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# Lightspeed = Infinite mass?

anakonda118
So, I was watching a TV show not long ago and heard someone discuss about how fast you would be able to fly. One of the scientist sayd that one of the reasons you can't go faster than light is because when you hit the speed of light, the mass of the object going with lightsspeed would be infinite. Is this true and if yes, how is it even remotely possible?

-----------------
Bikerman
Well, yes and no.
It isn't THE reason (there are others), but it is true.
As you get closer to the speed of light, some of the energy being used to 'push' is converted into mass.
Remember that Einstein told us that energy and mass are two ways of describing the same thing (e=mc^2).
It is obvious from that famous formula that if you stick energy into a body, that is the equivalent of an increase in mass. Now, the mass increase is very very small, since it is equal to the amount of energy divided by roughly 90000000000000000).

This doesn't just happen as you get close to light-speed - it happens all the time.
A charged battery has more energy than a dead one, so it must weigh more. You wouldn't be able to measure it (far too small), but it would be heavier. Likewise if you stick an iron bar in the fire, it gets heavier as it heats up (more energy).

Notice c in Einstein's famous equation? c is the speed of light. We can look at c as the conversion factor between mass and energy. If we want to measure energy, rather than mass, we multiply by c and then by c again. To convert the other way we divide instead. Particle physicists normally use energy to measure the tiny particles they work with, but with bigger things it is more convenient to use mass.
anakonda118
I think I understand some of it atleast. But This covers only that things get heavier when they go faster, what makes it get infintly heavy when it hits the speed of light ? (or am I missing something)
_AVG_
In order to conserve momentum, the mass of a moving body appears to increase - as Bikerman said.

Mathematically, this apparent increased mass is given by : m*γ where m is the mass of the object at rest and γ is the Lorentz Factor, a function of the body's velocity given as follows:

γ(v) = 1/sqrt(1-v^2/c^2)

As you can see, if you plug in the speed of light, γ becomes infinite ergo the object's mass appears to be infinite. However, an object can never be accelerated to the speed of light as some energy which is used to accelerate it will always add to its mass thereby requiring even more energy to accelerate the object at the same rate. Hence, an infinite amount of energy would be required to accelerate an object to the speed of light. This can be shown mathematically as well:

E = (γ-1)mc^2 where E is the Kinetic Energy of a moving body and c is the speed of light (m and γ are the same as before)

Again, plug in c in the formula and you'll end up with infinity again.
Indi
 Bikerman wrote: A charged battery has more energy than a dead one, so it must weigh more. You wouldn't be able to measure it (far too small), but it would be heavier.

i've heard that before and always questioned the logic involved. A charged battery has more useful energy than a dead one, but that doesn't necessarily imply that it has more energy. In other words, it may just be the case that a charged and dead battery both have identical energy, but the latter has a much higher entropy.

Consider this: suppose you had a battery that operated on an endothermic chemical reaction (when discharging). In other words, you are getting energy out of the battery in the form of electrical energy, but the battery is sucking energy in in the form of thermal energy. i don't see that it's a violation of physics that the energy out must be greater than the energy in in that case. In fact, it even seems reasonable. i am not a chemist, but it seems reasonable to hypothesize a battery type where the chemical bonds of the chemical after the discharge reaction are stronger than before (the weaker chemical bonds in the charged state would mean it it is easier for the electrons or ions to break free and go into the circuit, and the discharged state would be more stable because the bonds are stronger).

i don't know of any battery types that are endothermic, but it just seems possible to me. Am i off base?
Bikerman
Hmm....my rather simple thought experiment has me using a 12V car battery until it is discharged. Then an input of x joules charges it back to 'full'. Now, if the charged and uncharged states are comparable over 2 cycles then that must surely mean that dischared + energy = charged is symmetrical (or close to)?

The endothermic battery is intriguing. I'm going to have to stick that on my 'things to look into soon' spike and get back on that one....
metalfreek
It all comes down to mathematics and equations to solve these issues. Here is one equation

m=m0/(sqrt(1-(v^2/c^2)))

If you see carefully as v increases, mass also increases. When v=c then denominator becomes zero and hence mass (m) becomes infinity. And here is the problem (so to say). The mathematics that we have is not so good when it comes to infinity.

So to understand what infinite mass really means practically, one has to travel at the speed of light and I don't see man traveling at the speed of light very soon.
Dennise
As others have posted above, this is easiest to see mathematically.

