Why would a thick glass candy dish suddenly break in two with no one near it?
Glass is full of microscopic cracks. Uneven changes in temperature put tiny stresses on the glass, which lengthens the cracks. Glass is cracking continuously and very sensitive microphones can hear it. Some glass is made deliberately prestressed, to shatter into granules on impact rather than leave sharp edges, like car windscreens. Some glass may be made extra stressed due to flaws in manufacture. If a glass dish has been exposed to excessive changes in temperature, or has been manufactured with a stress flaw, then finally even a tiny change in temperature may be enough to lengthen the cracks until they start running into each other, which in a heavy glass dish will rapidly increases the stress until it falls into pieces.
