now return to "statistician with an interest in history and physics who lurks around reading these posts" mode.

 

[DukeofDuke]

Hello DukeofDuke.

Light transmission was known to be not instantaneous long before special relativity was required to solve other problems. The postulate of the same constant speed of light for all inertial observers is really the cornerstone of special relativity. What that speed happened to be is immaterial.

It is of course true that relativistic effects are only significant at very high velocities, but they apply at any subluminal velocity.

Matheinste.

yeah I'm agreeing with all of that =)

All I'm saying is that at very slow relative speeds, light seems to be practically instantaneous. Whereas, when you take speeds a tenth or more of light you think you'd observe light slowing or speeding up as you go with it classically, yet the valid assumption is made that c is the greatest possible speed (at least, that's the assumption for the Lorentz), and from that we get space and time dilation to fix the apparent contradiction. And then we have experiment verify it for us.

I was just mentioning noticeably "lag time" in information flow as one of the reasons special relativity makes some intuitive sense. Merely noting that before you even need to think about the Lorentz transformations, you can sort of make sense of some correction needed to classical ways of thinking about speed, because if you go fast enough you'll lose the "instantaneous" apparent affect. And you'd think that'd mess with your perceptions of space and time, because our assumption that event A happened at this time t is based on the assumption that we as an observer can locally measure some light from event A at around this time t as well. Once you get to relativistic speeds, you need to redefine your notion of space and time to account for the fact that you don't really know what's going on where, because its impossible for signals to reach you at anything considered near instantaneous. =)

 

[Pippo]

I understand that it makes the relativity theory work nicely, but...


Whether it's a particle or wave, light must have mupltiple speeds.
Light particles can be charged or excited which would increase the speed of the particle.
Light also has different wavelengths, each with different oscillations and travel length.


All this seem to support that light is NOT a constant.

I would say:
Maximum speed is just a characteristic of the environment called space-time and speed of light is a show of it, so it is independent by the intensity or frequency. Light conforms with, and so well describes, the behaviour of our space-time.