Radio signals travel in all directions.
We are not alone?
- Thread starter Brigadier
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The diameter of the universe is still twice its radius, which was the point of my comment. Therefore the previous comment of 6 billion light years being halfway across the universe was flawed.
You seem to be confusing matters somewhat. And there's no need to resort to subterfugal comments such as "only an insecure pedant would argue...."
There's clearly no point in continuing the discussion if it's on a downward slope into personal abuse already.
Irrespective, a diameter is still twice the radius. A radius of 13 gives a diameter of 26. A radius of 6 gives a diameter of 12. So from the center it is fair to say that the circumference of the smaller circle is nearly halfway to the circumference of the larger circle. However, if you're at a point near the larger circumference and cast a circle of radius 6, it would not reach the center, in fact it would be less than halfway to the center, and be a long way off a point beyond the center, in the other half of the circle. You'd be less than a quarter of the way towards a point on the circumference opposite.
And as far as area is concerned, even allowing for the centers of both larger and smaller circles being at the same point, the area covered by the smaller circle is less than a quarter of the larger circle.
Also, the radius of our observable universe is over 46 billion light years, making a diameter of nearly 94 billion light years. And that's only the "bit"that we can see. We have no idea how much further on it goes.
As far as the expanding universe is concerned, it is assumed that everyone is at the center because everything is expanding away from you.Therefore the earth is considered to be at the centre, as far as sending signals is concerned. But also any other planet would, to them, appear to be at the center of the universe. Thus the larger circles would actually be two larger non concentric, overlapping circles. So a smaller circle cast by them or us may not even be within our, or their, larger circle.
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Just as an addition to my previous comments: We've been sending signals into space for about 100 years now. Which means that we've created a sphere in space that contains our signals. That sphere is about 200 light years in diameter.
That's a sphere that is 200 light years diameter in an observable sphere of 94 billion light years diameter, but is known to be bigger but we don't know by how much bigger.
Kinda puts into perspective why we haven't yet detected any other signals, or they ours.
Here's an excellent example with a pictorial illustration only of the Milky Way, partly showing the magnitude of the dimensions involved:
http://www.planetary.org/blogs/emily-lakdawalla/2012/3390.html?referrer=https://www.google.co.uk/
That's a sphere that is 200 light years diameter in an observable sphere of 94 billion light years diameter, but is known to be bigger but we don't know by how much bigger.
Kinda puts into perspective why we haven't yet detected any other signals, or they ours.
Here's an excellent example with a pictorial illustration only of the Milky Way, partly showing the magnitude of the dimensions involved:
http://www.planetary.org/blogs/emily-lakdawalla/2012/3390.html?referrer=https://www.google.co.uk/
Where does the 94 billion figure come from?
Right, well me not understanding has no effect on what may be true, but...
... if the universe is 14 (13.7) billion years old yet some things are 47 billion light years from the centre then some 'faster than the speed of light' journeys must have happened.
I have heard the theory of inflation or expansion but still those things must have moved.
... if the universe is 14 (13.7) billion years old yet some things are 47 billion light years from the centre then some 'faster than the speed of light' journeys must have happened.
I have heard the theory of inflation or expansion but still those things must have moved.
Our understanding of physics at this time though, is that you cannot exceed the speed of light. Light is pure energy. A solid object, or that which has mass could get close, but never exceed.
However, space / time is like a lattice which can be bent and manipulated with appropriate technology, or natural anomalies.
However, space / time is like a lattice which can be bent and manipulated with appropriate technology, or natural anomalies.
In addition to fender's comment, and as I mentioned previously, the law about objects not being able to travel faster than light is a universal law, universal as we understand it. But the universe does not have to follow its own laws and is not an object in that sense.
The universe is expanding,and that expansion rate is accelerating, due to the inertia of the big bang, i.e. hence the "commoving" bit, meaning to move with force or violence.
In addition, that also means that anything near the circumference (if there is one, and we don't know about that either) of the sphere of the expanding universe is moving faster than anything nearer the center.
Which also means that any civilisation sending out signals from near the circumference of the universe (if there is a circumference), those signals may never actually reach us, which is where I previously nearly confused the point about the emitting source of signal from detracting from the speed of the signal. In effect, although the signal may/is travelling at the speed of light, or very nearly, the universe may be/is expanding faster, thus the space between the signal and us increasing. The analogy of fruit loaf rising and expanding is often used, where the whole expands and the space between the fruit within increases.
