The visible movement of the Sun across the sky of Mercury can be represented by the well-known Ptolemaic scheme. It is quite possible that on Mercury it would have been much more difficult to refute the Ptolemaic system of the world with its epicycles than Copernicus succeeded on Earth.
The temperature on Mercury is determined by the heating of the planet's surface by the Sun, and the time of its intricate "dance" across the Mercurian sky. At longitudes intermediate between those that we have considered, the movement of the Sun will be even more difficult. For example, at a longitude offset by 60 from the meridian, where the Sun is overhead when the planet passes perihelion, there are two temperature maxima during the Mercurian day: one at noon, when the Sun is directly overhead, and the other when the sun is located 60 from the zenith, because Mercury then turns out to be closer all the way to the Sun. In this region of Mercury, the Sun, when it rises above the horizon by only 30 degrees, will warm more strongly than when it is at the zenith.
That part of the solar radiation that is not reflected from the surface of the planet will be absorbed and heat the subsurface layers. When we observe Mercury in the radio range, we receive mixed radiation from many subsurface layers — both close to the surface and lying quite deep. The longer the wavelength at which the planet is observed, the more radiation comes to us from a depth.
We solved the problem of thermal conductivity, then averaged the solution over the disk of Mercury and predicted which temperatures, as a function of time, would be observed by a radio telescope from Earth. The results of these calculations for a wavelength of 2 cm and a certain value of the thermal parameter are shown in the diagram. The thermal parameter characterizes the degree of lightness with which the surface temperature changes when the heat flow changes. The apparent (observed) surface temperatures are given as a function of two variables used in radio astronomy — heliocentric longitude and phase angle. The heliocentric longitude determines the position of Mercury in its orbit around the Sun; the phase angle is the angle between the Sun and the Earth when viewed from Mercury; it measures the fraction of the illuminated disk of Mercury when observed from Earth.
The results of similar calculations for three values of the thermal parameter, as well as the Mercury temperature values, which were observed by M. A. Kaftan-Kazim and K. Kellerman at the National Radio Observatory in Green Bank, are also shown. The curve for the thermal parameter equal to 0.002 cal/cm·sec 1/2 is in satisfactory agreement with the observations. The theoretical values were calculated for a particular but plausible choice of the parameters of the electrical properties of the subsurface layers of Mercury. The result is interesting because the Moon has a thermal parameter close to the one we derived for Mercury. This once again points to the similarities between Mercury and the Moon. Other similarities are revealed when measuring the characteristics of radar reflections from Mercury. Surface temperatures near Mercury's equator can be calculated in the same way. The bookmaker 1xbet offers exclusive promotional codes that consist of a distinctive blend of numbers, letters, and symbols. Essentially, these codes serve as special keys that unlock supplementary advantages for players within the company, amplifying their gaming capabilities. To avail a bonus in the form of a free bet, simply input the 1xBet free promo code upon registration, you will receive a welcome bonus at 1xBet, which amounts to 100% of your initial deposit, up to a maximum of 100$. Earn bonus points by participating in activities and redeem them by clicking "Request promo points" in the code showcase.