Why can't we travel faster than light?
#1
I have never been able to understand this portion:

http://en.wikipedia.org/wiki/Speed_of_li..._on_speeds

This is so much contradicting to my beliefs :p


Well, seriously.... Why can't we travel faster than light again?
(because in my thought experiments I can)
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#2
(10-May-2010, 07:11 PM)shobhitg Wrote: I have never been able to understand this portion:

http://en.wikipedia.org/wiki/Speed_of_li..._on_speeds

This is so much contradicting to my beliefs :p


Well, seriously.... Why can't we travel faster than light again?
(because in my thought experiments I can)

This website does a wonderful job of explaining relativity. I'm still reading it, but this is what I understand on the speed of light:

It is an inherent property of our Universe and to make the speed of light same for all observers, the Universe varies time for different observers.

(That site also has a beautiful and simple proof for the equation E=mc2)
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#3
Thanks Lije for the link, I am already finding it very useful while reading and understanding it.

I think I will get it once I am done reading (and understanding) everything on that website.
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#4
This is impossible we can not go faster then light.
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#5
The reason why one can't faster then light is not answerable, All the laws which explain it uses the limit as "c" Hence if u change the value of c, the corresponding equation changes too.

A classical way to example is time collapse, Now lets think u and a light beam are having a race, but the thing is u're racing the first beam that was created by the universe, during the Big bang. To explain why u can't travel faster than light U have to go with an alternate theory showing that u travel faster than light, and look into what happens to the theory.

Now back to the race, lets say u travel at 2 times the speed of light (Your some superman, u don't age and u can't die either) so if the universe is a billion yrs old, and the first beam that moves is actually the beam that marks the imaginary boundary of the universe, don't worry u'll move past it in another 500 milllion yrs :P

after 500 million yrs...

Your still moving but u haven't caught up with it? Why? The answer is simple the beam is not stationary, its moving too! according to u the light beam must be at a stand still, since ur moving faster than that beam, but thats not how it works, relative to whosoever, no other bodies speed changes, if a car moving ahead of u is at 80kmph, and u move at 160kmph, If u measure the speed of the car relative to u, it'll be still 80kmph, so lets say u need another 200 million yrs to over come it smile

After 200 million yrs...

U look at the beam finally ur at par with it, for a moment u observer it and wallah! u see the birth of the universe! fascinating isn't it? wait! whts this there's someone gaining on u! its 3 times faster than light speed, and now its observing u, wht he see's is not the beginning of the universe but u're journey! so does that mean if u over come the speed of light u can change history itself? U create a new boundary and u become the history even though u were born way after the first beam was created, U actually changed space time continuum!

But the universe doesn't work that way, here's what actually happens according to the modern theory, First if u gain speed, the factors around u will change. Lets say, ur moving at 0.8c, The fact is the things around u look different, u see a man shaving so slow that u can have a bath at that time like in the movie "Wanted" where the stuff happens in slow mo! But u still take 20 mins to bath, where the other guy who's slower than u take what seems to be an hour or more...

Whts going on? Its simple, the universe adapts towards u! u're in relative with the universe, ur mass increases and time around u decrease, such that the speed will never exceed c!

Its given by the equation
t = t' /root{ 1 - (c^2/v^2) }

Which means if t is the adjusted time, t' is teh time with respect to the observer, thus if v = c, u have a time dilation! ur time = infinity, so u can't move faster than speed of light, as definition of velocity is " distance by time " By introducing the new factor and substituting the values you get velocity as zero smile

Thus u can't travel faster than light itself. Though the theory explains what happens and not an exact answer to ur question, which is a complex one ^_^

