Earth and Moon From an Alien's Perspective
krygny writes "NASA's Deep Impact spacecraft (whose extended mission is called EPOXI) has created a video of the moon transiting Earth as seen from 31 million miles away. Scientists are using the video to develop techniques to study alien worlds. 'Our video shows some specific features that are important for observations of Earth-like planets orbiting other stars,' said Drake Deming of NASA's Goddard Space Flight Center... 'A "sun glint'" can be seen in the movie, caused by light reflected from Earth's oceans, and similar glints to be observed from extrasolar planets could indicate alien oceans. Also, we used infrared light instead of the normal red light to make the color composite images, and that makes the land masses much more visible.'" Here are links to the two videos, one red-green-blue and the other infrared-green-blue.
Perhaps I am, but 31,000,000 miles doesn't seem that far away from an astronomical perspective - in fact it seems pretty darn close. A single light-year is about 5,878,625,373,183.61 miles (from Wiki), so 31M miles is roughly 1/190,000 of a light year.
The nearest star is ~4.2 light years away, so our potential alien visitor would have to travel a very long way towards us (and in that case why not come the last 0.0001% of the journey!) before this was a useful property.
Now I realise you can only take a video from as far away as your spacecraft really is, but I'd expect to see extrapolations to realistic distances before you start to claim things like "Making a video of Earth from so far away helps the search for other life-bearing planets in the Universe". - that's a bold claim, after all. I'm sure there's a standard line somewhere about extraordinary claims requiring extraordinary evidence to back them up...
I dunno, perhaps I'm just a grumpy old physicist, but there's all sorts of effects that only come into play at astonomical-scale distances (and the relativistic-scale speeds that commonly occurs between bodies that far apart), I guess I'd like to have seen more data and less hand-waving.
Simon.
Physicists get Hadrons!
I wish Sagan could be here to see this.
Edward@Tomato - /home/Edward/ man woman
man: no entry for woman in the manual.
"Qua!?"
I was going to post the usual attempt at witty snarkiness, but then I actually watched the video... seeing the Moon actually moving around the Earth like that, it actually made my heart skip a beat. Seeing us that way with my own eyes someday, as unlikely as it may be, is something I really long for.
http://twitter.com/OLDTELEGRAM
What, they couldn't just take pictures of Earth from the moon, resize them, and then photoshop the moon on top? I mean I'm all for NASA, but this seems pretty useless. "Seeing the earth will help us understand aliens!" I'm not buying it.
GCS/MU/P d- s:- a-- C++++$ UL++ P+ L++ E+ W++ N o K- w--- O M+ V- PS+++ PE Y+ PGP t+ 5- X R++ tv+ b++ DI++ D++ G+ e++ h-
That's cool but then again, I'm a sucker for any movie I'm actually in.
..I can see my house from there!
Huh? Did he just say that habitable planets must have large moons? (I've heard a similar argument before - something about two widely spaced bodies keeping the big one from wobbling too much.)
...harmless
Here you go, grumpy old man ; )
http://www.youtube.com/v/AFks9A9TCF0&hl=en&fs=1
"Kill 'em all and let Root sort 'em out"
Whoops, reached my limit for "That's no moon" comments in a single day. No no, don't get up. I'll show myself out.
Tic-Tac-Toe, Global Thermonuclear War, and relationships all have the same winning move.
A video like that really helps you realize how small and insignificant you really are.
The world keeps spinning, doing what it's doing, no matter what you do. We're all just bacteria on the proverbial fruit.
Also, we used infrared light instead of the normal red light to make the color composite images, and that makes the land masses much more visible.
Sigh...everything's gotta be special effects these days...
Have you read my blog lately?
Amazing.
Watching the video, I thought how cool it would be if you could see the Sun on the same scale. What size and how far away would it appear? The sun would obviously be located on the far far right somewhere.
I suspect a large enough display to show the three at once isn't possible yet (never mind the kind of camera lens you would need to take such a video) but I'm sure it would be a beautiful sight to see. For me it would really put into perspective just how massive the sun is compared to Earth.
31e6 mi = 1/3 AU
Has anyone out there converted these videos to something a little more standard? Quicktime .mov files aren't exactly accessable. Especially when some of us still refuse to install that blasted quicktime crap.
Disclaimer: The opinions and actions of the US Gov't are in no way representative of those held by this author or its ci
Anyone got FMV versions of these videos? I don't have Quicktime installed on my work (Windows) laptop, and would rather not jump through all those hoops just to view what sounds like an interesting vid.
(Alternatively, I can wait until I get home from work and use Gplayer.)
God invented whiskey so the Irish would not rule the world.
Go watch Sunshine, that movie definitely evoked those same kind of feelings in me.
There's an amazing scene where they watch Mercury transit across the Sun, and while we admittedly have the same view from here on Earth, imagining those folks were really on their way to the heart of the solar system, with one last, tiny gatekeeper between them and the monster that is the Sun is just AWESOME.
Goose-bump city.
