Physics question

[jdoggg12]

If you had a light source traveling at the speed of light in 1 direction, would the light emitted from it, in the opposite direction, be moving at all or would it travel away from the point of origin at the speed of light?

I believe it would be standing still. Kinda like if you are in a car traveling 30mph in 1 direction and you throw a ball at 30mph in the opposite direction, it'll just fall to the ground relative to everyone else but the person in the car.

 

[silverpig]

Nope. It moves at the speed of light. If you were sitting on earth and saw a spaceship traveling in one direction at c, and it shot a mini-spaceship backwards at c, you'd see the ship move one way at c and the mini-ship the other way at c.

If you were on the first spaceship, you'd see the mini-ship traveling away from you at c. Basically, no matter how you look at it, light always travels at c (through a vacuum).

 

[So]

Wouldn't it be traveling at the speed of light in the other direction but redshifted?

 

[Praxis1452]

Light always moves at c in a vacuum relative to the frame of reference.

Just look up relativity.

 

[Foxery]

Baseballs aren't made out of light

Your spaceship's headlights will be heavily blueshifted, and your tail lights will be heavily red shifted. Both will travel at exactly c in their respective directions.

 

[IHateMyJob2004]

It amazes me how people don't understand the concept of the word relative in the "theory of relativity". And if you take that idea, and try to comprehend it it can make your brain flip out.

That is:
Item A going to the left at the speed of light relative to Item B that can be thought of as stationary. After A passes B, it emits light. What happens? What if there is an item C going to the left relative to B at hte speed of light. What does A peceive C to be going in terms of speed? It can not be 2X the speed of light can it?

Ow, my brain.

 

[miketheidiot]

why is the speed of light the speed of light?

why isn't the speed of light some other speed?

can the speed of light be derived from some constant? why is it the speed that it is?

 

[2Xtreme21]

Originally posted by: miketheidiot
why is the speed of light the speed of light?

why isn't the speed of light some other speed?

can the speed of light be derived from some constant? why is it the speed that it is?

Because it's how fast it goes?

 

[91TTZ]

Originally posted by: Foxery
Baseballs aren't made out of light

Your spaceship's headlights will be heavily blueshifted, and your tail lights will be heavily red shifted. Both will travel at exactly c in their respective directions.

That's why riced out Hondas always seem to have blue headlights... because they're so fast.

 

[miketheidiot]

Originally posted by: 2Xtreme21

Originally posted by: miketheidiot
why is the speed of light the speed of light?

why isn't the speed of light some other speed?

can the speed of light be derived from some constant? why is it the speed that it is?

Because it's how fast it goes?

but why that particular speed?

 

[2Xtreme21]

Originally posted by: miketheidiot

Originally posted by: 2Xtreme21

Originally posted by: miketheidiot
why is the speed of light the speed of light?

why isn't the speed of light some other speed?

can the speed of light be derived from some constant? why is it the speed that it is?

Because it's how fast it goes?

but why that particular speed?

Not to sound like a douche, but because it's how far it travels (3x10^8m) in a second.

 

[Gamingphreek]

Originally posted by: miketheidiot

Originally posted by: 2Xtreme21

Originally posted by: miketheidiot
why is the speed of light the speed of light?

why isn't the speed of light some other speed?

can the speed of light be derived from some constant? why is it the speed that it is?

Because it's how fast it goes?

but why that particular speed?

Because when we measured the time it took a beam of light to get from point A to point B it came out as a time. We took that time and and put under the distance between those points and it came out to be 3*(10^8) m/s.

If you are assuming this is in a vacuum light will always travel at C no matter what. I understand your question and logic would say that +3*(10^8) + -3*(10^8) would equal 0. Somehow it just doesn't.

-Kevin

 

[Born2bwire]

Originally posted by: miketheidiot
why is the speed of light the speed of light?

why isn't the speed of light some other speed?

can the speed of light be derived from some constant? why is it the speed that it is?

Speed of light is the constant. You don't derive it, you define it. Now, if you want some real fun, try deriving the fine structure constant from first principles.

 

[DrPizza]

Originally posted by: miketheidiot
why is the speed of light the speed of light?

why isn't the speed of light some other speed?

can the speed of light be derived from some constant? why is it the speed that it is?

The speed of light in a vacuum is the same value, regardless of what the observer or the observer's frame of reference is. And, it's that particular speed by definition. The speed of light is defined as 299,792,458 meters per second. What's a meter? It's how far light travels in a vacuum in 1/299,792,458th of a second. Technically, you no longer can measure the speed of light. Instead, you're seeing how accurate the meter stick you're using is.

