Astrophysics and Cosmology - Discuss the Universe here

[eddie dean]

Possible waves on  Titan

"Reflections on the oceans of Saturn's largest moon suggest long-sought extraterrestrial ripples."

http://www.nature.com/news/first-hints-of-waves-on-titan-s-seas-1.14889

[zeebo]

Possible waves on  Titan...

Cool, I love any discovery that makes my sci-fi book covers more likely.

[Camazotz Automat]

Possible waves on  Titan
"Reflections on the oceans of Saturn's largest moon suggest..."

Ever the mammal, I did NOT initially read that as "long-sought extraterrestrial ripples."

[eddie dean]

Ever the mammal, I did NOT initially read that as "long-sought extraterrestrial ripples."

Green 'Ripple' slip

[attachimg=1]

[zeebo]

This is from like a year and half ago, but it's news to me.  Does anyone know if this is still being pursued?

http://io9.com/5963263/how-nasa-will-build-its-very-first-warp-drive

[area51drone]

This is from like a year and half ago, but it's news to me.  Does anyone know if this is still being pursued?

http://io9.com/5963263/how-nasa-will-build-its-very-first-warp-drive

Why spend the money when we already have them at area 51?

[Agent : Orange]

Hey all

I've been so busy it's crazy, so I haven't been on the board for a week. However, I had to show up briefly just to post this!!

http://www.eso.org/public/announcements/ann14021/

From the announcement:

"An international team of astronomers, led by Felipe Braga-Ribas (Observatório Nacional/MCTI, Rio de Janeiro, Brazil), has used telescopes at seven locations in South America, including the 1.54-metre Danish and TRAPPIST telescopes at ESO’s La Silla Observatory in Chile, to make a surprise discovery in the outer Solar System.

This unexpected result raises several unanswered questions and is expected to provoke much debate. A press conference will be held in Brazil to present the new results and allow opportunities for questions. "

That sounds mysterious... this is exactly how Rendezvous with Rama started.
Wish Art were still doing shows, this is the kind of mystery he would jump at.

We'll find out this afternoon what the big to do is all about...

[Agent : Orange]

Wow so cool, ESO found an asteroid with rings around it!
http://www.eso.org/public/news/eso1410/
It's not Rama, but it's still very cool and exciting, not just that such a thing exists (I never imagined such a small body could have a ring system) but also awesome they were able to detect it at all.

And one more neat one for the day: Could there be a 10 Earth-mass planet lurking in the inner Oort cloud?
http://www.nature.com/nature/journal/v507/n7493/full/nature13156.html

Between a ringed asteroid and waves on Titan's lakes my mind has been blown to all the stuff that we have sufficiently sensitive instruments to detect, and also at how much there is still to learn in our own backyard.

Long rant on the amazing gravity wave observations from last week and what it means for inflation incoming... for now back to work

[zeebo]

It's not Rama, but it's still very cool and exciting...

Damn I want my Rama!

Could there be a 10 Earth-mass planet lurking in the inner Oort cloud?

Hey Agent, dumb question - Is the Oort cloud still hypothetical or is it pretty much fact now?

Long rant on the amazing gravity wave observations from last week and what it means for inflation incoming...

A physicist on c2c last week mentioned that somehow this discovery implied the actual universe is much bigger than the observable one, which I wanted to understand better, but Noory decided instead to ask the guest about something more important like how you spell "big bang".  Perhaps you could give your thoughts?

[Camazotz Automat]

If there is a 10 Earth mass planet in the Oort network, perhaps it is what often perturbs the stable orbits of comet-sized objects into trajectories that send the comet toward the Sun or altogether outward, away from the cloud? At the very least, it makes you wonder if it is slowly vacuuming up comets like a mini-Jupiter. Then again, I have not a clue what the plot lines of a "cloud" of objects would look like and if there are intersections between objects.

[area51drone]

10 earth mass object in oort cloud == planetx folks

[zeebo]

I've decided to skip the broadcast Cosmos, and wait for a probable dvd release down the road.  It's really packed with jarring commercials and all the ugly and distracting promos superimposed on the screen really suck.  The content is promising but I just can't get into it this way.

Also, as long as I'm bitchin, it's fairly disjointed, it's moving too fast, there's too many over-the-top special effects, and the music is awful like something out of a Lifetime thriller.