Regards
Raj
I still think Naruto is the best manga ever \o/

" Tell me not, in mournful numbers,
Life is but an empty dream ! —
For the soul is dead that slumbers,
And things are not what they seem.
"
~~~ A Psalm of Life
~ H.W. Longfellow
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#6
Raajeva,
Thats no explanation.
Your explanation revolves around equations and conjectures that "presume c as the upper limit" and thus it becomes begging the question fallacy.

Speed of light being upper limit is just an assumption of STR. There is always a possibility that we might find an observation that contradicts this. And such an observation is not so devastating as much as other people make out it to be.

The fundamental principle that "all inertial frames of reference obey the same physical laws" leads to existence of a limiting velocity. But there is no need for that limiting velocity to be "speed of light". There might as well be another particle which travels faster than light and its velocity is the limiting velocity. Ofcourse the speed of the particle can't be too different than speed of light because a lot of observed effects of constancy of speed of light have been verified by experiments. So the speed difference would be such that it is within the error limits of the experiments.


(07-May-2012, 08:27 PM)Rajeeva Wrote: The reason why one can't faster then light is not answerable, All the laws which explain it uses the limit as "c" Hence if u change the value of c, the corresponding equation changes too.

A classical way to example is time collapse, Now lets think u and a light beam are having a race, but the thing is u're racing the first beam that was created by the universe, during the Big bang. To explain why u can't travel faster than light U have to go with an alternate theory showing that u travel faster than light, and look into what happens to the theory.

Now back to the race, lets say u travel at 2 times the speed of light (Your some superman, u don't age and u can't die either) so if the universe is a billion yrs old, and the first beam that moves is actually the beam that marks the imaginary boundary of the universe, don't worry u'll move past it in another 500 milllion yrs :P

after 500 million yrs...

Your still moving but u haven't caught up with it? Why? The answer is simple the beam is not stationary, its moving too! according to u the light beam must be at a stand still, since ur moving faster than that beam, but thats not how it works, relative to whosoever, no other bodies speed changes, if a car moving ahead of u is at 80kmph, and u move at 160kmph, If u measure the speed of the car relative to u, it'll be still 80kmph, so lets say u need another 200 million yrs to over come it smile

After 200 million yrs...

U look at the beam finally ur at par with it, for a moment u observer it and wallah! u see the birth of the universe! fascinating isn't it? wait! whts this there's someone gaining on u! its 3 times faster than light speed, and now its observing u, wht he see's is not the beginning of the universe but u're journey! so does that mean if u over come the speed of light u can change history itself? U create a new boundary and u become the history even though u were born way after the first beam was created, U actually changed space time continuum!

But the universe doesn't work that way, here's what actually happens according to the modern theory, First if u gain speed, the factors around u will change. Lets say, ur moving at 0.8c, The fact is the things around u look different, u see a man shaving so slow that u can have a bath at that time like in the movie "Wanted" where the stuff happens in slow mo! But u still take 20 mins to bath, where the other guy who's slower than u take what seems to be an hour or more...

Whts going on? Its simple, the universe adapts towards u! u're in relative with the universe, ur mass increases and time around u decrease, such that the speed will never exceed c!

Its given by the equation
t = t' /root{ 1 - (c^2/v^2) }

Which means if t is the adjusted time, t' is teh time with respect to the observer, thus if v = c, u have a time dilation! ur time = infinity, so u can't move faster than speed of light, as definition of velocity is " distance by time " By introducing the new factor and substituting the values you get velocity as zero smile

Thus u can't travel faster than light itself. Though the theory explains what happens and not an exact answer to ur question, which is a complex one ^_^

Regards
Raj

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#7
Quote: Your explanation revolves around equations and conjectures that "presume c as the upper limit" and thus it becomes begging the question fallacy.

Read my first lines ;) I've said it so

Quote:
Ofcourse the speed of the particle can't be too different than speed of light because a lot of observed effects of constancy of speed of light have been verified by experiments

Hmmm....Yes I agree with u on that, interestingly, u can travel twice the distance that light can travel but still you can't travel past its speed smile

I still think Naruto is the best manga ever \o/

" Tell me not, in mournful numbers,
Life is but an empty dream ! —
For the soul is dead that slumbers,
And things are not what they seem.
"
~~~ A Psalm of Life
~ H.W. Longfellow
Reply
#8
(08-May-2012, 04:02 PM)Rajeeva Wrote: Hmmm....Yes I agree with u on that, interestingly, u can travel twice the distance that light can travel but still you can't travel past its speed smile

Reference please. I am not aware of such behavior.
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#9
Well, Its easy, Consider three points A, B, C Lying at a point O which we consider as the center ( Relative to this case were studying). Let X (Me and U in this case :3) Be observing these three points from another place, suddenly A and B start a race, they move at light speed (Or 0.99c) at opposite directions!

