Speed of Light frame of reference

[Dantassii]

If you watched the original Cosmos series by Carl Sagan, in 1 of the episodes he explains some discoveries made in the late 19th and early 20th centuries:

1. The speed of light in a vacuum is constant no matter what frame of reference you use.
2. Thou shalt not add your speed to the speed of light.
3. Nothing w/mass can reach or exceed the speed of light.

Something else was discovered when it comes to things moving near the speed of light, and that is the light waves coming off said object moving near the speed of light are compressed towards the blue side of the spectrum if the object is moving towards you, or stretched into the red side of the spectrum if the object is moving away from you. This is called the doppler effect and it is similar to what happens to sound waves from an object moving through air (a train is used in the Cosmos example).

The effects of time dialation are also explained in a simple and concise manner using the example of a kid on a motor scooter traveling around the countryside outside the city of Vinci, home of Leonardo.

These are all proven laws of nature that have survived over a century of testing and experimentation. They provided the assumptions that Einstein used to develop his Theory of Special Relativity, which gave us the famous equation that relates energy to mass:

E = mc*c

To quote Carl, "For the laws of nature to be obeyed, very strange things must happen as you approach the speed of light."

I would highly recommend watching the original Cosmos series for anyone interested in getting an introduction of how space and time are related and where we as citizens of the Cosmos fit into the entire scheme of things. Even though it was made in the 70's and has some dated references, it still is by far the most efficient presentation I have ever seen that puts the whole universe into perspective.

The Cosmos lost a great communicator when Carl passed away.

Dantassii
HUMONGOUS IMS shipbuilder

 

[jedidia]

Check this out:

http://galileoandeinstein.physics.virginia.edu/

It'll take you a while, but it's really well explained. Arm yourself with a notebook and a pocket calculator and reproduce the examples (seriously, this is important. The text helped me understand the equations, but the equations were what finally made me understand the concept).
The math isn't very difficult either. Basic trigonometry is the most complex you are going to need.

 

[n122vu]

Its frame of reference is its own velocity vector; more specifically, how far it would move along its direction of travel between two arbitrary points along that path.

 

[SanderBuruma]

Is there some literature detailing the experiments that tested the propositions of Special Relativity?

 

[Urwumpe]

Is there some literature detailing the experiments that tested the propositions of Special Relativity?

Aside of the Wikipedia article on experiments trying to find violations of the Lorentz transformations (which is the scientific term for the principle that the speed of light is always constant regardless how you are moving)?

[ame="http://en.wikipedia.org/wiki/Modern_searches_for_Lorentz_violation"]Modern searches for Lorentz violation - Wikipedia, the free encyclopedia[/ame]

 

[SanderBuruma]

Other maybe than that yes, I have difficulty understanding things that are so highly theoretical without a physical reference frame or rather I can not trust something to be true without experimentally being able to verify it or reading through someone elses experiment. Most of the literature on that wikipedia page makes tons of rerences to exotic physics I do not understand.

 

[Urwumpe]

Other maybe than that yes, I have difficulty understanding things that are so highly theoretical without a physical reference frame or rather I can not trust something to be true without experimentally being able to verify it or reading through someone elses experiment. Most of the literature on that wikipedia page makes tons of rerences to exotic physics I do not understand.

:facepalm:You are aware, that you are talking about something absolutely theoretical and something that has very little contact with phenomena you can grasp with your own senses? Of course you will only find a lot of theory there. Without a bit of theory, you can't even measure something as fast as the speed of light, because you either need to be extremely accurate in time or capable of using longer measurement distances correctly.

Also... Special relativity and Lorentz transformations are everything but exotic.

But what is the deal of not understanding this experiment and its results?

http://en.wikipedia.org/wiki/Michelson–Morley_experiment

Its from 1887, over hundred years in the past, when trains had still been propelled by steam and cars didn't exist.

 

[Face]

Other maybe than that yes, I have difficulty understanding things that are so highly theoretical without a physical reference frame or rather I can not trust something to be true without experimentally being able to verify it or reading through someone elses experiment. Most of the literature on that wikipedia page makes tons of rerences to exotic physics I do not understand.

Relativity is not easy to understand. However, instead of "not trusting it to be true" it is a better approach to try to understand the "references to exotic physics" IMHO. Even if that means to start from far below.

You can bet that many folks in the past and today - capable of understanding exotic physics - tried to understand it, especially because it is such a counter-intuitive theory. And not surprisingly, they came to the conclusion that it is valid.

Do you think that those folks did not understand it and simply lied in order to "swim with the masses"?

The really impressive thing about relativity is that many things that felt fishy before - like electromagnetic induction in unipolar generators - suddenly become logical once you think about it in relativistic terms, despite them not being especially covered by Einstein's theory. I guess this insight was the point where I really understood the significance of relativity as a valid physical concept.

From this point on, I always look at problems involving speed of light like I look at problems involving perpetuum mobile: I take the known theories for granted until I find proof for it being broken, not the other way around.

