Last week, I posted an exceptional image of our home world as seen by the Suomi NPP Earth-observing satellite. The image was so popular that NASA released a second one, this time of the Eastern hemisphere, showing once again why it’s called the Blue Marble:

[Click to engaiaenate, or grab the terrestrialicious 11,500 x 11,500 pixel shot].

Like the other one, this is a mosaic, created over six different orbits — the bright north/south swaths are actually the reflection of the Sun in the ocean as the satellite passed over that area multiple times.

Although the satellite is in low Earth orbit, just a few hundred kilometers off the surface, the images have been mosaicked together to represent the view as if you were about 13,000 km (8000 miles) away. You’re seeing most of but not quite all of the entire hemisphere here. The inset image shows why; the farther you are from Earth the more of it you see.

If you’re having a hard time picturing that, imagine taking a camera and holding it a couple of centimeters from your floor. You only see a small section of the floor, right? Now take hundreds of pictures, moving the camera each time to get a different part of the floor. If you stitch those pictures together you have a complete image of your floor, even though it was too big to see from any individual shot. It’s as if you were hovering over the floor from higher up and took one shot.

That’s how this was done as well, though the pictures couldn’t just be stitched together; they had to be warped a bit to account for the Earth being round (near the Earth’s limb you’re seeing the ground at more of an angle than what’s directly below you). That’s why the image gives you such an overwhelming feeling of perspective, of actually being over the planet from all those thousands of kilometers away.

And I wonder… someday, our children may get this view every day, just by looking out a window. Every time I think about that, I get a chill. When I was a kid, that thought was science fiction. Now it’s maybe just a few more years down the road.

[UPDATE: Right after posting this, I got a feeling of deja-vu, and suddenly realized where I've seen this view of the Earth before: Apollo 17. What I wrote in that last paragraph is literally true: humans have seen this view before, and I hope that one day it will be routine to see it this way once again.]

Image credit: NASA/NOAA.

Thanks to astronaut Ron Garan on Google+, I was alerted to some amazing footage of the Moon setting as seen by astronauts on board the International Space Station. I uploaded it to YouTube and added some comments to show you something really cool…

[Set it to high-def and make it full screen!]

Astonishing, isn’t it? As the Moon sets, you’re seeing it through thicker and thicker air. The air acts like a lens, bending the light upward. The part of the Moon nearer the Earth’s limb gets bent up more, so the Moon looks like it’s getting flattened. Watch it again; the top of the Moon doesn’t appear to be affected much. It looks more like the bottom slows down and the top pushes into it. You can read about this effect in more detail in an earlier blog post.

Weirdly, as I watched the video, it looked very much like the whole Moon was shrinking as it set, as if it were receding rapidly. When I saw that I knew intuitively that couldn’t be real; the ISS is only moving a few thousand kilometers over the time this whole video was taken (about ten minutes), not nearly enough to see that big a change in the size of the Moon. It’s 400,000 kilometers away, after all! So I measured the size of the Moon on the screen, and incredibly the width doesn’t change. Do you see it appear to shrink too? It’s an illusion!

Funny how our brain interprets such things. As if seeing a gigantic rock moving through the sky while perched on board a football-field sized satellite moving at 30,000 km/hr isn’t weird enough!

Credit: Image Science and Analysis Laboratory, NASA-Johnson Space Center. "The Gateway to Astronaut Photography of Earth".

Just before Halloween last year, NASA launched into orbit the improbably named National Polar-orbiting Operational Environmental Satellite System Preparatory Project, which they thankfully shortened to NPP. In its low 800 km (500 mile) orbit it looks down at the Earth to investigate our environment. It only sees a portion of the Earth at any one time, but if you take observations taken during a single day — say, on January 4, 2012 — and stitch them all together, you get this magnificent shot:

[Click to engaiaenate, or download the Big McLarge Huge 8000 x 8000 pixel version.]

Man, the resolution is so high is like you’re actually there.

Oh wait.

In fact, the biggest version is 8000 pixels across, and the Earth is about 8000 miles wide, so the resolution is about a mile per pixel. We’re not seeing the entire hemisphere here, but the view is roughly 8000 km across (judging from the size of the US compared to the view). The big image is 8000 pixels wide, so the resolution of that mosaic is about 1 km/pixel. The Earth is big.

NPP was recently renamed Suomi NPP in honor of Verner Suomi, a pioneer in using satellites in meteorology. I like that we tend to name satellites and space probes after people whose work made those very missions possible, or for people we honor and respect (my favorite is still Sojourner, the Mars rover named after Sojourner Truth… with the bonus of the name being a pun).

Apropos of nothing, I’ll note the images making up this seamless mosaic were taken around the same time the Earth was at perihelion, when it was closest to the Sun in its orbit. There is nothing particularly important about that fact, but still… when I see pictures like this I think about how amazing our planet is, and how wonderfully well-adapted we are to it. Evolution is a stochastic process, a semi-random series of bumps and false starts that literally made us who were are today. But that doesn’t change the feeling of comfort I get when I see a picture of Earth, floating in space, sitting in the brightest and warmest sunlight of the year.

