Undergrad Can I be taught general and special Relativity on this forum

[itfitmewelltoo]

No its a theory believe it or not about symmetry. The link I gave before explains it:
http://www2.physics.umd.edu/~yakovenk/teaching/Lorentz.pdf

But you need math you probably do not have yet to understand it - you need to build up to it.
Well exist is a very philosophically loaded word in this contest best to not use it.

Here is a better way of looking at it.

Imagine you have a rod wider than your door you want to get through it. How do you do it? You rotate it - then it will fit. Now a watch you carry around with you is like the rod. All velocity does is rotate it so its smaller as seen by the door. In fact mathematically, by what's called hyperbolic rotation, that's just what is going on.

Using this view is time dilation real - that's a philosophical question. The theory doesn't answer that - it just tells you the results - like the rod is smaller in the direction of the width of the door if you rotate it.

How is the twin paradox resolved - well for one twin they are subject to accelerations - and that, at rock bottom is the answer. But you can read the detailed answer here::
http://www1.phys.vt.edu/~jhs/faq/twins.html

What is the rock bottom explanation of GR - simply that when gravity is present space-time is curved. Once you accept that then GR more or less falls out - but the mathematics of why is not trivial.

Thamks
Bill

Excellent. You hit on the two fundamental issues that people run into.

The first is they want to skip the bachelor's and master's material and jump right to the philosophical questions. And the can't, it simply doesn't work that way. You know, and I know, what are the philosophical questions because we studied the science.

The second, which you've implied, is what the twin paradox is. Many are under the false understanding that is a conclusion about reality that Relativity claims. It is the complete opposite. It is a paradox, and understood error that the logic of Special Relativity runs up against. Every system of logic will have a paradox that cannot be resolved within it. (No reference) General Relativity resolves the conflict by incorporating acceleration and gravity. It is the acceleration of one twin that accounts for time dialation. Even this resolved, Einstein remained concerned that the conclusion of the existence of the black holes was an unresolved paradox from General Relativity.

Now, as you said, the math of this is untenable. There is simply no satisfactory explanation of GR that a thoughtful person can have without the BS and MS material that comes before.

 

[PeterDonis]

Many are under the false understanding that is a conclusion about reality that Relativity claims. It is the complete opposite. It is a paradox, and understood error that the logic of Special Relativity runs up against.

This is not correct. The twin "paradox" is not an actual paradox in SR. It is an illustration of how SR spacetime geometry works. You do not need GR to explain the result in the standard setting of the paradox, which is in flat spacetime with no gravity.

 

[phyzguy]

The answer to your long post #29 is that the universe could work this way, in which there is a universal time which is independent of the observer's state of motion. However, this is not the universe that we live in. In our universe, when the spaceship arrives at Proxima, his clock will only read about 2024.9, not 2026. A vast number of experiments have confirmed the validity of relativity theory. You need to accept that there are things you don't understand and start studying.

 

[bhobba]

It is a paradox, and understood error that the logic of Special Relativity runs up against. Every system of logic will have a paradox that cannot be resolved within it.

Its not a paradox. The only issue is if you can use SR to resolve it or you need the full GR formalism. There is some debate I have seen about it, but the general answer is no - either way its not a paradox.

These days you don't really need Masters level material to do GR - senior undergrad is good enough.

Others likely will not agree with me but I believe you could teach it to senior HS students - but that is a whole thread by itself.

Thanks
Bill

 

[PeterDonis]

I will go and learn the mathematics, but hell guys, please just explain where Tine started to run slower or faster, because I see that the explanations by Physicists is only a description on how light is observed, and not that time dilates?

We can't "explain" your scenario as you give it because you got the numbers wrong. Here is a correct set of numbers for the scenario as you set it up. Just to be clear: the scenario is that a ship leaves Earth when Earth clocks say 2018 and the ship's clock says 2018; it travels at 0.5c relative to Earth until it reaches Proxima; then it turns around and travels back to Earth at 0.5c relative to Earth. For purposes of this scenario, we assume Proxima and Earth are exactly 4 light-years apart in an inertial frame in which they are both at rest.

