Naked Science Forum
On the Lighter Side => New Theories => Topic started by: RobotGymnast on 29/02/2008 23:05:25
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People like Albert Einstein and Stephen Hawking are revered by scientific communities, and whole lives are based on validating or continuing the things they have done, but these formulas, like E=MC squared, have some very odd flaws. First of all, the speed of light is not constant, light slows down (shown by black holes and how they can bend light towards them or make it change direction), but yet it is still used as a constant.. which speed of light do you use, who's to say which speed is 'natural'? Also, I find the idea that he seems to have almost arbitrarily used the speed of light laughable.
Sight is our most relied-upon sense. If you went deaf, you could find your way to work and live your life pretty well still. If you went blind, you'd have to make far more adjustments. Because of this, light is seen as a very important thing, which explains why it was involved in such formulas, and also why black holes are seen as so mysterious (because they nullify our ability to see them, which makes them amazing and interesting). Just because something nullifies one sense, that we could just as easily have not evolved with, does not mean it has the ability to bend space-time or rip time or manipulate these things otherwise. Why not E = M * speed of 1998 olympic gold medalist for 100 metre-dash? That's just as self-absorbed.
Also, how can space and time be intertwined so that manipulating one manipulates the other? I accept that time is another dimension, but if you shorten the width of something, do not its depth and height remain unchanged? Why should manipulating spacial amounts in any way mess with time?
Thanks, Teh Robot
P.S. Please try and make your answers as simple as possible without leaving out details.. I'm barely 15, so please keep that in mind when typing out an essay answer [;)]
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The notion that we are talking about the speed of light is arbitrary. What we are actually talking about is the maximum speed at which information can travel in the universe. As you rightly say, light can travel slower than this speed, it just cannot travel faster than this. But what is true of light is also true of radio waves, or even gravito-magnetic waves. It is in reality true of anything whatsoever, but it is simply that some things (like light, radio waves, gamma rays, gravito-magnetic waves) can in some circumstances actually reach this speed limit, whereas other things (electrons, sound waves, etc.) will never reach that limit.
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OK, in very simplistic terms (and I'll probably be crucified for simplifying things so far, but you wanted it simple), let us look at the relation of time and length.
If you are travelling by motor car, and it takes to 5 minutes to travel between two towns that are 5 miles apart, then you are travelling at 50mph.
Now, if it takes you 4 minutes to travel between those two towns, then you have a number of possibilities:
1) you have sped up to 75mph.
2) the towns have moved closer together, and are now only 4 miles apart.
3) your clock is slow, and time has stretched out, so that what was 5 minutes is now only 4 minutes.
If one now says that your car is not capable of going faster than 60mph, then we can discount the first possibility; so one is left with the other two possibilities. Either the owns have moved closer together, or time has stretched out.
As it happens, depending on your perspective, you may claim one to be true or that the other is true. OK, the speed limit on your car is not actually 60mph, but actually 186,000 miles per second; but as you get close to that speed, the people inside the car will see the towns moving closer together, whereas people on the outside will claim that the clocks the people inside the car are using are running slow (but it is not just mechanical clocks, but all aspects of time, from human ageing to the rates of chemical reactions, or any way in which one can measure time).
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I got confused reading that! [???]
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OK, in very simplistic terms (and I'll probably be crucified for simplifying things so far, but you wanted it simple), let us look at the relation of time and length.
If you are travelling by motor car, and it takes to 5 minutes to travel between two towns that are 5 miles apart, then you are travelling at 50mph.
Now, if it takes you 4 minutes to travel between those two towns, then you have a number of possibilities:
1) you have sped up to 75mph.
2) the towns have moved closer together, and are now only 4 miles apart.
3) your clock is slow, and time has stretched out, so that what was 5 minutes is now only 4 minutes.
If one now says that your car is not capable of going faster than 60mph, then we can discount the first possibility; so one is left with the other two possibilities. Either the owns have moved closer together, or time has stretched out.
As it happens, depending on your perspective, you may claim one to be true or that the other is true. OK, the speed limit on your car is not actually 60mph, but actually 186,000 miles per second; but as you get close to that speed, the people inside the car will see the towns moving closer together, whereas people on the outside will claim that the clocks the people inside the car are using are running slow (but it is not just mechanical clocks, but all aspects of time, from human ageing to the rates of chemical reactions, or any way in which one can measure time).
you're making a strange set of assumptions. Firstly, who says light can travel at the maximum possible speed for anything?
