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Skybird · 08-08-10, 04:17 AM

That empty space and void stuff made me thinking.

I did some mathematical gameplay to see how much of the total universe we possibly could see if we compare the size of the observable universe to that of the total universe.

Let's use rounded values, it's good enough for our purposes: 1 lightyear ly = 300,000 km (3x10^5); all fractions rounded to just one decimal. We also assume that the universe(s) has the shape of a perfect sphere.

To get a first idea: how many cubic kilometers does 1 cubic lightyear hold? The term is defined by convention not to cover the volume of a sphere, but a cube. So, when 1 ly = 9.5 x 10^12 km, then multiplying this value three times with itself gives a result of

1 ly^3 = 9. 5x10^38 km^3

Now to the volume size of the different universes we have. We scale that in cubic lightyears. I base on the idea that when we can look 14 billion lightyears into every direction, then this distance is not the total diameter but the radius of a spheric observable universe.

We have three universes we want to compare to each other: the observable universe (2x14=28 billion lightyears in diamter, and two different estimations for the size of the total universe, as mentioned earlier: 78 billion and 150 billion lightyears in diameter.

The formula to calculate the colume of spheres is this:

v = (4/3) r^3 pi; r being the radius.

The observable universe has a radius of 1.4x10^13 lightyears. We enter that into the formula. We get a result of

1.1x10^40 ly^3 -> observable universe

The total universe if it is 78 billion ly in diameter. First we must devide it by 2 to get the radius, then we use the formula again. The result is:

2.5x10^41 ly^3 -> total universe with d=78 billion ly

And the size of a universe with 150 billion ly in diameter:

1.8x10^42 ly^3 -> total universe with d=150 billion ly

Now we compare the volumes by using percentage calculation. We find that if

the total universe is 150 billion ly in diameter, then the observable universe covers a volume of just 0.6% of that. That means the other 99.4% of the total universe we cannot see because in a universe of the age of 14 billion years, light has had no time to travel from there to here.

If the total universe is smaller and "just" 78 billion lightyears across, then it still is only 4.4% of the total universe that we can ever hope to see. 95.6% will remain hidden to us, always.

Now mind you that the universe is expanding. The most distant galaxies we can see move away from us with almost the speed of light. Go figure. For us humans, however, it does not make a difference, because we simply will not exist long enough as if the difference in size of the universe will make a difference to us regarding the values above for how much of the universe we can see.

Estimations say there are 100 billion galaxies in the observable universe alone. If we scale our galaxy down to 1 cm, and the Andromeda galaxy also (it compares in size to ours), both would be around 25 cm apart in that scaling. If our galaxy were a football field, then our sun would be an object so small you would need a microscope to see it. the next star to our sun would be around 4 mm away, Alpha Centauri. The ratio between space and the soze of stars and voids and the size of galaxies is such that the probability of galaxies colliding is much greater than that of stars in a galaxy colliding with each other - and this although the abuss between galaxies is so very much bigger in dimension than that between stars. In the voyage scale model http://www.jeffreybennett.com/voyage_scale.html
they have build on a mall in the US, they visualised the solar system like this: they set up scaled models of the planets in straight line in correct relatiove distances. the sun has the size of a grapefruit, the earth is an object the soze of the tip of a ball pencil, 15 m away. Jupiter has the soize of a small marble. Pluto, back then still counted as a planet, is 600 meters away. the next star system, Alpha Centauri, would be 4 thousand kilometers away: or one trvael distance from the american West coast to the East coast. As I read a joke in a book: what astromers do when looking at other planets is they find a grapefruit that is 4000 km (and high factors of that) away and then identify an object the size of a ballpencil's tip circiling around it just some centimeters or meters away.

If you ask what the solar system is, then the best reply I think is possible is this: it is nothing but empty space.

Want to talk of "space travel", anyone? the term is a hopeless euphemism, i think.

Sunday morning. Some people go to church, I do this stuff instead. The delight found might be the same.

