Physics : Dark Matter, The Sun, Other Stars, And Galaxies

1462 Words Jan 20th, 2015 6 Pages
The visible universe- including Earth, the sun, other stars, and galaxies is made of protons, neutrons, and electrons bundled together into atoms (National Geographic, 2012). Astronomers use the term ‘baryonic’ to refer to all objects made of normal atomic matter, essentially ignoring the presence of electrons (Swinburne University, 2015). Baryons interact with each other through gravity, nuclear forces and the electrostatic force. These interactions are what allow baryonic matter (such as stars) to emit light (Grocutt, 2012). One of the most surprising discoveries of the 20th century was this ordinary, or baryonic, matter makes up less than 5 percent of mass of the universe. The rest of the universe appears to be made of a mysterious, invisible substance called dark matter (25 percent) and a force that repels gravity known as dark energy (70 percent) (National Geographic, 2012).
Dark Matter: The Source of Extra Gravity
Unlike normal matter, dark matter does not interact with the electromagnetic force. It does not interact with baryonic matter and it is completely invisible to light and other forms of electromagnetic radiation (National Geographic, 2012). This means it does not absorb reflect or emit light, making it extremely hard to detect. Scientists have not yet observed dark matter directly. Scientists can estimate where dark matter is based on its gravitational effects on surrounding matter using a technique called gravitational lensing; observing the way dark matter’s…

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