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ET Would Know There’s Life on Earth

Article written: 20 Dec , 2007
Updated: 26 Dec , 2015
by

It seems impossible to believe, but astronomers are now making plans to reach for the brass ring of planet hunting: to find Earth-sized worlds orbiting other stars, and then to analyze them to see if there’s life. But you’ve got to know what you’re looking for. That’s why astronomers are considering what the Earth might look like from afar. What clues would our planet give to distant astronomers that there’s life here?

The number of discovered planets is up to 240 now and growing. In fact, the planetary discoveries are coming so fast and furious that many universities don’t even bother releasing press releases any more.

But these are all hostile worlds; larger than our own gas giants, and many orbit tightly to their parent star. We’re not going to find life on these “hot jupiters”. No, it’s going to be the Earth-sized planets, orbiting within the habitable zone of their star, where water can still be a liquid on the surface of the planet. These planets are going to have active weather systems, oceans and land masses.

Even with a telescope with many times the power of the Hubble Space Telescope, an Earth-sized world would appear as a single pixel in a vast empty space. You wouldn’t get any kind of detailed resolution.

Can a single pixel tell you anything about that world? Researchers say, “yes”. In a new paper published in the online edition of the Astrophysical Journal, they say that observers looking at the Earth from afar would be able to judge our rotation rate, the probability of oceans, weather, and even if the planet has life.

If distant astronomers were watching Earth, they’d see the brightness change over time as clouds rotated in and out of view. If they could also measure its rotation period, they’d know whether a certain part of the planet was in view, and start to deduce if there are oceans or land masses pointed towards them.

The researchers have created a computer model for the brightness of Earth over time, showing that the global cloud cover is surprisingly constant. There are usually clouds over the rain forests, and arid regions are clear.

Astronomers watching Earth would start to recognize the patterns, and be able to deduce an active weather system here. Compare this to the other planets in the Solar System:

“Venus is always covered in clouds. The brightness never changes,” said Eric Ford, a UF assistant professor of astronomy, and one of 5 authors on the paper. “Mars has virtually no clouds. Earth, on the other hand, has a lot of variation.”

To recognize these kinds of characteristics on another world will require a telescope with roughly twice the size of Hubble. And observatories like this are in the works.

Original Source: University of Florida News Release


24 Responses

  1. Andy C says

    As a note, JPL PlanetQuest has the number of exoplanets up to 269, around 231 stars.

  2. MrBill says

    “To recognize these kinds of characteristics on another world will require a telescope with roughly *twice* the size of Hubble”

    OH LORD?! Twice the size of Hubble? How much could it possibly cost to build one 5x or 10x or 20x?

  3. david pinnell says

    So why haven’t they called?

  4. Bill says

    Because the long distance rates would be astronomical…….

  5. If we are being watched now by beings more technically advanced than we are, we have to assume that they and others could have been doing so for hundreds of millions of years or longer.

    They will have been able to detect a sudden change in our atmospheric composition that coincides with abnormal interference with the planet’s evolution. Since the composition of the atmosphere results to a very large extent from an organic contribution over millions of years, a sudden rise in carbon gases will indicate the presence of this abnormality.

    Intelligences, far more advanced than ours will probably be monitoring thousands of other planets as well, and will have recorded their evolutionary changes over thousands of years.

    The mind boggles because technically we are the infants on the block, and we have so much to discover, that is if we can restrain ourselves sufficiently to not turn our planet into a desert millions, or perhaps billions of years before its time.

  6. Adam says

    A side question: so can we confirm there is no planet around Proxima Centauri already? Or, just no one is sure. Quite depressed to think about the nearest star is about 4.22 light year away.

  7. Torben Marer says

    I couldn’t help thinking that some advanced people sitting on a planet around 70 billion light years away looking at our planet at the time of the dinos.

    Maybe that’s why they didn’t contacted us.

  8. Christian says

    I disagree, there are hundreds of planets near the solar system, dicovered and undiscovered, and if someone are looking right here, he would see the 20th century…

  9. Andy C says

    > A side question: so can we confirm there is no
    > planet around Proxima Centauri already?

    Adam, I would suggest that we simply don’t know yet (although I can’t be absolutely certain it hasn’t been ruled out.). I believe Gliese 581 c is the smallest planet we have ever found, and that’s 5 Earth masses, and Epsilon Eridani b is closest at 10.4 light years (0.86 Jupiters).

