we've been looking at radio waves for sometime now. If they're there, must b tons of stuff we're not looking in right media. Maybe it's lasers. What else could act as a carrier??

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Lasers are just beams of light. Light is electromagnetic waves, just the same as radio waves, just different frequencies. Maser is the microwave equivelent to a laser.

S@H realize they are only searching a small portion of the spectrum. There are other SETI projects that are searching a much larger spectrum, but they do that at a cost.

Another issue with lasers is that the divergence of a laser beam is so incredibly small that another civilization would almost have to point the beam directly at us for us to see it.

You definitely have the right idea. There are so many different mediums and areas of the spectrum that we still have yet to search, but we have to start somewhere. Keep thinking and keep the ideas coming. you just may be the one who stumbles onto the right idea.

we've been looking at radio waves for sometime now. If they're there, must b tons of stuff we're not looking in right media. Maybe it's lasers. What else could act as a carrier??

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A laser is far more efficient in actual transmission. Despite divergence, it still does not follow the inverse square law that applies to a radiated energy like lightbulbs and stars (put simply, the strength of the energy per unit area drops as the reciprocal of the square of distance. At 2x unit distance, the strength is 1/4, at 3x, it's 1/9, etc).

The biggest problem with laser-type devices is they're enormously inefficient devices in actually generating the beam. I read somewhere that the average laser only outputs .3% of its input energy as coherent light. This "wallplug efficiency" is the major drawback both in laser-based weapons and in laser based space communications. According to a quick internet search, they're still looking at ranges of 15% or so for even the best lasers. See High efficiency pulsed laser transmitters for deep space communication for an example.

High powered lasers have to dissipate more of this waste energy, largely in heat of course, so it becomes more difficult to make more powerful lasers when you start reaching operating temperatures that can easily damage your laser device.

Other problems have to do with the fact that we have to fire this beam through an atmosphere. One of the big problems with the high powered lasers used in the Strategic Defense Initiative (Star Wars) experiments is as the laser fires through the atmosphere, it causes the air to heat up. When the air heats up, it refracts the beam, thereby causing the spot you first fired at not to be the one you're aiming at a few nanoseconds later.

Since there's a practical and fairly low limit to the power we output, here's where the divergence actually becomes a problem. You'd want a machine with some divergence so at interstellar distances you're blanketing a good chunk of the destination planetary system, but since you're actual energy out the aperture is woefully limited, you may not get a strong enough signal per unit area to be detected.

Sticky problems. I'd have to read a bit more and maybe work with a few of the numbers to see how practical lasers in specific would be at interstellar distances. So far as I know, NASA has been solely relying on conventional microwave emitters with waveguides and parabolic "mirrors" (the ubiquitous "satellite dish") focusing the beam for conventional "short range" space communications, i.e. everything we've sent out so far. Speaking of microwaves, looks like we've unfortunately finally lost contact with Pioneer 10.

i wasnt thinking of lasers but of what other means besides the radio waves aliens might be using to transmit. Could they use x-rays? What else can be used as a carrier besides radio waves?

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i wasnt thinking of lasers but of what other means besides the radio waves aliens might be using to transmit. Could they use x-rays? What else can be used as a carrier besides radio waves?

x-rays and radio are the same thing, just like light. They are all electromagnetic radiation.

I have wondered in the past about whether we could detect intelligent alien lifeforms by the effects that have on their environment. Could an alien civalisation harness garvitational energy as a communcation media? Could we detect their presence by analysing differences in gravitational fields? Or maybe that should be left the Einstein@home!

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Could an alien civalisation harness garvitational

damned spelling was never my best subject at school!

It's past the edit timeout, so it should have read: ...... Could an alien civalisation harness gravitational energy .....

sorry :-(

i wasnt thinking of lasers but of what other means besides the radio waves aliens might be using to transmit. Could they use x-rays? What else can be used as a carrier besides radio waves?

x-rays and radio are the same thing, just like light. They are all electromagnetic radiation.

