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Sep122011

So your friend asks...Do you think we'll ever talk to aliens?

So you're sitting around at your book club, and nobody actually read the book, so people keep trying to change the subject, and that one guy knows that aliens always serve as a good red herring. So that guy asks, "Do you think we'll ever talk to aliens?"

Here's what you say:

Look, I know it's really cool to think that your new BFF is going to be an alien from the Whirlpool Galaxy, but you know what?

a) s/he (or both, given the possibility of evolutionarily advantaged hermaphroditic aliens) would probably think you're really strange
b) your new BFF probably wouldn't even be an alien from the closest star, Proxima Centauri, whose name literally means "close Centauri."

Let us set aside the question of whether or not ETI (extraterrestrial intelligence, the PC term for aliens) exists. My personal opinion? Statistics. There are 200-400 billion stars in our galaxy alone, and there are about 100-500 billion (gotta love astronomical error bars) other galaxies. Even if life rarely arises, chances are (by the definition of that phrase) somebody exists out there. IMHO, as they say.

But, regardless, this post is about talking to the ETI, more specifically talking with the ETI. There are two ways we could use contact to discover that ETI exists: 

  1. By our receipt of their message.
  2. By transmission of our own message, receipt on their end, their consequent/subsequent transmission, and subsequent receipt on our end.


In short, we'd have to be a lot
like Jodie Foster.
The possibility of the first is limited by several factors. First, we have to be looking in the exact right place. Second, we have to be looking at the exact right time, when they are an advanced civilization that hasn't destroyed itself and happens to be broadcasting. Third, we have to be looking at the right frequency. There are infinity frequencies. We have the idea that smart things would be broadcasting at certain frequencies to alert us to their smartness, but we could be wrong. Ideally, to find ETI, we would have zillions of telescopes pointed at zillions of spots on the sky monitoring zillions of frequency channels with fine time resolution 24/7/365.25. But we only have so much money, we only have so many resources, and we don't have a zillion anythings because 'a zillion' is not a real number.

The possibility of the second is basically a non-possibility at the moment. Transmission of a signal with the intent that it reach ETI, a practice known as "active SETI," is basically nonexistent. To broadcast a signal that ETI could pick up, we either have to make that signal extremely strong (sucking all the power out yo grid), or the ETI has to have an extremely sensitive telescope. The strength/brightness of a light wave dies down according to the "one over r-squared law," where the "r" of this phrase is the distance between the transmitter and the receiver. If you double your distance from a transmitter, the strength of its signal goes down by a factor of 4. If you triple your distance, it goes down by a factor of 9. If you quadruple your distance, the light you receive is 16 times dimmer than it was when it left the transmitter. Think about a flashlight, and how ineffective it feels when you're walking alone through the haunted forest.

This is from a website called "free haunted forest wallpaper."


But let's say that we either put out a radically strong radio beacon or the little green men (and women) have a radically powerful radio telescope. Their telescope still has to be pointed at us; it still has to be pointed at us when we're transmitting; it still has to be sensitive to the right frequency.

"Hey. Spell 'I cup.'"
Source.
But let's say that stars aligned (pun intended, as always), and all of the above were true. The aliens are jumping up and down and saying, "We found aliens!" and calling their press corps and joining end-of-the-world cults and accusing their governments of hiding the truth.

Their receipt of the signal was not instanteous: they didn't catch what we were throwing when we threw it. It had to travel across space for however many light-years they are away from us. By the time it gets to them, humans could be extinct or ruled by robot overlords. At the very least, our technologies, priorities, and attitudes toward SETI research--toward everything--would have changed.

Even knowing that, perhaps the ETI decide to send a signal back. They power up their near-magical signal generator and zap it in our direction. But for how long do they zap? A year? Two years? Ten? 

Since we don't know how far away the civilizations may be, we have no idea when the signal will get to them, and we thus we have no idea how quickly we could expect to receive a HELLO WORLD back. We, not knowing they had received our signal, would still be blindly searching. We would have to have our receivers, still, trained to the right place at the right frequency at a time equal to (their distance from us in light years+their distance from us in light years+however long it took them to work up a HELLO WORLD) if we wanted to receive it as soon as we could. If they broadcast for a while, we would have that amount of time to set our telescopes to the right place/frequency.

But let's say the stars aligned, and we got their signal. If the civilization were at the closest star, it would take a minimum of 8.5 years for us to hear back. Then, if we turned around the very next day and sent a reply, it would take them 4.24 years to receive it, and 4.24 years for us to receive their response, if they turned around the next day too. That doesn't sound so bad, I guess, now that I type it out. HOWEVER, it turns out that not all stars can be the nearest star. Most stars in our galaxy are thousands or millions of light-years away, making potential conversations much longer, much more awkward.

Are you depressed? Are your childhood dreams crushed? Don't feel that way!

Research in astrobiology is really getting going. We're working--both here on Earth, through research on scaryawesome things like extremophiles, and in space, through research on organic molecule/DNA precursor abundance--on figuring out how easy, or not easy, it is for life to form. As we learn more about the processes that led to our existence, we will be able to say more about the likelihood that other Usses, with sixteen arms and aresenic-based DNA, evolved on other worlds. 

Here's my philosophical speech.

We base the study of astronomy on the idea that if you start with similar initial conditions, you get similar end states, and similar stages along the way--that there are, for instance, only certain kinds of stars that form, certain paths their lives take. That there are galaxies everywhere, and that they only come in a few types, even though no galaxy near X edge of the universe told any galaxies near Y edge of the universe, "Hey, I'm forming this way. You should too." We look at stars that are one solar mass and the same age as the Sun and feel pretty confident saying, "In a billion years, you will do basically the same thing our Sun will do in a billion years." 

All science is based on the idea that fundamental laws underlie everything that goes on in the universe. That solar-mass star will do ~what the Sun does because they are subject to the same laws.

Doesn't it go against the way we think of all other natural processes, then, to say, "It only happened here"?

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    Response: superior paper
    Scientists are trying to have communication with other galaxy aliens. By using ETI they are transmitting signals into outer space and waiting for the recipient signal. There is no particular evidence to say that aliens are exited. But, some rumors say that they are present in another galaxy and use more ...

Reader Comments (2)

A brilliant summary to the column, and the fundamental assumption of all science - "All science is based on the idea that fundamental laws underlie everything that goes on in the universe. That solar-mass star will do ~what the Sun does because they are subject to the same laws." Without that assumption, any attempts at predictive power become meaningless.

September 14, 2011 | Unregistered CommenterCharlie

Boyfriend made me watch, seeing as I'm a nerd who has not seen this movie yet.

March 19, 2015 | Unregistered Commenterblogsforwomen

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