relativity

[tyflem]

If a person is on a spaceship and is traveling close to the speed of light, time is moving slower for the person in the spaceship relative to the person on earth. So does the person on the spaceship actually age slower, for example would his hair be shorter than the person on earth?

[HallsofIvy]

If a person is on a spaceship and is traveling close to the speed of light, time is moving slower for the person in the spaceship relative to the person on earth. So does the person on the spaceship actually age slower, for example would his hair be shorter than the person on earth?
As observed by a person on earth, yes. Of course, people on the space ship would see no difference. In fact, if they observed the people on the earth they would see time moving slower for them.

[50cobra302]

how about somone looking in a mirror aboard a spaceship traveling the speed if light? would he see anything? (assuming we could reach 100% speed of light, 99.999999% is only plausible.)

[Epsilon=One]

how about somone looking in a mirror aboard a spaceship traveling the speed if light? would he see anything?It's all relative. The point of relativity is that the frame of reference for any motion is relative, thus unique, for every observer that is at a different point of observation.

Regarding a third point, if the points of observation are in motion and are not congruent (vary in location) with one another, or with the third point, there will be a dimensional difference regarding all the involved locational dimensions which includes time.

Of course, it must be considered that a dimensionless point can have no motion; and thus, no existence.

[HallsofIvy]

how about somone looking in a mirror aboard a spaceship traveling the speed if light? would he see anything? (assuming we could reach 100% speed of light, 99.999999% is only plausible.)

First, you can't just say "traveling the speed of light". Traveling at the speed of light RELATIVE TO WHAT? In any case, the person and the mirror would be traveling at the same speed relative to whatever frame of reference so would be still relative to each other. Light would still travel from the person to the mirror and back again AT THE SPEED OF LIGHT (c). It is a basic point of relativity that light travels at the same speed relative to ANY frame of reference.

[Mr. Robin Parsons]

First, you can't just say "traveling the speed of light". Traveling at the speed of light RELATIVE TO WHAT? In any case, the person and the mirror would be traveling at the same speed relative to whatever frame of reference so would be still relative to each other. Light would still travel from the person to the mirror and back again AT THE SPEED OF LIGHT (c). It is a basic point of relativity that light travels at the same speed relative to ANY frame of reference.
© Mr. Robin Parsons :cool: Kingston Ontario Canada MMVII

Nice answer, yet it poses a rather simple dilema....if a spacecraft is travelling at c relative to passing by a psuedo stationary planet, someone aboard looks into a mirror and shines a flashlight into/at it, in the same direction of travel as the spacecraft itself, then that light must be going 2c relative to the stationary planets' frame of reference......right?

If a person was standing on the face of that planet, looking towards that craft through a telescope that tracked the crafts at it's speed, and then observed through a very large portal that showed the Person with the flashlight, saw the flashlight lighting up, what would they observe? :eek:


(Aren't (I) a Fun Guy....hee hee hee)

[HallsofIvy]

© Mr. Robin Parsons :cool: Kingston Ontario Canada MMVII

Nice answer, yet it poses a rather simple dilema....if a spacecraft is travelling at c relative to passing by a psuedo stationary planet, someone aboard looks into a mirror and shines a flashlight into/at it, in the same direction of travel as the spacecraft itself, then that light must be going 2c relative to the stationary planets' frame of reference......right?
Wrong. If B is moving at speed v relative to A and C is moving at speed u relative to B then A's speed relative to C is given by (u+ v)/(1+ uv/c^2). In the case that u= c this becomes (c+ v)/(1+ cv/c^2)= (c+ v)/(1+ v/c). Multiplying both numerator and denominator by c this is c(c+v)/(c+v)= c.
The speed of light in vacuum is c relative to ANY frame of reference.

