To check out the physics courses that I mentioned (many of which are free!) and to support this channel, go to https://brilliant.org/Sabine/ and create your Brilliant account. The first 200 will get 20% off the annual premium subscription. In this video I explain that quantum mechanics is not merely a theory for short distances, as it is often portrayed. Quantum mechanics applies to all objects, regardless of size. Indeed, quantum effects are necessary to explain many rather mundane observations: the sun shines, atoms are stable, laser light is strongly focused and coherent. Correction: The map at 5 mins 13 secs does not show the islands of Tenerife and La Palma but, mistakenly, the islands of Tenerife and Gran Canaria (the captial of which is Las Palmas). Lots of palms there, I figure. ht Jose de la Puente for pointing out. Note: The animation at 1 mins 31 secs does not show what really happens if an electron hits an atomic nucleus. It merely illustrates "this is not how atoms work". If an electron hits an atomic nucleus, there constituents of the nucleus most definitely do not fly off in all directions! The paper I mention about superpositions of large molecules is this: https://aip.scitation.org/doi/full/10.1063/1.2424439 And the one about Bose Einstein Condensates is this https://www.nature.com/articles/s41567-019-0663-9 The previous videos in the series "Understanding Quantum Mechanics" are: #1 It's not about discreteness https://www.youtube.com/watch?v=XJSfgE9LUJw #2 Superpositions and Entanglement https://www.youtube.com/watch?v=j6Mw3_tOcNI #3 Non-locality https://www.youtube.com/watch?v=XL9wWeEmQvo #4 The Bra-Ket notation: https://www.youtube.com/watch?v=ctXDXABJRtg #5 Decoherence https://www.youtube.com/watch?v=igsuIuI_HAQ Content of this video: 0:00 What and Why 0:36 Nuclear Fusion in the Sun 0:55 Stability of Atoms and Solar System 3:50 Lasers 4:50 Entanglement on the Canary Islands 6:15 Big Molecules and Bose Einstein Condensates 7:14 Brilliant Sponsor Message