Second, if my car were to speed up (the first selection), then that does not necessarily validate one or both of the others. You're using the theory I'm inquiring about as an explanation. Just because I'm moving faster does not mean I see things moving closer together, it just means they get closer faster (simultaneously, things behind me would move away faster), so it would not look like they were moving closer together. (Likewise, moving the towns closer together would not increase my speed).
Same basic arguments go for the time thing, so I'm not gonna retype it. You're right by saying "see" and "claim", it would appear this way IF you didn't know the car's speed had increased, but they still are the same distance apart. So is that what that entire theory states? That if you increase speed or decrease distance, the other appears increased/decreased to it? That seems like it shouldn't have taken a famous scientist to figure out [???].
Also, what's the idea behind that if you approach the speed of light, you become infinitely dense? And how does E=MCC work?
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Robot G first up, you do not seem to understand how science works. Einstein did not just invent his expressions and persuade other people that he was right. He developed the theories of relativity by firstly assuming that the laws of physics are the same if you move from one place to another or look in any direction (a reasonable assumption)together with newtons laws of motion (these had been observed and confirmed for hundreds of years) and the observation (The Michelson Morley experiment)that the velocity of light in a vacuum always came out to be the same value whichever way you are travelling. This experiment was one of the most significant negative experiments in history. everyone was expecting to be able to measure the speed of the earth through "the aether" which is what light was supposed to travel through. When the answer came back that we were always standing still even though it was obvious that we weren't ie the earth goes round the sun at around 18 miles a second! this made everyone stop and think.
When he worked it out he realised we must exist in a four dimensional space-time universe where space and time are all linked together. looking at the energy of moving bodies where the kinetic energy is the mass times the velocity squared the fact that the energy of a mass was the speed pf light squared just drops unexpectedly out of the equations
read it up in wikipedia if you want to know more
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you're making a strange set of assumptions. Firstly, who says light can travel at the maximum possible speed for anything?
Are you asking who say's light can travel at 2.99792458 m/s (approx 186000 miles per second), or who says says 2.99792458 m/s is the maximum speed for anything.
To the first question: light has been measured to travel at 2.99792458 m/s, so we know it can travel at that speed.
To the second question: we have not measured anything that can travel faster than that.
Thirdly, if we assume that the above is true, there are certain consequent predictions that can be made, and these predictions have been shown to be true; thus reinforcing the belief that light can indeed travel at the maximum possible speed.
Second, if my car were to speed up (the first selection), then that does not necessarily validate one or both of the others. You're using the theory I'm inquiring about as an explanation. Just because I'm moving faster does not mean I see things moving closer together, it just means they get closer faster (simultaneously, things behind me would move away faster), so it would not look like they were moving closer together. (Likewise, moving the towns closer together would not increase my speed).
If you assume you can travel faster than the maximum speed, then you are correct; but all the experimental evidence suggests this is not possible, so the possibility of the car speeding up beyond the maximum speed is not a possibility that has been observed in nature.
At the beginning of the 19th they thought just as you do, that light should travel at different speeds in different circumstances. Yes, light can travel slower when travelling through a medium such as glass; but in no circumstances could they get it to travel any faster than the maximum speed, and in a vacuum, they could never get light to go slower either.
The first experiments assumed that since the Earth was moving through space (travelling around the Sun, and the Sun is travelling around the Milky Way, and the Milky Way is travelling along its own path through the cosmos), so when they looked into the sky, light ought to be appear to be travelling faster in the direction towards which the Earth was moving towards, and ought to appear to be travelling slower in the direction from which the Earth was moving away from. Yet, when they looked, they found that light appeared to be travelling at exactly the same speed no matter which direction they looked.
It was not a case that someone arbitrarily invented a theory that said light always travelled at a constant speed in a vacuum; but rather that contrary to the then current theories, experimental evidence showed that this was indeed the case, so they had to invent a new theory to explain that experimental evidence.
Once they invented the new theory, that theory made other predictions about how things ought to behave, in ways that the old theories would not agree with; and experimental observation then supported the new theory.
Also, what's the idea behind that if you approach the speed of light, you become infinitely dense? And how does E=MCC work?
