Thursday, October 24, 2013

SETI, Radio Communications, Wastes of Time

One of the standbys of SETI (Search for Extra-Terrestrial Intelligence) has been listening for radio waves from outer space.

We've never heard any alien communications. Or anything resembling alien communications. Of course, radio's important. We use it...

...brakes on.

We use radio communication, sure. For cell phones. How close do you have to be to a cell tower to get a signal?

In perfect conditions: 45 miles. And we all know conditions are never perfect. Dropped calls, texts that don't get sent, randomly losing data in the middle of checking your email - such are the banes of the cell phone user. Technology has improved bandwidth, but it's still limited.

And that...is the only thing we really use radio for. Oh, true, there are still radio stations broadcasting. When was the last time you listened to one? Why - when most of us have several day libraries of MP3s on our computers or enjoy the customization of services such as Pandora, Spotify, or the new iTunes Radio? Who's going to let a DJ pick when they can set a seed algorithm, let it run, and enjoy?

Broadcast radio's not extinct yet, but it's close. (Amateur radio is still strong, but a lot of that has also moved to the internet in the form of podcasts and, of course, we still have no good substitute for the faithful CB or short range walkie talkie).

So.

Do you know anyone who still watches television through rabbit ears? Do you? I doubt it - either cable or satellite is the order of the day. Now, satellite television is still radio. I'll give you that. And signals from the broadcast center are broadcast into space. In theory our extra-terrestrial "friends" could pick up those signals...if they could work out how to decode them. These signals are highly compressed, encoded, and then encrypted. They are also beamed - as anyone who's ever had a satellite dish knows, you need to point your dish right at the satellite and if that's not possible on your property, you're out of luck. If there's a tree in the way, you may be out of luck. Weather can also interfere with the signal. All kinds of things can mess it up. So, in order for an alien to pick up our satellite broadcasts, they would have to have a receiver pointed in the right direction...and nothing in the way. What are the chances of that? As for terrestrial broadcasts - those too can easily be blocked by objects.

The rest of us get our television piped through cables (although if watching a live sporting event the signal probably went through a satellite at some point). The technology is currently moving from electronic transmission to "fiber optic to end user" (which allows much more bandwidth).

So. For an alien to pick up one of our broadcasts would be surprisingly hard - yet we think we're going to pick up theirs?

Ah, but what about signals sent to and from spaceships? We use radio for that, right?

Not so fast. First of all, again, any radio we use is tight beam, so the aliens would have to happen to be in the line of it. And, again, there's the same problem with obstacles in the way.

Furthermore, I and many other science fiction writers have held to the idea that radio is an inefficient way to communicate with ships and any higher civilization would long since have stopped using it. This has always been a theory.

Until now. LADEE, NASA's latest moon probe, doesn't use radio. She uses laser communication - the first use of it in space. Laser communication would have a far greater range than radio and can transmit, just like those fiber optic cables, far more data.

And, of course, it's still tight beamed.

Absence of evidence is not evidence of absence.