Some problems with light speed barrier.

Please Register or Log in to view the hidden image!

!!?!?!?!???!??!?!!!??!?!?

Can I have some of what you smoke?

Please Register or Log in to view the hidden image!

Just kidding...

Please Register or Log in to view the hidden image!

Btw, I do believe that the universe might be rotating, but when you start multiplying the "c"s, and "zero cosmic inertia"... what is that?

 

Log in or Sign up to hide all adverts.

Looks like the pool is prety well balanced...

Please Register or Log in to view the hidden image!

If God was democratic, I wonder what He would do with that pool result...

Please Register or Log in to view the hidden image!

Please Register or Log in to view the hidden image!

 

Log in or Sign up to hide all adverts.

MacM, if you understand relativity more than just "mass become infinity when thing reaches the speed of light", you certainly would not make the above statement. Rocket cannot reach the speed of light. Why? This is one of its reason.

Take this formula: E = E<SUB>o</SUB> + K, where E and E<SUB>o</SUB> are respectively your rocket total energy and energy corresponding to its rest mass, and K is the rocket kinetic energy relative to earth. Assume that fuel that your rocket use is brought from earth (no additional fuel after the rocket left the earth).

Here is an unfortunate constraint to your rocket. It cannot convert all energy from fuel to useful kinetic energy, not only because of thermodynamics restriction, but also because any trusting gas or plasma ejected taking away a substantial amount of energy.

There is a good thing. The rest mass of your rocket reduces as you 'burn' the fuel. Therefore, in the above equation, E<SUB>o</SUB> reduces the faster your rocket move, but of course never become zero as you still must have machine and 'bridge' for the astronouts . Assuming that your rocket burn all fuel and only 5% rest mass left (compared to the original rocket and fuel mass). This rest mass can be determined by measuring the number of moles of molecules left in the rocket, including the astronouts, machine, etc.

Now, it's time to determine the 'relativistic mass' of your rocket which is indeed the mass mentioned in your post. Get the rocket kinetic energy, K, which is certainly not infinity but in fact a figure less than the energy generated by your matter/antimatter reaction. Let say, K is 25% of the original rest energy. The rocket total energy is therefore 30% of original rest energy, in other way of saying the rocket 'relativistic mass' is 30% of its original mass.

Based on the above line of thought, rocket cannot have infinity mass. You could burn everything in the rocket, including the machine and astronouts inside, and therefore you have a condition of E<SUB>o</SUB> equal to zero. Your rocket reaches the speed of light, but of course left not a single atom. Even in this situation, you still unable to achieve infinity mass, because the amount of energy that your rocket has is limited.

May be you know some cunning trick to prove that a rocket indeed could have infinity mass. If you do, please show me. I really want to know.

 

Log in or Sign up to hide all adverts.

I think some Harvard scientists would disagree with you:

http://www.sciam.com/article.cfm?articleID=0003BA79-16F9-1C5A-B882809EC588ED9F

That is why I'm not taking it's unfounded postulates seriously. Simply, because the result is negative time of the mathematical equation, or you cannot "divide by 0" so you need infinite energy, or mass is infinite, are nothing but mathematical tricks. I can hardly consider that evidence.

There is absolutely no evidence for these postulates, and therefore it should be considered as psuedoscience. I mean seriously, just because the equation tells you, we can travel backwards in time by travelling faster than the speed of light, you just beleive it. That's not scientific at all.

How the hell do you travel back in time, to an event that has elapsed, that no longer exists, and is not at the same point in spacetime - by travelling faster, forwards in time. It's simple. If you went faster than the speed of light; you would travel further in spacetime. Not backwards in time. I think that's complete rubbish.

 

Paul T,

I have rocket formulas available thank you but you really did miss the point didn't you. If you want to claim infinite mass at v = c then you must also accept infinite energy of the fuel supply by matter/antimatter reaction at v = c. Infinite energy can acclerate infinite mass.

