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spoerl78
2009-Jan-16, 12:54 PM
Hi there,

does anybody know what the chance is,
for an extraterrestial probe sent to us from somewhere,
crossing the OortCloud, Kuiper-Belt and all
the Giants, to reach us?

Peter B
2009-Jan-16, 02:16 PM
Hi there,

does anybody know what the chance is,
for an extraterrestial probe sent to us from somewhere,
crossing the OortCloud, Kuiper-Belt and all
the Giants, to reach us?

G'day Spoerl78, and welcome to the BAUT Forum.

I don't think it's possible to calculate the chance, for one very simple reason - we don't know how many civilisations there are out there beyond our Solar System. After all, the more civilisations there are, the greater the chance that some of them would be sending probes in our direction. If there was only one other civilisation in our galaxy, then whatever the chance is that a probe is headed our way is going to be different from the chance would be if there were a million other civilisations in our galaxy.

Swift
2009-Jan-16, 02:52 PM
If they make it to our solar system (and as Peter B said, we don't know about the odds of that) there would be no particular problem crossing the Oort Cloud, the Kuiper Belt, or getting pass the gas giant planets, if that is what you are asking.

eburacum45
2009-Jan-16, 03:11 PM
The objects in the Oort Cloud are very very thinly spread, and the objects in the Kuiper belt are nearly as far apart; you could send trillions of probes in and out of our system and none of them would hit anything (unless you were very unlucky.)

JustAFriend
2009-Jan-16, 03:14 PM
The animations you see on movies and TV make it look like everything is grinding against each other. In fact it's 99.9999999999999999% empty space out there....

mugaliens
2009-Jan-16, 06:18 PM
Hi there,

does anybody know what the chance is,
for an extraterrestial probe sent to us from somewhere,
crossing the OortCloud, Kuiper-Belt and all
the Giants, to reach us?

Are you asking what the liklihood is of a probe getting through all that clutter?

If so, it's about 99.9999999999999%, as that "clutter," while numerous, is extremely spread out. A single handful of sand chucked outside a spacecraft in orbit around the Earth would be very spread out over time, but would still be much more dense.

spoerl78
2009-Jan-16, 07:50 PM
Hi,

I thought maybe Jupiter could be problem,
because it was/is for asteriods.
I just wondered, if more advanced civilisations
are out there and they already found us, because
of better equipment, maybe they already sent probes
which are now hanging out in our solar system,
like asteriods or are caught by Jupiter.

And I think they would do, because I think
we will do it in the future.

Sounds a bit like "Odyssee 2001" ;-)

novaderrik
2009-Jan-16, 08:19 PM
any probe coming in from outside the solar system would be going too fast to be captured by Jupiter- or even the sun.. at best, it would loop around the sun and shoot right back out the other side of the solar system and keep moving on.
unless, of course, it had some sort of means to slow itself down a bunch.

pzkpfw
2009-Jan-16, 08:20 PM
Don't be like Khan. Think 3D. The belts (and orbits) are not shells.

spoerl78
2009-Jan-16, 08:54 PM
Yeah I agree now that the belts are
not a problem. Lets just wait and see what we'll
find hanging out there.
Maybe join WETI meanwhile.

RalofTyr
2009-Jan-16, 09:05 PM
I'm sure an alien probe had or will pass through our solar system. If it had, it found no worlds with advanced life on them, just microbes. If it will, it will find no advanced life forms, just a world with a super thick atmosphere and a lot of ancient ruined space junk floating around the system because the first probe came 4.3BYA and the next one will be 1.2BY in the future.

Secondly, one such probe probably won't need to travel through the Oort cloud. The probe can come from any direction, from North or the South of the Sun's solar pole. The probe will have to slow down considerable and make several orbits around the sun until it reached our orbital plane.

Swift
2009-Jan-16, 10:10 PM
any probe coming in from outside the solar system would be going too fast to be captured by Jupiter- or even the sun.. at best, it would loop around the sun and shoot right back out the other side of the solar system and keep moving on.
unless, of course, it had some sort of means to slow itself down a bunch.
And if they have a means to slow down, they have a means to maneuver, so they can still avoid Jupiter.

mugaliens
2009-Jan-17, 12:51 AM
Secondly, one such probe probably won't need to travel through the Oort cloud. The probe can come from any direction, from North or the South of the Sun's solar pole. The probe will have to slow down considerable and make several orbits around the sun until it reached our orbital plane.

