A Christmas gift from The Science Geek 2017

 

Christmas is almost upon us. Once again I’m offering my e-books for free during the first five days of December!  Just call me Father Christmas :-).

Is Anyone Out There?” is about the likelihood of there being extraterrestrial intelligent life.  It is based on a number of posts from my blog.  For readers based in the UK the book is available to download from Amazon in Kindle format by clicking here and for readers in the US by clicking here. If you’re based outside the UK or US , see the notes at the end of the post.

Is Anyone Out There Cover

The Moon” is also based on a series of posts from my blog and you can guess what it is about.  UK readers download here, US readers here and anyone else please see the notes below.

Moon Cover

How to download the books if you’re based outside the UK or US.

There are threeways of doing this.

Option 1 if you go into the Amazon Kindle store and search for “The Science Geek” as the author you should find my books.

Option 2  I have created a page on my website where you will be able to download either of books for free.
https://thesciencegeek.org/e-books/

I’ll put them there until at least the end of the year.

Option 3  If your country is listed below, I have added some links  to allow you to download the books by just clicking on the link for your country.

Is There Anyone Out There?

Australia http://www.amazon.com.au/gp/product/B0131LVNW8?*Version*=1&*entries*=0

Brazil http://www.amazon.com.br/gp/product/B0131LVNW8?*Version*=1&*entries*=0

Canada http://www.amazon.ca/gp/product/B0131LVNW8?*Version*=1&*entries*=0

France http://www.amazon.fr/gp/product/B0131LVNW8?*Version*=1&*entries*=0

Germany http://www.amazon.de/gp/product/B0131LVNW8?*Version*=1&*entries*=0

India http://www.amazon.in/gp/product/B0131LVNW8?*Version*=1&*entries*=0

Italy http://www.amazon.it/gp/product/B0131LVNW8?*Version*=1&*entries*=0

Japan http://www.amazon.co.jp/gp/product/B0131LVNW8?*Version*=1&*entries*=0

Mexico http://www.amazon.com.mx/gp/product/B0131LVNW8?*Version*=1&*entries*=0

Netherlands http://www.amazon.nl/gp/product/B0131LVNW8?*Version*=1&*entries*=0

Spain http://www.amazon.es/gp/product/B0131LVNW8?*Version*=1&*entries*=0

USA http://www.amazon.com/gp/product/B0131LVNW8?*Version*=1&*entries*=0

The Moon

Australia http://www.amazon.com.au/gp/product/B00WRPR2S4?*Version*=1&*entries*=0

Brazil http://www.amazon.com.br/gp/product/B00WRPR2S4?*Version*=1&*entries*=0

Canada http://www.amazon.ca/gp/product/B00WRPR2S4?*Version*=1&*entries*=0

France http://www.amazon.fr/gp/product/B00WRPR2S4?*Version*=1&*entries*=0

Germany http://www.amazon.de/gp/product/B00WRPR2S4?*Version*=1&*entries*=0

India http://www.amazon.in/gp/product/B00WRPR2S4?*Version*=1&*entries*=0

Italy http://www.amazon.it/gp/product/B00WRPR2S4?*Version*=1&*entries*=0

Japan http://www.amazon.co.jp/gp/product/B00WRPR2S4?*Version*=1&*entries*=0

Mexico http://www.amazon.com.mx/gp/product/B00WRPR2S4?*Version*=1&*entries*=0

Netherlands http://www.amazon.nl/gp/product/B00WRPR2S4?*Version*=1&*entries*=0

Spain http://www.amazon.es/gp/product/B00WRPR2S4?*Version*=1&*entries*=0

USA http://www.amazon.com/gp/product/B00WRPR2S4?*Version*=1&*entries*=0

Voyager 40th anniversary

Nearly 40 years ago, on 20 August 1977, the Voyager 2 space probe was launched from Cape Canaveral, Florida, on a mission to study the Solar System’s four outermost planets. It was followed 15 days later by the launch of an identical spacecraft, Voyager 1.

