Relativity - Oh dear, here we go again!

[RecoveringYuppy]

Don’t see how you can be both “in a frame” and “moving in respect to it”. Surely to be “in a frame” you have to be “moving with it”.

When you get up and walk around in a room do you suddenly forget you're in the room?

Reference frames are arbitrarily chosen points of comparison. You chose one for your convencience depending on what you are trying to figure out.

Whatever baggage or complications you've attached to the phrase simply need to be forgotten.

 

[ynot]

When you get up and walk around in a room do you suddenly forget you're in the room?

Reference frames are arbitrarily chosen points of comparison. You chose one for your convencience depending on what you are trying to figure out.

Whatever baggage or complications you've attached to the phrase simply need to be forgotten.

Not sure what you’re saying here. When you’re walking around a room you’re still able to observe it as one frame can be observed from another. But this doesn’t mean that you’re in the same frame as the room. When you’re walking around the room you’re in the frame that you’re walking at, which is different to the frame of the room. If you’re changing your speed and direction, you’re changing your frame. I don’t see how observing one frame from another actually puts you in the other frame.

 

[RecoveringYuppy]

Simply forget what you just said and memorize the correct definition.

 

[ynot]

Simply forget what you just said and memorize the correct definition.

Simply read the bible and have faith?

 

[Fredrik]

But this doesn’t mean that you’re in the same frame as the room. When you’re walking around the room you’re in the frame that you’re walking at, which is different to the frame of the room. If you’re changing your speed and direction, you’re changing your frame. I don’t see how observing one frame from another actually puts you in the other frame.

You seem a little obsessed with the idea of being in a certain frame. As I said, a frame is just a function that assigns numbers to events. It's a mathematical abstraction, not something physical. When we say e.g. "the length of the space ship in Earth's frame is L", it only means that when we use the coordinate system that's associated in a natural way with Earth's path through space-time, the difference between the x coordinate at the front of the ship and the back of the ship is L. It has nothing to do with being in that frame, whatever that would mean.

Simply read the bible and have faith?

You don't need faith to learn how something is defined.

 

[69dodge]

Not sure what you’re saying here. When you’re walking around a room you’re still able to observe it as one frame can be observed from another. But this doesn’t mean that you’re in the same frame as the room. When you’re walking around the room you’re in the frame that you’re walking at, which is different to the frame of the room. If you’re changing your speed and direction, you’re changing your frame. I don’t see how observing one frame from another actually puts you in the other frame.

You don't observe a frame. You observe events. Events can be referred to any frame, and belong to none.

 

[69dodge]

How can you say “The clock is running slower in the other frame” when the clock is never actually in the other frame? It’s only perceived to be running slower when observed from the other frame. How does an anomaly of perception change the actual reality of the clock as it is, where it is?

Suppose we're standing in a field with some animals. To your right is a sheep, to your left a goat. I'm facing you, so the sheep is to my left, and the goat to my right. How can this be? What is the reality? Which animal is really to the right of the other?

Of course, the answer is that "right" and "left" aren't part of reality; they acquire meaning only when reality is observed from a particular viewpoint.

The distance between events, as well as the elapsed time between them, are, likewise, concepts that are not part of reality but rather acquire meaning only when the events are referred to a particular frame of reference.

 

[ynot]

You seem a little obsessed with the idea of being in a certain frame. As I said, a frame is just a function that assigns numbers to events. It's a mathematical abstraction, not something physical. When we say e.g. "the length of the space ship in Earth's frame is L", it only means that when we use the coordinate system that's associated in a natural way with Earth's path through space-time, the difference between the x coordinate at the front of the ship and the back of the ship is L. It has nothing to do with being in that frame, whatever that would mean.


You don't need faith to learn how something is defined.

Haven’t got time to give much time to an answer at present, but as a quick response - If a thing is a reality I tend to think it should be able to be explained and understood using real means. I guess I don’t think reverse engineering reality from math or impossible theoretical analogies are real means.

 

[ynot]

You don't observe a frame. You observe events. Events can be referred to any frame, and belong to none.

But events occur within a frame. And only one frame.

ETA - Events can move from one frame to another, but they are only in one frame at a given point in time.

 

[Fredrik]

Haven’t got time to give much time to an answer at present, but as a quick response - If a thing is a reality I tend to think it should be able to be explained and understood using real means. I guess I don’t think reverse engineering reality from math or impossible theoretical analogies are real means.

My quick response is that you seem to have misunderstood how physics gives us a better understanding of how the world works.

If you want to understand a real phenomenon, you have to understand the theory that describes it. There's no other way.

 

[69dodge]

But events occur within a frame. And only one frame.