I have wondered in the past about whether we could detect intelligent alien lifeforms by the effects that have on their environment. Could an alien civalisation harness garvitational energy as a communcation media? Could we detect their presence by analysing differences in gravitational fields? Or maybe that should be left the Einstein@home!

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Yes after hearing about string theory and that gravity can pass through deminsions, wondered if it could b used to communicate, could gravity b used as a carrier?

i wasnt thinking of lasers but of what other means besides the radio waves aliens might be using to transmit. Could they use x-rays? What else can be used as a carrier besides radio waves?

x-rays and radio are the same thing, just like light. They are all electromagnetic radiation.

I have wondered in the past about whether we could detect intelligent alien lifeforms by the effects that have on their environment. Could an alien civalisation harness garvitational energy as a communcation media? Could we detect their presence by analysing differences in gravitational fields? Or maybe that should be left the Einstein@home!

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Einstein@home is only searching for sources not if there are patterns of communication in the pulses.

Yes after hearing about string theory and that gravity can pass through deminsions, wondered if it could b used to communicate, could gravity b used as a carrier?

i wasnt thinking of lasers but of what other means besides the radio waves aliens might be using to transmit. Could they use x-rays? What else can be used as a carrier besides radio waves?

x-rays and radio are the same thing, just like light. They are all electromagnetic radiation.

I have wondered in the past about whether we could detect intelligent alien lifeforms by the effects that have on their environment. Could an alien civalisation harness garvitational energy as a communcation media? Could we detect their presence by analysing differences in gravitational fields? Or maybe that should be left the Einstein@home!

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To quote my favourite Author (Arthur C. Clarke):

"The fact that we have not yet found the slightest evidence for life - much less intelligence - beyond this Earth does not surprise or disappoint me in the least. Our technology must still be laughably primitive, we may be like jungle savages listening for the throbbing of tom-toms while the ether around them carries more words per second than they could utter in a lifetime."

2001: A Space Odyssey (the novel, p390)

Listening for an intentional beacon or signal is like finding a needle in a haystack (and that's assuming they are using communications technology that we could receive and detect, never mind identify).

Given this hurdle I believe we should continue to search for radio waves, but we should also look for evidence that does not require us to have compatible technology (since we have no real idea as to what their technology will be).

We should, if we can, try to figure out ways of indirectly detecting their technology. Such as Infra-Red Radiation from a Dyson sphere or a Kardashev Type Civilisation. In this vein we should not necessarily discount Gravity waves as being an effect of technology, worthy of further investigation. Along these lines I think we should also consider Pulsars, the ultimate in navigational or positional beacons over interstellar distances (I'm not saying Pulsars are artificial, but they have good time keeping and they are all unique) - what better place than near a pulsar to place a transmitting/receiving device (that is somehow not affected adversely by the pulsar itself) and that we can try to detect.

This is of course all sheer speculation, but it can't hurt (too much) to try and think of alternative scenarios or even "outside of the box".

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For anybody who's interested:
A SETI League essay on the question: Where Is Everybody?
Arthur C. Clarke's life and work

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Join TeamACC

Sometimes I think we are alone in the universe, and sometimes I think we are not. In either case the idea is quite staggering.

Like Nightlord pointed out, gamma rays, x rays, ultraviolet, visible light, infrared, microwaves, and radio wave bands are all part of the same thing, the electromagnetic spectrum. As I understand SETI, their purpose is to search the part of the spectrum around the "hydrogen line", a relatively quiet area.

I read an article in Science News many years ago on "T-rays". This is an area of the spectrum between microwave frequencies and the far infrared. This band is relatively quiet because very little naturally occurring phenomena either produce or absorb these frequencies, if I remember the article correctly. I've idly wondered if this might not be a good place to search.

Needless to say, a big problem is that if very little interferes with it, then by corrollary it's tough to build a device to transmit or receive it (look at the huge lengths they have to go through to detect neutrinos).

As for the gravity modulation thing, interesting idea. I wonder if we might detect a signal someday by a sudden unnatural change of the spin of a neutron star by something that added a peculiar amount of mass to it. Kinda a big cosmic gravitic "gong".