The Voyager spacecraft -Image from NASA

Although Voyager 1 was launched after Voyager 2, it followed a different path which meant that it actually visited its first target, the planet Jupiter, four months earlier.

Image from Wikimedia Commons

The diagram above shows the trajectory of the Voyager spacecraft. The first targets, the giant planets Jupiter and Saturn, had previously been visited by NASA’s Pioneer 10 and 11 spacecraft, but the Voyagers had better instruments and were able to take more accurate observations. Among the discoveries made by Voyager was that Io, one of Jupiter’s moons, has a number of active volcanoes. This made Io the first place other than the Earth where volcanoes had been seen to erupt.

Jupiter’s moon Io – Image from NASA

Voyager 1 passed close to Saturn’s giant moon Titan. Titan is 5,150 km in diameter, nearly twice as large as the Moon, and is in fact slightly larger than the planet Mercury. It is the only moon in the Solar System with a thick atmosphere, which surrounds it with a dense haze hundreds of kilometres deep, making it impossible to see any surface details. At Titan’s surface the atmospheric density is roughly 5 times greater than the Earth’s at sea level.  Voyager 1 discovered that it consists mainly of nitrogen (98.4%) and methane (1.4%) with trace amounts of other gases such as ethane.

Saturn’s moon Titan – Image from NASA

These discoveries led to speculation that, like Earth, Titan has complex weather patterns. Being so far from the Sun, Titan’s surface is very cold, around minus 180 degrees.  This temperature is near the boiling point of hydrocarbons such as ethane and methane, which on Earth are found in natural gas. Voyager 1’s discoveries suggested that on Titan it rains liquid hydrocarbons in a similar way to how it rains water on Earth and that there were lakes of liquid hydrocarbons on Titan’s surface. A later mission by the spacecraft Cassini to Saturn and its moons did indeed detect many lakes of liquid methane on Titan (NASA 2016).

After passing Saturn, Voyager 2 visited the two outermost planets Uranus and Neptune (shown below).

Neptune – image from NASA

Uranus and Neptune are of similar size and are both much smaller than the gas giants Jupiter and Saturn. They are mainly composed of frozen water, ammonia and methane and are sometimes called the “ice giants”  So far Voyager 2 is the only mission to have visited the ice giants and most of what we know about Uranus and Neptune came from this spacecraft. No further missions to Uranus or Neptune are planned. Although it is possible that a mission to the ice giants could be launched by NASA in the the 2030s (Clark 2015), this is very much at the proposal stage. I think that this won’t happen, given the high cost of space missions and other higher priority targets such as exploring Mars.

After completing their primary mission to study the outer planets, the Voyagers left the Solar System. They are still in contact with Earth and are now sending back data about interstellar space. For more details on this part of the Voyagers’ mission click here.

The golden record

Each Voyager contained a golden record, the cover of which is shown below.

Voyager Record Cover

Image from NASA

The purpose of the golden record was twofold. If either of the Voyager spacecraft were ever found by an alien intelligence in the far future then, as I’ll explain later, from the golden record cover they would be able to work out the location of the Sun within the galaxy and, by playing the record, get some information about the sounds and sights of Earth in the 1970s.

If you look at the bottom left hand corner of the golden record cover there is a small circle with 15 lines coming out of it. This is shown in more detail in the diagram below.

This diagram was also put on a plaque on the earlier Pioneer probes and was devised by Frank Drake (1930-), who has been heavily involved in the search for extraterrestrial intelligence (SETI). The centre of the diagram, from which the lines radiate, represents the Sun.  The right-hand end of the longest line (at 3 o’clock) represents the centre of the galaxy.  The end of each of the remaining lines represents an object called a pulsar and the length of the line between the Sun and the pulsar represents the distance to the pulsar.

Pulsars are rapidly rotating objects which emit radio waves in regular pulses a few seconds or fractions of a second apart. Each pulsar has its own distinct interval or period between pulses and the marks drawn on the lines depict the length of the pulsar period not in seconds but in multiples of a fundamental time unit that an alien might understand (see note below).  The alien civilisation could then have sufficient information to identify the fourteen pulsars and the distance of the Sun from each pulsar, and thus work out the location of our Solar system.

