De ontdekking van kleine groene mannetjes

‘The universe and more’. In 1967 was the first discovery of radio waves from little green men. My name is Roy Smits and in this series I talk about the universe and science. Today I’m going to talk about the discovery of these little green men. In the previous episode I told you how we might be able to detect radio signals from aliens with radio telescopes. These days astronomers are constantly looking at the radio waves from the universe.

00:50 - And the purpose of that is to try to understand what’s out there and how exactly it works. After all, since 1930 of the last century we have known that the universe does not only emit light that we could observe with the naked eye or with an optical telescope, but that the universe also emits radio waves. And the whole idea that we could find aliens this way, has long been seen as science fiction. But in 1967, we did receive a signal that looked like an actual signal from an alien intelligent civilization. This story is about Jocelyn Bell. In 1967 she worked as a student at Cambridge University under Professor Anthony Hewish.

01:42 - In the summer of 1967, she worked with other students to build this telescope. This telescope is very suitable for observing so-called quasars. These are galaxies that emit very strong radiation. And it was Jocelyn Bell’s job to analyze the data from this telescope. This is before the age of computers, so the data was written on a so- called chart recorder. This is a device through which paper passes and the signal is written out by an automatic pen that can move back and forth. So Jocelyn Bell had to search hundreds of metres of paper for special signals. And coincidentally she was very good at that. At one point, in those many hundreds of meters of paper that Jocelyn Bell had to study, she saw a signal that returned regularly. And that signal was quite similar to that from a local interference source, for example from an electrical appliance.

02:48 - But Jocelyn Bell is a curious person and she wanted to know exactly what that signal was, where it came from. So she started to study the signal more closely and discovered that the signal only returned when a certain spot in the sky was exactly above the telescope. In consultation with her boss Anthony Hewish, she decided to observe the signal more accurately. And that can be done by running the paper a little faster through the chart recorder when that mysterious place in the sky is exactly above the telescope. For this Jocelyn had to go to the observatory every day to manually adjust it.

03:33 - And what did she see? Nothing! Absolutely nothing. The signal had disappeared spontaneously. And for a month she went to the observatory every day and every day she saw nothing at all. The signal was gone. Until a special day when the signal spontaneously returned. And that happened to be the day Jocelyn Bell hadn’t gone to the observatory because she wanted to attend a lunch talk at her institute. Her boss wasn’t too happy. So the next day, Jocelyn Bell stayed at the observatory all day to make sure she wouldn’t miss the signal again.

04:18 - And sure enough, the signal was visible again and this time she had a great observation with a much higher accuracy. And this is what she saw. Pulses of radio waves from the deep universe. And these pulses are perfectly periodic, as if coming from some super sophisticated clock ticking every 1.33 seconds. What in the universe could cause such a thing? A clock? But clocks do not arise spontaneously in nature. So there is only one logical explanation: Jocelyn Bell had discovered little green men. The signal that Jocelyn Bell found was named LGM. That stands for Little Green Men. Jocelyn Bell, meanwhile, continued to analyze the hundreds of meters of paper and found another periodic signal. This time with a slightly different period and from a different place in the sky. And later she found two more Little Green Men like this. And all those signals seem to come from a clock, but they come from different places in the sky and that is weird.

06:16 - Because how is it possible that those aliens are on that side of the universe and also on that side of the universe? And that’s not all that is strange, because if the signals were really from aliens, then you would expect the signal to come from a planet. A planet orbiting a star. This is the earth revolving around the sun. And this is the planet of the little green men orbiting their own star. And these are the pulses that they send to the earth. If this signal really came from a planet, you would expect that the distance between those pulses would increase slowly or would decrease when the planet moves away from us or moves towards us.

07:08 - You can hear the same effect with the siren of an ambulance passing by. When the ambulance drives towards you, you will hear the pitch going up and when the ambulance leaves again you will hear the pitch going down. We call this the Doppler effect. And you would also expect that effect in this data set of the signal if you observe long enough. And indeed we see a Doppler effect in that signal, but that Doppler effect comes from the Earth moving around the sun. After all, that also gives a Doppler effect.

The source of this signal does not appear to have a Doppler effect. And that means that the source does not come from a planet. Then it seems that we have judged a little too quickly that the signal comes from little green men. But what is it then? Can nature spontaneously produce a perfect clock that also emits radio waves? I’ll talk about that next time. You will find more fantastic stories about astronomy in my book ‘Telescopes and Time Machines’. For more astronomy visit my website roysmits.nl Or Facebook: telescopes; Twitter: roy_smits or Instagram: jm_smits .