Cellular Phone Spectra and Earth's SETI Invisibility

astrobio writes: "How long will the Earth's technology be detectable to other worlds? From an article today by the Chairman of the SETI Institute: 'Not long, with shared transmission spectra. To transmit ever-increasing amounts of information, portions of the spectrum must be shared. This is only possible if signal strengths are reduced so that transmissions on the same frequency do not interfere with one another. The textbook example of this paradigm is the cellular phone system. This signal reduction means we are well on our way to becoming invisible.'"

Re:Our signals may not be visible

[TRACK-YOUR-POSITION]

Geez no wonder I can't see the light from other stars anymore! All this time I was blaming pollutants.

Re:Our signals may not be visible

[ShavenYak]

The point of this is that a signal may only propagate outwards until the total mass behind it exceeds a critical value (the location of this is called the "event horizon" in an analogy to black holes). At that point its deflection will equal more than 90 degrees...i.e. it will not go any farther from its point of origin.

Obviously this limit, if it exists, is more than several billion light years, otherwise we wouldn't be able to see galaxies that far away. So I don't think this is going to affect SETI too much.

Good.

[Violet Null]

Maybe now the three-eyed, ten-tongued aliens of Vega will be able to get some rest once we turn the noise down.

Bad intergalactic neighbors, that's what we are.

This is not a new theory

[eclectric]

SETI researchers have known this for a good while now. As we move from broadcast television and radio to digital formats, we will essentially be reducing and eventually completely shutting off runaway transmissions out into the cosmos. This is actually included in probability calculations in the success of SETI: you only have about 200 years in a given civilization in which to find them through their leftover radiation... after that time frame, there are certain signals (radio telescopes, for instance) that are detectable, but which don't travel in every direction.

One of the goals/projects of SETI is to keep transmitting data that appears to be from intelligent creatures... Prime numbers in binary is one proposed method. A simple SOS is even possible... anything that would look nonrandom.

We Should Build a Directional Ant.

[capt.Hij]

The examples of space going radiation given in the article are all point sources. The power per area for such sources should be exceedingly small for those sources within a relatively small distance. Perhaps we need to build directional antenae to make sure that we can be heard. Of course given the nature of directional antenae we should make sure that we build millions of them to make sure that they are pointing in the correct direction. (The down side of Fermi's dilema!)

What we need is a screensaver that will turn a monitor into a directional antena. Then everybody can then turn their monitor towards the heavens when their computers are not at work and let the screen saver then broadcast a message. This would be much more effective and much cheaper. This way we can do the broadcasting for a change and let those free-loading, beer swilling aliens take a turn trying to decode noise from space for a change. Why should we do all the work?

Re:Great tech, but why from SETI?

[mberman]

SETI isn't proposing that we should use tech that doesn't broadcast as much as in the past. It's reporting that we already are. It's an unavoidable consequence of progress in radio communication. Just because SETI talks about it doesn't mean they think it's contributing to their cause.

Invisible?

[Rhombus]

Perhaps this is why we don't hear any radio transmissions from alien civilizations...by the time we thought to start listening, they've already refined their communications to the point where they're no longer detectable by us.

Sounds like it could be the death knell for SETI...

Re:Invisible?

[ericman31]

Since, according to our current understanding, the Universe is between 10 and 15 billion years old, it also follows that the radius of the Universe (assuming it's spherical or circular) is between 10 and 15 billion light years. While some ET civilizations may no longer be detectable by us because of the change in transmissions, others will still be detectable. Why? Because they are far enough away that their transmissions have not yet reached us.

Remember those transmissions occurred in the past. They take years (or even millions of years) to reach us. Looking at the stars is looking into a time machine. We are not seeing the stars as they are now, but as they were in the past.

Re:Invisible?

[lugonn]

Hmmm...I think the current universe models are wrong. I don't believe the universe ever had a beginning 'time' which would give it an age value.

We don't understand gravity/time in relation to each other well enough, to label the universe within a paradigm we can understand, such as age.

I believe time accelerates the closer you get toward the center of the universe, and gets slower as you move away from the center.

I say this becuase time is measured by how particles move relative to eachother. If those particles accelerated/deccelerated relative to eachother, then time would never appear to change from the particles perspective. However, if you could determine the particles distance/velocity degridation from the center of the universe, then you would be able to tell the particles true age.

But, the universe itself has no age, since the particles that make it up DO NOT move relative to each other over a given distance.

