the nature of existence

[Berzerker]

how about a thread covering a wide range of subjects related to "existence"?

I got so many questions, like...

why does the "universe" appear to be expanding faster and faster?

I'm trying to visualize the mechanism and I keep coming up with bubbles - like the soapy bubbles we made as kids. Two pre-existing bubbles (or branes) - much larger than our universe - came into contact and when they parted, our universe was left behind expanding (with a snapping motion) in the directions of the passing bubbles.

But I recently saw a documentary claiming that galaxies are not really expanding away from each other (how could we be colliding with Andromeda some day?) but are moving in the same general direction - toward something beyond our universe, perhaps neighboring universes, or even the universes that bumped into each other to form our universe.

Big Crunch or Big Freeze?

If our universe was created by branes or bubbles bumping into each other, wouldn't that suggest a Big Freeze and a Big Crunch? Fuel will run out (disperse) even as the universe collapses inward, the trigger for a future expansion wont be there (I used to think our universe continually bangs and crunches).

Why dont the planets orbit the sun's equatorial plane?

I know they are close, but has the sun been tilted since the formation of the planets or did something drag the planets away from the equator and can this "something" be discerned by studying the planetary orbits? Why dont the planets have orbits more like the Galilean moons? And why does our moon orbit at ~5 degrees? That just aint right, something disrupted the Earth-Moon system after it formed.

How did the Earth get all this water? And why do astronomers keep trying to import water from further out in the solar system? First it was comets, now the culprits are water-laden asteroids.

If the Earth was struck by a large object (one that formed the Moon?), where did this collision occur and how did the Earth suffer such a large impact without a corresponding change in orbit? Why import comets and asteroids to provide the Earth's water when the Earth could have been pushed here by collisions?

Does the "face" on the Moon provide us with evidence of an impact on Earth ~3.5-4 bya or did the Moon just get plastered "normally"? The side facing us is "heavier" and looks like it was the side facing the Earth way back then as huge chunks of rock flew into the Moon.

If the Earth-Moon system was hit (the Earth taking the major impact), could it move to a new orbit as a system, or would the Moon be left behind as the Earth was pushed into a closer orbit?

It appears the Earth had surface water (even an ocean) 4.3 bya, the oldest minerals we have formed under water.
Thats one reason why comets were dropped as the Earth's source of water, not enough time for delivery, and why asteroids are being looked at. But a new theory says Jupiter and the outer planets migrated outward sending asteroids inward causing the "late heavy bombardment" ~4 bya. We had water before that... Either the Earth was formed here with water or it formed further away from the sun and was pushed into this orbit.

"Maps" of the universe showing it's structure etc dont look like any Big Bang happened, not from a "singularity" anyway. The universe appears "stretched" out a bit as if a child was pulling on playdo. I suppose the answer for this are slight variations in the singularity, or maybe I'm not really seeing what I think - I'd just expect a more "uniform" dispersion of matter from a Big Bang.

On the other hand, I use to think Big Bangs were followed by Big Crunches and that the subsequent collapse of the universe would trigger the next Big Bang, but would do so before the prior universe fully collapsed. This would mean
a Big Bang with material from the old universe still falling inward having an effect on the new expanding universe.

[gribbler]

Hey, I think I can do this one:

How did the Earth get all this water?

Hydrogen is the most common element in the universe and oxygen is the third most common element in the universe.

And why do astronomers keep trying to import water from further out in the solar system?

Wha...?

[Hauldren Collider]

I don't seem to recall us importing anything from any celestial body, unless you count all those moon rocks we brought back from Apollo.

[Berzerker]

the early solar wind supposedly depleted the inner solar system of gases, they were pushed outward to a "freeze" line

hence the need for astronomers to import Earth's water

the freeze line was the ~asteroid belt and I'd expect a planet to form there very early on - well before the outer giants.

[H Tower]

The nature of existence? It ends. Enjoy your life while you can.

[Berzerker]

I'll try , but how do you know it ends?

[Lorizael]

why does the "universe" appear to be expanding faster and faster?

Dark energy.

But I recently saw a documentary claiming that galaxies are not really expanding away from each other (how could we be colliding with Andromeda some day?)

The Milky Way and Andromeda are gravitationally bound in the Local Group to the extent that their attraction outweighs whatever repulsive force the vacuum has.

Big Crunch or Big Freeze?

Cosmology says Big Freeze right now, assuming dark energy's effect remains constant.

Why dont the planets orbit the sun's equatorial plane?

Things were pretty hectic 4.5 bya.

How did the Earth get all this water?

I read something about this recently, but I don't remember enough to comment.

"Maps" of the universe showing it's structure etc dont look like any Big Bang happened, not from a "singularity" anyway. The universe appears "stretched" out a bit as if a child was pulling on playdo. I suppose the answer for this are slight variations in the singularity, or maybe I'm not really seeing what I think - I'd just expect a more "uniform" dispersion of matter from a Big Bang.

What maps? WMAP? The differences between hot and cold regions on WMAP are on the order of 10s of microkelvins.

[gribbler]

the early solar wind supposedly depleted the inner solar system of gases, they were pushed outward to a "freeze" line

hence the need for astronomers to import Earth's water

the freeze line was the ~asteroid belt and I'd expect a planet to form there very early on - well before the outer giants.

Huh. Well, rocks can contain plenty of oxygen, in fact I think it's the most common element in the crust, so the Earth would only need to get hydrogen. Which is teh most abundant element in the universe.

[Lorizael]

Huh. Well, rocks can contain plenty of oxygen, in fact I think it's the most common element in the crust, so the Earth would only need to get hydrogen. Which is teh most abundant element in the universe.

Despite hydrogen's abundance in the universe as a whole, there's not a lot of it on Earth (or the other terrestrial planets). The theory goes that during solar system formation, light elements close to the Sun were too warm to solidify and accrete into planets. And whatever didn't get accreted was blown away by the solar wind.

[Berzerker]

I think dark energy is elasticity - like the snapping of a rubber band, or two bubbles separating leaving behind "debris" stretched out in the directions of the bubbles. Dark energy wont remain constant, it'll weaken with distance and time as the snapping motion runs its course. But if the universe is being pulled in one direction, or galaxies within the universe being pulled in one direction, that would seem to rule out our universe coming from the interaction of bubbles or branes... right? Anyone know if they've confirmed movement to some unknown great attractor beyond what we can see?

The main moons in our system have equatorial orbits, excluding ours and Triton which was probably captured. And the asteroids and comets are even more out of line - I believe only Mercury is close to an equatorial orbit. That tells me something's out there messing with the orbits. If we moved the Earth to the asteroid belt, the planets would follow a 2 to 1 ratio with the next planet in line being ~twice as far - that'd be true up to Uranus. Here's another oddity, Saturn's rings point to Pluto when its nearest the sun. And if we subtracted Saturn's distance from Pluto, we'd get another 2 to 1 ratio. One more, Saturn and Pluto ascend the ecliptic very closely - I think Pluto was ejected from Saturn and split in two during the process.

[Berzerker]

dp

[Alexander's Horse]

head spins