Here are the correct times given the above:

Departure from Earth
Earth's clock reads 2018.
Spaceship's clock reads 2018.
Earth and spaceship see an image of Proxima's clock reading 2014.
In the Earth/Proxima frame, Proxima's clock reads 2018 and Proxima sees an image of Earth's and spaceship's clock reading 2014.
In the spaceship frame, Proxima's clock reads 2020 and Proxima sees an image of Earth's clock reading 2016 and spaceship's clock reading 2016. Why? Relativity of simultaneity; the event on Proxima's worldline that is simultaneous with the ship leaving Earth is different in the spaceship frame than in the Earth frame.

Arrival at Proxima
Proxima's clock reads 2026.
Spaceship's clock reads 2024.9 (time dilation factor of about 1.15).
Proxima and spaceship see an image of Earth's clock reading 2022.
In the Earth/Proxima frame, Earth's clock reads 2026 and Earth sees an image of Proxima's clock reading 2022 and an image of spaceship's clock reading 2022.62 (because the ship is in transit when this light is emitted, plus time dilation).
In the spaceship frame, Earth's clock reads 2024 and Earth sees an image of Proxima's clock reading 2020 and an image of spaceship's clock reading 2021.46 (again, because the ship is in transit, plus time dilation).

Return to Earth
Earth's clock reads 2034.
Spaceship's clock reads 2031.8 (time dilation).
Earth and spaceship see an image of Proxima's clock reading 2030.
In the Earth/Proxima frame, Proxima's clock reads 2034, and Proxima sees an image of Earth's clock reading 2030 and an image of spaceship's clock reading 2028.52.
In the spaceship frame, Proxima's clock reads 2032, and Proxima sees an image of Earth's clock reading 2028 and an image of spaceship's clock reading 2027.36.

With these correct numbers, it should be obvious how the spaceship "loses time" relative to Earth and Proxima.

 

[jtbell]

[The twin paradox] is a paradox, and understood error that the logic of Special Relativity runs up against.

No. It is an apparent paradox that arises from an incomplete understanding of relativity. There are others, e.g. the “barn and pole paradox”.

In my experience, in nine out of ten cases, the resolution lies in an understanding of the relativity of simultaneity.

 

[russ_watters]

To put a fine point on your frame of mind:

This does not have any evidence and the experiment is incredibly non-based on reality, or I am missing out on the one thing I missed out on my whole life.
Where did time run slower for the traveler?
I don't see it.

There actually is an incredible amount of evidence. Some of the simplest to understand is how the clocks of GPS satellites stay in sync. But you can even put two clocks on different shelves and see a difference in the rate of passage of time between them due to [general] relativity. You can't get much more reality-based than that!

You will need to stop approaching this from a frame of mind of believing it can't be true. It will make learning it more difficult.

 

[phyzguy]

In Post #29, you asked, "what is Relativity, and where do they get this idea that Time runs slower for a traveler? Is there no one that can tell me?". Any book on relativity will answer this, but here is how I would phrase it:

(1) People studied electricity and magnetism for a couple of centuries, culminating in the development of Maxwell's equations in about 1865.
(2) It was noticed that in order for Maxwell's equations to be valid for observers in a state of motion, time and space had to transform in a certain way, which we call the Lorentz Transformations.
(3) Einstein realized that these transformations applied not just to electromagnetic phenomena, but to all phenomena, and elucidated that the consequences included time dilation and length contraction. This was in about 1905.
(4) Since then, a huge number of experiments and observations of many different types have confirmed that this really is the way the universe behaves.

As Feynman said, "This is the way the universe is. If you don't like it, go someplace else!"

I can't resist adding another quote:

"The rotating armatures of every generator and every motor in this age of electricity are steadily proclaiming the truth of the relativity theory to all who have ears to hear,"

Leigh Page, 1941

 

[itfitmewelltoo]

I have been thinking about the theory of General and Special Relativity for most of my life. When I was 16 years old, I...

Let me try this qualitative explanation. If I can get this posting thing right, there is a diagram below. You may have to click the link. There are two frames of reference. Internally, each has exactly the same device, two mirrors with a pulse of light bouncing back and forth. Internally, each experience exactly the same laws of physics. In each, light travels at a speed c.

