The Wow! Signal After 45 Years

Cool Worlds
18 Jun 202227:30

Summary

TLDRفي عام 1977، رصدت مرصد بيج إير في ديلاوير، أوهايو، إشارة راديوية غامضة وقوية من اتجاه كوكبة القوس، عُرفت لاحقًا بإشارة 'واو'. لم يكن هناك أحد في غرفة التحكم ليراقب الحدث مباشرة، لكن الإشارة تم تسجيلها على شريط طباعة بواسطة كمبيوتر IBM 1130. الإشارة، التي تميزت بنسبة عالية من الإشارة إلى الضوضاء، وترددها القريب من خط الهيدروجين، وطبيعتها الضيقة النطاق، واستمراريتها، ظلت محور اهتمام وتكهنات العلماء والهواة على حد سواء. على الرغم من الجهود المكثفة لإعادة رصدها، لم تتكرر الإشارة مرة أخرى، مما أدى إلى تكهنات حول مصدرها، سواء كانت طبيعية أو صناعية، وما إذا كانت دليلاً على وجود حضارات فضائية.

Takeaways

  • 🌟 45年前在俄亥俄州特拉华市的一个夏日傍晚,发生了一件非凡的事情。
  • 🚀 来自人马座方向的一束强烈且连续的窄带无线电波,被一个30米高的平面反射器反射向天空。
  • 💻 信号最终被一台IBM 1130计算机接收并放大,在控制室内被打印出来。
  • 🌌 著名的'Wow信号'是由志愿者Jerry Ehman在审查打印材料时发现的,他用红笔圈出了这个信号。
  • 📡 'Wow信号'的四个观测事实使其成为外星无线电传输的最有力候选者:高信噪比、特定频率、窄带特征和持续的本性。
  • 🔍 信号的频率几乎精确地等于1420MHz,也就是氢线频率,这是宇宙中最简单的原子的最基本电子跃迁引起的发射。
  • 🚦 'Wow信号'的窄带特性非常不寻常,自然中我们不知道有任何无线电源能做到这一点。
  • 🕒 信号在72秒的观测期间似乎是连续的,这是由于地球的旋转使得观测站在这个时间内扫过天空的这个区域。
  • 🔄 尽管进行了多次尝试重新观测,但'Wow信号'再也没有被检测到,这使得人们难以确定其来源和性质。
  • 📊 通过统计分析,即使在考虑了后续观测数据后,'Wow信号'仍有可能是一个真实的、重复的信号,其概率约为1/50。
  • 🌠 'Wow信号'仍然是一个谜,但通过更多的观测和分析,我们可能最终能够解决这个谜团。

Q & A

  • ال哇 الصوت ما هو؟

    -الوا الصوت هو تصوير радиоي قوي ومنتظم شحن من الفضاء الخارجي لمستشعر به في عام 1977 من قبل مراقبة الرأس العظيم Big Ear Observatory في أوهيو، وظل يظل هو المرشح الأكثر جاذبية للاتصال الفضائي من قبل البشر.

  • ما ال-four observational facts- يشيرون إليهم في النص؟

    -الأربعة حقائق المراقبة هي: ال第一位高比率 نoise-to-signal، ال第二位 التردد الخاص، الثالث النطاق الضيق للشارة، والرابع تظهر الصوت مستمرًا على 72 ثانية.

  • لماذا يشير التردد 1420MHz إلى ال頻率 اللازمة للاتصال؟

    -التردد 1420MHz يشير إلى ال頻率 اللازمة للاتصال لأنه يتوافق مع تصوير الذرة الهيدروجينية الأساسية في الكون، وهو التردد الأقل ضجيجًا في الفضاء، مما يجعله مواعيد للاتصال.

  • لماذا يشير إلى ال頻率 1420MHz للاتصال الفضائي المحتمل؟

    -التردد 1420MHz يشير إلى الاتصال الفضائي المحتمل لأنه يتوافق مع تصوير الهيدروجينية الأساسية في الكون، وهو التردد الأقل ضجيجًا في الفضاء، مما يجعله مواعيد للاتصال.

  • ماذا يشير الwah signal- إلى في الفضاء؟

    -الwah signal- يشير إلى ال可能性较大的外星无线电传输我们已经收到的最引人注目的候选者,但由于缺乏重复信号,这个谜仍未解决。

  • لماذا لم يتم العثور على الwah signal- مرة أخرى؟

    -لم يتم العثور على الwah signal- مرة أخرى لأسباب عدة، بما في ذلك القدرة المحدودة للمراقبة على ال repetitivity الصوت، والمكان المجهول للصوت، وعدم تكرارها في المراقبة اللاحقة.

  • ماذا يشير الwah signal- إلى في الفضاء؟

    -الwah signal- يشير إلى الاحتمالية الأكبر للاتصال الفضائي من قبل البشر، وهو المرشح الأكثر جاذبية للاتصال الفضائي من قبل البشر.

  • لماذا يشير الwah signal- إلى الاتصال الفضائي؟

    -الwah signal- يشير إلى الاتصال الفضائي لأن التردد الخاصة به يتوافق مع تصوير الهيدروجينية الأساسية في الكون، وهو التردد الأقل ضجيجًا في الفضاء، مما يجعله مواعيد للاتصال.

