Progarchives.com Homepage
Forum Home Forum Home > Topics not related to music > General discussions
  New Posts New Posts RSS Feed: The UFO Phenomenon
  FAQ FAQ  Forum SearchSearch  Calendar   Register Register  Login Login

The UFO Phenomenon

 Post Reply Post Reply Page  <1 212223
Author
Message
dr wu23 View Drop Down
Forum Senior Member
Forum Senior Member
Avatar

Joined: August 22 2010
Location: Indiana
Online Status: Offline
Posts: 4094
Post Options Post Options   Quote dr wu23 Quote  Post ReplyReply Direct Link To This Post Topic: The UFO Phenomenon
    Posted: June 29 2014 at 14:27
Originally posted by Toaster Mantis

One step closer to finding extraterrestrial life? Not quite, but still... meanwhile, the philosophical blogger Scott Alexander ponders why we haven't encountered any alien civilization yet. He doesn't really find any satisfactory answer, though as usual the comments section is worth reading since for reasons I don't quite grasp that particular blog attracts some very strange if always erudite commenters. I know SETI technically isn't the same thing as ufology but there's a bit of overlap in field of interest and the two are certainly relevant to each other.
http://en.wikipedia.org/wiki/The_Fermi_Paradox
one possible answer

Edited by dr wu23 - June 29 2014 at 14:28
Et In Arcadia Ego
Back to Top
dr wu23 View Drop Down
Forum Senior Member
Forum Senior Member
Avatar

Joined: August 22 2010
Location: Indiana
Online Status: Offline
Posts: 4094
Post Options Post Options   Quote dr wu23 Quote  Post ReplyReply Direct Link To This Post Posted: June 29 2014 at 14:35
Originally posted by Toaster Mantis

Maybe I should start a second thread for SETI? (Search for Extra-Terrestrial Intelligence) I gotta wonder if the association with UFOlogy does not exactly give that endeavour a most serious image... though it might kind of endear SETI to the general public.
 
I doubt if those who don't take the ufo phenom seriously on any level think much of SETI either.
But then Seth Shostak who was the main SETI man doesn't think much of the ufo phenom. But Michu Kaku does think aliens are out there and may have been here....go figure.
Wink
 
Et In Arcadia Ego
Back to Top
Toaster Mantis View Drop Down
Forum Senior Member
Forum Senior Member
Avatar

Joined: April 12 2008
Location: Denmark
Online Status: Offline
Posts: 4320
Post Options Post Options   Quote Toaster Mantis Quote  Post ReplyReply Direct Link To This Post Posted: June 30 2014 at 02:52
Last time I checked SETI received a lot more positive attention from the scientific community than ufology, perhaps for the reason that a lot of ufology is more religious or folkloric in character than scientific. I've already mentioned the continuity between Theosophy and the UFO contactee movement, then of course there's the alien abduction mythology's similarity to historical demonology or pre-Disneyfication faerie changeling stories.
Rejecting heaven, spurning the high ground, they stood in the way of demons and damnation... defending themselves alone.
Back to Top
Atavachron View Drop Down
Special Collaborator
Special Collaborator
Avatar
Honorary Collaborator

Joined: September 30 2006
Online Status: Offline
Posts: 47819
Post Options Post Options   Quote Atavachron Quote  Post ReplyReply Direct Link To This Post Posted: June 30 2014 at 02:58
if there were alien ships or probes near Earth, wouldn't they give off some kind of signal that SETI would pick up ? (I assume it ignores satellite transmissions)
"Too often we enjoy the comfort of opinion without the discomfort of thought."   -- John F. Kennedy
Back to Top
Dean View Drop Down
Special Collaborator
Special Collaborator
Avatar
Retired Admin and Amateur Layabout

Joined: May 13 2007
Location: Albion
Online Status: Offline
Posts: 32798
Post Options Post Options   Quote Dean Quote  Post ReplyReply Direct Link To This Post Posted: June 30 2014 at 03:32
Originally posted by Atavachron

if there were alien ships or probes near Earth, wouldn't they give off some kind of signal that SETI would pick up ? (I assume it ignores satellite transmissions)
SETI isn't looking close-range (even they realise there is little point in doing that). If there were aliens near Earth emitting electro-magnetic radiation of any kind we would have readily detected it somewhere in the EM spectrum without even looking for it.


