Teej
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As time slows as something approaches the speed of light, and, the speed of light is the speed of a photon, it would make sense that time has essentially stopped if you're a photon.
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fried diode
- Thread starter xirrious
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As time slows as something approaches the speed of light, and, the speed of light is the speed of a photon, it would make sense that time has essentially stopped if you're a photon.
IsaacT
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Here is the thing, I don't believe time has actually stopped. Rather, I think you are travelling along the same vector as the light data showing whatever situation occured when you launched. Since those particular light packets neither go faster or slower than you, you will keep viewing the same moment in time until you stop or what have you. Its a perspective thing, IMO. If you then turned around and travelled at the speed of light back where you came, you would see all the light data for the time that had passed zoom by you much quicker than actual events. But when you arrived back, exactly as much time would have passed there as the time you took up flying at the speed of light. So no time was changed. Merely an illusion due to the changed interaction with light.
Just my thoughts on the matter after a lot of thinking.
Just my thoughts on the matter after a lot of thinking.
Teej
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As the laser's light is definitely heading out to the stars when pointed at them from here (Earth...), I don't think we're on the same clock in that way...but, if time-space is the way its supposed to be (Or the GPS computers would not have to compensate, etc...) then the reality for the photon itself, would be that time stopped...or, perhaps, that the photon is not aging....
...At least, if all that's written about astronauts who are away for 100's of years in earth time, return to earth barely a few years old, etc....is the way it would really happen.
IsaacT
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I just don't think that is what would really happen. I know there are a lot of much smarter people behind these theories than me, but in my mind it just doesn't quite make sense. When we have actual evidence I will be glad to accept it as a truth. Or, if a scientist is willing to chat it out with me.
Teej
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The MAIN reason I see it as maybe being valid, is that the companies that design/deploy the GPS satellites, etc, and need to interpret the time signals to help your gps find where it is on the ground...actually found they needed to account for this phenomenon in their calculations for it to work best.
That means there's something to it at least.
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For a theory[1] to be valid, it is required to have predictive power. That means that a valid theory must have the power to mathematically predict phenomena before their actual discovery. Relativity satisfies this criterion, here are some phenomena it predicted:The MAIN reason I see it as maybe being valid, is that the companies that design/deploy the GPS satellites, etc, and need to interpret the time signals to help your gps find where it is on the ground...actually found they needed to account for this phenomenon in their calculations for it to work best.
That means there's something to it at least.
1) the mass increase of accelerated particles (any object approaching the speed of light increases its mass)
2) the lifetime increase of accelerated unstable particles (time slows down for any object approaching the speed of light)
3) clocks slowing down when accelerated or placed near a concentration of mass (it's not just speed that slows down subjective time, but gravity too)
Just because a concept "does not make intuitive sense" to someone, it does not mean that it's wrong. It's only wrong if it leads to predict the wrong outcome, or even worse, if it does not allow any prediction to take place. But if it gives the right results and it "does not make intuitive sense", that is not a statement about the theory. That is just a statement about a single person's intuition, which just happens to be wrong because it is based on an incorrect mental model of the world.
For example, at the time of Isaac Newton, gravitation "did not make intuitive sense" because the scientific model of the time attempted to reduce all physical interactions to collisions, and yet Newton's formulae let astronomers predict how other planets would move.[2]
It's important to stress this point: that scientists could obtain results about a phenomenon before actually observing it (a priori).
[1] A theory is an explanation of a fact. Which means: something exists, and here is how it works. For example, the "theory of microprocessors" explains how microprocessors works, it does not question their existence.
This is different from the popular, incorrect usage of the word "theory" to mean "something for which there is no proof". In reality, something for which there is no proof is a conjecture.
[2]The only exception was Mercury (its perihelion precession was greater than what Newton's formulae predicted), but lo and behold, when the calculations were corrected with Einstein's formulae, the result were just right. In this case, Einstein's theory had obtained a further demonstration, a posteriori.
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Teej
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I agree.
I think the concept of "it not making sense" is more about trying to wrap one's head around the idea that someone could fly off in a spaceship at age 40, when you are also 40, and return when they are 45 and you have been dead for a few hundred years, etc.
There IS evidence that this is true, but, it IS a rather bizarre idea to internalize as rational.