With the first link, the chain is forged.
.mov is QuickTime, which is old and not proprietary; I have a book here describing the format. However, that's just the container format; it's the codecs commonly used within QT these days that are proprietary.
And according to mplayer, the codecs used here are mp4v for video, and aac for audio. In other words, (tada!) MPEG.
Just out of curiosity, what bit of rigor ensures that those "extrasolar planets" we're detecting so many lightyears from home are actually resolved images, and not averages of four or five similar, but smaller, objects? It's really unclear to me that the Galilean moons of Jupiter could ever be resolved as four objects and not one "giant moon" from as far away as a half a lightyear.
``Tension, apprehension & dissension have begun!'' - Duffy Wyg&, in Alfred Bester's _The Demolished Man_
That a YouToob video got /.ed
Seven Days with Ubuntu Unity
Is there a GNOME (Ubuntu) screensaver that shows a realistic model (in scale, accurate surfaces) of the Earth and Moon orbiting each other?
I'd like to see our system from an alien's perspective whenever I've stopped working for a few minutes. Really give me the feeling of being "away from my desk".
--
make install -not war
When we look up at the moon, it moon looks like a pretty bright, reflective object. But in images containing both the earth and moon, you can see that the moon looks positively dim and dingy compared to the cloud-covered portions of Earth.
That that is is that that that that is not is not.
Looks beautiful.
MPEG non-proprietary?
MPEG2 maybe, but only because the patents have died.
Think before you post.
I am very small, utmostly microscopic.
That video is pretty cool, but didnt anyone else get a really creedy feeling as the moon passed by? Weird...
Yup, but to me (and damn near 100% of everyone else), you're really close to nothing. Outside of this planet, you're even closer to nothing.
Hence, insignificance.
I tend to consider aliens capable of traveling distances we consider in light years to be beyond use of such measurements. Infinity is infinity, therefore scale just goes way beyond comprehension. We consider such distance's as a very long road ahead whereby an alien might not even consider a distance but to know were the door knob is.
Marked for demolishment for intergalactic highway !
This is definitely my favorite JPL photo: http://marsrovers.jpl.nasa.gov/gallery/press/spirit/20050610a.html
If this alien perspective is awesome, thought provoking (or at least makes one pause for reflection) consider what the view would've been like from "Triana".
That was the space probe proposed by Al Gore in 2000 that was an earth looking satellite to be placed at the earth-SUN (not moon!) L1 point. This would've allowed it to have a continual, full on view of the sunlit side of the earth; it would've been invaluable for climate studies, weather forecasting, solar studies (how much sunlight is ACTUALLY reaching us) etc.
Of course our anti-intellictual/anti-science president cancelled it. Anyway, I would imagine the lunar transits would be spectacular, in fact we would almost be getting two missions for the price of one (because the instruments would only need be slightly redirected to image the moon).
I don't know enough about astronomy to know how close the plane of the moon's orbit is to the plane of the earth's orbit but there should be occasional transits which, in addition to being pretty, would also give us information about atmospheric attenuation (when the earth passes in front of the moon).
Now the soap box-
As an American it is so depressing when I see how the average person has come to think of intellectual as a dirty word. America is losing its greatness because it is embracing faith over reason, guts over brains, instinct over analysis. Already biotechnology is moving overseas; today you can get your dog cloned in Korea (why isn't that a slashdot story?) tomorrow maybe your heart or liver. The cancellation of this space probe was just the start of the country's fall over the last seven years.
And no, Al Gore isn't an Alien and yes he did have a hand at a critical phase of the Internet's development. (In 1993 I got a $100K grant from the NTIA which he set up).
Actually the "sun glint" is not from the oceans but from all the tin-foil hats. :)
I'm confused about how seeing the Moon transit Earth is relevant to extrasolar planetary observation. I thought that we were detecting extrasolar planets by tracking the wobble they induce in their star, not by direct observation of light reflected from the planet. If so, then how will dimming of the planet by a transiting moon be observable?
I thought the cutting edge in astronomy was the idea of a giant space telescope that might directly observe superjovian gas planets, not Earth-like planets.
Umm, is it just me or does the orbit of the Moon (the path it takes across the screen) not really match the rotation of the Earth? There seems to be a good 30 degrees of offset between the axis of rotation of the Earth and the axis of the orbit of the Moon. Shouldn't those two be fairly close? (Flame shields up!)
Could you please upload it to youtube? I don't have mplayer installed on my machine.
This is what he actually said: ""Making a video of Earth from so far away helps the search for other life-bearing planets in the Universe by giving insights into how a distant, Earth-like alien world would appear to us," said University of Maryland astronomer Michael Aâ(TM)Hearn"
What he is indicating by that, is not that habitable planets *must* have large moons, but simply that, knowing what a habitable planet that *does* have a large moon (ours) looks like from a distance, will help us disern similar such planetary arrangements.
Nowhere in that is he trying to make a "habitable planet MUST HAVE large moon ELSE no life" statement.