ETA - Events can move from one frame to another, but they are only in one frame at a given point in time.

No.

I don't know what sort of definition you have in mind for the word "event", but whatever it is, it isn't the same as what the word means in relativity.

An event is an instantaneous occurrence of infinitesimal size. It can't move---moving takes time. Anything that happens later is a different event.

It does not occur "within a frame". It just occurs. A frame is a way of describing events that occur, by assigning to each of them a position and a time of occurence. Different frames can assign different positions and times to the same event.

 

[robinson]

If you want to understand a real phenomenon, you have to understand the theory that describes it. There's no other way.

So true. Until Kepler, Newton and Einstein, nobody understood gravity. Things fell, but nobody understood why.

 

[69dodge]

So true. Until Kepler, Newton and Einstein, nobody understood gravity. Things fell, but nobody understood why.

I'm not sure whether you're being sarcastic. I suspect you are. But I don't understand your point. Can you elaborate?

 

[RecoveringYuppy]

Simply read the bible and have faith?

Or continue to be stupid if you like.

 

[sol invictus]

But events occur within a frame. And only one frame.

ETA - Events can move from one frame to another, but they are only in one frame at a given point in time.

That doesn't make any sense, so either

a) you're using the words "event" and "frame" in some non-standard way, or

b) you're just confused.

An event is a point in spacetime; it cannot move any more than a point in space can have a length. A frame is simply a coordinate system, all events occur in all frames.

 

[ynot]

No.

I don't know what sort of definition you have in mind for the word "event", but whatever it is, it isn't the same as what the word means in relativity.

An event is an instantaneous occurrence of infinitesimal size. It can't move---moving takes time. Anything that happens later is a different event.

It does not occur "within a frame". It just occurs. A frame is a way of describing events that occur, by assigning to each of them a position and a time of occurence. Different frames can assign different positions and times to the same event.

Perhaps that’s because you said “events” not “event” - “You don't observe a frame. You observe events. Events can be referred to any frame, and belong to none.”

I can accept the concept of an event as a theoretical “snapshot” of existence, but I’m not sure that it can ever have actual existence. Regardless of how infinitesimal an event is time wise, it can’t ever be zero. It must account for at least some time otherwise the next event couldn’t occur. No time = no change = no next event. If time stops to create an event, how does it get started again? If an event can’t exist then a universal frame can’t exist either.

Regardless of whether an event can exist or not, I don’t see how it can ever be observed. How is it possible to observe something that only exists for an infinitesimal period of time? Observation is more to do with memory and anticipation of a contiguous series of past and future events.

As I see it, reality is represented by events (not an event). Different events create different frames and there is never an actual reality where existence shares the same frame. Time would stop if it did.

 

[ynot]

That doesn't make any sense, so either

a) you're using the words "event" and "frame" in some non-standard way, or

b) you're just confused.

An event is a point in spacetime; it cannot move any more than a point in space can have a length. A frame is simply a coordinate system, all events occur in all frames.

I choose a). Although b) could also apply.

 

[robinson]

I'm not sure whether you're being sarcastic. I suspect you are. But I don't understand your point. Can you elaborate?

Well, first you have to understand this statement.

If you want to understand a real phenomenon, you have to understand the theory that describes it. There's no other way.

See? In order for you to understand something, you have to understand the theory that describes it. Since there is no other way to understand, people couldn't possibly have understood gravity until a theory was created, and understanding the theory is the only way to understand gravity.

An event is an instantaneous occurrence of infinitesimal size. It can't move---moving takes time. Anything that happens later is a different event.

Do you have a reference for who defined "event" like that? I would love to read the paper. And know what genius defined event that way. It would help us all out. Thanks.

 

[ynot]

See? In order for you to understand something, you have to understand the theory that describes it. Since there is no other way to understand, people couldn't possibly have understood gravity until a theory was created, and understanding the theory is the only way to understand gravity.

Makes one wonder how any understanding was possible before there was theorists. Perhaps it was understanding by way of theists.

 

[69dodge]

See? In order for you to understand something, you have to understand the theory that describes it. Since there is no other way to understand, people couldn't possibly have understood gravity until a theory was created, and understanding the theory is the only way to understand gravity.

Yes. And? Am I supposed to disagree? In your opinion, people before Newton understood gravity as well as we do today?

Do you have a reference for who defined "event" like that? I would love to read the paper. And know what genius defined event that way. It would help us all out. Thanks.

The usage is quite standard. Einstein, for example, wrote: "... the world of physical phenomena ... is composed of individual events, each of which is described by four numbers, namely, three space co-ordinates x, y, z and a time co-ordinate, the time-value t."