In the bottom frame, the pulse moves vertically. It takes some finite time t to make the round trip. It has traveled a distance 2d. The moving frame is shown with three positions as it moves. For an observer in the moving reference frame, everything is exactly as it is in the stationary frame. The moving observer does not experience anything unique. As far as she is concerned, the pulse is moving vertically between the two mirrors. The speed of light is exactly the same. It has traveled a distance 2d. And it took time t to travel that distance.

For the stationary observer watching the moving frame things a a bit different. On the left, the pulse leaves the bottom mirror. But, it moves further, at an angle, traveling till it hits the top mirror, then bouncing back to the lower mirror. The pulse has to move a distance of sqrt(dm^2+l'^2). The speed of light is still the speed of light, so for the stationary observer, the pulse has traveled further. It's not like the top mirror gets ahead of the bottom mirror and the light misses it. It does hit it after all, that's what the person in the moving frame sees. It has take more time to get there.

It should be apparent, without any further discussion, that the moving observers time must be slower by comparison made by the stationary observer. After all, the pulse has moved at the same fixed speed. What the moving observer has experienced as being some time t for the pulse to go from mirror to mirror, the stationary observer has experienced some longer time t'. Time has slowed down for the moving observer as seen by the stationary observer. Nothing else can be true. The speed of light is constant in all frames of reference. Something else must give. And what gives is the flow of time.

Now, I apologize. I use to be able to do the math here. I'm afraid that it will take a bit of work to find the path. It isn't all that difficult. It's simply geometry. It has been some 20 years. (I was a bit more motivated then) It's a matter of finding two equations out of it. And what falls out of it are two equations that equate time and distance between the two frames, a transformation so to speak.

 

[PeterDonis]

Moderator's note: I have moved this thread to the relativity forum since it has clearly become a discussion of relativity, not academic guidance.

 

[Sorcerer]

Thank you so much Sir.
And you are correct.
I need to get the mathematical side under my knee, and not just splashing around in this pool.
And believe me, I am doing it as quick as I can.
However, the references you supplied is welcomed and I am sure it will speed up my process.
Susskind is one heck of a good educator, and I watched a few of his lectures, but now that you recommended him, I will definitely take more time on his education.
I remember there are quite a number on his channel on you tube.

Thank you very much indeed.
Bill, you saw my thought experiment made by some MIT graduate on internet, and I think you might be able to see my predicament.
Look at the Twin Paradox as I placed it and please tell me what I am understanding wrong.

I see that Time remains a constant, but it is only the observation of light from 3 reference frames that seems to influence time.
In other words, all the explanations I saw from well established science descriptions is that they are telling me that because we observe, from the Earth (eg.), that a moving object flying away from us we see the light arriving slower at us because of the time light takes to get to Earth from the rocket.

Do you see where I am getting stuck?
Is the theory of Relativity simply a way to determine where a specific object is in space by measuring the arrival of its light in another time frame?

Because if this is what Relativity actually is, then Time dilation does not exist, and length contraction is simply a calculation on the observation of the same object's light leaving its front and rear and arriving at different times at my time frame. So, why all the fuss?

now you see my problem.
After all what I tried to learn, I still do not know what G&SR is, and no one can tell me?

So, what are all the great scientists doing with G&SR?

Still learning like you, but I would ask a question of you:

Do you understand Galileo’s principle of relativity? Look that up if you haven’t heard of it. Do not move forward until you completely understand that concept. 100%. Here is a link with a description.

http://www.physicscentral.com/explore/plus/galilean-relativity.cfm

Then, after that, consider what happens if an observer “at rest” and an observer moving with respect to the at rest observer happen to agree on the speed of a pulse of light. How can they both agree on the speed of that pulse of light if they are moving with respect to each other?If you understand Galileo’s principle of relativity, the notion of an observer at rest and an observer moving with respect to the first agreeing on the speed of anything should give you pause.

And then you can learn special relativity, which explains how both observations (the principle of relativity and the constancy of the speed of light) can be true.KEY POINT

If you get that far you shouldn’t still be having these questions, which means if you THINK you have gotten that far you really haven’t and you should start over.

 

[lekh2003]

Come on gentlemen, don't tell me to go and study the maths.

Niels Bohr once said that if you can't explain something to a toddler, it must not be simplified enough for yourself to understand. I soon came to realize that there is a certain extent to which this applies. One cannot explain general relativity with a simple thought experiment, why would all these members not explain one to you if there was one.

