Ghost Nebula

NGC 6960 (Western Veil nebula) & Horsehead Nebula and the Flame Nebula

by David Wills

10 Spacetime Mysteries That Quantum Gravity Could Solve

“4.) In most approaches to quantum gravity, space-time is not fundamental but made of something else. That might be strings, loops, qbits, or some variant of space-time “atoms” which appear in condensed-matter based approaches. The individual constituents, however, can only be resolved when probed with extremely high energies, far beyond what we can achieve on Earth.”

What is the fundamental nature of the Universe? When it comes to General Relativity, our answer is matter and energy on one hand, and spacetime on the other. But there’s another side to that story: a quantum one. While matter and energy can be discretized into quanta, our notion of spacetime is purely classical. But depending on what our true, fundamental theory of quantum gravity actually is, it could have incredible implications for our Universe. Perhaps we have tiny little black holes popping in and out of existence on a continuous basis; perhaps the vacuum of space isn’t entirely transparent to light; perhaps time turns into space at some level; perhaps wormholes and baby Universes are real. These are mysteries that are currently unresolved, but quantum gravity could provide the answer.

What are the mysteries, and what does it all mean? Sabine Hossenfelder explores, with a fantastic video!

Dunes, peaks and craters on Mars obtained by HiRISE (High Resolution Imaging Science Experiment), a camera on board the Mars Reconnaissance Orbiter.

Image credit: NASA/JPL/University of Arizona

Image of Titan taken by the Cassini spacecraft

NASA/JPL-Caltech/SSI/Kevin M. Gill

Europa 

Jupiter’s moon Europa is slightly smaller than Earth’s moon. Its surface is smooth and bright, consisting of water ice crisscrossed by long, linear fractures. Like our planet, Europa is thought to have an iron core, a rocky mantle and an ocean of salty water beneath its ice crust. Unlike Earth, however, this ocean would be deep enough to extend from the moon’s surface to the top of its rocky mantle. Being far from the sun, the ocean’s surface would be globally frozen over. While evidence for this internal ocean is quite strong, its presence awaits confirmation by a future mission.

Europa orbits Jupiter every 3.5 days and is locked by gravity to Jupiter such that the same hemisphere of the moon always faces the planet. Because Europa’s orbit is slightly stretched out from circular, or elliptical, its distance from Jupiter varies, creating tides that stretch and relax its surface. The tides occur because Jupiter’s gravity is just slightly stronger on the near side of the moon than on the far side, and the magnitude of this difference changes as Europa orbits. Flexing from the tides supplies energy to the moon’s icy shell, creating the linear fractures across its surface. If Europa’s ocean exists, the tides might also create volcanic or hydrothermal activity on the seafloor, supplying nutrients that could make the ocean suitable for living things.

Europa Clipper

NASA’s planned Europa Clipper would conduct detailed reconnaissance of Jupiter’s moon Europa and investigate whether the icy moon could harbor conditions suitable for life.

The mission would place a spacecraft in orbit around Jupiter in order to perform a detailed investigation of the giant planet’s moon Europa – a world that shows strong evidence for an ocean of liquid water beneath its icy crust and which could host conditions favorable for life. The mission would send a highly capable, radiation-tolerant spacecraft into a long, looping orbit around Jupiter to perform repeated close flybys of Europa. NASA has selected nine science instruments for a future mission to Europa. The selected payload includes cameras and spectrometers to produce high-resolution images of Europa’s surface and determine its composition. An ice penetrating radar would determine the thickness of the moon’s icy shell and search for subsurface lakes similar to those beneath Antarctica’s ice sheet. The mission would also carry a magnetometer to measure the strength and direction of the moon’s magnetic field, which would allow scientists to determine the depth and salinity of its ocean.

Image credit: NASA / JPL / Galileo / Voyager & Processed by Kevin M. Gill

Credit: NASA & Europa Clipper Mission

The Space Shuttle Challenger at a foggy Cape Canaveral, 1984.

(NASA/Department of Defense)

The missing links between galaxies have finally been found. This is the first detection of the roughly half of the normal matter in our universe – protons, neutrons and electrons – unaccounted for by previous observations of stars, galaxies and other bright objects in space.

Flying Monsters of Scorpius | Yuriy Toropin

Saturn photographed by the Cassini spacecraft in 2014

Image credit: NASA/JPL/Cassini; precessed by: Ian Regan

ISS | Credit: NASA

Time-lapse imagery captured June 25, 2017 by Expedition 52.