Thus my reference to Gallileo, but I think you got it.
look i know this is a little late...but i only just signed up to this forum. but to who ever asked
"I dont know alot about the topic but reading these threads, the theory states that nothing can travel at the speed of light! Why then can light, having mass, travel at these speeds. ??"
there is nuthing to say that we can not travel at the speed of light, the reason though for scientist to say that nothing can travel at the speed of light is due to "mass dialation". This is, mass increases with velocity, so at high speeds that tend to the speed of light, the mass dialation is so high that our or any other body can not deal with this increase in mass and will be crushed. So basicaly what i am saying is that when something travels at the speed of light it will pretty much implode.
this is the reason for scientist saying that nothing can travel at the speed of light.
Aidos, Welcome to A2K. I'm certain that someone here will be able to answer your query. Unfortunately, it will not be I.
I have vague memories of:
1) Light not having mass
2) Mass not increasing when speed increases, merely force(N) increasing (F= m * v ) or something like that
3) High school physics
4) High school
But I'm on vacation now, so I don't think you should rely on me (nor blame me for anything I said; I'd rather have you correct me
)
Quote:there is nuthing to say that we can not travel at the speed of light, the reason though for scientist to say that nothing can travel at the speed of light is due to "mass dialation". This is, mass increases with velocity, so at high speeds that tend to the speed of light, the mass dialation is so high that our or any other body can not deal with this increase in mass and will be crushed. So basicaly what i am saying is that when something travels at the speed of light it will pretty much implode.
Quote:this is the reason for scientist saying that nothing can travel at the speed of light.
yeah that makes sense. i wouldnt be surprised if one simply turned into light if they were to go that fast..
let me go back to the original question...
Quote:"I dont know alot about the topic but reading these threads, the theory states that nothing can travel at the speed of light! Why then can light, having mass, travel at these speeds. ??"
There is no theory that states that "nothign can travel the speed of light". the speed of light is simply the speed that an electromagnetic wave travels while in a vaccuum. Light is an electromagnetic wave, so that is it's speed. However, radio, microwaves, in fact, all electromagnetic waves ALL travel at "the speed of light"
in a vaccuum.
On Earth, we don't have many vaccuums...so certain waves are slowed down more than others depending on their wavelength.
The speed of light happens to be the highest possible speed that anything can travel.
Traditionally, we assume that velocities can be added.
AKA, if you are travelling in a train at 60 mph (u), and you start running in the train at 5 mph(v), then you are travelling 65 mph (u+v)...right?
NO, but close.
Your total velocity (w) is actually more complicated than just u + v
It has been measured that velocites actually add like so:
w = (u + v)/(1 + uv/c2)
A close look at this equation shows us that if the velocities being added are less than the speed of light, then they will almost exactly add. But what if the train was moving at speed c, and you ran at speed c...well then your total velocity would be c as well! Because you cannot go faster than c.
EDIT: by the way, light does not have mass. yes, light is composed of quantized particles we call photons...and yes photons have energy, so you might be tempted to use e=mc^2 and get yourself a mass value...however, that equation is actually wrong...the real equation is:
E^2 = m^2c^4 + p^2c^2
So if p(momentum)=0, then the equation simplifies down to e=mc^2...however, photons in light ALWAYS have momentum because they are always moving...we can measure that their momentum is actually h/lamba. This makes perfect sense because lamba=c/v and E= hv...so if you solve that, you will see that E=pc...which naturally falls out of the relativity equation if m=0.
Now the question is....is mass really zero, or is it just close enough to zero? there is evidence that it is actually zero, but that is beyond my learning at this point.
however, you can try reading this for an answer to that:
[quote]If the rest mass of the photon was non-zero, the theory of quantum electrodynamics would be "in trouble" primarily through loss of gauge invariance, which would make it non-renormalizable; also, charge-conservation would no longer be absolutely guaranteed, as it is if photons have vanishing rest-mass. However, whatever theory says, it is still necessary to check theory against experiment.
It is almost certainly impossible to do any experiment which would establish that the photon rest mass is exactly zero. The best we can hope to do is place limits on it. A non-zero rest mass would lead to a change in the inverse square Coulomb law of electrostatic forces. There would be a small damping factor making it weaker over very large distances.
The behavior of static magnetic fields is likewise modified. A limit on the photon mass can be obtained through satellite measurements of planetary magnetic fields. The Charge Composition Explorer spacecraft was used to derive a limit of 6x10-16 eV with high certainty. This was slightly improved in 1998 by Roderic Lakes in a laborartory experiment which looked for anomalous forces on a Cavendish balance. The new limit is 7x10-17 eV. Studies of galactic magnetic fields suggest a much better limit of less than 3x10-27 eV but there is some doubt about the validity of this method.[/quote]
stuh505 wrote:Quote:there is nuthing to say that we can not travel at the speed of light, the reason though for scientist to say that nothing can travel at the speed of light is due to "mass dialation". This is, mass increases with velocity, so at high speeds that tend to the speed of light, the mass dialation is so high that our or any other body can not deal with this increase in mass and will be crushed. So basicaly what i am saying is that when something travels at the speed of light it will pretty much implode.
