The Universe is big...Really?

[StevOz]

Then again there is more than just spin outside of Earth...

 

[Isaac Sauvage]

So when they say all of the stars in the sky are moving away from us quicker and quicker, and these stars will no longer be able to be seen in future, how does that jive with Andromeda moving closer and closer, and eventually colliding with us?
So everything except Andromeda is moving faster and faster away from us?
That does not make sense.

Imagine your class goes on a school trip to a balloon factory.

At a balloon factory, before the latex rubber sheets are processed in to balloons, they can be quite large, like the size of tarps. Now let's say for fun purposes, one of the tarps is cut in to large circle, and your class is permitted to play around with it in the visitors' area. Now the science teacher proposes an experiment:

Two kids stand in the middle of the sheet, and the rest of the class spreads around the perimeter and grabs hold of the edges with both hands. The teacher says "now pull everyone!" and the rubber expands, slowly getting larger and larger.

Then the teacher says "okay, you two in the middle, step slowly towards each other," and in a couple moments, they're close enough to touch. How was such a thing possible?

It was possible because the speed of the two objects in the middle moving towards each other was greater than the speed in which the sheet was expanding.


Remember, if everything's indeed expanding in the universe, then the same is true on Earth. And yet, I'm still able to reach over to the table and pick up my glass of iced tea without it flying away from me. That's because the universe is expanding in a relative way.

Not unlike how the Earth is spinning around its axis at 1,000mph, while rotating around the sun at 66,000mph, while the Solar system is rotating around Sagittarius A* (the massive black hole at the center of the galaxy) at a speed of 448,000mph, while the Milky Way is also flying through space. We just don't notice it.

Or another way to look at it is that gravity can be a game-changer in these situations. For example, the Earth as a whole is held together by gravity despite all the spinning & flying, and despite the universe expanding. That's also true up to the local cluster of galaxies... up to a point. Eventually, far in the future, that may be less true, when the force of expansion is greater than gravity's ability to knit things together. Indeed, the universe may ultimately be headed towards a Big Rip.

AFAIK the very strongest natural forces (indeed, much stronger than gravity) that can resist the expansion are atomic forces (strong & weak force), followed by molecular bonds. Those will pretty much be the last things to go in a Big Rip scenario.

Getting back to the point-- not unlike how our lives go on Earth, the Milky Way and Andromeda don't 'notice' that the universe is expanding because their speed and mutual attraction is far greater at the moment. As for what the galactic merger will look like? It should be something like this:

Thanks for coming to my very amateurish TED talk. :D

 

[Isaac Sauvage]

Then again there is more than just spin outside of Earth...

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I guess I missed that at the time. Nice!

I don't understand much about superclusters, but one thing I do find interesting is that they structure themselves so vastly differently than almost everything else smaller than them.

For example, fundamental units from atoms right up to galaxies all arrange themselves as a heavy spinning mass in the center (edit: well maybe not atoms), with orbiting satellite material around that central mass.

Yet superclusters seem to operate in an almost completely different way. I guess it's like watching gravity's last little effect, just before it loses all influence.

 

[StevOz]

Though how about those black holes, at the centre of every galaxy, the bigger the galaxy the bigger the hole, though that's not all...

A speeding black hole is birthing baby stars across light years

Who says all black holes are space vacuum cleaners?

mashable.com

 

[xenonph]

Easily explained.
That black hole just ate too much, and has a bad case of gas.

 

[centaur]

Some years ago I got Universe Sandbox. It sounded like pretty cool game on paper but in reality it doesn't even touch the ankle of pinball. The first thing I did was to go to Jupiter and fatten it. I kind of enjoyed how it made the rest of the planets' trajectories wobble more and more, eating this and that from time to time. But at one point the whole thing glitched out ... or so I thought... in fact Jupiter transformed into a black hole?! Can't say if it's lazy physics or just a boring program. Deleted it and got a refund.

 

[StevOz]

That black hole just ate too much, and has a bad case of gas.

Nah, at 4 million mph?

Though I did an experiment in the kitchen on this I used a full jar of jalapeños in my last curry, and it did feel like giving birth to stars the next day, though I guess I wasn't travelling fast enough?

 

[xenonph]

4 million MPH is pretty incredible!

 

[Isaac Sauvage]

Some years ago I got Universe Sandbox. It sounded like pretty cool game on paper but in reality it doesn't even touch the ankle of pinball. The first thing I did was to go to Jupiter and fatten it. I kind of enjoyed how it made the rest of the planets' trajectories wobble more and more, eating this and that from time to time. But at one point the whole thing glitched out ... or so I thought... in fact Jupiter transformed into a black hole?! Can't say if it's lazy physics or just a boring program. Deleted it and got a refund.

I used to have the notion that if Jupiter had been somewhat larger, it might have turned in to a star, even if only a small one. From what some astronomers on Reddit have said though, it's many orders of magnitude too small.

I think you were right to get a refund!

 

[centaur]

I used to have the notion that if Jupiter had been somewhat larger, it might have turned in to a star, even if only a small one.

So... a planet? Maybe you wanted to write "a planet like our Sun"? Otherwise I must object to your use of the word "star". Stars obviously belong to the sphere of fixed STARS and have nothing to do with planets like our beloved Sun or Moon.

 

[Isaac Sauvage]

So... a planet? Maybe you wanted to write "a planet like our Sun"? Otherwise I must object to your use of the word "star". Stars obviously belong to the sphere of fixed STARS and have nothing to do with planets like our beloved Sun or Moon.

Roughly speaking, when there's enough stellar gas collected in a mass, the gas will collapse and begin fusion, forming a "star."

Jupiter is a gas giant similar in H/He composition to the cloud of gas that became the sun, but it didn't have nearly enough mass to go in to the fusion cycle. From a quick search, it looks like it would have had to be about a dozen times more massive to have become a brown dwarf star, and over 6x that amount to have become a small star with typical stellar output.

So you may sometimes see Jupiter called "a failed star," and that references the fact that it didn't have enough gas content to become one.

Planets, stars, black holes, moons, comets, asteroids, and even all life on Earth... their atoms are all built from early cosmic dust, ultimately.

 

[Isaac Sauvage]

And here's the official video of that, yeah?

 

[centaur]

Roughly speaking, when there's enough stellar gas collected in a mass, the gas will collapse and begin fusion, forming a "star."

Maybe the real Sun/suns were the friends we made along the way...

 

[StevOz]

And here's the official video of that, yeah?

Actually, I think it goes more like this...