Nobody is proposing rocket technology or actually performing such a task the issue is having infinite fuel energy to do the job by the same reason you claim infinite mass of the rocket..

 

If you were to study the matter more closely, you would find that these scientists would agree with me:

http://www.abc.net.au/science/news/stories/s518907.htm

You can't just go by what is printed in one article written for lay people; often they are oversimplified to the point of misrepresentation.

Once again, the equation does not say that FTL results in traveling back in time. Until you decide to take the time and effort to actually learn Relativity, you are not qualified to have an opinion on the subject.

You know what I think? You just don't want Relativity to be true and will grasp at any straw, no matter how flimsy, to avoid accepting it. Unfortunately for you, the Universe doesn't give one whit for your wants and desires, and will behave by its own rules no matter how much you personally consider them rubbish.

 

I did not claim infinity of mass at v=c. How could you get infinity of mass if you could not get any object with rest mass to move at v=c? Your statement : "infinite energy of the fuel supply by matter/antimatter reaction at v = c" clearly indicates that you misunderstood relativity. As I described earlier, rocket could not gain enough energy to become having infinity of mass. You appear to think that since mass increases with velocity, the mass of the fuel also increases and therefore capable of providing more thrust. It is not true. The amount of energy available to the rocket does not increase. You better think about this again.

Sorry, this is false. There is no magic about relativity. You can't make fuel to become more massive so it could deliver more energy by moving it. Think about this way. Will 1 gallon fuel have more molecules because it move? Of course not.

 

Paul T,

You either don't understand matter/anti-matter energy, don't understand Relativity (I have never seen it claimed that the rocket would increase in mass but not the fuel or other items aboard the rocket also change in mass in like fashion.) Yorn reference to 1 gallon shows you are avoiding the matter/anti-matter reaction I proposed and what to talk chemical reactions.

Let me suggest you come back to this discussion after you have had a bit of cooling and study.

 

Good. Please explain the two things that you claimed, i.e.:

1) Mass of rocket could increase to infinity (when it reach speed v=c). How could it be?
2) Rocket fuel become more powerful (and could become infinitely powerful too) as the rocket move faster. What is the rational?

I disagree with both of them.

Please note that the 1 gallon fuel can be anything, chemical or your matter/antimatter. That 1 gallon of fuel (0.5 gal matter and 0.5 antimatter, if you want) consist of the same number of particles whether it is at rest or move at the speed of 0.999c.

MacM, try to answer this simple question. If you have a rocket with certain amount of fuel that you know capable of delivering 1 million joule of energy, do you think it could increase your rocket kinetic energy by more than 1 million joule? Think carefully. Assume that the final (rest) mass of rocket just a small fraction of the original mass so that its final speed is very close to the speed of light (say 0.999c).

 

Paul T,

You seem to want to make more of this than is merited. My point was and remains that if you want to claim relavistic mass for the rocket, you must also claim relavistic mass for the fuel. If that fuel is matter/anti-matter and that fuel now becomes or approaches an infinite amount of mass then you have a relavistic (or infinite) amount of matter/anti-matter energy. That is whatever the relavistic mass change the rocket and fuel must have the same amount or proportional change. IF you claim infinite rocket mass then you also have infinite fuel mass and infinite matter/anti-matter energy available.

 

The problem is, if you collide one those almost infinite in mass matter molecules with one of those almost infinite in mass anti-matter molecules
to produce the almost infinite in energy explosion, it would probably
blow the tail off your almost infinite in mass spacecraft, unless it was
also almost infinite in strength. Whew!

 

Riiight, it a conspiracy by me, to discredit relativity, so I can prove aliens can get here, right? You have faith in relativity, and faith is not the act of science. It's almost as if I'm trying to show an theist, god doesn't exist. I think we can consider this discussion over.