I don't know if you have heard about it, but there was a TV show by National Geographic called "Genius" about Einstein. They had a good episode which mostly explained special relativity. They conveniently skipped the explanations behind general relativity even though it was a significantly bigger part of Einstein's life. Go figure.

I am merely 14. My mathematical understanding stops at around 11th Grade Level. I have given up trying to fully understand the math behind modern physics, because I know I'm going about in the wrong order. I need to have more understanding of the subjects surrounding it before jumping into it. You must go in order, many members have not gone in order and refused to listen to the advice we are giving. Please do listen to us, go in order.

 

[P J Strydom]

If you understand Galileo’s principle of relativity, the notion of an observer at rest and an observer moving with respect to the first agreeing on the speed of anything should give you pause.

Thank you for your reply.
I do know Galileo's principle of relativity very well.
And I am in total agreement with him too.

Now let's take your example to the next level.
1. When Galileo was at rest and he dropped the Ball, he and the fish saw it touching the exact same spot it would do thousands of times if repeated.
2. When the ship accelerated, the ball as well as Galileo gained momentum, and the mass of both moved with the ship.
3. This would mean that if the ball gets dropped it will still touch the same position.
4. and you are correct, the fish will see a triangle movement whereby one can deduct that the Ball actually dropped a few feet further from the original position.

Now we get back to the SR relation to the experiment when we speak about Light in this context.
1. Light travels at C1 irrespective of the speed a ship or rocket are moving at.
2. If a spaceship moves at half a C, it will never push light faster to one and a half C.
The light will still move only at C.
I will post my last picture later today so you can see what scientists are saying.

 

[P J Strydom]

Niels Bohr once said that if you can't explain something to a toddler, it must not be simplified enough for yourself to understand. I soon came to realize that there is a certain extent to which this applies. One cannot explain general relativity with a simple thought experiment, why would all these members not explain one to you if there was one.

I don't know if you have heard about it, but there was a TV show by National Geographic called "Genius" about Einstein. They had a good episode which mostly explained special relativity. They conveniently skipped the explanations behind general relativity even though it was a significantly bigger part of Einstein's life. Go figure.

I am merely 14. My mathematical understanding stops at around 11th Grade Level. I have given up trying to fully understand the math behind modern physics, because I know I'm going about in the wrong order. I need to have more understanding of the subjects surrounding it before jumping into it. You must go in order, many members have not gone in order and refused to listen to the advice we are giving. Please do listen to us, go in order.

And all I want is to tell me what does scientists measure with SR?
When I look at their examples, I find a lot of talk, and no answers.

have you ever thought that perhaps only Einstein knew what he was talking about, and everyone else simply pretend that they know and whenever we ask an explanation, they run to the mathematics.
Anyhow, I still want to know what this mysterious measurement of Special Relativity, Time dilation, Length contraction and mass increase is.

Simple, what are they measuring?

 

[lekh2003]

And all I want is to tell me what does scientists measure with SR?
When I look at their examples, I find a lot of talk, and no answers.

have you ever thought that perhaps only Einstein knew what he was talking about, and everyone else simply pretend that they know and whenever we ask an explanation, they run to the mathematics.
Anyhow, I still want to know what this mysterious measurement of Special Relativity, Time dilation, Length contraction and mass increase is.

Simple, what are they measuring?

They are measuring all the things you just listed. There is no conspiracy that no one knows special relativity except Einstein. It's just that this stuff is so complex that it requires prior knowledge otherwise it would taint your assumptions of the subjects.

 

[P J Strydom]

In Post #29, you asked, "what is Relativity, and where do they get this idea that Time runs slower for a traveler? Is there no one that can tell me?". Any book on relativity will answer this, but here is how I would phrase it:

(1) People studied electricity and magnetism for a couple of centuries, culminating in the development of Maxwell's equations in about 1865.
(2) It was noticed that in order for Maxwell's equations to be valid for observers in a state of motion, time and space had to transform in a certain way, which we call the Lorentz Transformations.
(3) Einstein realized that these transformations applied not just to electromagnetic phenomena, but to all phenomena, and elucidated that the consequences included time dilation and length contraction. This was in about 1905.
(4) Since then, a huge number of experiments and observations of many different types have confirmed that this really is the way the universe behaves.

