Should we think of time as the 4th dimension?

I don’t think of time as a dimension. I don’t it it helpful to do so.

I have some trouble with that metaphor too. We know that any dimension cannot be mapped in the other dimensions. The x axis look like a point in the y and so on.
So can we consider other properties like dimensions: Temperature (from hot to cold), or Noise level. or Radiation levels. Are these dimensions, too? None “map” into the others.

In any context in which time appears as the axis of a graph, it’s serving as a dimension.

This topic goes back at least to the time of H.G. Wells’ The Time Machine and Flatland by Edwin Abbott—both from the late 1800s.

A good physical metaphor is to think of 4-dimensional space-time as something through which we are traveling at the speed of light. When you sit in a chair, you are ‘speeding through time’ at the speed of light. As you move faster through space, it’s like rotating out of the time dimension into the space dimensions, so your speed through time slows down as your speed through space increases.

It’s just another way to try to visualize what the equations of the Lorentz transformation describe in mathematical detail. As a metaphor the mathematics speaks for itself ! The hard part is visualization. I don’t believe any human (including Einstein) could literally visualize four spatial dimensions.

The tricky part of relativity is that distances in space-time are calculated as the square root of (x^2 + y^2 + z^2 – t^2) . That final minus sign makes it complicated.

Stephen Hawking just posited that time travel is possible but without accelerating through space at a faster pace up to the speed of light…time travel would seem impossible. I would further argue that since we are not constantly bothered by people from the future, that is proof positive that at some point in the future some cataclysmic event obliterates the human race halting any development of time travel.

Time travel is possible, but only back in time.. We do it every time we look at the stars.

@gasman Interesting way of visualizing it. Thanks. But the light-speed chair analogy falls apart when I try to reverse directions, not speeding it up but slowing it down from a standstill. I am still left with something that, while theoretically interesting, does not behave at all like the 3 physical dimensions.

@Cruiser Why couldn’t the lack of visitors from some future where time travel is possible equally be evidence that the causal ordering postulate (COP) functions like a universal traffic cop, preventing travel fast enough to move through time?

If you allow time travel, then it should be possible for a mad scientist to invent a time machine and use it to travel back in time and murder himself before he invents the machine he used to commit the suicide. Generally, when a scientific postulate leads to obvious paradoxes, the postulate is what’s wrong, not the paradox it produces.

@ChazMaz Great point. It is certainly possible to “look” back in time. In fact, that is the only way we can see the distant portions of our Universe today.

@ETpro You got the wrong guy to further debate the nuts and bolts of this. But Stephen did also think traveling back in time was impossible due to some fundamental rule…
whatever that was supposed to mean?

Moving backwards is impossible, Hawking says, because it “violates a fundamental rule that cause comes before effect.”

If moving backwards through time was possible, a person could shoot their former selves.

“I believe things cannot make themselves impossible,” Hawking said.

If you want to think of it in basic geometry, and ignore relativity, think of it this way.

A point divides a line into two parts
A line divides a plane into two parts
A plane divides a space into two parts
A space divides a time into two parts (past and future).

So yes, it’s useful to think of time as the 4th dimension.

“If moving backwards through time was possible, a person could shoot their former selves.”
Problem with that theory is since you do exist then you did not. Even if you try.

@ETpro Yes, the Lorentz transformation—which successfully describes how the world works—treats time in a fundamentally different way from the 3 space dimensions, which only deepens the mystery of what time is.

Travel to the future is simple in the sense of the twin paradox, whereby a traveler returning from a near-speed-light trip has aged much more slowly than folks at home, where many generations may have elapsed since his departure.

While violation of causality (not to mentions the second law of thermodynamics) would seem to prohibit backward travel in time, some physicists think it’s still possible. There’s an in-between hypothesis that you can travel back in time—but no further than the invention of the time machine!

The problem, I believe, is one of presentation of data. We see the three dimensions as space in the real world. We use three axes on a two dimensional plane in order to try to display information about three dimensional models. If we are to extrapolate this idea, we could show the placement of the sun over time in three dimensional space by having a three dimensional box and then adding a line to indicate the fourth dimension.

Thinking of these characteristics of space and time as “dimensions” is, I believe, a bad metaphor for graphically displaying our models of reality. The term “dimension” makes us think of space, and so when we get to the fourth and higher dimensions, our minds can’t grapple with it. We aren’t using the right metaphor.

