Is deep Space deep?

[Jet2]

Deep , wide, and tall dude, deep, wide, and tall:hihi:

 

I take this one.

 

Actually I was asking is right right? Or is wrong wrong?

[sanctus]

Hi UncleAl,

 

I think you've made a slight error.

 

While the observer is always at the pointy end of a light cone, wherever they may be in the universe, the object that projects the photons towards the observer also projects photons in all directions, including 180 degrees away from any observer, unless something gets in its way.

Nobody denies that but this doesn't imply that this two galaxies are also in causal contact...

[Ahmabeliever]

;) I think in trying to measure the volume of space we are being as short sighted as the humans who insist the world is flat.

 

Surely space is infinite. The Big-Bang a miniscule pop in the scope of things and all we know and see but one point in a region that is but one point in a region ad infinitum.

 

We can't see or detect beyond certain points, or fathom the reach of it, it is not 'a reach' to fathom. We may measure and fathom portions of space for now, between frames of reference we have, I do not think we can measure 'total space' as an area or volume or depth at all.

 

If there is an end, an edge, then you could measure it. The edge of space, imo, is the proverbial edge of the world.

[Tormod]

At least we know there is a restaurant there. At the end of the universe, I mean.

[sanctus]

42 should be the answer if I remember right Tormod.

[Tormod]

42 should be the answer if I remember right Tormod.

 

But is it 42 in time or space? ;)

[DougF]

Ahmabeliever

I think in trying to measure the volume of space we are being as short sighted as the humans who insist the world is flat.

 

Surely space is infinite. The Big-Bang a miniscule pop in the scope of things and all we know and see but one point in a region that is but one point in a region ad infinitum.

 

We can't see or detect beyond certain points' date=' or fathom the reach of it, it is not 'a reach' to fathom. We may measure and fathom portions of space for now, between frames of reference we have, I do not think we can measure 'total space' as an area or volume or depth at all.

 

If there is an end, an edge, then you could measure it. The edge of space, imo, is the proverbial edge of the world.[/quote']

Good answer! I like it. ;)

[modest]

The universe has the same geometry as inside a black hole's event horizon. No path leads outward across the event horizon. "Outside" is not meaningful.

 

1) The geometry of a black hole is different than the approximately flat geometry of the visible universe

2) You can not see out of the cosmological horizon.

3) You can see out of the event horizon.

4) They are not alike, see Eddington/Finkelstein coordinate system

 

-modest

 

They say imitation is the sincerest form of flattery ;)

[sanctus]

Modest, are you sure about 3) ?

[modest]

Modest, are you sure about 3) ?

 

Sure you can see out of a black hole. Photons don't have any trouble getting in. Strictly speaking, I don't think the event horizon is really a boundary condition. The two equations at the bottom of,

Eddington-Finkelstein coordinates - Wikipedia, the free encyclopedia

are maybe insightful.

 

-modest

[sanctus]

I see your point I never looked at it that way...

[REASON]

:doh: I think in trying to measure the volume of space we are being as short sighted as the humans who insist the world is flat.

 

Surely space is infinite. The Big-Bang a miniscule pop in the scope of things and all we know and see but one point in a region that is but one point in a region ad infinitum.

 

We can't see or detect beyond certain points, or fathom the reach of it, it is not 'a reach' to fathom. We may measure and fathom portions of space for now, between frames of reference we have, I do not think we can measure 'total space' as an area or volume or depth at all.

 

If there is an end, an edge, then you could measure it. The edge of space, imo, is the proverbial edge of the world.

 

I have always perceived space to be infinite as well, and that the universe is expanding within the void. But I'm sure I recall a theory that suggested that space and time are intertwined such that they were both created simultaneously with the Big Bang, meaning that everything, all matter, energy, space, and time occupied the same initial point, and has expanded outward. This would imply that the there actually is an edge to space.

 

But then I always wondered, "oh yeah, well what's on the other side then?" :shrug:

 

Does anyone know this theory?

[freeztar]

But then I always wondered, "oh yeah, well what's on the other side then?" :shrug:

 

Does anyone know this theory?

 

I think UncleAl answered this one well earlier in this thread. He said:

"Outside" is not meaningful.

 

What he means by this is that our lightcone can never coincide with the photons streaming (and expanding) "outward". We simply can never "catch up" to it.

 

Here's a much better explanation:

What is at the edge of the universe?

[Moontanman]

I think UncleAl answered this one well earlier in this thread. He said:

"Outside" is not meaningful.

 

What he means by this is that our lightcone can never coincide with the photons streaming (and expanding) "outward". We simply can never "catch up" to it.

 

Here's a much better explanation:

What is at the edge of the universe?