On the upper part of the golden record cover is a picture of the record itself plus instructions for playing it.

Voyager Record

Image from NASA

The content of the record was agreed by a committee chaired by Carl Sagan (1934-1996) itself, and includes:

  • greetings in 55 different languages,
  • natural sounds and some music from Earth
  • 116 pictures of a variety of objects such as the planets in the solar system, human anatomy, groups of children, important landmarks, interesting places, and man-made structures such as airports, large telescopes, the Golden Gate Bridge in San Francisco, and an American highway in the rush-hour.
  • a printed message from the then United States president Jimmy Carter, part of which is given below:

“…This is a present from a small different world, a token of our sounds, our science, our images, our music, our thoughts, and our feelings.  We are attempting to survive in our time so that we we may live into yours. We hope someday, having solved the problems we face, to join a community of galactic civilisations. This record represents our hope and our determination and our goodwill in a vast and awesome universe.”

Where are the space probes now?

As well as the two Voyagers, three other spacecraft have been launched on a trajectory to take them out of the Solar System. They are New Horizons, which passed the dwarf planet Pluto in 2015 and Pioneer 10 and 11, which were the first spacecraft launched to leave the solar system. As you can see from the table, the Pioneer spacecraft  are no longer in contact with Earth.  There are two possible reasons for this: either their power supply has run out, or the radio transmitter is no longer lined up with the Earth and is beaming out signals in a completely different direction. The Voyager spacecraft are still in contact and should have enough power to continue transmitting messages back to the Earth until the mid 2020s.

 

In the table, the distance of the probes is given both in kilometers and astronomical units (AU). 1 AU is the average distance from the Earth to the Sun and is equal to just under 150,000,000 km. The outermost planet Neptune is about 30 AU from the Sun and the nearest star about 250,000 AU away. The speed column shows how fast the spacecraft is moving away from the Sun in AU per year.

Will the Voyagers ever be found?

Even astronomers who think that alien life is widespread within our galaxy think that it is very unlikely, given the vastness of space, that the Voyager spacecraft will ever be found.  The spacecraft are small and their power sources will have long died, thus making them unable to transmit a signal which could be picked up. However if they were ever to be intercepted by an alien civilisation it is fascinating to think what they would make of them.

Note about the pulsar diagram

Clearly units of time such as hours, minutes and seconds, which have been invented by humans, would be meaningless to an alien. Atomic hydrogen is the most common element in the Universe and Drake used the transition of a hydrogen atom, shown on the bottom right hand corner of the record cover, to create a “fundamental time unit” which he hoped an extraterrestrial race would understand.  When a hydrogen atom flips from one state to another it emits radio waves at a frequency of 1,420,406,000 waves per second, a fact that any advanced civilisation would be well aware of. So each individual wave corresponds to a time interval of 0.000 000 000 704 seconds. All the pulsar periods are expressed in multiples of this fundamental time interval.

References

Clark, S (2015) Uranus, Neptune in NASA’s sights for new robotic mission, Available at: https://spaceflightnow.com/2015/08/25/uranus-neptune-in-nasas-sights-for-new-robotic-mission/ (Accessed: 15 June 2017).

NASA (2016) Cassini explores a methane sea on Titan, Available at: https://www.nasa.gov/feature/jpl/cassini-explores-a-methane-sea-on-titan (Accessed: 15 June 2017).

 

A Christmas present from The Science Geek

 

Now that we are into December, Christmas is almost upon us. So, as I did last year, I’d like to give my readers an early Christmas present, by letting you download my short e-books for free during the first five days of December!

Is Anyone Out There?” is about the likelihood of there being extraterrestrial intelligent life.  It is based on a number of posts from my blog.  For readers based in the UK the book is available to download from Amazon in Kindle format by clicking here and for readers in the US by clicking here. If you’re based outside the UK or US , see the notes at the end of the post.

