Not made by humans? | Part 1

Dawn at Big Ear, Ohio State University,

At a quarter past ten in the evening on the 15th of August 1977
a once-in-a-lifetime event took place in Delaware:

a very strong signal arrived at the “Big Ear” radio telescope. It had all the characteristics of having come from an extraterrestrial intelligent source.

The OSU Big Ear radio observatory was aligned in North/South direction. The parabolic reflector is in the South.

No-one was at the telescope at the time. The receiver and telescope computer were doing their jobs all by themselves. Therefore the signal was actually first detected by a machine, a twelve year old computer.

The IBM 1130 had first been built in 1965. it looked and felt like an old battleship. It had only 1 megabyte of memory. For that reason the only record of the radio signal is a 6 digit printout on endless paper. There’s no audio recording of the signal. Today we would have a complete audio recording of it, measuring mega- if not gigabytes. But in those days, just six characters on paper had to suffice as a record.

After a few days the stack of computer printouts was bundled by Big Ear technician Gene Mikesell and brought to Jerry Ehman’s home.

Jerry Ehman was a SETI volunteer with the Ohio State University. Together with Bob Dixon he had written the software for the Big Ear computer in FORTRAN and assembler.

Around the 19th of August Jerry began analyzing the printouts from the radio telescope at his home, looking for unusual radio signatures.

A few pages into the pile of paper he saw a peculiar sequence of numbers and characters.

He was astonished. After highlighting in red pen the six characters “6EQUJ5” Jerry wrote the notation “Wow!” in the left margin of the computer printout opposite them.

The Wow! signal printout

The characters and numbers denoted a very strong narrow-band transmission. Apparently it had come from outer space. Narrow-band transmissions usually don’t occur naturally and are a sign of artificial origin.

Conventionally speaking, all artificial things are made by humans. That’s because human language and the Cambridge Dictionary defines “artificial” as “made by humans”. That definition may have to be revised.

The Wow! transmission had all the hallmarks of a radio signal from a non-human extraterrestrial civilization. In the 1959 article “Searching for Interstellar Communications” Giuseppe Cocconi and Philip Morrison explained that using the 21 cm hydrogen frequency was a logical choice for SETI.

And that was precisely the frequency of the Wow! signal. It had come from the direction in the sky were the constellation Sagittarius is found. 

The Big Ear radio and computer shack.

If we transfer the number codes from the Wow! printout to plotting paper we can see the waxing and waning strength of the 1420 mHz radio beam that reached the radio telescope. Each of the letters and numbers corresponds to a certain signal intensity, as the next graph illustrates.

The signal may have been transmitting for centuries and was never detected because no one looked for it before. The signal source did not move in the sky. The only thing that moved over for 72 seconds was the Earth, rotating majestically from East to West as the radio receiver moved in and out of the signal beam.

And then the signal vanished. Gone. The signal would have been picked up again by the second horn antenna of Big Ear. But it was no longer there.

The rise and fall of the signal we see in the graph above was due to the antenna pattern, the signal itself remained at constant strength.

The graph below shows a similar signal pattern in “OV-221”, the radio source to the right of the Wow! signal. (OV-221 is also known as MSH 19203 (Mills Slee Hill Radio Sources)).

In this broadband continuum record the Wow! signal does not show up because it is too narrow-band.

Today I’m waiting to hear if OV-221 corresponds to the center of the Milky Way galaxy , Sagittarius A*, but no-one seems to know the old radio source designations anymore.

After Jerry Ehman showed the computer printout of the Wow! signal to John Kraus and Bob Dixon, they immediately talked about it, speculating and making hypotheses. Quickly, John and Bob began to investigate the various possibilities.

Dr. John Kraus was a physicist and the designer of the Big Ear radio telescope. He actually invented several types of radio antennas.

Bob Dixon was the director of SETI at Ohio State University radio telescope.

Together they excluded the possibility of the signal having been a plane, planet, asteroid, comet, satellite, space craft, ground based transmitter, or any other known natural source.

Now, since the Wow! signal appeared to be unnatural and no known human cause for it could be found, it was suspected that it could have come from a technological alien civilisation.