How sure are you it won't vector in on our EM transmissions only to return to it's original course long before it gets here because those transmissions, any transmissions of any kind (subspace, quantum separation, etc..)...

...have stopped?

RalofTyr
2009-Jan-17, 01:08 AM
How sure are you it won't vector in on our EM transmissions only to return to it's original course long before it gets here because those transmissions, any transmissions of any kind (subspace, quantum separation, etc..)...

...have stopped?

I'm not sure what you're asking.

What does EM transmissions have to do with the physics of gaining a trajectory that matches with the orbital plane of our system?

astromark
2009-Jan-17, 02:29 AM
I have tried to understand your question but find the lac of logic astounding.
What are the odds... as has been said, we have no idea.
Could it happen ? yes.
Has it happened yet ? No. ,or if it has the proof is not apparent.
Any inter stellar vehicle could find Earth and if intelligently controlled even enter a stable Earth orbit. After a orbit or two a landing would not be impossible. Getting off again is easy enough requiring only surfactant thrust available to exceed escape velocity. Assuming energy for such is availabe... how far do we go with this ? Would the gas giants get in the way ? No. They could actually help the incoming craft slow by using the slingshot reverse gravity to slow the velocity.

Veeger
2009-Jan-17, 03:12 AM
While there are many different ways to speculate and calculate the odds, it is pretty safe to say under any scenario there is very little chance we will ever be found. Check out the Drake equation. (http://en.wikipedia.org/wiki/Drake_equation)

spoerl78
2009-Jan-17, 08:52 AM
But this would also mean
that we will never detect any
aliens and I don't believe that.
Given enough time they will show up.
But that just what i think.

BetaDust
2009-Jan-17, 09:20 AM
Hi spoerl78, Welcome to BAUT!


But this would also mean
that we will never detect any
aliens

No. It means the chances are verry verry low.


and I don't believe that.

Why?


Given enough time they will show up.

Sure, but will we humans still exist then? Space is verry, verry big.


--Dennis

spoerl78
2009-Jan-17, 09:28 AM
Hi spoerl78, Welcome to BAUT!



No. It means the chances are verry verry low.



Why?



Sure, but will we humans still exist then? Space is verry, verry big.


--Dennis

I think chances are high enough.

Why? Pete wanted it that way.

Let's have a cup of coffee and see...

BetaDust
2009-Jan-17, 02:45 PM
Let's have a cup of coffee and see...

Better make that a verry big cup of coffee.

Veeger
2009-Jan-17, 02:47 PM
You asked in the OP what are the chances. While we are not sure if you were asking "what is the chance ET can fly through the kuiper belt" or "what is the chance ET can find us"? We have answered the first possible question, the chance of ET surviving a flight through the Kuiper belt is very good. The odds he can find us are slim to none. If you choose to believe otherwise, it is your perogative.
I am enjoying my coffee this morning, thank you.

spoerl78
2009-Jan-17, 04:04 PM
I thought it would be more of a problem to get through that,
but now I'm convinced that this is not the case.
Lets see what we will find among all the chunks out there
in our solar system.

So now I open up a *verry* big bottle of beer and watch the sky
for ET's probe...

Veeger
2009-Jan-17, 05:35 PM
Cheers

astromark
2009-Jan-18, 03:17 AM
twas it me ? not this time.... Good quality beer poured over ice.... and a very ( verry ) odd way of spelling., but still a good idea. While we wait to see if some advanced civilizations prob is ever going to find out who is making all that noise...
We scan the skies looking and listening and as yet nothing. We must except that that is probably a good thing. Being found could be a very bad day.:(

Van Rijn
2009-Jan-18, 03:48 AM
We have answered the first possible question, the chance of ET surviving a flight through the Kuiper belt is very good.


Agreed. That's pretty straightforward.



The odds he can find us are slim to none.


But I don't know how you can decide that without making a lot of assumptions. Who is "he" and under what conditions is it difficult for him to find us?

Peter B
2009-Jan-18, 05:53 AM
I think chances are high enough.

Why? Pete wanted it that way.

Let's have a cup of coffee and see...

Remember, the universe is not obliged to meet our expectations.

Another way of looking at it is this: life in the universe is either common or it isn't. If it isn't common, there's a chance that we're alone in this universe, in which case no one will be coming to visit. But even if life is common, some life form had to be the first to arise somewhere in the universe, and they would wonder where all the life was in the universe. That could be us too.

mugaliens
2009-Jan-18, 06:52 PM
Remember, the universe is not obliged to meet our expectations.

