If the side of planet Mercury facing "the Sun" is hot, and the opposite side cold, Then is in-between just right?

Mercury spins on its axis once every 60 Earth days. Link. So at any instant of time there must be a sweet spot, but it keeps on moving. To keep at a reasonable temperature, you would have to walk around the planet every 60 days.

The article says that there may be permanently low temperatures at the poles. Could there be a sweet spot near the poles?

There is no atmosphere so it’s either hot or cold. No in between.

@LostInParadise thanks for that info! Somehow I missed that new information. Back in the day, we learned that Mercury always had the same side of the planet facing the Sun, and I hadn’t heard that it had been discovered that it rotates fully 360 Earth days. But then again, I still insist that Pluto is a planet, lol!

^^ Me too…poor ole Pluto!

The day-night terminator on a gravitationally locked planet would have a temperature between the two extremes, but depending on the intensity of the sunlight and the atmospheric retention of heat, it might still be too hot/too cold for humans, so you would have to move closer to the day or night side, depending on circumstances.

Well, you would want to do your best, since the surface temperature ranges between 800 F and -279 F . . .

So it sounds like humans would like to stay in a certain (moving) ring on the dark side. The desirable ring would not only move over the surface, but also vary in diameter throughout Mercury’s year, because it’s a relatively eccentric orbit, so it gets nearer and closer to the sun. The year is also pretty close to the time of a Mercury day – about 88 Earth days.

Fortunately, the rotation speed is under 7 MPH. Slowest near the poles.

I read a science fiction book where there was a city on Mercury that crept around the planet as it turned, staying at the terminus.

I expect this would be like setting your torso on fire with your head in the freezer. There’s a balance of concepts, but in practice you will look very silly, very dead or both.

Maybe there’s a place, somewhere near a pole where the light is more diffuse, and the distance around the sphere is small enough to circumnavigate regularly, but in reality, it’s way easier to create devices to heat and cool bodies, rather than trying to stay in one place where the temperature, (if not atmosphere, or UV levels) are ideal.