08-08-10, 04:17 AM	#10
Skybird Soaring Join Date: Sep 2001 Location: the mental asylum named Germany Posts: 42,727 Downloads: 10 Uploads: 0	That empty space and void stuff made me thinking. I did some mathematical gameplay to see how much of the total universe we possibly could see if we compare the size of the observable universe to that of the total universe. Let's use rounded values, it's good enough for our purposes: 1 lightyear ly = 300,000 km (3x10^5); all fractions rounded to just one decimal. We also assume that the universe(s) has the shape of a perfect sphere. To get a first idea: how many cubic kilometers does 1 cubic lightyear hold? The term is defined by convention not to cover the volume of a sphere, but a cube. So, when 1 ly = 9.5 x 10^12 km, then multiplying this value three times with itself gives a result of 1 ly^3 = 9. 5x10^38 km^3 Now to the volume size of the different universes we have. We scale that in cubic lightyears. I base on the idea that when we can look 14 billion lightyears into every direction, then this distance is not the total diameter but the radius of a spheric observable universe. We have three universes we want to compare to each other: the observable universe (2x14=28 billion lightyears in diamter, and two different estimations for the size of the total universe, as mentioned earlier: 78 billion and 150 billion lightyears in diameter. The formula to calculate the colume of spheres is this: v = (4/3) r^3 pi; r being the radius. The observable universe has a radius of 1.4x10^13 lightyears. We enter that into the formula. We get a result of 1.1x10^40 ly^3 -> observable universe The total universe if it is 78 billion ly in diameter. First we must devide it by 2 to get the radius, then we use the formula again. The result is: *2.5x10^41* ly^3 -> total universe with d=78 billion ly And the size of a universe with 150 billion ly in diameter: 1.8x10^42 ly^3 -> total universe with d=150 billion ly Now we compare the volumes by using percentage calculation. We find that if the total universe is 150 billion ly in diameter, then the observable universe covers a volume of just 0.6% of that. That means the other 99.4% of the total universe we cannot see because in a universe of the age of 14 billion years, light has had no time to travel from there to here. If the total universe is smaller and "just" 78 billion lightyears across, then it still is only 4.4% of the total universe that we can ever hope to see. 95.6% will remain hidden to us, always. Now mind you that the universe is expanding. The most distant galaxies we can see move away from us with almost the speed of light. Go figure. For us humans, however, it does not make a difference, because we simply will not exist long enough as if the difference in size of the universe will make a difference to us regarding the values above for how much of the universe we can see. Estimations say there are 100 billion galaxies in the observable universe alone. If we scale our galaxy down to 1 cm, and the Andromeda galaxy also (it compares in size to ours), both would be around 25 cm apart in that scaling. If our galaxy were a football field, then our sun would be an object so small you would need a microscope to see it. the next star to our sun would be around 4 mm away, Alpha Centauri. The ratio between space and the soze of stars and voids and the size of galaxies is such that the probability of galaxies colliding is much greater than that of stars in a galaxy colliding with each other - and this although the abuss between galaxies is so very much bigger in dimension than that between stars. In the voyage scale model http://www.jeffreybennett.com/voyage_scale.html they have build on a mall in the US, they visualised the solar system like this: they set up scaled models of the planets in straight line in correct relatiove distances. the sun has the size of a grapefruit, the earth is an object the soze of the tip of a ball pencil, 15 m away. Jupiter has the soize of a small marble. Pluto, back then still counted as a planet, is 600 meters away. the next star system, Alpha Centauri, would be 4 thousand kilometers away: or one trvael distance from the american West coast to the East coast. As I read a joke in a book: what astromers do when looking at other planets is they find a grapefruit that is 4000 km (and high factors of that) away and then identify an object the size of a ballpencil's tip circiling around it just some centimeters or meters away. If you ask what the solar system is, then the best reply I think is possible is this: it is nothing but empty space. Want to talk of "space travel", anyone? the term is a hopeless euphemism, i think. Sunday morning. Some people go to church, I do this stuff instead. The delight found might be the same. __________________ If you feel nuts, consult an expert. Last edited by Skybird; 08-08-10 at 04:46 AM.