Another way of looking at it is this: life in the universe is either common or it isn't. If it isn't common, there's a chance that we're alone in this universe, in which case no one will be coming to visit. But even if life is common, some life form had to be the first to arise somewhere in the universe, and they would wonder where all the life was in the universe. That could be us too.

Given the universe is (probably) infinitely large, I look at it in terms of limits:

1. The probability that we're alone in the universe: infinitely small

2. The probability that we're the first to arise as sentient life wondering where all the life was in the universe: infinitely small

Given these two (likely) probabilities, the probability of of us having visitors is a function of them both. The problem is, we don't know what that function looks like, as we have absolutely no data on the density of life as it's distributed throughout the universe. It might be every solar system (unlikely, or we'd know by now!). It might be once per galaxy (also, unlikely, as if life does originate spontaneously, what happened here on Earth cannot be a fluke and would have happened at one point or another on millions of planets throughout the Milky Way).

Without good, clear data on the density distribution, we cannot calculate when "they" are likely to come visit. For all we know, "they" may have their own version of the Prime Directive (http://en.wikipedia.org/wiki/Prime_Directive)and we'll remain in the dark until we develop our own warp drive (or equivalent).

Veeger
2009-Jan-18, 09:02 PM
For many years previously the Soviets and later SETI, conducted large scale sweeps of the sky searching for signs of intelligent signals. Eventually officials at SETI realized this kind of sweeping search was pointless. The current project is narrowed to about a 1000 local stars which after nearly forty years of searching have revealed nothing (although some nice technologies are being developed). The driving reason behind a limited search: the resolution of the largest radio telescopes is less than one arcminute. This means a huge amount of sky would need to be searched and we need to hope that any life that is out there is capable of producing extremely powerful electromagnetic signals that are distinguishable from noise.

Turning the problem around, ET faces the same problems. The search area is huge and our signals are not very powerful so difficult to detect at interstellar distances. Perhaps impossible to detect. Therefore either ET needs to be very close or he needs to detect us some other way. So we must assume that if he finds some way to detect something unusual on our planet circulating a normal star, he must recognize it as something intelligent. Afterward we must consider whether ET has the technology and the will to launch a massive project to visit us which is the premise of the OP.

We can extrapolate the odds of ET finding us by looking at our own ability of detect life on distant planets. So far we can not detect life less intelligent than us nor of equal or greater intelligence. It is the same for ET.

It has been convincingly argued that SETI and the entire search for ET is not science, it is religion. I tend to agree.

Van Rijn
2009-Jan-19, 09:54 AM
Turning the problem around, ET faces the same problems. The search area is huge and our signals are not very powerful so difficult to detect at interstellar distances. Perhaps impossible to detect.


It depends on the signal and how good the radio telescopes are. And, some radar transmissions are actually pretty strong. Probably the biggest limitation on a hypothetical ET picking up radio from Earth is simply the time that it would take for the signal to reach them - we haven't been doing it for long.



Therefore either ET needs to be very close or he needs to detect us some other way. So we must assume that if he finds some way to detect something unusual on our planet circulating a normal star, he must recognize it as something intelligent.


Right. Large space based optical and infrared telescopes in theory should be able to detect life at interstellar distances, if there are worlds similar to Earth. It's significantly more difficult, but a large enough telescope array might be able to detect signs of the type of civilizations that have existed on Earth for a few thousand years.

So, it is possible, within known physics, that a hypothetical ET could have detected us (Earth life, possibly Earth civilization).



Afterward we must consider whether ET has the technology and the will to launch a massive project to visit us which is the premise of the OP.


And I'd agree that it would be extremely unlikely, even if one assumed an ET civilization was watching this system, that a probe would enter the system right now.



We can extrapolate the odds of ET finding us by looking at our own ability of detect life on distant planets. So far we can not detect life less intelligent than us nor of equal or greater intelligence. It is the same for ET.


There's a difference between what is possible, and what we have the hardware to do right now.


It has been convincingly argued that SETI and the entire search for ET is not science, it is religion. I tend to agree.

If someone insists that there must be an ET that will be found with SETI, I would agree that it is an essentially religious point of view. But, if someone insists that SETI must be pointless because ET can't possibly exist, I would say that's also an essentially religious point of view.

mugaliens
2009-Jan-20, 07:20 PM
Interesting. How sure are we that quasars or pulsars aren't the intergalactic equivalent of whalesong amongst incredibly advanced species?