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Old 07-19-2016, 01:13 AM #289
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Default Re: Space Discussion Thread

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Originally Posted by Benm View Post
Who knows what the exact motivation is in china - it could just be a prestige project, but also something like a race to make 'first contact'.

It will not pick up alien TV stations if those are anything like our analog tv stations were. One reason this would not happen is that TV transmitters are usually designed to transmit sideways from the tower, not up into space since. Antenna's are constructed to radiate in a plane up to the horizon - after that they do take off into space, but the signal path loss would be such that there is little chance of anyone around another star even detecting the signal.

This would be different if someone sent a message on purpose. Earth once did, and a radio telescope of this size could be used to receive such messages from others. It's not beyond reason that china would outfit this telescope with a transmitter at some point, perhaps representing earth.
Have you ever heard of satellites? Nearly all of our television goes through satellites, so yes we do transmit it directly into space, much of our other communications also goes through satellites. We have been transmiting into space for many years now.

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Old 07-19-2016, 01:29 AM #290
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Default Re: Space Discussion Thread

Well, we tend to aim pretty well at those. Most of the signal actually misses, but where it goes is fairly random.

An uplink to to a geostationairy say would look like a bit of a lighthouse from far away, pulsing every 24 hours. But as the earth rotates around the sun this signal would no go in the same direction the next day. It would go in the same direction twice a year, and not even exactly that either since the mass of the solar system is not in the middle of the sun but varies in/around it depending on the position of mostly jupiter. As such it would go in -exactly- the same direction very rarely.
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Old 07-19-2016, 01:38 AM #291
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Default Re: Space Discussion Thread

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Originally Posted by Benm View Post
Well, we tend to aim pretty well at those. Most of the signal actually misses, but where it goes is fairly random.

An uplink to to a geostationairy say would look like a bit of a lighthouse from far away, pulsing every 24 hours. But as the earth rotates around the sun this signal would no go in the same direction the next day. It would go in the same direction twice a year, and not even exactly that either since the mass of the solar system is not in the middle of the sun but varies in/around it depending on the position of mostly jupiter. As such it would go in -exactly- the same direction very rarely.
You have an excuse for everything don't you? Why it's not possible. I have read that us or them should even be able to detect the use of large scale power systems like our power grids from hundreds of light years away. I also wouldn't be surprised if they can detect the use of thermonuclear weapons from long distances.

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Old 07-19-2016, 01:51 AM #292
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Default Re: Space Discussion Thread

It's not an excuse at all, it's just a fact on how uplinks work in relation to orbital mecahnics.

Also these techniques are being phased out, and earth is already going more and more radiosilent.

The analog transmissions of the past would have been easy to interpret but were aimed the wrong way. The signals we send to sats are often encrypted which allows detection but no understanding of the content.

This is all going away though, since we now mostly rely on either landlines or encrypted low power signals like 4g. And we don't even do thermonuclear weapon tests anymore either, so the earth is just becoming pretty boring to any outside observer.

This isn't all that bad though, we still have the ability to send signals on purpose that would be detectable to others far away. If sending those out would a be a wise cause of action is another debate.
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Old 07-19-2016, 02:54 PM #293
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Default Re: Space Discussion Thread

Quote:
Originally Posted by Benm View Post
It's not an excuse at all, it's just a fact on how uplinks work in relation to orbital mecahnics.

Also these techniques are being phased out, and earth is already going more and more radiosilent.

The analog transmissions of the past would have been easy to interpret but were aimed the wrong way. The signals we send to sats are often encrypted which allows detection but no understanding of the content.

This is all going away though, since we now mostly rely on either landlines or encrypted low power signals like 4g. And we don't even do thermonuclear weapon tests anymore either, so the earth is just becoming pretty boring to any outside observer.

This isn't all that bad though, we still have the ability to send signals on purpose that would be detectable to others far away. If sending those out would a be a wise cause of action is another debate.
Haven't yall watched the new x-files? They came because of the thermonuclear testing. What I'm wondering is how they got through the glass at the top of the dome.
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Old 07-19-2016, 03:31 PM #294
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Default Re: Space Discussion Thread

Quote:
Originally Posted by Benm View Post
It's not an excuse at all, it's just a fact on how uplinks work in relation to orbital mecahnics.

