I have read recently in many websites dedicated to science that China has made an artificial sun hotter than the 'sun'. My question is how did they make a thing that can withstand such a high temperature and not burn the earth ? related links :
I'm far from being an expert on this topic but I might trigger some more detailed answers so I will try my best to give a short intuitive explanation.
The general Idea in most nuclear fusion experiments is to produce a very hot plasma in which the fusion will take place and keep it trapped via a strong magnetic field so that it will not touch the walls of the fusion reactor.
In contrast to the fusion inside the sun where the fusion can take place mostly due to the high density of the plasma combined with a in comparison to the experiments on earth low temperature the density of the plasma inside such a reactor is very low. Therefore the total amount (mass) of plasma that is inside the reactor at the same time is very low (I remember a few grams) . This means that the energy density inside the reactor stays relatively low although the plasma is extremely hot. Due to this relatively low energy density it is possible to find materials that can withstand the generated heat.
So shortly speaking: A few gram of very hot plasma emit the same amount of energy as a lot of not so hot plasma. The temperature itself does not matter as long as the total amount of heat that is radiated towards the reactor material is not too high.