Are laws of nature really the same in all reference frames?

zonde

We don't know the speed. We measure speed i.e we make some observations and then come up with some number.
Two observers will come up with different numbers from their respective observations. Just because these numbers are different doesn't mean that they live in different worlds. It just means that they use different units for their measurements. In particular case it is time unit that is different.

Bjarne

If speed is different for the 2 observers, - classic laws of gravity would not (as I see it) be the same. - I mean how could these?

Or the gravity of the galaxy would not be the same for the 2 observers. That too would sound absurd.

What should possible cause two different speed, or different influence of gravity?

darkhorror

Lets say we are both on earth. I decide that a foot is 24 inches. You come along and ask for 2 feet of lumber. I cut to me what is 2 feet of lumber. Now to you a foot is 12 inches. You measure the lumber i just cut(with a foot being 12 inches), and you tell me it's too long and that it's 4 feet. I say no it's clearly 2 feet. Is the lumber really 4 feet and 2 feet at the same time? Yes it just depends on which foot measurement you use.

That isn't really a good example but it might help you see the point people are trying to make.

Bjarne

So what you are saying is; if observer A and B would compare their meter sticks, the size must be different and therefore they also measure different distance?

So when time shrink, the meter stick extend?
And this explains that the math is correctm, - for both, - when 1 orbit of the MilkyWay is completed?

JordanL

Ah, alright. I just went back and reread how this thread began:

Bjarne: The answer is yes, the laws of nature would be found the same in all reference frames. However, the measurements taken of your surroundings, and thus your inputs into your equations, would be different. Because the measurement is different, your receive a different answer for your reference frame. However, because of your different reference frame, you received the right answer for you.

That was actually the point of the idea... that we had spent hundreds of years making equations and laws that only worked for Earth and our reference frame. GR and SR together were a set of rules that would give the right answer even if your measurements turned out different.

Bjarne

Try to be more exact.
We can very simple multiply speed and time and get the result = distance

Why can a "stranger" living in a different space-time (caused by GR) - according to the mentioned example, not do the exact same as we can ?

Why seems reality to be limit to a certain place on Earth. ?

WHAT exactly should a observer that not shares our time-rate then exactly do if he also want to make such speed * time calculations. ?

How are the rules for him?

Shall he just pretend he is moving faster as us, even though there are absolutely no reason to believe so ?

Is his meter sticks really longer than ours and distance therefore shorter for him?

WHAT exactly would you tell him?.

I mean not only words, but how are the rules / law exactly according to the examples I have mentioned?

How can such relative huge dilemma have surveyed in 100 years without anyone have wonder; what happens here?

I believe we have no clue how to explain that, right ?

This could be a bad sign.

russ_watters

The rules for another observer are exactly the same as for us. No pretending needed and no issue of who's measurement is "really" right - the whole point of Relativity is that both measurements are right.

Bjarne

According to last the mentioned exsample;

• We know observer B’s clock is "losing" 6 earth-years relative to A’s clock. after one Milkyway orbit,
• We also know that both clocks’ orbits the milkyway (MW) the same radius from the center of the MW.
• And we know that both clocks complete an orbit of the MW in the same period.
• Both clocks follows the Sun, - The only difference that counts is that B is closer to the Sun as A is , hence B is stronger affected by gravity from the Sun as A, - ( none of the clocks are orbiting the Sun, and none on board of a planet).

Questions

1. So is the speed of observer B the same as the speed of A( 250 km/s) ?
2. Does both observer A and B agree the speed is the same ?
3. Are A's and B's meter-stick comparable the same ?
4. Will both observer A and B agree about how long the circumstance of the Milkyway is ?
5. If both observer A and B agree that speed and distance is the same for both (but the time rate not) , how can it be that speed multiplied with time not would show the same result for observer B as it would for observer A ?

It seems to be that we say that our reality is more real than these”out there”
I mean this is also how science was in the Middle Ages, - something must have change since.
I am not satisfied with words, but to know WHAT exactly is going on here.

darkhorror

You are getting caught up in time, speeds, distances being absolute. You have to do the calculations with respect to each "observer." So you say you are moving at 250k/s you have to ask with respect to what. In your own frame of reference you aren't moving at all. In the earths you are moving at one speed, sun another,...

russ_watters

As you must know, this question is incomplete. Speed is measured between two points and you've only listed one point for each of the two speeds you are looking for. You need to specify what you are measuring the speeds relative to and who is doing the measuring. Don't bother fixing this question, though - I'm not interested in playing games with made-up/impossible numbers and it really isn't important to your original point. Maybe. But again, this isn't really all that important. What is important is this:

If both observers faithfully follow the principle of Relativity as stated in your title and, as it requires, ensure they are clear and consistent about what frames of reference they are doing the measurements from, or measure from one and properly transform to the other, they will agree on what is happening. Again: If they follow the principle of Relativity and are clear on the choices of reference frames (and the definition of a "meter") they most certainly will. They might say: "From here, your meter looks smaller than mine, but since I know our relative speeds, I calculate that if I was to go over to you and measure your meter it would be the same as mine." Same answer as above. The wording of the question violates Relativity by mixing and matching observations from different reference frames without properly accounting for the differences. So we can answer this way: if A and B don't properly apply the principle of relativity, they may not believe that the laws of the universe are the same in all reference frames. Or put another way: if a person doesn't understand how to use a law, they will misuse it and may assume that the law is wrong when, in fact, it was just their use of the law that was wrong. That appears to be the basis of your issues with Relativity.

