So, life (on Earth) is much older than what was thought...

[caudor]

Trouble is that no one really knows for sure.

It could be that life is simply entertainment for immortals. Think Total Recall. You are actually dreaming up the world during your lunch break; the earth, and all its history, was created when you were born and will end when you die (or wake up).

Then you have to go back to work doing whatever immortals do.

 

[kirinke]

Rubbish all of it. Life, the universe and everything. The moment we begin to understand even a fraction of such complexities is when it immediately blows up and is replaced by something even more inexplicable.

 

[Darth K'Trava]

I really like to soak up this type of info; very interesting. Thanks.

So they think the moon was formed by a planet crashing into the Earth? Wow.

If so, there should be one huge hole in the Earth where that would've happened... even that amount of time wouldn't have totally removed traces of it.

I watched a documentary myself recently that said that the Milky Way and Andromeda are on a collision course. Our Milky Way has eaten up other smaller galaxies in the past; however, Andromeda is much bigger than the Milky Way, so our galaxy will just not the same after that happens (in about 10 billion years).

I think I've heard that at one time.

Of course, they also say the sun has about 5 billion years of fuel left before it expands (or explodes) and turns our planet to ashes.

It's possible. But since stars last for many millions of years before they either fade away or go supernova.

All are based on scientific theory as we can't predict events that far ahead. Especially for spacial phenomenon. We can only make educated guesses made on conjectures.

 

[Darth K'Trava]

A giant impact would lead to a ring of very hot debris in orbit around the young Earth. Calculations indicate that the Moon could have formed from that debris in ten years or less! This implies that the Moon would have formed very hot, possibly entirely molten. This scorching initial state is consistent with the idea that the Moon was surrounded by an ocean of magma when it formed. The magma ocean idea has been a central tenet of lunar science for decades, and recent data from the Clementine mission to the Moon finally proved it, as described in "Moonbeams and Elements," an October, 1997 PSRD article. The Moon probably continued to accrete material to it, including some objects up to about half its size. These big impacts could maintain a magma ocean, and scramble any crust that formed. It could also add rock with a composition different from the rest of the Moon, accounting for some unexplained features of the lunar interior.

Hmm.... you know... this might could explain why the moon's surfaces look like it has "oceans" on it when it doesn't have water or water vapor on it.... Molten magma that "swished" around like very thick liquid until it solidified and thusly shaped the moon's surface.

 

[tarchon]

If so, there should be one huge hole in the Earth where that would've happened... even that amount of time wouldn't have totally removed traces of it.

Collisions of that magnitude release enough energy to melt both bodies into slag, so the surface is completely reformed. The conventional model puts it somewhere before about 4.5 billion years ago, which is when the present lunar and terrestrial surfaces seem to have formed. The critical clue is the structure of the moon, which bizarrely has little or no iron core and has few volatiles. It's easy to explain one or the other but figuring out how both happened is tricky. The lack of volatiles suggests a major heating event after the original accretion of the moon, and the lack of a core would tend to suggest either that the moon originated much farther out in the solar system (which is energetically unlikely) or that it accreted from metal-depleted debris formed by some secondary process. The major success of the collision theory was in showing that the dynamics of a collision given reasonable values for the colliding masses can result in the coalescence of the two original planetary cores, while flinging large quantities of crust and mantle material into orbit. Basically, the present moon came together out of the ring of rock and dust that was ejected by the collision, so it has a rocky composition instead of the volatiles/rock/metal composition that's typical of large inner solar-system bodies.

 

[Umbran]

If so, there should be one huge hole in the Earth where that would've happened... even that amount of time wouldn't have totally removed traces of it.

Well, an impact that large releases a heack of a lot of energy. Some of that energy goes into ejecting mass (which would later become the Moon). But a lot of it has nowhere else to go, so it just goes to heating things up. Melt the surface enough, and it just flows and the whole thing becomes a sphere again, and you never know it happened.

However, you'd certainly notice it all less if it happened over 3 billion years ago, instead of less than one billion years ago.

It's possible. But since stars last for many millions of years before they either fade away or go supernova.

Depends upon the star. The bigger the star, the faster it burns. Some stars only live several billion years.

And it isn't "fade or supernova". For one thing, the fade is preceded by an immense brightening - the thing swells into a red giant before fading. And, for another, between fade and supernova lies the more mundane, ordinary nova.

All are based on scientific theory as we can't predict events that far ahead. Especially for spacial phenomenon. We can only make educated guesses made on conjectures.

We can't predict the minute details - like exactly when a given star will die. But, many of the generalities are figured out on somewhat more than a "educated guess based upon conjecture" basis. The reactions that make the star burn are more than conjecture. The effects of gravity are more than conjecture. The two get together, and make the lifespan of a star.

And it isn't like we don't have observational data. There's an entire universe we get to look at, and see if our theories predict what we'll find.