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Zero Kelvin is understandable that all molecules kinetic energy is Zero

But what is Negative Kelvin, means negative kinetic energy ? How can a body will have negative energy ?

As explained on this Wikipedia page, (formally) negative temperatures can result for systems with bounded phase space.

What this means is that the entropy decrease when the energy increases.

This is probably easiest to understand for the finite discrete system of $N$ non-interacting two-level atoms (having level energy $\pm \epsilon$) discussed on the Wikipedia page.

The temperature can be calculated exactly as: $$ \frac{1}{T} = \frac{1}{2}\ln\left(\frac{N+1-E}{N+1+E}\right)\;, $$ where, for simplicity, I set $k=\epsilon=1$, so the value of $E$ ranges from $-N$ to $N$. The temperature is zero when $E=0$ and the temperature is negative when $E$ is positive.

You can start to understand this, for example, by considering the highest energy state. Just like the lowest energy state, the highest energy state is perfectly ordered, having all atoms in the upper state. Thus, just like the lowest energy state, the highest energy state also has zero entropy. Thus, as we approached the highest energy state from below the entropy must have been decreasing.

In this bounded system the entropy is actually largest when $E=0$, therefore the entropy decreases when either $E$ increases away from zero (negative temperature) or when $E$ decreases away from zero (positive temperature).

Zero Kelvin is understandable that all molecules kinetic energy is Zero

But what is Negative Kelvin, means negative kinetic energy ? How can a body will have negative energy ?

As explained on this Wikipedia page, (formally) negative temperatures can result for systems with bounded phase space.

What this means is that the entropy decreases when the energy increases.

This is probably easiest to understand for the finite discrete system of $N$ non-interacting two-level atoms (having level energy $\pm \epsilon$) discussed on the Wikipedia page.

The temperature can be calculated exactly as: $$ \frac{1}{T} = \frac{1}{2}\ln\left(\frac{N+1-E}{N+1+E}\right)\;, $$ where, for simplicity, I set $k=\epsilon=1$, so the value of $E$ ranges from $-N$ to $N$. The temperature is zero when $E=0$ and the temperature is negative when $E$ is positive.

You can start to understand this, for example, by considering the highest energy state. Just like the lowest energy state, the highest energy state is perfectly ordered, having all atoms in the upper state. Thus, just like the lowest energy state, the highest energy state also has zero entropy. Thus, as we approached the highest energy state from below the entropy must have been decreasing.

In this bounded system the entropy is actually largest when $E=0$, therefore the entropy decreases when either $E$ increases away from zero (negative temperature) or when $E$ decreases away from zero (positive temperature).

Zero Kelvin is understandable that all molecules kinetic energy is Zero

But what is Negative Kelvin, means negative kinetic energy ? How can a body will have negative energy ?

As explained on this Wikipedia page, (formally) negative temperatures can result for systems with bounded phase space.

What this means is that the entropy decrease when the energy increases.

This is probably easiest to understand for the finite discrete system of $N$ non-interacting two-level atoms (having level energy $\pm \epsilon$) discussed on the Wikipedia page.

The temperature can be calculated exactly as: $$ \frac{1}{T} = \frac{1}{2}\ln(\frac{N+1-E}{N+1+E})\;, $$ where, for simplicity, I set $k=\epsilon=1$, so the value of $E$ ranges from $-N$ to $N$. The temperature is zero when $E=0$ and the temperature is negative when $E$ is positive.

You can start to understand this, for example, by considering the highest energy state. Just like the lowest energy state, the highest energy state is perfectly ordered, having all atoms in the upper state. Thus, just like the lowest energy state, the highest energy state also has zero entropy. Thus, as we approached the highest energy state from below the entropy must have been decreasing.

In this bounded system the entropy is actually largest when $E=0$, therefore the entropy decreases when either $E$ increases away from zero (negative temperature) or when $E$ decreases away from zero (positive temperature).