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In addition, kind of why are we considering this subject now, I would suggest that unless you're actually in that field, you might as well put it into the same conceptual consideration as "is there a God?"
Because, so far we have not detected any other presence. So we can assume that there is no other civilisation within 100 light years of our existence.
Now assume we do detect a signal tomorrow, it would be another 100 light years, assuming we responded immediately, that the alien life form would receive our specific greeting.
Perhaps another couple of hundred light years for us to assess each other's technological capability.
Then we're faced with some ethical, morally sensible decisions. Suppose we are only 100 years more technologically advanced, should we share our technological secrets? Suppose we send the most recent vaccines for the worlds (our world's) worst lethal diseases, as they were 100 years ago. Would they be any use, would they be any danger?
Who, or how would the receiving alien deal, control, manufacture, etc those vaccines.
How would it effect the planetary power?
So we decide we shouldn't share any technological secrets until we understand the planetary power/authority system within that alien world. Perhaps that might take another 1000 light years. That's only 5 to 10 transmissions either way, assuming the alien world is sufficiently advanced to respond in (our) view of honesty.
So, in effect there may be something like 30 generations before we can make an ethically acceptable and morally sensible decision. That's the decision for our great (X 30) grand children. Perhaps I ought to write that out in full: great, great, great, great, great, great, great, great, great, great, great, great, great, great, grand children..........and that's only half way!
So I would suggest, again, that we put the consideration of the existence of alien life in the same conceptual bracket as "is there a God?" for now.
Because, so far we have not detected any other presence. So we can assume that there is no other civilisation within 100 light years of our existence.
Now assume we do detect a signal tomorrow, it would be another 100 light years, assuming we responded immediately, that the alien life form would receive our specific greeting.
Perhaps another couple of hundred light years for us to assess each other's technological capability.
Then we're faced with some ethical, morally sensible decisions. Suppose we are only 100 years more technologically advanced, should we share our technological secrets? Suppose we send the most recent vaccines for the worlds (our world's) worst lethal diseases, as they were 100 years ago. Would they be any use, would they be any danger?
Who, or how would the receiving alien deal, control, manufacture, etc those vaccines.
How would it effect the planetary power?
So we decide we shouldn't share any technological secrets until we understand the planetary power/authority system within that alien world. Perhaps that might take another 1000 light years. That's only 5 to 10 transmissions either way, assuming the alien world is sufficiently advanced to respond in (our) view of honesty.
So, in effect there may be something like 30 generations before we can make an ethically acceptable and morally sensible decision. That's the decision for our great (X 30) grand children. Perhaps I ought to write that out in full: great, great, great, great, great, great, great, great, great, great, great, great, great, great, grand children..........and that's only half way!
So I would suggest, again, that we put the consideration of the existence of alien life in the same conceptual bracket as "is there a God?" for now.
Your comment is based on the assumption that other life forms have developed in some super fast evolutionary period. If you look at when the gases started to cool into solid form, assuming we are expecting other life forms to exist in a solid form, then any other evolution couldn't have started until about 10 to 100 million years after the big bang (in our galaxy, at least).
So a comment about multiple signals circulating for billions of years is a slight exaggeration. Ours have been in circulation for only 100 years. For any other existence to have bettered that means that their evolution has been so mush faster than our own, which I am not rejecting, just not accepting that it could have been in the magnitude of one billion, never mind more than one billion.
Note, some suggest that our signals have only been escaping the atmosphere for about 70 years because LW and MW don't apparently escape the atmosphere, only VHF signals escape.
BTW, similarly, as we have only been transmitting signals for about 70 years, we have only been capable of receiving and recognising signals for about 70 years. Thus it's eminently possible that some signals have been and gone hundred(s), thousands of years ago and we are ignorant of them.
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If we go by our own civilisation, there are a number of explanations as to why we neither see nor hear of aliens:
Radio Signals:
Our TV/radio signals have been emitting for about 100 years. However, what you need to realise is that we only actually emitted signals to space for a few decades. Todays communications systems are much more efficient than in the days of the first Sky At Night episodes, and so our little green men (assuming they have kit advanced enough to piece together a very weakened signal), will see things like I Love Lucy, early Coronation St, Sky At Night when Mr Moore was a young man, and of course Hitler. But today, TV companies do not broadcast adverts for the latest Sky package to ET, as they are unlikely to take it up. And digital TV renders the signal encrypted, so they probably wouldn't even see it, even if it was strong enough. They could maybe detect some later episodes into the 70s, but only Sky At Night would make it worth while, and by then you had some awful TV, so it probably put them off.