It was decided to go back to the region in space were the signal had come to see if it could be found again. The scientific method calls for reproducibility of any experiment or result.

Weeks turned to months, and years into decades as astronomers from all over the world searched the region in space were the Wow! signal had been detected.

The Wow! signal was never found again.

Calculations on the space region of the Wow! signal

Image by The Planetary Society, license

The Wow! signal was observed for 72 seconds. In this time a region of space equivalent to 18 arcminutes was scanned, according to the following calculations:

24h x 60 min = 1440 mins/day = 86400 sec
360° / 86400 = 0.0041° per second
72 seconds = 0.3°

An arcminute (denoted by the symbol ‘), is an angular measurement equal to 1/60 of a degree or 60 arcseconds. To convert a degree measurement to a minute of arc measurement, we multiply the angle by the conversion ratio.

The angle in minutes of arc is equal to the degrees multiplied by 60:
0.3 x 60 = 18 arcminutes.

As seen from the Earth, the Sun and Moon both have angular diameters of about 30 arcminutes. The full moon’s average apparent size is about 31 arcminutes (or 0.52°).

In other words, the Wow! signal spanned an area of about half the size of the Sun or the Moon, as seen from Earth in the sky. That is a rather large area in astronomy.

On the basis of this simple calculation I cannot readily agree that the Wow! signal came from a pointlike source. That may or may not be a problem. It can be resolved by agreeing that the resolution of the Big Ear radio telescope was not any better!

The frequency and speed of the Wow! signal source

It’s assumed that aliens that use the hydrogen frequency do so in a manner to compensate for the motion of their planet with respect to the motion of Earth. Otherwise the precise frequency of the hydrogen becomes higher or lower.

That’s why it’s important to look at the precise frequency of the signal.

John Kraus, the director of the observatory, gave a frequency value of 1420.3556 MHz in his 1994 summary written for Carl Sagan.

Jerry Ehman in 1998 gave a value of 1420.4556±0.005 MHz. 

This is (50±5 kHz) above the hydrogen line value of 1420.4058 MHz.

Only one of those frequencies could be the correct one. The explanation of the difference between Ehman’s and Kraus’s values was that a new oscillator had been ordered for the frequency of 1450.4056 MHz.

The university’s purchasing department then made a typographical error in the order and wrote 1450.5056 MHz instead of 1450.4056 MHz. The software used in the experiment was then written to adjust for this error. When Ehman computed the frequency of the Wow! signal, he took this error into account.

After all errors are accounted for, the Doppler shift of 1420.4556 MHz indicates that the Wow! signal source moved at a speed of 37 893 km/h towards Earth. The following calculations show how I arrived at that speed:

Calculations on the Doppler shift of the Wow! signal

The Wow! signal was detected at 1420.4556 MHz. First we need to convert the frequency to the wavelength. The wavelength is given by the frequency and the speed of light, how far one wave crest travels in a given time span.

Frequency to wavelength calculator:

The frequency of the Wow! signal 1420.4556 MHz is equal to a wavelength of (Δλ) 21.105373 cm. That’s the distance between each wave crest.

The presumed origin signal of hydrogen has a precise frequency of 1420405751.768 Hz, equivalent to the wavelength of (λ) 21.106114054160 cm. Wikipedia:

The doppler shift speed from delta lambda and lambda = 299 781 932.02409 m/sec.

Now we subtract
299 781 932.02409 m/sec
[Doppler shifted Wow! signal speed from v = (Δλ/λ) * c]
-299 792 458 m/sec [ speed of light (c)]

10 526 m/sec = 37 893 km/h or 10.526 km/sec.

Ref. 1: The source of the Wow! signal approached Earth at a speed of 37 893 km/h or 23 545 mph, if the transmission frequency was from hydrogen.

The average speed of asteroids is 18 – 20 km/s vs the 10.52 km/s from the Wow! signal. Comets that impact Earth usually are also faster, at 30 km/s.

End of part 1.

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Can We Have Artificial Gravity In Spacecraft?

Why has nobody built rotating spacecraft to simulate gravity?

