Assuming there are actually space aliens, there are a lot of factors that make the probability of contact with these aliens very low.
First, the universe is a vast, vast place... it can take millions and billions of years for even a photon of light -- the fastest-moving particle in existence -- to reach many places. Even if there is alien life out there, even if they sent a message now, the Earth would be long gone by the time it reached us.
Second, it's possible that whatever life is out there has not advanced far enough to contact us. It could be single-celled, etc.
Third, it is extraordinarily difficult for us to find life in the universe without going out and trying to find it (which is impractical and, currently, impossible beyond a very short distance from Earth). Whatever intelligent life is out there is probably under the same limitations.
Tell her that, if there are any space aliens, then they are probably a very, very long way away. So they are having a very hard time getting to us, just like we are having a very hard time getting to them. Chances are, they will send us messages with radio or light long, long before they can actually make the journey. It's like being very easy to phone someone on the other side of the world, but very, very hard to get there by walking... until someone invents the ship and the car, or better yet, the airplane. For going all the way to other stars, we have not yet invented the right type of airplane.
You should probably also tell her that all those ideas about aliens trying to sneak onto our planet in spaceships with flashing lights are all fake. If aliens are here and they want us to know, then they would tell us. If they don't want us to know, then they wouldn't be flying around in spaceships with lights so bright that people can actually look upward and see them.
They are soooo far away that they probably can't travel to us even if they know about us. Even if they could go very fast, they might not be able to find us. It's like 3 people on the entire empty earth trying to find each other. It's actually harder than that, but that's as close as i can get for a 7 yr old.
Well aliens matter is still being discussed with intelligence and if aliens really exist and are always watching our dailly activities especially science wich seems they are the best ever, may be if we pose no threat to them they will show up. Besides Machael Jackson is a volunteer who is about to build their airport.
Not an easy one to answer, eh? Well, let's start from the beginning.
First things first, the question presupposes that extraterrestrial beings have not visited the Earth. In the traditional sense of what that means, I would tend to agree with her. It is, however, worth pointing out that some very serious scientists have postulated that life on Earth may have an extraterrestrial origin. If that is the case, then in a very real sense, we humans, along with bacteria, cauliflower, sheep, and every other living thing on the planet may be "space aliens". Regardless, that's not a very satisfying answer to the question.
So, how about our more conventional idea of little green men (or tall gray ones) in spaceships? Well, let's next try to determine whether there might be any out there. The astrophysicist Frank Drake came up with an equation (now cleverly known as the Drake Equation) to roughly calculate the incidence of life, and intelligent life in particular, in the Milky Way Galaxy, to determine the approximate likelihood of us being able to communicate with a distant civilization.
The Drake equation is:
N = (number of stars) * (percentage of stars that have planets) * (number of planets per star that can support life) * (percentage of planets that can support life where life actually starts) * (percentage of planets that have life on them that get intelligent life) * (percentage of planets that have intelligent life that can communicate -- or maybe master interstellar travel, in this case) * (fraction of a planet's lifetime where intelligent, communicating species can exist)
Depending upon who you ask and what estimates you end up using, there might be something on the order of 2000 other intelligent civilizations currently inhabiting the Milky Way along with us, but the margin of error on that is obviously quite large.
Does that sound like a lot? Well, let's talk about the scale of the Milky Way. First off, there are about 200,000,000,000 stars in the galaxy (again, depending upon who you ask). Most of those stars are clustered in a central bulge of the galaxy with several arms of stars spiraling out. Our Sun is about 28,000 light years from the central bulge. A light year is a unit of distance equivalent to the distance a photon of light can travel in a year. Given that light travels at a constant 186,000 miles per second, a light year is a REALLY long way.
The nearest star to us is called Proxima Centauri, and is approximately 4.2 light years from us. Thus, if you were to hop on a beam of light leaving the Earth today, you wouldn't get there until late in 2010. Nevermind the fact that you can't ride light. Given the technologies currently known to humans, it would require almost 70,000 years for us to get to Proxima Centauri.
And there aren't a whole lot of other stars that are terribly close to us. There are only 8 stars within 10 light years of us, and given our earlier calculations from the Drake Equation, it looks extremely improbable that there's intelligent life nearby.
So the question becomes one of the difficulty of traveling great distances. Now, is it possible that other superintelligent species have mastered relatively rapid interstellar travel? Sure. Similarly, it is possible that their lifespans might be sufficiently long to make a few centuries of travel be a reasonable thing to do with one's life. Impossible to say for sure, but seems more than a little unlikely.
Um, you have explained to her that there is no credible proof that space aliens have ever visited us...and that since space is so incredibly vast that even if they were out there somewhere, it's unlikely they could visit us?
conrad D, before you ensure yourself that "there aint none"
consider this: if the universe is truely infinite, then it is a logical certainty that every possible solution is out there. if you roll a dice with 1,000 numbers on it an infinite amount of times, you will eventually get every number. so if the universe goes on forever then it is certain that every possible solution is out there, even a universe the exect same as ours. even a universe like ours but where earth is one square inch smaller. or a universe like ours but earth is one square inch smaller and you have red hair. even one that is exactly the same, except you are playing hockey right now. and one that is the same but you are playing hockey while speaking french. do you understand where im going with this? infinite means all possibilities must be covered. not only in existence, but in an incalculable amount. if the universe is infinite. then every possible solution must show up an infinite amount of times. even aliens. in every possible shape and form.
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Verified answer
Assuming there are actually space aliens, there are a lot of factors that make the probability of contact with these aliens very low.
First, the universe is a vast, vast place... it can take millions and billions of years for even a photon of light -- the fastest-moving particle in existence -- to reach many places. Even if there is alien life out there, even if they sent a message now, the Earth would be long gone by the time it reached us.