    > OH LORD?! Twice the size of Hubble? How
    > much could it possibly cost to build one 5x or 10x
    > or 20x?

    MrBill, the James Webb Space Telescope is a 6.5m infrared telescope (compared to Hubble’s 2.5m), scheduled for launch in 2013, at a cost of about $4 billion. The problem with anything much larger is how we actually launch it into orbit, as I believe 8m is about the maximum for current launch vehicles (I think post JWST launch vehicles push this out to about 16m, but 25m and 50m space telescopes look a very long way off).

  10. Jimmy J says

    I agree with Torben.

    Like with any type of signal containing information, you have to be looking in the right part of the sky at the right time (see: variable “L” in the Drake Equation).

    Intelligent life on any planet could have already died out by the time its light reached our telescope.

    And forget about sending them a message. We’ll likely be extinct before it reaches them.

    Without the ability to bend space/time, the Universe will remain a lonely place.

  11. Torben Marer says

    You may rigth in some way, but on the other hand, if we get into contact, we’re all dead before getting an answer back.

    And if there are some hidden out there, they may think they have seen UFO’s, when they get a glimse of all the merchandise we are sending out on missions in the universe.

  12. michel duchaine says

    We have just to wait for a visit.If any extraterrestrial civilisations exist,it is sure and certain these have received a lot of messages…particularly our laser beam communication emitted from our military communications systems (Soviet,US and chinese) since the sixties.We have commit the biggest mistake of all times…revealed our existence.If any ET exists somewhere our messages hit 1000 worelds a day.!!!

  13. Karan Patki says

    Here , we assume that the basic requirements for life on exoplanets might be the same as that for life on Earth . Is it not possible that a totally different civilization living in a totally different environment might be watching us as a non-habitable planet?

  14. Jesse says

    Send out the Big GREEN Laser Beacon to SPACE!!!! WE NEED HELP…..this project is not going well !!!!!!

  15. Senad Subasic says

    >It’s probably possible to tell if a planet has water due >to its distinct shade of blue

    But water is blue just because the sky is blue, and the sky is blue due to Rayleigh scattering. So, it’s not exactly universal 🙂

  16. I might not pack my bags for a million-year voyage to Earth 2 based solely on the flickering color of a single pixel, even if it includes the right shade of blue, the size is right, and the neighborhood looks OK.

  17. Kent Durvin says

    Senad Subasic: Water is not blue because the sky is blue. Water is very slightly blue. Take a look at water under cloudy skies; still blue. Here is a good reference:
    http://www.dartmouth.edu/~etrnsfer/water.htm

    If we would be extinct by the time ET replied, we still might get a signal from ET, who might be extinct by now. It goes both ways. There is value in knowing, even if a conversation is not possible. Trade is not likely. Nothing is worth the trouble of crossing the vastness of space.

  18. david pinnell says

    The problem we all have is that all this speculation is based on the level of our technology today. Just to give a crude example we are now entering the digital age of communication. If we had been searching for Alien ‘Radio’ transmissions’ using Analogue receivers when they were transmitting digital ones we simply would not have been capable of understanding their signal even if we did pick it up.

    A hundred, a thousand years from now who’s to say what communications technology may have evolved or be possible. The most advanced device of today will most likely be as obsolete as sending a pigeon or writing on a piece of stone with a chisel.

    The simple fact is that if there are other intelligent tool using species in the Galaxy they are probably millions of years ahead of us, so much so that our crude attempts to contact them or find them are probably on no more interest to them than if an ant were to start waving a feeler in our direction!

    If they are are there, which they probably are, then lack of contact leaves just two options. The first of these is that the Einsteinian view of the Universe and Relativity is spot on and therefore contact is either impossible or pointless over such vast distances. i.e. as many people have pointed out by the time a signal is received the species sending the message has become extinct

    The second option is that, if emerging string theory is correct and the bending of time and space might be possible, therefore they haven’t contacted us either because they don’t exist or because we are too primitive to bother with. In the case of the later, this may well be because we haven’t yet developed the technology they are using.