IE: Not getting it doesn't make it wrong, it means its hard to understand in a way that correlates with ones life experiences, etc.
So we have:
1) the mass increase of accelerated particles (any object approaching the speed of light increases its mass)
So WHEN the particle reaches the speed of light, it's mass increases. A photon is traveling at the speed of light, so it should have mass. This might be where energy becomes matter.
2) the lifetime increase of accelerated unstable particles (time slows down for any object approaching the speed of light)
So a photon traveling at the speed of light has time stopped?
When they talk about "the clock slowing down", so far, the examples were essentially real clocks.
3) clocks slowing down when accelerated or placed near a concentration of mass (it's not just speed that slows down subjective time, but gravity too)
The GPS signal timing is mass correction. More mass = slower time.
So, to put it all together, the stuff going the fastest we know of, have no mass, despite that they should gain it by achieving light-speed (Or being it?)
On the other hand, they have momentum, and can be deflected by gravity....which implies mass.
So, perhaps they have no mass if you could put them on a scale, but, as you can't weight it at rest, it must be balancing between matter and energy as it continually holds the light-speed limit.
We also know its speed is not the same in different media, so, it doesn't turn to matter when shot into a bowl of jello, etc.
Its speed is relative to something (something I have no clue about), but, if it has momentum and energy, there's some (Small) lets call it "Mass-Like" affect.
Momentum is normally mass x velocity.
It seems to me that to TELL something has momentum, you'd need it to do something when interacting with some sort of resistance, and the ability to overcome/succumb to that resistance would be the indication of the momentum.
So, we do know how much light is deflected when it goes by a star or planet, etc, so, if we know the mass of the body that has the deflecting effect, we should be able to calculate the "mass-like" aspect of the light, as, we know its speed at least in space.
I'm sure someone has figured out how to measure this, and there's a "mass" of some sort calculated from it.
So, they boil it all down to gravity being a distortion of the fabric of time-space, so things "roll down into the depression" created by mass on that fabric.
Its heady stuff for sure.
So, I am aware that there are enormous gaps in what I know, so, I try not to close my mind to things that, on the surface, seem far fetched. I look for shadows cast by vast bodies of information that might be cast across my path, and, that tells me they are there...even if I can't see them directly.
Edited -
I just did a quick math-like check, and the angle of deflection is equal to 4 times the mass at distance r, all divided by r times c squared....(Ain't google cool)
I think the concept of "it not making sense" is more about trying to wrap one's head around the idea that someone could fly off in a spaceship at age 40, when you are also 40, and return when they are 45 and you have been dead for a few hundred years, etc.
There IS evidence that this is true, but, it IS a rather bizarre idea to internalize as rational.
IE: Not getting it doesn't make it wrong, it means its hard to understand in a way that correlates with ones life experiences, etc.
So we have:
1) the mass increase of accelerated particles (any object approaching the speed of light increases its mass)
So WHEN the particle reaches the speed of light, it's mass increases. A photon is traveling at the speed of light, so it should have mass. This might be where energy becomes matter.
2) the lifetime increase of accelerated unstable particles (time slows down for any object approaching the speed of light)
So a photon traveling at the speed of light has time stopped?
When they talk about "the clock slowing down", so far, the examples were essentially real clocks.
3) clocks slowing down when accelerated or placed near a concentration of mass (it's not just speed that slows down subjective time, but gravity too)
The GPS signal timing is mass correction. More mass = slower time.
So, to put it all together, the stuff going the fastest we know of, have no mass, despite that they should gain it by achieving light-speed (Or being it?)
On the other hand, they have momentum, and can be deflected by gravity....which implies mass.
So, perhaps they have no mass if you could put them on a scale, but, as you can't weight it at rest, it must be balancing between matter and energy as it continually holds the light-speed limit.
We also know its speed is not the same in different media, so, it doesn't turn to matter when shot into a bowl of jello, etc.
Its speed is relative to something (something I have no clue about), but, if it has momentum and energy, there's some (Small) lets call it "Mass-Like" affect.
Momentum is normally mass x velocity.
It seems to me that to TELL something has momentum, you'd need it to do something when interacting with some sort of resistance, and the ability to overcome/succumb to that resistance would be the indication of the momentum.