I prefer to use the metaphor called “attributes.” We are all plenty aware that things can have more than three or four attributes. We can think of hundreds for human beings. I believe if we think of space as something that tends to have 12 attributes, we’re better off at imagining it. With attributes, we don’t necessarily expect to be able to see all of them. We aren’t trying to jam twelve dimensions into a three-dimensional metaphor.

Remember, math is just another language, like French or Slovenian or Swahili. It is considered to be a good language to model the physical world with. Just because math is good at that doesn’t mean that we can’t understand the physical world in other languages.

Physicists use math to model space and time, and the math is complex, and that makes people feel like only physicists can understand what’s going on. This is not true. You can figure out a model of how space and time work using other languages. It might be clunkier, but it also might be easier to understand for a large number of people.

In any case, if we use different metaphors (and numerals and operations and relationships are also metaphors), science and math may be more accessible to people. They might bot burst a blood vessel trying to wrap their minds around 12 dimensional space. The issue of time as the fourth dimension would not be at all controversial, because we are not stuck with the metaphor of dimensions.

@wundayatta
Watch Discovery channel on Sunday night at 9 PM.
I saw the first two shows.
They are taking about Black wholes singularities and all such things.

I think it is a good way to understand it. I have read that time is no different to the spatial dimensions in a mathematical sense. Although we cannot significantly change the passage of time for ourselves, it is important to understand that changes in the rate of the passage of time are factors to explain other phenomena such as muons formed by cosmic rays.

I don’t think it’s a dimension because as you stated, it’s not one we can move about in. Except for Doctor Who, I’m sadly going to have to say it’s not practical to think of time as a 4th dimension.

@PacificToast
Watch Discovery Channel Sundays at nine PM.
I was amazed about the possibilities. I find it difficult to explain in detail.
I will leave it to Dr Kaku and Professor Hawking’s.

@wundayatta Very insightful answer. Thank you.

@FireMadeFlesh I can see that side of the question, but still feel it is a poor choice of wording that tends to further confuse an already difficult to access concept.

@philosopher Watching Stephen Hawking’s Universe is what brought this question into my mind.

@ETpro
I have about a million questions.
Cool question.
I wish we had a Physicist on fluther.
The Physicist admitted they have many unanswered questions.
They hope to develop technology that would make approaching a Black Whole possible . It sounds like something that will not happen for a long time.
It would be amazing to know if an alternate Universe exist on the other side of a Black Hole.

@philosopher Thanks. BTW, not to be a grammar pest, but I think you intended to say black hole and not whole. If they were studying a black whole, they might slice through it and make two balck halfs to better understand its inner workings. Too bad we can’t do that.

I am fascinated by the fact that the laws of physics break down inside a black hole. Time stops. So, nice place to visit if there were a way to get back out.

@ETpro
I agree and I always make errors when I am tried.
I love Science.

@philosopher I, too, find science fascinating. And not to worry about spelling errors. I owe what little I do manage to write properly to the help of the built-in Firefox highlighter that catches misspellings. But of course, it’s perfectly happy with whole for whole, and your for you’re. Some are bound to slip past the best spelling and grammar sweep.

@philosopher I have instant access to a physicist, and I often ask him to render his opinion on questions. This really isn’t a physics question, though, but a math one.

In the meanwhile we are only moving through clock time.

I understand the theoretical basis for seeing the relationship between space and time and to appreciate the 3 dimensions fully requires incorporating the temporal dimension as well. I believe the better we understand the parameters of space-time, the better we will understand the universe and how we relate to it.

@ETpro “I can see that side of the question, but still feel it is a poor choice of wording that tends to further confuse an already difficult to access concept.”

If time were not referred to as a dimension, we would not be able to understand light cones as well, or any other diagram that we use to help understand the implications of Relativity. It may be confusing at first to view time as a dimension, but it is far more difficult when you study it in depth if you haven’t been referring to it as such all along.

@Rarebear
I wish I had a Scientist to watch with me and asked questions.
I have to admit I took many Science classes in college. I complained back then but I learned a lot. Not enough to totally comprehend everything on Sundays show.
They have made many new discoveries.
I wish more people cared about Science because it will greatly effect the Human Race.
Thankfully we have people on here that don’t say, I don’t know. I hope this show can make young Child like Science too.