  • ماذا يشير الwah signal- إلى في الفضاء؟

    -الwah signal- يشير إلى الاحتمالية الأكبر للاتصال الفضائي من قبل البشر، وهو المرشح الأكثر جاذبية للاتصال الفضائي من قبل البشر.

  • لماذا يشير الwah signal- إلى الاتصال الفضائي؟

    -الwah signal- يشير إلى الاتصال الفضائي لأن التردد الخاصة به يتوافق مع تصوير الهيدروجينية الأساسية في الكون، وهو التردد الأقل ضجيجًا في الفضاء، مما يجعله مواعيد للاتصال.

  • ماذا يشير الwah signal- إلى في الفضاء؟

    -الwah signal- يشير إلى الاحتمالية الأكبر للاتصال الفضائي من قبل البشر، وهو المرشح الأكثر جاذبية للاتصال الفضائي من قبل البشر.

Outlines

00:00

🌌 Discovery of the Wow Signal

The first paragraph introduces the Wow signal, a strong narrow-band radio signal detected 45 years ago in Delaware, Ohio. It was picked up by a radio telescope and recorded by an IBM 1130 computer. The signal, with a high signal-to-noise ratio and a frequency corresponding to the hydrogen line (1420MHz), was found by volunteer Jerry Ehman, who circled the sequence 6EQUJ5 and wrote 'Wow'. Despite efforts to find a natural explanation, the signal remains a compelling candidate for an alien radio transmission.

05:01

🚀 Characteristics and Implications of the Wow Signal

The second paragraph delves into the unique characteristics of the Wow signal, including its high signal-to-noise ratio, specific frequency, narrow band signature, and continuous nature. The signal's frequency near the hydrogen line is significant as it's a natural quiet part of the spectrum and a wavelength hypothesized for alien communication. The narrow band nature of the signal is also intriguing as it's not found naturally. The signal's continuous observation for 72 seconds suggests it's not from a satellite or space debris, but the lack of repetition and the unknown origin leave room for skepticism.

10:03

🤔 The Mystery Surrounding the Wow Signal

The third paragraph discusses the mysteries and challenges in understanding the Wow signal. It highlights the unknowns, such as whether the signal was modulated, its origin, the fact that it was detected in only one horn, and its lack of repetition. The signal's detection in one of two horns that observe the same patch of sky three minutes apart raises questions about the timing of the signal's appearance. Despite extensive efforts to reobserve the Wow field, no recurrence has been detected, leaving the signal's nature undetermined.

15:04

📊 Statistical Analysis of the Wow Signal

The fourth paragraph presents a statistical approach to understanding the Wow signal. It introduces a new research paper that uses a responsive emulator of the Big Ear Observatory to simulate potential alien transmissions and determine the likelihood of detecting a signal like Wow. The analysis considers both periodic and random schedules for the hypothetical alien transmissions. It concludes that the Wow signal could still be a viable alien transmission, even after multiple unsuccessful attempts to detect it again.

20:07

🔍 Further Observations and Analysis of the Wow Signal

The fifth paragraph discusses further observations and analysis of the Wow signal. It mentions additional efforts using different radio telescopes and the accumulated observations since the original Big Ear data. The use of an emulator to include this new data reduces the probability of a random Wow signal matching all observations to about one in 50. The paragraph suggests that around 1500 hours of additional observing time could provide a conclusive answer to the nature of the Wow signal.

25:10

🌟 The Legacy of Robert Gray and the Future of the Wow Signal

The final paragraph pays tribute to Robert Gray, co-author of a new research paper on the Wow signal, who passed away during the writing of the paper. It acknowledges Gray's significant contributions to the study of the Wow signal and his book 'The Elusive Wow'. The paragraph concludes by highlighting the ongoing interest in the Wow signal and the hope that it may still be detected again, potentially resolving the mystery of its origin.

Mindmap

Keywords

💡Wow signal

The Wow signal is a strong, narrow-band radio signal detected in 1977 by astronomer Jerry Ehman, while he was working on a SETI (Search for Extraterrestrial Intelligence) project. It is named after the 'Wow!' that Ehman wrote on the computer printout when he discovered the signal. The signal's origin remains unexplained, and it has not been detected again, making it one of the most compelling candidates for a potential extraterrestrial radio transmission. In the video, the Wow signal is the central topic, with extensive discussion on its characteristics, possible explanations, and the ongoing efforts to understand its nature.

💡Signal-to-noise ratio

Signal-to-noise ratio (SNR) is a measure used in signal processing and telecommunications to compare the level of a desired signal to the level of background noise. It is expressed in decibels (dB) and a higher ratio indicates a clearer, more reliable signal. In the context of the Wow signal, a high SNR indicates that the signal was significantly stronger than the surrounding noise, suggesting it was not a random or natural occurrence. The video emphasizes the Wow signal's high SNR as evidence supporting its potential extraterrestrial origin.