As a body's speed increases its mass increases too, but it's NOT a linear relationship. Instead, as the speed approaches the speed of light. the mass increases asymptotically toward infinity as the limit. As this limit is approached, and mass increases without limit, so does the energy needed to further increase the body's speed. This is why anything having mass can never reach the speed of light.

This is difficult to understand without a knowledge of the calculus.
To either help simplify or greatly confuse the discussion -

You can't really say that when it is at the speed of light, it would have infinite mass, because it can't go at the speed of light, because it would have to have infinite mass.

I know it makes sense if you understand where I'm coming from, but otherwise, could just be really really unhelpful.
ocalhoun
 Radar wrote: You can't really say that when it is at the speed of light, it would have infinite mass, because it can't go at the speed of light, because it would have to have infinite mass.

'It' can't accelerate to the speed of light because of the increasing mass, but what if it always had been at the speed of light, been that way since the beginning of the universe?
anakonda118
ocalhoun wrote:
 Radar wrote: You can't really say that when it is at the speed of light, it would have infinite mass, because it can't go at the speed of light, because it would have to have infinite mass.

'It' can't accelerate to the speed of light because of the increasing mass, but what if it always had been at the speed of light, been that way since the beginning of the universe?

Then everything would have bumped into it now, and we wouldn't be here
_AVG_
anakonda118 wrote:
ocalhoun wrote:
 Radar wrote: You can't really say that when it is at the speed of light, it would have infinite mass, because it can't go at the speed of light, because it would have to have infinite mass.

'It' can't accelerate to the speed of light because of the increasing mass, but what if it always had been at the speed of light, been that way since the beginning of the universe?

Then everything would have bumped into it now, and we wouldn't be here

No. I think he's implying that the photon has a rest mass of 0. That's the reason it travels at the speed of light.
Bikerman
The obvious objection is that if the thing had been travelling at c when the universe was created in the BB then where the hell was it moving? It can't have been moving through spacetime since that didn't exist..
ocalhoun
 Bikerman wrote: The obvious objection is that if the thing had been travelling at c when the universe was created in the BB then where the hell was it moving? It can't have been moving through spacetime since that didn't exist..

All right, if you want to be technical, let's assume it began moving at exactly the same 'time' that our familiar dimensions of space and time came into existence.

Just trying to posit the difference between impossibility of becoming and impossibility of being.
Bikerman
ocalhoun wrote:
 Bikerman wrote: The obvious objection is that if the thing had been travelling at c when the universe was created in the BB then where the hell was it moving? It can't have been moving through spacetime since that didn't exist..

All right, if you want to be technical, let's assume it began moving at exactly the same 'time' that our familiar dimensions of space and time came into existence.

Just trying to posit the difference between impossibility of becoming and impossibility of being.

(Yep, I know what you are trying to posit, that's why I'm forcing exactitude
The same objection applies and you have now arrived where I was hoping.
OK, now, here's the biggie...in a universe with nothing in it, how can you say that anything is moving?
There, in a nutshell, you have the question that raged across theories and generations until Einstein, and even Einstein changed his mind at least twice...
I'm not going to spoil this by answering the conundrum, it would be better, I think, to see if anyone has an interesting take on it.
To start it off - the basic question is framed as Mach's Principle. I usually summarise it in the following question: "Is it sensible to talk about motion when there is only one object in the universe?"
Others give more specific definitions.
A specific question would be:
"we know that non-inertial frames (where there is acceleration) produce effects. We can label this as 'centrifugal force' (though that is a misleading label because it implies a distinct force, and there is no such force, simply Newtonian mechanics - specifically inertia. Thus the weight will continue in a straight line but the string exerts an inward force adjusting the path, and we get an orbit).
We also know that objects undergoing such motion sometimes show it explicitly. (One simple exemplar is a bucket full of water. Spin the bucket and the water rises up the sides of the bucket).
So the question becomes 'will the water climb the sides of our bucket if it is the only object in the universe?" If yes then you are clearly implying a reference frame, against which we can say things move. If there is no such 'absolute' frame then how can we validly say that the bucket is spinning? If there is such a frame then what defines it?
supernova1987a
 anakonda118 wrote: So, I was watching a TV show not long ago and heard someone discuss about how fast you would be able to fly. One of the scientist sayd that one of the reasons you can't go faster than light is because when you hit the speed of light, the mass of the object going with lightsspeed would be infinite. Is this true and if yes, how is it even remotely possible? -----------------

It is not possible. That is why you can never reach the speed of light!!!
Einstein was amazing! Maybe he was a guy from another planet. hehe.

sorry abt the emoticons
ongdesign
your body have limitation. if you travel speed of the light, your mass is shrinking and time is shrinking. the mass is not exist and only proton. which is your body is not exist any more during the time. you may gain back if your travel speed back to normal. but no tested result, it is only an theory.
_AVG_
 ongdesign wrote: your body have limitation. if you travel speed of the light, your mass is shrinking and time is shrinking. the mass is not exist and only proton. which is your body is not exist any more during the time. you may gain back if your travel speed back to normal. but no tested result, it is only an theory.

