The theory is disputed, but many physicists agree that the universe can't just expand indefinitely, and will likely being to shrink again eventually; and then the whole process will repeat.

You know, I completely forgot about that one. I learned that in public school back in elementary school / 6th grade. I've been through biology and chemistry honors, and not once has my christian school even mentioned that.

I believe more in the second theory.

Wow, haha. This is a really interesting topic! A very science-y one.. My favorite type :)

If we don't kill each other with nuclar weapons and stuff, I have my own ideas of now the Earth will will end..

One: Grey goo will take over the world and kill us all. (If you're too lazy to follow the link, it's a fictional self-replicating nanobot.) Yes, I am a nerd who loves science. And of course, nanotechnology, which I studied quite a bit in July.

Two: Seeing as I probably know know more about astrophysics than most of you, my theory is WAY different. I am warning you guys, this is gonna be long.

OK. So do any of you know that the Earth's magnetosphere is changing? Like flipping literally. The magnetosphere is this "shield" for the Earth that causes magnetic North and South. When the magnetosphere flips, the North Pole will be the South Pole and vice versa. (There is proof of this, by the way. In ancient Chinese Pottery and volcanic rock and the Mid-Atlantic Ridge and lots of stuff.) It usually flips every few thousand years or so (I think), and but it's been 70,000 (I think) years since it reversed. (I'm not sure about the dates, but I KNOW it's long over due. I learned it in Astrophysics class.) Anyways.. As it reverses, the magnetosphere weakens. And since the magnetosphere is what protects us from the sun (CMEs, solar wind/solar flares, ect.), we get more vulnerable to it. Now, sun damage causes skin cancer, and scientists estimate that as the magnetosphere weakens, millions of people per year will die from skin cancer and other related things. That could be what destroys the Earth, but I'm not finished.

Now, scientists have this theory that Mars' magnetosphere (yes, it was like Earth in its earlier years. They have sent SEVERAL missions and pretty much proved it) just.. disappeared. Now how could that have happened? Ok, you guys know that the liquid core is what generates the magnetosphere and the magnetosphere is what causes the liquid core to circulate, right? (I don't want to get into that topic too deeply.) OK! So over time, the liquid core of Mars cooled to the point it was solid. So when the core is solid, it can't circulate at all, causing the magnetosphere to just disappear. And when the magnetosphere just disappears, the planet is pretty much doomed. It's MUCH more vulnerable to the sun. What will happen? All the WATER is evaporated, the atmosphere disappears, all life forms die, ect.
That's why they call Mars the "Dead Planet."
And that's my theory. Not as long as I expected, but it's pretty long. I really wanted to cover other things, but seeing as it's like 2AM and I'm really tired....

BTW, they say the magnetosphere will most likely reverse in 400 years, so we don't have anything to worry about.

you are quite interesting ;O

Don't know about the end of earth but the Sun one sounds convincing. If anything we will die off. But I don't think it will be in my time or my kids. There's going to be a primetime TV special on thie on Aug. 29 I don't know why. Gotta live life regardless and can't worry about that stuff.I think HUMANS will be the ones to die off first, then earth will end a long while later. But then the Earth destroying and all the other planets are lonesome, it makes me think...was there ever life on those other planets?



New heaven,new Earth. Also, a lot of the stuff that the bible predicts is happening now. I always questioned until now.



It's repairing itself now.

Me? Haha, thanks!

I believe there used to be life on Mars. And I definitely believe in life on Europa (a moon of Jupiter. It has oxygen on its surface. Water under ice. Volcanos underwater.) under the thick layer if ice. And I'm very, very sure that there is life on other planets. I pretty much have no proof, but I strongly believe in it.

I don't believe Sun thing 'cause I don't think Earth can live for another few billion years.. And humans probably won't die first 'cause just look at the endangered species list! But if you're talking about Humans vs. the Earth, it's definitely Humans because we're more vulnerable than the Earth.
If humans survive the next few hundred years somehow, without nuclear war or something skin cancer will probably wipe out a lot of us, as mentioned in my theory.'

Oh, and if the sun thing really happens, then the end of the Earth thing will really happen 'cause Earth will be vaporized.

We'll run out of chocolate.

^ Really? You wouldn't be alive at that time, so why would you care that much about chocolate?

I didn't bother to read the other posts, but whatever.

Here's how I think the world will end: We all know about global warming. The sea levels will rise and the population will be forced to move more inland. We'll use up all our resources and let out more pollution. The weather would get all screwed... It would get too hot for agricultural production. More famines, more starvations. There won't be enough food or resources to keep up with the growing population. And combine that with global epidemics. We'd be killing ourselves.

I think it makes sense.

I think this topic is leaning toward the end of the Earth rather than the extinction of mankind.

^ oh. you're right. haha. forget everything i said :P

The end of the world?

I heard it starts with an earthquake, with birds, snakes and airplanes.

Yes, you!

Oh, last night, I watched this show in ABC.. I think it was called Last Days on Earth or something like that AND THEY DIDN'T MENTION MY THEORY!
Oh well. It was probably too smart for them to think of it.