So, we do know how much light is deflected when it goes by a star or planet, etc, so, if we know the mass of the body that has the deflecting effect, we should be able to calculate the "mass-like" aspect of the light, as, we know its speed at least in space.
I'm sure someone has figured out how to measure this, and there's a "mass" of some sort calculated from it.
So, they boil it all down to gravity being a distortion of the fabric of time-space, so things "roll down into the depression" created by mass on that fabric.
Its heady stuff for sure.
So, I am aware that there are enormous gaps in what I know, so, I try not to close my mind to things that, on the surface, seem far fetched. I look for shadows cast by vast bodies of information that might be cast across my path, and, that tells me they are there...even if I can't see them directly.
Edited -
I just did a quick math-like check, and the angle of deflection is equal to 4 times the mass at distance r, all divided by r times c squared....(Ain't google cool)
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No. A material particle can never reach the speed of light. But as it approaches the speed of light, its mass increases. How much it increases, it depends on its speed. If you want to know how much it increases, there is a calculator here. Try inputting different velocities, and you will notice that the effect is not linear: at 200000 km/s (light speed in a vacuum being 299792.458 km/s) the mass increase factor is only 1.34, but as you approach the speed of light, the effect becomes bigger and bigger (1.81 at 250000 km/s, 3.94 at 290000 km/s, 13.76 at 299000 km/s, 40.27 at 299700 km/s and so on).
Calculations show that, if a material particle could reach the speed of light, its mass would become infinite, but in order to get there, it would need an infinite amount of energy, because the more mass it has, the more energy it is needed to accelerate it further.
No, a photon has zero mass. You can multiply zero by any number you want, and you'll always get zero.
Yes. If we could mount a clock on a photon, that clock would remain still. Conversely, if we could ride a photon ourselves, we would experience the entire history of the universe, from the present to the end, in a single instant.
Right.
No, for the reason I explained before. If it starts with zero mass, you can multiply it by any factor you want and it'll always be zero.
Photons don't have momentum, but gravity still influences them because gravity curves space. If you have two masses (like two stars in a binary system) they can orbit each other, or even fall into each other, because each mass curves its surrounding space, and each mass is influenced by the curvature caused by the other. But if you have one star and a photon, the photon will still be deviated by the star because the mass of the star still curves space.
And if the star is sufficiently massive to be able to collapse below a certain radius (the exact formula is r = (2*G*m)/c^2, where G is the gravitational constant, m is the mass of the object and c is the speed of light in a vacuum ), a region will form where space is so curved that it closes back into itself, so that anything entering that region will be unable to escape (and if it has a mass, it will eventually crash into the collapsed star). That is a black hole.
What matters is the speed of light in a vacuum, which is always the same no matter the environment one is in to measure it. That is what we call c.
In reality, saying that "light slows down when it passes through a different medium" is not precise. If you could see a photon while it travels through a piece of glass, you would see it moving in the vacuum between the atoms at a speed of exactly c. Then, when it collides with an atom, the atom would absorb it. After a short interval, that atom would emit another photon, which would again travel at c in the vacuum between the atoms, until it touches another atom, which absorbs it, then emits another photon after a short time... and so on. If you add up all intervals between an absorption and an emission, you get the impression that photons have slowed down, but they haven't. The photons that come out of a piece of glass are not the same photons that went in.
No, here you're just confused. Light has no momentum. As you say, momentum is mass*velocity, but photons have 0 mass, so 0*c means that they have a momentum of 0 kg*m/s.
Energy can turn into mass and viceversa, but for that, it's not necessary for light to have mass. In fact, energy and mass turn into each other every time a reaction (chemical or nuclear) takes place. If you burn something and you weigh (with a normal, kitchen-grade scale) the products before the reaction and after the reaction, you would be under the impression that the weight has not changed, but only because the scale you used was not precise enough to notice the change. Use a scale that is precise enough and you'll notice that after the reaction, a tiny amount of mass will be missing. How much? Exactly the equivalent of the energy that was liberated by the fire, which can be calculated with the famous formula: E=m*c^2 (or, if you want to calculate mass, m=E/(c^2) ).