In old fashioned Newtonian mechanics, the amount of acceleration an object undergoes depends on its mass and the force you apply to it - thus, if your car breaks down, and you have to push it, then the heavier the car is, the more effort you need to apply build up the same amount of acceleration in the car (this will be complicated in a real world car by frictional forces, but in a friction free world, if you apply a constant force to a car, it will keep accelerating at the same rate forever, and in theory at some time you will be able to keep accelerating the car until it was travelling faster than the speed of light).
If you get to a point where you say that even in a friction free world, this car cannot be accelerated any faster, no matter how much energy you apply to it, then this is equivalent to saying that at this point you car has infinite mass, since a car of infinite mass cannot be accelerated no matter how much force you push it with.
As for E=mc2 (MCC is the Marylebone Cricket Club [;D]) - when Einstein first worked out his equations (actually, they were not originally his equations, which is why they are known as the Lorenz Transform, but people like Poincaré and FitzGerald also came to a similar formula, and there is much debate as to who came up with it first), he came to the conclusion that even when an object had absolutely no velocity at all, it still had an energy value of mc2. This was then regarded as the rest energy of the mass. At first this was just regarded as an idiosyncracy of the equations, and nobody thought that anything useful could be made of this energy; but then when experimenters such as Rutherford started to split the atom, they found that the sum of the masses of the fragments of the atom after it was split was not the same as the original mass of the atom (the difference was very very small, but it was measurable). They also found that when the split the atom, energy could be released in the kinetic energy of the fragmentary particles, and it turned out that the energy they released was equivalent to the loss of mass of the fragments, if they used the equation E=mc2 - and so demonstrating that this little quirk of the original equations had real meaning in the real world.
If the equations Einstein had been using were wrong, then nobody could have explained how the loss of mass when they split the atom could create energy, but not only did Einstein's equations explain how the two related, but they could numerically predict how much loss of mass would create how much energy.
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I got confused reading that! [???]
I suspect the problem is that you know the complicated (i.e. with lots of scientific shorthand) version of relativity, and so the simplistic, long winded (and still skipping some of the nuances), explanation for someone who does not know all the scientific shorthand looks very confusing to you.
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..just because nothing faster has been measured, it's considered the maximum speed? That's terrible rationalization! (No offense).
Okay, so if I concede (good work on that.. it's hard to get me to concede anything) that at infinite mass, whatever you're pushing can't be accelerated, and I assume for now that the speed of light is the maximum speed of anything, that still doesn't mean that anything traveling at the speed of light has infinite mass, because multiple factors determine whether or not something can be accelerated.
Okay, so E is the amount of energy an object contains when it's not moving? Or its potential energy, or what?
Wait, when you split an atom, aren't all the particles inside it just separated from eachother? I was under the (apparently false) impression that the energy released was the energy from the bonds being broken.
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Light always travels at C under all circumstances.
Light may appear to slow down whilst travelling through certain medium but in reality it nothing more than an illusion.
First of all, the speed of light is not constant, light slows down (shown by black holes and how they can bend light towards them or make it change direction), but yet it is still used as a constant.
Blackholes and their gravity have no effect on the photon it doesnt slow it down ,it still travels at C . Gravity affects the fabric of space bending the pathway that the photon is travelling along
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I consider that a very biased opinion. Please support it. If you can say that for light, you can really say that for anything. I always travel at the same speed, sometimes there's just stuff in my way.
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I consider that a very biased opinion. Please support it. If you can say that for light, you can really say that for anything. I always travel at the same speed, sometimes there's just stuff in my way.
You cant be absorbed and then re-emitted
Firstly I'm not an expert but from what I've learnt when light enter a medium such as air or any of the other experiments where they seem to slow down light all they are doing is performing an illusion. Light always under all circumstances travels at C
When light enters a medium such as air the photons are absorbed by the atoms making up the medium increasing their energy, but because the atoms cant remain in their high energy state they then lose the energy they have gained by releasing a photon. The slower the transition between absorption and emission of a new photon the slower it will appear that light is moving.