It’s home, and I’m glad we’re taking such a close look at it.

This summer will be a little bit longer than usual. A tiny little bit: one second, to be precise. The world’s official time keepers are adding a single second to the clocks at the end of June. This "leap second" is needed to keep various time scales in synch. It’s a bit of a pain and won’t really affect people much, but if it weren’t done things would get messy eventually.

This gets a bit detailed — which is where the fun is! — but in short it goes like this. We have two systems to measure time: our everyday one which is based on the rotation of the Earth, and a fancy-schmancy scientific and precise one based on vibrations of atoms. The two systems aren’t quite in synch, though, since the Earth counts a day as a tiny bit longer than the atomic clocks say it is. So every now and again, to get them back together, we add a leap second on to the atomic clocks. That holds them back for one second, and then things are lined up once again.

There. Nice and simple. But that’s spackling over all the really cool details! If you want a little more info, you can read the US Naval Observatory’s press release on this (PDF).

If you want the gory details, then sit back, and let me borrow a second of your time.

Time after time

There are lots of ways of keeping time. The basic unit day is based on the physical rotation of the Earth, and year is how long it takes to go around the Sun. But we need finer units than those! So we decided long ago to divide the day into 24 hours, and those into 60 minutes each, and those into 60 seconds each. In that case, there are 86,400 seconds in a day. OK, easy enough.

For most of us, that is enough. But scientists are picky (or "anal" if you want to be technical) and like to be more precise than that. And the thing is, the Earth is a bit of a sloppy time keeper. Tidal effects from the Sun and Moon, for example, slow it a bit. Other effects come in as well, changing the rate of the Earth’s rotation.

To account for this, in 1956 the International Committee for Weights and Measures made a decision: we’ll base the length of the second on the year, not the day. In fact, we’ll take the year as it was in the year 1900 (a nice round number, so why not) and say that the length of the second is exactly 1/31,556,925.9747 of the year as measured at the beginning of January 1900^*.

OK, fine. Now scientists have their anal precise definition, normal people have calendars, and we’re all happy, right?

Right?

Sunrise, sunset

Yeah. Not so much. (more…)

Astronomers have achieved a big milestone in the search for another Earth: the two smallest confirmed planets ever found orbiting another star… and they’re both about the size of Earth!

Artist’s illustration of the Kepler-20 planets with Earth and Venus for size comparison.

The planets are called Kepler-20e and Kepler-20f, and as you can see by the illustration above they are very close to the same size as our home world: 20e is about 11,100 km (6900 miles) in diameter, and 20f about 13,200 km (8200 miles) across. For comparison, Earth has a diameter of 12,760 km (7930 miles). This makes them the smallest confirmed exoplanets seen orbiting another star! The previous record holder was Kepler-10b, which has a diameter about 40% bigger than Earth’s.

To be clear: while these planets are the size of Earth, they are nowhere near Earth-like. The star, Kepler-20, is very much like the Sun, though a bit smaller and cooler (and 950 light years away). However, both planets orbit the star much closer than Earth does; 7.6 million km (4.7 million miles) and 16.6 million km (10.3 million miles), respectively. This is so much closer that both planets must have surface temperatures far hotter than ours, 760°C and 430°C (1400°F and 800°F). Even on the "cooler" planet Kepler-20f, it’s hot enough to melt tin and zinc.

So don’t start packing your bags to visit, even if you could spare a few million years to get there via rocket (950 light years is a bit of a hike). I’ll note that we don’t know the masses of these planets either. I’ll explain that in a moment, but given their sizes it’s expected they’ll have masses similar to Earth’s.

So this is very exciting! For one thing, it shows that Kepler can indeed find planets the size of Earth orbiting distant stars. That right away is fantastic; that’s the main goal of Kepler in the first place.

For another, it shows that our solar system is not entirely unique. We do know of several other stars hosting solar systems of their own, but those planets tend to be very massive; they’re easier for us to find. Since Kepler-20e and f are so close to Earth-sized, this is a big achievement.

And we’re still not done: there are three other planets in the Kepler-20 system! (more…)

When the Sun belches out an eructation of subatomic particles, they can travel across the solar system and interact with the Earth’s magnetic field. This can make our field ring like a bell, shaking the particles trapped within, and generating electromagnetic noise and signals across the radio spectrum. The CARISMA radio array can detect these emissions and learn about how the Sun’s and Earth’s fields interact.

That’s the science. But there’s art here, too: the Lighthouse agency commissioned artists to create digital artwork based on science, and one group, Semiconductor, used the CARISMA data to do so. Based on the data, they translated the radio waves (which are like the light we see, but less energetic) and converted them to sound. This has been done many times before, but what’s cool is that they then created an animation based on the converted sounds, an astonishing and odd and mesmerizing animation. Watch:

How wild is that? It reminds me of the movie "Forbidden Planet". The vibrating patterns are wonderful, and while I’m not sure how much scientific insight can be gained from them, the aesthetics are riveting. And I can hope the underlying purpose of this will be seen: to show that science is beauty, science is art, and that if this gets someone who might not otherwise be interested to poke a little further into it, then mission accomplished.