North polar hexagon of Saturn
Just like our Earth, many differientiated proto-planets consisted of a silica and olivine rich mantle surrounding a very dense iron-nickel core. It is thought that pallasites (which are composed of olivine embedded in an iron-nickel matrix) are derived from the boundary between the Mantle and Core.
We believe that the most likely scenerio for the creation of the pallasites was a cataclysmic impact event that penetrated deep enough to remove both mantle and core material which was mixed in a liquid state. This mixture of iron-nickel and olivine then cooled over millions of years in the zero gravity environment of space to produce the stunningly beautiful meteorites known as Pallasites.
Fascinating. All the universe is math.
The curvature of spacetime is described by a type of object called a field - which really just means it’s a set of numbers (matrices, in particular) with some value at each point in space and time, each saying how much curvature there is in various directions. There are lots of other fields - the electromagnetic field is a famous one - and while the spacetime field is certainly special, since it describes the background that all the other fields move on, it’s nonetheless the same kind of thing fundamentally.
Quantum theory tells us that fields and particles are inextricably linked - particles are nothing other than energetic excitations in a field. So just as the excitations or ripples in the electromagnetic field give rise to electromagnetic waves, or photons, so we expect the gravitational field to give rise to particles called gravitons. We already know half the story, we know that spacetime has classical (i.e., non-quantum) ripples called gravitational waves that are very much analogous to electromagnetic waves, and we know that when you throw quantum mechanics in the mix, the electromagnetic waves become photons.
But there are various technical difficulties with taking Einstein’s theory of spacetime and making it work as a quantum theory. As I said, they’re quite technical, but they have to do with the fact that at higher and higher energies, the theory “blows up” and starts spitting out infinities, making it impossible to calculate anything.
A composite of 31 different images, taken in the shadow of the solar eclipse that passed over Asia and parts of the Pacific for 6 minutes and 39 seconds. That’s the longest solar eclipse anyone on Earth will witness this century; a longer one isn’t coming until 2132.
The photo shows the solar corona that make up the sun’s “atmosphere” in glorious detail. Its whorls and loops extend millions of miles into space, are nearly 200 times hotter than the visible surface of the sun, and yet aren’t nearly as bright (by a factor of something like a million), hence, we can only see them during eclipses.
The Galactic Centre. Every dot is a star. Photo from 2MASS. Click image for hi-res.
Near Santa Cruz, Bolivia, the radial-pattern fields are part of a planned settlement scheme in a rainforest area. At the centre of each unit is a small community, which is surrounded by fields. A small buffer of forest separates the settlements from one another
Outside Bangkok, Thailand, rice fields fed by an extensive network of canals that is hundreds of years old appear as skinny rectangular fields. Some fields seem to be flooded (deep purple), which is part of the growing cycle of rice plants
South of Khartoum, Sudan, where the White and Blue Nile rivers join, a dizzying arrangement of irrigated fields stretches out across the state of El Gezira. Given the semi-arid climate of the surrounding area, this geometrical spectacle of fertile green fields depends on thousands of miles of canals and ditches that connect the region to the Blue Nile in the west. The man-made rivers and streams are part of an irrigation project called the Gezira scheme, which the British started in the colonial era to grow cotton for export back to Europe
John Young, Commander of Apollo 16 driving the Lunar Roving Vehicle (LRV). Filming is Charlie Duke, the Lunar Module Pilot.
It was at the end of their stay on the moon, and NASA wanted some footage of the LRV being put through it’s paces to see how it performed. By all accounts it was an excellent vehicle, able to climb hills with ease.
An unprecedented new look at our planet at night. A global composite image, constructed using cloud-free night images from a new NASA and National Oceanic and Atmospheric Administration (NOAA) satellite, shows the glow of natural and human-built phenomena across the planet in greater detail than ever before.
A timelapse of Planet Earth from Electro-L, a geostationary satellite orbiting 40000km above the Earth. The satellite creates a 121 megapixel image every 30 minutes with four visible and infrared light wavelengths. The infrared light appears orange in these images, and shows vegetation. The images were obtained beginning on May 14th, 2011 and end on May 20th. The images are the largest whole disk images of our planet, the resolution is 1 kilometer per pixel.