Date post: | 01-Apr-2015 |
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What is dark matter?
• 96% of the universe is missing• In fact, all of the stuff we can
detect in the universe:– All of the matter– All of the energy – Only seems to account for
4% of the total size of the universe
• Scientists have been measuring the movements of millions of stars and galaxies
• And the way light bends on its way to us from distant galaxies billions of light years away
• The results say the same thing again and again
• There is a lot more out there than we see
• The straight answer: we don’t know
• Whatever it is, it doesn’t emit or absorb light like normal matter
• So we’re call it dark matter• We think it accounts for 23% of
all the matter in the universe
Pie of matter and energy[NASA]
• It’s invisible, but its gravity gives it away by bending passing light, like a lens
• The cluster of galaxies in the front of this image, called Abell 1698, is bending the light from galaxies behind, making the curved streaks
• Abell 1698 must contain dark matter to bend the light this much
Galaxy Cluster[NASA]
• This map shows dark matter has been around since as far back as we see, around 13.4 billion years billion years
• It’s scattered all through the universe, like an invisible skeleton holding normal matter in the shapes we see
Dark matter map[NASA]
• Invisible astronomical objects called Massive Compact Halo Objects - MACHOS - may explain some of it
• MACHOS are things like neutron stars and black holes, which have huge masses but give out no light
• But most dark matter is probably made from something completely mysterious
[CERN]
• Dark matter might also be made of a completely undiscovered kind of subatomic particle
• These particles are called supersymmetric particles, or sparticles for short
• Some are weakly interacting massive particles: WIMPS
• Top of the list of suspected dark matter WIMPS are neutralinos
• Making sparticles, like neutralinos, needs more powerful particle accelerators than ever before
• The LHC will be able to collide particles with enough energy to make them
• We won’t see them directly, but the huge detectors at the LHC may pick up hints of their existence
[CERN]
• The biggest machine on Earth• To glimpse a shadow world of
particles• That most of the matter in the
universe is made from…
[CERN]