Is the theory of heat death testable?

Question

Given the following statements, I arrived at the conclusion that heat death is not a scientific theory. Can someone please confirm my argument or find where I went wrong?

1. Given an arbitrary particle with an arbitrary state, a non-zero amount of work is required to change its state

2. At heat death, the universe has no thermodynamic free energy, and hence, no work can be performed

3. Given statement 1 and 2, no particle can change state at heat death

4. An observer is a system of particles

5. An observation implies a change in state within this system

6. Given statement 3 and 5, an observation is impossible at heat death

7. Since observations are impossible at heat death, the heat death theory is untestable, and hence, is not scientific

Answer 1

"Given statement 1 and 2, no particle can change state at heat death"

Not necessarily. At heat death, particles may still be bouncing around.

https://en.wikipedia.org/wiki/Heat_death_of_the_universe#Current_status

"If the cosmological constant is zero, the universe will approach absolute zero temperature over a very long timescale. However, if the cosmological constant is positive, as appears to be the case in recent observations, the temperature will asymptote to a non-zero positive value, and the universe will approach a state of maximum entropy in which no further work is possible"

When the heat death temperature is above absolute zero, particles are still bouncing off each other and changing position and velocity. It's just that in heat death they are uniformly mixed, at thermodynamic equilibrium, and cannot be used to do any thermodynamic work.

However, you are right that direct observations of heat death are impossible. (Except for Boltzmann brains)

But it would be too restrictive to say, on this basis, that it's not scientific. We can't observe heat death from inside a universe in heat death, but we can look at it "from a distance" (a distance in time) and see the signs. Many billions of years in the future humanity may still be around, and experiencing a universe on an inevitable slide towards heat death - they won't experience heat death itself, because they will be dead first, but they can experience the progress towards it.

We can't observe a nuclear explosion from inside the explosion, either. But this does not mean nuclear explosions are not science. We can observe them from a distance.