This is false information. There is no such thing as mass dilation. Mass remains
constant regardless of velocity.
Actually this depends on which area of physics you are working in.
the universally accepted equation goes like this:
M=m * 1/
(1-
((v^2
)/
(c^2
)))
People who call the small m mass says mass does not dilate with velocity, people who call the bog M mass says it does. Both are correct.
The big M is the one that goes in the newtonian equation for acceleration:
A=F/M
or using the small m:
A=F/(m * 1/
(1-
((v^2
)/
(c^2
))))
The reason why nothing can move faster than the speed of light is that as velocity tends towards the speed of light the force required to maintain a given acceleration tends towards infinite. So at the speed of light, even with infinite force you would not accelerate.
The small m goes in the equation for gravity, so you wouldn't have a problem with collapsing.
Quote:Somehow you have got this very confused with
time dilation and
length contraction.
time dilation says that the faster you go, the slower time moves for you...and length contraction says that the faster you go, the shorter you will be to other people.
Quote:this is the reason for scientist saying that nothing can travel at the speed of light.
Well, obviously that's not the reason because that's not true...
let me go back to the original question...
Quote:"I dont know alot about the topic but reading these threads, the theory states that nothing can travel at the speed of light! Why then can light, having mass, travel at these speeds. ??"
There is no theory that states that "nothign can travel the speed of light". the speed of light is simply the speed that an electromagnetic wave travels while in a vaccuum. Light is an electromagnetic wave, so that is it's speed. However, radio, microwaves, in fact, all electromagnetic waves ALL travel at "the speed of light"
in a vaccuum.
On Earth, we don't have many vaccuums...so certain waves are slowed down more than others depending on their wavelength.
The speed of light happens to be the highest possible speed that anything can travel.
Traditionally, we assume that velocities can be added.
AKA, if you are travelling in a train at 60 mph (u), and you start running in the train at 5 mph(v), then you are travelling 65 mph (u+v)...right?
NO, but close.
Your total velocity (w) is actually more complicated than just u + v
It has been measured that velocites actually add like so:
w = (u + v)/(1 + uv/c2)
A close look at this equation shows us that if the velocities being added are less than the speed of light, then they will almost exactly add. But what if the train was moving at speed c, and you ran at speed c...well then your total velocity would be c as well! Because you cannot go faster than c.
That's one way to go about trying to explain it. The v in my equation is of course the velocity relative to the point of refference.
Einherjer,
I'm a bit clumsy in my head, and it looks like you replied to the un-edited version
yeah, mass does change with velocity...I was just thinking of rest mass...anyway I have already edited it hehe
Quote:
M=m * 1/(1-((v^2)/(c^2)))
what is this equation?
obviously it is using gamma from the lorentz transformations but havent seen that used for mass...brain is a bit fried now...
Quote:The reason why nothing can move faster than the speed of light is that as velocity tends towards the speed of light the force required to maintain a given acceleration tends towards infinite. So at the speed of light, even with infinite force you would not accelerate.
yes well...this is quite obvious when you look at the equation for velocity additoin which i just showed...but it does not really pertain to why regular matter could not travel the speed of light which was actually the question
Quote:The small m goes in the equation for gravity, so you wouldn't have a problem with collapsing.
what the heck are you saying...by small m it looks like in your equation you would be referring to the rest mass as opposed to the relativistic mass? well, you'd need to use relativistic mass for any kind of equations because that is the "instantaneous mass"...the rest mass is not useful for any calculations
I sort of explained it already, it is how you calculate "mass", as it goes in the certain newtonian equations from "mass" as read from tables velocity being 0. Some diciplines of science refer to M as mass, others refer to m as mass. This has resulted in a lot of laymenn getting very confused.
stuh505 wrote:Quote:The reason why nothing can move faster than the speed of light is that as velocity tends towards the speed of light the force required to maintain a given acceleration tends towards infinite. So at the speed of light, even with infinite force you would not accelerate.
yes well...this is quite obvious when you look at the equation for velocity additoin which i just showed...but it does not really pertain to why regular matter could not travel the speed of light which was actually the question.
Could anything reach the spead of light with mass tending towards infinite as the speed tended towards lightspead?