 

MacM, I knew exactly what you were trying to say. Unfortunately, it was all wrong. Mass of rocket cannot grow to infinity. In fact, it (read: rest mass)reduces as it move faster as more and more fuel thrown out. The 'relativistic mass' associated to the remaining rest mass does increase but cannot exceed the total available energy of the rocket. It would never become infinity. This is where your mistake is. Do not confuse this with phenomenon of particle accelerated in particle accelerator. They are two different cases. A rocket is self propelled (drawing its own limited energy) while particles in those particle accelerators do not.

 

Why does the mass increase is the first question. And what parts of the ship atoms react to what to stop the accelerations, what is there to stop it ?

 

Hi RawThinkTank,
From the point of view of you as the Ship's pilot, mass does not increase at all, and acceleration never becomes ineffective.

 

And what you fail to realise is at you accelerate your rocket, you use up that fuel, and that the fuel to payload ratio drops faster than the increase in relativistic mass. You will always use up your fuel before you can reach c.

Even considering a rocket that used direct matter to energy conversion, and that all of this energy was applied to increasing the velocity of the Payload (An impossibility since some percentage will be lost to the reaction exhaust.), then taking matter/energy converison and relativistic mass increase of fuel and ship into consideration, you get the following realtionship:

V = c* sqrt(1-1/(Mf/Mp+1)²)

Mf and Mp are the initial rest masses of the fuel and payload respectively.
As can be seen, no matter how much fuel vs payload you start out with, your final velocity end up below c.

 

Janus58,

I'm not in disagreement with the arguement base against any practical attempt to achieve v = c. But that hasn't been the issue. If we are talking hypothetical (and we must) then we can hypothetically claim 100% efficiency.

The point was and still is against the arguement that mass of the rocket increases but that the energy to propell it doesn't. Using the matter/anti-matter reaction ties the energy available to the same relavistic curve - which was my point - not that other pragmatic aspects would prevent such an actual venture.

 

As very well noted by Pete a few posts earlier, the mass only increases for someone not in the frame of reference of the rocket. For someone in the frame of reference of the rocket, the mass stays the same (or only decreases because fuel gets burnt). You need to look in the frame of reference of the rocket to see what energy is available for further acceleration.

Still the same old frame of reference problems, eh Mac?

 

Yes, Crisp, and we are back to an older question of mine. In the frame of reference
of the rocket, the mass of the rocket nor its propulsion system increases. If the
rocket is self powered, i.e. not pushed by an external source, why does it take 'an
almost infinite amount of energy' to push it to near 'c'? The limitation would seem to me
to be on the velocity of the power source. Even a source that was dumped out the
rear at 'c' would not give an equal velocity to the rocket. The reason the craft cannot
attain 'c' is because of the limited velocity of the propulsion, not because the craft
attains 'infinite mass.' I know Special Relativity's equations state nothing with mass
can attain 'c', but aren't those equations based on the rise of mass to infinity? That
is where this layman has difficulties. Isn't the restriction of mass attaining 'c' based
on a false premise? I am asking for help understanding this in logical terms.

 

Common misconception. The final velocity of a rocket is not limited to the exhaust velocity. Case in point, a satellite needs to attain around 7000 m/s to achieve orbit. Present rocket technology only produces exhaust velocities of around 4000 m/s. Obviously, if your assertion was true, then we would never have been able to achieve orbit, let alone escape velocity.

Another common misconception, Actually what SR says is that the kinetic energy of an object increases asymptotically as the velocity approachs c.

If you want an "intuitive" explaination, try this:

Energy and mass are equivalent (matter energy conversion, etc)

What this also means is that some properties that we originally believed were exclusive to mass also pertain to energy. (namely inertial properties and coupling with gravity) .

Thus if you speed up an object relative to you, you also increase its energy. but by adding energy you are also adding to the object's inertia and its tendancy to resist further change of its velocity. Thus it will take even more additional energy to produce the same magnitude of velocity change, but adding even more energy adds even further to the object's inertia. As you go on, the increase in inertia begins to out pace the increase in velocity. The upshot is that the maximum velocity attainable has a limit. You can keep pumping energy into your object, and you will keep getting closer and closer to this limit, but you will never reach it.