The issues raised on this show are profound and important, and I just wish the new one had a presentation more like the original - with it's more meditative, reverent presentation and it's soaring soundtrack commensurate with the soaring ideas.  And we need some time to absorb some of these ideas and ponder them - I don't know why this has to look and feel like some modern action movie hurtling forward from scene to scene.

For instance the episode I tried to watch tonight, was supposedly about light/time/space but they only spent a few minutes on Einstein and never really explained much about relativity before getting to some black hole action sequence.

That said I'm sure I'll watch the entire thing at some point since I think there's still alot of good stuff in there.

[area51drone]

It's not as good as the original, no doubt.  And I didn't see the original until maybe 7-8 years ago.    Zeeb, just d/l it and save yourself the commercial hassle.   It's all over the web commercial free.

[Camazotz Automat]

And you know, zeebo, as soon as you stop watching, that is when the truly amazing episodes will air.

It's some kind of Schrödinger effect.   

[zeebo]

And you know, zeebo, as soon as you stop watching, that is when the truly amazing episodes will air.

It's some kind of Schrödinger effect.   

Haha yes perhaps you can know the time a show is on, or the likely greatness of a show, but not both.   

[zeebo]

...Zeeb, just d/l it and save yourself the commercial hassle.   It's all over the web commercial free.

Thanks, good idea (unless of course there is some rights issue I don't know about in which case of course I'm speaking only hypothetically and would never dream of downloading anything.)   : 

[area51drone]

And you know, zeebo, as soon as you stop watching, that is when the truly amazing episodes will air.

It's some kind of Schrödinger effect.   

Since I'm watching them, good episodes will never air. 

[area51drone]

Thanks, good idea (unless of course there is some rights issue I don't know about in which case of course I'm speaking only hypothetically and would never dream of downloading anything.)   :

nzbclub + unzbin + usenet provider = no hassle

xsusenet is a free provider, but their smallest paid subscription package is well worth it

[area51drone]

BTW, watching the latest cosmos now.  Agent, or anyone else for that matter, I have a question for you.   I have heard this before, and NDT just mentioned it in Cosmos - the idea that no matter where you are in the universe, you are at the center of it.   

The question I have is how can that possibly be?  If the big bang started from one point, and space has expanded from that location, there must be some matter that is closest to the edge of nothing compared to where we are, for example?   I have never been able to wrap my puny misogynist brain around the idea that somewhere must be the edge of space.

[zeebo]

nzbclub + unzbin + usenet provider = no hassle

xsusenet is a free provider, but their smallest paid subscription package is well worth it

This is interesting information, which of course I will use for informational purposes only.

[area51drone]

Nobody has any thoughts on my post about "being the center of the universe"?

[Agent : Orange]

There is no center of the universe because all of space and time is wrapped up in the big bang, it's not like a conventional explosion into something that existed before it. This means that every point in the universe is the center because all points overlapped at the first instant. Think of it like this: right now I am in the milky way galaxy and I can look out, I see a horizon around my position and measure the temperature of the CMB to be 2.74 kelvins, and measure the local matter density and the Hubble constant and a number of other such values. Then lets say I go somewhere else - it doesn't matter where - and repeat my observations. I could go to the Andromeda galaxy or I could go to a distant quasar and repeat my observations. I would measure the same cosmological parameters I could see here. Every point has a local horizon around it, which is determined by the speed of light and the expansion of the universe.

A simpler way of putting it is to think of a person constrained to move on the surface of a sphere, or an ant on a balloon that's inflating. This observer can walk around the surface of the balloon but can't move in the third dimension. Anywhere this ant stands on the surface of the balloon it will look to them like they are at the center - there is always more balloon that forms their horizon no matter where they are. There's no edge or boundary to the balloon. To someone on the surface it looks like all the points on the surface of the balloon are the same and that there is no center. The surface is two-dimensional, mind you, while the entire balloon is three dimensional and in 3D we can always step back and say that the perspective of the ant is limited because they are not seeing the full picture.

This analogy fails for the actual universe because the balloon is expanding into a pre-existing space, and that's what makes the big bang different. Everything came from the big bang, including all of space and time.

Sorry again I have not been posting much, it's been one of those times for me. Hopefully things will lighten up soon and I can start poking around here a bit more.