Quote:Quote:The small m goes in the equation for gravity, so you wouldn't have a problem with collapsing.
what the heck are you saying...by small m it looks like in your equation you would be referring to the rest mass as opposed to the relativistic mass? well, you'd need to use relativistic mass for any kind of equations because that is the "instantaneous mass"...the rest mass is not useful for any calculations
I'm sorry, I'm kind of groggy too. I meant to say that he should use the object moving at near lightspead as point of refference when calculating mass interactions. Easier that way.
I posted this in the black hole thread, but this one seems to be getting more action.
1. Due to the equations, we can not approach the speed of light (1-(v^2/c^2)) because you approach infinate mass.
2. The accepted theory of the universe is about 13.8 billion years old. . . yet
3. The accepted size of the universe is 100 Billion years across.
How is this possible? Assuming you are on one edge of the universe, the other end would be travelling faster then light. Does inflation ignore Einstein's thoeries? Is it possible to travel faster then light when dealing on a macro scale, but relativistic laws apply when dealing on a micro scale?
All of these questions are puzzling to me. Once we found out the universe was accelerating its expansion, it threw out all new rinckles. Any ideas guys?
Do you know how this width of the universe was arrived at?
Newtonian addition of velocities or distances could lead to this answer, but somehow I don't see scientists using newtonian physics for this kind of thing.
I don't think that the expansion of the universe itself involves motion in the usual sense, but rather an expansion of the continuum, of space itself, as opposed to travel through space.
Joe Republican wrote:I posted this in the black hole thread, but this one seems to be getting more action.
1. Due to the equations, we can not approach the speed of light (1-(v^2/c^2)) because you approach infinate mass.
2. The accepted theory of the universe is about 13.8 billion years old. . . yet
3. The accepted size of the universe is 100 Billion years across.
How is this possible? Assuming you are on one edge of the universe, the other end would be travelling faster then light. Does inflation ignore Einstein's thoeries? Is it possible to travel faster then light when dealing on a macro scale, but relativistic laws apply when dealing on a micro scale?
All of these questions are puzzling to me. Once we found out the universe was accelerating its expansion, it threw out all new rinckles. Any ideas guys?
I've figured it out. When shifting your point of reference to the edge of the universe you need to compensate for space distortion due to the motion of your new point of reference in relation to your old one. This will result in the width of the universe becoming less than CT. (T=age of universe, C= speed of light)
It's not a violation because it involves expansion of space, not motion through space.
Brandon9000 wrote:It's not a violation because it involves expansion of space, not motion through space.
It would not be a violation either way, unless the width of the universe comes out as more than 2CT, T being the time the universe has existed.
Quote:I posted this in the black hole thread, but this one seems to be getting more action.
1. Due to the equations, we can not approach the speed of light (1-(v^2/c^2)) because you approach infinate mass.
hmm...why would that be?
higher velocity means higher energy. but there would still be a measurable energy at the speed of light...photons have a measureable energy.
e^2 = m^2c^4 + p^2c^2
so by the equation, why would mass be infinite?
Quote:
2. The accepted theory of the universe is about 13.8 billion years old. . . yet
3. The accepted size of the universe is 100 Billion years across.
By the size of the universe, you mean the diameter of the debris from the big bang...but this is the same as the accepted age of the universe...around 15 billion not 100 billion
Quote:I've figured it out. When shifting your point of reference to the edge of the universe you need to compensate for space distortion due to the motion of your new point of reference in relation to your old one. This will result in the width of the universe becoming less than CT. (T=age of universe, C= speed of light)
no, this makes no sense
Quote:I don't think that the expansion of the universe itself involves motion in the usual sense, but rather an expansion of the continuum, of space itself, as opposed to travel through space.
no, the spacetime continuum is not getting bigger...the size of the universe represents the diameter of the mass expelled from the big bang and it's increasing at naturally (accelerating for some unknown reason)...and this also does not mean that the're can't be more matter outside of this universe that we cant see
stuh505 wrote:Quote:I posted this in the black hole thread, but this one seems to be getting more action.
1. Due to the equations, we can not approach the speed of light (1-(v^2/c^2)) because you approach infinate mass.
hmm...why would that be?
higher velocity means higher energy. but there would still be a measurable energy at the speed of light...photons have a measureable energy.
e^2 = m^2c^4 + p^2c^2
so by the equation, why would mass be infinite?
Elementary special relativity, discovered by Einstein in 1905 and taught daily in freshman college physics.
stuh505 wrote:Quote:I don't think that the expansion of the universe itself involves motion in the usual sense, but rather an expansion of the continuum, of space itself, as opposed to travel through space.
no, the spacetime continuum is not getting bigger...the size of the universe represents the diameter of the mass expelled from the big bang and it's increasing at naturally (accelerating for some unknown reason)...and this also does not mean that the're can't be more matter outside of this universe that we cant see
At:
http://www.science.ca/askascientist/viewquestion.php?qID=1254
Quote:The Big Bang event was not an explosion which occurred within a large, empty space. Rather, the Big Bang was the initial unfolding of space and time. All parts of the Universe were participants in the Big Bang event.