Second, it's possible that whatever life is out there has not advanced far enough to contact us. It could be single-celled, etc.
Third, it is extraordinarily difficult for us to find life in the universe without going out and trying to find it (which is impractical and, currently, impossible beyond a very short distance from Earth). Whatever intelligent life is out there is probably under the same limitations.
Tell her that, if there are any space aliens, then they are probably a very, very long way away. So they are having a very hard time getting to us, just like we are having a very hard time getting to them. Chances are, they will send us messages with radio or light long, long before they can actually make the journey. It's like being very easy to phone someone on the other side of the world, but very, very hard to get there by walking... until someone invents the ship and the car, or better yet, the airplane. For going all the way to other stars, we have not yet invented the right type of airplane.
You should probably also tell her that all those ideas about aliens trying to sneak onto our planet in spaceships with flashing lights are all fake. If aliens are here and they want us to know, then they would tell us. If they don't want us to know, then they wouldn't be flying around in spaceships with lights so bright that people can actually look upward and see them.
They are soooo far away that they probably can't travel to us even if they know about us. Even if they could go very fast, they might not be able to find us. It's like 3 people on the entire empty earth trying to find each other. It's actually harder than that, but that's as close as i can get for a 7 yr old.
Well aliens matter is still being discussed with intelligence and if aliens really exist and are always watching our dailly activities especially science wich seems they are the best ever, may be if we pose no threat to them they will show up. Besides Machael Jackson is a volunteer who is about to build their airport.
Not an easy one to answer, eh? Well, let's start from the beginning.
First things first, the question presupposes that extraterrestrial beings have not visited the Earth. In the traditional sense of what that means, I would tend to agree with her. It is, however, worth pointing out that some very serious scientists have postulated that life on Earth may have an extraterrestrial origin. If that is the case, then in a very real sense, we humans, along with bacteria, cauliflower, sheep, and every other living thing on the planet may be "space aliens". Regardless, that's not a very satisfying answer to the question.
So, how about our more conventional idea of little green men (or tall gray ones) in spaceships? Well, let's next try to determine whether there might be any out there. The astrophysicist Frank Drake came up with an equation (now cleverly known as the Drake Equation) to roughly calculate the incidence of life, and intelligent life in particular, in the Milky Way Galaxy, to determine the approximate likelihood of us being able to communicate with a distant civilization.
The Drake equation is:
N = (number of stars) * (percentage of stars that have planets) * (number of planets per star that can support life) * (percentage of planets that can support life where life actually starts) * (percentage of planets that have life on them that get intelligent life) * (percentage of planets that have intelligent life that can communicate -- or maybe master interstellar travel, in this case) * (fraction of a planet's lifetime where intelligent, communicating species can exist)
Depending upon who you ask and what estimates you end up using, there might be something on the order of 2000 other intelligent civilizations currently inhabiting the Milky Way along with us, but the margin of error on that is obviously quite large.
Does that sound like a lot? Well, let's talk about the scale of the Milky Way. First off, there are about 200,000,000,000 stars in the galaxy (again, depending upon who you ask). Most of those stars are clustered in a central bulge of the galaxy with several arms of stars spiraling out. Our Sun is about 28,000 light years from the central bulge. A light year is a unit of distance equivalent to the distance a photon of light can travel in a year. Given that light travels at a constant 186,000 miles per second, a light year is a REALLY long way.
The nearest star to us is called Proxima Centauri, and is approximately 4.2 light years from us. Thus, if you were to hop on a beam of light leaving the Earth today, you wouldn't get there until late in 2010. Nevermind the fact that you can't ride light. Given the technologies currently known to humans, it would require almost 70,000 years for us to get to Proxima Centauri.
And there aren't a whole lot of other stars that are terribly close to us. There are only 8 stars within 10 light years of us, and given our earlier calculations from the Drake Equation, it looks extremely improbable that there's intelligent life nearby.
So the question becomes one of the difficulty of traveling great distances. Now, is it possible that other superintelligent species have mastered relatively rapid interstellar travel? Sure. Similarly, it is possible that their lifespans might be sufficiently long to make a few centuries of travel be a reasonable thing to do with one's life. Impossible to say for sure, but seems more than a little unlikely.
Um, you have explained to her that there is no credible proof that space aliens have ever visited us...and that since space is so incredibly vast that even if they were out there somewhere, it's unlikely they could visit us?
conrad D, before you ensure yourself that "there aint none"
consider this: if the universe is truely infinite, then it is a logical certainty that every possible solution is out there. if you roll a dice with 1,000 numbers on it an infinite amount of times, you will eventually get every number. so if the universe goes on forever then it is certain that every possible solution is out there, even a universe the exect same as ours. even a universe like ours but where earth is one square inch smaller. or a universe like ours but earth is one square inch smaller and you have red hair. even one that is exactly the same, except you are playing hockey right now. and one that is the same but you are playing hockey while speaking french. do you understand where im going with this? infinite means all possibilities must be covered. not only in existence, but in an incalculable amount. if the universe is infinite. then every possible solution must show up an infinite amount of times. even aliens. in every possible shape and form.
because we could be the astronomical equvalent of either...
1) Alice springs http://en.wikipedia.org/wiki/Alice_Springs
2) An ant hill in the middle of a extremely big desert
3) We've only been sending radio signals out for 70yrs so they might not be within the 70 light yr ranage to pick us up or they may not b listening.
4) they might have proceedures not to get involved
If there was intelligent life that knew about us, they already would have contacted us. If aliens exist, they probably dont care to communicate.
Think about bears communicating w/penguins.
Cuz there aint none (numba 1) and numba two, there might be some bacteria out there that have no desire to visit us (numba 2)