This, by the way, is also why matter and antimatter annihilate: because the reaction between matter and antimatter is so energetic that the entire mass of the reagents is consumed when energy is liberated (in that specific case, as gamma rays).
No, as I explained, light doesn't need to have mass for that. Stars and planets have mass, so they curve space, so anything (it doesn't matter what it is) passing nearby will naturally follow a curved trajectory.
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Teej
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Hmmmm
OK, a photon is considered to be a particle and a wave (But not a desert topping...), so, when its a particle, it is traveling at the speed of light, so, a particle CAN reach the speed of light, because it IS light in this case.
I agree that at rest, a photon has no mass, but, in motion, its got a mass-like aspect to it.
As gravity IS the warping of that time-space fabric, and what makes things follow the curve created by a mass, etc...that IS what momentum is defeating, or trying to, etc.
We can plan a space ship trajectory to take advantage of this, to sling shot us off into another region of space, and, we can bend light the same way...
...its the same time-space effect.
So, as gravitational lensing "works" on light...gravity has an effect.
If gravity has an effect, then, there is mass....or, at least something that acts like mass.
Also, if you create matter from energy, it would not have to release energy, it could just release matter for example.
I know that the text books tend to call a photon mass-less, but, if its massless, then there has to be an aspect of it that is acting like mass for it to have momentum (E=pc) for example.
In empty space, the photon moves at c (the speed of light) and its energy and momentum are related by E = pc, where p is the magnitude of the momentum vector p. This derives from the following relativistic relation, with m = 0:[16]
E^{2}=p^{2} c^{2} + m^{2} c^{4}.
The energy and momentum of a photon depend only on its frequency (ν) or inversely, its wavelength (λ):
E=\hbar\omega=h\nu=\frac{hc}{\lambda}
\boldsymbol{p}=\hbar\boldsymbol{k},
where k is the wave vector (where the wave number k = |k| = 2π/λ), ω = 2πν is the angular frequency, and ħ = h/2π is the reduced Planck constant.[17]
Since p points in the direction of the photon's propagation, the magnitude of the momentum is
p=\hbar k=\frac{h\nu}{c}=\frac{h}{\lambda}.
/\ /\ /\
Pasted from wiki on photons, showing they do have momentum
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xirrious
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Photons themselves according to general relativity do not travel through time. Whoever it was that said that is correct. All is relative tho in including momentum vectors I.e. direction speed and mass.
Wannaburnstuff. .I see you like the theory. You got it a little mixed up though. I'll try to find a good link for you that explains everything better then I can.
Also the GPS timing corrections have NOTHING to do directly with mass
There is a negligible quickening of time as orbiting satellites are further from earth's center of mass. See relativity for why that matters. But the main reas on is they are travelling around 14000mph. That's fast enough to slow their atomic clocks relative to our clocks sitting on the ground.
Wannaburnstuff. .I see you like the theory. You got it a little mixed up though. I'll try to find a good link for you that explains everything better then I can.
Also the GPS timing corrections have NOTHING to do directly with mass
There is a negligible quickening of time as orbiting satellites are further from earth's center of mass. See relativity for why that matters. But the main reas on is they are travelling around 14000mph. That's fast enough to slow their atomic clocks relative to our clocks sitting on the ground.
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Teej
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xirrious
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Yes quite right you were!
IsaacT
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Yeah whenever you get a chance, hit me with the theories. I understand that there can always be forces at work that I have no knowledge of but for me, I have a very analytical mind, and I like things to make sense. When the click happens and all the information falls into place, that is always a nice moment.
xirrious
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I'm the same way and I've studied physics for yeara but still plenty i can't explain clearly. I could suggest some books? Ifor you'd like I'll just contact you privately for that
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I'm a little worried. I am waiting on a single part to finish a 405nm laser build in a C11 host. I have the driver set to " exactly " 700mA because the heat sink is so large, but don't want to lose my LD. Maybe I should set it back to the recommended current for the S06J 12X sled diode. I already lost one diode to this build because the heat sink is too close to the pill where I heat sinked my driver and shorted the thing out. The driver is okay, though.
xirrious
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A friend told me 405nm diodes are sensitive I've fried two so far it doesn't take much. I'd turn the current down a tad. To be on the safe side that is. If I was you.
