Wednesday, October 29, 2014

The Long Delay Echoes

The subject here is a scientific mystery that was well documented by European scientists in the 1920s and 1930s, well before any man made objects were launched into outer space, and then was largely forgotten. The phenomenon has since apparently disappeared, although anecdotal reports still pop up from time to time, and a low level of interest persists. We are discussing it here, because although no one knows for sure what caused the Long Delay Echoes, one plausible explanation is Bracewell Probes. The Long Delay Echoes (LDEs) just possibly might be a clue to how to find such a probe.

Some Basic Background You may Wish to Skip

 I'm sure you know that radio waves generally travel at the speed of light, and can be bounced off of various surfaces and also off the Earth's ionosphere is the radio wavelength is long enough. The speed of radio waves can be a bit slower if they are traveling through a medium such as a plasma or water, but generally the speed is not much less than the 300,000 kilometers per second we are used to. That means, if we send a radio signal out, and see it come back to us, then to calculate the distance to the reflector, we divide the time delay in seconds by 2 (since it went out and back), and then multiply by 300,000 kilometers per second to get the distance. Then, if we send out a radio signal and it comes back 2 seconds later, it must have traveled 300,000 km each way, or most of the way to the Moon. Amateur radio operators often enjoy bouncing their signals off the moon, which generally exhibits a very weak echo delayed about 2 and one half seconds. Strong echoes, or echoes delayed longer than 2.5 seconds, are not moon echoes.

Since the 1960s, there are many radio repeaters in Geosynchronous orbit, but the round trip delay is much shorter than the moon -  less than half a second, and you generally won't see a satellite echo at all unless your signal parameters are just right - and probably illegal.

The Long Delay Echoes

In the 1920s, with radio technology beginning to really develop rapidly, there was a great deal of
Van der Pol
interest in how radio waves propagated. Scientists and radio enthusiasts alike were making measurements to try to understand how radio waves were affected by the Earth, the Sun and the upper the atmosphere. At this point, everyone knew that if you sent out a strong radio signal, you would get a faint echo 1/7 th of a second later as it bounced around the planet.

The LDEs were first noted in 1927 by an early amateur radio operator named Jorgen Hals in Norway. He brought this to the attention of professional scientists. In October of 1928, Hals, Stoermer and Van der Pol observed LDEs on the 9.5 MHz frequency ranging from 3 to 30 seconds.  Now, as noted above, 3 seconds is a bit longer than a moon echo could be, and 30 seconds is far longer. Further experiments were carried out, and Hals observed an echoes as long as 260 seconds. These signals weren't bouncing off astronomical objects, such as the moon or Mars, and they didn't have the shift in frequency due the Doppler effect you would expect if the were reflections from the Solar Wind (moving at roughly 1/1000 the speed of light).

After the war, some interest in the LDEs returned, and more observations were made. Budden and Yates conducted a long series of experiments at shorter wavelengths, but observed no LDEs.

In 1960, Ronald Bracewell published his famous paper about alien probes in our solar system, speculating that the Long Delay Echoes may have been transmitted by such a probe as a way of announcing its presence.

In the late 1960s and 1970s scientific interest in the echoes peaked, as documented by Volker Grassman in his excellent survey paper. A number of amateurs report LDEs in the 1960s, with delays up to 10 seconds. Stanford University got involved in the late 1960s. They recorded several LDEs, and by 1971 had seen one as long 31 seconds.

Two things are certain about LDEs: they are not reflections from astronomical bodies, and they are not echoes from man made satellites. Beyond that, the question remains open. We can't just jump to the conclusion we want, that Bracewell's speculation was correct.

Are there natural explanations for the LDEs? Some work has been done on that, and it turns out that under ideal and fairly delicate conditions, some of the echoes observed might be a result of complex plasma physics in the Earth's ionosphere. The ionosphere is actually multiple layers of the Earth's upper atmosphere where some free electrons are found. A phenomenon known as a plasma wave does exist, and it propagates much more slowly than the speed of light. We know that plasma waves are real from both satellite and radar observations, but it takes special conditions for the wave to be stimulated by radio transmissions and then to grow strong enough to result in an echo.

There may be other natural explanations for LDEs, but just not enough work has been done to nail them down. A combination of theoretical modeling and experiments over many years is usually what it takes to nail these things, and not surprisingly, it hasn't been a scientific priority for space physicists. However, as our understanding of the Earth's plasma environment improves, and modeling tools get better, it might get easy enough to be worth a try.

If we could do the above (and it may take some amateur radio work to observe the echoes), what if
Duncan Lunan
we find that the echoes are still there, and natural explanations still fail? Does that mean we're now hunting for Bracewell Probes? People like Duncan Lunan have attempted to understand the LDEs in terms of a message from a Bracewell Probe. Someone has to be brave and try this, but frankly I think it's premature. It's not completely clear to me that we can scientifically study Bracewell Probes, but I think we should try as best we can.

