Melting Rocks with Sunshine

Just How Hot is Hot? How do they know it?

Jem Stansfield traveled to the Solar Furnace Research Facility in Southern France and witnesses the incredible power generated by highly concentrated sunlight in this YouTube video. It can really heat up things! shows the same video with the following commentary and comments:

On average, there’s about 1.366 kilowatts per square meter (kW/m??) of solar radiation hitting the surface of the Earth at any moment (on the day side, obviously).

See also: Melting Steel With Only the Sun (Video)

Via BBC, Laughingsquid

Visit: and??

Brian Barrett, the author of this article (, says at the Gizmodo story on these feats,Just how hot does it get in that ring of fire sunshine? Over 6,300 degrees Fahrenheit.”

Well, 6300 ??F is nearly 3483 ??C or about 3750 K. That’s above the upper temperature capability of any commercially available temperature measurement device.

In the two examples shown, meting rocks and melting steel, the approximate temperatures can be estimated from the melting temperature property of the materials. According to Wikipedia, “The chemical element with the highest melting point is tungsten, at 3683 K (3410 ??C, 6170 ??F).”

The highest temperature measuring thermocouple, the Tungsten/Tungsten-26% Rhenium thermocouple, has an upper limit of about 2700 K and the top temperature scale of any Radiation Thermometer is about 3300 K?

So, one has to wonder how the solar furnace people can estimate their highest temperature capability. For that matter, how did someone actually determine the melting point of Tungsten?

Would anyone like to challenge those temperature measurement results or estimates? Or, better still, explain the physics behind such an estimate?

So, how do they measure temperature above the highest known measurement device capabilities?