When we talk about the expansion of the Universe as revealed by the recession of galaxies, it is space which is expanding and carrying the galaxies along with it, and not the galaxies which are 'really' moving through space. Hence, there could in principle be galaxies beyond the edge of the observable Universe which are apparently receding at a speed in excess of the speed of light. We could not see them, of course, and because they are not traveling through space faster than c the fundamental principles of Special Relativity are not violated.
By the same token, at or immediately after the Big Bang, all the matter in the Universe was tightly confined but so too was space and time. The scale of the Universe in all respects differed from what it is now, and there was no 'outside'. An hypothetical observer inside -- as all observers must be unless we live in a higher dimensional hyperverse -- would see an unfolding of space and time as we do, with matter carried along in the spacetime continuum, and would observe nothing that contradicts the principles of Relativity.
Well, I had a discussion with one of the top astrophysicits in the world yesterday and his answers were both great and puzzling.
First, the universe is expanding beyond our event horizon. I got the age correct, but the "distance" across was incorrect. The distance currently calculated is 10^21st light years across (yep, that's one QUINTILLION light years across 1,000,000,000,000,000,000,000).
Now, this does not violate relativity on the cosmic sense because of inflation. The expansion of the universe is accelerating, because space is "increasing" between the outer ends of the universe. I use the word "increasing" loosely because we don't know why this increases. According to relativity, these points are outside the observable event horizon, therefor we don't know they exist and they don't violate relativity. On a macro-cosmic scale, they are accelerating past the speed of light (in reference to each other) but because at the reference point, the other end is not observable, it is not in violation of relativity.
He also mentioned something which really got me thinking. He mentioned that every 10^113 years, there is the probability of empty space, devoid of nothing, spontaneously producing a big bang. He mentioned something way over my head, but it had something to do with a negative particle.
Now, this leads me to a few follow up questions I asked him.
1. As time progresses, and inflation occurs, do galaxies on a cosmic sense pass beyond our event horizon? (the event horizon of the universe is the observable universe 13.8 Billion years across) If these galaxies do pass beyond our event horizon, how would the galaxy appear to an observer as it passes beyone the event horizon? Would it just disapear or fade? What would the observation look like?
2. Is there a way to measure the universe outside the event horizon? I know there is nothing physical which can pass from the outside to the inside of the event horizon, but can we observe anything outside the horizon? Are there any theories which postulate a way to measure or observe something beyond our event horizon.
3. The cycle of the universe seems to go as follows, big bang, expansion, inflation, empty space devoid of nothing, another big bang. Is this correct?
4. If all of #3 is correct, AND we have a way of measuring beyond the event horizon, could we theoretically find the remanence of other universes created by other big bangs?
If anyone has anything to add, any contradictions to my above statements and or questions, please feel free to discuss. This is one of the great things about science, no matter how much you think you know, you really know so little on the grand scheme of things.
One of the benefits of my job (designing x-ray, EUV and UV telescopes for satellites) is that I get to work with some of the worlds top astrophysicits. Every once in a while I get to pick their brains. Yesterday, we had a fire drill, so we were all outside and I was lucky enough to have some free time to ask him questions.
stuh505 wrote:Quote:I posted this in the black hole thread, but this one seems to be getting more action.
1. Due to the equations, we can not approach the speed of light (1-(v^2/c^2)) because you approach infinate mass.
hmm...why would that be?
higher velocity means higher energy. but there would still be a measurable energy at the speed of light...photons have a measureable energy.
e^2 = m^2c^4 + p^2c^2
so by the equation, why would mass be infinite?
Einherjar explained it earlier.
einherjar wrote:
Actually this depends on which area of physics you are working in.
the universally accepted equation goes like this:
M=m * 1/(1-((v^2)/(c^2)))
People who call the small m mass says mass does not dilate with velocity, people who call the bog M mass says it does. Both are correct.
The big M is the one that goes in the newtonian equation for acceleration:
A=F/M
or using the small m:
A=F/(m * 1/(1-((v^2)/(c^2))))
The reason why nothing can move faster than the speed of light is that as velocity tends towards the speed of light the force required to maintain a given acceleration tends towards infinite. So at the speed of light, even with infinite force you would not accelerate.
The small m goes in the equation for gravity, so you wouldn't have a problem with collapsing.
As velocity approaches the speed of light, the denominator of the equation approaches zero, hence the M approaches infinity. Just do a limit problem as v -> infinity to see the answer.