💡1420MHz

1420MHz refers to the frequency at which the Wow signal was detected. This frequency, also known as the hydrogen line, is significant because it is the frequency at which a neutral hydrogen atom transitions between its energy levels. The hydrogen line is considered a likely frequency for extraterrestrial communication due to its universality and the relative quietness of space at this frequency. The Wow signal's frequency being close to the hydrogen line has fueled speculation about its possible artificial origin.

💡Narrow band

A narrow band refers to a small range of frequencies in the electromagnetic spectrum. In the context of radio signals, a narrow band signal has a limited frequency range, which is often indicative of artificial or controlled sources. The Wow signal's narrow band nature is one of its intriguing characteristics, as natural radio sources typically have broader frequency ranges. This feature of the Wow signal suggests that it could be a product of intelligent life, as opposed to a natural phenomenon.

💡Big Ear Observatory

The Big Ear Observatory is the radio telescope facility where the Wow signal was first detected. Located in Ohio, it was part of a SETI project scanning the sky for extraterrestrial radio signals. The observatory's unique configuration and the circumstances of the Wow signal detection are central to the discussion in the video, as they provide clues about the signal's potential origin and the challenges in detecting it again.

💡Doppler shift

The Doppler shift is a change in frequency or wavelength of a wave in relation to an observer who is moving relative to the wave's source. It is commonly associated with the change in pitch of a vehicle's engine as it approaches and then passes by. In the context of the Wow signal, a slight deviation from the expected hydrogen line frequency could be explained by the Doppler shift if the signal source was moving towards Earth. This concept is used in the video to discuss the possibility of the Wow signal being from a moving celestial body.

💡Statistical analysis

Statistical analysis is the process of analyzing data through the application of statistical methods, allowing researchers to draw conclusions based on data-driven evidence. In the video, statistical analysis is crucial in evaluating the likelihood of the Wow signal being a natural or artificial occurrence. The speaker uses statistical models to estimate the probability of the signal's properties and to determine how much more data would be needed to conclusively prove or disprove its extraterrestrial origin.

💡Alien transmission

An alien transmission refers to a hypothetical signal or message that is sent by an intelligent extraterrestrial civilization. The Wow signal is considered by some as a potential candidate for an alien transmission due to its unique characteristics that are hard to explain through natural phenomena. The video delves into the possibility of the Wow signal being an intentional or unintentional leakage of communication from an advanced civilization outside of Earth.

💡Jerry Ehman

Jerry Ehman is an astronomer who first discovered the Wow signal while working on a SETI project at the Big Ear Observatory. His role in the discovery and his subsequent analysis of the signal are central to the narrative of the video. Ehman's initial reaction to the signal, as indicated by his famous 'Wow!' scribble on the computer printout, reflects the significance and surprise of the signal's detection.

💡Robert Gray

Robert Gray was a data analyst and amateur astronomer who became one of the world's leading experts on the Wow signal. In the video, Gray's extensive research, his efforts to understand the Wow signal, and his collaboration with the speaker on a new research paper are highlighted. Gray's work and his dedication to unraveling the mystery of the Wow signal are commemorated in the video, especially following his tragic passing.

Highlights

45年前在俄亥俄州特拉华州的一个闷热夏夜,发生了一件非凡的事情。

来自人马座星座方向的强烈连续窄带无线电波,被一个30米高的平面反射器反射向天空。

无线电波随后被另一个抛物面反射器反射,导向两个检测喇叭之一,接收并放大信号。

在附近的控制室内,没有科学家或工程师观察这一刻,与好莱坞电影不同。

IBM 1130计算机在那个黑暗孤独的空间里,不停地工作并发出声响。

计算机打印输出落入托盘,折叠成随后页面的方式。

在那个页面上,无线电信号的不可否认的证据已经被永久记录。

技术员后来将打印输出送到志愿者Jerry Ehman的家中,他同意查看它们是否有有趣的内容。

Ehman用红笔仔细扫描各种数字,代表探测器接收到的信噪比。

当Ehman遇到6EQUJ5序列时,他意识到这是他见过的最高信噪比事件。

他本能地圈出这个序列,并写下了现在历史性的潦草字迹'Wow'。

Wow信号至今仍是我们收到的最引人注目的外星无线电传输候选者。

Wow信号的四个观测事实使其非常令人兴奋:高信噪比、特定频率、窄带特征和显然的连续性。

Wow信号的峰值强度比周围背景高30倍,排除了这是随机统计波动的可能性。

Wow信号的频率几乎精确地等于著名的1420MHz,也称为氢线。

Wow信号的窄带特性在自然界中是未知的,指向了人工发射器的可能性。

信号在72秒的观察期间似乎是连续的,这对于地球的旋转和观测站的扫描模式来说是正常的。

尽管进行了多次尝试重新观测Wow信号区域,但该信号再也没有被检测到。

新的研究论文通过深入统计分析Wow信号,尝试挤压数据以寻找答案。

通过创建一个响应模拟器模拟Big Ear和其他观测站的行为,研究者可以模拟假设的外星传输。

即使在考虑了后续观测数据后,Wow信号仍有1/50的概率是一个真实的重复信号。

大约需要额外1500小时的观测时间才能最终确定Wow信号是否为一个真实的天文源。

Wow信号的最可能属性表明,信号持续时间在2分钟到37小时之间,平均重复率大约每个月一次到每月12次。

尽管希望不大,但Wow信号可能仍然是一个真实的信号,等待被发现。

Wow信号的研究者Robert Gray对这个话题充满热情,他的去世对天文学界是一个损失。

Transcripts

00:01

(waves crashing)

00:08

(gentle instrumental music)

00:12

- 45 Years ago,

00:14

on a sultry, summer evening in Delaware, Ohio,

00:18

something remarkable happened.

