Note to SSDD: Here is an example of thermal energy from a cold substance hitting a warmer substance.
The cosmic ray background (CRB) was discovered with a radio telescope. The CRB is a cold 2.725 deg K. Radio telescopes are at ambient outdoor temperatures, averaging 15 deg C. The CRB reflects from the much warmer parabola dish to a ruby maser at the focal point.
This illustrates that thermal energy from a cold substance can strike a much warmer substance and be detected to have done so.
Sorry. but it doesn't. Funny how willing people are to fool themselves with their instrumentation. A radio telescope was used to first record CMB. A radio telescope tunes to varying resonance frequencies of an antenna which, in turn creates an electrical signal which then gets amplified in order to create a recording over a particular frequency or spectrum.
Then that recording is matched up to a black body spectrum in accordance with Plank's law and the peak of that recording is used to determine the temperature from which a radiance can be determined, again, using Plank's law. The recorded spectrum is being translated, using Plank's law into a radiance which is measured in W/m2.
A radio spectrum is being recorded and from that a radiance is being computed....similar in many ways to the so called measurements of back radiation....no actual measurement is being made...the measurements are artifacts of mathematical models...not actual measurements of radiation.