The Universe, who is fascinated by that?

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#1619166 29-Aug-2016 14:56

MikeB4:

tdgeek:

There are billions of stars inside billions of galaxies, how can all that emanate from one dot, i.e. the Big Bang Theory? Cannot comprehend that

A Nuclear explosion starts from a small spot and a chain reaction ......boom.

Good job that the Greens weren't in charge then - otherwise, no universe!

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#1619167 29-Aug-2016 15:00

The Known Universe - American Museum of Natural History

MadEngineer

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#1619177 29-Aug-2016 15:24

tdgeek:
MikeB4:

tdgeek:

There are billions of stars inside billions of galaxies, how can all that emanate from one dot, i.e. the Big Bang Theory? Cannot comprehend that

A Nuclear explosion starts from a small spot and a chain reaction ......boom.

yes, but isn't that energy? Splitting atoms, yes, maybe your right. But the volume of hard matter that exists is incomprehensible, from a teeny weeny dot. Maybe the universe was always massive, and the big crunch theory came into play, then once all that matter got so small and dense (but way bigger than a dot) it blew up and the matter expanded once again?

the lines between matter and energy get a bit blurry here.

You're not on Atlantis anymore, Duncan Idaho.

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#1619188 29-Aug-2016 15:42

MikeAqua:

Geektastic:

I always wonder, when they say that the universe is expanding, what they think it is expanding into i.e., if the universe were a balloon being inflated in a box, what is the box?

This is something I find interesting too. As I understand it we have observed objects within the universe moving further apart and from that we infer that the universe is expanding.

But we haven't/can't observe an outer limit of the universe, so there isn't really a case for saying the universe as a whole is expanding?

It also seems the universe has a general property of aggregation.

Loose matter into solar systems, solar systems into nebula, nebula into galaxies. It's like dust-bunny formation on the cosmic scale.

Even the galaxies are slowly aggregating into central black holes.

Will the black holes eventually also aggregate until there is just one big black hole, which eventually becomes unstable and explodes to start the cycle again.

The expansion and the aggregation are happening at opposite ends of the scale of distance. On the scale of clusters of galaxies and smaller, there is aggregation. On larger scales there is expansion.

Black holes become more stable as they increase in size. However, they do lose mass through the process known as Hawking Radiation. Smaller black holes lose mass at a faster rate than large ones.

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#1619190 29-Aug-2016 15:43

JWR:

But, we won't be left with just one black hole, because the expanding (and accelerating) Universe will keep that from happening.

That interests me too.

If you think about a typical explosion, acceleration of matter happens quite quickly. Initial inertia is overcome, peak velocity is reached and then air resistance starts to slow objects down again.

But the universe is a vacuum. There is no 'resistance' to overcome.

So are we seeing acceleration because the objects are still overcoming initial inertia and attractive forces.

Mike

jpoc

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#1619235 29-Aug-2016 17:38

tdgeek:

jpoc:

Geektastic:

I always wonder, when they say that the universe is expanding, what they think it is expanding into i.e., if the universe were a balloon being inflated in a box, what is the box?

Try to imagine a two dimensional universe that is on the surface of that balloon. The balloon is inflating but from the perspective of that two dimensional universe, it is not expanding into anything it is just that the universe is getting bigger.

I think what he means is if right now the universe was X big, what exists 2 feet outside that?

Yes, but think about the surface of the balloon and realize that the surface is a 2 dimensional universe. There is no 'outside' there is only the surface. The balloon can get bigger and the two dimensional universe will expand but it will not have expanded into anything. A key concept is that the surface of that balloon has no edge.

Our three dimensional space can expand in just the same way but it is not expanding in to anything it just gets bigger. In the same way, our universe has no edge.

You can start on the surface of the balloon and travel forever in the same direction and you will never find an edge. The same applies to our universe. That begs the question of whether or not you can get back to where you started in our universe by travelling in a straight line but the answer is almost certainly that you cannot. How can that be so? Go back to the balloon again. It is expanding so everything that you see is moving away from you. The farther away something is, the faster it is moving away from you. Just like in our own universe. Now imagine the point that we (from outside the balloon surface universe) would nominate as the far side of the balloon surface universe. If the expansion of the balloon universe is fast enough that the farthest point is moving away at the speed of light then a pair of travelers in that universe who departed from each other in opposite directions could never meet up again if they kept on in straight lines.

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#1619236 29-Aug-2016 17:38

Except, gravity should be providing that resistance but isn't ... Or is it (see: dark matter)

You're not on Atlantis anymore, Duncan Idaho.

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#1619241 29-Aug-2016 17:53

MikeAqua:

JWR:

But, we won't be left with just one black hole, because the expanding (and accelerating) Universe will keep that from happening.

That interests me too.

If you think about a typical explosion, acceleration of matter happens quite quickly. Initial inertia is overcome, peak velocity is reached and then air resistance starts to slow objects down again.

But the universe is a vacuum. There is no 'resistance' to overcome.

So are we seeing acceleration because the objects are still overcoming initial inertia and attractive forces.

There is no air resistance but there is gravity. That should mean that the expansion of the universe should slow down and at some point perhaps even reverse. However, the picture of the universe as expanding at an ever slowing rate has always had some troubles and a while ago, cosmologists came to understand that the universe is actually expanding at an increasing rate. Nobody knows why or what is propelling the ever accelerating expansion. We do not know what it is but we gave it a name 'Dark Energy' which makes it seem more friendly. "What is dark energy" is probably the biggest unanswered question in physics today. Lots of people are trying to answer it and whosoever comes up with an answer that can be verified by some sort of experiment is guaranteed a Nobel prize and more media coverage and fees than you can imagine.

