# Is Time a vector quantity?

by Amio
Tags: time, vector
P: 27
 Quote by quantumnick There are quantity which have three, but also quantity that have four or more ( also infinite) number of component but still remain scalar.
Well, well... I think I should take a break. :-)
P: 27
 Quote by D H You have to look at the space of which that vector is a member.
That post clarifies a lot.
Mentor
P: 15,167
 Quote by Matterwave I don't think it's productive to confuse the OP by giving him the mathematical definition of a vector space, or more abstract definitions of vectors in terms of coordinate transformations, etc., at this point.
Agreed.

Writing about concepts such as spinors and tensors, Lorentz and Poincaré transformations, QED and general relativity, or group theory IS NOT HELPING.

Yes, I broke the rules of the forum by shouting. Every once in a while that's needed.

On the other hand, giving a slight inkling into the concept of vector spaces sometimes does help in straightening out beginner misunderstandings with respect to vectors (the physics 101 version of a vector, something with a magnitude and a direction). A full blown treatment? No. That doesn't help.

 It seems to me that the OP is a beginner in physics who's simple concept of physical vector at this point is "a quantity with both magnitude and direction (in space as is usually implied)" whereas a scalar is something "only with magnitude (usually implied to be positive, like speed, or distance)".
Agreed. I take it that it's the sign that was confusing the OP rather than the dimensionality. If that's the case, pointing the OP to the paper "On determinism and well-posedness in multiple time dimensions" by Craig and Weinstein would fall in the category of "not helping".

If it's the sign that's the problem, Amio, consider temperature as an analogy. One way to express temperature is on an absolute scale, with zero meaning absolute zero. This makes all temperatures that will be encountered in an introductory physics class positive. However, telling someone that the high temperature tomorrow will be 308 K doesn't quite translate into "summer's here!". Telling them that the high will be 35 °C or 95 °F does. That Kelvin scale isn't as useful in the everyday world as are the Celsius or Fahrenheit scales. But now temperature can be negative.

One can in a way do that with time (please keep relativity out of this, everyone) by setting t=0 at the big bang. Doing that is not every useful in the everyday world.
Mentor
P: 17,318
 Quote by Amio I am beginner intro physics student. So I might be lacking in concept. That said; when we study 1D kinematics don't we consider 1D quantity like 1D velocity. 1D acceleration as vectors?
There is no benefit to doing so. None of non-trivial concepts of vectors are relevant to 1D motion. That is precisely why 1D motion is taught, because you can treat all of the quantities that are vectors in higher dimensions precisely as though they were scalars.

For example, for a 3D vector y like velocity then there is a difference between the operations ##x\;\mathbf{y}## where x is a scalar and ##\mathbf{x}\cdot\mathbf{y}## where x is a vector. There is no such difference if y is a 1D "vector" like time.
 P: 27 I think I got the idea. Thanks everyone.

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