Question about the maximum speed of light and 'weight'

[porkop]

No one said it was easy to understand. Lol

[trash]

So if it has mass how can it travel at the speed of light?

Actually, it should be; "If they don't have mass how come they don't travel at the speed of light?"

First is that they always travel slower than "C" the speed of light.
Second is the mass is virtual. We might consider it to be 0+j1.

Remember that while the photon is are right angles to the gravitational field it is effected by it. Yet when aligned on the same axis as the motion of the photon it doesn't "accelerate it".

I'm not sure if it is correct to say that a photon gains or looses this virtual mass as if falls down a gravitational well.

Second: If it is now "They're carriers of mass or was that force?". If a wave, then what hits the eye?
It's known (as far as the tools we have!), that the human eye can detect 1 (ONE), photon.

Actually, the human eye can't detect single photons. They're not that sensitive

There are devices like PMT's which can detect single photons, and even... "half photons". Ha, you're going to say that doesn't make sense ! And you'd be right, but... this is the world of quantum physics, half of a photon can be in either of two places

What is detected by the eye is... Both. depending on how you look at it, so to speak. The answer you seek is described by "Photo Electrics".

2a) If it has energy then it has to have mass, no?

That appears to be the case with respect to the planck constant.
I'm not aware of any other particles known to have a zero mass.

[quote]And what about these Neutrinos - now found out that they have mass?[quote]
Yes they have mass. I learnt in high school that it was suspected they were massless and that photons had a rest mass. It's the neutrinos that have a rest mass and photons do not.

Neutrinos are the carrier of the weak nuclear force. Changing the neutrino flux can change how fast isotopes decay.

Who said (might have been Feynman), "If you can explain Quantum Mechanics, then you don't understand Quantum Mechanics".

Dunno, but I sure as hell don't have a firm grasp on it. The best thing I can suggest is that if you're prepared to constantly change your thinking it helps a little. Usually you will find two experiments to test a theory which oppose each other, yet both hold true. Like the double slit experiment we are all shown in high school.

... 2,476,873 are from Trashes IP...

Actually, I keep an eye on the second hand book shops. Some good books turn up from time to time. I just finished reading an old one I found from 1955.
It's quite interesting how it talks about the apollo missions in the future tense.
It has lectures from a number of professors (including Julius Sumner-Miller) on a variety of subjects. One of the subjects is cosmology, and it describes dark energy and universal expansion with some amusing clarity without even realising what it is they are describing.

[anyone]

(including Julius Sumner-Miller)

why is it so fame and other shows, loved his shows as a teen but this is too deep for me

[trash]

I'll see if I can scan some of his lectures

[gordon_s1942]

Way over my head but in another posting, there was a discussion of Light passing through a 'Medium' which from I followed caused the speed of light to be 'reduced/slowed down'.
To me once it 'slows down' it ceases to be light but if it managed to pass through this 'effect', to become light again how can it regain its speed without some sort of 'regeneration' occuring?
The only way I can follow this is to just look at Light as Energy and that another form of Energy (magnectic) can be used to cause the path of the other (light) to be diverted but it doesnt (I dont think) alter the origonal Energy's compostion.

[trash]

Oh I love questions like that.
Ok... rather than thinking of light slowing down in the medium, think of it more like a chain of events.

In free space the photon is crusing along through space-time, A happy little particle riding his quantum surfboard on his little light wave. Nothing can stop him in the vacuum of space and he's going flat stick, as fast as the wave can carry him.

Now he collides with a molecule of gas out in space and be damned if he didn't collide with an electron. Because the electron is so much much bigger, our little photon is annihilated in the collision like a quantum bug splat. But the energy he carried was enough to knock the electron into a higher orbit.

The electron doesn't like where he is, he wants to be back in his lowest shell (rest state). But he can't get back there without spending some energy, SO.... he emits just the right amount of energy to drop him back down into the lower orbit.
That energy is ... a photon ! It's the same photon as before. All his energy and momentum was conserved. (It's the law !)

So now our little photon continues on his way at the speed of light.

