# Speed of Time

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I have a question from the following statement in this article that I can't understand.

How can our speed traveling in time be the speed of light? I realise our measure of time, such as seconds, minutes, is purely artificial, so how is our movement through time measured? For anything travelling at the speed of light, you would need infinite energy to accelerate the object to light speed. I don't see an infinite energy propelling my desk or me to light speed. What's going on here?

"We know through the physics of Einstein's special theory of relativity that you can trade motion in space for motion in time. If you're standing perfectly still, you're moving through the dimension of time at a particular speed (the speed of light, for those of you who are curious)." https://phys.org/news/2020-05-future-totally.html

Here's a bonus question - time decreases the faster you get, and the examples given are always straight linear motion relative to an observer.

What if you put a moving observer inside a cyclotron - he sits in the middle (not spinning), and the cyclotron spins around him at the speed of light.

Would time stop for him, or does he physically need to me moving/spinning.

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1 hour ago, M.Ross said:

I have a question from the following statement in this article that I can't understand.

How can our speed traveling in time be the speed of light? I realise our measure of time, such as seconds, minutes, is purely artificial, so how is our movement through time measured? For anything travelling at the speed of light, you would need infinite energy to accelerate the object to light speed. I don't see an infinite energy propelling my desk or me to light speed. What's going on here?

"We know through the physics of Einstein's special theory of relativity that you can trade motion in space for motion in time. If you're standing perfectly still, you're moving through the dimension of time at a particular speed (the speed of light, for those of you who are curious)." https://phys.org/news/2020-05-future-totally.html

There is a concept in relativity known as the velocity four-vector (aka four-velocity). The components are the spatial velocity vectors and gamma*c for the time component, which has the opposite sign of the spatial components

The magnitude of this vector is always c^2. If you are at rest, the time time proceeds normally, with a magnitude of c. If you have a velocity, then the time component is reduced.

1 hour ago, M.Ross said:

Here's a bonus question - time decreases the faster you get, and the examples given are always straight linear motion relative to an observer.

What if you put a moving observer inside a cyclotron - he sits in the middle (not spinning), and the cyclotron spins around him at the speed of light.

Would time stop for him, or does he physically need to me moving/spinning.

You are always at rest in your own frame and time runs normally for you. Nothing with mass can move at c, so this is a non-issue. The objects in the cyclotron will have their time run slow according to that central observer.

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• 11 months later...

It doesn't seem like you are traveling through time at c because everything else is going with you.  But there is way more to this than what I just said.

Maybe a rough analogy is to imagine an ant sitting on top of a table in a 2 dimensional scenario.  Now imagine as time goes the ant and the table gets closer and closer to the ceiling.  The ant does not realize he is moving towards the ceiling because he can only see along the table because he and the table are only 2 dimensional.

But that analogy just needs a little addition to be more realistic.  Instead of the ant and the table "moving" towards the ceiling through space, the ant and the table exist in a series of many layers that "grow" toward the ceiling.

And to add a little to the addition, the "block" that grows to the ceiling is not a 3d Euclidean block, but a 3d block that cannot be visualized, called a Minkowski space.

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The model for relativity uses the concept of space-time, and the distance, in space-time, between events.
This distance uses the Pythagorean theorem for distances, such that the square of the distance is equal to the square of the spatial dimensions and the time dimension.
To get a distance squared, from a time squared, it needs to be multiplied by a speed squared, which in this case, is -c2.

This is the model; are you really travelling at c ?

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13 hours ago, MigL said:

The model for relativity uses the concept of space-time, and the distance, in space-time, between events.
This distance uses the Pythagorean theorem for distances, such that the square of the distance is equal to the square of the spatial dimensions and the time dimension.
To get a distance squared, from a time squared, it needs to be multiplied by a speed squared, which in this case, is -c2.

This is the model; are you really travelling at c ?

If I throw a boomerang in the air and it returns to me after traveling a  distance of 1 light second and having travelled at a significant fraction of c  the boomerang's clock presumably  moves at a  slower rate than mine.(when I am able to make a physical comparison)

Conversely my clock's rate  is faster than its(the boomerang's)

If the boomerang travels as close to c as is practically possible does the rate of my clock compared to its clock  approach a value  that is equal to c?

Does that shed any light on the expression that we are "traveling through time at the speed of light (c)?

Edited by geordief
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3 hours ago, geordief said:

If the boomerang travels as close to c as is practically possible does the rate of my clock compared to its clock  approach a value  that is equal to c?

No, it approaches infinity.

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if a giant man standing had arms that where in length 299,792,458 metres  and he clapped his hands,  from start to clap it took him .2 of a second. what would happen to his hands?

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17 minutes ago, FRAGMASTER2023 said:

if a giant man standing had arms that where in length 299,792,458 metres  and he clapped his hands,  from start to clap it took him .2 of a second. what would happen to his hands?

What do the length of the arms and the duration of the clap have to do with the question?

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;

Minkowski inflated the time scale for a space-time plot from t to ct, enabling an analysis of extremely short durations of time, and allowed comparisons of object motion to light motion (apples to apples), or vt/ct, which equals v/c or speed. With two possible directions ±(x, y, z), a history of each position with a corresponding time, becomes a velocity profile. It is not interpreted as a geographical map.