Yeah. Well it talked about a huge asteroid and disease and global warming and nuclear war. But that isn't really the end of the Earth, now is it? It would just be the end of the Earth for us.
Now are we talking about the end of the Earth or the extinction of mankind?

i belive the universe will end when GOD comes down and takes is back...and for the rest... read the bible and find out

Besides, some of us don't have the time to read a 1000+ page book..

Yeah, you a$$hole. you dont need to make it so big and mighty ... shit.





I know why. Your theory isn't very common or thought able.




But I heard a similar story to your theory. From what I heard, a huge asteroid could possibility hit Earth causes the magnet field to change. Earth's North and South Pole can changed its location due to the alignment of Earth.



Scientist had a theory similar to Uranus because the ring's position was odd. Same with other planets, the rings tilts. it was suppose to be horizontal. That means, if the planet alignment change, the ring will change.



Ever heard of that?

^
I've never actually heard those theories before. Thanks for sharing!
Changing the magnetic field can be really deadly.. If the North Pole shifts to the equator or somewhere near it, lots of solar particles can escape through and possible harm the environment.
But so you're saying that if the poles change, then the Earth is gonna tilt?
That's crazy, but it could happen.
Can you explain it some more in detail?

It can affect out geography, climates, temperature, and weather. If the north pole roll to another location where the equater is, the ice/glacier will melt. It will pretty much be like ... The Day After Tomorrow which is similar to the gobal warming.







I'm saying, if a huge strong asteroid hit Earth, Earth will roll, changes the pole, climate will change, and will face the sun in a different way.



For an example, the North Pole roll and it faced the sun. Do you know what will happen next? The ice will melt into water causing the ocean level to rise.



here's an example that i did on MS Paint ;]


It's the same thing happens to one of the planets in our solar system *******

Global warming is actually what caused The Day After Tomorrow.. Global warming caused the ice caps to melt and decreased the salinity of the ocean and the Atlantic current changed so the climate changed drastically.


And after the ocean level rises, the salinity level of the water to decrease and the currents might change! And people near coasts will have to be evacuated..

And whatever part is North/South will freeze up! What if that's the US? Now, that'll be a national catastrophe..

And that is a very interesting drawing you made :)
But then, don't you think humans will die if an asteroid hit the Earth?

It depends how the asteroid hit the earth.

Well, either way.
99% of humanity will be wiped out.



-------




If North Pole becomes South Pole and South Pole becomes North Pole, we'll survive.

Yeah. There'll be a lot of tsunamis and volcano explosions and earthquakes all over the world!
And the remaining people might die too, of hunger or something.



And if the Earth turns because of an asteroid collision and the poles switch, we'd still die out..

Wait, how do we still died, when the pole just changed?







------

Interesting. I had never thought of natural disaster could happen. The asteroid is a disturbance to Earth's surface.

I guess sea animals will dominate the world. YAY, GO SEAL!



poor polar bear ;[

Well, the asteroid collision would kill us, wouldn't it?


Yes, the sea animals will dominate. And maybe animals living underground if they don't die out from earthquakes and volcano explosions and stuff.

But then the climate change might be too drastic and everything might die out.
Except for maybe single-celled organisms like bacteria.

oh oh oh yeah. It would annihilate part of human population.



asteriod collision AND gobal warming will kill all of us. (most likely)



Earthquakes, volcanoes, and tsunami are a good bonus to kill us faster.

BUT scienctists are trying to find a way to change an asteroid's orbit by using some type of spacecraft..

If they're unsuccessful, then yes, we'll probably all die out from earthquakes, volcanoes, and tsunamis caused by an asteroid collision.

The truth is...

WE WILL NEVER KNOW.

It's good to estimate though.

we'll kill ourselves long before anything in the cosmos does.


it'd be a true tragedy, if we are smart enough to walk on the moon, if we are smart enough to build nuclear weapons. but we're not smart enough to save ourselves.

and psh, Gama ray burst are extremely closer to happening than the universe closing in. or the sun expanding/exploding. and its scarier. you'll literally burn to death. because the ozone layer will be completely gone. well first of all, on the first day of one happening in our galaxy, the sky will appear to have two suns, not one. this will cause the sky to be so bright, anything with eyes will be blinded. and on, lets say the 3rd day, is when the the ozone layer is completely wiped out. causing us absolutely no defense against the UV rays from the sun, and radiation from the gama ray. first everyone will look as if they have an extremely bad sunburn. and because of the radiation, your cells will lose the ability to be able to regenerate. causing your hair and your finger nails to cease growning. and even worse since the cells in your intestines cant regenerate either, you'll lose the ability to consume food or water. =/
scientist see at least about 2 of these a day in different galaxies. but what if one happens in ours?

so you can use your imagination. and this isnt even the nearest threat in the cosmos.

like i said, we're our worst enemy.

global warming is the biggest and nearest threat to man-kind right now. but i hate how people continue to belittle it. *sigh*

The ozone doesn't protect us from gamma ray bursts.. Or at least that's what I remember.