 

[Thunder Chicken]

The videos in the Minute Physics channel on Youtube are actually some of the best visual explanations of special relativity and quantum physics that I have seen. They're a bit fast, but short and to the point. You can (and should) work them out on paper to make sure you follow the arguments.

https://www.youtube.com/channel/UCUHW94eEFW7hkUMVaZz4eDg

 

[jedidia]

They're a bit fast, but short and to the point.

Honestly, I don't think I would have understood what he is talking about if I didn't already know what the deal was. Then again, I have almost no capacity for visual imaginagion.

 

[Thunder Chicken]

What I'd really love would be for someone to explain the Standard Model in such a way that a technical layman (such as an engineer like myself) could understand and visualize it. The current descriptions either veer toward superficial understanding ("The Standard Model is a model of the universe. It's full of particles and Greek letters n' stuff. That's all for now folks :hello:") or heavily laden with mathematical jargon and frankly sounding like something that would be mumbled by someone who should be wearing a straitjacket. I haven't seen anything in between.

---------- Post added at 09:48 PM ---------- Previous post was at 08:28 PM ----------

In response to the OP, here's a summary of the history:

Michelson & Morley (1887) determined that the speed of light c was a constant in all directions relative to all observers. A very non-intuitive result, but true nonetheless.

With that tidbit of information, folks could do some thought experiments. My favorite is the one of a person walking on a train.

Assume a train is moving with velocity v1 relative to the platform, and a person is walking on the train with a velocity relative to the train v2. To an observer standing on the platform next to the train, the person appears to be moving with a velocity v1 + v2 = v3, where v3 is the total velocity of the person relative to the platform.

Now change that person into a light wave. The result of the Michelson-Morley experiment says that this light wave must move with velocity c relative to both the train and the platform! That implies both v2 and v3 must be c, or (according to our conventional summation) v1 + c = c, which can't be correct. In truth, the only way for the math to work out is for v1 + v2 = (v1 + v2)/(1 + (v1*v2)/(c*c)). Plug in c for v2 and you recover the equality. You also get the correct answer of v1 + v2 ~ v3 when working at velocities much less than the speed of light.

But if v1 + v2 = (v1 + v2)/(1 + (v1*v2)/(c*c)), that means that the elapsed time seen on the train must be slower than on the platform must be different. This is how the Lorentz transformations were determined, basically just getting the math to reconcile with the observations.

Einstein's E=mc^2 came about by another thought experiment watching the change of energy of an object in two different frames of reference.

So there isn't anything to exotic or weird about all this, it's just reconciling math with known physics. Newton's laws are approximate as he did not have the results of the Michelson-Morley experiment to ponder, just slow apples falling off of trees.

 

[Urwumpe]

The Standard model is "Not" for the universe - it exists in particle physics. Yes, it has some effects on the cosmological models, but the big physical question is still putting microscopical and macroscopical world together into one theory without contradictions. What explains particle physics does not really help explaining the cosmos.

The most standard model of cosmology* is the Lambda-CDM (cold dark matter) model. It is pretty popular now, but already shows limitations. It is still based on Einsteins cosmological constant lambda, which describes the expansion of space (scientists are not really happy with it... but it works), but assumes a large quantity of cold, dark matter in our universe. (To describe it with Terry Pratchetts words: 90% of the universe is bureaucracy). The toughest aspect in the model is still the cosmological constant, but if you can ignore some many implications of it, it is actually some sort of the "idle rpm" of the universe. If lambda is positive, regardless how much the universe expands and how low the density of matter and energy gets, the expansion of the universe will never cease. If it is zero, the expansion will gradually come to a halt in infinity, while the density of energy and matter drops. If it is negative, the expansion could stop or reverse in finite time. Currently, measurements suggest a very very low positive value.



*Some call it the standard model of cosmology, but that's pretty optimistic

 

[Thunder Chicken]

I think this is why I quit physics early in college and went into engineering. Part of physics is trying to model flecks in the paint, some the curvature of the metal, some the fabric on the seats, but what they don't realize is that they are all looking at a car.

I think we're fundamentally not looking at the whole business in a complete way, and I don't see how fitting models to certain parts of it will help matters. The models are our tricks to visualize what is happening, and those visualizations may provide false intuitions.

 

[Urwumpe]

I think this is why I quit physics early in college and went into engineering. Part of physics is trying to model flecks in the paint, some the curvature of the metal, some the fabric on the seats, but what they don't realize is that they are all looking at a car.

I think we're fundamentally not looking at the whole business in a complete way, and I don't see how fitting models to certain parts of it will help matters. The models are our tricks to visualize what is happening, and those visualizations may provide false intuitions.

Well, the problem is: Even car engineers only rarely look at the whole car. You have specialists for engines, air conditioning, suspension, etc. The most complete picture do the people of the car electrics get, but these then look at the car with a electromagnetic eye.

I think thats the wisdom behind the three blinds touching the elephant: Every entity has multiple aspects, that multiple models can describe, but it is hard to find a single model that addresses multiple aspects.

 

[Thunder Chicken]

Well that's just it, seeing only parts of the picture can lead to a misleading overall conclusion.

Here is a video of an old game show called Catch Phrase that illustrates the partial-picture problem:

https://www.youtube.com/watch?v=GJQdEY82zs0