Bjarne

We have “two point”...
We have a orbit and thereby a circumstance of the milkyway (MW).
You can bend the orbit to a straight line.
So you do have “two points”.
A staring point that also is the final point when the orbit is completed.

This is done too.
The Sun travels relative to a points of no motion, which is the center of the Milkyway.
The 2 clocks are according to the example mentioned above following the exact same orbit as the Sun.

First at all notice we are only speaking about influence due to gravity (GR) not about SR
The orbits of the 2 clock’s are exactly the same (for all observers).
Observer A and B are doing the measurement from their own reference frame.
B's clock is really ticking slower as A's clock - because B is closer to the Sun as A and therefore comparable slower as A's clock.

Nothing prevent that A and B can compare time differences.
Think about; how do we determinate how long 1 meter is or what the speed of light.
Both obersver A and B would determinate that the exact same way, wouldn’t they?

If A's meter-stick is comparable shorter as B's it will not only "look" shorter.
B's reality is real, as well as A's (or our) reality also are real.
Therefore B's meter stick will really be shorter.
We are not speaking about "illusion" but about realities.

Now you are speaking SR
Both A and B is according to the example in the same SR-reference frame, since both exactly follows the motion of the Sun, hence SR do not apply, - only GR does.

Let me ask more simple and all-round.
Imaging you was orbiting the Sun with a meter stick 50 billion km from the Sun.
I was orbiting 150 billion km from the Sun also carry a meter stick.
Would both meter sticks comparable be the same length? .
What I am asking is 1 meter the exact same length if a observer far away ( not affected by gravity of the Sun) could se both meter stick and also was able to compare if our meter stick did have the exact same length, so long we are different places in the gravitational field of the Sun ?

Now let say that time in your orbit is 1 billion part slower for you, compared to my time rate.
Would your meter stick then proportional to that be 1 billion-part longer ? (or shorter ) – or exactly the same as mine, - still seen from a observer C far away and not affected by the gravity of the Sun.

Comparing relative differences, doesn’t matter whether we speak about time rate, speed or length, - is not necessary mixing these, and this is also not what I have done at all.

I am not mixing anything but asking what is the speed and [B]distance /B] difference between A’s and B’s reality according to the example, - if any ?
There must be a very simple answer to that question.

If you would say there is no difference between the reality of A and B (accept time), simple math would show you a mathematical contradiction, since time multiplied with speed can impossible result to the same distance for A and B. (since time for B is shorter)

So I am in fact trying to separate relative differences.

Mathematical either speed or distance cannot comparable be the same.
So what is the mathematical answer here?
Is speed comparable larger - or is it distance that is proportional and comparable shorter (and therefore the meter -stick propositional longer) ?

If nothing proves that (comparable) speed is affected (and hence comparable different), and you multiply less time (for B) with the same (comparable ) speed that is valid for A, - you will get a shorter distances for B.

So if you have no objection that we assume that speed is (comparable) the same for A and B, - then it is mathematical proven that distance (circumstance of the MW) for A and B NOT is comparable the same for A.

If you do not agree speed is comparable the same, what is the correct comparable speed for B, ?.

Yours assumption that I am mixing realities is not true. – I am ONLY comparing realities, and do in fact try to keep factors separated, by asking what the differences except time .

Is speed and / or distance comparable different according to the very simple example mentioned?

Please try to keep it simple.

Bjarne

No both clocks are moving 250 km/s as well as the Sun
Both clocks’ follows the Sun
SR does not apply to the mentioned scenario.
So this is not the correct answer either.

darkhorror

250 km/s with respect to what?

Bjarne

I geusss the same way how we measure speed in space.
That must be valid for us but also for an observer with a slow ticking clock.

darkhorror

The way we measure speed in space is we see how fast we are going with respect to something else. If I am in space with respect to me my velocity is 0. With respect to the earth it might be .5c. With respect to something else it might be 250km/s.

Saying something is moving 250km/s is meaningless unless you say what it is with respect to.

zaybu

A consequence of Relativity is that we seek laws that are Lorentz invariant: meaning, if we have an equation A = BC + D in one frame of reference, then using the lorentz transformation laws to another frame of reference, we get A' = B'C' + D'. Note that not all equations will have this property, and certainly not certain observables. That's why we have time dilation, length contraction or that if two events are simultaneous in one frame, they might not be silmutaneous in a different frame. Now there are constants that are taken to be the same in every frame, that is, Lorentz invariant, notably the speed of light c, Planck's constant h-bar, and G -- Newton's constant in his law of universal gravitation.

Hope this helps.

Bjarne

250 km/s is the speed of the Sun's motion orbiting the MW
I don’t know how they did that measurement.
It is not with respect to “something” I believe, - but only to the center of the MW, where you have relative no motion.
If we can do such measurement, other observers in the Solar system can also. But I am not sure the result for a different space-time observer would be the same.