How Fast Is It - 04 - General Relativity I - Geometry (1080p)

In this segment of the “How Fast Is It” video book, we cover the geometry of general relativity. We start with the Elevator Thought Experiment, and show how it represents a gravitational field and how it predicts the bending of light. This sets the stage for the Equivalence Principle. This leads to the reconciliation of Newton’s two definitions for mass. Which, in turn, leads to the idea that the existence of a mass bends space. To understand the bending of space, we cover the basics of Euclidian and non-Euclidian Riemann geometry. We include spherical and hyperbolic geometries along with the nature of their respective geodesics. We actually measure geodesic deviation above the Earth. For a fuller understanding, we cover the definition of metrics and curvature in terms of tensors. With the general Riemannian Curvature Tensor in hand, we find the subsets that reflect the behavior of space within a volume. We then cover how Einstein mapped this geometry to space-time to produce the Einstein Curvature Tensor. And finally, we describe the Energy-Momentum tensor that identifies the nature of a volume of matter-energy, which is the source of the space-time curvature. Setting these equal to each other with an appropriate conversion factor gives us Einstein’s general relativity field equations.

[philenealvarado]

Why so much criticism here? This man is highly intelligent; be better if you just start your own science channel.

[DickHoskins]

Excellent video. There is a lot of subtlety here that is nearly impossible if not totally impossible to convey to lay people. It took Einstein 10 years to develop all this stuff and it took until the present day to have a substantial fraction of professionals to understand it. You have done a great job. Thanks for the effort.

[mamm]

Such a great presentation... Simple and powerful

[michieldrost]

That Dr. Who reference was great. Thanks

[oddarneroll]

haha, awesome video. Please dont take this the wrong way, i use it as a sleeping aid every night now. I tried listening to some mindfulness crap, but i got so bored by all the bs. This is interesting and extremely relaxing at the same time.

[lidarman]

One of the best explanation of GR I have ever heard.

[Lanka]

thanks..you are the best physics teacher

[frankyjayhay]

The therapeutic music is a good idea, like what some brave people calm themselves with during a major operation instead of having a general anaesthetic.

[eyesyc]

Fabulously concise. Beautifully narrated, illustrated, and scored-once again Mr Butler

[flugschulerfluglehrer]

Congrats. I've seen and read a lot of popular science on GR. This is by far the clearest explanation I've seen so far.

[simonmcgrath]

How is it possible for anyone to thumbs down this? I suppose it's all relative!!

[heydj]

23:20 level of respect for you reaches beyond expectations, star wars is life, balance is everything.

[learnerlearns]

Best explanation of Ricci and Einstein tensors I've seen!

[ernieengineer]

Awesome explanation. Thanks for posting.
Thanks for posting.
Love your narration too.

[nottees]

A wonderful series, I am your student! And thank you for starting to include the info-window music credits, as well. The music is a subtle but stimulating encouragement to the stretching minds like my own, I'd say.

[ritchiefrostwood]

Sitting here with my math books, doing my best to follow every step. Going well so far.

[ThomasJr]

Holy moly, you do understand all of this. Tbh, I try to understand just the more tangible parts, prior to tensors, such as SR. Thats why it puzzles me how you can be so smart but kinda dyslexic.

[potawatomi]

You produce excellent videos which are well narrated and expertly explained.

[antiNuetron]

Very interesting. Now that we have YouTube, college is almost useless.

[inthefade]

I am going to have to rewatch this some day. I got a little lost at the explanation of what tensors are. Really great videos though.