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First off, I'd like to confess, I'm not a physicist, but this question, the one I'm about to ask, has been bothering me for quite some time. I have some basic knowledge of science and I'm afraid I can't get technical/mathematical at this point. If the question fails to meet the standards of Physics SE, kindly do let me know and I'll delete it or edit it; the former is more likely.

Ok, so let me begin.

I know that gravity causes time dilation and so does motion, the effect being noticeable in only in the extreme (massive objects or relativistic speeds). How would time dilation manifest for a chemical reaction? The reaction would slow down i.e. assuming the reaction is taking place in a spaceship travelling at 0.9c, an observer at rest will notice that the chemical reaction on the moving spaceship is taking longer than the same reaction at rest.

Cold also slows down chemical reactions. The mechanism of the slowing is different but the effect is equivalent i.e. it seems possible let the chemical reaction under normal conditions occur in a spaceship travelling at an appropriate speed such that the lengthened duration of the reaction is caused by time dilation, this duration being equal to the duration of the reaction at a lower temperature.

So, is cold equivalent to speed or gravity (with respect to time dilation)?

To reiterate, if the question is substandard, please say so and I'll delete it.

Gracias.

Hudjefa
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6 Answers6

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The difference is that temperature may slow down some reactions (usually by making some activation energy less available in the environment), cold can also speed up other reactions. Think of the transition of gelatin from liquid to colloid (solid-ish), which must happen in the refrigerator. Or consider that virus particles may replicate at body temperature, but die at slightly higher temperature, which is why we get fevers when sick.

Time dilation, on the other hand, affects all clocks in exactly the same way. In special relativity, there is no experiment either of us can do to decide whether you’re moving and I’m stationary, or vice-versa.

rob
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The effects are not really equivalent.

You could speed up a reaction by heating it. Or perhaps with a catalyst. OK, the reaction takes place at the same speed in both cases, but other things are different. Thermometers would have different readings for example. Or perhaps the air conditioner would turn on in one case but not the other.

mmesser314
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No, cold is not equivalent to speed or gravity in that sense. Cold will prolong some types of chemical reaction- ie it will increase the time interval between the start and end of the reaction as measured by a clock in the rest frame in which the reaction occurs. Speed will not affect the duration of the reaction in its own rest frame.

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I shall stress on "temperature" and "speed", not particularly on "cold"; without going into Special Relativity. And I shall put some mathematical expression for completeness, though I saw your no-math request.

In Thermodynamics there is a fundamental area known as Kinetic Theory. Among several of its consequences there is this link between temperature of a substance, and speed/velocity of the particles constituting that substance.

Assume a container filled with some sort of gas. That is, there are a lot of gas particles within it, whether $O_2$, $CO_2$ you name it. Now all these particles are in a state of constant, spontaneous, random motion (which is called Brownian Motion). And during this crazy movements, the particles collide with each other. The more energetic a particle is, the higher the chance of making a collision. And we have this well know expression for kinetic energy of a moving body: $\frac{1}{2}mv^2$ (m: body's mass, v: its speed). So clearly, the higher its speed, more energy it carries.
Now, when collision occurs, heat is generated. This is the fundamental origin of heat/temperature. No movement $\implies$ no heat. Also, there is this Equipartition Theorem, which results into the following equation (with simplification considered): \begin{equation} \frac{1}{2}mv^2 \propto k_BT \end{equation} ($k_B:$ Boltzmann Constant)
That is - temperature is very much linked with velocity (of constituent particles).

Let me know if it helps.

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Here's another way in which time dilation is not equivalent to cooling.

Let's put the chemical reaction on a spaceship inside a spherical shell of radius 10 light seconds with walls that are impenetrable to spaceships. Let's park the spaceship in the center of the shell.

If the physicist on the spaceship manipulates the rate of the chemical reaction by adjusting the temperature, the rocket ship need not move and will not hit the sides of the sphere.

If the physicist wants to use time dilation, then the physicist will need to accelerate the rocket ship in some direction to a good fraction of the speed of light.

First, note this will only change the reaction rate for an observer at rest with respect to the spaceship. The physicist on the ship will not see a change in reaction rate -- that's already a major difference with respect to adjusting the temperature.

Second, the spaceship will after of order 10 seconds run into the walls of the container. That clearly didn't happen in the situation where temperature was used to control the reaction rate, so this is yet another difference between these two separate concepts.

Andrew
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While this particular analogy might not be the best one, gravity and temperature are somehow related. Check "Unruh effect" and "Hawking radiation".

John
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