Zero Kelvin is understandable that all molecules kinetic energy is Zero

But what is Negative Kelvin, means negative kinetic energy ? How can a body will have negative energy ?

As explained on this Wikipedia page, (formally) negative temperatures can result for systems with bounded phase space.

What this means is that the entropy decrease when the energy increases.

This is probably easiest to understand for the finite discrete system of $N$ non-interacting two-level atoms (having level energy $\pm \epsilon$) discussed on the Wikipedia page.

The temperature can be calculated exactly as: $$ \frac{1}{T} = \frac{1}{2}\ln\left(\frac{N+1-E}{N+1+E}\right)\;, $$ where, for simplicity, I set $k=\epsilon=1$, so the value of $E$ ranges from $-N$ to $N$. The temperature is zero when $E=0$ and the temperature is negative when $E$ is positive.

You can start to understand this, for example, by considering the highest energy state. Just like the lowest energy state, the highest energy state is perfectly ordered, having all atoms in the upper state. Thus, just like the lowest energy state, the highest energy state also has zero entropy. Thus, as we approached the highest energy state from below the entropy must have been decreasing.

In this bounded system the entropy is actually largest when $E=0$, therefore the entropy decreases when either $E$ increases away from zero (negative temperature) or when $E$ decreases away from zero (positive temperature).

Zero Kelvin is understandable that all molecules kinetic energy is Zero

But what is Negative Kelvin, means negative kinetic energy ? How can a body will have negative energy ?

As explained on this Wikipedia page, (formally) negative temperatures can result for systems with bounded phase space.

What this means is that the entropy decrease when the energy increases.

This is probably easiest to understand for finite discrete systems, e.g., the system of $N$ non-interacting two-level atoms (having level energy $\pm \epsilon$) discussed on the Wikipedia page.

The temperature can be calculated exactly as: $$ \frac{1}{T} = \frac{1}{2}\ln(\frac{N+1-E}{N+1+E})\;, $$ where, for simplicity, I set $k=\epsilon=1$, so the value of $E$ ranges from $-N$ to $N$. The temperature is zero when $E=0$ and the temperature is negative when $E$ is positive.

You can start to understand this, for example, by considering the highest energy state. Just like the lowest energy state, the highest energy state is perfectly ordered, having all atoms in the upper state. Thus, just like the lowest energy state, the highest energy state also has zero entropy. Thus, as we approached it from below the entropy must have been decreasing.

In this bounded system the entropy is actually largest when $E=0$, therefore the entropy decreases when either $E$ increases away from zero (negative temperature) or when $E$ decreases away from zero (positive temperature).

Zero Kelvin is understandable that all molecules kinetic energy is Zero

But what is Negative Kelvin, means negative kinetic energy ? How can a body will have negative energy ?

As explained on this Wikipedia page, (formally) negative temperatures can result for systems with bounded phase space.

What this means is that the entropy decrease when the energy increases.

This is probably easiest to understand for the finite discrete system of $N$ non-interacting two-level atoms (having level energy $\pm \epsilon$) discussed on the Wikipedia page.

The temperature can be calculated exactly as: $$ \frac{1}{T} = \frac{1}{2}\ln(\frac{N+1-E}{N+1+E})\;, $$ where, for simplicity, I set $k=\epsilon=1$, so the value of $E$ ranges from $-N$ to $N$. The temperature is zero when $E=0$ and the temperature is negative when $E$ is positive.

You can start to understand this, for example, by considering the highest energy state. Just like the lowest energy state, the highest energy state is perfectly ordered, having all atoms in the upper state. Thus, just like the lowest energy state, the highest energy state also has zero entropy. Thus, as we approached the highest energy state from below the entropy must have been decreasing.

In this bounded system the entropy is actually largest when $E=0$, therefore the entropy decreases when either $E$ increases away from zero (negative temperature) or when $E$ decreases away from zero (positive temperature).