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Asked by HabztheG to Josh, Chris, Rebecca, Rob, Susan on 16 Jun 2015. This question was also asked by shakil fahad, XX__JoJo__XX ( Jorja Howard ), estherisboss, charliebam, Jimmy (Jemima).
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Susan Cartwright answered on 16 Jun 2015:
About 70% of it is dark energy. We have no idea what dark energy is at all – we only know what it does (it acts against gravity, speeding up the expansion of the universe).
About 26% is dark matter. We don’t know what dark matter is either, although we have some plausible ideas. We do know something about its properties: it is not electrically charged, it is stable (or at least has a lifetime much longer than the age of the universe), and it moves slowly enough to be gravitationally captured by galaxies. No particle in the Standard Model has these properties, so it is something new and as yet undiscovered here on Earth.
The remaining 4% is ordinary atomic matter. Most of this is in the form of hydrogen and helium gas in between the stars (and in between the galaxies) – only about a tenth of it has condensed into stars and planets.
So, what you see in the night sky is about 0.4% of the energy content of the universe! (And 96% of it is as yet not understood. Plenty for young physicists to work on in future.)
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Josh Meyers answered on 16 Jun 2015:
Hi Habz,
I reckon Susan has answered this much more than I can!
If you’re interested in this, then physics is the one for you. I’m a chemist and more interested in applying atomic matter to understand our world and create new materials and medicines.
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