If a person was standing on the face of that planet, looking towards that craft through a telescope that tracked the crafts at it's speed, and then observed through a very large portal that showed the Person with the flashlight, saw the flashlight lighting up, what would they observe? :eek:


(Aren't (I) a Fun Guy....hee hee hee)
The observer would see the light from the flashlight coming toward him at the c of course. He could also compute, using the Lorenze contraction formulae, that, from the point of view of the person in spaceship, the light was leaving the space ship at c.

[Mr. Robin Parsons]

© Mr. Robin Parsons :cool: Kingston Ontario Canada MMVII

Wrong. If A is moving at speed v relative to B and C is moving at speed u relative to B then A's speed relative to C is given by (u+ v)/(1+ uv/c^2).

In the case that u= c this becomes (c+ v)/(1+ cv/c^2)= (c+ v)/(1+ v/c).
Multiplying both numerator and denominator by c this is c(c+v)/(c+v)= c.
The speed of light in vacuum is c relative to ANY frame of reference.
Nice answer, but......

Simple problem? you are finding A's speed relative to C, we want C's Speed relative to B

.....because we already know that C's speed relative to A ......is c.

Should you try again?

(after all ...you are good at it) :cool:

[Mr. Robin Parsons]

© Mr. Robin Parsons :cool: Kingston Ontario Canada MMVII

Just for clarity, C (the flashlight) is stationary relative to A, but it is not the speed of C 'persay' that we are looking for, it is the speed of the Light eminating from C relative to B, (that A is approaching at c speed) that we are looking for.....

All to easy to simply add the equations together and get 2c...Right?

Oh Yes, Pardon my humor? :eek:

[HallsofIvy]

I realized that I had made a typo and corrected it.

The fundamental rule in relativity is that the light travels at the same speed relative to ANY frame of reference- that is necessary so that Maxwell's equations for electro-magnetic fields do not lead to contradictions. This is contrary to classical physics.

Suppose you are standing at the side of a road with a catcher's mitt. A flat bed truck comes along, at 50 miles per hour (relative to the road and you). I am standing on the flat bed and a throw a baseball to you. I throw the base ball at 50 miles per hour, relative to myself and the flatbed truck. How fast is the baseball going relative to you?

Classical physics says you add the speeds: 50 + 50= 100 mph. The ball would be coming at you at 100 mph (making me a major league pitcher!).

Relativity would use a slightly different formula: (50+ 50)/(1+ (50)(50)/c^2)= 100/(1+ 2500/c^2). Since c is about 186000 mph, 2500/c^2 is about 0.00000007. According to relativity, the baseball would be moving, relative to you at about 100/(1.00000007) = 99.99999 mph. Okay, 50 mph is a "non-relativistic" speed. The difference between classical and relativistic theories is too small to measure. But if one of the speeds is c, no matter what the other we have, as I said before, (v+ c)/(1+ vc/c^2)= (v+ c)/(1+ v/c) and, multiplying both numerator and denominator by c, that becomes c(v+c)/(c+ v)= c. If I am moving at 99% the speed of light relative to you, and I aim a flash light directly in front of me, I see the light moving at c, relative to me, and you see the light moving at c relative to you.

I will admit I'm not sure how much of what you are saying is intended as "humor" but I would suggest that you try not to confuse people who may not understand relativity as well as you do.

[Mr. Robin Parsons]

© Mr. Robin Parsons :cool: Kingston Ontario Canada MMVII

I realized that I had made a typo and corrected it.Sorry, but now you have Lost me... :eek:

Lets go this way....

The Planet is Now A

The spaceship, approaching A at c speed, is B

The light eminating from the flashlight (@ c speed) on the spaceship, is C

Now, want C's speed relative to A = :cool:

Does it still work? :confused:

[Mr. Robin Parsons]

© Mr. Robin Parsons :cool: Kingston Ontario Canada MMVII

BTW just for fun, instead of a flashlight, lets try ...it is the Mommy Ship and it launches a Baby ship that, relative to Mom, goes off from Mom @ light speed, (c) towards the planet that 'Mom' is approaching, the Home planet, also @ Light speed. (c)

How fast is 'Baby' going relative to the Home boys?

