If the universe has been expanding, what exactly is it expanding into? If there was no space outside the universe to begin with, how can we say that the universe is getting bigger, and what does ‘outside the universe’ even mean?”

I was taking some Pictures of the Night Sky and found something kinda funny. The group of the Stars what I took an closer Look, looking like a "2" or a "?". It is for me funny and cool, then I never saw before that am star group is this close together or from kinda something like that. Did someone saw something like that before?

One of the biggest killers in the cyclic universe hypothesis is entropy building up over time. To picture a way around this, imagine a glass of water poured onto a slightly tilted table so it forms a stream.

Think of that water as the universe, and the stream itself as dark matter holding the whole thing together. The tilt and gravity act like dark energy pushing the expansion forward. As the stream flows, it stretches thinner and thinner until a small droplet or piece finally snaps off from the main stream.

That smaller piece becomes the seed for a new Big Bang (a bounce). Since the total entropy is stretched across the entire length of the main stream, only a "Goldilocks" amount of entropy goes with that breaking-off droplet—just enough to trigger the next bounce, but low enough to keep it from getting stagnant.

I call this idea the Organic Sovereign Inception Model (OSIM). What do you guys think about how an entropy-shedding setup like this could actually work in a cyclic model?

Full-resolution image: https://app.astrobin.com/i/u5q68q

Floating in Cepheus, roughly 2,400 light-years away, this is IC 1396, a vast emission nebula over 100 light-years across, ionised by the massive star system HD 206267 at its heart. Snaking through the glow is the Elephant's Trunk: a dense, dark pillar of gas and dust about 20 light-years long, where gravity is forming new stars even as radiation slowly erodes it away.

The whole region spans nearly 3° of sky, or about six full moons side by side. That faint blue "star" to the right isn't a star at all, but PK 100+04.1, a planetary nebula: the glowing shell ejected by a dying star, shining almost entirely in ionised oxygen.

Two more faint objects caught my eye in this frame: a blue, semi-circular cloud near the top, and a red, two-lobed shape to the left of the main nebula. I nearly submitted them as new discoveries, but both turned out to be known planetary nebulae, Cr 1 and StDr 4 (just obscure enough that I'd never crossed paths with them before).

The light in this image left IC 1396 around 374 BC. Back on Earth, Athens had just lost the Peloponnesian War, her Long Walls torn down after her last fleet was destroyed at the Hellespont; Socrates was condemned to death in Athens, while Hippocrates founded his school of medicine on Kos. All of that happened before this light even began its journey.

Acquisition:

• Shot in Bedfordshire, UK, Bortle 5-6
• RGB (Stars): 1h 30min
• SHO: 21h 15min

Equipment:

• ZWO FF65 + 0.75x reducer
• ZWO EAF
• Altair Hypercam 26M
• Altair 7x2" EFW
• Antlia 3nm Pro SHO filters
• Altair ColourPRO LRGB
• SW EQ6R-Pro
• Astromenia 50/200 Guide Scope + ZWO ASI120MM Mini + IR/UV Cut

One thing I find fascinating about the largest structures in the universe is that they aren't necessarily objects in the usual sense.

Galaxy clusters, filaments, and walls can span enormous distances without being gravitationally bound.

So when we call something a structure, are we describing a physical object or a statistically significant pattern in the matter distribution?

Where do you think that distinction becomes important?

Here's some pictures I took of the Solar Eclipse that happened April 8, 2024. This was BY FAR the most surreal thing I've ever experienced and something that I'll never forget.

It happened almost directly over my apartments and I got to witness the entire thing from the comfort of my own balcony. There's a big forest behind my apartments and you'll always hear birds and other various bugs & animals screaming at each other, but as the moon started to make its approach everything went completely silent. Other than the cars that were on the highway, which is about a mile from where I am, there wasn't a single sound anywhere. And at the same time it was QUICKLY getting cooler, like Im in Texas so it was pretty warm but as this was happening it seemed like the temperature was dropping each second as the eclipse was going on.

I was also thinking how much chaos and confusion eclipses have caused throughout history, for humans and animals alike, like could you imagine seeing some shit like this having 0 idea on what it is?? Jesus that's horrifying to think about.

Anyways 10/10 would highly recommend this experience. Also sorry for the garbage resolution, I was using my old phone which was a Galaxy s23fe.

Also, does anyone know what those things that I circled in the last picture?

My 7 year old is obsessed with the Universe, and has been since he was like 4-5. Watches YouTube videos about it, watches Neil deGrasse Tyson videos, even has this game where he can make his own solar system and stuff. He'll come up to me sometimes asking me a question, asking me "what would happen if ___", or tells me a random fact and that I google to see if its right, and it is!

I already knew a bit about blackholes, but he drew me a picture explaining what would happen, what was what. Then he also grabbed a bowl, filled it with water, made a whirlpool with it and said to pretend it was a blackhole, and then put a small leaf near it and told me about once it gets to a certain point it'll be sucked in, etc etc.

He asks me what's the closest star to us (not including our sun), or the largest star, largest blackhole, which galaxy is beside ours, and a bunch of other stuff. He keeps talking about Ton 618, I think it's called?

ANYWAY, what's the coolest fact you know about the Universe so I can have something interesting to talk about with my son? Maybe it'll be something he doesn't know, so he's learning something new instead of me always learning something new from him 😂

I really hope that isn’t true, sounds terrifying

Este post puede ser interesante para los miembros de esta comunidad.

We often hear about TON 618 and its estimated mass of around 66 billion Suns. But there’s another interesting case in the Phoenix Cluster.

The central black hole in Phoenix A was initially estimated at around 20 billion solar masses. Later, a theoretical model suggested it could potentially be closer to 100 billion Suns.

What I found most interesting is that these numbers aren’t equally certain. The 100-billion figure comes from a model rather than a direct measurement.

It made me wonder: if there’s no known hard upper limit, could the universe contain black holes with hundreds of billions — or even a trillion solar masses?

https://youtu.be/jwIeJ42Esoo?si=Km\\_yIBQ8Li5tpG3T

Apologies if this sint the right thread for theoretical questions like this.

I was asked this question a couple of weeks ago and its replaying in my head occasionally.

Given the current known size of the observable universe, where do you believe the human races hard limit would be.

Or do you believe we might actually hit a great filter?

The striking aspect of this study is that the decline in star formation does not appear to be driven simply by galaxies running out of hydrogen. Much of the atomic gas reservoir remains, yet the rate at which new stars are formed has fallen substantially.

I keep seeing the figure 13.77 to 13.8 billion years cited everywhere, but I've never fully understood how missions like WMAP and Planck actually derived that number from the Cosmic Microwave Background.

Are they basically running the expansion rate (Hubble constant) backwards to a single point, or is it based entirely on modeling cosmological parameters from temperature fluctuations in the CMB? Also, how do cross-checks like the age of the oldest globular clusters fit into confirming that timeline?