Now for me and you, this seems impossible, but the two bodies are moving apart twice the speed of light :o (or 2* 0.99c). For C too, the bodies apart at twice the speed of light. You must notice that for U and Me the objects move apart at twice the light speed ( This also a factor why when observed from Earth the universe seems to be expanding faster than light speed, which some irrational Theorists [May I say Blog'ists] make it sound as if they've discovered something new).

I hope u get my concept! It was the basis of worm holes (Or something that inspired it smile )
I still think Naruto is the best manga ever \o/

" Tell me not, in mournful numbers,
Life is but an empty dream ! —
For the soul is dead that slumbers,
And things are not what they seem.
"
~~~ A Psalm of Life
~ H.W. Longfellow
Reply
#10
(08-May-2012, 07:49 PM)Rajeeva Wrote: Well, Its easy, Consider three points A, B, C Lying at a point O which we consider as the center ( Relative to this case were studying). Let X (Me and U in this case :3) Be observing these three points from another place, suddenly A and B start a race, they move at light speed (Or 0.99c) at opposite directions!

Now for me and you, this seems impossible, but the two bodies are moving apart twice the speed of light :o (or 2* 0.99c). For C too, the bodies apart at twice the speed of light. You must notice that for U and Me the objects move apart at twice the light speed ( This also a factor why when observed from Earth the universe seems to be expanding faster than light speed, which some irrational Theorists [May I say Blog'ists] make it sound as if they've discovered something new).

I hope u get my concept! It was the basis of worm holes (Or something that inspired it smile )

Interesting. Never thought it from this angle.
But its kind of incorrect to say "you can move at twice the speed of light". The case that you have given actually "distance between two bodies growing at faster than speed of light". That is permitted. But a matter moving at double the speed of light is not considered possible.
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#11
***The reason why one can't faster then light is not answerable, All the laws which explain it uses the limit as "c" Hence if u change the value of c, the corresponding equation changes too.***
WOW.
Really? I mean seriously? Not really no.
I am wondering did you guys get a chance to study relativity at some point? For kids, I recommend 1,2,3,...Infinity by Gamow.
For grown ups - H.C.Verma volume 2. For real people phase 1 Feynman Lectures Vol 1, and for serious People Pauli, and Dirac and Weinberg.

Summary : If speed of light is NOT a constant, then the principle of relativity which states that "Constant velocity is indistinguishable from 0 velocity"
would break down. How? Read Simon Singh {The Big Bang } for the explanation.

Once we have established that velocity of light + our velocity = velocity of light, we need a new equation for addition.
That thing is called a Lorentz Transform. By virtue of that great transformation, if one puts velocity greater than that of c, one gets... well
imaginary numbers. That is not untrue, **you can have particle velocity with more than the velocity of light , they are unreal particles** called tachyons,
and are heavily used in QFT --> Quantum Field Theory. But to understand further we need to put lots of equations, and I mostly hate them.
So I wont. Hope that summarises things up.
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#12
(09-Apr-2013, 12:10 AM)LordPlaguies Wrote: Really? I mean seriously? Not really no.
I am wondering did you guys get a chance to study relativity at some point? For kids, I recommend 1,2,3,...Infinity by Gamow.
For grown ups - H.C.Verma volume 2. For real people phase 1 Feynman Lectures Vol 1, and for serious People Pauli, and Dirac and Weinberg.

Sir, you could have given these references with out sounding rude. I am not the moderator. But I believe the moderator might not like the tone in your post.
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