Plenum

Plenum may refer to:

See also

Luminiferous aether

In the late 19th century, luminiferous aether, aether or ether, meaning light-bearing aether, was the postulated medium for the propagation of light. It was invoked to explain the ability of the apparently wave-based light to propagate through empty space, something that waves should not be able to do. The assumption of a spatial plenum of luminiferous aether, rather than a spatial vacuum, provided the theoretical medium that was required by wave theories of light.

The concept was the topic of considerable debate throughout its history, as it required the existence of an invisible and infinite material with no interaction with physical objects. As the nature of light was explored, especially in the 19th century, the physical qualities required of the aether became increasingly contradictory. By the late 1800s, the existence of the aether was being questioned, although there was no physical theory to replace it.

The negative outcome of the Michelson–Morley experiment suggested that the aether was non-existent. This led to considerable theoretical work to explain the propagation of light without an aether. A major breakthrough was the theory of relativity, which could explain why the the experiment failed to see aether, but was more broadly interpreted to suggest that it wasn't needed. The Michelson-Morley experiment, along with the blackbody radiator and photoelectric effect, was a key experiment in the development of modern physics, which includes both relativity and quantum theory, the latter of which explains the wave-like nature of light.

Plenary session

A plenary session (with a plenary speech or plenary talk) is derived from the Latin root plenarius meaning "full" or "absolute". It usually refers to a session in a conference which is open to all (or a large number) of attendant speakers, who may each contribute prepared or ad-hoc material. Plenary sessions are typically scheduled both near the start of a conference, and in the latter half, but not typically at the final hour, due to many attendees leaving before the last day. Various prominent speakers often give opening plenary speeches, at the start of a conference, or closing plenary speeches, in the final plenary session. During those sessions, typically all other activities are suspended, or exhibit halls closed, to allow everyone to attend the plenary talks or sessions.

These sessions may contain a broad range of content from keynote speeches to panel discussions and are not necessarily related to a specific style of delivery.

Examples of usage