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The E in the Einstein equation is the energy tied up in the mass of the object potential energy in a gravitational or electrical field and kinetic energy associated with the motion of the particle are separate. potential gravitational energy is mostly associated with large objects on the earth's surface in most cases the total energy of a particle is its rest mass energy plus its kinetic energy. The kinetic energy of a particle also contains an expression in its velocity that goes to infinity as the particle velocity approaches the velocity of light that is as a particle approaches the speed of light its energy becomes infinite, looking at it the other way around you can put as much energy as you like into one atomic particle and you will never reach the velocity of light. these equations have been proved many times in colliders. That is why the velocity of light is the absolute maximum possible for anting to travel and the only things that can go at this speed have no mass like electromagnetic waves or gravitational waves.
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..just because nothing faster has been measured, it's considered the maximum speed? That's terrible rationalization! (No offense).
It is not just that nothing faster has been measured.
The key points are that in circumstances where one would have expected light to travel faster than it did, it obstinately refused to do so.
Ofcourse, science is only ever about dealing with information that one knows. It is always conceivable that tomorrow someone will be able to demonstrate that something can travel faster than light.
The point is that the theories, as they stand, make predictions, and those predictions can be verified by experiment. It does not prove that tomorrow a better theory will not come along, but we can only work with what we have today.
You asked why people believe as they do. They believe as they do because they carried out the experiments they did, came up with the results they did, and had to create some sort of model to explain those results. If the day after tomorrow (I assume you wont have time to prepare to do this tomorrow [;)]) you can put in place an experiment that violates the present theories, then people will have to go back and think up new theories. That is how science works.
Okay, so if I concede (good work on that.. it's hard to get me to concede anything) that at infinite mass, whatever you're pushing can't be accelerated, and I assume for now that the speed of light is the maximum speed of anything, that still doesn't mean that anything traveling at the speed of light has infinite mass, because multiple factors determine whether or not something can be accelerated.
No - if something cannot be accelerated, the no matter what multiplicity of forces you have, you cannot accelerate it. No matter how many forces you have, the key issue is that the sum of all those forces represents a nett force acting on the object, and it remains that no matter what nett force applies to the object, you cannot make it accelerate once it has reached the speed of light.
Okay, so E is the amount of energy an object contains when it's not moving? Or its potential energy, or what?
Wait, when you split an atom, aren't all the particles inside it just separated from eachother? I was under the (apparently false) impression that the energy released was the energy from the bonds being broken.
No, there is a measurable difference in the mass of the whole from the mass of the parts (it is a very small difference, but it is there). One can debate whether the mass comes from the mass contributed by the bonds, or a change in mass of the constituent parts themselves (I believe the consensus is the former, but for the purpose of the issue at hand, the difference does not matter).
I believe there are now a number of different experiments that can show that mass is not always conserved, but when mass changes, there is a change in energy that reflects the increase or decrease in mass.
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Okay, so if I concede (good work on that.. it's hard to get me to concede anything) that at infinite mass, whatever you're pushing can't be accelerated, and I assume for now that the speed of light is the maximum speed of anything, that still doesn't mean that anything traveling at the speed of light has infinite mass, because multiple factors determine whether or not something can be accelerated
No - if something cannot be accelerated, the no matter what multiplicity of forces you have, you cannot accelerate it. No matter how many forces you have, the key issue is that the sum of all those forces represents a nett force acting on the object, and it remains that no matter what nett force applies to the object, you cannot make it accelerate once it has reached the speed of light.
Sorry, I should've been more clear. I'll explain what I meant in pseudocode..
possible acceleration = yes;
if mass is infinite OR maximum speed attained OR [other conditions]
then possible acceleration = no;
the ORs are inclusive. I just meant that because one condition is true, it doesn't mean the others are true as well.
Okay, so E is the amount of energy an object contains when it's not moving? Or its potential energy, or what?
Wait, when you split an atom, aren't all the particles inside it just separated from eachother? I was under the (apparently false) impression that the energy released was the energy from the bonds being broken.
No, there is a measurable difference in the mass of the whole from the mass of the parts (it is a very small difference, but it is there). One can debate whether the mass comes from the mass contributed by the bonds, or a change in mass of the constituent parts themselves (I believe the consensus is the former, but for the purpose of the issue at hand, the difference does not matter).
I believe there are now a number of different experiments that can show that mass is not always conserved, but when mass changes, there is a change in energy that reflects the increase or decrease in mass.