As Feynman said, "This is the way the universe is. If you don't like it, go someplace else!"

I can't resist adding another quote:

"The rotating armatures of every generator and every motor in this age of electricity are steadily proclaiming the truth of the relativity theory to all who have ears to hear,"

Leigh Page, 1941

And the experiments does not take into account that the further away matter from the source of gravity, the slower the Radio decay.
and I read everything about satellites and how Einsteins theories are keeping them on track too.
Yet, what it is keeping track of is not explained.
Do you think that an equation entered into the satellite's computers is working out exactly where the triangulation of 3 satellites pinpoints a true position on earth?
No, in this regard Galileo's relativity is 100% correct.
However, can you tell me what you measure with Einsteins theory?

 

[P J Strydom]

They are measuring all the things you just listed. There is no conspiracy that no one knows special relativity except Einstein. It's just that this stuff is so complex that it requires prior knowledge otherwise it would taint your assumptions of the subjects.

Realy?
So are you saying that what I calculated with Gallilean relativity is correct?
Or do you say what I calculated is incorrect.
If incorrect, show me where?
Was it the time on Earth, the space ship, or ProxC that I calculated incorrectly.
Why do I get the feeling no one can answer me?

 

[lekh2003]

And the experiments does not take into account that the further away matter from the source of gravity, the slower the Radio decay.
and I read everything about satellites and how Einsteins theories are keeping them on track too.
Yet, what it is keeping track of is not explained.
Do you think that an equation entered into the satellite's computers is working out exactly where the triangulation of 3 satellites pinpoints a true position on earth?
No, in this regard Galileo's relativity is 100% correct.
However, can you tell me what you measure with Einsteins theory?

Einstein's theory doesn't measure things like a ruler. It uses different equations with Einstein derived to make sure the satellites are running on the same time and are aware of their positions. When orbitting the Earth at high speeds, relativity comes into play. It's not really an equation, but an idea which has been represented mathematically like every other concept in physics.

 

[P J Strydom]

Moderator's note: I have moved this thread to the relativity forum since it has clearly become a discussion of relativity, not academic guidance.

I do thank you for the promotion sir.
Do you think our fellow Members realizes that I am playing Devils Advocate?
I want to see if they understand GR&SR, and will pest them for a while.

 

[lekh2003]

Realy?
So are you saying that what I calculated with Gallilean relativity is correct?
Or do you say what I calculated is incorrect.
If incorrect, show me where?
Was it the time on Earth, the space ship, or ProxC that I calculated incorrectly.
Why do I get the feeling no one can answer me?

You get the feeling you can't be answered because you have approached us with that kind of attitude. I can't help you with your problem, but I can help you understand that you need to learn more before approaching the problem.

 

[Ibix]

And all I want is to tell me what does scientists measure with SR?

Nuclear power plants and weapons cannot be explained without it. Particle accelerators such as CERN likewise (there's a nice video of Bertozzi demonstrating the relativistic energy/velocity relation that you can find on YouTube). For that matter, electromagnetism is a relativistic field theory, so radios and mobile phones. The GPS uses general relativity.

 

[P J Strydom]

Einstein's theory doesn't measure things like a ruler. It uses different equations with Einstein derived to make sure the satellites are running on the same time and are aware of their positions. When orbitting the Earth at high speeds, relativity comes into play. It's not really an equation, but an idea which has been represented mathematically like every other concept in physics.

Now you are confusing me.
Do you say something traveling at 14 000 Km per hour in relation to the Earth needs Special relativity, and not Galilean relativity?
300 000 Km per second, 1 080 000 000 Km per Hour is the speed of light.
this versus 14 000 Km per second?
1.296% of SOL.
this over a measurable distance of 20 000 Km altitude.
Do you know what a negligible adjustment this makes on positioning.
So, now that you know how SR are used in GPS, please explain to me exactly where they are doing an adjustment?
Where between the Satellites and the Earth does Time dilute.

 

[lekh2003]

Now you are confusing me.
Do you say something traveling at 14 000 Km per hour in relation to the Earth needs Special relativity, and not Galilean relativity?
300 000 Km per second, 1 080 000 000 Km per Hour is the speed of light.
this versus 14 000 Km per second?
1.296% of SOL.
this over a measurable distance of 20 000 Km altitude.
Do you know what a negligible adjustment this makes on positioning.
So, now that you know how SR are used in GPS, please explain to me exactly where they are doing an adjustment?
Where between the Satellites and the Earth does Time dilute.