If you cannot be wise, pretend to be someone who is wise and then just behave like they would - Neil Gaiman
Back to Top
Dean View Drop Down
Special Collaborator
Special Collaborator
Avatar
Retired Admin and Amateur Layabout

Joined: May 13 2007
Location: Albion
Online Status: Offline
Posts: 32798
Post Options Post Options   Quote Dean Quote  Post ReplyReply Direct Link To This Post Posted: June 30 2014 at 04:13
I have attempted to explain this before, but it is worth repeating.

All forms of EM radiation are subject to the Inverse Square Law
This means that signals from astronomical distances have to be phenomenally powerful at their point of origin for us to be able to detect them. Weak signals, and even powerful ones from distant stars, are lost in the Cosmic Microwave Background radiation, even to the most sensitive radio receivers we can build - no amount of signal processing can recover those signals.

If you consider the amount of EM radiation emitted by a star of the same magnitude as our Sun is in the order of 384.6 yotta watts (3.84610^26 W) then radio signals at interstellar distances would need to [be] of similar power levels for us to detect them. The Andromeda Galaxy has 1 trillion stars and that appears as a faint smudge to the naked eye - such is the effect of the Inverse Square Law.


Edited by Dean - June 30 2014 at 04:42


If you cannot be wise, pretend to be someone who is wise and then just behave like they would - Neil Gaiman
Back to Top
dr wu23 View Drop Down
Forum Senior Member
Forum Senior Member
Avatar

Joined: August 22 2010
Location: Indiana
Online Status: Offline
Posts: 4094
Post Options Post Options   Quote dr wu23 Quote  Post ReplyReply Direct Link To This Post Posted: June 30 2014 at 10:26
Originally posted by Atavachron

if there were alien ships or probes near Earth, wouldn't they give off some kind of signal that SETI would pick up ? (I assume it ignores satellite transmissions)
Not if they have that darn Star Trek shielding.
 
Wink
Et In Arcadia Ego
Back to Top
Dean View Drop Down
Special Collaborator
Special Collaborator
Avatar
Retired Admin and Amateur Layabout

Joined: May 13 2007
Location: Albion
Online Status: Offline
Posts: 32798
Post Options Post Options   Quote Dean Quote  Post ReplyReply Direct Link To This Post Posted: July 02 2014 at 11:54
Another factor affecting what SETI can detect is the simple observation that space is not empty. 

All the objects floating around in space can affect the path of an EM wave such as a radio signal or light emitted from a star. Big stuff such as galaxies, nebula and stars; medium size stuff like planets, moons, asteroids, meteors, comets, satellites, space craft, space junk and the small stuff such as dust, ice crystals, gas molecules, stray atoms and subatomic particles can all affect the passage of a signal to our receivers.

Space is not a perfect vacuum, even interstellar space has a density of a few hydrogen atoms per cubic metre and also contains dust and other space debris from exploding stars. While this ultra-low density at first seems insignificant, and indeed it is when we are considering transmission of radio waves only a few thousand kilometres, it does become significant when the distances involved are measured in light-years. This is because the mathematical formula that describes the losses is an inverse exponential power law (this is like the inverse square law of geometric spreading I mentioned earlier but much worse), so EM radiation is attenuated exponentially when it passes through a medium, even when that medium is interstellar space. Like the inverse square law that's a fundamental and immutable factor of the Universe. If this never happened we'd have full 100% 5-bar cell-phone coverage anywhere on Earth. While the density of space is small in comparison to Earth's atmosphere, the distances involved in interstellar 'communication' are astronomically huge ... at this scale low density and long distance is equivalent to high density and short distance. Therefore the total attenuation that is attributed purely to distance involves both the inverse square law and the exponential attenuation of the space it is passing through. Big distances = lots of attenuation - too much attenuation and we cannot receive it, it will be out of the range of our receivers. If you can travel a few meters and be out of WiFi range or a few kilometres and be out of range on your cell-phone, imagine the effect of travelling a few light-years on an interstellar radio source.

Having traversed the vast distances of space, the EM waves then have to contend with the Oort Cloud, the Heliosphere and all the other space debris that orbits our Sun before entering the significantly attenuating Earth's atmosphere. In all probability those signals would have passed though a similar miasma of energy-draining local space stuff when leaving the extraterrestrial solar-system it originated from.

