- #1

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but please..my teacher says time is a scalar quantity,my physics book also says so.

but time moves forward,why should it be a scalar?

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- Thread starter monty37
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- #1

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but please..my teacher says time is a scalar quantity,my physics book also says so.

but time moves forward,why should it be a scalar?

- #2

russ_watters

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- #3

atyy

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- #4

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much applies to direction,right.so according to einstenian physics,time is a vector

and according to newtonian physics,time is a scalar,right?

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Einstein Physics: Time is not a vector. Time is one component of a 4-vector.

- #6

atyy

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The elapsed time of a "stationary" observer is the "length" of his "velocity" vector integrated along his path in spacetime. This elasped time can be generalised for arbitrarily moving observers.

Maybe try looking up "4-velocity" and "proper time".

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now,putting it directly,if someone asks you if time is a scalar?

yes is the answer,right?

- #8

tiny-tim

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now,putting it directly,if someone asks you if time is a scalar?

yes is the answer,right?

Hi monty37!

Short answer:

Time is not a vector. Time is one component of a 4-vector.

- #9

DrGreg

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Tiny-Tim's answer is technically the correct answer, but I suspect it will go over the head of Monty37. I suspect he may not know the difference between proper time and coordinate time, and I'm pretty confident he hasn't studied tensors and therefore won't appreciate the tensor interpretation of "scalar" as "invariant".Hi monty37!

Short answer:Proper timeis a scalar.

Observed timeis neither a scalar nor a vector … asChrisassays, it's just a component of a vector …

Loosely speaking, yes "time is a scalar", in the non-tensor sense of a one-dimensional real number.

- #10

atyy

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A bit more correctly: Proper time is the elapsed time as read by a standard ideal clock, so it is a scalar. Standard ideal clocks moving at different velocities read different proper times.

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time?provide me a link, if you can on this.Also elaborate on tensors.

- #12

Fredrik

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He usually is.DrGreg is right!!!

See post #21 here.can someone tell me difference between proper time and coordinate

time?

Tensors are pretty difficult to understand, and not very important here. But see e.g. post #3 here. There's a lot more to be said about tensors, but I'm afraid it would mostly be gibberish to you if you haven't even studied linear algebra yet. You probably feel that way about the post I linked to as well, but maybe it's better than nothing.Also elaborate on tensors.

- #13

atyy

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time?provide me a link, if you can on this.Also elaborate on tensors.

If a person carries an ideal clock (like an atomic clock), and walks about, flies about, swim about etc, proper time is the time elapsed as read by the clock he is carrying. People carrying identical clocks, but moving in different ways, will have different proper time.

If we fill all of space with clocks that "do not move relative to each other", and define some "time" at which all the clocks are set to zero, then coordinate time at that location is the proper time on the clock at that location, ie. coordinate time is the proper time of a specific set of clocks moving in a specific set of ways.

If we are in Newtonian, non-relativistic physics, and we define one place to be the "origin" of a set of axes. Then for an object located away from the origin, there is a position vector from the origin to the object. The distance between the origin and the object is the "length" of the position vector. In this sense, "distance" is a function that takes a vector as input and produces a number as output. A tensor generalizes this idea: it is a function that takes one or more vectors as inputs and produces a number as output. In relativity, the vectors are vectors in spacetime, not just space alone.

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