I'm afraid you've got it wrong, when you travel at the speed of light, your length theoretically contracts to 0 while your mass and time dilate to infinity (when plugged in the relativistic formulae) BUT any massive object cannot reach the speed of light as an infinite amount of energy is required for such an acceleration.
ocalhoun
 supernova1987a wrote: sorry abt the emoticons

I laughed.
Why post a bunch of random emoticons, then immediately apologize for it, when you could just erase them?
Jthomasnaz
 anakonda118 wrote: So, I was watching a TV show not long ago and heard someone discuss about how fast you would be able to fly. One of the scientist sayd that one of the reasons you can't go faster than light is because when you hit the speed of light, the mass of the object going with lightsspeed would be infinite. Is this true and if yes, how is it even remotely possible? -----------------
mass could not become infinite or you would not be able to square the speed of light. Not having enough energy to travel 186,000 miles per second is the same as saying, "not enough energy to go 185,000 miles per second or 190,000 miles per second. you can prove anything you want mathematically. I could take bible truth and put mathematical symbols to it and prove it mathematically.
Bikerman
 Jthomasnaz wrote: mass could not become infinite or you would not be able to square the speed of light. Not having enough energy to travel 186,000 miles per second is the same as saying, "not enough energy to go 185,000 miles per second or 190,000 miles per second. you can prove anything you want mathematically. I could take bible truth and put mathematical symbols to it and prove it mathematically.
Errr...a few problems here:
a) rather than give inaccurate figures for the speed of light it is better to just use 'c' - those reading these forums will tend to know what it means.
b) Saying that 'mass could not become infinite' because of the impossibiliy of c^2 is incoherent. I presume you MEAN to say that E=MC^2 would have no specific solution where M = ∞ . That is a very bad argument in itself, for reasons I would be happy to expand upon if you consider yourself capable of following.....
c) You could NOT take 'bible truth' and mathematically prove it. I have some doubt that you have the ability to prove ANYTHING mathematically, and I am almost certain that you have no conception of what a rigorous mathematical proof actually entails.
Jthomasnaz
Bikerman wrote:
 Jthomasnaz wrote: mass could not become infinite or you would not be able to square the speed of light. Not having enough energy to travel 186,000 miles per second is the same as saying, "not enough energy to go 185,000 miles per second or 190,000 miles per second. you can prove anything you want mathematically. I could take bible truth and put mathematical symbols to it and prove it mathematically.
Errr...a few problems here:
a) rather than give inaccurate figures for the speed of light it is better to just use 'c' - those reading these forums will tend to know what it means.
b) Saying that 'mass could not become infinite' because of the impossibiliy of c^2 is incoherent. I presume you MEAN to say that E=MC^2 would have no specific solution where M = ∞ . That is a very bad argument in itself, for reasons I would be happy to expand upon if you consider yourself capable of following.....
c) You could NOT take 'bible truth' and mathematically prove it. I have some doubt that you have the ability to prove ANYTHING mathematically, and I am almost certain that you have no conception of what a rigorous mathematical proof actually entails.

If you always need more energy to approach the speed of light and not get there it doesn't matter if it is 1 mph under the speed of light or 1 mile mph over the speed of light. The point is using the speed of light as a limit is not rational. And yes people do try to prove their theory is correct by using mathematical symbolism and formula. You talk as if everything you believe is absolute and cannot be challenged --but I disagree thus far.
kelseymh
Jthomasnaz wrote:
Bikerman wrote:
 Jthomasnaz wrote: mass could not become infinite or you would not be able to square the speed of light. Not having enough energy to travel 186,000 miles per second is the same as saying, "not enough energy to go 185,000 miles per second or 190,000 miles per second. you can prove anything you want mathematically. I could take bible truth and put mathematical symbols to it and prove it mathematically.
Errr...a few problems here:
a) rather than give inaccurate figures for the speed of light it is better to just use 'c' - those reading these forums will tend to know what it means.
b) Saying that 'mass could not become infinite' because of the impossibiliy of c^2 is incoherent. I presume you MEAN to say that E=MC^2 would have no specific solution where M = ∞ . That is a very bad argument in itself, for reasons I would be happy to expand upon if you consider yourself capable of following.....
c) You could NOT take 'bible truth' and mathematically prove it. I have some doubt that you have the ability to prove ANYTHING mathematically, and I am almost certain that you have no conception of what a rigorous mathematical proof actually entails.