Exciting stuff.

tdgeek

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#1619320 29-Aug-2016 20:28

jpoc:

MikeAqua:

JWR:

But, we won't be left with just one black hole, because the expanding (and accelerating) Universe will keep that from happening.

That interests me too.

If you think about a typical explosion, acceleration of matter happens quite quickly. Initial inertia is overcome, peak velocity is reached and then air resistance starts to slow objects down again.

But the universe is a vacuum. There is no 'resistance' to overcome.

So are we seeing acceleration because the objects are still overcoming initial inertia and attractive forces.

There is no air resistance but there is gravity. That should mean that the expansion of the universe should slow down and at some point perhaps even reverse. However, the picture of the universe as expanding at an ever slowing rate has always had some troubles and a while ago, cosmologists came to understand that the universe is actually expanding at an increasing rate. Nobody knows why or what is propelling the ever accelerating expansion. We do not know what it is but we gave it a name 'Dark Energy' which makes it seem more friendly. "What is dark energy" is probably the biggest unanswered question in physics today. Lots of people are trying to answer it and whosoever comes up with an answer that can be verified by some sort of experiment is guaranteed a Nobel prize and more media coverage and fees than you can imagine.

Exciting stuff.

It certainly is. As the universe expands, matter, in the form of stars and planets, etc become further apart from each other. A time will come when as stars die, the ability to produce new stars will fade, and the universe will become a very dark and very cold place. Forget what the theory was, its the opposite of the Big Crunch effectively.

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#1619332 29-Aug-2016 21:06

tdgeek:

It certainly is. As the universe expands, matter, in the form of stars and planets, etc become further apart from each other. A time will come when as stars die, the ability to produce new stars will fade, and the universe will become a very dark and very cold place. Forget what the theory was, its the opposite of the Big Crunch effectively.

Heat death. Without 'dark energy' it seems a possibility.

Little while back, came home, found the twins picking up fallen lemons.."why is there gravity? Learning opportunity! I thought.. lets talk about...

Around the bit where the Universe dissipates into eternal heat death, noticed they'd gone a bit wide eyed ..

and Mother-in-Law, who's visiting, and had been listening from the kitchen, popped out and barked “God won't let that happen, You kids come with me.."

Have to say, I can't prove her wrong..

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#1619352 29-Aug-2016 21:53

Google "opaque universe" to get some fascinating reading. This particular article* lays a lot of things out in easy to understand terms.

*for some reason the site wouldn't let me post a link in the text via my phone, so here: http://blogs.discovermagazine.com/badastronomy/2011/10/13/astronomers-have-found-when-and-how-the-cosmic-fog-was-lifted/#.V8QDKst5bqA

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#1619374 29-Aug-2016 22:57

Geektastic: I always wonder, when they say that the universe is expanding, what they think it is expanding into i.e., if the universe were a balloon being inflated in a box, what is the box?

Who says there is a box? I thought it was turtles all the way down.

I remember reading something (pretty sure it was Hawking/A Brief History Of Time, but not 100% certain) where he defined the universe as finite but boundless. So, like the surface of a ball, the universe is not infinite - there's only so much of it - but there is no boundary - no edge. You can travel across the surface in any direction and never come to an end.

And I thought that's fine of you're on the surface, but what if you're inside the ball? If you travel far enough (or fast enough) in any direction you're eventually going to come to the inner surface of the ball, and continuing in the same direction means you travel beyond the ball. So what's beyond the universe? Do the laws of physiscs even exist outside the universe as they do inside?

Is the theory that all matter was once in a single point, and is now expanding outwards from a "big bang" at that location? If so, where did that matter come from? Where was it before the bang? Was there an earlier universe that collapsed into that point before exploding outwards again? Are we just experienceing the current iteration of a universe that has been going through a constant cycle of expanding and collapsing? But even so, where did it come from the "first" time?

MikeAqua

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#1619419 30-Aug-2016 08:47

jpoc:

"What is dark energy" is probably the biggest unanswered question in physics today.

A force the emanates from ex wives!

Mike

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#1619423 30-Aug-2016 08:59

jpoc:

MikeAqua:

JWR:

But, we won't be left with just one black hole, because the expanding (and accelerating) Universe will keep that from happening.

That interests me too.

If you think about a typical explosion, acceleration of matter happens quite quickly. Initial inertia is overcome, peak velocity is reached and then air resistance starts to slow objects down again.

But the universe is a vacuum. There is no 'resistance' to overcome.

So are we seeing acceleration because the objects are still overcoming initial inertia and attractive forces.

There is no air resistance but there is gravity. That should mean that the expansion of the universe should slow down and at some point perhaps even reverse. However, the picture of the universe as expanding at an ever slowing rate has always had some troubles and a while ago, cosmologists came to understand that the universe is actually expanding at an increasing rate. Nobody knows why or what is propelling the ever accelerating expansion. We do not know what it is but we gave it a name 'Dark Energy' which makes it seem more friendly. "What is dark energy" is probably the biggest unanswered question in physics today. Lots of people are trying to answer it and whosoever comes up with an answer that can be verified by some sort of experiment is guaranteed a Nobel prize and more media coverage and fees than you can imagine.

Exciting stuff.

We all know what dark energy is ......

Here is a crazy notion, lets give peace a chance.

tdgeek

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#1619481 30-Aug-2016 09:34

MikeB4:

We all know what dark energy is ......

Just need that hand to be holding a red chocolate bar, also dark energy

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