Interesting... Now throw quantum physics into the mix with all those other possible dimensions from Timeline and you'll have scientists all over the world jumping off bridges =P
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Sorry, I should've been more clear. I'll explain what I meant in pseudocode..
possible acceleration = yes;
if mass is infinite OR maximum speed attained OR [other conditions]
then possible acceleration = no;
the ORs are inclusive. I just meant that because one condition is true, it doesn't mean the others are true as well.
I don't think I made myself clear.
It is not a case of "if mass is infinite OR maximum speed attained". It is a case of "If there is a maximum speed, then how is it enforced?". Making the mass go to infinite was considered the only feasible enforcement mechanism.
Furthermore, if this was not the right enforcement mechanism, then there would have been no reason to believe that mass could change at all, and so the equation E=mc2 would never have been invented, and so we would not have been able to validate the relationship between mass and energy when we split the atom. So, you see, the energy we get from splitting the atom actually does validate the theories we have about mass increasing to infinity as we approach the speed of light - the parts of the jigsaw fit together nicely.
Again, you will note that the equation E=mc2 includes the term c2, and ofcourse, c is the speed of light, so demonstrating that the equations inherent dependence on the speed of light (not some other speed) is valid. This dependency of the speed of light is a consequence of the way the equations also demonstrate that mass will be infinite when the speed of light is reached - it all fits together.
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But how does raising something to infinite mass make it move at infinite speed? Or are you saying that if something has infinite mass, it has the potential to move at the maximum speed?
Also, if the maximum speed is a finite number, shouldn't things below infinite mass be able to attain it? And what about photons? They travel at the speed of light, they define the speed of light; are they infinitely dense?
And isn't it possible that certain things have a maximum speed point, where others have different ones?
So you're saying that something of infinite mass has the capability to travel at the maximum speed, but if something accelerates towards the maximum speed, does its mass increase? Does that mean that the supposed singularity of a black hole travels at the speed of light?
Thanks
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But how does raising something to infinite mass make it move at infinite speed? Or are you saying that if something has infinite mass, it has the potential to move at the maximum speed?
Also, if the maximum speed is a finite number, shouldn't things below infinite mass be able to attain it? And what about photons? They travel at the speed of light, they define the speed of light; are they infinitely dense?
And isn't it possible that certain things have a maximum speed point, where others have different ones?
So you're saying that something of infinite mass has the capability to travel at the maximum speed, but if something accelerates towards the maximum speed, does its mass increase? Does that mean that the supposed singularity of a black hole travels at the speed of light?
Thanks
No, nothing can attain infinite mass - infinity is an impossibility.
What I am saying is that the greater the mass, the more difficult it is to accelerate to a higher speed. If something were to travel at the maximum speed, then it would have to attain infinite mass, so it cannot achieve the maximum speed. As it gets closer to the maximum speed, its mass increases rapidly, and as its mass increases, so it becomes ever more difficult to accelerate, so it cannot be made to go faster. As it is just below the maximum speed, and it cannot be made to go faster, it cannot actually achieve the maximum speed.
So the question is, why can light achieve the maximum speed - and the reason for that is that light has zero rest mass, so the increase in mass applied to a zero rest mass can avoid the problem of infinities. There is also another issue with light - it cannot ever be stationary (which gets out of the problem of how you can have something with zero mass, since that mass is really only its rest mass, and light is never at rest).
What happens inside a black hole is a much more complex issue, and as yet I don't think even the experts can quite agree about that. The easy answer is to say that a black hole has an event horizon which blocks out what really happens beneath it, so one can never actually know what goes on beyond the event horizon. The problem that is that Soul Surfer will come along and tell us that spinning black holes don't need to have event horizons. Then there is the problem that the very notion of a singularity, while looking fine in classical mechanics (if you are happy with infinities - which even classicists usually warn are an indication that something is not quite right), but quantum theorists like the idea of singularities even less. So I think the answer is that at present none of the current theories actually deal very well with what happens at the centre of a black hole; but since no-one has actually been inside a black hole to investigate (and probably never will), it is understandable that there is something of a lack of experimental evidence upon which to work out which theories are reasonable and which are not.
Science can only work by making experiments, testing out those experiments; looking at the results; making theories about why those results are as they are; using the theories to make predictions; and then creating new experiments to test out the predictions; if the experimental results match the predictions, then the theory is good (so far), but if they do not match the results, you have to go back and make a new theory. So far, the experiments with black holes have been notable by their absence, so it is very difficult to make good theories about them.
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alright thanks for your time