Pictured: a fairground ride from the 1950’s, I call it a GRAVITY DRUM.

A whole spacecraft is expensive to rotate, but small spaces on space stations or ships could easily be rotated.

Can those small spaces be big enough to provide meaningful and healthy artificial gravity?

From my physics knowledge I recall that gravity and acceleration are the same.

If I remember correctly, 1 g is equal to an acceleration of 9.81m/sec per second. In other words, a wheel with a circumference of 10 meters would have to be spun about once per second to simulate 1 g in Zero gravity? Not quite.

Alas, it’s a bit more complicated than that, and thankfully we don’t have to spin the wheel quite so fast. That’s a bonus!

Here are a few handy calculators to work out wheel sizes and rotation rates to simulate Earth gravity:

SpinCalc, solves for gravity, radius and rotation rate,

Circle Calculator, solves for diameter, radius and circumference.

A wheel with a circumference of 10 meters would have a diameter of 3.18 meters. This would be a handy size for artificial gravity experiments, even on Earth.

Would it be comfortable to spend any time in this? The wheel should rotate at about 24 RPM to simulate 1 g. It could be compartmentalized in to 1 x 2 meter beds, holding ten crew.

So at least during their rest period spacefarers would have the benefit of normal gravity. The astronauts are lying on the inside of the wheel, a bit like in the fairground ride illustration but with more privacy.

Is it feasible to built such small Drum Gravity units?
How would the human body react? (Artificial Gravity by Centrifuge).

We know that the negative effects of zero gravity are really serious and numerous. Even 2.5 hours of daily treadmill exercise are insufficient to prevent these effects:

  1. fluid redistribution: Bodily fluids shift from the lower extremities toward the head. This precipitates many of the problems described below .
  2. fluid loss: The brain interprets the increase of fluid in the cephalic area as an increase in total fluid volume. In response, it activates excretory mechanisms.
  3. electrolyte imbalances: Changes in fluid distribution lead to imbalances in potassium and sodium and disturb the autonomic regulatory system .
  4. cardiovascular changes: An increase of fluid in the thoracic area leads initially to increases in left ventricular volume and cardiac output. As the body seeks a new equilibrium, fluid is excreted, the left ventricle shrinks and cardiac output decreases.
  5. red blood cell loss: Blood samples taken before and after American and Soviet flights have indicated a loss of as much as 0.5 liters of red blood cells.
  6. muscle damage: Muscles atrophy from lack of use. Contractile proteins are lost and tissue shrinks. Muscle loss may be accompanied by a change in muscle type.
  7. bone damage: Because the mechanical demands on bones are greatly reduced in micro gravity, bones essentially dissolve.
  8. hypercalcemia: Fluid loss and bone demineralization conspire to increase the concentration of calcium in the blood.
  9. immune system changes: Loss of T-cell function may hamper the body’s resistance to cancer — a danger exacerbated by the high-radiation environment of space .
  10. interference with medical procedures: Bacterial cell membranes become thicker and less permeable, reducing the effectiveness of antibiotics.
  11. vertigo and spatial disorientation: Without a stable gravitational reference, crew members experience arbitrary and unexpected changes in their sense of verticality.
  12. space adaptation syndrome: About half of all astronauts and cosmonauts are afflicted. Symptoms include nausea, vomiting, anorexia, headache, malaise, drowsiness, lethargy, pallor and sweating.
  13. loss of exercise capacity: This may be due to decreased motivation as well as physiological changes.
  14. degraded sense of smell and taste: The increase of fluids in the head causes stuffiness similar to a head cold.
  15. weight loss: Fluid loss, lack of exercise and diminished appetite result in weight loss. Space travelers tend not to eat enough.
  16. flatulence: Digestive gas cannot “rise” toward the mouth and is more likely to pass through the other end of the digestive tract “very effectively with great volume and frequency” .
  17. facial distortion: The face becomes puffy and expressions become difficult to read, especially when viewed sideways or upside down.
  18. changes in posture and stature: The neutral body posture approaches the fetal position. The spine tends to lengthen.
  19. changes in coordination: Earth-normal coordination unconsciously compensates for self-weight. In weightlessness there is a tendency to reach too “high” .

