Thread: time

It is said one of the unique things about time is that it only goes one way - to the future. It is said as a an example that for instance you can never uncrack an egg.

First of all 'time' may or may not exist. Its something we make up to make things understandable (like the word 'gene') After all all observation is subjective.

So does not quantum physic suggest that the whole egg and the cracked egg both exist together, its only our observations that make it seem one follows the other.

Why?

Because we need to explain things so that we can understand them, regardless of the REALITY, its how are brains work. We need to put things into patterns

However thats us. That is not necessarily WHAT IS

Not only is all relative, but we can only see what we can see, and we can only understand what we can understand. And that is a limit. So therefore all scientific observation is limited to what we can understand, or the stories we make up, to understand

here is a basic question - why is there something rather than nothing?

how can we a part of the whole - explain the whole?

if logic is the pure answer then where is the logic in the following "everything I say is untrue"

How can we prove TIME exists? ( a clock? the words 'past' and 'future"? )

If we cannot answer basic questions, no wonder we create scapegoats like time and space to explain our stories

Time exists because, as far as I know, general relativity proved it to be an extra dimension added onto the 3 dimensions of space (x, y, z)- hence Space-time. The question I must ask the experts on here is: as time is a dimension, does it have an x (length) dimension like space? And, if so, as this spatial dimension can be altered- does this mean the 'length of time' can be altered too (i.e. Time travel)?

Originally Posted by x(x-y)

Time exists because, as far as I know, general relativity proved it to be an extra dimension added onto the 3 dimensions of space (x, y, z)- hence Space-time. The question I must ask the experts on here is: as time is a dimension, does it have an x (length) dimension like space? And, if so, as this spatial dimension can be altered- does this mean the 'length of time' can be altered too (i.e. Time travel)?

Time is not an "added dimension in general relatvity. The spacetime manifold of GR is a 4-dimensional Lorentzian manifold. Both "time" and "space" are local ideas. There is no global definition of either time or space. What clocks measure is "proper time", which is the length of the world line of the clock in terms of the metrc of spacetime. Proper time is associated with each world line, and is not a dimension per se.

Ah, ok. I see, thank you.

Nothing to do with the thread, or physics, but I was just reading a short article about the American writer, William Faulkner, who apparently said about time: "The past is never dead. It's not even past."

and your opinion about that ?

Originally Posted by x(x-y)

Time exists because, as far as I know, general relativity proved it to be an extra dimension added onto the 3 dimensions of space (x, y, z)- hence Space-time.

Note quite, it was Minkowski who introduced spacetime in 1908 in Raum und Zeit, which is considered to be a special relativity paper.

Originally Posted by x(x-y)

The question I must ask the experts on here is: as time is a dimension, does it have an x (length) dimension like space?

No. When calculating a spatial distance you use x y and z, but when calculating a spacetime interval you use x y z and -t. The minus sign means time is very different to space. It's a dimension of measure rather than a dimension that offers freedom of motion. In other words you can move through space but you can't move through time. Even if you take a fast round trip such that you suffer time dilation, we meet back up at the same time. You don't end up living in my past.

Originally Posted by x(x-y)

And, if so, as this spatial dimension can be altered- does this mean the 'length of time' can be altered too (i.e. Time travel)?

The "length" of elapsed time as measured by you can change, but it isn't time travel. Time travel is science fiction.

Thank you Farsight. However, how can you be so sure that time travel is just science fiction? That's hasn't been proven, has it?

Originally Posted by x(x-y)

Thank you Farsight. However, how can you be so sure that time travel is just science fiction? That's hasn't been proven, has it?

The equations of general relativity do not clearly prohibit closed timelike curves. In fact closed timelike curves are known to exist under exotic conditions.

However Stephen Hawking showed that if the weak energy condition is satisfied then closed timelike curves are prohibited. A more general conjecture of Hawking, the "chronology protection conjecture" states that time travel is impossible at the macroscopic scale in the real universe. It remains an unproved conjecture, but most physicists would be surprised if it were not true.

Originally Posted by Farsight

Originally Posted by x(x-y)

The question I must ask the experts on here is: as time is a dimension, does it have an x (length) dimension like space?