  19. George G. Kountouris says

    I liked very much the concluded phrase of Mr Jimmy’s comment, the “absence of ability to bend space/time, the Universe will remain a lonely place.”
    I made allready a work/ article “The propabity to make a journey to stars’ with excactly the same closing conclusion.
    (i have this in Greek language.is hard to translate this in enlish)

  20. Vince says

    I have to agree with David.

    I have absolutely no doubt that there are many other forms of life in our galaxy and others. I think because of our rigid and limited understanding of space and especially time, that many of these other life forms are incredibly more advanced than us. They could have evolved millions of years ago and have such advanced technology that we would not be able to interpret a signal. However, they may just not have interest.

    Also, you would think if someone wanted to contact us and were advanced enough that they could reach us if they wanted to. Whether bending space time or using a technology to traverse the vast distance between two worlds, there is most likely someone or something out there able to do it, if we were worthy.

    It would be a great shame if we were the only intelligent life formes in the universe…would be such a great waste of space.

  21. david pinnell says

    If they are there another point is that would we really want them to contact us anyway? If one examines the history of our planet it quickly becomes apparent that contact between a technologically advanced culture and a more primitive one rarely, if ever, does any favours for the less advanced.

    Look at what happened when Europeans discovered the Americas, the Inca and Aztec civilisations were swept away in just a few decades whilst the culture and history of the plains Indians suffered a similar fate. Examination of almost any period of human history will normally always reveal the same pattern.

    If we, humans, can do this to our own species imagine what a totally unrelated species, maybe millions of years in advance of us, might do to us? Its all well and good imagining that they may be benevolent but the chances are that they would be no more benevolent to us than we have been to our own kind.

    In any case, even if they did have some sort of ‘Galactic’ charter not to interfere with less developed species the simple exposure to their technology in itself would, most probably, destroy our present civilisation leaving the entire human race in much the same state as the many of the native tribes around the world from Alaska to the nomads of central Africa who’s traditional hunting and gathering skills. are rapidly failing simply because of what ‘advanced’ technology has done to the planet.

  22. Steve says

    David, I agree with most of your comments except this:

    “The simple fact is that if there are other intelligent tool using species in the Galaxy they are probably millions of years ahead of us, so much so that our crude attempts to contact them or find them are probably on no more interest to them than if an ant were to start waving a feeler in our direction!”

    You can’t make the assumption that a) if there is intelligent life in our galaxy it automatically has to be more advanced than us, they could be at any level of technology, we just don’t know b) they wouldn’t be interested in us because we are not as advanced as them. That’s like saying NASA should have no interest in finding microbial life on another world because they’re not as smart as us.
    We would represent a different culture, which, if they had any level of interest in exploring the cosmos in the first place, should be a fascinating discovery for them. Do we really need to be on the same technological level as them to be considered interesting?

    I know this is a controversial topic but I feel it is relevant to point out that whilst so many people argue that we haven’t been contacted by an advanced alien race yet, what if at least a small portion of these UFO sightings represent technology not from this world. Wouldn’t that be evidence of an advanced civilisation showing an interest in us. Not in a “Greetings Earthlings” kind of way but more from a surveillance point of view. Monitoring our behaviour from a safe distance so as not to interfere or put themselves in harms way.

    Just a thought.

  23. david pinnell says

    Yes of course Steve, you are right. But what I meant was that given that the Universe is so old its highly probable that there are thousands of civilisations at all levels of development from the Stone Age through to advanced technology.

    With our present knowledge of physics interstellar travel is impossilbe and I would guess that we have a very very long long way to go before it becomes so, it it is even possible..

    With this in mind I think it most likely that any civilisations capable of Interstellar travel are going to be very very far ahead of us, and that is what I meant when I said that we are probably too primitive to ‘bother’ with.

    I’m also interested in your comments about UFO’s and I have very mixed feelings about these. I have to say I have witnessed an Unidentified Flying Object. But I take it as that, ‘Unidentified’ what I and my wife saw, can not be expained but I have a very open mind about it and sure you could be right, maybe we are being observed.

  24. Steve says

    Hi David,

    I see where you’re coming from.

    Regarding the UFO topic, I have seen one as well, it was one of those black triangles you hear about. It was almost 20 years ago, 1988, around the time of the Belgium wave I think. Since then I have been intrigued. But I feel like you about this, to cry “aliens!” is a leap. What I saw wasn’t a conventional craft so it deserves the title of UFO, as yet, unidentified.

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