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# A speed beyond light question ^^

1
Sat 20 Dec, 2008 07:35 am
@Brandon9000,
Be gentle with me Brandon - but if two objects leave the same point at three quarters of the speed of light in opposite directions are they travelling at 1.5 times the speed of light away from each other? (high school physics and first year uni only - and the odd Asimov non-fiction book)

All this talk of 'planet of origin' is freaking me out - do you mean 'frame of reference'? Sorry it just sounds like I could break the lays of physics if I left a planet other than my own.
Brandon9000

1
Sat 20 Dec, 2008 08:31 am

Be gentle with me Brandon - but if two objects leave the same point at three quarters of the speed of light in opposite directions are they travelling at 1.5 times the speed of light away from each other? (high school physics and first year uni only - and the odd Asimov non-fiction book)

All this talk of 'planet of origin' is freaking me out - do you mean 'frame of reference'? Sorry it just sounds like I could break the lays of physics if I left a planet other than my own.

I do mean frame of reference, but I was translating it into something more palatable to the layman.

If you are sitting on your front porch and see two spaceships take off in opposite directions, and accelerate to 3/4 the speed of light in opposite directions, you will jusdge their relative speed to be 1.5 times the speed of light, but notice that you do not see any one object exceeding the speed of light. When either of these two spaceships looks at each other, it will see the other receeding from it .96 the speed of light. None of the three of you will measure any one object as travelling at a speed as high as the speed of light.
0 Replies

ebrown p

1
Sat 20 Dec, 2008 08:35 am

The answer will be different depending on why point of view you are using.

Let's start with this "point" you are talking about this. Let's put our friend Mr. Bob at this point with some highly accurate measuring equipment to see the objects. Sure he would observe one object going .75 the speed of light and and other object going .75 in the opposite direction.

He could, of course, do some simple math and say that they are going 1.5 the speed of light compared to each other. The problem is that this simple math is meaningless in that the number 1.5 doesn't signify anything. (In fact most of us would say this calculation is wrong, although then we would need to define wrong).

If you were on one of the objects with the exact same equipment, you would accurately measure the second object (which Mr. Bob insists should be going at 1.5 the speed of light) traveling at a speed of less than the speed of light.

The point is that measuring speeds depends on the "frame of reference". Mr. Bob's simple calculations will get you over the speed of light.... but no one from any frame of reference will see the object going over the speed of light.
0 Replies

akaMechsmith

1
Sat 20 Dec, 2008 01:45 pm

Two objects receeding from each other each travelling at 75% of the speed of light "c" would not be able to "observe" each other for the simple mechanical reason that the light between one and the other would be "red shifted" towards infinity. The energy level of the wave to the observer would be too low to be able to convey any information although an observer at the midpoint would be able to see both objects. If you define a universe as everything inside a volume contained within a sphere emaniating from a "big bang" and delinated by a microwave "horizon" it becomes rather obvious that nothing within the observable universe can exceed the speed of light "relative to an Earthbound observer.

Consequently we can observe nothing in the universe travelling faster than "c". This is merely a commentary on the physical nature of light and our conception of the universe and will have little to do with the nature of the universe.
High Seas

1
Sat 20 Dec, 2008 01:56 pm
@akaMechsmith,
That's true enough, as far as it goes, but mathematically speaking faster-than-light propagation exists. Whether it carries data other than gravitational forces is what's in doubt:

Quote:
General relativity has a geometric and a field interpretation. If angular momentum conservation is invoked in the geometric interpretation to explain experiments, the causality principle is violated. Meanwhile, the field interpretation avoids this problem by allowing faster-than-light propagation in forward time. Lightspeed is not a universal speed limit.

http://www.metaresearch.org/cosmology/gravity/speed_limit.asp

Btw, the above isn't a new observation - it's been proven at least since dark matter and dark energy were found to exist in abundance in our universe. And it's nothing to do with postulating the existence of either string theory or parallel universes, which are just unproven (and unprovable) theories.
High Seas

1
Sat 20 Dec, 2008 02:07 pm
@High Seas,
Details of previous statement can be found about halfway down the previous link:

Quote:
Now that we know that Lorentzian relativity is experimentally viable [18] and allows faster-than-light (ftl) propagation in forward time [19], ftl propagation is no longer forbidden in physics, and ftl force carriers are the most reasonable interpretation of the equations. I expect that no one would ever have thought otherwise if they had not mistakenly believed that ftl propagation was forbidden in physics.

numbers refer to bibliography
0 Replies

Brandon9000

1
Sat 20 Dec, 2008 06:13 pm
@akaMechsmith,
akaMechsmith wrote:

Two objects receeding from each other each travelling at 75% of the speed of light "c" would not be able to "observe" each other for the simple mechanical reason that the light between one and the other would be "red shifted" towards infinity. The energy level of the wave to the observer would be too low to be able to convey any information although an observer at the midpoint would be able to see both objects. If you define a universe as everything inside a volume contained within a sphere emaniating from a "big bang" and delinated by a microwave "horizon" it becomes rather obvious that nothing within the observable universe can exceed the speed of light "relative to an Earthbound observer.