Also these techniques are being phased out, and earth is already going more and more radiosilent.

The analog transmissions of the past would have been easy to interpret but were aimed the wrong way. The signals we send to sats are often encrypted which allows detection but no understanding of the content.

This is all going away though, since we now mostly rely on either landlines or encrypted low power signals like 4g. And we don't even do thermonuclear weapon tests anymore either, so the earth is just becoming pretty boring to any outside observer.

This isn't all that bad though, we still have the ability to send signals on purpose that would be detectable to others far away. If sending those out would a be a wise cause of action is another debate.
Let's assume there ARE intelligent aliens who are capable of getting to us. I see three main possibilities.
1-They kill us all and take our planet, or they enslave us and rule with an iron fist.
2-They just ignore us. Perhaps they don't consider us advanced enough as a species to be worthy of joining the galactic council or w/e. We still have idiots killing over religion and such. It's pretty understandable if the aliens want nothing to do with us.
3-They make contact with us, and try to help us save ourselves by giving us technological help. This could also turn into a "Rule over us with an iron first for our own good" kind of thing.

Which would it be? Personally I don't think it's worth the risk of intentionally trying to contact aliens.

I actually consider #1 somewhat likely considering the fact that planets don't stay habitable forever. Even if we take perfect care of our world, scientists believe the increasing luminosity of the sun will render it uninhabitable within 500mil-1billion years. If humans are still around at that time we'll likely be very technologically advanced, and in search of a new home planet. If there are any less-advanced natives on the new world we find it will probably suck quite a lot for them. If they're LUCKY we'll just kill off most of them, and stick the remaining survivors in reservations.
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Old 07-19-2016, 03:57 PM #295
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Default Re: Space Discussion Thread

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Well, we tend to aim pretty well at those. Most of the signal actually misses, but where it goes is fairly random.
Random? Since we have no clue if/where other intelligent life may be, what difference does it make.
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Old 07-19-2016, 05:02 PM #296
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Default Re: Space Discussion Thread

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Haven't yall watched the new x-files? They came because of the thermonuclear testing. What I'm wondering is how they got through the glass at the top of the dome.
Many people think this. There have been sightings and even visitors throughout history, but it wasn't until 1947 that they started showing up in large numbers. Our first atomic bomb test was at the Trinity test site in New Mexico in 1945. This is also near the White Sands missile test range and two nuclear facilities for research and developement of nuclear weapons. These are all very close to the city of Roswell, there were many sightings there starting two years after the first test at the Trinity test site, this would be in 1947, Roswell was also the location of the Army Air Force 509th bomb group starting a short time later, our first nuclear capable bombers, my father was stationed there with them for a time. My guess is that a ship was passing near our solar system and detected the energy signature of an atomic bomb and put us on their list of places to check out and reported home about it and they started showing up to investigate two years later. Today there are about 10,000 sightings a month world wide, that is a huge number! China gets no shortage of sightings and even reports of craft landing, we don't know how many but I think this is why they decided to build the radio telescope.

Quote:
Originally Posted by Razako View Post
Let's assume there ARE intelligent aliens who are capable of getting to us. I see three main possibilities.
1-They kill us all and take our planet, or they enslave us and rule with an iron fist.
2-They just ignore us. Perhaps they don't consider us advanced enough as a species to be worthy of joining the galactic council or w/e. We still have idiots killing over religion and such. It's pretty understandable if the aliens want nothing to do with us.
3-They make contact with us, and try to help us save ourselves by giving us technological help. This could also turn into a "Rule over us with an iron first for our own good" kind of thing.

Which would it be? Personally I don't think it's worth the risk of intentionally trying to contact aliens.