Or are you reading something different than I am?
Looks fake.
"Are you being sarcastic?" "I can't even tell anymore."
Populus vult decipi, ergo decipiatur...
"Force shits upon Reason's back." - Poor Richard's Almanac
Oceans? We though you had covered 70% of your planet with blue tarps.
Definitely a low class neighborhood. Move along now.
Have gnu, will travel.
Hi, ScienceTim here, from the EPOXI team. Let me correct some misconceptions. The purpose of this experiment is to make a measurement of the Earth's spectrum at low spectroscopic resolution that allows us to simulate what an observer would detect from outside the solar system. Although we have spatial resolution in this movie, our scientific results will be obtained by adding up all the light in each of our filters in order to explore the ability to deduce properties of the Earth in unresolved data (we actually have 7 filters, not just the 4 that we show, plus a near-IR spectrometer). This information can be used to evaluate the engineering requirements for future space missions that will have the actual purpose of detecting and characterizing extrasolar terrestrial planets. Such a mission will be able to collect very few photons, so it will be required to do its job with very limited information. Why not just simulate the Earth computationally, since we know a great deal about it? We do this, of course. Converting our detailed knowledge into an accurate simulation is not straightforward, however. Radiative-transfer techniques employ a variety of approximations, depending on the situation, and those approximations may require us to know something that would not be available for an actual extrasolar planet -- as an easy example, the pressure scale height is important for some methods. The EPOXI observation, and others like it that we acquired on earlier and later dates, provide an empirical test for those models. Once we have an empirically-tested model verified, we can apply the techniques from that model to the problem of modeling the apparent spectrum of nearly-Earthlike and not-at-all Earthlike terrestrial planets. Keep in mind that this measurement is an interesting and useful exercise in the value of empirical test, but it is not the primary mission element. Currently, the primary mission element is observations of stars with known planets, to investigate these systems more deeply. We will finish in another month or so. Then we cruise for about a year, then we have a close flyby of another comet, after which the mission will be over. We have lots of good stuff coming.
Why does the moon not have a bright side like the Earth did, in that video? It almost appears as if the moon is in the shadow of something. Could it be that the moon doesn't reflect IR the same way the Earth does?
Authority questions you. Return the favor.
Why not go with the simplest explanation. First of all space is vast and huge with limitless possibilities both bad and good. Thus assuming there is some alien society capable of navigating the great reaches to meet us is a pretty big assumption why not make it simple.
I simple society that does not share in our challenges. Lets say a biologic that reproduces asexually, and has long gestation periods. A simple cocoon cable of reflecting harmful radiation catapulted from there home asteroid which has limited gravity.
the whole time they are just being hurled through open space. Lets then say they launch millions of ships instead of just one using probability to navigate space.
Thus your alien who will use limitted sensory levels (visual ?) to identify a water base dplanet ?
mind you, it's a bit of a shock to see just how dark and brown the moon really is... we're dazzled by it and it looks so bright against the night sky...
Donald 'Duck' Dunn: We had a band powerful enough to turn goat piss into gasoline.
There, that's better :)
Not correct.
First off, given the currently understood process by which planetary systems form, giant collisions are inevitable. There isn't a single non-tidally locked planetary body in the solar system that doesn't have an axis tilted relative to the ecliptic (even Jupiter!) In fact, as the Jupiter example shows, it's not obvious that a body, even during the accretion phase, will end up with zero tilt. As mass accretes to a growing planetoid, it's unlikely that all of the angular momentum of the impacting material will perfectly average out to match exactly that of the Sun.
Secondly, gravitational interactions between bodies in the solar system, over billions of years, will cause axial wobble. The planets themselves are in elliptical orbits about the Sun that are not coplanar. So their gravitational effects will be oriented at some angle to their rotational axes even if they had zero tilt relative to the ecliptic. Any mass variation in these bodies therefore will experience differential pull. For any non-rigid body, which applies to all of the large bodies in the solar system at some point in their history, there is uneven distribution of mass inside them which changes over time.
What the Moon did for us, at the "cost" of tidal braking is produce a local gravity well whose effects are much larger than the other influences on our axial tilt, so that these effects primarily result in precession of the tilt axis rather than changes to its overall value. However, this is largely a chance development based on the particular mass ratio between the bodies and the configuration of our solar system. If the Earth-Moon system orbited closer to a jovian with a large inclination, the overall effect could have been to de-stabilize the rotational axis.
Wiki has useful page on this topic:
http://en.wikipedia.org/wiki/Axial_tilt
I can't open the thing in Windows Media Player, I can't open it in Real Player, and Digital Media Converter is telling me that I have to install Quacktime before it will convert the thing.
And I fscking refuse to install Quacktime.
FSCK THIS SHIZNAT.
AND FSCK THESE TAX-PAYER SUBSIDIZED, STEVE-JOBS'S-@$$-KISSING C*CKSUCKERS WHO ENCODE TO THIS PROPRIETARY SHIZNAT.