Consequently we can observe nothing in the universe travelling faster than "c". This is merely a commentary on the physical nature of light and our conception of the universe and will have little to do with the nature of the universe.

Each of the two ships would observe the other to be receding from it at .96 the speed of light, according to the relativistic velocity addition formula. The light would be greatly shifted in frequency, but not to infinity, and, in principle, each ship could observe the other with sufficient instrumentation. Each would observe the shifted light from the other ship to be approaching at the speed of light, at whatever frequency.
0 Replies

Mr BOB

1
Sat 20 Dec, 2008 09:05 pm
Brandon 9000

Catch up with the times dude
I understand that according to the theory of relativity..nothing can travel faster then the speed of light
I also understand special theory of relativity says a rosenburg bridge/tunnel is possible which though in of itself would not persay be traveling faster then the speed of light..but by creating this special bridge (known better as a worm whole) would enable faster then light speed travel..

However i am not talking about the theory of relativity (persay)
Nor am i speaking of going faster then light by means of a worm hole.

If we return the the point in time (known as) the Big Bang.
when the big bang happened all the energy was in FACT traveling beyond the speed of light.
It is this that has science perplexed
it is this that is not understood
However it may be understandable given the immense energy present and released by the big bang that some how caused and or enabled energy and matter to travel faster then the speed of light.

what really has science wondering is why and how..even TODAY
galaxies we have only begun to be able to see
how these extremely far off galaxies are moving away from us at well beyond the speed of light ( as measured by the red shift they exhibit)

I can care less whether you believe me or not
This is FACT and happening as we speak (as you read this)

if you look at red shift it shows nearly all galaxies moving away from us
and in so doing it is theorized billions and billions of yrs from now
all the stars we see will have moved off beyond our ability to see and study them (taking the expansion theory way past what it was thought to be)
yet only recently is it also realized that the galaxies nearly beyond our seeing
are moving away from us faster then other galaxies closer to us.

in fact the closer a said galaxy is to us the slower it is moving away from us
the further a said galaxy is from us the faster it is moving away from us
( both realized as FACTs obtained by their red shift )

Again the Galaxies furthest from us (so far off that only with very new discoveries of them and our ability to see them because of advancing technologies in sciences and abilities) even today are seen to be moving away from us at speeds beyond the speed of light

Einstein himself thought his E=MC2 was only a minor realization
He thought at first his theory of relativity would be far more important
Einstein then added what he thought at first were the only flaws to his finding
(adding special relativity to complement his theory of relativity )
However even to the day he died he was seeking and saddened in not having found the holy grail which is the theory of everything would be found

That is where one can explain both the large and the very small are understood and controlled via a single set of laws of science
He ( Einstein) hinted at it in a paper then with drew it
The Unified Field Theory
but he backed off of it in realizing it was not properly complete

in later yrs a few used various forms of string theory as being the holy grail
but still we are not there yet

So Brandon 9000
for you to discount the existence of matter and energy known to be traveling faster then the speed ... simply because you want to invoke the speed limit of the theory of relativity is a bit behind the times

I do not yet have the answer to this
but at this time neither does anyone else

maybe you need look further ahead and consider you do not know it all
I know i do not

but i also know that the Big Bang Theory is not what most think it to be

But then that is the Great Lure of Science
in understanding what really is
gungasnake

1
Sat 20 Dec, 2008 09:11 pm
@crayon851,
Electromagnetic radiation does not travel faster than C and no particle which we have observed travels that fast.

Nonetheless gravity propagates instantaneously to within our ability to measure it and there is sound reason to believe that what we have been calling the basic atomic particles for the last hundred years have their own orbital systems and sub particles and that the computed necessary speed of one of those sub electron particles would be vastly greater than C.
Brandon9000

1
Sat 20 Dec, 2008 09:52 pm
@Mr BOB,
Mr BOB wrote:

Brandon 9000

Catch up with the times dude

...

But then that is the Great Lure of Science
in understanding what really is

As I've already said, if our observation of the red shift of distant objects indicates a speed faster than light, it's because the space itself is expanding, not because something is moving through space at a super-luminal speed. No form of propulsion can accelerate an object up to the speed of light, as a direct consequence of Special Relativity. This is high school physics that's over a hundred years old, and verified countless times in laboratories. If you've got a way for a man-made object to reach super-luminal speeds without accelerating up to them, that's a different story, but I don't know of any ideas for how to do that which are even being discussed seriously by real scientists.
0 Replies

Brandon9000

1
Sat 20 Dec, 2008 09:56 pm
@gungasnake,
gungasnake wrote:

Electromagnetic radiation does not travel faster than C and no particle which we have observed travels that fast.

Nonetheless gravity propagates instantaneously to within our ability to measure it and there is sound reason to believe that what we have been calling the basic atomic particles for the last hundred years have their own orbital systems and sub particles and that the computed necessary speed of one of those sub electron particles would be vastly greater than C.

