Gravity may have chased light in the early universe

It’s supposed to be the most fundamental constant in physics, but the speed of light may not always have been the same. This twist on a controversial idea could overturn our standard cosmological wisdom.
In 1998, Joao Magueijo at Imperial College London, proposed that the speed of light might vary, to solve what cosmologists call the horizon problem. This says that the universe reached a uniform temperature long before heat-carrying photons, which travel at the speed of light, had time to reach all corners of the universe.
The standard way to explain this conundrum is an idea called inflation, which suggests that the universe went through a short period of rapid expansion early on – so the temperature evented out when the cosmos was smaller, then it suddenly grew. But we don’t know why inflation started, or stopped. So Magueijo has been looking for alternatives.

Now, in a paper to be published 28 November in Physical Review, he and Niayesh Afshordi at the Perimeter Institute in Canada have laid out a new version of the idea – and this one is testable. They suggest that in the early universe, light and gravity propagated at different speeds.
If photons moved faster than gravity just after the big bang, that would have let them get far enough for the universe to reach an equilibrium temperature much more quickly, the team say.

China’s space station now has insects, weeds and rice on board

INSECTS, weeds and rice are growing on the Chinese space station, and could pave the way for future food sources for astronauts.
China’s Tiangong-2 space station launched on 15 September, and two astronauts have been living there since mid-October. The station includes experiments growing thale cress – an edible weed – and rice in microgravity. Chinese news sources are reporting that the cress has flowered and some of the rice plants are 10 centimetres tall.

The station also hosts an experiment designed by Hong Kong middle school students involving six silkworms, which previous studies have suggested could be protein sources for long space journeys. Five of the silkworms have spun cocoons.
When the astronauts return to Earth, which is expected around 18 November, they will bring cress samples back with them. The rice experiment will continue for several months.

This is not the first time we’ve grown food in space – astronauts on the International Space Station ate lettuce grown in orbit. But the Tiangong-2 experiment lets scientists on Earth control the incubator environment remotely.