Geodesics and Relativity

Why does the Moon orbit the Earth? What's the connection between a funnel and a black hole? What is a metric? All these answers in 11 minutes!

0:00 - Introduction
0:45 - The metric
3:54 - Geodesics
6:29 - Spacetime
10:13 - Conclusion

This video is narrated by Octave Masson.
And if you liked this video, you can share it on social networks !

Alessandro Roussel,

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To learn more :

[StevenG]

I’ve found myself sharing your videos with physicists of all levels of expertise—from beginning students to long-time professors. Your videos are not only a gift to students, but they are also an inspiration to anyone interested in physics pedagogy. I hope you enjoy making these videos as much as we enjoy watching them.

[gama]

Yay! I'm biologist and im learning distance metrics, including geodesics as a part of a proyect that involves tensors and n-dimensional spaces of proteins. With this video I get a clear view about geodesics

[Badmanxl]

This is what the internet and YouTube should be used for not the dumb stuff of social media.

[WilliamDye-willdye]

I love that you explain the concepts clearly enough for most everyone, but also include the equations for those who wish to go further. Thank you for being "au-dessus de ma tête, mais pas hors de portée" (above my head, but not out of reach).

[Maxi-qreg]

It is insane how well presented your videos are. Please keep this up! :)

[SAUCEKING-zp]

Favorite science channel on the site honestly

[justind]

You're the Geodesic to my Relativity, ScienceClic <3 Your videos are superb.

[dutonic]

I just watched your entire general relatively series and have never had such a strong understanding of the material. You also addressed how a 5th dimension is not needed to address gravity in your better general relativity model, which had been nagging my understanding of that concept for a long time. I have so far yet to go but feel invigorated to press forward thanks to you. I noticed you've been using the same song on every video for the last several years. I'd be absolutely willing to compose a custom soundtrack for your videos completely free as thanks for the work you do. Feel free to reach out any time :)

[dutonic]

I just found your channel and I'm blown away by the quality. Videos like yours inspire me to continue grinding through the hard parts of university to one day be able to wholly understand the beauty of the cosmos.

[ckara]

This is the best Physics channel by far. The concepts are explained in the right amount of detail

[technologystrong]

The giant connection with relativity at 6:14 blew my mind. These videos help me so much understanding general relativity because of it's excellent visual and audio information. Excellent channel!

[timgabby]

Showing that following the same latitude is not a geodesic is more clear near the poles. Great video.

[NikHem]

This channel knows the geodesic to my heart

[thenephilim]

I just LOVE your visualizations... They are clarifying so many things a textbook or a simple PowerPoint presentation can't really answer. Thanks for all the effort! Your channel is one of my favorite physics channels.

[IntegralMoon]

This video is simply stunning! I'm amazed at how well you've condensed these equations and how intuitively you've explained them. I hope your channel absolutely explodes in popularity. Great job :D

[michaelharipersad]

Alot of this knowledge I've already viewed in other videos, but the clear step by step breakdown is a joy to watch/listen to. Great content!

[mohammaddashtpeyma]

By far, ScienceClic is the most precise on the subjects of physics in the internet. Keep up the good work.

[dialectphilosophy]

This is another in a series of amazing, sophisticated, elegant, accolade-deserving videos that ought to receive recognition beyond just the YouTube platform. That said, we were determined to find something to be nitpicky about, so here goes 😂 :

“…when an apple falls off a tree from a previously motionless state….”

**technically speaking** the apple hanging from the tree was subject to a force and therefore already in motion.

“…it is because the curvature of spacetime bends the geodesics between time and space…”

Well again, **technically** the apple wasn’t on a geodesic to begin with; being held up by the tree meant it was subject to geodesic deviation. There isn’t also really spacetime curvature in this small of a region. The ground is just an accelerated observer; the geodesic paths on his/her spacetime diagram appear to be bending as a consequence of that acceleration. (For there to be spacetime curvature in the vicinity, the distance between geodesics on the spacetime diagram would have to be changing — but even the down-diving lines maintain regular spacing.) However that statement does apply in the global sense, since without curved spacetime there wouldn’t be the gravitational force there to begin with.

It’s very encouraging and inspiring to see videos of this quality and caliber out there — please keep it up!

[flochforster]

Incredibly well explained and the visuals make it crystal clear. Thank you very much.

[beabzk]

I was literally arguing with my friends about the path a plane takes, yesterday. Great video and thanks! Now I can refer them here.