Sorry, gravity propagates at exactly the speed of light in vaccuum. As for atomic particles, one doesn't talk about their trajectories or speeds because of the Uncertainty Principle. One talks about their quantum wavefunctions.
0 Replies

Fountofwisdom

1
Sun 21 Dec, 2008 07:54 pm
A theoretical faster than light particle is called a tachyon: It would behave in the opposite way to our universe in terms of energy: e.g. the harder you pushed it : the more it would stay still: Isaac Asimov did a good explanation of this .
Fountofwisdom

1
Sun 21 Dec, 2008 07:56 pm
This is currently whimsy: However the impossible tends to happen quite frequently in physics: I believe it would be foolish to rule anything out:
0 Replies

Brandon9000

1
Mon 22 Dec, 2008 01:33 am
@Fountofwisdom,
Fountofwisdom wrote:

A theoretical faster than light particle is called a tachyon: It would behave in the opposite way to our universe in terms of energy: e.g. the harder you pushed it : the more it would stay still: Isaac Asimov did a good explanation of this .

The only way such a particle could exist would be to be created travelling faster than light. Nothing can accelerate up to the speed of light.
0 Replies

Fountofwisdom

1
Tue 23 Dec, 2008 01:35 pm
Tachyons could have been created before the laws of physics were invented: or they could have invented themselves: science should be about thinking how the impossible could be achieved:
Brandon9000

1
Tue 23 Dec, 2008 04:46 pm
@Fountofwisdom,
Fountofwisdom wrote:

Tachyons could have been created before the laws of physics were invented: or they could have invented themselves: science should be about thinking how the impossible could be achieved:

Every laboratory test for decades has shown that Special Relativity is exactly correct to as many decimal places as can be measured, and if it is, then no material object can be accelerated to the speed of light. There is probably more physics that's not known, and possibly even some way of achieving an effective speed greater than light speed, but absolutely not by ordinary acceleration. This is old physics that has been tested and is well understood.

I doubt that y0u are qualified to opine about what science "should be thinking" about? Have you bothered with going to school and learning physics? Unlike you, actual scientists, when stating an opinion, have to pay some attention to what's been learned during the past few centuries.
0 Replies

akaMechsmith

1
Tue 23 Dec, 2008 05:14 pm
re. Particularly for Brandon and Mr.Bobs posts.

As long as light is a "wave" there will be some continuity and we can call it light or an X-ray or a radiowave as the case may be. But at some velocity the wave will be broken and then the characteristics will change.

If I am out in my sailboat in a hurricane I will observe that at some point the wind driven waves will diminish as the tops will be blown off destroying the wave function. A water wave will build as long as it can absorb wind energies. If the bottom of the wave "stumbles" on the seabed it also destroys the wave. We call those "breakers" and it signifies the end of the wave.

I suspect that what will happens with light is that at some velocity the light waves will become discontinuous thus destroying the wave function. Then it becomes something not light. I know that electromagnetic waves (submarine ELF radio) can be many miles long but eventually the wave function of light also must be lost in the background. Somehow I doubt that there are a bunch of photons hanging around in outer space waiting for something to collapse onto but there may be.

The math became too much for me when I tried to figure out exactly when this point occurs but occur it must. The speed of time also enters into it.

Mr. Bob,
The "red shift" theory of the expanding universe has a few too many anomalies for me to take as "gospel". Also keep in mind that "c" is a constant is not the same as saying that the speed of light is constant. "c" also defines the speed of time which is not the same for everybody.
High Seas

1
Tue 23 Dec, 2008 05:31 pm
@akaMechsmith,
That was Feynman's idea also, speed of time; mathematically the transmission of gravity (not particles called gravitons, changes in the fabric of the spacetime grid itself) is instantaneous (or at least many orders of magnitude faster than the speed of light) as proven by experiments. That's from the link I posted earlier on this page:

Quote:
Feynman preserves the force and motion concepts with their classical meanings, and comments: "It is one of the peculiar aspects of the theory of gravitation, that it has both a field interpretation and a geometrical interpretation. ... the fact is that a spin-two field has this geometrical interpretation: this is not something readily explainable - it is just marvelous. The geometrical interpretation is not really necessary or essential to physics."
0 Replies

akaMechsmith

1
Tue 23 Dec, 2008 05:32 pm
Mr Bob.

According to Big Bang Theories the "expansion of space" as opposed to an "expansion in space" is what makes it possible for things to travel faster than "c". Since there was no "space" at the time there was nothing for anything to go faster than therefore the constraints of relativity did not apply. For all I know they may not apply yet at the boundaries of the "Big Bang" universe. Where ever they may be!

Don't ask me to defend it. I merely hope I explained that part of the theories for you.
0 Replies

akaMechsmith

1
Tue 23 Dec, 2008 05:59 pm
Hello High Seas,

I agree with Richard Feynmann pretty well. I like to call gravity a field which does not have to be instantaneous in propagation. However in our current definitions we tend to call anything faster than light instantaneous. This I am afraid is simply a note on some of the "mechanical" properties of electromagnetic radiation rather than any reversal of causuality as shown by some experiments.

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