If you always need more energy to approach the speed of light and not get there it doesn't matter if it is 1 mph under the speed of light or 1 mile mph over the speed of light. The point is using the speed of light as a limit is not rational. And yes people do try to prove their theory is correct by using mathematical symbolism and formula. You talk as if everything you believe is absolute and cannot be challenged --but I disagree thus far.

Disagreement is fine. However, if you attempt to make a scientific argument, then you need to have an understanding of the science involved, which includes the mathematics. If you don't have that understanding then your disagreement arises from ignorance, not from knowledge.
Jthomasnaz
kelseymh wrote:
Jthomasnaz wrote:
Bikerman wrote:
 Jthomasnaz wrote: mass could not become infinite or you would not be able to square the speed of light. Not having enough energy to travel 186,000 miles per second is the same as saying, "not enough energy to go 185,000 miles per second or 190,000 miles per second. you can prove anything you want mathematically. I could take bible truth and put mathematical symbols to it and prove it mathematically.
Errr...a few problems here:
a) rather than give inaccurate figures for the speed of light it is better to just use 'c' - those reading these forums will tend to know what it means.
b) Saying that 'mass could not become infinite' because of the impossibiliy of c^2 is incoherent. I presume you MEAN to say that E=MC^2 would have no specific solution where M = ∞ . That is a very bad argument in itself, for reasons I would be happy to expand upon if you consider yourself capable of following.....
c) You could NOT take 'bible truth' and mathematically prove it. I have some doubt that you have the ability to prove ANYTHING mathematically, and I am almost certain that you have no conception of what a rigorous mathematical proof actually entails.

If you always need more energy to approach the speed of light and not get there it doesn't matter if it is 1 mph under the speed of light or 1 mile mph over the speed of light. The point is using the speed of light as a limit is not rational. And yes people do try to prove their theory is correct by using mathematical symbolism and formula. You talk as if everything you believe is absolute and cannot be challenged --but I disagree thus far.

Disagreement is fine. However, if you attempt to make a scientific argument, then you need to have an understanding of the science involved, which includes the mathematics. If you don't have that understanding then your disagreement arises from ignorance, not from knowledge.

I may be stupid, however, can we not talk with reason instead of being mathematical genius's.
kelseymh
Jthomasnaz wrote:
kelseymh wrote:
Jthomasnaz wrote:
Bikerman wrote:
 Jthomasnaz wrote: mass could not become infinite or you would not be able to square the speed of light. Not having enough energy to travel 186,000 miles per second is the same as saying, "not enough energy to go 185,000 miles per second or 190,000 miles per second. you can prove anything you want mathematically. I could take bible truth and put mathematical symbols to it and prove it mathematically.
Errr...a few problems here:
a) rather than give inaccurate figures for the speed of light it is better to just use 'c' - those reading these forums will tend to know what it means.
b) Saying that 'mass could not become infinite' because of the impossibiliy of c^2 is incoherent. I presume you MEAN to say that E=MC^2 would have no specific solution where M = ∞ . That is a very bad argument in itself, for reasons I would be happy to expand upon if you consider yourself capable of following.....
c) You could NOT take 'bible truth' and mathematically prove it. I have some doubt that you have the ability to prove ANYTHING mathematically, and I am almost certain that you have no conception of what a rigorous mathematical proof actually entails.

If you always need more energy to approach the speed of light and not get there it doesn't matter if it is 1 mph under the speed of light or 1 mile mph over the speed of light. The point is using the speed of light as a limit is not rational. And yes people do try to prove their theory is correct by using mathematical symbolism and formula. You talk as if everything you believe is absolute and cannot be challenged --but I disagree thus far.

Disagreement is fine. However, if you attempt to make a scientific argument, then you need to have an understanding of the science involved, which includes the mathematics. If you don't have that understanding then your disagreement arises from ignorance, not from knowledge.

I may be stupid, however, can we not talk with reason instead of being mathematical genius's.