 

 

I rather like the answer provided by brane theory, Our infinite universe is quite finite when viewed from a higher dimensional perspective. Even though we cannot ever get to the edge of the universe it is still there just like the surface of the earth has no edge but if you go at a right angle to the surface you find a space outside the two dimensional surface of the earth. Just becasue you can't see outside the light cone doesn't mean it's not there. Our three dimensional universe can be thought of as the three dimensional surface of a four dimensional sphere.

[modest]

But I'm sure I recall a theory that suggested that space and time are intertwined such that they were both created simultaneously with the Big Bang, meaning that everything, all matter, energy, space, and time occupied the same initial point, and has expanded outward.

 

Doesn't necessarily imply:

 

This would imply that the there actually is an edge to space.

 

The most elegant solution cosmologists used to be fond of was a positively curved universe - like a ball. This would make the universe closed allowing it to have a limited amount of space and matter and yet have no edge. Stephen Hawking proliferated this idea to the public in 'A Brief History of Time'.

 

If you draw a big triangle in a closed universe and measure the angels they will add up to more than 180 degrees. Also, if you shine a laser beam off into space and wait long enough it will go around the universe and hit you in the back of the head (assuming the universe isn't expanding too quickly). This closed geometry was compelling, however:

 

WMAP used elements of the universe to conceptually draw a really big triangle and measured the sides which came up a statistical dead-even 180 degrees. This makes the universe flat (or Euclidean in its geometry) - commonly thought of like a sheet of paper. So, it's now mostly accepted that the universe is open and infinite. If you shine a laser off into space - it just keeps going forever.

 

This open and infinite model is a bit more of a head-scratcher than a closed solution would be:

 

I suppose infinity always dazzles us, and I have never been able to build up a good intuition about the concept. The problem is compounded here because there are actually two infinities competing with each other: there is the infinite volume of space, and there is the infinite shrinkage, or compression, represented by the big bang singularity. However much you shrink an infinite space, it is still infinite. On the other hand, any finite region within infinite space, however large, can be compressed to a single point at the big bang. There is no conflict between the two infinities so long as you specify just what it is that you are talking about.

-Paul Davies 1992 'The Matter Myth'

 

I'd say the most common sentiment is Freeztar and UncleAl's comment about not imagining what is beyond our visible part of the sky. There is nothing wrong with that approach. I've said as much myself. However, it is something that gets said a whole lot more now that we estimate the universe is open and infinite. I suppose it avoids questions like "how can something infinite in size expand?" and "how can something infinitely big fit into an infinitely small space?"

 

So, how deep is space?

 

I think both answers are correct:

• infinitely deep
  
• 13.7 billion years light-travel-time deep
  

 

-modest

[Ahmabeliever]

Moontanman said

Even though we cannot ever get to the edge of the universe it is still there just like the surface of the earth has no edge but if you go at a right angle to the surface you find a space outside the two dimensional surface of the earth.

 

If you go at a right angle you will still be in space, presense of matter or not. In that instance defining space would need to be defined as that portion of space containing matter? I think there is space forever, if there is space that retains no matter I don't know, but even if there is, it is still space. The 'folds' of it may fool us into seeing another globe due in part to our knowledge the earth is not flat. :hihi: Perhaps there is a spherical shape to the part of the universe we see, but it is merely a jot of a jot of a jot...

 

Our ego struggles with infinity no doubt. I think every point of the universe is the centre of the universe. So we are the centre of the universe and can relax... :) A big bang is a ripple. The variables in an infinite universe are also infinite.

 

The edge of the universe link said

Einstein first came up with the idea of gravity curving space. That's how the Earth orbits the sun. It wants to go straight but the Sun curves the space around it so the Earth can't go flying off.

 

Why doesn't a bunch of stuff get caught up in the same trajectory of the Earth and other planets then? Does matter need to be in the same position according to the date, and we collect it ie: meteorites. Does it need to be the same sized mass to be caught in the same trajectory?

 

I guess we've proved this for the most part with orbiting satellites.

 

Gravity curves space where mass is present. I believe our ability to measure mass is faulty, or that all mass in space is not equal and some has more 'pull' than we give credit for. Perhaps density of matter is not so important as reactivity of matter to other matter. Hence the reason we lost 2 space capsules.

 

Modest said -

If you draw a big triangle in a closed universe and measure the angels

:confused:

 

Perhaps gravity is caused by the beat of their wings :D

 

Voted - Best Freudian slip of the week!

[freeztar]

Perhaps gravity is caused by the beat of their wings :D

 

Ithink he meant to say that the angels wings would be greater than 60 degrees. :confused:

Voted - Best Freudian slip of the week!

 

Agreed. I completely read over it. Funny how the brain works. :hihi:

 

Although, in truth, I assume that it was more of a typo than a freudian sip. :)