Book Research, Astronomical Justification for Plot Device

[john.andrews]

Little preface to this series of questions, I'm really into theoretical physics but I have very little astronomy knowledge. I'm a very curious person so feel free to talk over my head and I'll google what I need.

That being said, I'm participating in Novembers "Novel Writing Month" as a fun project in my spare time. I'm doing some research into astronomical facts I'd like to use to justify some things in my story. I figured I could make stuff up, or I could learn something and add a bit of authenticity to the book.

Long story short, we receive a signal which appears to be a mass of alien transmissions (something like what aliens 50 light years away would be getting from us right now...). The thing is I want the aliens to be at about a 1960s level of technological development and I'd like them to be far enough away that they wouldn't be able to see any of our transmissions (meaning pre-1930s, at least 100 or so light years away). I'd like to select a real star to use in the story.

-What real star could I use that is at least 100 light years away and could possibly have a planet around it that supports life (even, especially if none has been discovered)?

-What justification can I use as to why we haven't noticed any transmissions from this planet before? (I'm thinking something like a lensing effect, a star blocking it's path, a strange orbit, etc... not "they weren't sending any out into space")

I know it's a lot to ask (feel free to just point me in the right direction, I'm not shying away from research), but any advice/ideas/help would be great!

 

[chemisttree]

Well if they are 100 ly distant and they are currently living in the 60's, they would have had to have radio in their version of 1860! That assumes that their civilization develops technologically at a rate similar to our own.

Hmmm. Find a star at least 100 ly distant? The milky way is about 100,000 ly across. You need to find a model of the milky way and pick a region located about 1/10 the diameter of the disc. http://cfcpwork.uchicago.edu/kicp-projects/nsta/pdf/milky-way-model_plot.pdf" Looks like Alkaid works.

 

[john.andrews]

Well finding the star shouldn't be too difficult, but what about the justification for why we're just not seeing those signals? I mean obviously you have to be pointing your radio telescope in just the right direction, but I was under the impression that SETI had already surveyed the surrounding 100-200 light years of stars and come up with nothing obvious so far (although I admit this information isn't something I've confirmed since beginning this book). If this isn't the case then I'm good, we just didn't look there yet! If it is, why didn't we see what is supposed to be (for the sake of the story) a very obvious and dense set of signals?

 

[chemisttree]

Did WE have the radio in 1860? Think about it.

If we survey a star 200 ly distant and get a signal... it's 200 years old when we receive it.

 

[john.andrews]

I don't think I'm being clear lol.

The signals we are receiving today (2010) are of a civilization who has had radio for 50-60 years (meaning they're 150-160 years ahead of us if they're 100 ly away). So we should've been receiving their signals for the past 50-60 years because they 'started transmitting' from our perspective 50-60 years ago. We just didn't see it until now.

Timeline order goes a little like this...

2010 we get their first signal
1950 the first signal we could've gotten hits earth

1910 they transmit the signal we receive first
1850 they send their first signal

Why didn't we see their signals for 60 years?

 

[twofish-quant]

Well finding the star shouldn't be too difficult, but what about the justification for why we're just not seeing those signals?

It's possible that the aliens for various bureaucratic and cultural reasons have decided to use only a small set of frequencies in the radio spectrum, and it so happens that the frequencies that they've decided to use happens to be the ones in which we've used for things like CB radios.

Radio astronomy tends to happen only on certain frequencies that have been blocked off from terrestrial use. If you try to do radio astronomy on the same frequency as AM or FM radio signals you aren't going to see very much.

Maybe very early on, your aliens have decided to keep the sky spectrum clear, and to only transmit on some selected frequencies which happen to be block on Earth by CB radios.

I mean obviously you have to be pointing your radio telescope in just the right direction, but I was under the impression that SETI had already surveyed the surrounding 100-200 light years of stars and come up with nothing obvious so far (although I admit this information isn't something I've confirmed since beginning this book).

It's also possible that for cultural and political reasons, your aliens don't use radio transmissions. The first radio transmissions were to communicate to ships. Suppose your aliens are on a planet that has one huge continent so there isn't much use for ships. So pretty much all communications goes through land lines.

 

[twofish-quant]

One other thing to note is that it's really hard to detect television signals from the Earth from large distances

http://www.setileague.org/editor/uhftv.htm

Part of the problem is that TV broadcasters intentionally setup their antenna so that most of the power gets radiated toward the ground and anything that goes into space is leakage. It could be that your aliens are just much better at controlling leakage than we are.

There are lots of reasons for this

1) maybe your aliens just live on a relatively small part of the planet and so they don't have to have big antennas

2) maybe your aliens live in an energy poor environment (i.e. no oil) and so they have to be extremely stingy about power. Putting kilowatts of energy into your antenna might be inefficient.

3) maybe your aliens have a different culture in which you don't have radio stations that are controlled by large corporations. On your planet, people use radio for low power transmissions.