[hamdani yusuf (OP)]

What would happen if they interact?
What do you mean by "they"?

Those two objects with negative temperature but different magnitude.

Could you at least try to think about your questions a bit before you ask them?

[Bored chemist]

What would happen if they interact?
What do you mean by "they"?

Those two objects with negative temperature but different magnitude.

Could you at least try to think about your questions a bit before you ask them?

It depends on the objects and what sort of negative temperatures they have.

[hamdani yusuf (OP)]

It depends on the objects and what sort of negative temperatures they have.

How many kinds of negative temperature are there?  What makes them different?

[Bored chemist]

In a HeNe laser the electronic temperature is negative.
In the ammonia maser the rotational  (I think- might be something odd like a spin flip) temperature is negative.
In the hydrogen maser the electron spin temperature is negative.

There are other sorts too.

[hamdani yusuf (OP)]

Here's my first video on investigation of thermodynamics.

Demonstrating the effect of emissivity on infrared thermal camera measurement.

[hamdani yusuf (OP)]

In a HeNe laser the electronic temperature is negative.
In the ammonia maser the rotational  (I think- might be something odd like a spin flip) temperature is negative.
In the hydrogen maser the electron spin temperature is negative.

There are other sorts too.

Negative value can be assigned to a physical parameter if it negates or cancels out the positive value of the same physical parameter. Otherwise, it shouldn't be assigned a negative value.

[alancalverd]

Gravitational potential is very real and always negative.

[hamdani yusuf (OP)]

A Recipe for Cooling Atoms to Almost Absolute Zero

NASA’s Cold Atom Lab aboard the International Space Station cools atoms down to a billionth of a degree above absolute zero, or the temperature at which atoms should stop moving entirely. Nowhere in the universe are there atoms that reach this temperature naturally. But how do scientists accomplish this feat? It’s a three-step process that starts with scientists hitting the atoms with precisely-tuned lasers to slow them down.
 
The colder atoms are, the slower they move, and the easier they are to study. Ultracold atoms can also form a fifth state of matter, called a Bose-Einstein condensate (BEC). Learning about the fundamental properties of atoms has laid the foundation for technologies that most of us use every day, such as computers. As the first ultracold atom facility in Earth orbit, Cold Atom Lab is opening up new avenues for investigation.

Here are some other videos explaining about laser cooling.

From 2:22 of the last video, we can infer that to make it work, the frequency of the laser is set to be slightly lower than transition frequency of the atoms to be cooled. Thus, a certain frequency of laser can cool some type of atoms, but heat other types of atoms instead. Which means that it doesn't always have negative temperature.

[Bored chemist]

Negative value can be assigned to a physical parameter if it negates or cancels out the positive value of the same physical parameter.

So what?

[Bored chemist]

Which means that it doesn't always have negative temperature.

No
You have missed the point.
It's sad, but no surprise.
You just don't seem to have what it takes to understand this.
You should probably stop wasting time trying.
The process called "laser cooling" but that is a misnomer.
You don't need a laser to do it.
Using a laser is by far the most sensible way but, in principle you could use a different light source.

So laser cooling has nothing to do with the negative temperature in a laser.

[alancalverd]

The concept of negative temperature derives from a definition of temperature in terms of entropy. All it means is a condition where adding energy to a system decreases its entropy.

[hamdani yusuf (OP)]

Using a laser is by far the most sensible way but, in principle you could use a different light source.

What other kinds of light can be used for cooling? Do you have any source?

[hamdani yusuf (OP)]

The concept of negative temperature derives from a definition of temperature in terms of entropy. All it means is a condition where adding energy to a system decreases its entropy.

Do laser cutters decrease entropy?

[hamdani yusuf (OP)]

Gravitational potential is very real and always negative.

In classical mechanics, the gravitational potential at a location is equal to the work (energy transferred) per unit mass that would be needed to move an object to that location from a fixed reference location. It is analogous to the electric potential with mass playing the role of charge. The reference location, where the potential is zero, is by convention infinitely far away from any mass, resulting in a negative potential at any finite distance.
https://en.wikipedia.org/wiki/Gravitational_potential

When the reference location has negative gravitational potential, gravitational potential at some location can have positive value.

[hamdani yusuf (OP)]

Negative value can be assigned to a physical parameter if it negates or cancels out the positive value of the same physical parameter.

So what?

If it cannot negate positive value of the same parameter, it should not be assigned a negative value.

[hamdani yusuf (OP)]

In a HeNe laser the electronic temperature is negative.

What's the magnitude, in Kelvin?

[alancalverd]

Do laser cutters decrease entropy?

no.

[hamdani yusuf (OP)]

Do laser cutters decrease entropy?

no.

So, they don't have negative temperature.

[Bored chemist]

Negative value can be assigned to a physical parameter if it negates or cancels out the positive value of the same physical parameter.

So what?

If it cannot negate positive value of the same parameter, it should not be assigned a negative value.

But it can so... what was your point?

[Bored chemist]

In a HeNe laser the electronic temperature is negative.

What's the magnitude, in Kelvin?

I'd have to do lots of complicated maths but, for the sake of discussion, let's pretend that I have done it and the answer is minus 5000K.

What use are you going to make of that information?
Because, if you don't have a good answer, I'm going to take it as further proof that you are a troll.
It will prove that you were just trying to trick me into doing lots of pointless work.