[area51drone]

There is no center of the universe because all of space and time is wrapped up in the big bang, it's not like a conventional explosion into something that existed before it. This means that every point in the universe is the center because all points overlapped at the first instant. Think of it like this: right now I am in the milky way galaxy and I can look out, I see a horizon around my position and measure the temperature of the CMB to be 2.74 kelvins, and measure the local matter density and the Hubble constant and a number of other such values. Then lets say I go somewhere else - it doesn't matter where - and repeat my observations. I could go to the Andromeda galaxy or I could go to a distant quasar and repeat my observations. I would measure the same cosmological parameters I could see here. Every point has a local horizon around it, which is determined by the speed of light and the expansion of the universe.

A simpler way of putting it is to think of a person constrained to move on the surface of a sphere, or an ant on a balloon that's inflating. This observer can walk around the surface of the balloon but can't move in the third dimension. Anywhere this ant stands on the surface of the balloon it will look to them like they are at the center - there is always more balloon that forms their horizon no matter where they are. There's no edge or boundary to the balloon. To someone on the surface it looks like all the points on the surface of the balloon are the same and that there is no center. The surface is two-dimensional, mind you, while the entire balloon is three dimensional and in 3D we can always step back and say that the perspective of the ant is limited because they are not seeing the full picture.

This analogy fails for the actual universe because the balloon is expanding into a pre-existing space, and that's what makes the big bang different. Everything came from the big bang, including all of space and time.

Sorry again I have not been posting much, it's been one of those times for me. Hopefully things will lighten up soon and I can start poking around here a bit more.

Hmm... I'm still not following.   Why use the balloon analogy if it's wrong to think about it that way?  I understand what you're saying in regards to a horizon on a balloon.  But I don't see how that equates to 3D space.   In the analogy, is the volume of the balloon time?   Are you saying that "looking up" from the balloon's surface would be equivalent to looking into the future?

In real life, what is the 3D shape of the universe assumed to be?

[Agent : Orange]

Hmm... I'm still not following.   Why use the balloon analogy if it's wrong to think about it that way? 

It's an analogy that illustrates the point well enough, but it's not the full description because otherwise it becomes a mathematical discussion. The real picture is in four dimensions, but it's not at all intuitive to think that way (but four dimensional equations can be solved just fine). So it's easier to talk about lower dimensional analogies sometimes.

I understand what you're saying in regards to a horizon on a balloon.  But I don't see how that equates to 3D space.   In the analogy, is the volume of the balloon time?   Are you saying that "looking up" from the balloon's surface would be equivalent to looking into the future?

Roughly, yes. Just as the ants are on the 2D surface of the 3D balloon you can think of us on the 3D surface of a 4D universe but even that's not exactly right. I just don't think I really have the words to say it any better. 

In real life, what is the 3D shape of the universe assumed to be?

The geometry has been measured to be flat, and the universe is driven to be this way naturally because of inflation at early times which gives a beautiful description of why it must be. On the *largest* scales (larger than the observable universe) the 3D "space" part of space-time is more like a sphere. Since we live in a very large universe that extends out beyond our local horizon (which is bounded by the CMB), our patch of universe and any other patch you could observe from will always appear locally flat.

But this is exactly what  the ants on a very large balloon would also think. Any sphere (including the Earth) looks flat when you look on sufficiently small scales.

Even this is just an analogy though maybe we've gone a bit beyond the ants on the balloon. But you can't REALLY talk about chopping up space and time in that way except for a few limiting cases. They are tied up with one another and when you start trying to break them apart it becomes a bit touchy.

[area51drone]

Even this is just an analogy though maybe we've gone a bit beyond the ants on the balloon. But you can't REALLY talk about chopping up space and time in that way except for a few limiting cases. They are tied up with one another and when you start trying to break them apart it becomes a bit touchy.

I don't want to talk about ants on a balloon.  I want to really understand what is happening.   Let's save part of this discussion for later and just discuss the 3D space that we are all familiar with.