No. When calculating a spatial distance you use x y and z, but when calculating a spacetime interval you use x y z and -t. The minus sign means time is very different to space. It's a dimension of measure rather than a dimension that offers freedom of motion. In other words you can move through space but you can't move through time. Even if you take a fast round trip such that you suffer time dilation, we meet back up at the same time. You don't end up living in my past.

1. The spacetime interval in Minkowski space is the proper time of the straight line path connecting two points. A clock following that path would record that proper time.

2. Of course you can travel through time. I just traveled about 90 seconds while typing this. It appears to be impossible NOT to travel through time. Going backwards is a bit more problematic.

Originally Posted by ecom131

It is said one of the unique things about time is that it only goes one way - to the future. It is said as a an example that for instance you can never uncrack an egg.

First of all 'time' may or may not exist. Its something we make up to make things understandable (like the word 'gene') After all all observation is subjective.

So does not quantum physic suggest that the whole egg and the cracked egg both exist together, its only our observations that make it seem one follows the other.

Why?

Yeah. Our notion of time is tied very closely to our notion of entropy. At the highest level of entropy, like say a really hot gas or plasma, there would be no preferred direction for us to say time is flowing. Backwards and forwards are basically the same.

Originally Posted by kojax

... At the highest level of entropy, like say a really hot gas or plasma, there would be no preferred direction for us to say time is flowing. Backwards and forwards are basically the same.

As per your usual style, this assertion is baseless.

Did you really pass a physics course somewhere ?

At the extreme of entropy, determinism breaks down. It's an equivalent statement to say that time has no discernible arrow.

Did you really pass a mathematics/logic/reasoning course somewhere?

Originally Posted by kojax

At the extreme of entropy, determinism breaks down. It's an equivalent statement to say that time has no discernible arrow.

Rubish.

I defy byou to prove it.

Originally Posted by kojax

Did you really pass a mathematics/logic/reasoning course somewhere?

Several. You either did not or attended a most unusual school -- a school those wishing an education should avoid.

You have made many positive assertions that without any foundation. Rank unsupported speculation at best, often just plain wrong.

Originally Posted by DrRocket

Originally Posted by Farsight

Originally Posted by x(x-y)

The question I must ask the experts on here is: as time is a dimension, does it have an x (length) dimension like space?

No. When calculating a spatial distance you use x y and z, but when calculating a spacetime interval you use x y z and -t. The minus sign means time is very different to space. It's a dimension of measure rather than a dimension that offers freedom of motion. In other words you can move through space but you can't move through time. Even if you take a fast round trip such that you suffer time dilation, we meet back up at the same time. You don't end up living in my past.

1. The spacetime interval in Minkowski space is the proper time of the straight line path connecting two points. A clock following that path would record that proper time.

This is amusing.

How will you get a clock to travel a spacelike space-time interval?

Spacelike paths cannot be physically traveled (as they require moving faster than light).
http://en.wikipedia.org/wiki/Proper_time

Originally Posted by chinglu

Originally Posted by DrRocket

Originally Posted by Farsight

Originally Posted by x(x-y)

The question I must ask the experts on here is: as time is a dimension, does it have an x (length) dimension like space?

No. When calculating a spatial distance you use x y and z, but when calculating a spacetime interval you use x y z and -t. The minus sign means time is very different to space. It's a dimension of measure rather than a dimension that offers freedom of motion. In other words you can move through space but you can't move through time. Even if you take a fast round trip such that you suffer time dilation, we meet back up at the same time. You don't end up living in my past.

1. The spacetime interval in Minkowski space is the proper time of the straight line path connecting two points. A clock following that path would record that proper time.

This is amusing.

How will you get a clock to travel a spacelike space-time interval?

Spacelike paths cannot be physically traveled (as they require moving faster than light).
http://en.wikipedia.org/wiki/Proper_time

You are correct in that the statement applies only to timelike curves. But a worldline if an object is always a timelike curve. So your comment, though technically correct, is basically pointless.

So how does a supermassive black hole cause frame dragging and a relative backwards time travel?

Originally Posted by DrRocket

Originally Posted by chinglu

Originally Posted by DrRocket

Originally Posted by Farsight

Originally Posted by x(x-y)

The question I must ask the experts on here is: as time is a dimension, does it have an x (length) dimension like space?