Those who are lucky enough to live in regions of low light pollution can look up into the night sky and see the Milky Way. Since we are on the outer rim of the the galaxy as we look towards the constellation of Sagittarius we are looking at the centre of the galaxy edge-on and in our field of vision are the majority of the 400 billion star that the galaxy contains.

Yet running though this is a dark vein that astronomers call the Great Rift, this is a misnomer since it isn't a gap in the Milky Way that we can see through to deep space but a band of dust and plasma roughly 300 light years away between us and the galactic centre that is blocking the light. We can "see" through this with radio telescopes but the dust attenuates those frequencies of EM waves too and still absorbs/blocks the weaker ones. Why this obscures such a large area of the Milky Way is simply a matter of geometry and trigonometry - it is 300 ly away and the galactic centre is 27,000 lys away therefore the area it obscures at that distance is 90 times larger than the Rift itself.

[The vast distances involved cannot be stressed enough - it is incredibly difficult to comprehend how far these distances are because we have no frame of reference for distances that large - the 4.24 light years to Proxima Centauri is a stupidly huge, mind-boggling distance - 40,113,368,000,000km (24,924,839,194,400miles) - that's the same as circumnavigating the Earth 1,000 million times - it would take the Space Shuttle 163,429 years to fly to Proxima. Yet both these examples are just as incomprehensible - we can no more imagine what 163,429 years is like than we can imagine what going around the Earth 1 billion times is like - there is nothing in our experience that can allow us to picture a journey of 40 million-million kilometres. Even travelling at light-speed still takes 4.24 years to cross the space between Proxima and here - a lot can happen to a travelling wave of Electro-Magnetic radiation in 4.24 years.]

EM radiation in the form of radio waves and light waves travels in straight lines. In Earth-bound radio communication we call this "line-of-sight. On a planet such as ours with a complex, layered atmosphere some of the lower frequency radio waves can bounce off the layers in the atmosphere so can be detected beyond the horizon, but in general, for things like cell-phones and satellite tv if the receiver cannot "see" the transmitter then it doesn't receive the signal. Space does not have a complex, layered atmosphere to bend and bounce EM radiation - it can bend it slightly by the process of gravitational lensing, but that requires a massive gravitational source such as a galaxy cluster, a black hole or a quasar to act as a lens but they are relatively rare and only allows us to see very distant objects beyond our galactic neighbourhood. So to generalise again - for most of the radiant objects in the Universe, and all those within our own galaxy, if there isn't clear line-of-sight between them and the receivers here on Earth we are not going to be able to detect them.

[Proxima Centauri is interesting because it is our nearest stellar neighbour, other than that it is pretty uninteresting - as far as we can tell it has no planets, and due to its size and composition that is not a surprise - it's a small and weak red dwarf and even though it is the closest star to our own Sun it is so faint in the night sky we cannot see it without using a telescope. Red dwarves are pretty uninteresting in general - their fusion reaction just makes helium that circulates freely with the hydrogen fuel and does not produce a denser helium core, which means it can never produce the heavier elements such as carbon, nitrogen and oxygen or any of the other elements in the periodic table up to and including iron. The hydrogen-helium reaction process is very slow and very stable and lasts for trillions of years - they don't explode as novas and they don't rapidly collapse or expand - essentially the only way for a red dwarf that was formed during the past 13 billion years not to exist now is for it to have crashed into something else, such as another star or a black hole. There are however two quite interesting things about red dwarves - the first is there are a hell of a lot of them - it is estimated that 85% of the stars in the Milky Way Galaxy are red dwarves; and the second is (as I've already intimated) that they are small and produce very little light so we cannot see them with the naked eye. This means that 85% of the stars in our galaxy do not produce enough light to be seen by an observer on Earth looking up into the night sky]

Of the 400 billion stars in the galaxy only 15% (60 billion) of them emit enough light to be seen with the naked eye here on Earth. Many of those are obscured by the Great Rift and many more are blocked by each other because we are looking through the width of the galaxy - for example we do not have clear line-of-sight to all the stars on the far side of the galaxy (which would be the delta quadrant in Trekkie-speak) because all the stars between us (in the alpha quadrant) and the galactic centre obscures them. The same is true when we look in any other direction, we do not have clear line of sight to every potentially visible star in the galaxy (in any quadrant, even our own alpha quadrant) so we cannot receive light or radio signals from them either.