Energetic particles leave the center of the universe and travel out. Over distance they lose momentum, and their unique quantum spin. The particle then becomes 'Dark', it cannot directly interact with the quantum universe anymore. But since it does occupy mass, it now begins to accrete back to the center of the universe to start the process all over again.

This whole process in analogous to phase shifting in electric currents. Each cycle reaches an almost infinite value before it repeats.

Re:Invisible? Super Strings for Dummies.

[lugonn]

Sure, sure, since you're so much smarter than every cosmologist in the world who says that the universe has a finite age.

They laughed at Gallileo when he said an orange and a cannon ball would fall at the same rate. Besides I said "I think this" not "I know this". I am entitled to my own observations. I was trying to engage you on the subject, not start a flame war...elitist.

Time is not measured by how particles move relative to each other. If everything is stationary time continues to march on.

Huh? If our galaxy and all the matter in it stopped moving, so would time. We would have no way to measure it, at least that is what relativity states. The photons we rely on for reference would not be moving, neither would we. Relativity is the same theory they use to come up with the age of the universe model you espouse, it's not wrong per-se, just incomplete. Time is a human concept, there is no time/space. Time is an effect of gravity and space interracting, and is wildly subjective. It changes depending on were you are in the universe.

Also, you're assuming the universe has a preferred centre. It doesn't.

What's the big bang then? They gauge the current estimate of the universe's age by it's rate of expansion from a single point. I make other assumtions, but not on this point.

Also, if "energetic particles leave the center of the universe and travel out", how does this mesh with "...the particles that make [the universe] up DO NOT move relative to each other..."? Please reconcile this.

As the particle moves away from the center, it moves slower. Thus, the particles relative movement is slower at the edges than in the center. I'm basically saying that in our layer of the expanding explosion known as the universe, light moves slower than it does closer to the center. Thus time seems to move faster.

Also, how do particles lose quantum spin? Can you explain this to me, and correlate it with the Standard Model that has been hammered out through years of extensive observations, calculations, and theories and show absolutely no support for this hypothesis?

What standard model are you talking about? One doesn't exist. Super String theory seeks to find out how sub-atomic particles exist without mass. They could be tiny knots were several dimesions meet. When 1 or more of these dimensions become unentangled, the particle ceases to interact in 3 dimensions. It is not quantum anymore, not in several places at once.

I think you should leave the thinking up to people who actually can. Don't pretend to know something when you so clearly do not.

I didn't 'think' this up. Read 'The Elegant Universe' by Brian Greene (NYT bestseller!). He is one of leading physicists of our time. Super string theory upsets assumtions made in relativity, which is why it is unpopular with the old egg-heads who have invested their lives into an incomplete observation. Einstein had no idea that sub-atomic particles existed (like quarks). So he had to make up shit to fill the holes in his theories. He even admitted relativity wasn't a complete explaination.

You're right, we don't understand gravity and time well enough. However, you understand it even less (to the point, one might add, where you don't understand it at all), so you're the least qualified to say anything even remotely resembling intelligent about it.

Seems your definition of intelligence precludes reading books, and comes from TV. I've cited my sources, you've cited none. See if you can pull your ego and your common sense apart and get back to me with rational logic.

Re:Invisible? Super Strings for Dummies.

[Anonymous Coward]

Huh? If our galaxy and all the matter in it stopped moving, so would time. We would have no way to measure it, at least that is what relativity states.

The lack of a way to measure something does not mean it does not exist. Do you think that because people could not measure the mass of an electron in the 1600s means it didn't exist then?

Time is a human concept, there is no time/space.

So you're saying that if humans did not exist, there would be no time?

What's the big bang then? They gauge the current estimate of the universe's age by it's rate of expansion from a single point. I make other assumtions, but not on this point.

It's called the cosmological principle. There is no preferred centre of the universe. The Big Bang happened everywhere in the universe, not at one point in the universe.

Think of the "raisin bread" model of the universe. Suppose you're a raisin in an expanding loaf of bread. According to you, all the other raisins are moving away at a speed proportional to their distance from you. From this you would assume that you're at the centre of the loaf. However, if your friend is on another raisin, he too sees all the other raisins (including the one you're on) moving away from him at a speed proportional to their distance from him. From this he would assume that he's at the centre of the loaf. There is no preferred raisin.

As the particle moves away from the center, it moves slower. Thus, the particles relative movement is slower at the edges than in the center. I'm basically saying that in our layer of the expanding explosion known as the universe, light moves slower than it does closer to the center. Thus time seems to move faster.