Now he comes to a sheet of glass .... as our photon starts to work his way through the glass he knocks electrons from their shells, and they remit the photon. Over and over and over again. This is going to slow things down.

A tennis ball thrown across free space move as fast as it is thrown.
But if it inside a big room full of people and the ball is passed from one person to another to travel across the room, it too is going to take a little longer.

Conservation of momentum is still required even at the quantum level.

[Strada916]

Can I ask this, now I know cars can not travel at the speed of light but here goes anyways

"A car traveling a the speed of light, has no lights on. It gets dark so he turns on his lights. Does he see in the dark?" Can a pedestrian see his lights coming towards him?

[trash]

No, a pedestrian cannot see him coming.

If you were standing on a street corner and this car travelling at the speed of light passed you, you would see .....

A bright flash of light (as the photon wavefront hits you like a sonic boom), then you would see the race race off backwards from the direction it came at a speed which might look like it was faster than the speed of light backwards.

The reason is that the photons from the car when it is beside you arrive first, the photons from a distance have to travel (hypotenuse) distance form their point of origin, so the further the car is away, it takes proportionally slightly longer for those photons to arrive. This is why the car appears to move backwards rather than forwards from the observer's point of view.

Now as for the driver's headlights. IF he's traveling slower than the speed of light, by even a tiny fraction, his headlights will appear to function normally apart from the massive blue shift
If he's traveling AT the speed of light his time frame is frozen, while the universe continues on as normal. To him, billions of years appear to pass in millisonds. (and that's a gross understatement).

[Arbiter]

So what happens if the pedestrian is carrying a torch and points it at the approaching vehicle with it's headlights on and the two light sources meet?
Would not the impact velocity of photons be 327000 miles per second ie twice that of the speed of light or more?
Would be an interesting experiment to conduct at your nearest synchrotron.
FYI: Synchrotrons, amongst other things, fire an electron through a magnetically guided circular course very close to the speed of light (think rail gun) and at the appropriate moment, if I'm not mistaken, deflect the electron which then emits a photon.
This photon is then also deflected and captured in a separate storage chamber.
It is 10,000+ times brighter than our sun.
It also has a life span of a few days before decaying to who knows what.
This intense light source is then used, for all intents and purposes, as a massive ultra-bright "flash bulb" which people then use to perform various experiments on specific matter at atomic/molecular level.
Check it out at

They were not impressed when I made the statements:
"Oh, I see you have a machine that goes BING" and described the facility as a very expensive example of demonstrating "What goes around, comes around".
"Many hands make light work" was also not appreciated by staff.

[trash]

Would not the impact velocity of photons be 327000 miles per second ie twice that of the speed of light or more?

I'm not even sure that photons can collide... But yes, that statement is correct, they do (would) collide at twice the speed of light. But don't confuse photons, with the subject of an observer.

Would be an interesting experiment to conduct at your nearest synchrotron.

And this is pretty much what particle colliders do, but not with photons.
A low energy collider which you could build yourself would collide electrons into electrons. The fragments are going to be rather basic.
But we want more energy in our collisions, so we accelerate electrons in one loop and collide them with positrons in the other loop. Now the energy levels are going to be ~500keV (from inhalation) plus the kinetic energy of each particle.

But we want MORE, Fermilab ! ... next we much collide protons with protons head on.
We make up for the extra momentum with mass rather than just trying to push electrons ever faster.

Step up the LHC ! To get the most out of our collider we smash protons into anti-protons. Or deuterons or Tritons or even iron ions into each other.

if I'm not mistaken, deflect the electron which then emits a photon.

You're not mistake, this is called Bremsstrahlung or Braking radiation.
It's mostly X-rays depending on the energy of the accelerator.

This photon is then also deflected and captured in a separate storage chamber.

Err... not so sure about that.
You might be confusing it with something else, but there isn't anything that 'stores' photons.

"Oh, I see you have a machine that goes BING" and described the facility as a very expensive example of demonstrating "What goes around, comes around".

Ah, no sense of humour !