I actually consider #1 somewhat likely considering the fact that planets don't stay habitable forever. Even if we take perfect care of our world, scientists believe the increasing luminosity of the sun will render it uninhabitable within 500mil-1billion years. If humans are still around at that time we'll likely be very technologically advanced, and in search of a new home planet. If there are any less-advanced natives on the new world we find it will probably suck quite a lot for them. If they're LUCKY we'll just kill off most of them, and stick the remaining survivors in reservations.
You may be correct, we have no idea how common high quality habitable planets are throughout our galaxy. This may be an explanation for the cattle mutilations and the abductions, they could be doing tests for the effects of radiation and to see how much we are polluting our environment.

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Random? Since we have no clue if/where other intelligent life may be, what difference does it make.
It makes no difference at all, we have been broadcasting our location here for quite a few years, possibly long enough to reach other inhabited systems.

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Old 07-19-2016, 07:00 PM #297
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Default Re: Space Discussion Thread

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Originally Posted by Pi R Squared View Post


It makes no difference at all, we have been broadcasting our location here for quite a few years, possibly long enough to reach other inhabited systems.

Alan

Even if our radio emissions have reached other inhabited systems, they would be well into the noise floor by that point. Unless some alien race has a probe rather close by that can still pick out the signals from background noise I don't imagine anyone/thing has detected us - at least not from just radio emissions.

Unless they've come up with some clever way to pull signals out of the noise floor that we've yet to discover - higher gain detectors don't help pull signals out of the noise, they just make the noise louder...
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Old 07-19-2016, 11:55 PM #298
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Default Re: Space Discussion Thread

It also depends on what you consider a signal.

Let's take something like an AM signal (could be radio, could be analog tv to some degree). We consider the signal useful if we can demodulate it so we can hear or see it's content.

This content requires quite some bandwidth and hence brings noise.

If you just want to establish if the signal is there or not, regardless of any content, you can use a very narrow bandwidth. Instead of needing say 8 kHz for AM radio, you could use 1 uHz (i.e. integration time of 1.000.000 seconds).

This works as long as you can continously see the source (an omnidirectional one or a 'lighthouse' type signal that keeps hitting the same spot) and are not moving to or from it, or compensate for that. Lowering the bandwidth that far boosts your S/S+N ratio by about 70 dB but you can still establish the signal is -not noise-.

This is not magic, theory fully supports doing it, but the practical side can be difficult.

Still, lowering the bandwidth works in practical ways: you can get a lot more range from a given transmitter + signal path loss using morse code than voice modulation, albeit it at much lower information speed.
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Old 07-20-2016, 07:30 PM #299
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Default Re: Space Discussion Thread

Anyway, the point is that determining if an extraterrestrial radio signal is from an intelligent source is always going to be very difficult unless the source is very close, directly intended for us, and/or extremely powerful.

My original point is that you're almost certainly not going to pick up any transmitted data even if the source was something like extraterrestrial communications (TV, internet, phone, etc.). What we might be able to find are quiet little tidbits above noise of a signal that follows an intelligent pattern of modulation.

More people working on a radio astronomy experiment like this helps to identify these little signals amongst massive amounts of data. There's a lot of stuff in the radio sky that jumps above the noise floor irregularly and might look like a transmission. Most of it is completely natural though, so it's not a trivial task at all.

For anybody interested, SETI (Search for extraterrestrial intelligence) is the largest legitimate organization for identifying this sort of extraterrestrial radio activity. You can help identify signals by lending your computer's idle time to process a bit of their massive amount of calculations.
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Read more on helping out here: About SETI@home
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Old 07-20-2016, 10:31 PM #300
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Default Re: Space Discussion Thread

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Originally Posted by Rivem View Post
For anybody interested, SETI (Search for extraterrestrial intelligence) is the largest legitimate organization for identifying this sort of extraterrestrial radio activity. You can help identify signals by lending your computer's idle time to process a bit of their massive amount of calculations.
SETI Website
Read more on helping out here: About SETI@home
Ok, now that is very cool & I didn't even know about it! Thank you! + rep

Edit: Gotta spread some.

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Last edited by Hap; 07-20-2016 at 10:32 PM. Reason: Whoops, need to spread.
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Old 07-20-2016, 10:47 PM #301
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Default Re: Space Discussion Thread

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Ok, now that is very cool & I didn't even know about it! Thank you! + rep

Edit: Gotta spread some.