00:21

From the direction of the Sagittarius constellation,

00:24

an intense and continuous narrow band radio wave

00:28

bounced off a 30 meter tall,

00:31

flat reflector tilted towards the sky.

00:33

It then bounced off another parabolic reflector,

00:36

funneling it towards one of two detection horns

00:39

that received and amplified the signal.

00:42

Within the nearby control room,

00:45

there were no scientists or engineers to watch the moment

00:48

like in a Hollywood film.

00:51

Instead within that dark and lonely space,

00:55

the only sound was out of a busy line printer

00:58

and IBM 1130 computer,

01:01

diligently worrying and chirping away into the night.

01:06

The computer printout fell into the tray,

01:08

folding into the way to the subsequent pages.

01:11

But upon that page,

01:13

the irrefutable evidence

01:16

of the radio signal had been immortalized.

01:19

Sometime later,

01:21

a technician dropped off the printouts

01:22

at the home of volunteer, Jerry Ehman

01:25

who had agreed to look through them

01:27

for anything interesting.

01:29

scouring through the pages,

01:31

Ehman would carefully scan through the various numbers

01:34

with his red pen.

01:36

Most of the time,

01:37

the numbers were small images

01:39

representing the signal-to-noise ratio

01:41

the detectors received.

01:42

Numbers greater than nine,

01:44

had to be represented as letters for 10,

01:47

B for 11 and so on.

01:49

And so when Ehman stumbled across the sequence 6EQUJ5,

01:56

he realized that he was looking

01:58

at the highest signal-to-noise event he'd ever seen.

02:03

Instinctively, he circled the sequence

02:06

and wrote the now historic scribble, Wow.

02:11

That happened in 1977 and despite four and a half decades

02:16

that have passed since,

02:17

the Wow signal remains the most compelling candidate

02:20

for an alien radio transmission we have ever received.

02:24

I've long been fascinated with the Wow signal,

02:28

like an irresistible itch.

02:30

I've often found myself dwelling on it at night

02:33

in quiet moments,

02:34

wondering what was it?

02:37

Who sent it?

02:38

And what else could be out there?

02:41

Radio signals are detected from the sky all the time

02:44

to such an extent that there's an entire field

02:47

of astronomy dedicated to mapping the sky in the radio.

02:51

But the Wow signal found by the Big Ear Observatory stands

02:55

out as being incredibly exciting

02:57

because of four observational facts.

03:01

Number one, it's high signal-to-noise;

03:05

Two, it's particular frequency,

03:08

three, it's narrow band signature,

03:11

and four, it's apparently continuous nature.

03:14

For fact one,

03:15

the high signal-to-noise is crucial

03:17

because it removes any doubt that this could be some kind

03:21

of random statistical fluctuation.

03:23

The peak intensity of the Wow signal was 30 times higher

03:27

than the ambient background.

03:29

So that means that the probability of a random fluctuation

03:32

doing this was one intent to the power of 196.

03:36

That's an astronomically tiny number.

03:40

The bigger observatory could run for a trillion years

03:43

and never expect to see a fluctuation like that.

03:45

Yet more the moments just before

03:47

and after the peak

03:48

also show exceptionally high signal-to-noise values.

03:52

So there's no way that we can legitimately ignore this

03:55

as some kind of statistical fluke.

03:56

For fact two,

03:57

the signal frequency was almost precisely equal

04:00

to the famous frequency of 1420MHz,

04:04

also known as the hydrogen line.

04:06

This is a special channel long hypothesized

04:09

to be a likely wavelength that aliens might use

04:12

to attempt to communicate with us

04:13

because of two major reasons.

04:16

First, the cosmos is naturally quietest

04:18

at this part of the spectrum.

04:19

So there's less noise to interfere with the communications.

04:23

And second,

04:24

the hydrogen line corresponds to the emission caused

04:27

by the most basic electronic transition

04:29

within this simplest atom in the universe.

04:33

Anyone in the cosmos who understands quantum physics

04:36

should know about this special frequency.

04:39

And so it serves as a Schelling point,

04:42

a rallying point in frequency space.

04:45

Now, it should be noted that the frequency

04:47

actually wasn't quite exactly equal to the Hydrogen line,

04:50

but instead was 50 kilohertz above it.

04:54

However, this slight difference is consistent

04:57

with a variation expected

04:58

due to the Doppler shift of a transmitter

05:00

that is moving towards the Earth

05:02

at a modest speed of order of 10 kilometers per second,

05:05

which is a fairly typical velocity for nearby stars.

05:08

For fact, number three,

05:10

we turned to the narrow band nature of the Wow signal,

05:14

but how do we know this?

05:16

While the Big Ear Observatory had 50 detector channels,

05:20

each one with a bandwidth of 10kHz.

