"Dark matter" is a blanket term for inferred matter that is undetected but must exist in order for gravity at very large scales to make any sense at all.
Based on inference, 27 percent of the universe is generally acknowledged to be dark matter, even though it is not visible and eludes direct detection and measurement. Whatever dark energy might turn out to be gets a number of about 68 percent of the universe. The rest of the universe, what we can detect and feel, is what we know to be matter.
Hang on? Oh, there you are… ESA, Author provided
By Monica Grady, The Open University
Phew, what a day it was yesterday. Ended up having a quiet drink at the hotel. Last drink of the day – a nice cup of tea!
Most of the world that has access to the Internet knows two things about the Rosetta mission - it landed on a comet and a European engineer wore an ugly shirt that offended a lot of American women on Twitter.
The least interesting news is that the ESA now knows that if women can't wear bathing suits to represent them on television, then male project scientists cannot wear bowling shirts and shorts. The important news, however, is that mankind has shown we can go on a 10 year, 4 billion mile journey through the solar system and land on a rock the size of Cork City, Ireland.
Hey, does anyone want this comet?
For the first time, mankind has successfully landed on a comet - a journey over 10 years in the making.
After a seven-hour final descent, Rosetta’s Philae probe signaled from the surface of Comet 67P/Churyumov–Gerasimenko and the message arrived on Earth at 16:03 GMT, completing the longest part of a 4 billion mile journey through the solar system.
The landing site, named Agilkia and located on the head of the bizarre double-lobed object, was chosen based on images and data collected at distances of 30–100 km from the comet. Those first images soon revealed the comet as a world littered with boulders, towering cliffs and daunting precipices and pits, with jets of gas and dust streaming from the surface.
Rosetta: Firing harpoons in space. ESA/ATG medialab
By Alan Fitzsimmons, Queen's University Belfast
The first attempted landing on the surface of a comet is a huge landmark in the history of space exploration that will not only uncover further details about comets but could unlock further clues about the origins of our solar system and the development of life on Earth.