You are now counter confusing me.

 

[P J Strydom]

Nuclear power plants and weapons cannot be explained without it. Particle accelerators such as CERN likewise (there's a nice video of Bertozzi demonstrating the relativistic energy/velocity relation that you can find on YouTube). For that matter, electromagnetism is a relativistic field theory, so radios and mobile phones. The GPS uses general relativity.

So, now you claim that GPS' uses general relativity, and not Special Relativity?

GPS satellites travel at approximately 8,700 mph (14,000 km/h) with respect to Earth. This means time runs 7,200 nanoseconds per day slower for a satellite relative to us on Earth as described by Special Relativity.

http://www.physics.org/article-questions.asp?id=77

Lets us continue with exactly what we can measure with SR and GR.
gentlemen, If you don't know, say so.
However, show me on scientists very own Thought Experiment where I am wrong.

 

[weirdoguy]

So, now you claim that GPS' uses general relativity, and not Special Relativity?

Both. Besides, SR is built in GR.

Why do I get the feeling no one can answer me?

Because you are unwilling to learn, and want to stay with your incorrect premises. At least that's what it looks like for me, an external observer. Especially when you write something like this:

Come on gentlemen, don't tell me to go and study the maths.

because studying textbooks that uses maths is the only way to learn and understand physics.

 

[Ibix]

So, now you claim that GPS' uses general relativity, and not Special Relativity?http://www.physics.org/article-questions.asp?id=77

Read the very next paragraph after the one you quoted.

 

[P J Strydom]

Read the very next paragraph after the one you quoted.

Nice of you to investigate the sources I quote.
Do you know how many people would not even have bothered?

The article reads: "GPS satellites travel at approximately 8,700 mph (14,000 km/h) with respect to Earth. This means time runs 7,200 nanoseconds per day slower for a satellite relative to us on Earth as described by Special Relativity.

However, using General Relativity it is possible to calculate that time goes faster for a GPS satellite by 45,900 nanoseconds per day, due to the satellite being 19,000km above the Earth (therefore in weaker gravity). This means overall time runs 38,700 (45,900 – 7,200) nanoseconds faster per day for a GPS satellite relative to us stationary on Earth."

1. As Special relativity describes, time runs slower for the Satellite, than what Time runs on the earth.
2. But according to General Relativity, Time on the Satellite runs Faster.

We will come back to this statement.

 

[Ibix]

Nice of you to investigate the sources I quote.

Do you know how many people would not even have bothered?

The problem is that you didn’t bother to read the source you cited. You need to read carefully if you are going to understand.

1. As Special relativity describes, time runs slower for the Satellite, than what Time runs on the earth.
2. But according to General Relativity, Time on the Satellite runs Faster.

That's not what it's saying. It's saying that you can decompose the time dilation into an effect due to speed relative to a hovering observer and an effect due to height. The effects are opposite. The effect due to speed can be handled using SR (or GR, giving the same result from more complicated maths). The effect due to height needs the full theory of GR to explain.

We will come back to this statement.

No point. You just misunderstood what was written. Please note that, as has been pointed out several times, the sooner you accept that the problems are in your understanding of relativity, not in relativity, the sooner you will start to learn.

Relativity might not be a perfectly accurate model of reality, but it is not inconsistent with itself. Any logical problems you find are in your conception of relativity, not in relativity itself.

 

[phinds]

Do you think our fellow Members realizes that I am playing Devil's Advocate?

No, because you are not playing Devil's Advocate, you are simply spouting over and over the same misunderstandings. A Devil's Advocate tries to use a valid argument, just one that is counter to the one being advocated against. Your arguments are not valid.

I want to see if they understand GR&SR, and will pest them for a while.

By proving over and over that you do not understand SR and GR? That's hardly a test of the members here, it simply a demonstration of your lack of understanding.

 

[jbriggs444]

Do you think our fellow Members realizes that I am playing Devils Advocate?
I want to see if they understand GR&SR, and will pest them for a while.

If you pretend to be a jerk, you are not pretending.