# Why does Relativity effect the melting point of mercury?

I know there is a related question, that references the Dirac Equation, that relies on relativity, but I've just watched this video:

Which seems to say there is something new on this topic? What specifically has changed in our understanding?

Here is the paper he references.

In short, he (in the video) says that as mercury is large, it's electrons have to orbit really fast to not get sucked in. As they move much faster they approach c and gain mass meaning they are less able to bond with other mercury atoms.

for a start, I know that electrons fill shells and the bohr model of 'orbits' is quite naive.

The abstract of the paper says :

An old problem solved: Monte Carlo simulations using the diatomic-in-molecule method derived from accurate ground- and excited-state relativistic calculations for Hg2 show that the melting temperature for bulk mercury is lowered by 105 K, which is due to relativistic effects.

Which doesn't tell me much.

So, what new information do we have about the melting point of mercury due to relativity?

• It's very time-consuming for people to watch a video in order to find out what your question is. Please summarize the relevant material from the video. The purpose of SE is not really to answer your question, it's to build a body of questions and answers that will be useful to other people. This question, in its present form, is unlikely to be useful to other people. – user4552 Aug 20 '13 at 21:45
• @BenCrowell I've tried to summarise it now in my edit. I was more expecting people to go from the paper (which I can't access), and not the video which originally confused me. – Pureferret Aug 20 '13 at 22:00
• – user4552 Aug 20 '13 at 22:05

What actually changes at relativistic speeds is the dynamical law that relates momentum and energy depend with the velocity (which was already written). Let me put it this way: trying to ascribe the modification of the dynamical law to a changing mass is the same as trying to explain non-Euclidean geometry by redefining $\pi$!