Science junkies .. I need help with this one.

[Jeremy]

In regards to the "speed" in which an object travels through space.

On earth we determine speed by how fast an object is moving in relation to the ground.
The speed of the earth is determined by it's relation to the sun.
The speed of the sun is determined by it's relation to the center of the galaxy. etc. etc.

How is the speed of an object determined in the vacuum of outerspace?
Light obviously travels at a constant speed in relation to it's source, but all light sources in the universe are themselves "moving".
How do we know what "stationary" is in outerspace to identify the true "speed" of an object? And how does this factor into setting limitations on how 'fast' matter can "travel'.

I guess what I'm trying to figure out is whether or not "the speed of light" is actually a barrier when it comes to how "fast" matter can travel.

Any thoughts?

 

[CrusaderFrank]

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"

 

[Jeremy]

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.

 

[ABikerSailor]

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.

 

[Jeremy]

I guess I just don't buy into the theory that the speed of matter is limited in relation to "the speed of light" and that matter would turn into energy once it breaks that threshold.

 

[CrusaderFrank]

I guess I just don't buy into the theory that the speed of matter is limited in relation to "the speed of light" and that matter would turn into energy once it breaks that threshold.

I highly recommend the book "Hyperspace" by Michio Kaku

 

[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?

 

[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.

 

[Dr.Traveler]

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?

You can't. Part of relativity is the fact there's no unique frame of reference. That's why the fact that light moves at the same speed regardless of frame of reference is so baffling the first time you see it.

Take this as an example:

You're standing stationary. A train whizzes by at 50 mph and a person on the train throws a ball at 80 mph (in his reference frame) from the train, to you the observer it is travelling at 130 mph (80+50).

However, if the person on the train turns on a flashlight, in his reference frame it is traveling at c. Strangely enough in your reference frame it is also traveling at c.

That's the issue. Experiment after experiment has proven light always moves c through a vacuum in any frame of reference. The idea that c is the universal speed limit comes from that.

 

[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.

 

[Jeremy]

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?

 

[Baruch Menachem]

What you are thinking of is not speed, but vector. I think Frank gave the best answer, speed is where an observer views something moving from point to point in his reference. So someone standing on venus watching a beam of light will see it as taking an hour and 23 minutes to get here.

A vector is the speed of something in relation to something to which it is attached. As a person sitting on earth, I am moving at thousands of miles per hour in relation to my position vis a vis the sun, but my speed here is zero, as my chair is not moving.

This explains your question

[ame="http://www.youtube.com/watch?v=dYlstdCWzCY"]Jaimie goes boom[/ame]

 

[Baruch Menachem]

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?

yes

 

[Bill Angel]

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?

Well..not really.
Here is a slightly different thought experiment.
Physicists use particle accelerators to propel subatomic particles to speeds very close to the speed of light. So lets say an electron is accelerated to .999 of the speed of light.
Now the electron emits a photon. In the frame of reference of the electron (which is also moving at .999 of the speed of light) the photon has a velocity of the speed of light.
In the frame of reference of the observer (who is stationary along with the particle accelerator) the photon also has a speed of 1.0 of the speed of light. But what is NOT the same in the two frames of reference is the WAVELENGTH of the photon that was emitted. If the photon had a wavelength of red light in the electron's frame of reference, it would have a wavelength of violet in the stationary observer's frame of reference.

 

[Jeremy]

 

[ABikerSailor]

Interestingly enough, photons can only move at 186,000 miles/sec. If you go past that speed, then there is a thing called a tachyon, which their speed is unlimited (kinda).

They can go no SLOWER than 186,001 miles per sec.

 

[Si modo]

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

 

[Jeremy]

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.

 

[ABikerSailor]

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).

 

[JBeukema]

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.