News Physics New limit placed on physics constant Analysis could help scientists determine whether quantum mechanics parameter varies with time Share this:FacebookTwitterPocketRedditPrint By Gabriel Popkin October 15, 2013 at 4:12 pm This article is only available to Science News subscribers. Subscribers, enter your e-mail address to access our archives. Client key* E-mail* Log in Not a subscriber? Science News is a nonprofit. Support us by subscribing now. Subscribe