Is deep Space deep?

[alexander]

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?

 

Oh but there is lots of matter that gets "caught up" in similar trajectories. Every object in out system gets effected by out otherwise dim star. Gravity is dependent on mass, and distance, any two massive (meaning having mass) object exhibit gravitational attraction to each other, and thus curve space time. In a universe, the trajectory of a celestial body is dependent on how it got created, its mass, and speed.

 

In the simplest matematical terms, [math]F=G\frac{m_1m_2}{r^2}[/math] where F - magnitude of gravitational force between two masses

G - gravitational constant ([math]6.67*10^{-11} N m^2 kg^{-2}[/math])

m1 and m2 are masses of 2 objects

r - distance between two objects

 

actually you know what, here are some links for you for gravitational theory:

 

start here

Newton's law of universal gravitation - Wikipedia, the free encyclopedia

 

more generally (continue here)

Gravitation - Wikipedia, the free encyclopedia

 

and if you feel like frying your brain

General relativity - Wikipedia, the free encyclopedia

[modest]

Modest said

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

- :hihi:

 

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

 

Voted - Best Freudian slip of the week!

 

My keyboard just can't keep up :confused:

 

-modest

[sanctus]

 

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. ;) 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...

 

You took the analogy a bit too "real" in the sense that you did not consider that it was an analogy and so it can't describe completely the reality, otherwise it would be a model...

 

The analogy wants to say that if we were to live as two dimensional beings on the 2 dimensional surface of earth, then leaving the surface of earth would correspond to leave our usual dimensions (seeing it from a higher dimension as moontanman said). So we would leave space since as 2D-beings space would be defined to have 2 dimensions, ergo no problem on how define space there and we would have actually left space....

I hope you understand my point.

[Ahmabeliever]

Yes, I get the point, but find the arguement pointless.

 

A finite universe, is, imo, likened to a flat earth. We'll find galaxies upon galaxies when we can see further.

 

The 4th dimension huh. Fairy tale, or hypothesis or....?

 

Great links thanks Alex, you're right, relativity was a brain fryer.

 

When jesus went fishing, was he a fish friar?

[HydrogenBond]

One model I used to like to use to describe space and the universe is the house of mirrors. If one goes into a house of mirrors, we can appear to be everywhere allowing any place in the house of mirrors to show the same reference affect. It also allows us to see ourself from many angles. If we used an odd geometry, the various angles can make it look like many different things. There are only so many types of galaxies, if we view these from all possible angles we now appear to have much more variety.

 

If the house of mirror is large enough, we can also get time delays with respect to reflections. I can see a reflection of myself eating cotton candy, after I have already finished it. That can't be me, since I am already done. If we put the mirrors in motion, I can now see time delays with a red shift. If we add a bunch of people, we can get a multiplier affect making it look like 50 equals thousands or millions all in various states based on the time delay, red shift, and angle of reflection. It also appear like the 100 x100 house goes to infinity.

[Jet2]

One model I used to like to use to describe space and the universe is the house of mirrors. If one goes into a house of mirrors, we can appear to be everywhere allowing any place in the house of mirrors to show the same reference affect. It also allows us to see ourself from many angles. If we used an odd geometry, the various angles can make it look like many different things. There are only so many types of galaxies, if we view these from all possible angles we now appear to have much more variety.

 

If the house of mirror is large enough, we can also get time delays with respect to reflections. I can see a reflection of myself eating cotton candy, after I have already finished it. That can't be me, since I am already done. If we put the mirrors in motion, I can now see time delays with a red shift. If we add a bunch of people, we can get a multiplier affect making it look like 50 equals thousands or millions all in various states based on the time delay, red shift, and angle of reflection. It also appear like the 100 x100 house goes to infinity.

 

That's a great analogy! But then how big is big enough?

[LaurieAG]

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

 

Hi Sanctus,

 

How does this fit in with regards to the theory of the expanding universe and anti matter? If theres no causal implications between galaxies why would they be perceived as expanding?

 

On a lighter note. If light from one galaxy can reach another and vs a vs then there is also a potential for communications contact (possibly over vast time spans).

[freeztar]

Hi Sanctus,

 

How does this fit in with regards to the theory of the expanding universe and anti matter? If theres no causal implications between galaxies why would they be perceived as expanding?

 

I think what Sanctus was saying is that if we point a powerful telescope in one direction of the sky and find the galaxies whose light is from a time close to the big bang and then we point the telescope in the opposite direction (180 degrees) and view similar galaxies, then it is unreasonable to think that these galaxies could view each other.

 

On a lighter note. If light from one galaxy can reach another and vs a vs then there is also a potential for communications contact (possibly over vast time spans).

 

Vast time spans indeed. That's also allowing for such a strong signal that it does not degrade appreciably. Then there's the expansion problem, leading to something like Achilles and the tortoise.

[sanctus]

Exactly freez, that is what I meant.

Laurie we can say the galaxies are accelerating away from us for those galaxies where we can see their light, hence that are in causal contact with us. It is not important if there is causal contact between the considered galaxies. That we can see them both doesn't imply they have causal contact, consider Galaxy A and B both at the same distance from our galaxy, but one at theata=0° and the other at theata=180°. Now suppose that the distance is such that the light from A (and B too since we suppose them at the same distance) just reached us today. We see them both but the galaxy A has to wait another current age of the universe time to see galaxy B ( actually more due to expansion of space-time).

 

If you were asking why twwo galaxies which are in no causal contact (today) can behave in the same way (i.e. accelerating away from any other galaxy), one answer is inflation: in inflanationary cosmological models there was a time where things that are in no causal contact today were in the past. Look up Cosmic inflation - Wikipedia, the free encyclopedia

for example, but there are also other models without inflation, likes seed-models for example.

[modest]

Exactly freez, that is what I meant.

Laurie we can say the galaxies are accelerating away from us for those galaxies where we can see their light, hence that are in causal contact with us. It is not important if there is causal contact between the considered galaxies. That we can see them both doesn't imply they have causal contact, consider Galaxy A and B both at the same distance from our galaxy, but one at theata=0° and the other at theata=180°. Now suppose that the distance is such that the light from A (and B too since we suppose them at the same distance) just reached us today. We see them both but the galaxy A has to wait another current age of the universe time to see galaxy B ( actually more due to expansion of space-time).

 

Three past lightcones on expanding spacetime.

 

 

I'm sure this isn't exactly correct because I did it by hand - well, not exactly by hand... it's not the result of any code or equation.

 

The green lines are the world lines of our 3 galaxies. We are the center line. Our past lightcone is red and we can see A and B because our past lightcone includes their world line. A and B can't see each other because their past lightcone doesn't cross the other's world line - but they can see us.

 

I got the expanding spacetime layout from Ned Wright's cosmology page.

 

-modest