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View Full Version : Ep. 110: The Search for Extraterrestrial Intelligence

Fraser
2008-Oct-14, 10:20 PM
You know what this show needs? More aliens. Since we don't seem to have any visiting right now, we're going to have to find some. SETI is an acronym. It stands for the Search for Extraterrestrial Intelligence. But there's more to SETI than just putting up a radio telescope and hoping to catch a glimpse of an alien television broadcast.http://feedproxy.google.com/~r/astronomycast/~4/0y1ahalXH08

Pepsi Is My Blood
2008-Oct-15, 09:55 PM
An incredibly minor nitpick on this episode: the 10 cent deposit is in Michigan not Massachusetts... we only get 5 cents here.

The episode was great as always though. I started listening around episode 82, and have since gone back through and listened to all of them.

jasonb
2008-Oct-20, 02:26 AM
1. Do we have the ability to calculate exactly how many stars are within a given light-year radius from Earth? Is there a website I can go to and plug in say "25 light years" and it will tell me exactly how many suns fall within that radius? Fraser glossed over that in the show commenting "hundreds, if not, thousands of suns" within a 70 ly radius. It would be interesting to know how many suns fell within the first 25-year period from the point we started broadcasting, and then how many during the 2nd and 3rd periods and, finally, how many will be within reach during the upcoming 25-year period.

2. Relatedly, if a civilization received a signal and responded back (at lightspeed), then the only suns that could be currently "in play" from a communication standpoint would be those within a 35 ly radius. Is that correct? So, how many suns are within 35 ly?

3. Dr. Gay stated that the Drake equation was developed to estimate (and I quote) "the number of alien CITIZENS on alien worlds." I was under the impression that it attempts to estimate the number of CIVILIATIONS only. Please clarify.

Thank you.

AmroB
2008-Oct-20, 10:25 AM
Hi Jasonb,

"3. Dr. Gay stated that the Drake equation was developed to estimate (and I quote) "the number of alien CITIZENS on alien worlds." I was under the impression that it attempts to estimate the number of CIVILIATIONS only. Please clarify."

I'm not Pamela, but yeah the equation deals with the number of civilisations; a slip of the tongue on Dr Gay's behalf I think.

You can read more about the Drake Equation at SETI’s at

http://www.activemind.com/Mysterious/Topics/SETI/drake_equation.html

Episode 23 of Astronomy Cast (Counting Aliens with the Drake Equation) dated February 12 2007 deals with just that as you can tell from the title. Just go to the show’s archive...

HTH and have fun listening to Ep 23!

timb
2008-Oct-20, 11:21 AM
Hi Jasonb,

"3. Dr. Gay stated that the Drake equation was developed to estimate (and I quote) "the number of alien CITIZENS on alien worlds." I was under the impression that it attempts to estimate the number of CIVILIATIONS only. Please clarify."

I'm not Pamela, but yeah the equation deals with the number of civilisations; a slip of the tongue on Dr Gay's behalf I think.

On his part, surely. If it were done in his behalf then someone else did it for him.

AmroB
2008-Oct-20, 12:09 PM
Ha? Sorry timb I'm not following. You can tell that English isn't my first language, no? :)

Neverfly
2008-Oct-20, 12:11 PM
Ha? Sorry timb I'm not following. You can tell the English isn't my first language, no? :)

Speaking as an American... Your profile location is a dead giveaway that you ain't speakin' proper English.

AmroB
2008-Oct-20, 12:21 PM
Neverfly, strange, the English think otherwise ')

Cheap Astronomy
2008-Oct-20, 09:16 PM
Hi,

Reply to Jason B - you could achieve what you want to do by searching the term 'nearest stars' in Wikipedia. You will find a list of stars with their distance from the solar system in light years.

I don't know about thousands of stars within 70 lys, but there are hundreds. The Wiki article lists 50 within 16.3 light years

The most massive star within 10 light years is Sirius A if you were wondering about the trivia question on last Planetary Radio podcast.

sohh_fly
2008-Oct-20, 11:55 PM
DR. Gay stating that the drake equation was formulated to find alien civilizations.
whats wrong with her statement , cause thats exactly what they would be "alien"...so i see nothing wrong with her statement.
why wouldn't we consider them alien after all there not from this world IF their out there....so alien is just fine for the question of the drake equation

my 2 cent's

timb
2008-Oct-21, 12:28 AM
1. Do we have the ability to calculate exactly

Obviously not. If you are calculating then you are estimating. To know "exactly" how many stars there are in a given volume you have to count them one by one.

As someone else posted there is a list of 50 known star systems within ~16.3 ly. You can draw your estimates for larger distances from that, though the list is very likely incomplete. Nearby red dwarfs such as Teegarden's Star have been found in the last few years and so there are probably more there to find.

NHR+
2008-Oct-21, 01:13 PM
On his part, surely. If it were done in his behalf then someone else did it for him.

Last I heard Dr. Gay was a female, so "her", not "his/him".

Just some more nitpickin' here... :)

mirid
2008-Oct-22, 05:50 PM
Great show. The possibilities of advanced civilizations out there is one of my favourite things to think about.

murphed
2008-Oct-22, 07:06 PM
It seems to me that we have not found likely habital planets in or near our solar system, so aliens would have to travel some distance to get here. Traveling closer to the speed of light would get them here faster; however, I understand (AE) that the faster they go the more time would slow down for them. When they return to their home a lot of time might have passed. Would they have to go fast enough where this really made a difference. If so, why would they spend travel time then buzz a few airplanes, probe farmer or two, and then go home?!?

I would like to get some idea of the variables; i.e.:
Is it likely they would have to come from some distance away since we cant find anything close?
If so, what price would they likely pay in time?

I have heard people discuss this but I cant wrap my mind around whether it is a big issue since we cannot seem to find any close candidate planets?

Sorry for the rambling

murphed
2008-Oct-22, 07:13 PM
Per previous post:
I guess I am asking what the curve looks like (Faster Speed = Slower time).

formulaterp
2008-Oct-27, 02:53 PM
Per previous post:
I guess I am asking what the curve looks like (Faster Speed = Slower time).

This is probably what you are looking for:

http://www.fourmilab.ch/cship/timedial.html

As you can see, the time dilation effects are not that significant until you get up to an appreciable fraction of c.

I'm not sure how big of an issue it is. If you are going to travel 100's of lightyears to buzz a planet and/or probe a few orifices, you just have to accept that centuries will pass on your homeworld by the time you get back. Your speed will only affect how much time passes for yourself, not for the rest of the universe.