Proof, please. Light always moves at the same speed.

What standard model are you talking about? One doesn't exist.

The Standard Model. The Standard Model is the name given to the current theory of fundamental particles and how they interact. Nowhere in this model do particles lose spin over time. They're not like small tops in space, they have discrete, quantized spin.

Seems your definition of intelligence precludes reading books, and comes from TV. I've cited my sources, you've cited none. See if you can pull your ego and your common sense apart and get back to me with rational logic.

My intelligence comes from reading books and lecture notes, including (but not limited to) those I used when I obtained my degree in physics and astronomy.

You seem to have this idea that the universe is exploding into space. That could not be further from the truth. The universe is not expanding into space, it is space expanding. There's a huge difference there, and a very profound one. One of the consequences of the expanding universe is that there is no physical edge of the universe. If you flew in a space-ship you could not reach the physical edge of the universe because it does not exist.

I only have two links to suggest to you because I am too busy at the moment (busy working at a major astronomical observatory).

http://calspace.ucsd.edu/edout/calforum/universe/
http://www2.slac.stanford.edu/vvc/theory/model.htm l

And yes, I am the same AC as above.

Re:Invisible? Invarience 'n stuff

[lugonn]

The lack of a way to measure something does not mean it does not exist.

I know. But my point was, time is an arbitrary concept. It has different values depending on your motion through space relative to whatever you want to measure time from. So therefore, the universe has no age. It just always was, and always will be. Unlocking the secrets of dark matter will show that the universe recycles space and motion, there is no time.

>Time is a human concept, there is no
>time/space.
So you're saying that if humans did not exist, there would be no time?

No, I'm saying that time is a way humans measure motion through the universe. It is not constant however, and makes a lousy yardstick. Einstein says that photons move through space but not time, Which is why I think he was wrong to conclude that time must be a separate dimension.

It's called the cosmological principle. There is no preferred centre of the universe. The Big Bang happened everywhere in the universe, not at one point in the universe. Think of the "raisin bread" model of the universe.

Right, space occupies different distances depending how fast you move through it...special relativity.

From our point of view, your statment makes sense. However, the raisins have no idea that they are actually moving through the bread, from they're point of view everything else is moving away from them, and they are still. They have no way to tell that everything around them is moving in one direction, away from a singular point, (think spheres expanding, not planer motion).

>..light moves slower..
Proof, please. Light always moves at the same speed.

Lets say some bubbles in a fishtank rise at a constant rate. The fish observe that the bubbles go the same rate no matter how fast they swim toward or away from them. The bubbles appear to slow down and speed up, but the fish realize this is a doppler effect, and is due to their motion, not the bubbles motion.

Now take the fishtank and chuck it out of the window of a 100 story building. The fish would still draw the same conclusion about the bubbles even though they, and the bubbles, are both in motion. They are just moving in a way they can't detect, becuase they can ONLY measure their speed relative to that of the rise of the bubbles. It's the paradox of special relativity.

Nowhere in this model do particles lose spin over time. They're not like small tops in space, they have discrete, quantized spin.

Right, and from our point of view, that spin is static. But since we MOVE at such discreet distances, we cannot gauge this decay, becuase the speed at which we move and the rate of decay, are relative.

The universe is not expanding into space, it is space expanding. There's a huge difference there

Right, if space is expanding, then all the particles in it would move relative to the rate of expansion. Even though they can move about in space, the space itself is changing, so the velocity available to relative movement is changed depending how much quantum momentum you have used up.

Thanks for the links (anon-coward). And I hope you can see now, why I think that the universe cannot have an "age". I could be wrong, but it's still has merit to consider before casting it away for what we think we already know.

Re:Invisible? Super Strings for Dummies.

[Drizzt Do'Urden]

Proof, please. Light always moves at the same speed.


When I was doing a research on light, I learned that in the deep seas, radiation was mooving faster than light due to the high pressure of the water. This was making radiation (something totally invisible normally) having a blue halo. Thus.. you could actually see the radiation.

Take it for what it's worth, I can't give you any source.. and this is all based on memory...

Re:Invisible? Super Strings for Dummies.

[Drizzt Do'Urden]

Oh wait.. that didn't proove that light was moving at a different speed, but more that something can travel faster than light..

sorry.. :)

Re:Invisible?