05:24

The Wow signal was only recorded in one channel,

05:27

channel number two of the 50 possibilities,

05:30

which means that its power is limited

05:32

to within a 10kHz window or even possibly much smaller.

05:37

So given the frequency of 1420Mhz,

05:41

that means that the bandwidth divided by the frequency

05:45

is less than seven parts per million, incredibly narrow.

05:49

Now in nature,

05:49

we simply don't know of any radio sources that do this.

05:55

For example, the Crab pulsar is often referred to

05:58

as a natural narrow band radio source,

06:00

but there, the spectral ratio is one part in 10.

06:04

Even if we turn to the recently discovered,

06:06

and mysterious fast radio bursts,

06:08

you still only get down to one part in 20.

06:12

The truth is that short of an artificial transmitter,

06:15

we really don't know how such a narrow band signal

06:18

could ever be produced.

06:20

Of the four facts,

06:22

this is perhaps the most important.

06:24

Finally, turning to fact four,

06:27

this signal appeared to be continuous during the 72 seconds

06:30

that it was observed for.

06:32

Now, when you actually turn the numbers

06:34

and letters into a graph, you see a bell curve like this,

06:37

not a flat continuous line.

06:40

But here's the thing

06:41

because of the Earth's rotation,

06:43

the observatory is sweeping over the field during this time.

06:47

Meaning that, in fact,

06:48

the bell like curve is exactly what you'd expect

06:51

for a continuous source.

06:53

Fact number four is important

06:55

because most satellites reside in a low Earth orbit

06:58

where they would pass through the Wow field much faster

07:01

than the 72 seconds that the signal was observed for.

07:03

For example,

07:04

the International Space Station would pass

07:06

through the Wow field in less than a second.

07:09

So you'd only get one single high digit,

07:12

not the persistent sequence of six that was observed.

07:15

These four properties are essentially exactly

07:20

what you'd expect from an alien transmitter

07:23

and likely a very high powered one.

07:26

Now, it has to be said that a human made orbiting satellite

07:30

cannot be excluded,

07:31

but they would need to be on a wide orbit

07:33

beyond the geosynchronous orbital altitude

07:36

to yield a sufficiently slow speed,

07:39

which was rather unusual in 1977.

07:42

Yet more that signal

07:43

will be utilizing a protected frequency,

07:45

since the hydrogen line is internationally agreed

07:48

to be a protected channel.

07:50

Spy satellites also don't make a lot of sense here

07:52

because after all radio astronomers

07:55

across the world are very closely monitoring

07:57

that wavelength.

07:58

So it really wouldn't be very secretive to be using it.

08:01

Emission from a comet has also been previously suggested

08:04

and made the news a few years back,

08:06

but it has largely been rejected by the community,

08:08

since they do not emit strongly enough at this frequency,

08:12

nor were the cited comets,

08:14

even in the beam at the correct time.

08:16

So in summary,

08:17

we have these four observational facts

08:19

that together look quite promising

08:21

for the validity of the Wow signal.

08:23

But on either hand,

08:24

we also have four holes in our knowledge that frustrate us

08:28

and ultimately lead the door open

08:30

to skepticism about the Wow signal.

08:33

So let's go through these four.

08:34

Number one,

08:35

we don't know if the signal was modulated or not.

08:39

Two, we don't know where it even came from.

08:43

Three, the signal was strangely only detected

08:47

in one horn.

08:48

And four, we've never seen it repeat, ever.

08:52

Points one and two are really just a product

08:54

of the observatory's limitations.

08:57

The detect was not sensitive enough

08:59

to detect AM or FM modulation.

09:01

So there could very well have been a message embedded within

09:05

the Wow signal that we just never saw.

09:08

Obviously, if we had seen something like that,

09:10

it would've removed any doubt that this was truly

09:12

from an artificial transmitter.

09:14

Point two,

09:15

the unknown location surprises many.

09:18

Surely a telescope knows what star is looking at, right?

09:21

Well, Big Ear has two big issues here.

09:25

First, each horn spans a fairly wide field of view

09:29

about one by 20 arc minutes on the sky.

09:33

Second, we don't actually know

09:35

which horn detected this signal in the first place,

09:38

that was never recorded.

09:40

Albert Caballero recently investigated this issue

09:43

showing here the large region of space

09:46

where the source could have come from.

09:48

There's thousands of stars in here,

09:50

but Caballero tries to narrow this down

09:53

to 60 near sun-like stars as the best candidate.

09:57

But frankly, we have no idea

10:00

whether the source was indeed a sun-like star

10:03

or even from a star at all.

10:05

Point three is a weird one.

10:07

The two detect horns actually sweep over the same patch

10:11

of the sky,

10:12

but their physical separation means

10:14

that they see that patch three minutes apart in time.

10:17

Now, because we actually don't know

10:18

which of the two horns detected Wow,

10:21

that means there are two possible scenarios.

10:24

In scenario A,

10:25

the first horn detected the continuous radio mission

10:27

from the Wow field,

10:28

but the signal then switched off in the three minutes

10:32

between the horns.

10:33

Or in scenario B,

10:35

the signal was not present in the first horn,

10:38

but then it switched on in the three minutes

10:40

between the two horns.

