
Show HN: An Interactive Audio Lesson About the Shape of the Universe - Uehreka
http://chrisuehlinger.com/expansion-lesson
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flexie
Very nice! I really like this kind of teaching :-)

Nitpick: If the model universe is a square that is 100 meters across as said
in one of the first lessons, it's area is not 100m2 as stated in one of the
next lessons.

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Uehreka
Somehow, I just knew a dumb mistake like that was going to make it in. Thanks
for the tipoff, I'll record a new voiceover this weekend and edit those bits.

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motleyhatch
That was fascinating, and very well done. It's not often you see somebody
actually creating interactive scripts (and miniature models) of things like
particle collisions for a presentation. The availability and the quality of
the external links is also highly appreciated (even though sending me to
Vsauce might cost me another evening). A couple of suggestions for
improvement:

An estimate for how long the lesson will take (on average), best stated up
front.

An indicator for where we are in the presentation (like "slide 5 of 18").

A way to pause the audio in the middle of a slide (I just saw you already
addressed this one).

On the "Corrections" slide, you mention a fascinating PBS documentary. It
would be nice to get a link to that, too (if available).

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steinsgate
loved it! just one question : when the universe expanded, why did the size of
the spheres, the rocket and the asteroid remain constant? shouldn't they
expand too?

~~~
Uehreka
So this has to do with something called Dark Energy; I may dedicate a whole
lesson to it. On small scales (small meaning the size of galaxies and smaller)
Dark Energy isn't strong enough to overcome gravity (or any of the other
forces that hold stuff together). However in the void of space where gravity
isn't too strong, Dark Energy runs rampant pushing things apart at high
speeds.

If I were to do the math on how much Dark Energy there was in my tiny
universe, it might actually be the case that the asteroids should've been torn
to shreds by the immense amount of Dark Energy. In fact, there used to be an
interesting doomsday theory called the Big Rip, which went something like
this: If Dark Energy got more and more powerful with time, eventually it would
overcome gravity and start pulling apart galaxies, then stars, then molecules,
atoms and subatomic particles. This scenario is no longer considered likely,
but it's still crazy to think about.

Dark Energy -
[https://en.wikipedia.org/wiki/Dark_energy](https://en.wikipedia.org/wiki/Dark_energy)

The Big Rip -
[https://en.wikipedia.org/wiki/Big_Rip](https://en.wikipedia.org/wiki/Big_Rip)

~~~
steinsgate
Are you sure that this has to do with Dark Energy? Dark Energy is an unknown
form of energy that must appear in Einstein's equation in order to make the
universe accelerate at its current rate. Are you saying that:

1\. Dark Energy only makes the space near it expand and has little to no
effect on faraway regions?

2\. Dark Energy is not present in places which has high matter density.
Therefore, space in places with high matter density do not expand at the same
rate as other regions (which contain Dark energy)?

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skadamat
Wow this is incredible! Super fun :)

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LargeCompanies
Good stuff and cool your from Baltimore & working on a reveal.js project too.

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ghubbard
Is there any way to pause?

~~~
Uehreka
Unfortunately not at the moment, although you can click the refresh button in
the lower right corner to restart a slide if you missed something or mute the
presentation audio if you need to.

I'll look into adding a pause button, I'll just need to make sure that certain
animations pause if they were synced to the audio.

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borden
oh my god the vocal fry

~~~
betenoire
Of all the time and effort that must have went into this, you are complaining
about the sound of his voice?

