Science junkies .. I need help with this one.

[JBeukema]

BTW, I should add that c is a local speed limit. It is possible globally to exceed c with respect to a very distant observer and his frame of reference.

?

Clarify. No matter your frame of reference, light never appears to travel @ >c

 

[JBeukema]

It's determined according to the point of view of the observer.

So depending on who is counting and where they are and what their frame of reference is, Earth has several speeds all of which are "Correct"

What Frank said is correct. I'd just add that it's been scientifically proven that the speed of light is constant in all frames of reference. That's why its the universal speed limit. Even light itself can't be accelerated faster than c.

I see. So if a flashlight is moving at c minus 1 mph, and you turned the flashlight on, the light illuminating from the flashlight would, in theory, only be traveling a 1mph. Do I have that correct?

Nope. You'd see it leave you @ c. If you're moving towards me, I'd see you coming @ (c-1) and the light would travel towards me at c.

Now you see where the relativity of time comes into play...

 

[Jeremy]

The speed limit for the universe is 186,000 miles/sec, or the speed of light.

Watch The Universe sometime, they explain it very well there.

I love that show and watch it all the time. But what is still unanswered, in my opinion, is what that speed is in relation to. How do they determine a 'stationary' point in the universe to base that measurement on?

They themselves are the stationary object.

ALL MOTION IS IN RELATION TO SOMETHING
Just take the old example of a pitcher on a flatbed truck throwing a ball to someone while someone in a car and someone on the ground watch.

And noone said the speed of light was limited. What Einstein actually deduced was that time is relative. 'Speed', by its very definition as change in position over a set period of time- well, you should be able to get it from here.

Also, who said matter would turn to energy @ c? What happens is that as you near c, you approach infinite mass- making further acceleration ever more difficult and eventually requiring infinite energy to accelerate since your mass is infinite.

Obviously, infinite energy doesn't exist, making it impossible for anything with mass to travel at c. Thus we only observe massless particles (eg: photons) traveling at (or anywhere near) c in any given frame of reference.

Thanks ... *cough* ... eer pass it on.

 

[Jeremy]

All I got to say is Gene Roddenberry had his shit together.

 

[THE LIGHT]

Irrespective of one's reference, the speed of light is constant and the limit.

That makes me wonder if anyone has calculated the speed at which the Earth is actually moving through the universe in relation to the speed of light. ...Not the speed in relation to the sun, but the Earth's "true" speed in relation to c.

Actually, the Mayans did with the long count calendar.

That's why the world is predicted to "end" on December 21st, 2012 at 11:00 am (probably either Eastern or Central Standard time, based on their location).

At least according to Hollywood.

 

[Quantum Windbag]

It's determined according to the point of view of the observer.

So depending on who is counting and where they are and what their frame of reference is, Earth has several speeds all of which are "Correct"

So by your definition there is no "true" speed. Thus no physical limitation to how fast matter can travel through a "vacuum". -at least that is what I am starting to believe myself.

The speed of light in a vacuum is is constant relative to the observer. If you are traveling at .5c relative to me, and send a radio signal my way, it will leave your position at 1c, and approach me at 1c. The way this works is that time actually slows down as you go faster, so light always travels at the same speed, which is dependent on time.

 

[Quantum Windbag]

The speed limit for the universe is 186,000 miles/sec, or the speed of light.

Watch The Universe sometime, they explain it very well there.

I love that show and watch it all the time. But what is still unanswered, in my opinion, is what that speed is in relation to. How do they determine a 'stationary' point in the universe to base that measurement on?

Astronomers generally take the center of the Milky Way and arbitrarily treat it as a fixed point. This is not accurate, obviously, but it is convenient, and it works.

 

[Quantum Windbag]

BTW, I should add that c is a local speed limit. It is possible globally to exceed c with respect to a very distant observer and his frame of reference.

?

Clarify. No matter your frame of reference, light never appears to travel @ >c

That is not what he said.

A rotating pulsar sends out a stream of energy that sweeps across the entire universe. An observer on that pulsar would see that stream sweeping across a distant gas cloud at a speed that appears to exceed that of light, even though the individual elecectrons making up that stream are limited to the speed of light.

 

[Jeremy]

This is quite possibly the most illuminating thread on USMB.

 

[Dr.Traveler]

BTW, I should add that c is a local speed limit. It is possible globally to exceed c with respect to a very distant observer and his frame of reference.

?

Clarify. No matter your frame of reference, light never appears to travel @ >c

That is not what he said.

A rotating pulsar sends out a stream of energy that sweeps across the entire universe. An observer on that pulsar would see that stream sweeping across a distant gas cloud at a speed that appears to exceed that of light, even though the individual elecectrons making up that stream are limited to the speed of light.

Yeah, this is it.

The first time I ran into the thought experiment of the Spotlight shining on the moon it blew my mind. Nothing in the model is breaking c, but to an outside observer it sure looks like the light is illuminating the surface of the moon at a superluminal speed.

Theoretically you can cover distance at greater than c using an Alcubierre drive or using a traversable wormhole, however, both objects are entirely theoretical and again, you don't actually break c locally.

 

[Dr.Traveler]

It's determined according to the point of view of the observer.

So depending on who is counting and where they are and what their frame of reference is, Earth has several speeds all of which are "Correct"

What Frank said is correct. I'd just add that it's been scientifically proven that the speed of light is constant in all frames of reference. That's why its the universal speed limit. Even light itself can't be accelerated faster than c.

