What is the frame of reference?

[midgetwars]

Also what is the twin paradox?

[swansont]

http://en.wikipedia.org/wiki/Twin_paradox

 

An inertial frame of reference is any coordinate system that is not accelerating. Usually you choose it to be co-moving (and the origin co-located) with one of the observers in the problem.

[midgetwars]

still makes no sense

[toastywombel]

This is the definition of frame of reference:

 

"A frame of reference in physics, may refer to a coordinate system or set of axes within which to measure the position, orientation, and other properties of objects in it, or it may refer to an observational reference frame tied to the state of motion of an observer."

 

Essentially a frame of reference is a coordinate system based on the position of the observer. Like if you created a frame of reference around yourself, you could imagine a coordinate system emanating from you. With your position being 0,0,0 (at the origin). Refer to the following image:

 

 

As for the twin paradox this is from wikipedia as here, I also believe it was linked by swansont.

 

"In physics, the twin paradox is a thought experiment in special relativity, in which a twin makes a journey into space in a high-speed rocket and returns home to find he has aged less than his identical twin who stayed on Earth. This result appears puzzling because each twin sees the other twin as traveling, and so, according to the theory of special relativity, paradoxically each should find the other to have aged more slowly. How the seeming contradiction is resolved, and how the absolute effect (one twin really aging less) can result from a relative motion, can be explained within the standard framework of special relativity. The effect has been verified experimentally using precise measurements of clocks flown in airplanes.[1][2]"

 

Only one twin ages though, this is because only one of the twins actually changed their frame of reference. The twin who took the journey would age more because he underwent the acceleration, as opposed to the other twin who stayed on Earth.

 

Because light is a constant to all observers that means time cannot always be agreed between two observers, especially if they are travelling away from each other near the speed of light. This is called time dilation. I suggest you watch the set of videos here, they offer a good explanation of how time works per say.

[Bob_for_short]

A frame of reference is an observatory. It is furnished with means to measure everything in question.

[swansont]

still makes no sense

 

Can you be more specific?

[StringJunky]

Frame of Reference could be thought of as: that point in space (which may be moving) from which some external moving object is measured against.

 

The need for this term is because there is no such thing as absolute zero velocity...there isn't a universally applicable yardstick where we can say 'this or that object is moving at absolute zero velocity' relative to ALL the background....every external velocity measured is always relative to the motion of the observer or observation point.

 

You physics guys correct me on this but that's how I understand it at the moment.

Edited February 13, 2010 by StringJunky

[npts2020]

From my frame of reference it has generally meant;

Observer/Narrator Point of View=Frame of Reference

[midgetwars]

oh ok.......

[mooeypoo]

The need for a frame of reference starts because time and movement are relative.

 

Think of it this way: You are sitting on a chair (presumably) reading this post in front of your computer. You're not moving. A car outside your window is moving relative to you. That is, the car is moving relative to your frame of reference.

 

If I am inside the car, I am sitting down strapped to the seat. While I logically know that I am moving, I could also look at things from *my* frame of reference and declare myself as stationary and the road, streets, buildings and you in your chair to be moving relative to me. That would be perfectly true, and in fact when we calculate relative speeds we do that.

 

Now look at some spaceship outside our galaxy, say. The person inside that spaceship looks at the Earth, and for him, the Earth is moving - around the sun, around itself, and along with the sun around the center of our galaxy. For the observer outside the galaxy, the Earth -- which we defined as 'stationary' before when we looked at ourselves in front of the computer -- is no longer stationary, it's moving.

 

You are stationary in your own frame of reference, but you are moving relative to other frames of reference. When you go into relativity, those definitions get an even bigger meaning because we can calculate relative time dilation and length contraction based on the difference in reference frames. Also, in relativity, you *must* pick a frame of reference to discuss otherwise you are making no sense, because there's no such thing as "absolute" frame. That is, while you are stationary in your seat, there will always be infinite number of reference frames that will see you moving. We won't be able to speak of your state (moving or stationary, and at what speed) if we don't decide, first, that we are talking about the same frame of reference.

 

Last example: If I am on a moving train, and I throw a ball accross the cart, I see myself as stationary, and can calculate the speed of the ball *relative to me*. However an observer on the ground, outside the train, will calculate a different speed for the ball, relative to him, which would also include the speed of the moving train.

 

That is what we mean by "Frame of Reference".

 

~moo

[ponderer]

The need for a frame of reference starts because time and movement are relative.

 

Think of it this way: You are sitting on a chair (presumably) reading this post in front of your computer. You're not moving. A car outside your window is moving relative to you. That is, the car is moving relative to your frame of reference.

 

If I am inside the car, I am sitting down strapped to the seat. While I logically know that I am moving, I could also look at things from *my* frame of reference and declare myself as stationary and the road, streets, buildings and you in your chair to be moving relative to me. That would be perfectly true, and in fact when we calculate relative speeds we do that.

 

Now look at some spaceship outside our galaxy, say. The person inside that spaceship looks at the Earth, and for him, the Earth is moving - around the sun, around itself, and along with the sun around the center of our galaxy. For the observer outside the galaxy, the Earth -- which we defined as 'stationary' before when we looked at ourselves in front of the computer -- is no longer stationary, it's moving.

 

You are stationary in your own frame of reference, but you are moving relative to other frames of reference. When you go into relativity, those definitions get an even bigger meaning because we can calculate relative time dilation and length contraction based on the difference in reference frames. Also, in relativity, you *must* pick a frame of reference to discuss otherwise you are making no sense, because there's no such thing as "absolute" frame. That is, while you are stationary in your seat, there will always be infinite number of reference frames that will see you moving. We won't be able to speak of your state (moving or stationary, and at what speed) if we don't decide, first, that we are talking about the same frame of reference.

 

Last example: If I am on a moving train, and I throw a ball accross the cart, I see myself as stationary, and can calculate the speed of the ball *relative to me*. However an observer on the ground, outside the train, will calculate a different speed for the ball, relative to him, which would also include the speed of the moving train.

 

That is what we mean by "Frame of Reference".

 

~moo

 

A buddy and I were driving in Quebec. I was doing the speed limit, but the topic of the Surete du Quebec came up - it think we saw a fuzzmobile going the other way - and of course speeding.

 

I commented to him that we were actually moving backwards at very high velocy, because we were going against the spin of the earth, which moves much faster than the car.

 

I pondered if we could actually go much faster and then argue in court that we were actually travelling backwards, and so beat the speeding ticket.

 

But then they might give me a bigger ticket for going the wrong way on a highway, and doing a couple thousand miles an hour over the speed limit, in reverse. That's dangerous driving.

 

I figured it was best to agree to the road being the stationary frame of reference and not use the sun. I stuck to the speed limit.

Edited April 15, 2010 by ponderer