Is Anyone Out There Cover

The Moon” is also based on a series of posts from my blog and you can guess what it is about.  UK readers download here, US readers here and anyone else please see the notes below.

Moon Cover

How to download the books if you’re based outside the UK or US.

There are two ways of doing this.

Firstly, if you go into the Amazon Kindle store and search for “The Science Geek” as the author you should find my books.

Secondly, I have added some links below to allow you to download the book by just clicking on the link for your country.

Is There Anyone Out There?

Australia http://www.amazon.com.au/gp/product/B0131LVNW8?*Version*=1&*entries*=0

Brazil http://www.amazon.com.br/gp/product/B0131LVNW8?*Version*=1&*entries*=0

Canada http://www.amazon.ca/gp/product/B0131LVNW8?*Version*=1&*entries*=0

France http://www.amazon.fr/gp/product/B0131LVNW8?*Version*=1&*entries*=0

Germany http://www.amazon.de/gp/product/B0131LVNW8?*Version*=1&*entries*=0

India http://www.amazon.in/gp/product/B0131LVNW8?*Version*=1&*entries*=0

Italy http://www.amazon.it/gp/product/B0131LVNW8?*Version*=1&*entries*=0

Japan http://www.amazon.co.jp/gp/product/B0131LVNW8?*Version*=1&*entries*=0

Mexico http://www.amazon.com.mx/gp/product/B0131LVNW8?*Version*=1&*entries*=0

Netherlands http://www.amazon.nl/gp/product/B0131LVNW8?*Version*=1&*entries*=0

Spain http://www.amazon.es/gp/product/B0131LVNW8?*Version*=1&*entries*=0

USA http://www.amazon.com/gp/product/B0131LVNW8?*Version*=1&*entries*=0

The Moon

Australia http://www.amazon.com.au/gp/product/B00WRPR2S4?*Version*=1&*entries*=0

Brazil http://www.amazon.com.br/gp/product/B00WRPR2S4?*Version*=1&*entries*=0

Canada http://www.amazon.ca/gp/product/B00WRPR2S4?*Version*=1&*entries*=0

France http://www.amazon.fr/gp/product/B00WRPR2S4?*Version*=1&*entries*=0

Germany http://www.amazon.de/gp/product/B00WRPR2S4?*Version*=1&*entries*=0

India http://www.amazon.in/gp/product/B00WRPR2S4?*Version*=1&*entries*=0

Italy http://www.amazon.it/gp/product/B00WRPR2S4?*Version*=1&*entries*=0

Japan http://www.amazon.co.jp/gp/product/B00WRPR2S4?*Version*=1&*entries*=0

Mexico http://www.amazon.com.mx/gp/product/B00WRPR2S4?*Version*=1&*entries*=0

Netherlands http://www.amazon.nl/gp/product/B00WRPR2S4?*Version*=1&*entries*=0

Spain http://www.amazon.es/gp/product/B00WRPR2S4?*Version*=1&*entries*=0

USA http://www.amazon.com/gp/product/B00WRPR2S4?*Version*=1&*entries*=0

A Christmas gift from The Science Geek

 

Christmas is almost upon us. Give yourself an early Christmas present, without it costing you a penny, by downloading my e-books for free during the first five days of December!

Is Anyone Out There?” is about the likelihood of there being extraterrestrial intelligent life.  It is based on a number of posts from my blog.  For readers based in the UK the book is available to download from Amazon in Kindle format by clicking here and for readers in the US by clicking here. If you’re based outside the UK or US , see the notes at the end of the post.

Is Anyone Out There Cover

The Moon” is also based on a series of posts from my blog and you can guess what it is about.  UK readers download here, US readers here and anyone else please see the notes below.

Moon Cover

How to download the books if you’re based outside the UK or US.

There are two ways of doing this.

Firstly, if you go into the Amazon Kindle store and search for “The Science Geek” as the author you should find my books.