No. When calculating a spatial distance you use x y and z, but when calculating a spacetime interval you use x y z and -t. The minus sign means time is very different to space. It's a dimension of measure rather than a dimension that offers freedom of motion. In other words you can move through space but you can't move through time. Even if you take a fast round trip such that you suffer time dilation, we meet back up at the same time. You don't end up living in my past.

1. The spacetime interval in Minkowski space is the proper time of the straight line path connecting two points. A clock following that path would record that proper time.

This is amusing.

How will you get a clock to travel a spacelike space-time interval?

Spacelike paths cannot be physically traveled (as they require moving faster than light).
http://en.wikipedia.org/wiki/Proper_time

You are correct in that the statement applies only to timelike curves. But a worldline if an object is always a timelike curve. So your comment, though technically correct, is basically pointless.

Very good, but you made a general comment about space-time and now you are correcting yourself to only include time-like curves.

You have proven yourself to be a good pupil, but you did not prove me wrong based on your statements.

You talked about general Minkowski spacetime with your example, and I corrected you because you were wrong. You included space-like intervals.

Having read DrRocket's comments, he made no mention of space-like curves, only spacetime (which is all of everything, includeing space-like, time-like and light-like curves).

Originally Posted by x(x-y)

Thank you Farsight. However, how can you be so sure that time travel is just science fiction?

I'm sure because I understand time. There's an interesting book called A World Without Time: the Forgotten Leagcy of Godel and Einstein that's fairly interesting. It's heavy going at times, but there's some good history in there. It describes how Godel and Einstein worked out what time was all about in 1949. The blurb says time does not exist, but actually it ought to be time isn't what people often say it is. It isn't something that flows, and it isn't something you can travel through. To understand this, think about a stasis box. That’s science fiction too, kind of like fighting fire with fire, but it's a good one. No motion occurs inside the box, so when I put you inside one, electromagnetic phenomena don’t propagate, nor do nerve impulses, nothing moves, nothing happens at all. So you can’t see, you can’t hear, your heart doesn't beat, and you can’t even think. Hence when I open the door 5 years later, to you it’s like I opened the door just as soon as I closed it. You “travelled” to the future by not moving at all. Instead everything else did.

If you don't like this stasis box just think in terms of a refrigerator. We can freeze human embryos now. A child is born maybe five years after it was conceived, but it didn't "travel through time".

Originally Posted by x(x-y)

That's hasn't been proven, has it?

No. Nor has the non-existence of fairies.

Originally Posted by MagiMaster

Having read DrRocket's comments, he made no mention of space-like curves, only spacetime (which is all of everything, includeing space-like, time-like and light-like curves).

Excellent.

Then he also said that a clock could follow such path.

To be scientific, you must include all information.

Are you scientific?
But, a clock cannot follow a space-like path.

Now do you understand?

Originally Posted by Farsight

I'm sure because I understand time. .

We have been through this before in some detail.

You don't understand time, general relativity or much else.

You have proved yourself to be a menace on the board and a well-recognized crank across many boards on the internet.

You are a positive danger to neophytes on the board who are trying to learn real science.

The notion that time halts in a "stasis chamber" is pure science fiction, which you present as real science. CRANK

Originally Posted by Farsight

If you don't like this stasis box just think in terms of a refrigerator. We can freeze human embryos now. A child is born maybe five years after it was conceived, but it didn't "travel through time".

Maybe that kind of time travel is the best we can hope for. If reverse time travel were possible, it probably would have to consist in a similar process, except instead of bringing all the chemical processes to a halt, it makes them work backwards. A time travel machine that just teleports you to the time you want to visit would be like trying to make that embryo pop out of existence and suddenly reappear 5 years later instead of being present in a frozen form for all that time.

Of course that's a really big "if", but such is the nature of the topic.

It's all about causality. If you can create a situation where the last event (from our perspective) triggers the first event (from our perspective), then you've defined an object that travels backward through time (from our perspective). Naturally that object would perceive us to be the ones going backward in time, not itself. I don't have any good ideas about how to do that. I'm just saying that is the definition of backwards time travel.

Originally Posted by x(x-y)

That's hasn't been proven, has it?

No. Nor has the non-existence of fairies.

This experiment at least appears to have sent information back in time.

http://en.wikipedia.org/wiki/Delayed...quantum_eraser