Ode To Apollo 11 And The Joy Of Discovery

Toute la nuit sous la lune ronde à faire le tour de l'étang

Bashô / © Pascal Picco, Pleine lune du mercredi 8 avril 2020

The leisurely pace of light speed

In a 45-minute video called Riding Light, Alphonse Swinehart animates the journey outward from the Sun to Jupiter from the perspective of a photon of light. The video underscores just how slow light is in comparison to the vast distances it has to cover, even within our own solar system. Light takes 8.5 minutes to travel from the Sun to the Earth, almost 45 minutes to Jupiter, more than 4 years to the nearest star, 100,000 years to the center of our galaxy, 2.5 million years to the nearest large galaxy (Andromeda), and 32 billion years to reach the most remote galaxy ever observed.1 The music is by Steve Reich (Music for 18 Musicians), whose music can also seem sort of endless.

If you’re impatient, you can watch this 3-minute version, sped up by 15 times:

This isn’t strictly true. As I understand it, a photon that just left the Sun will never reach that most remote galaxy.↩

The Last Shuttle, Dan Winters

Strange moons

Stunning, trippy 1970s NASA concept art for future space colony designs. Available (plus many more) in super hi-res here (and copyright free), for all your desktop wallpaper and/or prog-rock album cover needs. (via io9)

Rotate

Curiosity’s Marsian panoramas.

The Moon in Motion

Happy New Year! And happy supermoon! Tonight, the Moon will appear extra big and bright to welcome us into 2018 – about 6% bigger and 14% brighter than the average full Moon. And how do we know that? Well, each fall, our science visualizer Ernie Wright uses data from the Lunar Reconnaissance Orbiter (LRO) to render over a quarter of a million images of the Moon. He combines these images into an interactive visualization, Moon Phase and Libration, which depicts the Moon at every day and hour for the coming year. 

Want to see what the Moon will look like on your birthday this year? Just put in the date, and even the hour (in Universal Time) you were born to see your birthday Moon.

Our Moon is quite dynamic. In addition to Moon phases, our Moon appears to get bigger and smaller throughout the year, and it wobbles! Or at least it looks that way to us on Earth. This wobbling is called libration, from the Latin for ‘balance scale’ (libra). Wright relies on LRO maps of the Moon and NASA orbit calculations to create the most accurate depiction of the 6 ways our Moon moves from our perspective.

1. Phases

The Moon phases we see on Earth are caused by the changing positions of the Earth and Moon relative to the Sun. The Sun always illuminates half of the Moon, but we see changing shapes as the Moon revolves around the Earth. Wright uses a software library called SPICE to calculate the position and orientation of the Moon and Earth at every moment of the year. With his visualization, you can input any day and time of the year and see what the Moon will look like!

2. Shape of the Moon

Check out that crater detail! The Moon is not a smooth sphere. It’s covered in mountains and valleys and thanks to LRO, we know the shape of the Moon better than any other celestial body in the universe. To get the most accurate depiction possible of where the sunlight falls on the lunar surface throughout the month, Wright uses the same graphics software used by Hollywood design studios, including Pixar, and a method called ‘raytracing’ to calculate the intricate patterns of light and shadow on the Moon’s surface, and he checks the accuracy of his renders against photographs of the Moon he takes through his own telescope.

3. Apparent Size 

The Moon Phase and Libration visualization shows you the apparent size of the Moon. The Moon’s orbit is elliptical, instead of circular - so sometimes it is closer to the Earth and sometimes it is farther. You’ve probably heard the term “supermoon.” This describes a full Moon at or near perigee (the point when the Moon is closest to the Earth in its orbit). A supermoon can appear up to 14% bigger and brighter than a full Moon at apogee (the point when the Moon is farthest from the Earth in its orbit). 

Our supermoon tonight is a full Moon very close to perigee, and will appear to be about 14% bigger than the July 27 full Moon, the smallest full Moon of 2018, occurring at apogee. Input those dates into the Moon Phase and Libration visualization to see this difference in apparent size!

4. East-West Libration

Over a month, the Moon appears to nod, twist, and roll. The east-west motion, called ‘libration in longitude’, is another effect of the Moon’s elliptical orbital path. As the Moon travels around the Earth, it goes faster or slower, depending on how close it is to the Earth. When the Moon gets close to the Earth, it speeds up thanks to an additional pull from Earth’s gravity. Then it slows down, when it’s farther from the Earth. While this speed in orbital motion changes, the rotational speed of the Moon stays constant. 

This means that when the Moon moves faster around the Earth, the Moon itself doesn’t rotate quite enough to keep the same exact side facing us and we get to see a little more of the eastern side of the Moon. When the Moon moves more slowly around the Earth, its rotation gets a little ahead, and we see a bit more of its western side.

5. North-South Libration

The Moon also appears to nod, as if it were saying “yes,” a motion called ‘libration in latitude’. This is caused by the 5 degree tilt of the Moon’s orbit around the Earth. Sometimes the Moon is above the Earth’s northern hemisphere and sometimes it’s below the Earth’s southern hemisphere, and this lets us occasionally see slightly more of the northern or southern hemispheres of the Moon! 

6. Axis Angle

Finally, the Moon appears to tilt back and forth like a metronome. The tilt of the Moon’s orbit contributes to this, but it’s mostly because of the 23.5 degree tilt of our own observing platform, the Earth. Imagine standing sideways on a ramp. Look left, and the ramp slopes up. Look right and the ramp slopes down. 

Now look in front of you. The horizon will look higher on the right, lower on the left (try this by tilting your head left). But if you turn around, the horizon appears to tilt the opposite way (tilt your head to the right). The tilted platform of the Earth works the same way as we watch the Moon. Every two weeks we have to look in the opposite direction to see the Moon, and the ground beneath our feet is then tilted the opposite way as well.

So put this all together, and you get this:

Beautiful isn’t it? See if you can notice these phenomena when you observe the Moon. And keep coming back all year to check on the Moon’s changing appearance and help plan your observing sessions.

Follow @NASAMoon on Twitter to keep up with the latest lunar updates. 

Make sure to follow us on Tumblr for your regular dose of space: http://nasa.tumblr.com.

50 Lovingly Restored Photographs of the Earth Taken by Apollo Astronauts

For his Earth Restored project, Toby Ord digitally remastered 50 photographs of the whole Earth taken by Apollo astronauts during their missions in the 60s and 70s.

The Apollo photographs are historic works of art. So in restoring them, I sought to bring out their own beauty. I refrained from recomposing the images by cropping, or trying to leave my own mark or interpretation. Perhaps in some cases this would make a more pleasing image, but it was not my aim.

And the Apollo photographs are also a scientific record of what our Earth looks like. In particular, what it would have looked like from the perspective of the astronaut taking the shot. So rather than pumping the saturation or adjusting the colours to what we think the Earth looks like, I wanted to allow us to learn from these photographs something about how it actually appears.

Many of these shots are new to me – the Apollo program and its scientific and cultural output continue to be revelatory 50 years later. (My only quibble here: the images on the website are not high-res. Would love to see much bigger versions of these.)