[MindStalker]

Yes, but look at it another way, each civilization may live for millions of years, or they may live for a few hundred. Either way the time between them inventing radio and the time in which they become invisible (through radio reduction, or going to some subether technology or something. Is probably in the order of 100-200 years. What is our chances of listening to a particular civilization who is going through that transitional stage right now?? I bet if we could listen to them all at the same time, but currently, we havn't figured that out yet either.

This may be a Good Thing

[rpjs]

Because do we really want to let the universe know we're here? Contact with a more advanced civilisation might have unfortunate repercussions for us - look at the impact contact with the West had on so many indigenous cultures during the ages of exploration and imperialism.

And that's just assuming the ETs are benevolent and simply can't help having the effect on us that we have on a newly contacted tribe in the Amazon. What if the ETs are paranoid about competitor intelligences arising and have a policy of wiping out any new civilisation that pops its head up over the electro-magnetic parapet? That's one of the more pessimistic explanations for the Fermi Paradox.

Re:This may be a Good Thing

[Rhombus]

Good point....look at StarFleet...they have a specific rule against this sort of thing, and it gets broken about twice an episode. :P

Seriously, though, if we were to discover an alien race that was technologically inferior to us, I entertain no illusions as to how our species would corrupt and exploit them. Why do we assume that alien races technologically superior to us would be equally superior ethically?

Re:This may be a Good Thing

[dpilot]

Or read "The Forge of God" by Greg Bear, or the Galactic Center series by Greg Benford. The hazards of becoming visible. Maybe everyone else knows better.

Re:This may be a Good Thing

[UranusReallyHertz]

The sequal to "The Forge of God" , "Anvil of Stars", took this to and extreme. One solar system had a holographic shield around the entire thing that consumed a large percentage of the entire star's output. And a decoy system that was booby-trapped in a very clever way. p.s. I read that WB(?) have picked up the rights to both books and a third one that has yet to be written, so we might see a movie in the next ten years or so.

Re:This may be a Good Thing

[dpilot]

Read both, heard about the movie, hope they do all, well. Generally follow Bear's works, anyway.

Re:This may be a Good Thing

[whovian]

On the other hand, what if a civilization gets the idea of "aliens" for the first time by discovering patterned interstellar radio signals? It's an involuntary violation of the Prime Directive on our part. In the big scheme of the universe (whatever that may be) I don't think this is so serious.

On the other hand, that civiliation too would probably get sued under DMCA :P

Re:This may be a Good Thing

[ericman31]

Although we don't have enough data to come to any conclusions, a reasonable first assumption about the nature of ET civilizations that are no longer restricted to their own planet is possible. We can use human experience as a starting point.

They have somehow managed to not destroy themselves with nuclear and thermonuclear weapons. Supposing that their civilization was similar to ours in terms of conflict and competition, the assumption is that means of dealing with conflict are in place. This is good news for us if they are more advanced than we are.

They are much older, racially speaking, than us (unless there is a breakthrough in energy right around the corner for us) and so probably have a bureaucracy from hell, making ours look like kids playing office.

So if they did decide to wipe us out or make us a dependent colony, then most likely the Emperor's order would be lost for a thousand years in the filing system!

Re:A limited form of invisibility

[dzym]

There is no reason expect that oxygen is the basis for all life in the universe. The scientific community has become increasingly aware of small bacteria-sized creatures currently termed archaea. These creatures do not depend on photosynthesis for their nutrition but instead rely on varying and diverse elements (including some of the "heavy" ones) and presumably also do not require the existence of massive amounts of oxygen to survive/thrive.

Bottom line: don't assume that just because humans require oxygen to survive, that any other alien species must also, and that they would necessarily also search for oxygenated worlds.

Re:A limited form of invisibility

[joto]

And this has exactly what to do with radio-signals?

Re:A limited form of invisibility

[dzym]

Just posting to correct some incorrect assumptions of the previous poster.

The Truth Wants To Be Free

But then again it's Slashdot so why do I care ...

Not True

[Perdo]

I thought of this years ago. Then realized I was wrong. How much power does your local AM radio station put out? 50,000 watts. Will the ammount of power required to broadcast to three states ever drop? Nope. How many 50,000 watt radio stations are there in the US alone? Over 8000.

Will XM sattelite radio change that? Has linux been able to break Microsoft's monopoly?

Re:Not True

[babbage]

Actually, almost all of the high power AM stations are required to throttle back at night so that they can't interfere with each other. During the day they have to pump out that much power to get through the Sun's radiation; at night the signals have no such interference and so have to operate at low power to keep from trampling each other. There are only a dozen or so AM stations allowed to broadcast at full power overnight as a result.