I understand fully what it means to see a "flat" horizon when you're standing on the surface of the earth looking out over the ocean.   But clearly, on even our scale, the observable universe is NOT flat in 3D space.  Explain why I can look north and see stars, and look south and see stars.   Let's pretend we have an imaginary space ship that can travel with local time at infinite speeds, without warping space.   I hop on said space ship, pick a direction and press the GO button.   If I hit a planet, a sun, or a black hole, let's just assume that I can travel through it in the same direction I was headed in in the first place.  Where will I end up, back home eventually?

When you look at the problem, are you able to "see" in your mind what is happening, or are you just solving equations?   

[Agent : Orange]

I don't want to talk about ants on a balloon.  I want to really understand what is happening.   Let's save part of this discussion for later and just discuss the 3D space that we are all familiar with.

I understand fully what it means to see a "flat" horizon when you're standing on the surface of the earth looking out over the ocean.   But clearly, on even our scale, the observable universe is NOT flat in 3D space.  Explain why I can look north and see stars, and look south and see stars.   Let's pretend we have an imaginary space ship that can travel with local time at infinite speeds, without warping space.   I hop on said space ship, pick a direction and press the GO button.   If I hit a planet, a sun, or a black hole, let's just assume that I can travel through it in the same direction I was headed in in the first place.  Where will I end up, back home eventually?

When you look at the problem, are you able to "see" in your mind what is happening, or are you just solving equations?

The universe is flat - geometrically flat - such that parallel lines never cross, and even large triangles have the sum of all angles equal to 180 degrees. This kind of space is like the balloon surface + 1 extra dimension. That's why the balloon example is just an analogy but one which is good for visualizing this, it's surface is only 2D instead of 3D. But all of the geometrical tests the ants could do on such a surface are the same kinds of tests we could do in our universe and we would come to the conclusion that it's geometrically flat globally. Hope that helps.

"Seeing" these ideas in your mind is the same as solving equations. No one can really visualize the fourth dimension except through analogy, the closest and most pure way there is to "see" means that you must solve equations. Which is why describing it with no math only gets you so far.

Escher wrestled with the concepts of geometry in his artwork in an attempt to express the mathematics visually.

[Camazotz Automat]

As a boy, I became concerned about a fourth spatial dimension; there's little doubt that Madeleine L'Engle served up this mutant seed.

On the earliest library search that I remember, some book stated that in the fourth dimension, I could turn an inflated basketball inside out without any of the air escaping from the sphere.

So I've always worked from that.

It gives me comfort and helps me briefly escape Euclidean space.

Infinitely Chubby Checker:

Come on, baby, let's tesser like that....
Come on, baaaaaaaay beeeeee.... let's do the tesseract.....
Come on, baby, let's tesser like that....

[zeebo]

The universe is flat - geometrically flat - such that parallel lines never cross, and even large triangles have the sum of all angles equal to 180 degrees....

Agent is this true whether the 4-dimensional shape is hyperbolic or spherical or whatever?

Also, here's a question that occurred to me recently.  When we talk of the expansion of space, is space actually being created?  Or is it just stretching and if so is it infinitely elastic?

[area51drone]

On the *largest* scales (larger than the observable universe) the 3D "space" part of space-time is more like a sphere.

The universe is flat - geometrically flat - such that parallel lines never cross, and even large triangles have the sum of all angles equal to 180 degrees. This kind of space is like the balloon surface + 1 extra dimension. That's why the balloon example is just an analogy but one which is good for visualizing this, it's surface is only 2D instead of 3D. But all of the geometrical tests the ants could do on such a surface are the same kinds of tests we could do in our universe and we would come to the conclusion that it's geometrically flat globally. Hope that helps.

Maybe I'm missing something, but this doesn't answer my question, or does it?  Where would my imaginary ship end up?   If on a large scale, you say the universe is a sphere, we should eventually hit the "edge" of space, would you not?   What is at the edge of space?

[zeebo]

Maybe I'm missing something, but this doesn't answer my question, or does it?  Where would my imaginary ship end up?   If on a large scale, you say the universe is a sphere, we should eventually hit the "edge" of space, would you not?   What is at the edge of space?

I'll take a shot, as I understand it.  Travelling through 4-d curved space in a spherical universe would be like travelling across the surface of a sphere in 3-d space, such that you would never hit an edge but eventually come back to where you were.  (If in fact 4-d curved space is not closed/spherical but open/hyperbolic then it would be the same experience but you'd never return to your starting point.)  Well physics geniuses, am I close?