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Comment by CriticalCathed | Hacker News Reader

>And on the other side of the boundary, the interstellar medium is at least 54,000 degrees Fahrenheit, which is hotter than expected. However, this plasma is so thin and diffuse, the average temperature around the Voyager probes remains extremely cold.

I don't understand this. If the medium is 54,000 degrees wouldn't it have incinerated the probes? How can an extremely diffuse plasma be 54,000 degrees and yet also be extremely cold?

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Temperature relates to how fast atoms are moving. If they're moving very fast, then we say it's very hot. Damage from high temperature however requires a substantial quantity of those atoms, not just that they be moving quickly.

But there are very very few atoms in the interstellar medium. They are moving very fast, but there are very few of them indeed.

To incinerate something, there would need to be a lot of atoms indeed moving at high temperature. An isolated atom hitting the probe, even at relatively high speed, won't be doing much incinerating.

It's like a sparrow hitting a building. Won't do much, even it's a fast-moving sparrow. But a billion sparrows hitting it in unison - that might be a problem.

But there once was this Diamond Mountain in Lower Pomerania...

Have you ever reached into a hot oven and grabbed a sheet of tinfoil with your bare hands? The foil is 350F (or hotter) but you don't feel anything because it's so thin and flimsy. There is not enough mass to hold enough energy to hurt you.

seriously? I assumed that it simply cooled more quickly because of high surface area to mass ratio; not that it actually was 400F but I couldn't feel it.

It doesn't make intuitive sense to me but I do understand the explanation.

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