Secondly, I have added some links below to allow you to download the book by just clicking on the link for your country.

Is There Anyone Out There?

Australia http://www.amazon.com.au/gp/product/B0131LVNW8?*Version*=1&*entries*=0

Brazil http://www.amazon.com.br/gp/product/B0131LVNW8?*Version*=1&*entries*=0

Canada http://www.amazon.ca/gp/product/B0131LVNW8?*Version*=1&*entries*=0

France http://www.amazon.fr/gp/product/B0131LVNW8?*Version*=1&*entries*=0

Germany http://www.amazon.de/gp/product/B0131LVNW8?*Version*=1&*entries*=0

India http://www.amazon.in/gp/product/B0131LVNW8?*Version*=1&*entries*=0

Italy http://www.amazon.it/gp/product/B0131LVNW8?*Version*=1&*entries*=0

Japan http://www.amazon.co.jp/gp/product/B0131LVNW8?*Version*=1&*entries*=0

Mexico http://www.amazon.com.mx/gp/product/B0131LVNW8?*Version*=1&*entries*=0

Netherlands http://www.amazon.nl/gp/product/B0131LVNW8?*Version*=1&*entries*=0

Spain http://www.amazon.es/gp/product/B0131LVNW8?*Version*=1&*entries*=0

USA http://www.amazon.com/gp/product/B0131LVNW8?*Version*=1&*entries*=0

The Moon

Australia http://www.amazon.com.au/gp/product/B00WRPR2S4?*Version*=1&*entries*=0

Brazil http://www.amazon.com.br/gp/product/B00WRPR2S4?*Version*=1&*entries*=0

Canada http://www.amazon.ca/gp/product/B00WRPR2S4?*Version*=1&*entries*=0

France http://www.amazon.fr/gp/product/B00WRPR2S4?*Version*=1&*entries*=0

Germany http://www.amazon.de/gp/product/B00WRPR2S4?*Version*=1&*entries*=0

India http://www.amazon.in/gp/product/B00WRPR2S4?*Version*=1&*entries*=0

Italy http://www.amazon.it/gp/product/B00WRPR2S4?*Version*=1&*entries*=0

Japan http://www.amazon.co.jp/gp/product/B00WRPR2S4?*Version*=1&*entries*=0

Mexico http://www.amazon.com.mx/gp/product/B00WRPR2S4?*Version*=1&*entries*=0

Netherlands http://www.amazon.nl/gp/product/B00WRPR2S4?*Version*=1&*entries*=0

Spain http://www.amazon.es/gp/product/B00WRPR2S4?*Version*=1&*entries*=0

USA http://www.amazon.com/gp/product/B00WRPR2S4?*Version*=1&*entries*=0

Is There Anyone Out There? updated post

Thank you to everyone who has downloaded my books. One recent commenter pointed out that the links in the post point to the Amazon UK website and it was unclear how someone based outside the UK would download the books. I have therefore updated the post to make it easier for readers outside the UK to download them.

The Science Geek 🙂

I have written a short e-book on the likelihood of there being extraterrestrial intelligent life and how humans have tried to find that life and make contact with it.  It is based on a number of posts from my blog. For readers based in the UK the book is available to download from Amazon in Kindle format by clicking here. For readers outside the UK, see the notes at the end of the post.

Is Anyone Out There Cover

The book will be free to download until the end of Thursday 13 August GMT, after which time it will be £1.99.

I have also made my earlier e-book on the Moon available on the same deal. For readers based in the UK, this can be downloaded by clicking here.

Moon Cover

How to download the books if you’re based outside the UK.

There are two ways of doing this.

Firstly, if you go into the Amazon Kindle store and search for “The Science Geek” as the author you should find my books.

Secondly, I have added some links below to allow you to download the book by just clicking on the link for your country.

Is There Anyone Out There?