It's supposed to be the magnetosphere (magnetic field), right?

It might happen if the power of the magnetic field continues to decrease.. But then we won't have sunburn. It'd be skin cancer.


And the ozone layer is repairing itself. Or at least that's what BBC News is saying..
http://news.bbc.co.uk/2/hi/science/nature/5276994.stm

i didnt say it would protect us from gama ray bursts. i said a gama ray burst would obliterate the ozone layer. not gradually, right then and there. like a nuclear bomb effect. it wouldnt necessarily destroy the planet because our nearest star isnt close enough for that to happen. so humanity would die because of the mere effects. but thats not necessarily the earth i guess though.

and it doesnt matter if the ozone layer even is repairing itself. from global warming, the tempature will rise at pretty concerning speeds just because of the Co2 in the air already, not necessarily only because of UV rays.

The danger is that global warming may become self-sustaining, if it has not done so already. The melting of the Arctic and Antarctic ice caps reduces the fraction of solar energy reflected back into space, and so increases the temperature further. Climate change may kill off the Amazon and other rain forests, and so eliminate once one of the main ways in which carbon dioxide is removed from the atmosphere.



The rise in sea temperature may trigger the release of large quantities of carbon dioxide, trapped as hydrides on the ocean floor. Both these phenomena would increase the greenhouse effect, and so global warming further. We have to reverse global warming urgently, if we still can.

Yeah, they say that greenhouse gases might postpone the healing of the ozone layer too. Or even not allow it to heal at all.

But then the magnetosphere would block gamma ray bursts, so I don't really think it's possible for the gamma rays to escape through..

Can you explain how the ozone would be depleted? Because the magnetic field would be in the way..

Oh really? dont drive a car, take the bus, or anything that contribute the gobal warming. If you do, you'll just hate yourself. i'm sorry.





If Earth loses its ozone layer, think of Mars.
Yes. Mars doesn't have ozone layer anymore. The environment is mainly CO2.

It does matter if the ozone layer is repairing. Ozone layer is our protection and a source of survival.





This is Mars without the ozone layer

Destruction spawns rebirth.

The human race is so flawed that we'lldestry this planet before nature can run its course.

i want to see some zergs and protoss ;[

^
Err. Starcraft?

HAAHHAHA. YEAH.

i think it will be like in The Day After Tomorrow. lmao, i know. but i mean, i do think that theres going to be all that stuff: hurricanes, avalanches, etc. in california, it's already over a hundred degrees each day. what is it going to be like in the next ten years? i think the world will destroy itself first. i don't really believe in those theories.. they don't seem true. i mean, COME ON, Earth is not just some ordinary star.

^ The Day After Tomorrow was caused by global warming.. The Atlantic Current was pretty much what caused it all, or so I remember. And the Atlantic Current changed because the ice caps were melting causing the salinity level to decrease and so the current changes.. Yeah.


Ohh, there was something I've been wondering for a while..

Did California ever had hurricanes in the past? Other than the recent one..

god will destroy it

I dont think so. I live close to San Andreas fault and the beach.



California is mainly earthquakes.

Oh, so then the one that hit a few weeks ago isn't normal?

Climate change.. It's all caused by global warming.

and global warming was the Cause for the ice caps melting....

I think it'll be due to Global Warming, if we dont do anything to slow it down now... while we still can.

We'll all kill ourselves.

Yeah.

the planet will be converted into a technological rock and we'll wander space and create new civilizations across the galaxies...

I wish we get invaded by aliens, but not become their slaves.
That would rock =]

global warming. within the next 50 years.

the sun will explode

I dont think it'll be THAT soon. It's going to be a gradual process. But that's what I've been thinking too.

I can think of a multitude of things that could slowly kill the earth, but these are all theories that could be prevented in the future. There's one theory that is inevitable, and it's related to the sun.

Well, as you all know, the sun is a star. In 7 billion years, it will use up its fuel supply and collapse. But it's important to be familiar with a star's life cycle.

Nebula --> Star --> Red Giant --> Red Dwarf --> White Dwarf --> Supernova --> Neutron Stars --> Black Hole

Our sun is currently at the "star" stage, but in the future it will become a red giant. Red giants swell from 10 to 100 times larger than our sun (or their star stage). Some can even swell up to 1000 times the size of our sun.

So, the sun will begin to expand as it ages, engulfing anything in its path as it gets closer to the earth. As the sun expands, earth's temperature will begin to rise and will eventually become unliveable. Our oceans will evaporate. Carbon dioxide levels will drop, and the process of photosynthesis wouldn't be able to be carried out, and our plants would die. We would die. Our only option then is to move on to another planet where the temperature has, by that time, become more moderate (say, Mars. Jupiter, even), or to perish altogether. Eventually the earth will become victim to the growing mass that is the sun, and any planets we "move" to would be engulfed as well.

So, really, the earth will be destroyed before any sort of explosion from the sun.