In the standard example, Ut is the time scale for the reference frame and Ux is the x coordinate for A moving at .5c relative to U. An object moving at c is represented by the blue line with a slope of 45º, which can only be light. The red calibration curve (as labeled by Max Born) represents a constant time wherever it intersects a velocity profile. The spatial units will match the time units. Thus x=5 light sec. when Ut=10 light sec, and At=8.66 light sec.

When Einstein developed Special Relativity, he defined the sum of squares of the velocity components (x, y, z) as an invariant interval S, and the corresponding time for that interval as S/c. Minkowski did what mathematicians do, simplify and generalize by redefining Einstein's time variable using complex notation as -ict, I.e. it is only a mathematical 4th dimension. The 'time' identity was removed when it became must another line.

Moving in time is a metaphorical expression popularized by scientists such as Brian Green in books and on PBS.

Referring to the plot, if A remains at Ux=0, there is no motion, but his clock keeps ticking. If the velocity components =0, t=0/c=0.

If the clock moved at c, it would cease to function as a clock

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On 6/10/2023 at 4:12 AM, Genady said:

What do the length of the arms and the duration of the clap have to do with the question?

Presumably if information can't be transmitted faster than light then initiating the motion at the shoulders would result in the hands moving later, or something, wouldn't it?

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25 minutes ago, exchemist said:

Presumably if information can't be transmitted faster than light then initiating the motion at the shoulders would result in the hands moving later, or something, wouldn't it?

Yes, of course.

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• 2 months later...
On 6/10/2023 at 4:12 AM, Genady said:

What do the length of the arms and the duration of the clap have to do with the question?

Well my good man , if his theoretically long arms where th elength i posted that would be the distance that light would travel in one second, so if he clapped his hands he would probably do this in under that time frame meaning his arms at his elbows only travelled 8 inches in that second to bring closed his hands , but his hads being on those impossibly long arms? projected on the same angle. of trajectory , would most likely be over that light per second distance , so it would have to travel over a light year in under a second , theoretically of course.

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3 hours ago, FRAGMASTER2023 said:

Well my good man , if his theoretically long arms where th elength i posted that would be the distance that light would travel in one second, so if he clapped his hands he would probably do this in under that time frame meaning his arms at his elbows only travelled 8 inches in that second to bring closed his hands , but his hads being on those impossibly long arms? projected on the same angle. of trajectory , would most likely be over that light per second distance , so it would have to travel over a light year in under a second , theoretically of course.

His arms will not remain straight. From the initiation of the move near the shoulders until the hands start moving, at least one second will pass.

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• 3 weeks later...

We cant possibly even touch the speed of light-

According to the special relativity theory relative mass increases with the increase of velocity . the nearer we are to the speed of light the more mass the object gets.

The equation for this phenomenon is     m0/ 1 - (v)sq/ (c)sq

if we let the original mass to be even the lightest of for eg 1kg then the equation will result in something like this  - 1kg/1-( (3 x 10^5)km^2/(3 x 10^5)km^2)   == 1kg/ 1 - (1) = 1kg/0 = ∞ . now if the relative mass = ∞ according to Einstein's equation e= mc^2. the energy required to move an object of ∞ mass would be ∞ itself. The energy in the universe itself is finite then how in the batmobile will we be able to harness infinity energy.

*Light travels at this speed cuz it aint no relative

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Forget "relative mass".

(It's a deprecated concept. Modern physics has pretty much dropped the idea.)

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7 hours ago, IamBATMAN said:

the energy required to move an object ...

But you don't have to move an object. Instead of moving the object, pick an observer that moves faster than light relative to the object.

The object moves faster than light relative to that observer.

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But you don't have to move an object. Instead of moving the object, pick an observer that moves faster than light relative to the object.

The object moves faster than light relative to that observer.

But that just begs the question - how does the observer move that fast?

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23 minutes ago, swansont said:

But that just begs the question - how does the observer move that fast?

He just does. Why not?

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He just does. Why not?

Because it’s unphysical

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15 minutes ago, swansont said:

Because it’s unphysical

Yes. This or similar, i.e., causality is a correct explanation of not moving faster than light rather than an infinite energy required for the acceleration.

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Yes. This or similar, i.e., causality is a correct explanation of not moving faster than light rather than an infinite energy required for the acceleration.

If you had infinite energy could you end up breaking the "fabric" of the universe ? (semi seriously)

I mean "blow it apart"

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1 minute ago, geordief said:

If you had infinite energy could you end up breaking the "fabric" of the universe ? (semi seriously)

I mean "blow it apart"

No.

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Yes. This or similar, i.e., causality is a correct explanation of not moving faster than light rather than an infinite energy required for the acceleration.

Both. As the saying goes, relativity, causality, FTL: pick two. You can have causality and FTL if you discard relativity, but relativity is consistent with experiment.

No.

Why not?

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15 minutes ago, geordief said:

Why not?

Because GR does not require an assumption of finite energy.

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