Australia http://www.amazon.com.au/gp/product/B0131LVNW8?*Version*=1&*entries*=0

Brazil http://www.amazon.com.br/gp/product/B0131LVNW8?*Version*=1&*entries*=0

Canada http://www.amazon.ca/gp/product/B0131LVNW8?*Version*=1&*entries*=0

France http://www.amazon.fr/gp/product/B0131LVNW8?*Version*=1&*entries*=0

Germany http://www.amazon.de/gp/product/B0131LVNW8?*Version*=1&*entries*=0

India http://www.amazon.in/gp/product/B0131LVNW8?*Version*=1&*entries*=0

Italy http://www.amazon.it/gp/product/B0131LVNW8?*Version*=1&*entries*=0

Japan http://www.amazon.co.jp/gp/product/B0131LVNW8?*Version*=1&*entries*=0

Mexico http://www.amazon.com.mx/gp/product/B0131LVNW8?*Version*=1&*entries*=0

Netherlands http://www.amazon.nl/gp/product/B0131LVNW8?*Version*=1&*entries*=0

Spain http://www.amazon.es/gp/product/B0131LVNW8?*Version*=1&*entries*=0

USA http://www.amazon.com/gp/product/B0131LVNW8?*Version*=1&*entries*=0

The Moon

Australia http://www.amazon.com.au/gp/product/B00WRPR2S4?*Version*=1&*entries*=0

Brazil http://www.amazon.com.br/gp/product/B00WRPR2S4?*Version*=1&*entries*=0

Canada http://www.amazon.ca/gp/product/B00WRPR2S4?*Version*=1&*entries*=0

France http://www.amazon.fr/gp/product/B00WRPR2S4?*Version*=1&*entries*=0

Germany http://www.amazon.de/gp/product/B00WRPR2S4?*Version*=1&*entries*=0

India http://www.amazon.in/gp/product/B00WRPR2S4?*Version*=1&*entries*=0

Italy http://www.amazon.it/gp/product/B00WRPR2S4?*Version*=1&*entries*=0

Japan http://www.amazon.co.jp/gp/product/B00WRPR2S4?*Version*=1&*entries*=0

Mexico http://www.amazon.com.mx/gp/product/B00WRPR2S4?*Version*=1&*entries*=0

Netherlands http://www.amazon.nl/gp/product/B00WRPR2S4?*Version*=1&*entries*=0

Spain http://www.amazon.es/gp/product/B00WRPR2S4?*Version*=1&*entries*=0

USA http://www.amazon.com/gp/product/B00WRPR2S4?*Version*=1&*entries*=0

Is There Anyone Out There ? e-book from the The Science Geek

I have written a short e-book on the likelihood of there being extraterrestrial intelligent life and how humans have tried to find that life and make contact with it.  It is based on a number of posts from my blog. The book is available to download from Amazon in Kindle format by clicking here.

Is Anyone Out There Cover

The book will be free to download until the end of Thursday 13 August GMT, after which time it will be £1.99.

I have also made my earlier e-book on the Moon available on the same deal. This can be downloaded by clicking here.

Moon Cover

New Horizons

On 14 July 2015 the New Horizons Spacecraft will fly past the dwarf planet Pluto which lies on the edge of our Solar System. This is the culmination of a nine and half year voyage which started when it was launched in back in January 2006.

New Horizons

Artist’s Impression of New Horizons passing Pluto – Image from NASA

After it has passed Pluto it will fly past one or two more dwarf planets which lie beyond the orbit of Neptune. It will then leave the solar system into interstellar space, the fifth spacecraft to do so since the launch of Sputnik 1 in 1957, the beginning of the space age. Like the other four spacecraft, New Horizons has a number of artefacts from Earth aboard, to allow for the extremely remote possibility it is found by an intelligent civilisation in the distant future. This post discusses these artefacts and the spacecraft they are carried on.

The Pioneer Missions

On 3 March 1972 Pioneer 10 was launched from Cape Canaveral on its mission to become the first spacecraft to fly past Jupiter, which it did in November 1973. After passing Jupiter it continued its journey to the edges of the solar system and beyond, becoming the first of only five spacecraft ever to pass beyond the orbit of the outermost planet Neptune.

pioneer10 Jupiter

Pioneer 10 passing the giant planet Jupiter in 1973- Image from NASA

When it leaves the Solar System, Pioneer 10 will drift through interstellar space getting further and further from the Sun. The spacecraft could last for millions, possibly even billions, of years and could in theory be recovered by an alien civilization.