10:41

Either way, though,

10:42

it seems rather fortuitous that the Big Ear just happened

10:46

to be looking at the right moment

10:48

to catch the switch over,

10:49

unless Wow is just constantly switching on and off.

10:52

And then to top it all off, we have point number four,

10:55

which is perhaps the most frustrating part

10:57

of this whole story,

10:59

because despite many efforts to reobserve the Wow field,

11:03

there have been no detections of a recurrence

11:06

of that signal.

11:08

With just one detection, the signal is tantalizing,

11:12

but not definitive.

11:14

So where does that leave us?

11:16

Well, definitive proof

11:18

that the signal was indeed astrophysical

11:20

and not some terrestrial interference or space debris

11:23

demands a repeat detection.

11:25

But on the other hand,

11:27

a lack of repetition also does not comprise definitive proof

11:31

that it was spurious either.

11:33

So we are left in no man's land.

11:37

Or are we?

11:39

As subscribers of our channel will know by now,

11:41

my approach to science

11:42

often takes a rigorous statistical approach

11:45

to such problems.

11:46

And so one might ask,

11:48

could the absence of any recurrence

11:50

of that Wow signal be used to exclude it

11:53

as an astrophysical source

11:54

and then just move on with our lives?

11:57

And so this is where our new research paper comes in,

12:00

where we take a deep statistical dive into the Wow signal

12:03

and aim to squeeze that data as hard as we can.

12:07

Many of you will know that we've discussed the Wow signal

12:10

before on this channel in our "Black Swans" video.

12:13

There, I discussed a different Cool Worlds research paper,

12:17

where I developed an (indistinct) model

12:19

for dealing with one-off events.

12:21

The model works very well when you have a single observatory

12:25

with constant settings,

12:26

but Wow has been pursued now

12:28

from many different observatory.

12:31

Yet more in that video,

12:32

we saw how the unknown duration of the Wow signal

12:36

causes a real headache

12:38

and different assumptions lead to very different answers

12:41

about its likelihood of recurring in the future.

12:44

And so after that last video, I wasn't satisfied.

12:48

I wanted to go back and do the Wow signal justice

12:51

to fix these issues and complete a final analysis.

12:55

I wanted to know,

12:56

I needed to know,

12:58

could the Wow signal still be a viable alien transmission,

13:02

even after all of those no results?

13:05

Whilst making that video,

13:06

I started corresponding with Robert Gray,

13:09

who literally wrote the book about the Wow signal.

13:12

perhaps more than anyone else Gray has pursued Wow

13:17

with a feverish curiosity, visiting the original site,

13:21

interviewing the team and studying the technical diagrams

13:23

of the observatory.

13:24

He even set up a 12 foot radio telescope in his backyard

13:30

to continuously monitor Wow from home.

13:32

Remarkably, even though he was not trained as an astronomer,

13:36

he was awarded telescope time

13:38

on the very large array in New Mexico to look for the Wow.

13:42

The first amateur astronomer to ever use the facility.

13:46

So after the video was posted,

13:48

we continued to correspond about the Wow signal

13:51

and started working on a new improved analysis.

13:55

So what is new here?

13:57

What is the big idea?

13:59

The basic premise of our approach is

14:01

to create a responsive emulator of the Big Ear Observatory

14:05

and indeed the other observatories

14:06

that observed the Wow field.

14:08

Back in 1985, Gray had visited Ohio State University

14:12

who operated the Big Ear,

14:14

and managed to reconstruct

14:16

the exact dates of each and every time Big Ear looked

14:20

at a Wow field.

14:22

Even though Wow was only seen once,

14:24

Big Ear actually observed that field on 122 unique days,

14:28

spanning August, 1977 to March, 1984.

14:33

However, only 90 of these were actually useful observations

14:37

due to various issues at the site.

14:39

We also know that Big Ear has this peculiar observing mode

14:43

where two horns pass over the same patch

14:46

of the sky each day,

14:47

separated by three minutes

14:49

and each one observing for just 72 seconds.

14:52

So equipped with this information,

14:55

can now simulate a hypothetical alien transmission

14:58

from the Wow field?

14:59

And ask in how many of those 180 observations

15:04

would we expect to detect it?

15:06

Now, this is where the fund begins,

15:07

because with that emulator,

15:09

we can change the properties

15:11

of our hypothetical alien transmissions

15:13

and see how would it affect the observations

15:15

that Big Ear would get.

15:17

So for example, if the signal repeated like clockwork,

15:20

once every hour

15:21

and stayed on for about 10 minutes,

15:22

then we would expect about 30 detections.

15:25

However, if the signal repeats say,

15:27

once every millennia, instead,

15:29

then we would get zero detections.

15:32

In this way,

15:33

we have a Big Ear sandbox, if you will,

15:36

where we can play God with different alien transmissions

15:39

and see what Big Ear would report each time.

15:42

Now, there's a certain degree of randomness here

15:45

because apart from the alien signal

15:47

is periodicity and duration,

15:49

it also has some arbitrary start time,

15:50

which we simply randomize in the simulations.

15:54

So for any given alien signal,

15:56

we actually generate thousands of different realizations

16:00

of it and then average them together at the end.