When I was a young whipper snapper, on a tour of Lucas Heights we were asked, "Any questions ?"
Trash:"Yeah, can you irradiate this 20 cent piece for me ?"
Boffin:"Hey teach; keep an eye on this one... he's dangerous !"

[Uncle Fester]

If he's traveling AT the speed of light his time frame is frozen, while the universe continues on as normal. To him, billions of years appear to pass in millisonds. (and that's a gross understatement).

More like his infinite mass has just absorbed the entire universe and he will never notice it... if Einstein was right.

[dogknees]

[QUOTE=trash;419201]I'm not even sure that photons can collide... But yes, that statement is correct, they do (would) collide at twice the speed of light. But don't confuse photons, with the subject of an observer.

Photons don't interact directly with each other. As there can be no collision, asking what it's speed would be is meaningless.

[aktomkins]

I do believe that the photon is a massless particle and as such can not have weight so it can easily travel at the speed of light.

I do not know the reason why the mass increases as one approaches the speed of light, the dimention in the direction of travel shrinks and time has the apperance of slowing down to the outside observer.

Personally, i believe that the speed of light is a purpose barrier to prevent interstellar travel. The only communication between stars will only be via transmission means.

Time for trash to step in.

Doesn't light travel as a wave, not a particle?

Sent from my SM-T550 using Tapatalk

[lsemmens]

Back to the OP for a moment

But i can't 'see' why the weight increases?
I understand the mass increasing. But why weight?

The theory says that we can't achive full light speed, as the weight outlays the power required - and the faster you go - the heavier it gets and more power required, ad infinitum.

Mass is the only thing that increases and the energy expended to accelerate that mass is exponential. Weight is a product of gravity which is why you weigh less if you live on the moon. Never confuse weight with mass, two completely different things.

As atomkins has observed light is a "wave" and as it speed up or slows down it's colour changes so, light does not necessarily have a constant speed per se which is why we can determine the distance of a celestial body from us owing to "red shift". I do wonder if there is such a thing as super light speed as we still do not understand enough of how the universe is made to make such a wild claim that we can never exceed "C". Time was when we did not believe that we could ever leave this planet, or "see" through solid objects (Xrays). Only time will show which is a correct theory. Unfortunately, none of us are likely to live long enough to see it come to fruition.

[spook]

I reckon within the next 5 years they will discover energy forms which make light, to be one of the slowest things in our universe and transiting the universe is doe by dimensional shifts. They've got it wrong with the universes origins, black holes and they have it wrong in regard to stars and how they operate.

[gordon_s1942]

No doubt I will get killed for this but back further was a discussion on 'Cars' and lights etc and this thought crossed my mind (dont laugh),
If a car is traveling at the speed of light and big Blofly is sitting on the back window and decides to fly to the front windscreen, what speed is the Blofly flying at???

[lsemmens]

You aren't the only one to ponder that, gordon. What would happen if you opened the window to let him out?

[trash]

Newtonian and Relativistic physics. You live in and observe the Newtonian version of the universe which you share with everybody everywhere at the same time.
The relativistic version is your own personal personal universe. The center of your universe is you. So I can observe one thing and see it one way and you can observe it at the same time (from a different location) and see something different and yet the two versions of the universe do not conflict because they are relative to the observer.


How about helium balloons in a car Gordon, you hit the brakes and the balloon goes flying towards the rear window !

[gordon_s1942]

I think we all have a few relatives we wonder about at times..............but whether their Newtonian, Realistic or Personal I cannot tell.

Dont you just hate these blokes whose shirt cuff buttons are smarter than you'll ever be and pose questions you know you'll end up with egg on your face when trying to answer it !!

[trash]

It's an exponential curve Gordon, there are people that are towers above me that I love to question to get answers or on rare occasions, stump them.
Science is something everybody can do. You'll notice that ever time Tytower makes an appearance I give him a clean slate. I have infinite tolerance for his questions. I have none for ignorance.

Last weekend I was out at Siding Spring observatories. It's a lot of fun being able to milk smart people for information and trying to suck them dry.
The rules apply equally to everybody. "There is always somebody smarter than me."