In case that should happen, Pioneer 10 carries a simple plaque, shown below. This would tell intelligent beings from another planet where the spacecraft had come from and give them some basic information about humanity.

Pioneer_plaque

The Pioneer plaque- Image from NASA

The Pioneer plaque was designed by Carl Sagan (1934-96) and shows four relatively simple things, which he hoped an alien civilisation would understand.

  • On the top left is a diagram of a hydrogen atom. Hydrogen is the most common element in the Universe and emits radiation naturally at a wavelength of 21-cm, when it moves from one state to another. Sagan felt that any intelligent civilisation would know this and understand this diagram.
  • On the right is a figure of a man and woman. The man has his hand raised in a gesture of friendship, although there is no way of knowing whether an alien race would correctly interpret this.  The figures have caused some controversy – some have objected to the lack of clothing, whereas others, much more significantly, feel that the fact that both figures are clearly Caucasian does not fairly represent humankind.
  • Behind the figures is a diagram of the spacecraft. The man, woman and spacecraft are all drawn to the same scale. An alien race could therefore figure out how large we are.
  • At the bottom is a diagram of the Sun and nine planets. The arrow indicates which planet the spacecraft has come from. Pluto still features in the diagram, as its demotion to a dwarf planet only occurred in 2006!

The fifth item on the plaque is the diagram with 15 lines coming out of it and was devised by Frank Drake, who as mentioned in a previous post was one of pioneers of SETI. The centre of the diagram, from which the lines radiate, represents the sun.  The right-hand end of the longest line (at 3 o’clock) represents the centre of the galaxy.  The end of each of the remaining lines represents an object called a pulsar.  Pulsars are rapidly rotating objects which emit radio waves in regular pulses a few seconds or fractions of a second apart. You will notice that the lines to the pulsars are not smooth – you will see these more clearly if you use the zoom facility – and the marks drawn on the lines depict the length of the pulsar period in time units that an alien might understand.  The alien civilisation could then have sufficient information to identify the fourteen pulsars, and thus the location of our Sun and then the Earth.  If you are interested, there are additional notes at the bottom of this post explaining the technicalities of this.

An identical plaque was sent out in April 1973 on the spacecraft Pioneer 11.  This went past Saturn as well as Jupiter and, like Pioneer 10, is currently well beyond Neptune and on its way out of the Solar system and heading out into interstellar space.

The Voyager missions

The next spacecraft launched to leave the solar system were the two Voyagers.  Voyager 1 was launched on 5 September 1977 and, like Pioneer 11, flew past Jupiter and Saturn. Voyager 2 actually set off a couple of weeks earlier, on 20 August, on a mission to fly past all four outer planets – Jupiter, Saturn, Uranus and Neptune, Each Voyager contained a golden record, the cover of which is shown below.

Voyager Record Cover

Image from NASA

You will notice right away Drake’s pulsar map and the hydrogen atoms, but perhaps less obvious are a picture of the record itself plus instructions for playing it.  These instructions use symbols which Sagan hoped aliens would understand.

Voyager Record

Image from NASA

The record itself, entitled ‘The sounds of Earth’ includes:

  • greetings in 55 different languages,
  • natural sounds and some music from Earth
  • 116 pictures of a variety of objects such as the planets in the solar system, human anatomy, groups of children, important landmarks, interesting places, and man-made structures such as airports, large telescopes, the Golden Gate Bridge in San Francisco, and an American highway in the rush-hour.
  • a printed message from the then United States president Jimmy Carter, part of which is given below:

“…This is a present from a small different world, a token of our sounds, our science, our images, our music, our thoughts, and our feelings.  We are attempting to survive in our time so that we we may live into yours. We hope someday, having solved the problems we face, to join a community of galactic civilisations. This record represents our hope and our determination and our goodwill in a vast and awesome universe.”

