Whats the hottest temperature humans have ever managed to heat a body and keep it at that temperature for more than 1 hour ?
Caveat 1 : Body weight (mass) > 1 lb (500g)
Caveat 2 : Must be one continuous body (100 lightbulb filaments does not count)
My WAG would be a fusion reactor.
I don’t think the plasma in a fusion reactor is greater than one pound.
Also, although this may have since been exceeded, the longest reported time a fusion reactor has operated continuously is only 210 seconds:
I’m thinking that the general difficulty of containing a plasma for an extended period means that something else (nowhere near as hot) is much more likely to meet the OP’s criteria, but I have no idea what that may be.
Obviously in scientific research many small things may get very hot for small amounts of time. But if you want something larger, very hot, for long periods of time, my guess would be some small but expensive furnace that is necessary for some niche item or material.
I have no idea what it may be. Something for making elemental tungsten?
How about the heat shield from a space capsule reentry? Although I don’t know if it goes through the atmosphere for an hour… and i guess that’s not really ‘on earth’.
Could the answer be an IMAX projector? They run at temperatures hotter than the sun for hours.
In an underground nuclear test, the initial temperature is north of 100 million degrees. (Leaf to p 32) So for humans heating up a large mass for at least an hour, my guess would be the melt cavity of a large test such as Cannikin.
However I don’t know how hot the rock actually gets (obviously nothing close to the initial temperature of the bomb itself), nor how long it stays toasty.
How about a glass furnace? Is that hotter than the steel in a blast furnace?
For an underground nuclear test, I have to imagine the cavity would stay pretty warm for a very long time. After all, where else can the heat escape to?
That would be my first guess. Carbon is the only element with a higher melting point, but I doubt anyone has usefully melted significant quantities for any serious amount of time.
You need it to be liquid, getting 500g of vapour or plasma it is going to be quite difficult, especially for an hour. Tungsten boils at one atmosphere at 5,555C, which is impressive, and Tungsten Carbide at 6,000C. Whether anyone has bothered to take a large mass of either of these to their boiling points I don’t know, but these would have to be close to any reasonable limit. Not clear what you hold them in to do it.
For liquids, Ta[sub]4[/sub]HfC[sub]5[/sub], Tantalum Hafnium Carbide seems to be close to the record, with a melting point of 4,215C. But no-one seems to have managed to melt any serious amounts of it, the very small production being a sintered powder.
It would be interesting to do the heat flow for an underground nuke, but I actually doubt it would meet the OP’s criteria.
I’m going to bet on liquid tungsten. 3,422C.
Perhaps it would be a large electric arc furnace:
http://www.siemens.com/innovation/en/news/2011/an-eye-that-measures-liquid-steel-temperatures.htm
More specifically, the region around the tip of one of the three electrodes. These things are carbon and they’re big. I think selecting the hottest 1 pound around the tip would qualify. I kind of think the surface of the electrode where the carbon is melting and disintegrating operates around 5 kK, but the temperature would be falling off pretty rapidly as you move away from there. Nonetheless, if this region is rapidly exporting heat to a steel melt, it’s doing so by being much hotter.
I don’t think anybody holds liquid tungsten. The solid forms of tungsten I’m familiar with are sintered from powder, which process is done below the melting point, and little beads that are much smaller than a pound and are kept liquid for seconds.
Online refs say the temperature at the tip of a carbon arc lamp electrode is more like 3600 C, so I was pretty overoptimistic there.
I think carbon arc lights operating on DC get hotter than arc furnaces operating on AC, because the positive electrode gets most of the heat and forms a pool of liquid carbon that incandesces to create most of the light. Thus, a big arc furnace wouldn’t have anything as high as 3600 C.
A thermite reaction between tantalum and iodine pentoxide can potentially reach a temperature of 7240°C. cite