Should we try and look for evidence of these radio-echoing probes at Earth-Moon Lagrange Points L4 and L5? Can we pinpoint a source for the LDEs? Good questions all. I say lets go and try to find out. What do you think?

Saturday, August 30, 2014

I should post more often, I know..

The trick is how to divide time between podcasting and blogging - time that is left over after work, Krav Maga, domestic chores and family time. Not to mention, the European club football season has started up again and some other projects are in the works...

Anyway, there should be a burst of blog activity soon as the podcasting season winds down at the end of November. We have a four person team working on the Wow! Signal now, and the intent is that this bears fruit in terms of more and better episodes, some of which will have little, if any, involvement by me. I want to write about the Long Delay Echoes soon, and I will also have an interview with Duncan Lunan on the podcast on that very topic.

As for API Case Files, the plan is to get that completely independent of me in the long run, except for my few minutes of Unidentified Science in each episode. I really enjoy doing Unidentified Science, and it is helping me to connect with like minded people all over the place. I hope you will listen.

Wednesday, May 7, 2014

The Fermi Paradox, Part 2

In my first post on the Fermi Paradox, I went over the basics, which I expect most readers are familiar with anyway. It can be summed up simply (perhaps over-simply) as:
  • Our galaxy is plenty old enough for at least one advanced civilization to have completely colonized it by now, even at speeds much slower than the speed of light.
  • "Completely colonized" should include our solar system.
  • No one can make a persuasive case that this has happened.
 So, the simple version is: they should be be here, but they aren't. This presents us with a paradox.

I'd bet that some readers already have a few objections to the above, and over the next few posts we will take this apart and see where reasonable doubt lies.  This is the real value of the paradox: it serves as superb mental lens that makes us question our assumptions. It should make us more humble about our understanding of how the universe works, and spur us into deeper research. The great unknown is great indeed, so let's go explore. The forward path for the human adventure could not be clearer, and one of the best signposts is the Fermi Paradox.

Sadly, this is not the only effect it has. Too many seize on the Fermi Paradox to jump to Grand Conclusions not in evidence. I promise not to do that. Instead, we will look for better questions than "where is everybody?" I haven't found one yet, but I see hope.

Wednesday, January 22, 2014

The Case for the Wow! Signal

I recommend Robert Gray's book The Elusive Wow! if you want detailed background on the Wow! event of August 15th 1977. The book also describes the author's efforts to replicate the signal. To date, no one has reported a reliable second detection of the Wow! Signal, although efforts to find it have not been persistent.

The Wow! Signal was a single 72 second event detected by the Big Ear radio telescope operated by Ohio State University, which was sweeping past the constellation Sagittarius at the time. This telescope was designed to conduct a survey of the radio sky, not to study individual sources in detail. The survey was successful and a number of new radio sources were discovered. After that, some of the science team thought that a SETI search would be a good use of the telescope.

I think the case against the Wow! Signal as an ET beacon is well known.

We are all well aware of the fallacy of the argument from ignorance. Just because the Wow! Signal has not been proven to be from a known source doesn't mean it's from ET. It's possible that the Wow! Signal was some sort of strange problem with the Big Ear's receiver that only occurred once, or that it was an extraordinarily elaborate and strenuous hoax. For these reasons, you would need to see independent confirmation, and we haven't; Robert Gray's single-handed and largely self-funded efforts to do so have been far from comprehensive.

Since the Wow! Signal was discovered after the fact, when Jerry Ehman went through a stack of printouts, it was too late to get another radio telescope to break off what it was doing, swing over and confirm the signal.  The signal was never confirmed, and no similar signal has been found in that region of space.

The are multiple reasons we think that the Wow! Signal may have been an ET beacon.

Tuesday, December 31, 2013

Where I am on the Drake Equation at the end of 2013

I'm sure you are all familiar with the Drake Equation. It's straightforward: SETI scientist Frank Drake devised it as a way to estimate the number of alien civilizations in our galaxy that we might be able to detect. It's only intended to be a rough guide, and has survived the last 50 odd years because it serves as a good way to divvy up the questions we will need to resolve to answer the bigger question, "Are we alone"?

There are many fine explanations of the terms of the Drake Equation easily available to you, so I won't repeat them. Here are few:

This is how the equation is usually written:

N = R* • fp • ne • fl • fi • fc • L

As we move from left to right across the equation, the terms become less and less well known and harder to estimate, even when we know more. The only thing we're sure of with some of the terms is that none of them are zero, since we are here.

In the last few years, there has been progress. We have gone from knowing just the first term with any kind of accuracy ( a factor of 2 or so), to having solid estimates of the first three terms, and we can now begin to conceive of a research program that would give us an estimate of the fourth term.

Remember, we are only interested in rough numbers here: we just want to know, is N a lot or a little?

So, for 2013, I think we are here: