{"id":30632,"date":"2022-03-25T09:03:31","date_gmt":"2022-03-25T09:03:31","guid":{"rendered":"https:\/\/www.skyatnightmagazine.com\/?p=106410"},"modified":"2022-03-25T09:14:13","modified_gmt":"2022-03-25T09:14:13","slug":"a-formula-for-alien-life-understanding-the-drake-equation","status":"publish","type":"rss_feed","link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/rss_feed\/a-formula-for-alien-life-understanding-the-drake-equation\/","title":{"rendered":"A formula for alien life? Understanding the Drake Equation"},"content":{"rendered":"

<\/p>

By Maggie Aderin-Pocock\n \t\t<\/p>

Published: Friday, 25 March 2022 at 12:00 am<\/p>

\n\n

Some years ago, researchers <\/span>asked 2,000 people what scientific question they would most like answered.<\/span> Top of the list was: are we alone in the Universe?<\/p>\n

I was surprised (and quite heartened) by the fact that so many people thought this question was important, as it has always intrigued me too.<\/p>\n

But are we to getting any closer to an answer to that question: will we ever find life beyond Earth<\/a>?<\/p>\n

In 1961 American scientist Frank Drake tried to quantify the problem by looking at probabilities, laying down<\/span> the parameters that would<\/span> affect the numbers of active, communicative<\/span> civilisations in our Galaxy.<\/p>\n

\"""\"<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>
Dr. Frank Drake at his home in California, USA, 27 February 2015. Photo by Ramin Rahimian for The Washington Post via Getty Images<\/span><\/figcaption><\/div>\n

He came up with a calculation that has become known as the Drake Equation. The Drake Equation can be expressed thus:<\/p>\n

N<\/b> <\/b>=<\/b><\/span> <\/b>R*<\/b> <\/b>x<\/b><\/span> <\/b>fp<\/b> <\/b>x <\/b><\/span>fg<\/b> <\/b>x<\/b><\/span> <\/b>ne<\/b> <\/b>x<\/b><\/span> <\/b>f<\/b><\/span>l<\/b> <\/b>x<\/b><\/span> <\/b>f<\/b><\/span>i<\/b> <\/b>x<\/b><\/span> <\/b>fc<\/b> <\/b>x<\/b><\/span> <\/b>L<\/b><\/p>\n

What do the letters in the Drake Equation mean?<\/strong><\/h2>\n

R*<\/b> = the rate of yearly star formation in the Galaxy<\/p>\n

fp<\/b>= the fraction of stars with planets orbiting them<\/span><\/p>\n

fg<\/b>= the fraction of stars that could support habitable planets<\/p>\n

ne <\/b>= the number of planets that can potentially support life (per star with planets)<\/p>\n

fl <\/b>= the fraction of planets that actually develop life at some point<\/p>\n

fc<\/b>\u00a0= the fraction of civilisations that emit detectable signs of their presence<\/p>\n

L= <\/b>the average length that a civilisation exists<\/p>\n

Finding values for the Drake Equation<\/strong><\/h2>\n
\"""\"<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>
A DECam image showing the bulge of the Milky Way: part of a survey of 250 million stars. Credit: CTIO\/NOIRLab\/DOE\/NSF\/AURA.<\/span><\/figcaption><\/div>\n

OK, so we have Drake\u2019s famous equation, but how well can we actually apply values to the various parts of the formula?<\/p>\n

When Drake first considered the equation<\/span> some 53 years ago, only the first term, R*<\/b> \u2013 the rate of yearly star formation in the Galaxy \u2013 how many stars are born<\/a> \u2013 was known with any confidence.<\/p>\n

But with increasingly sophisticated equipment, we\u2019ve gleaned more and more information from our observations.<\/p>\n

Our estimate of fp<\/b>, the fraction of stars with planets orbiting them, has greatly improved<\/span> since the discovery of the first exoplanet<\/a> in 1992.<\/p>\n

\"""\"<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>
How many stars host planets orbiting in the so-called habitable zone?<\/span><\/figcaption><\/div>\n

Values for fg<\/b>, the fraction of stars that could support habitable planets, is also better understood today, although our definition of what makes a planet habitable<\/a> is limited to the one example we have \u2013 Earth \u2013 and so hinges on the availability of liquid water.<\/p>\n

The next parameter, ne<\/b>, the number of planets that can potentially support life (per star with planets), has driven our search for Earth-like planets rather than the larger, easier to detect Jupiter-like worlds that earlier searches revealed.<\/p>\n

At this point we reach a bit of a boundary, and we have to resort to guestimation rather<\/span> than estimation to fill out the rest of the parameters.<\/p>\n

We are on the cusp of being able to measure the initial signs of fl<\/b>, the fraction of planets that actually develop life at some point, using spectral analysis.<\/p>\n

Life as we know it leaves chemical signatures in a planet\u2019s atmosphere \u2013 biosignatures<\/a> \u2013 which could be detected by analysing light absorption through it.<\/p>\n

\"""\"<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>
Astronomers can search for atmospheric biosignatures in transiting exoplanets. Credit: NASA<\/span><\/figcaption><\/div>\n

It may even be possible to get a feel for fi<\/b>, the fraction of planets that will develop intelligent life, using a similar method.<\/p>\n

Some chemicals do not occur naturally, so if we detect them on an exoplanet it is likely that its population has made technological advances.<\/p>\n

The final two terms prove to be even harder: fc<\/b>, the fraction of civilisations that emit detectable signs of their presence, and L<\/b>, the average length that a civilisation exists, are very hard to judge when you have a sample of just one, us.<\/p>\n

As a result of the nebulous nature of these latter terms, estimates for the value of N<\/b> \u2013 the number of civilisations in our Galaxy which we may be able to communicate<\/span> with \u2013 can vary by more than 10 orders of magnitude.<\/span><\/p>\n

This could be seen as a problem,<\/span> but that might perhaps be missing the point of the Drake Equation, as it should not be seen as less of an estimating tool and more of a blueprint for how to go about searching for life in the Galaxy.<\/p>\n

This article originally appeared in the October 2014 issue of <\/strong><\/em>BBC Sky at Night Magazine<\/strong>.<\/strong><\/em><\/p><\/body><\/html>\n

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By Maggie Aderin-Pocock Published: Friday, 25 March 2022 at 12:00 am Some years ago, researchers asked 2,000 people what scientific question they would most like answered. Top of the list was: are we alone in the Universe? I was surprised (and quite heartened) by the fact that so many people thought this question was important, […]<\/p>\n","protected":false},"author":24,"featured_media":30633,"template":"","categories":[1],"acf":{"readingTimeMinutes":"4"},"uagb_featured_image_src":{"full":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/03\/a-formula-for-alien-life-understanding-the-drake-equation.jpg",1200,800,false],"thumbnail":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/03\/a-formula-for-alien-life-understanding-the-drake-equation-150x150.jpg",150,150,true],"medium":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/03\/a-formula-for-alien-life-understanding-the-drake-equation-300x200.jpg",300,200,true],"medium_large":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/03\/a-formula-for-alien-life-understanding-the-drake-equation-768x512.jpg",768,512,true],"large":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/03\/a-formula-for-alien-life-understanding-the-drake-equation-1024x683.jpg",800,534,true],"1536x1536":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/03\/a-formula-for-alien-life-understanding-the-drake-equation.jpg",1200,800,false],"2048x2048":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/03\/a-formula-for-alien-life-understanding-the-drake-equation.jpg",1200,800,false]},"uagb_author_info":{"display_name":"importmanagerhub@sprylab.com","author_link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/author\/importmanagerhubsprylab-com\/"},"uagb_comment_info":0,"uagb_excerpt":"By Maggie Aderin-Pocock Published: Friday, 25 March 2022 at 12:00 am Some years ago, researchers asked 2,000 people what scientific question they would most like answered. Top of the list was: are we alone in the Universe? I was surprised (and quite heartened) by the fact that so many people thought this question was important,…","_links":{"self":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/rss_feed\/30632"}],"collection":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/rss_feed"}],"about":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/types\/rss_feed"}],"author":[{"embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/users\/24"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/media\/30633"}],"wp:attachment":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/media?parent=30632"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/categories?post=30632"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}