Compared to these adverse effects of zero gravity, here are some studies by a psychologist named Graybiel from 1977 on the effects of rotating a human on his own axis here on Earth, like on a spit (from


Graybiel concluded that 
1.0 RPM: even highly susceptible subjects were symptom-free, or nearly so
3.0 RPM: subjects experienced symptoms 
5.4 RPM, only subjects with low susceptibility performed well
10 RPM, adaptation presented a challenging but interesting problem. Even pilots without a history of air sickness did not fully adapt in a period of twelve days.

The “adaption” that Graybiel is talking about is the getting used to the absence of the rotation, after the body had been spun.

What that feels like we all remember from childhood.:


I must say that spit rotating a human on his own axis in the horizontal under the influence of Earth gravity is most likely to be very far removed from what a human may experience in an artificial gravity drum in weightless space.

I’d go as far as to say that Graybiel’s rotation comfort zones have absolutely nothing to do whatsoever with artificial gravity by centripetal force. All he proved in his paper “Somatosensory motion after-effect following earth-horizontal rotation about the Z-axis” is that the after effect of spinning someone rapidly is disorientation of the vestibular system of the ear, leading to dizziness, aka vertigo.

But let’s see if these Graybiel’s comfort zone figures can be applied.
The SpaceX Mars rocket is going to have a diameter of 9 meters. Would it be possible to create a comfortable habitat for sleeping or resting spacefarers within the confines of this rocket?

A 9 meter drum would need to rotate at 14 RPM to simulate 1 g, or at 8 RPM to achieve 1/3 of Earth gravity. Graybiel’s findings would indicate that the space available on the SpaceX Mars rocket would be too small.

However, I believe that the gravity (centripetal force) acting on the body as it lies down, not spinning about itself and on one level , will be more comfortable than twirling rapidly around one’s own axis.

In Drum Gravity Bed Units there would be no head-to-foot acceleration gradient.

The drum gravity bed units are conceived of as an add-on module to a spacecraft or space station, be it in transit, orbit or on the Moon, Mars or asteroids to provide more natural gravity.

Have prototypes of this concept been built?

In a certain way: Yes! The first picture in this post is a fairground attraction from the 1950’s.

Did humanity really forget from the ’50s how easy and fun it is to enjoy artificial gravity? Apparently the fairground visitors subjected themselves to the experience voluntarily and enjoyed it.

“Rotor Ride”

Simple gravity devices like this could help spacefarers to maintain their health, after the device is tweaked.


Rotating wheel space station — Wikipedia

Here are the calculations on the von Braun wheel from 1952 used in the movie 2001: A Space Odyssey:

They envisioned a rotating wheel with a diameter of 76 meters (250 feet). The 3-deck wheel would revolve at 3 RPM to provide artificial one-third gravity. It was envisaged as having a crew of 80.

Fast forward 70 years (not much has happened since the 1950’s):

The SAHC human centrifuge began testing and operations in about 2020. It’s to investigate the tolerability and use of artificial gravity on astronauts and their health, to counter the effects of weightlessness. What’s taken so long?

The machine measures 5.6 meters in diameter. 
It would be small enough to put in the SpaceX Mars rocket. But it needs a few more seats.

Centrifuge with lying test person

With the Short-Arm Human Centrifuge (SAHC) in Cologne — provided by the ESA — artificial gravity will be created to afford fundamental research in medicine and human physiology. The main focus is on the possibility to extend e.g. bed-rest studies to test methods of artificial gravity based counter-measures for medical risks due to weightlessness.

Technical data:

Max. radius at outer perimeter: 2,8 m
Max. overall payload: 550 kg

Max. centrifugal acceleration
(foot level, test subject height 185 cm): 4.5 g
Max. revolution of centrifuge rotor
(software limit): 39 rpm

Scientific applications

  • Development of effective countermeasures for neuromuscular and skeletal degeneration of astronauts using Artificial Gravity, etc…

This is an article by Erich Habich-Traut for the Contact Project,

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