Where are the space probes now?

The table below shows where the four spacecraft are now. However, the location given for the Pioneer spacecraft is only an estimate, as they are no longer in contact with Earth.  There are two possible reasons for this.  Either their power supply has run out, or the radio transmitter is no longer lined up with the Earth and is beaming out signals in a completely different direction.  We can therefore only guess where they are, based on their last known location, as they are too small and faint to see with any telescope. The Voyager spacecraft are still in contact and should have enough power to continue transmitting messages back to the Earth until the mid 2020s, but after that we will have to rely on projections for them too.

Voyager and Pioneer distances

In the table, the distance of the probes on 1 July 2015 is given both in kilometers and astronomical units (AU). 1 AU is the average distance from the Earth to the Sun and is equal to just under 150,000,000 km. The outermost planet Neptune is about 30 AU from the Sun and the nearest star about 250,000 AU away. The speed column shows how the spacecraft s moving away from the Sun in AU per year.

What objects are carried on New Horizons?

New Horizons doesn’t have any golden records, plaques or maps to tell an alien civilisation where it came from. Instead, it carries the following nine objects from Earth.

  • Some of the cremated ashes of the astronomer Clyde Tombaugh (1907-1998), who discovered Pluto
  • A CD with the names of 434,000 people who submitted their details to the project team – I would have loved to do this myself, had I only known about it in time!
  • A CD with the pictures of some of the staff who worked on the spacecraft
  • Two quarters (25 cent coins) from Florida and Maryland, where the spacecraft was built and launched
  • A small piece of SpaceShipOne, the first privately funded spacecraft to fly into space
  • Two US flags
  • A 1991 US postage stamp proclaiming, “Pluto: Not Yet Explored”.

The reason for there being nine objects is that Pluto was still considered to be the ninth planet from the Sun at the time the mission was being planned.  In August 2006  the International Astronomical Union (IAU) downgraded the status of Pluto to that of dwarf planet,  on the grounds of it being extremely small. Its mass is only a tenth of that of our Moon. It is ironic that the planet was demoted the very same year the mission was launched.

Pluto Earth Moon Comparison

Relative sizes of the Earth, the Moon and Pluto.  

Will any of the objects ever reach their intended recipients?  

Even astronomers who think that alien life is widespread within our galaxy think that it is very unlikely, given the vastness of space, that any of these five spacecraft will ever reach an alien civilization able to recover the objects sent for their perusal.  The spacecraft are small and their power sources will have long since died, thus making them unable to transmit a signal which could be picked up.

I personally believe that we are alone in the galaxy.  If I am right,  there is no alien race in existence to find the objects, let alone one intelligent enough to decipher them.

More likely, but still incredibly unlikely in my opinion, is the possibility that in the far distant future, long after the Voyagers, the Pioneers and New Horizons have been forgotten, mankind itself may leave Earth and colonise planets around other stars, and in millions of years time our descendants could discover one of these craft and its contents. It is fascinating to think about what they would make of them.

In popular culture

The Pioneer plaque and the Voyager golden record have made numerous appearances in popular culture including science fiction series such as Star Trek, Buck Rogers and the X-files.

In an episode of the”The Simpsons”.  The Pioneer plaque is shown with an alien holding the plaque upside down struggling to make sense of it!

 

Note about the pulsar diagram

Clearly Earth-based units of time such as seconds would be meaningless to an alien. Therefore Drake used the transition of a hydrogen atom, shown on the plaque, to create a time unit he hoped an extraterrestrial race would understand.

When a hydrogen atoms flips from one state to another it emits radio waves at a wavelength of 21.1 cm.  A wavelength of 21.1 cm corresponds to a frequency of 1,420,406,000 cycles per second. So each individual cycle corresponds to a time interval of 0.000 000 000 704 seconds. All the pulsar periods are expressed in multiples of this fundamental time interval.