How can we know the size, composition, and atmospheric makeup of distant exoplanets? NASA explains the details in this Alien Atmospheres video.
By observing periodic variations in the parent star’s brightness and color, astronomers can indirectly determine an exoplanet’s distance from its star, its size, and its mass. But to truly understand an exoplanet astronomers must study its atmosphere, and they do so by splitting apart the parent star’s light during a planetary transit.
Watch more astronomy videos, including Measuring the Universe and The Hubble Ultra Deep Field.
via Boing Boing.
Sea Level! What is it and how do scientists calculate it? As it turns out, there are actually many complexities in determining this measurement. For example, Earth isn’t actually a sphere, gravity is stronger and weaker at different points around the globe, and of course, there are a lot of mountains that are no where near water — so how do we know what sea level would be? In this video, Minute Physics explains the details.
After you’ve watched, check out these related links: ellipsoid, geoid, geodesists, Mount Everest, Chimborazo Volcano, Space.com’s Best Gravity Map Yet Shows a Lumpy, Bumpy Earth, and this clarifying and not-to-be-missed animated gif of Earth’s gravity field.
In the archives: videos about or involving measuring things, including Measuring the Universe.
What did Mars look like 4 billion years ago? The team at NASA’s Conceptual Image Lab have an idea based on the existing evidence:
Billions of years ago when the Red Planet was young, it appears to have had a thick atmosphere that was warm enough to support oceans of liquid water - a critical ingredient for life. The animation shows how the surface of Mars might have appeared during this ancient clement period, beginning with a flyover of a Martian lake. The artist’s concept is based on evidence that Mars was once very different. Rapidly moving clouds suggest the passage of time, and the shift from a warm and wet to a cold and dry climate is shown as the animation progresses. The lakes dry up, while the atmosphere gradually transitions from Earthlike blue skies to the dusty pink and tan hues seen on Mars today.
The animation was released in anticipation of November 18th’s Cape Canaveral launch of MAVEN, Mars Atmosphere and Volatile Evolution mission. MAVEN will explore the planet’s lost atmosphere.
Previously: flying over a topographically accurate landscapes of Mars, and more NASA.