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.

Comments

Missing something

[Space cowboy]

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.

Wow

[FlyingSquidStudios]

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.