There were efforts in the 1960s as part of the Cold War to detect Russian planes etc, by bouncing signals off our atmosphere. These were powerful enough to emit to space, and again, were a short term signal.
And of course, the Arecibo Radio Telescope in Puerto Rico sent signals out to space in 1974. This was the first intended signal, and was about as powerful as we could do at the time, but again, a short term signal in the big scheme of things.
Also, they would not detect many of our radio signals, as they are encrypted. What ET might be using is neutrinos, as they are better at travelling those sort of distances. We will probably do this in time ourselves.
Intersteller Travel
We don't actually see aliens turning up to say hello, why?
Space travel is tricky. Actually no, space travel is really difficult. It takes a lot of energy to get up there, and once you're there, you have to protect against all sorts of nasty things like radiation, loss of breathable air, you have to maintain your biosphere of a space ship, you have to prevent yourself from going mad (there's only so many episodes of I Love Lucy you can watch), and when you're half way out of your own star system, you'll be asking yourself why the smeg are you going anyway? Why wouldn't you just send a robot, and save a heap of resources?
If you're thinking that ET might want to explore/expand their civilisation, you might want to answer why? Looking at our own situation, our own population looks set to stablise at about 12billion(ish). We should be able to feed that many people, and it may even reduce over time. The reason this is happening is birth control.
Birth Control is easier and cheaper than going into space to colonise other worlds (this seems a bit of an understatement, but you'd probably get bored if I wrote "very very very ......... very much easier").
They could send probes of course, and robots. And given, as you say, that a civilisation probably existed billions of years ago (although more like millions), they probably missed us.
Looking for possible alien civilisations in our own little corner of this galaxy, we wouldn't look at the nearest stars, as they are mostly Red Dwarfs (not ideal). There are however, some stars in a group a bit further away, that are like ours, which suggests that our system got flung out of that group. So there may be (or have been , or will be) an alien civilisation there.
Also, aliens in other galaxies probably exist. The current thinking is to look at old galaxies, so (as you said), they would be well advanced.
But they are unlikely to make it over here, owing to the huge distances.
Physical signs of Aliens
There are other ways of detecting alien societies, such as heat and light. With the mass deployment of LED bulbs, the Earth is getting brighter at night. The way things are going, we will be detectable by aliens in the not too distant future, just by our lights. And that doesn't include heat. Even if we stop the Global Warming thing from the greenhouse effect, if our economy continues to grow, we will heat the Earth from direct waste heat, owing to the huge amount of energy we would consume. This is because of the relationship between the economy and energy consumption.
Its thought that in about 200 years(ish), we will see a detectable rise of a few degrees from this effect globally. We see it currently as urban heat islands, but this will only increase as we develop. If we continue to grow economically at current rates, the oceans will boil in 400 years time (this won't happen in reality of course, but serves to illustrate the issue).
So when we are sufficiently developed, aliens could detect both our heat and light from many light years away. They can also have a rough idea of what organisms are in our atmosphere, and the basic composition of gases. But won't see us unless we find a way of sending signals for a long time in the right way that they can detect.
If our aliens feel the need to grow economically beyond what their planet can support (which would be silly), they may feel the need to build a Dyson Sphere. This would be easy to detect (although very difficult to build), as again, it would emit waste heat, but at a scale that could be detected from a huge distance. But remember the comment about space travel and birth control.
So assuming our aliens have comparable gravity wells, and the ability to do the whole birth control thing, and the likelihood that they will have some equivalent of I Love Lucy, going by our own experience, we can assume that they sent signals, but basic radio signals would only have lasted for a short time (relatively speaking). Any signals that they do send would probably be something other than basic radio signals, such as neutrinos, or some kind of gravity wave, or other system we hadn't considered. These would have to be emitted for a huge amount of time for us to pick them up, otherwise we would miss them
This also applies for robots/probes. They could send out a million probes, but its unlikely we would come across one, as there are so many systems they could send them to. We could look for signs of energy emissions for ships, or asteroid mining etc, but these would be close by systems.
Of course I do hope we will one day see some evidence of aliens, but we must remain sceptical (if for nothing else, our sanity).
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Love it!!
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