[Mr. Robin Parsons]

© Mr. Robin Parsons :cool: Kingston Ontario Canada MMVII

BTW just in case you would like to tell me about "matter cannot be accelerated to the speed of light" try reading this one (physicsmathforums.com/showpost.php?p=5267&postcount=50) first please.

(In these forums)

[Mr. Robin Parsons]

© Mr. Robin Parsons Kingston Ontario Canada MMVII

Wrong. If B is moving at speed v relative to A and C is moving at speed u relative to B then A's speed relative to C is given by (u+ v)/(1+ uv/c^2). In the case that u= c this becomes (c+ v)/(1+ cv/c^2)= (c+ v)/(1+ v/c). Multiplying both numerator and denominator by c this is c(c+v)/(c+v)= c.

You can keep repeating this:
The speed of light in vacuum is c relative to ANY frame of reference.
....as much as you want, Stand Alone, it is not a proof.

Aside from that, is there experimentation that proves you math is Viable as opposed to suitable mathematical conjecture?


BTW what we want is NOT A's speed relative to C, we want C's speed relative to A, as C is aboard B travelling towards A....

That is why (I) re-rwrote the explainations, as you hadn't defined A B + C.

Aside from that, (as well) you seemed to {edit}Have{/edit} neglected that v = c as well in your equations and result.

Sooooo, try again..?

(Or Am (I) somehow wrong again, as (I) know (I) can be sometimes :eek: )

[Mr. Robin Parsons]

© Mr. Robin Parsons Kingston Ontario Canada MMVII

(SNIP) Aside from that, (as well) you seemed to {edit}Have{/edit} neglected that v = c as well in your equations and result. :eek: (SNoP)

That makes it (c+c)(1+c^2/C^2) ='s 2c right? {EDIT} see post #17 {/EDIT}

So if the 'Mom' (Mother) Ship send a signal towards home, while travelling towards home at c speed, then the signal should get to Home before Mom does.....If your at Alpha 'Proxima' (Alpha = the first or beginning Proxima = Close/near/nearby) four light years distant, flying back towards earth, send an EMR signal from your ship which is flying at c speed towards earth Don't Say: "Hi, Can you hear me?" :eek: :D :p

If you send a signal in that manner, then you will get an answer (if they to can return their signal with that kind of acceleration to it) in three years!

To lightspeed! and B-E-Y-O-N-D!!

Hey! we can put it on a Tee shirt "A + B = 2c" :D :cool:

Real Quick!


(P.S. Did (I) get the math right? cause nevermind spell-check, (I) need {a} Math Checker!)

[Mr. Robin Parsons]

© Mr. Robin Parsons Kingston Ontario Canada MMVII

(SNIP) If you send a signal in that manner, then you will get an answer (if they to can return their signal with that kind of acceleration to it) in three years! (SNoP)

Oooops that is wrong because of what is highlighted in red, take away that 'condition' and it is right!

But it certainly proves this part right!

(SNIP) (P.S. Did (I) get the math right? cause nevermind spell-check, (I) need {a} Math Checker!) (SNoP)

Oh Yes, (I) sorta do have 'math checkers' as (I) was made :o away :o {EDIT}aware{/EDIT} of what (I) already knew yet had not factored in properly, about 15-20 minutes ago, just that (I) couldn't get onto a computer to fix it....they were 'in use' by 'others'......and they wonder why (I) would complain about my treatment.

My 'Reputation/Renown' is one the line....sorta ALWAYS!

[Mr. Robin Parsons]

© Mr. Robin Parsons :cool: Kingston Ontario Canada MMVII

(SNIP) That makes it (c+c)(1+c^2/c^2) ='s 2c right? (SNoP)

Good thing (I) asked if that was right, cause it isn't!!

The answer there is 4c as it is (c+c)(1+c^2/c^2) ='s (2c)(1 + 1) ='s (2c)(2)='s 4c

OYE!! :o :( needs a math checker, then again how come no one else noticed it??

