# Faster than light

Arthurwerbrouck
I stumbeld upon a wikipedia page called faster then the speed of light
https://en.m.wikipedia.org/wiki/Faster-than-light
And if you look at 3.1 it seems to be prooven
Could someone with knowledge of the topic explain this to me and tell me al about it

Arthurwerbrouck
Mentor
And if you look at 3.1 it seems to be prooven
No.
The first question is "what type of velocity do we measure?". Take a laser pointer, point at the moon and rotate it fast enough: the dot of the pointer can easily "move" from one side to the moon at a speed faster than the speed of light. That is not the speed of any real object, however, and it cannot be used to transmit information from one side of the moon to the other at this speed.

The true limit applies to signal speed: how fast can an event at place A influence an event at place B? None of the experiments discussed there found superluminal effects here.
Just nonsense.

SapientiaPT and vanhees71
Welcome to PF!
No.
The first question is "what type of velocity do we measure?". Take a laser pointer, point at the moon and rotate it fast enough: the dot of the pointer can easily "move" from one side to the moon at a speed faster than the speed of light. That is not the speed of any real object, however, and it cannot be used to transmit information from one side of the moon to the other at this speed.

The true limit applies to signal speed: how fast can an event at place A influence an event at place B? None of the experiments discussed there found superluminal effects here.
Just to expand on what mfb said, the limit of the speed of light applies to particles and mechanical disturbances (there is actually really good information about this on the FAQs, I believe under relativity). The dot on the laser pointer he mentioned is not a particle or object because it is an effect of the photons constantly traveling from the pointer to the moon, and those photons are effected by the speed of light limit.

1oldman2 and mfb
DrStupid
The dot on the laser pointer he mentioned is not a particle or object [...]

That depends on the definition of "object".

That depends on the definition of "object".
Object meaning something made up of one or more particles, and we should not make this more complicated than it needs to be. I understand that it is not a perfect definition but it should do for this situation.

davenn and 1oldman2
DrStupid
Object meaning something made up of one or more particles

That would mean that a black hole is not an object because it is made up of space time only.
And it would mean that a dot on a crt-display is an object because it is made up of electrons and a fluorescent substance. And yes, I know that this also depends on the definition of "made up of".

and we should not make this more complicated than it needs to be.

Than we should avoid imprecise terms.

1oldman2
Object meaning something made up of one or more particles, and we should not make this more complicated than it needs to be. I understand that it is not a perfect definition but it should do for this situation.
Good show! If an explanation ain't broke making it more complicated won't fix it.

davenn
That would mean that a black hole is not an object because it is made up of space time only.
And it would mean that a dot on a crt-display is an object because it is made up of electrons and a fluorescent substance. And yes, I know that this also depends on the definition of "made up of".

Than we should avoid imprecise terms.
I'm sorry for my improper terminology, however I believe the OP gets what I mean. As I said, it is not a perfect definition, but it should do for this situation.

Staff Emeritus