Support MinutePhysics on Patreon: www.patreon.com/minutephysics Aatish Bhatia helped write this video! A big thanks for his help! Here's his blog: www.empiricalzeal.com The universe is expanding – this we know from looking at red shifts of distant galaxies – but the acceleration of the universe's expansion is harder to measure. It requires measuring the change of recession velocity over time, and it's done by comparing Type Ia supernovas as standard candles at different distances, which is how we know the universe is accelerating! Thanks to everyone who supports MinutePhysics on Patreon! Link to Patreon supporters here: www.minutephysics.com/supporters.html REFERENCES Type Ia supernovae hyperphysics.phy-astr.gsu.edu/hbase/Astro/snovcn.html en.wikipedia.org/wiki/Type_Ia_supernova Luminosity Distance en.wikipedia.org/wiki/Luminosity_distance Hubble diagram for type Ia supernovas (relatively close to earth): www.pnas.org/content/101/1/8/F3.expansion www.astronomy.ohio-state.edu/~thompson/1101/lecture_fate_of_universe.html Straightforward references: Ryan Foley talking about WFIRST & Dark Energy youtu.be/BhOAwXYKdmw?t=23m Dark Energy FAQ: www.preposterousuniverse.com/blog/2011/10/04/dark-energy-faq/ Why does dark energy make the universe accelerate? www.preposterousuniverse.com/blog/2013/11/16/why-does-dark-energy-make-the-universe-accelerate/ David Spergel on dark matter & WFIRST tvr2c.com/2016/06/01/53116-show-feat-professor-david-spergel-on-his-research-spanning-astrophysical-scales/ Slightly-technical references: Permlutter article (old article but quite well explained & goes into future directions near the end) supernova.lbl.gov/PDFs/PhysicsTodayArticle.pdf Technical references: Mukhanov’s Physical Cosmology www.astro.caltech.edu/~george/ay21/readings/Mukhanov_PhysFoundCosm.pdf Nobel Prize Summary www.nobelprize.org/nobel_prizes/physics/laureates/2011/advanced-physicsprize2011.pdf Cosmological redshift en.wikipedia.org/wiki/Redshift#Expansion_of_space MinutePhysics is on Google+ - bit.ly/qzEwc6 And facebook - facebook.com/minutephysics And twitter - @minutephysics Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute! Created by Henry Reich

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