16:02

So the real point of all of this is

16:04

that we can now ask the question,

16:06

what kind of alien radio transmission do we have to generate

16:09

such that it matches the properties that Big Ear saw

16:12

for the Wow signal.

16:13

In other words, out of 180 attempts,

16:16

how do we get just one success?

16:19

Now, to make progress though,

16:20

we have to choose between one of two types of alien signal.

16:23

In case one, a repeat like clockwork

16:27

on a regular constant schedule.

16:29

So for example,

16:30

this could be an alien transmitter

16:32

that resides on a rotating exoplanet

16:35

or in case two, it repeats randomly.

16:39

Perhaps this might be an intentional leakage

16:41

from an advanced civilization that sporadically points

16:44

towards the Earth.

16:45

Perhaps even it could be an automated beacon

16:48

that deliberately follows a random schedule.

16:50

Since it turns out this would actually minimize the chance

16:54

of a signal being missed by a receiver on a planet

16:56

with a fixed rotation rate like the Earth.

16:59

Now, some of you might be thinking to yourself,

17:01

hold on, What about if the Wow signal was a one-off event,

17:04

not repeating at all,

17:05

but actually technically a one-off event

17:08

is still a repeating event

17:10

just where the repeat time equals infinity.

17:13

And so mathematically,

17:14

we don't have to change anything here.

17:15

It is fully encoded within our framework.

17:18

The first case of a periodic signal has been studied

17:21

extensively already, including by Gray himself.

17:25

The summary of this is that any periodicity below 14 hours

17:28

is completely excluded.

17:30

And even beyond that looks very unlikely.

17:34

So if we assume that alien transmitters have to be periodic,

17:38

well, there's really not much chance

17:40

of Wow being what we might have hoped it was.

17:42

In this vein,

17:43

The best way to save Wow is

17:45

to assume that it's not periodic,

17:47

but rather it follows some random schedule,

17:50

but even randomness can be characterized statistically.

17:53

If we assume the average number

17:55

of pings per unit time is unchanging,

17:58

then that means that the events

17:59

must follow the well known class on distribution.

18:02

What this essentially says is that

18:04

yes, the events are being generated by some unknown,

18:07

random generator,

18:08

but the properties of that random generator

18:10

are themselves not changing in time.

18:12

So now the Wow signal is characterized

18:14

by just two parameters.

18:16

The duration of the pulses, let's call that T,

18:19

and the average rate of pulses per unit time,

18:22

let's call that Lambda.

18:23

Equipped with our Big Ear emulator

18:25

and our random signal generator,

18:28

we are now finally ready to figure out

18:30

what are the properties of the Wow signal.

18:33

To do this,

18:34

we essentially create a dense 2D grid of possible duration,

18:38

T values on the X axis,

18:39

and Lambda values up on the Y axis,

18:42

and ask in each one of these simulations,

18:44

how often do we get a Wow like signal?

18:48

In other words, just one success from 180 observations.

18:52

You can see here,

18:53

the color coded map that we recover,

18:55

where the white region there leads to the highest odds.

18:59

In that region, the peak probability is in fact, 32.3%,

19:05

almost a 1/3.

19:06

So that means that the fact that we saw just one Wow signal

19:11

from the years of Big Ear observations

19:13

is actually not that weird.

19:15

It's a one in three outcome.

19:17

If the Wow signal has a T and Lambda in that region.

19:22

This is why statistics is so important

19:25

because let's compare that to our intuition

19:28

or, in fact, the intuition of Jerry Ehman,

19:30

who remember was the person who first discovered Wow,

19:33

back in 1977.

19:35

In a 1994 interview, Jerry said,

19:38

"We should have seen it again

19:39

when we looked for it 50 times."

19:42

But here,

19:43

we find that it's actually not particularly unusual

19:45

that Big Ear never saw it again,

19:47

even after 90 observing days.

19:50

So long as a Wow signal has the right T and Lambda.

19:53

But hold on, so far we've only used the original,

19:56

Big Ear observatory data,

19:58

but remember in the years that followed other observatories

20:01

have pursued the field and also come up empty-handed.

20:04

Surely, if we add in this extra data,

20:07

it will finally kill the Wow signal.

20:10

Well, using our emulator,

20:12

we can easily fold in this additional data

20:14

and see what we get.

20:16

Of the various follow up efforts of the Wow field.

20:18

Three, really dominate.

20:20

And we'll focus on those here.

20:22

In 1994, Robert Gray used

20:24

the 26 meter Harvard Smithsonian Radio Telescope

20:27

for a total of eight hours on target.

20:30

Then in 2002, gray was added again,

20:33

but now using

20:34

the University of Tasmania's 26 meter radio telescope

20:38

on target for 84 hours in total.

20:42

And finally, in 2020 Harvard now joined the hunt

20:45

and used the Allen Telescope Array

20:47

to collect more than 100 hours on the field.

20:50

So that means there's been more than 184 hours

20:54

of accumulated observations since the original Big Ear data.

20:57

And all of this new data has even higher sensitivity

21:00

than the original Big Ear observatory did.

21:03

So look, I get it.

21:04

It's easy to see why a director and observatory

21:08

would just shoot down any proposition

21:10

to keep going at this point.

