What is Dark Energy?

There is a mysterious repulsive energy that is pushing our universe apart at an accelerating rate. What is this "Dark Energy"? How did we come to find out about it? How does it work and what does it mean for the future of our universe? All of these questions and more are discussed in this video of Turtles All the Way Down.
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***** CONTENTS ************
0:00 Introduction
0:35 Einstein's Blunder?
2:30 Static or Changing Universe?
3:28 Distances to Galaxies
4:02 Speeds of Galaxies
5:03 Expansion of the Universe
8:03 Removal of the Cosmological Constant
8:57 An accelerating Universe
11:10 Resurrection of the Cosmological Constant
11:45 THIS is Dark Energy
14:11 The Future of our Universe
14:40 Heat Death
15:03 Dark Energy NOT Dark Matter
15:20 Conclusion
********************
CREDITS:
BG Music:
Einstein's quotes: www.pnas.org/doi/full/10.1073..., www.ncbi.nlm.nih.gov/pmc/arti...
Hubble's paper/data: www.pnas.org/doi/10.1073/pnas...
Perlmutter et al Paper: iopscience.iop.org/article/10...
Riess et al paper: iopscience.iop.org/article/10...

[@user-nn1cl8ow7b]

Dear youtuber, congratulations on your subject and the handling of it. If I may suggest something though: please ask yourself why 'music' (if some notes may be called so) is needed in the background. In my opinion 'music behind a voice' is a matter of fashion and - if I may say so - quite a silly one. People who need music in orde to be attracted to listen to the explanation of an interesting and serious subject do not exist. Those who really need a backgrond music are in my view empty-headed (they need the music to fill in a void) and those people are by definition not interested in a serious subject. I found the background 'music' very disconcerting in your - otherwise splendid - video. So, my sincere compliments, but a strong suggestion to let music be music and voice be voice.

[@TurtlesWayDown]

Thanks for the input! However, I find that music in the background adds flavor to the video in the same way that the unneeded visuals do. Without either, the video would lack color. In the same way that many documentaries contain background music and some people seem to focus more with gentle music playing I've found that adding music to these videos gives an added dimension that the videos would otherwise lack. But I would in no way call the curious viewers who enjoy this music "empty headed". I have heard from many intelligent viewers who actually enjoy it. However, I do appreciate your input. Thanks

[@benheald6881]

@@TurtlesWayDownI agree. The video is equally a showing of scientific passion as it is of artistic expression.

[@shawns0762]

There is only one reason to postulate dark energy, to explain the exponential expansion rate of the universe. The expansion was discovered in 1929. It was discovered that the expansion was accelerating in 1998, this is when the concept of dark energy became mainstream. If something accelerates at a constant rate it will get faster and faster. If a ship travels at a constant 1g acceleration rate it would achieve about 95% light speed in 1 year. Electricity is drawn towards potential and the universe as a whole behaves the same way. Electricity comes into our homes because the neutral circuit provides the potential. Electricity is drawn towards grounding rods for the same reason. Physicists in the last century did not postulate dark energy because they understood that the expansion is a fundamental property of the universe. The fact that the expansion is accelerating does not invalidate their reasoning, it's what the known laws of physics would predict. All studies to find dark energy have been fruitless because it doesn't exist. To say there is dark energy is to say there is 5 fundamental forces, there is 4.

[@oldmandoinghighkicksonlyin1368]

Nice. A science communicator that is not an AI narrator. That is most welcome!

[@TurtlesWayDown]

LOL, "It can only be attributable to human error." - HAL9000