 

[Vic]

Originally posted by: miketheidiot

Originally posted by: 2Xtreme21

Originally posted by: miketheidiot
why is the speed of light the speed of light?

why isn't the speed of light some other speed?

can the speed of light be derived from some constant? why is it the speed that it is?

Because it's how fast it goes?

but why that particular speed?

No one knows. Although there is some speculation that it hasn't always been the same.

My personal opinion is that its the speed of expanding space-time, but that still doesn't answer the question either.

 

[hypn0tik]

The speed of light is constant in any frame of reference is it not?

 

[OUCaptain]

The Theory of Relativity is pure evil. The more I understand it, the more it makes my brain hurt.

Same thing happens when I think about the size of the universe.

 

[Jeff7]

Originally posted by: miketheidiot

Originally posted by: 2Xtreme21

Originally posted by: miketheidiot
why is the speed of light the speed of light?

why isn't the speed of light some other speed?

can the speed of light be derived from some constant? why is it the speed that it is?

Because it's how fast it goes?

but why that particular speed?

Why not that particular speed? You could ask the same question if it went 300mph or 3 trillion miles per second.

It might be dependent on some property of spacetime that we can't yet measure directly. But then, you could just ask why that property of spacetime is the way it is.
It just IS that way, simple as that.


Concerning the OP: Normal laws of physics don't really apply once you get close to the speed of light. Fun stuff happens: Mass increases, and an object gets flatter in the direction of travel.

 

[CorCentral]

Originally posted by: IHateMyJob2004
It amazes me how people don't understand the concept of the word relative in the "theory of relativity". And if you take that idea, and try to comprehend it it can make your brain flip out.

That is:
Item A going to the left at the speed of light relative to Item B that can be thought of as stationary. After A passes B, it emits light. What happens? What if there is an item C going to the left relative to B at hte speed of light. What does A peceive C to be going in terms of speed? It can not be 2X the speed of light can it?

Ow, my brain.

The Plane/Treadmill deal is tough enough for some people in here to grasp!
Those that actually believe that a plane on a treadmill cannot take off?? Go to another forum already! :laugh:

 

[Evadman]

the plane takes off
you switch doors
1=.999~
If you are going 99% the speed of light, and shine a flashlight, the light will appear to move away from you at 300kmps. Relitive to you, it is moving at 300kmps. To a stationary opbserver, it is also moving at 300kmps. Does your head hurt? Good. Go read up on the double slit experiment to blow your head inside out.

 

[Random Variable]

Originally posted by: jdoggg12
If you had a light source traveling at the speed of light in 1 direction, would the light emitted from it, in the opposite direction, be moving at all or would it travel away from the point of origin at the speed of light?

I believe it would be standing still. Kinda like if you are in a car traveling 30mph in 1 direction and you throw a ball at 30mph in the opposite direction, it'll just fall to the ground relative to everyone else but the person in the car.

When you're dealing with speeds near or at the speed of light, the normal vector addition of velocities doesn't apply.

 

[Jeff7]

Originally posted by: Random Variable

Originally posted by: jdoggg12
If you had a light source traveling at the speed of light in 1 direction, would the light emitted from it, in the opposite direction, be moving at all or would it travel away from the point of origin at the speed of light?

I believe it would be standing still. Kinda like if you are in a car traveling 30mph in 1 direction and you throw a ball at 30mph in the opposite direction, it'll just fall to the ground relative to everyone else but the person in the car.

When you're dealing with speeds near or at the speed of light, the normal vector addition of velocities doesn't apply.

Sure it does. You just have another variable to account for - time.

 

[91TTZ]

Originally posted by: miketheidiot
why is the speed of light the speed of light?

why isn't the speed of light some other speed?

can the speed of light be derived from some constant? why is it the speed that it is?

why is an apple an apple?

why isn't an apple an orange?

can an apple be derived from some other fruit? why is it the fruit that it is?

 

[rivan]

Originally posted by: 91TTZ

Originally posted by: miketheidiot
why is the speed of light the speed of light?

why isn't the speed of light some other speed?

can the speed of light be derived from some constant? why is it the speed that it is?

why is an apple an apple?

why isn't an apple an orange?

can an apple be derived from some other fruit? why is it the fruit that it is?

An apple is an apple because the tree that makes it has the genetic instructions to make apples.

I think he's looking for reasons - physical constraints or whatever - that limit light to C.

 

[ZeroEffect]

The cosmologist Joao Magueijo theorizes that at the time of the big bang, light traveled faster
than it does now. Check out his show on the Science Channel. interesting stuff.