I didn't say you were stupid. You made a set of statements which were logically incoherent, scientifically nonsensical and mathematically ignorant. If you do not understand the science, then, no we cannot talk reasonably, since you're unwilling to take the reasonable step of understanding what you are trying (and failing) to talk about.
Bikerman
Jthomasnaz :
What kelseymh said is correct. You are talking about something you don't understand to people who DO understand.
Would you consider yourself competent to offer your opinion to a brain surgeon about to operate? Do you think that you could usefully advise the rocketry specialists at NASA, or particle theorists at CERN?
I doubt it. So what makes you think that your opinion on Relativistic physics is worth anything?
What you call reason is nothing more than common sense - which in a specialist 'non common' arena like relativistic physics is just another way of saying complete ignorance.

If you find it objectionable to have your mistakes pointed out then I'm afraid you are in the wrong forums. The internet is full of places where people can spout ill-informed opinion on complex physics and have other numpties congratulate them on their brilliance.

Here, however, we don't do that.

What you need to realise is that this stuff is HARD. You have to put a lot of work into understanding the physics - and that includes getting some sort of handle on the mathematics.
I'm no expert (kelseymh IS, btw) - I have spent countless hours educating myself so that I can, at least, talk sensibly about the basics. Science isn't a democracy and ill-informed opinion is worth precisely nothing.
Jthomasnaz
Jthomasnaz wrote:
kelseymh wrote:
Jthomasnaz wrote:
Bikerman wrote:
 Jthomasnaz wrote: mass could not become infinite or you would not be able to square the speed of light. Not having enough energy to travel 186,000 miles per second is the same as saying, "not enough energy to go 185,000 miles per second or 190,000 miles per second. you can prove anything you want mathematically. I could take bible truth and put mathematical symbols to it and prove it mathematically.
Errr...a few problems here:
a) rather than give inaccurate figures for the speed of light it is better to just use 'c' - those reading these forums will tend to know what it means.
b) Saying that 'mass could not become infinite' because of the impossibiliy of c^2 is incoherent. I presume you MEAN to say that E=MC^2 would have no specific solution where M = ∞ . That is a very bad argument in itself, for reasons I would be happy to expand upon if you consider yourself capable of following.....
c) You could NOT take 'bible truth' and mathematically prove it. I have some doubt that you have the ability to prove ANYTHING mathematically, and I am almost certain that you have no conception of what a rigorous mathematical proof actually entails.

If you always need more energy to approach the speed of light and not get there it doesn't matter if it is 1 mph under the speed of light or 1 mile mph over the speed of light. The point is using the speed of light as a limit is not rational. And yes people do try to prove their theory is correct by using mathematical symbolism and formula. You talk as if everything you believe is absolute and cannot be challenged --but I disagree thus far.

Disagreement is fine. However, if you attempt to make a scientific argument, then you need to have an understanding of the science involved, which includes the mathematics. If you don't have that understanding then your disagreement arises from ignorance, not from knowledge.

I may be stupid, however, can we not talk with reason instead of being mathematical genius's.

There is understanding the science and math as far as reason, and there is understanding of science and math for those who think it is absolute, and anything that wavers from that absolute is considered false. All I ever asked for was to do some reasoning here. But Oh well --you carry on in your world.
Bikerman
 Jthomasnaz wrote: There is understanding the science and math as far as reason, and there is understanding of science and math for those who think it is absolute, and anything that wavers from that absolute is considered false. All I ever asked for was to do some reasoning here. But Oh well --you carry on in your world.
This is yet more gibberish.
Science is empirical and therefore BY DEFINITION not absolute. All science is contingent upon observation/evidence - that is why science deals in THEORY and HYPOTHESIS. It is clearly understood that ANY theory is up for debate and can (and will) be changed in light of new evidence.

The problem YOU have is that you are ignorant of the basic theory but arrogantly and mistakenly think that your ignorance is actually reason.
What you need to do is to go away and spend a few weeks (at the very least) studying Special Relativity. Then you will need a longer period to get to grips with General Relativity. Only then will you be in a position to offer a coherent and reasonable opinion on the matter. Until then you are simply gibbering.

[MOD]
EDIT: Please do not post further responses to this, Jthomasnaz, unless you have something specific and relevant to the topic. I don't particularly care if you consider me 'snotty' - as I said previously science is not a democracy and ignorant option is worthless. Fortunately (or unfortunately, depending on your POV) these forums are not a democracy either, and I'm afraid that on this issue I must insist.
[/MOD]
PS - I am happy to provide links to material on Relativistic theory that would provide a basic education on the matter, but that would be a waste of my time unless you are prepared to put the necessary time into studying such material and, at the moment, I doubt this.