21:12

But critically is that a rigorously justified position?

21:16

Using our emulator,

21:17

this triage of new observations

21:20

definitely reduces the overall probability

21:22

of a random Wow signal

21:24

matching all of the existing observations.

21:26

Whereas before our peak probability was 32.3%,

21:30

about a third, the best matching T and Lambda.

21:34

Now slide down to a probability of 1.8%.

21:38

So about one in 50. Now one in 50 is undeniably improbable,

21:43

but it's also hardly implausible.

21:47

It corresponds to 2.4 Sigma in statistical parlance.

21:50

But in science,

21:51

we would only normally consider a hypothesis rejected

21:54

if across the three Sigma threshold.

21:56

So that means that we would have to change this 1.8% number

21:59

to 0.3% to finally reject Wow.

22:02

In our paper,

22:03

we can use the ator to actually predict how much more data

22:07

is necessary to get to that point.

22:10

And the answer,

22:11

around 1500 hours of additional observing time

22:14

would be necessary

22:15

or 62 days of accumulated observations;

22:19

that might seem daunting,

22:21

but it could be achieved in a single year

22:24

with aggressive scheduling.

22:26

And the payoff would be a conclusive answer at last.

22:31

Either, we see, Wow, repeat and know it's the real deal

22:34

a frankly Earth shattering result,

22:38

or we see nothing

22:40

and can finally exclude it as an astrophysical source

22:42

to highest statistical probability.

22:45

Now, one thing I haven't revealed yet

22:46

are what are the most likely properties of the Wow signal.

22:50

I've told you those most likely properties have

22:51

a one in 50 chance of occurring,

22:54

but what are the associated duration T,

22:57

and mean repeat rate, Lambda,

22:59

that correspond to that most likely solution.

23:01

Coupling at emulator to an inference framework,

23:05

we can constrain that the duration of the signal

23:08

is between 2 minutes and 37 hours to 95% confidence.

23:14

And as for the mean repeat rate,

23:16

that comes in between about once every other month

23:19

to 12 times per month, again, to 95% confidence.

23:23

Very slow repeat times,

23:25

those less than once per year

23:27

are strongly disfavored by the existing data,

23:29

as they almost always lead to zero total detections,

23:34

rather than the one Wow signal that was observed.

23:37

So in conclusion, Wow, is still alive, just about.

23:42

It may be a real, repeating signal,

23:44

a scenario with a probability of 1 in 50,

23:48

or it may be bogus after all.

23:51

Something that we could conclusively state

23:53

if we collected just two months extra of new data.

23:56

Here, we've tried to push the statistics as far as we can,

24:00

but there's only so much we can model.

24:03

Perhaps our assumption

24:04

that the mean repeat rate doesn't evolve is wrong.

24:08

Maybe someone is behind the controls of that transmitter

24:10

who has substantially modified the mean repeat rate

24:13

over the last 45 years.

24:15

Who knows why, but it's not impossible.

24:18

In science though,

24:19

we try to proceed with this simplest model possible.

24:22

that's justified by the data,

24:24

a philosophy that hearkens back to William Ockham.

24:27

And in this case with a single data,

24:30

I don't think we can easily propose a more elaborate model

24:33

in the absence of additional data,

24:36

but even so our analysis shows that hope remains.

24:41

Wow could be still out there just waiting for me

24:46

or for you to go to the telescope

24:48

and hear it again.

24:51

To close, I wanna share one last thing with you.

24:55

Robert Gray was the co-author

24:56

with me on this new research paper,

24:59

but during the writing up of this work,

25:01

he tragically passed away in December last year.

25:05

I didn't know Robert personally,

25:06

but professionally, he was a true gentleman,

25:09

with whom my interactions were always warm and spilling over

25:13

with enthusiasm for the Wow signal.

25:16

And that's clear from his life, the data analyst by day,

25:19

who trained himself to become the world's preeminent expert

25:23

on the Wow signal.

25:25

I strongly recommend you pick up this book.

25:27

This is "The Elusive Wow" by Robert Gray.

25:30

It is the definitive book on the topic

25:33

and a great read.

25:35

Look, despite the tragedy of Robert's passing,

25:39

I personally have some solace

25:41

that this final project he wrote on the Wow signal

25:44

led to the result that there is still some hope

25:46

of Wow recurring, not a lot of hope, but a little,

25:51

and maybe a Nerf that someone out there,

25:54

perhaps watching this right now might pick this up

25:57

and one day resolve the Wow mystery.

26:02

I'm glad that I got to help Robert with that.

26:06

So, until next time, stay thoughtful and stay curious.

26:14

(gentle guitar music)

26:21

- Why care about life elsewhere?

26:24

That's a good question.

26:28

Life here is riot of different forms, colors, sizes, noises,

26:35

environments, behaviors.

26:38

And I think that people probably have an innate interest

26:43

in whether something like that happened elsewhere.

26:46

And the only way to settle that question, of course,

26:51

is to go look.

26:52

(ethereal electronic music)

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Wow信号外星生命射电天文学宇宙探索科学发现统计分析未解之谜Big Ear观测Robert Gray天文研究
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