I see. So if a flashlight is moving at c minus 1 mph, and you turned the flashlight on, the light illuminating from the flashlight would, in theory, only be traveling a 1mph. Do I have that correct?

Not really. The light is still moving at c.

Its crazy, but at relativistic speeds it turns out additivity of speeds breaks down. For example, if you're going at .98 c and you fire off a photon at .99 c, the photon's speed won't be additive. Instead you'll get something like .998 c (I don't have time to do the exact calculation now).

That's also kinda crazy. At low speeds, things add up nicely. At high speeds, they don't. Its another consequence of e=mc^2.

 

[zzzz]

Speed is a distance over time and although our scientific theories state that the speed of light cannot be exceeded our theories are not the final laws of nature. We are still seeking them. Just like light bends due to gravity can it be slowed down too.

So speed is just the distance that an object is travels over a set amount of time. There needs to be no observer or relation to anything else. Velocity is another subject that is realtive.

 

[Bill Angel]

BTW, I should add that c is a local speed limit. It is possible globally to exceed c with respect to a very distant observer and his frame of reference.

?

Clarify. No matter your frame of reference, light never appears to travel @ >c

That is not what he said.

A rotating pulsar sends out a stream of energy that sweeps across the entire universe. An observer on that pulsar would see that stream sweeping across a distant gas cloud at a speed that appears to exceed that of light, even though the individual elecectrons making up that stream are limited to the speed of light.

More precisely, INFORMATION cannot be propagated faster than the speed of light.

"If a laser is swept across a distant object, the spot of light can easily be made to move at a speed greater than c.Similarly, a shadow projected onto a distant object can be made to move faster than c. In neither case does any information travel faster than light."
See Faster-than-light - Wikipedia, the free encyclopedia

 

[Missourian]

BTW, I should add that c is a local speed limit. It is possible globally to exceed c with respect to a very distant observer and his frame of reference.

?

Clarify. No matter your frame of reference, light never appears to travel @ >c

You know, I always believed that the speed of light was the speed limit of the universe, but I read this article and now I'm not so sure.

I understand that the constant of light pertains to a vacuum, but 300 times the speed of light?

I tried to understand the principles involved, but it is beyond my level of comprehension.

Here is the article:

Scientists have seen a pulse of light emerge from a cloud of gas before it even entered.


This astonishing and baffling observation was made by researchers from the NEC Research Institute in Princeton, US.


They conducted an experiment that involved lasers, a chamber containing cold caesium atoms and a super-fast stopwatch.


The end result was a beam of light that moved at 300 times the theoretical limit for the speed of light.

BBC News | SCI/TECH | Beam smashes light barrier




​

 

[xotoxi]

All of you are wrong.

Nothing is moving...all movement is a figment of your imagination.

 

[Jeremy]

All of you are wrong.

Nothing is moving...all movement is a figment of your imagination.

 

[ABikerSailor]

That makes me wonder if anyone has calculated the speed at which the Earth is actually moving through the universe in relation to the speed of light. ...Not the speed in relation to the sun, but the Earth's "true" speed in relation to c.

Actually, the Mayans did with the long count calendar.

That's why the world is predicted to "end" on December 21st, 2012 at 11:00 am (probably either Eastern or Central Standard time, based on their location).

At least according to Hollywood.

Actually, no. It's according to what archaeologists and others who have studied the Mayan culture and artifacts have come up with.

Interestingly enough, did you know that the Mayans calculated the rotation of the Earth around the Sun to within 8/10ths of a SECOND of what scientists and astronomers say it is with all our super fantastic technology?

Might wanna do some research into the subject, the Blight.

 

[JBeukema]

More precisely, INFORMATION cannot be propagated faster than the speed of light.

I was under the impression that quantum entanglement threw a giant monkey wrench into that one?

 

[JBeukema]

BTW, I should add that c is a local speed limit. It is possible globally to exceed c with respect to a very distant observer and his frame of reference.

?

Clarify. No matter your frame of reference, light never appears to travel @ >c

You know, I always believed that the speed of light was the speed limit of the universe, but I read this article and now I'm not so sure.

I understand that the constant of light pertains to a vacuum, but 300 times the speed of light?

I tried to understand the principles involved, but it is beyond my level of comprehension.

Here is the article:

Scientists have seen a pulse of light emerge from a cloud of gas before it even entered.


This astonishing and baffling observation was made by researchers from the NEC Research Institute in Princeton, US.


They conducted an experiment that involved lasers, a chamber containing cold caesium atoms and a super-fast stopwatch.


The end result was a beam of light that moved at 300 times the theoretical limit for the speed of light.

BBC News | SCI/TECH | Beam smashes light barrier




​

i don't quite understand...

 

[dilloduck]

Actually, the Mayans did with the long count calendar.

That's why the world is predicted to "end" on December 21st, 2012 at 11:00 am (probably either Eastern or Central Standard time, based on their location).

At least according to Hollywood.

Actually, no. It's according to what archaeologists and others who have studied the Mayan culture and artifacts have come up with.

Interestingly enough, did you know that the Mayans calculated the rotation of the Earth around the Sun to within 8/10ths of a SECOND of what scientists and astronomers say it is with all our super fantastic technology?

Might wanna do some research into the subject, the Blight.

and archeologists and others who have studied the Mayans are above reproach ?
Even Einstein was proven wrong about somethings. Lets not be too quick to take a scientist's word as the gospel truth lest we sound like a religious fundementalist.