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They used to have a screensaver that showed you all sorts of funky graphics as it processed stuff in the background - not sure if they still have that. I remember my Dad running it when I was a kid - still remember sitting watching it on the CRT.

There's a whole bunch of other crowd sourced computing projects too: https://boinc.berkeley.edu/projects.php
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Old 07-20-2016, 11:37 PM #302
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Default Re: Space Discussion Thread

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Even if our radio emissions have reached other inhabited systems, they would be well into the noise floor by that point. Unless some alien race has a probe rather close by that can still pick out the signals from background noise I don't imagine anyone/thing has detected us - at least not from just radio emissions.

Unless they've come up with some clever way to pull signals out of the noise floor that we've yet to discover - higher gain detectors don't help pull signals out of the noise, they just make the noise louder...
This is complete nonsense, just within 100 light years there are about 512 stars, not including white dwarf stars. Within 50 light years if we count just the ones visible to the naked eye from earth they number 133. I have been listening to Seth Shostak on the radio for many years now and he thinks we can detect artificial signals at more than 1000 light years even with our primitive technology. So do the Chinese with their worlds largest radio telescope they are just finishing. They even relocated 9000 people so they could build it there, paying them each the equivalent of $1500 or $1800 to relocate.

If you don't know who Seth Shostak is, he is an astronomer, currently the Senior Astronomer and Director of the Center for SETI Research.

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Old 07-20-2016, 11:58 PM #303
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Default Re: Space Discussion Thread

One issue is that we still don't really know how long a planen would emit detectable signals. On earth it's been 100 years or so and is now rapidly coming to an end. Things like high power analog tv transmissions are rapidly being phased out, and fm radio stations usually are less powerful now servicing smaller areas (and being phased out for digital systems as well).

This shift from analog to digital is very important. Most digital modulation schemes spread the information over a fairly wide piece of spectrum. Also the information is encoded, sometimes encrypted, making it hard or impossible to decipher or even detect unless you know what you are looking for.

If other planets evolve similarly the window to detect one could be 150 years or so.

Also it's not unthinkable that some planets will skip/omit the whole high power transmission phase, perhaps because they live closer together and use wired or low powered systems, or skip analog and start with digital modes directly.

How often this would happen is guesswork, but it does impact chances of 'seeing' some society even if it is very close by.
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Old 07-21-2016, 12:02 AM #304
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Default Re: Space Discussion Thread

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This is complete nonsense, just within 100 light years there are about 512 stars, not including white dwarf stars. Within 50 light years if we count just the ones visible to the naked eye from earth they number 133. I have been listening to Seth Shostak on the radio for many years now and he thinks we can detect artificial signals at more than 1000 light years even with our primitive technology. So do the Chinese with their worlds largest radio telescope they are just finishing. They even relocated 9000 people so they could build it there, paying them each the equivalent of $1500 or $1800 to relocate.

If you don't know who Seth Shostak is, he is an astronomer, currently the Senior Astronomer and Director of the Center for SETI Research.

Alan

I didn't say we couldn't detect signals from them - for all we know they could be using incredibly powerful radio transmitters which they use to systematically transmit to different star systems with in the hopes of receiving a reply.

What I said was they wouldn't receive much, if anything from us. The majority of our transmissions A) aren't powerful enough or B) aren't directional (thus the signal "weakens" faster). Keep in mind while our radio bubble may extend ~100 light years - powerful, higher frequency, directed transmissions didn't start being common until later than that, and even then chances of someone catching one powerful enough for any length of time are very slim.

About the only transmission that has much of a chance at actually conveying much information at any reasonable distance is the Arecibo Message sent in 1974 - which was very directional (aimed at a star cluster 25,000 light years away - so it'll be a while before it gets to it's intended destination) and has "only" propagated some 40 light years. That transmission lasted for ~3 minutes - further reducing the chance of it ever being detected unless someone is specifically watching this direction continually. Even if it had propagated for 100 light years it'd miss most if not all of the 512 stars you mentioned.

So my point stands, I highly doubt anyone/anything has detected us yet.
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