Discover the Fascinating Olber's Paradox in This Cartoon Cosmology Video

[JesseC]

Cosmology isn't my thing but a friend showed me this and I thought it was great so I'll leave it here too for anyone interested:

https://www.youtube.com/watch?v=gxJ4M7tyLRE

 

[tiny-tim]

cool!

 

[marcus]

It is indeed cool!
But towards the end, where it talks about the stretching out of wavelengths (along with distances) remember that in Hubble Law expansion there is a pattern of distances increasing without anybody going anywhere as would happen in ordinary motion. So they really shouldn't call it motion without some explanation.

In modern understanding of geometry (GR is a theory of dynamic geometry) the distances between everybody can increase without anybody getting anywhere. Without the relative position of neighbors changing etc. No approach to any destination. No transmission of info. Just everybody getting farther apart.

That's not the only seemingly weird thing, the angles of a triangle can change what they add up to. Geometry can interact with matter. And geometry can just...well...expand. But GR also explains for us why in our situation under normal conditions geometry is at least very close to Euclidean. GR explains what CAUSES it to actually be very close to what we used to think it always was. What's more, GRs geometric effects have been extremely well tested. It is our currently accepted Law of Gravity and How Geometry Works.

So in Jesse's animation of why night is dark, towards the end when they say wave-lengthening is because stuff is MOOOVING away from USSS, be a little careful and don't entirely swallow that. It's an over simplification.

Geometric expansion affects both wavelengths and largescale distances between disconnected observers in the same way. (Pairs of observers both at rest relative to ancient light, not part of part of some fixed-size thing bound together by its own internal forces. Coherent things ike that don't experience Hubble Law expansion.)

 

[Faradave]

Not to worry Marcus! Having read through your posts in the balloon analogy sticky thread, when the narrator of the otherwise excellent video said "moving" I automatically substituted the word "receding".

 

[sardar]

I am always fascinated by the complexities and mysteries of the universe. The Olber's Paradox is a perfect example of this, as it challenges our understanding of the universe and the nature of light.

The paradox, named after German astronomer Heinrich Olbers, raises the question of why the night sky is dark if the universe is infinite and filled with an infinite number of stars. According to the video, if we assume that the universe is infinite and unchanging, then every line of sight should eventually end at a star, making the night sky infinitely bright.

However, we know from observation that the night sky is not infinitely bright. This paradox has puzzled scientists for centuries, and it was not until the 19th century that astronomers began to understand the concept of an expanding universe.

The video does a great job of explaining how the expansion of the universe and the finite speed of light can help solve this paradox. As light travels through the expanding universe, it becomes redshifted, meaning its wavelength increases. This results in the light becoming fainter and dimmer as it travels through space.

Additionally, the finite age of the universe also plays a role in the darkness of the night sky. The universe is estimated to be around 13.8 billion years old, meaning that light from distant stars has not had enough time to reach us yet. This creates a boundary of observable stars, known as the cosmic horizon, and beyond this boundary, the universe appears dark.

The Olber's Paradox is a perfect example of how science is constantly evolving and challenging our understanding of the universe. I highly recommend this video to anyone interested in cosmology and the mysteries of the universe. It is a great reminder that there is still so much we have yet to discover and understand about our vast and fascinating universe.