We can see some obscured stars, nebula and galaxies as we orbit the Sun due to the parallax effect - as our position in space moves we can peek behind a star to see what it has obscured, but because of the relatively short distance we move in space compared to the distance to that blocking-star we can only see objects that are significantly further away from the star than we are from that star itself (again, simple trigonometry). This we know because the position of the stars and the shapes of the constellations do not change dramatically as we orbit the Sun, the apparent changes in position are small and allow us to measure the distance to the stars (more trigonometry) but it doesn't reveal a large number of otherwise hidden stars to us.

All of this limits what SETI can possibly detect in its search for extraterrestrial radio sources, this is before we consider whether those radio signals are natural or not and whether those that may be artificial are created by an extraterrestrial intelligence deliberately or by accident or are the result of an as yet unknown natural phenomena (which was the case with pulsars). This doesn't make the search futile, it merely lowers expectations and makes the Fermi Paradox a little less paradoxical.


If you cannot be wise, pretend to be someone who is wise and then just behave like they would - Neil Gaiman
Back to Top
Atavachron View Drop Down
Special Collaborator
Special Collaborator
Avatar
Honorary Collaborator

Joined: September 30 2006
Online Status: Offline
Posts: 47819
Post Options Post Options   Quote Atavachron Quote  Post ReplyReply Direct Link To This Post Posted: July 03 2014 at 00:02
Originally posted by Dean

Since we are on the outer rim of the the galaxy as we look towards the constellation of Sagittarius we are looking at the centre of the galaxy edge-on and in our field of vision are the majority of the 400 billion star that the galaxy contains.

 - Is this better than being toward the center, or would a panorama view be more comprehensive (if daunting to observe)?

Originally posted by Dean

it would take the Space Shuttle 163,429 years to fly to Proxima - we can no more imagine what 163,429 years is like than we can imagine what going around the Earth 1 billion times is like

 - Actually that's not bad; that's the one number I can wrap my head around.






Edited by Atavachron - July 03 2014 at 00:16
"Too often we enjoy the comfort of opinion without the discomfort of thought."   -- John F. Kennedy
Back to Top
Dean View Drop Down
Special Collaborator
Special Collaborator
Avatar
Retired Admin and Amateur Layabout

Joined: May 13 2007
Location: Albion
Online Status: Offline
Posts: 32798
Post Options Post Options   Quote Dean Quote  Post ReplyReply Direct Link To This Post Posted: July 03 2014 at 03:31
Originally posted by Atavachron

Originally posted by Dean

Since we are on the outer rim of the the galaxy as we look towards the constellation of Sagittarius we are looking at the centre of the galaxy edge-on and in our field of vision are the majority of the 400 billion star that the galaxy contains.

 - Is this better than being toward the center, or would a panorama view be more comprehensive (if daunting to observe)?
The night sky would be brighter and while it seems a contradiction we could possibly see less stars as a result. This is because our eyes would not become fully dark-adapted (this is not just the iris fully opening, there are chemical changes in the rods and cones that make them more sensitive, which it why it takes time to become dark-adapted), an example of this effect is we see fewer stars when the Moon is up. A bright night-sky would also cause the atmosphere to glow, just as it does when light from the nearest star to us is scattered through the atmosphere - we can't see stars in the day time,

We also have evidence of this from the Moon landings - there are no stars in the any of the photographs because they were taken during the day when the Sun (and often the Earth) were visible in the sky.


Originally posted by Atavachron


Originally posted by Dean

it would take the Space Shuttle 163,429 years to fly to Proxima - we can no more imagine what 163,429 years is like than we can imagine what going around the Earth 1 billion times is like

 - Actually that's not bad; that's the one number I can wrap my head around.




The number yes, but the time span? I doubt it. 

160,000 years ago the human species had not left Africa, most of Europe was frozen and megafauna dominated the planet (this is during the penultimate Ice Age ... ie not the one from the popular animated film).


If you cannot be wise, pretend to be someone who is wise and then just behave like they would - Neil Gaiman
Back to Top
 Post Reply Post Reply Page  <1 212223

Forum Jump Forum Permissions View Drop Down

Bulletin Board Software by Web Wiz Forums® version 9.69
Copyright ©2001-2010 Web Wiz

This page was generated in 0.141 seconds.