So, yeah. The amount of power required to broadcast to three states rises & falls every single day, and the amount of power used to accomplish this is adjusted accordingly :)

Another interesting angle is signal compression & encryption, both of which can make the signal sound like so much static. Will this make us more "invisible" too? Presumably a burst or stream of seeming gibberish might be distinguishable from true static if you know what you're listening for, but if not it could easily blend into the background noice. Conversely, if other civilizations are doing the same thing, picking up their signals could be very difficult -- much harder than just scanning for Betelgeusian episodes of "I Love Lucy"... :)

Re:Not True

[AJWM]

There are only a dozen or so AM stations allowed to broadcast at full power overnight as a result.

I suspect Denver's KOA (850 kHz) is one such. They certainly pump out 50 kW, and brag about reaching a 38 state (plus Canada and Mexico) area.

OTOH, one reason for the huge range is that the radio signal is reflected back to Earth by the Heaviside layer, reducing the amount of it detectable beyond the ionosphere.

Somewhat-slightly-less-than-great opening lines

[realgone]

"I am an invisible planet. No, I am not a Kamino like that which eluded Obi-Wan Kenobi; nor am I one of your Hollywood-movie hurtling asteroids. I am a planet of substance, of soil and bedrock, forests and oceans -- and i might even be said to possess a voice. I am invisible, understand, simply because bug-eyed aliens refuse to listen to my... erm... reduced-power, shared-spectrum, electromagnetic transmissions."

Vow of silence

[Dr. Cody]

I don't think that we have to worry about being a silent planet if these guys [vaticanradio.org] keep it up [guardian.co.uk].

Holy Shit Batman!

[capt.Hij]

Italy passed a new law regulating electromagnetic emissions in February, which sets a limit of six volts per square metre for inhabited areas. Residents in Cesano have complained that the eletromagnetic emissions in their homes sometimes exceed 50 volts per metre.

Wow! I thought the neighbors described in the article were whining until I got to this part. This is a staggering amount of radiation that they are pumping out.

I once spoke to some Air Force dudes about this sort of stuff, and they said that the big concerns were over endocerine systems. It would be very interesting to see if there are any problems with diabetes or other such diseases in the area. Sounds like a perfect test bed to see if e-mag emissions really can be harmful.

Of course the complication here is that if someone there gets sick, they can rest assured that the pope will be praying for them. It is probaly a bit tough to add such complications into your statistical models.

From the mouth of a terrone

[Dr. Cody]

A Sicilian friend of mine once visited Rome and said that, even from outside the walls, the buzzing was almost deafening on some days.

We are assuming a lot about alien psychology

[bigsexyjoe]

We don't know how these aliens think. They may be curious and interested in us, or they may not. Their way of thinking may or may not be similar to ours. It is hard to know how they view the universe.

I don't think they will invade the Earth though. The amount of energy needed to come over means that it wouldn't make sense to come over for resourses and they don't need us for slaves if they can develop artifical intelligence technology.

The best reasons for contact would be curiosity and to share knowledge of mathematics and what not.

Moon transmitter.

[Yet Another Smith]

What the heck is stopping us from setting up a transmitter station on the far side of the moon which beams out as powerful a message as we want without interfering with terrestrial communications one bit.

You'd be able to broadcast a hemispherical signal in all the transmission windows no problem. You could broadcast with as much power as you can provide, and the moon would sheild earth-bound and even orbital communications systems.

Re:Moon transmitter.

[IndependentVik]

Oh yeah, like NASA has any money as it is.

Frequency Hopping and other Obfuscation

[ZahrGnosis]

Even if some extra-terrestrials can pick up our wireless communications, their ability to decipher it from noise may be limited because of new technologies, notwithstanding the power of our transmissions.

Consider the 2.4GHz range and frequency hopping. There's no way anyone picking up the earth's aggregate transmissions in that band would be able to decipher them, (frequency hopping is designed that way)... TV and AM/FM broadcast signals are relatively simple to decipher, having carrier signals that are quite regular.

I also understand that radio waves are fairly common in the universe, although not being at all the astronomer, I have no idea why. If our airwaves get too muddled, I imagine we won't look much different to a radio telescope than some other radio-prolific celestia.

Another question is, has this already happened somewhere else? I think I remember hearing that SETI's work, particularly their distributed computer search software would probably miss wide spread-spectrum FH radio technology and consider it white noise. Any word on that?