I've heard of satellites that go way out in space, like, pass Pluto. Theirs the Pioneer and Pioneer 2 (I think) that go far outer the solar system. But I was wondering, what powers them? Solar energy? How far will it go before it fails, or out of contact from humans?

I was also wondering, why don't we just build one of those satellites and just let it float farther and farther into space with information about us. Just let it float until something happens to it, like it got picked up by E.T. or something. Even if it runs out of power or contact, still let it float with the information permanently on it, so sooner or later, it has to run into aliens.

Yes they are solar powered. They need only a very small amount of power for the onboard communications systems. I believe that pioneer 10 is now out of contact with us due to it's signal being very weak. I think pioneer 11 and the voyagers are still in contact.

As to your second question:
Pioneer plaque - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Pioneer_plaque)
Voyager Golden Record - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Voyager_Golden_Record)

They built those things to last!

Not sure what you mean by "just floating". You need to overcome the gravity of the Earth and Sun... the whole Solar system actually... or the object will simply be towed along by gravity... or, more likely, fall into the Sun or a planet. It's a bit more complex than I can figure out.

Some of the space missions have atomic power rather than solar. The Galileo mission to Jupiter, for example, had a power supply that worked off the radioactive decay of plutonium 238.

I mean just let it keep going and going for a long time until maybe, I don't know, just maybe it reaches the edge of the galaxy and maybe being spotted by an ET

I've heard of satellites that go way out in space, like, pass Pluto. Theirs the Pioneer and Pioneer 2 (i think) that go far outer the solar system. But i was wondering, what powers them? Solar energy? How far will it go before it fails, or out of contact from humans?

I was also wondering, why don't we just build one of those satellites and just let it float farther and farther into space with information about us. Just let it float until something happens to it, like it got picked up by E.T. or something. Even if it runs out of power or contact, still let it float with the information permanently on it, so sooner or later, it has to run into aliens.

Unlike what is suggested in Hollywood science fiction movies, in space what is in motion stays in motion. You only need a (rocket) engine to set direction and speed. Only gravitation or engine power can change objects from that direction and speed.
So while heading out of our solar system, the speed of satelllites is reduced by the gravitational pull of the sun. For satellites intended to leave the solar system either their speed has to be high enough to compensate for the speed loss by the sun, or they have to be equipped with some kind of engine that can compensate for that speed loss (as in case of the ion drive).

Gravitation is also used to speed up satellites : by planning the path of deep space satellites to pass very near by to one or more planets , some of that force is used to increase their speed.

Most satellites are powered by solar energy, some deep space satellites use nuclear energy. That energy is used to power equipment, not satellite speed.

Note : all objects in orbit around the sun are actually falling towards the sun. But while falling, their velocity push them aside, so that they keep falling around the sun, almost always in an eliptical orbit.

As to "floating" satellites : all satellites are provided with their own velocity on top of the speed of earth around the sun. Therefore they are already in orbit around the sun when launched. If a satellite in intended to head outwards, it's orbital speed is increased. If it needs to go inwards, it's orbital speed is decreased. And if it has to stay orbital around the earth it's starting speed is just enough to reach it's intended height and orbit above earth.

i mean just let it keep going and going for a long time until maybe, i don't know, just maybe it reaches the edge of the galaxy and maybe being spotted by an ET
Have you any idea how big the galxy is? It takes light at 300.000 km/sec about 100.000 years to go from one end to the other.
So if a satellite would move at an outward velocity of 1000 km/sec, it would take some 30 Million years to reach the far end of the galaxy. And any communication send by that satellite would take even more time (travel time plus return signal at light speed).
What use would that be? Humanity most probably by that time is no longer existing.

And re. ET : if there are ET's, you will most probably find them in the far arms of the galaxy, just like earth.

Have you any idea how big the galxy is? It takes light at 300.000 km/sec about 100.000 years to go from one end to the other.
So if a satellite would move at an outward velocity of 1000 km/sec, it would take some 30 Million years to reach the far end of the galaxy. And any communication send by that satellite would take even more time (travel time plus return signal at light speed).
What use would that be? Humanity most probably by that time is no longer existing.

And re. ET : if there are ET's, you will most probably find them in the far arms of the galaxy, just like earth.



I know, that is why I ask if there is some kind of energy to that could last millions of years. We don't need to keep in touch with the satellite, all we have to do is put some information of us in the satellite and let it keep on going farther and farther into space. If we exclude the possibility that it might run into a planet or something, then with a few million years of energy to keep going. I think it might as well reach Tau Ceti or farther by a million years...

We don't need to contact the satellite at all. Our goal is for another civilization to find it, somehow read the information we put on it, and have an idea that their not alone. We might be lucky enough for the satellite to run into a advanced civilization and they might know where we are and contact us!

If we exclude the possibility that it might run into a planet or something .... Our goal is for another civilization to find it, somehow read the information we put on it, and have an idea that their not alone.
The chance that the satellite runs into a sun or planet is extremely low.
The galaxy is a relative empty space. The universe is even much more empty.
The chance that somehow some other civilization find it is even millions of times lower.
And what would there be in for us to ship so many expensive satellites out in different directions without any further control from our side ?
All that wasted matter and energy, all that pollution.
Why would we do that, specially as earth is approaching increasing low raw materials levels and energy resources ?
Would it not be more ethical to start taking care instead of all those human beings that have little to eat and lack a roof above their heads in the third world ?


We might be lucky enough for the satellite to run into a advanced civilization and they might know where we are and contact us!
What do you estimate the chance that by (let's say) 20 Million years humanity or life on earth still exists?
And what do we care if they know where we are ? Seems rather dangerous to me.
An advanced civilization (they would be if they can find our small satellite) could also be very dangerous to our existence.

According to Stephen Hawking, we humans will not survive if we don't spread out into space. There are too many accidents which could befall life on one planet.

I agree, if we spread out, then lets say something happens to our planet Earth, we would not be extinct.

So, if we hope to survive in a few million years later, we better spread out into space.

According to Stephen Hawking
Stephen Hawking is a brilliant Professor of Mathematics, and a great expert in cosmology and quantum gravity.
But for contributions to biology and evolution you have to refer to his father, Dr. Frank Hawking.


we humans will not survive if we don't spread out into space.
May be it is better if we do not spread out. At least not yet.
First we should do something against these disasters. Stop the increasing dangers like the Cern or similar projects. Stop with nuclear explosives and fission energy. If we can not do that, we are not ready for space travel.
Note : we are already on a spaceship. It is called earth. And we could be safe here for at least another 4 billion years, unless we ourselves make this planet unhabitable.