He solved these problems by invoking radiation pressure
and the laws of thermal radiation.
Christine Demore, a physicist at the University of Dundee in Scotland, and colleagues set out to reverse the direction of that radiation pressure
, so that an object would get pulled rather than pushed.
Because it may be tumbling along under atmospheric drag instead of solar radiation pressure
, some purists insist it isn't a true solar sail.
Recent advances in technology mean that spacecraft propelled by solar sails, which use radiation pressure
from photons emitted by the Sun, or electric sails, which harness the momentum of the solar wind, can now be envisaged for mid-term missions.
Until now, scientists weren't sure whether magnetic fields, radiation pressure
, or heat alter the orbit and trigger that fall.
At the macroscopic scale, the interaction is mediated by the radiation pressure
and is raising considerable interest as a way to excite and control mechanical oscillators, allowing, for instance, the refrigeration of a macroscopic object near the quantum limit.
This solar radiation pressure
would have a negligible effect on normal-sized spacecraft but is significant at the millimetre scale.
The L-AII update has incorporated improvements in a variety of scientific knowledge areas, including: numerical standards, geopotential, monitor station site displacement, tidal variations in the earth's rotation, tropospheric delays, and satellite solar radiation pressure
With atoms no longer in light's grip, radiation pressure
stops, and the biggest sound waves quickly die.
This fine dust is usually removed through collisions among the particles, radiation pressure
from the star's light and other forces," explained Debes.
The tug-of-war between gravity and radiation pressure
generated acoustic oscillations, which are regions of higher and lower pressure that have the same form as sound waves.
The research, by Lawrence Livermore National Laboratory, University of California, Santa Cruz and UC Berkeley, has shown how a massive star can grow despite outward-flowing radiation pressure
that exceeds the gravitational force pulling material inward.