[Mr. Robin Parsons]

© Mr. Robin Parsons :cool: Kingston Ontario Canada MMVII

HallofIvy (I) see that you are still a mentor at physicsforums...have you told them about this speed of light thing? Lorenz well expansion :eek: :rolleyes:

(if the math is done right, right?)

Oh yes, (I) am, none the less, gratefull as you were (AFAIK/Recall) the first one to "show me the math" and (Especially important) how it was used.

As you haven't commented (further) can (I) simply assume you agree? :eek:

[Mr. Robin Parsons]

© Mr. Robin Parsons :cool: Kingston Ontario Canada MMVII

(SNIP) As you haven't commented (further) can (I) simply assume you agree? :eek: (SNoP) How is it "Fog Horn Leg Horn" says it?

"Answer me (whatever)"

(no (I) don't want to use that word here that way)

Will ya?

That Phi'sics forums thing doesn't bother me, (I) had suspected it was you cause it felt the same as when from there, soooooo...........(huh?)

[Epsilon=One]

The fundamental rule in relativity is that the light travels at the same speed relative to ANY frame of reference- that is necessary so that Maxwell's equations for electro-magnetic fields do not lead to contradictions. This is contrary to classical physics.
...

If I am moving at 99% the speed of light relative to you, and I aim a flash light directly in front of me, I see the light moving at c, relative to me, and you see the light moving at c relative to you.

I will admit I'm not sure how much of what you are saying is intended as "humor" but I would suggest that you try not to confuse people who may not understand relativity as well as you do.Finally.

Some sanity in this thread.

And, "humor" and confusion, so often encountered with histrionics has no place in this forum.

[Mr. Robin Parsons]

© Mr. Robin Parsons :cool: Kingston Ontario Canada MMVII

Moderator this is a report of abuse, and attempted/furthered abuse by the above poster.

Could you please explain to it that (I) cannot see what they write and therefore their posting constitute nothing less (& Certainly nothing more) then acts of antagonism.

Thank you. :cool:

[Epsilon=One]

Moderator this is a report of abuse, and attempted/furthered abuse by the above poster.An excellent example of said stated complaint can be found in every signature line of Mr. Robin Parsons, the complainer.

Could you please explain to it that (I) cannot see what they write...It would appear that this is another of your misstatements as there would be no cause for your complaints if you were being truthful.

The topic of this thread is relativity. Do you have any disagreement with my comments concerning relativity?

[Mr. Robin Parsons]

© Mr. Robin Parsons :cool: Kingston Ontario Canada MMVII

was asking 'HallsofIvy' to answer .....figures..... the 'Jerk to be ignored NOW!' responds instead.

GO AWAY JERK!

[HallsofIvy]

Ah, but I just love watching you two go at each other!

[Epsilon=One]

was asking 'HallsofIvy' to answer .....figures..... the 'Jerk to be ignored NOW!' responds instead.I don't believe that in an open dialogue that searches for truth that there is any limit as to who responds other than that the reply can add some insight.

You might consider the above thought; as so often, your replies add little but an insight into ill manners, confusion and obfuscation.

[Epsilon=One]

Ah, but I just love watching you two go at each other!Thank you.

It's nice to know that such an endless task, with such small reward, can bring some occasional enjoyment.

Though, I do have some doubt as to whether many other members can possibly understand your position . . .

[Mr. Robin Parsons]

Ah, but I just love watching you two go at each other! (Jealous?? :p )

© Mr. Robin Parsons :cool: Kingston Ontario Canada MMVII

Nothing new, he's hit it in four separate places.

Instigator & Antagonist nothing else, nothing new.


But (I) cannot see what he is typing, so it is Amazingly UNFAIR!! especially for a Moderator, ultra especially!!

[Allondell]

General relativity is a theory of gravitation developed by Einstein in the years 1907–1915. The development of general relativity began with the equivalence principle. The relation is specified by the Einstein field equations, a system of partial differential equations.

[orten999]

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