Want to Learn SQL? Here is a Great Tutorial!

Mode Analytics, a recently launched site for collaborative data science in the cloud, has published an excellent tutorial for learning SQL.

The tutorial is named SQL School .

This is one of the best SQL tutorials I have seen. Plus, it has the huge added advantage of not requiring you to setup your own database first (the data is already available). Setting up your own database can be a bit overwhelming when you are first learning. So, if you are looking to learn SQL, now is a great time to start.

Are the Earth's magnetic poles about to flip?

Over the past six months, the Earth’s magnetic field has been weakening 10 times faster than in previous years, reports the European Space Agency (ESA). The recent changes may indicate that the Earth's magnetic poles are about to flip.

The magnetic field, which has been described as a huge bubble that protects the Earth from incoming cosmic radiation and solar winds, is always changing and ESA’s Swarm mission has been tracking these fluctuations since November 2013. 

The magnetic poles flip every few hundred thousand years and changes in the strength of the magnetic field are part of the cycle, but what is striking is the rate at which it is weakening. “Researchers estimated the field was weakening about 5 percent per century, but new data revealed the field is actually weakening at 5 percent per decade, or 10 times faster than thought,” explains Kelly Dickerson at LiveScience.

Scientists expect the next flip in about 2,000 years, but at this rate it may happen sooner. What does it mean for humans? Compasses could point south instead of north for the first time in more than a hundred thousand years, and grids and communication may be affected.

According to LiveScience, the biggest weak spots in the magnetic field have been found over the Western Hemisphere, but it has strengthened over the southern Indian Ocean since January 2014. The latest measurements, as ESA states in a news release, suggest the movement of the magnetic North towards Siberia.

Over the next few months, researchers will continue to analyse Swarm’s data to see how the mantle, crust, oceans, ionosphere and magnetosphere may be contributing to these change.

Two Earth-like Planets Never Actually Existed

Publishing in the journal Science, lead author Paul Robertson from Penn State University in the US declared that Gliese 581g doesn’t exist, and neither does another planet in the same solar system, known as Gliese 581d.

Discovered in 2009 and 2010 based on signals from their home star, Gliese 581 - which is a dim red dwarf sitting 22 light-years away from Earth and with a third of the mass of our Sun - Gliese 581g and Gliese 581d were at the time a momentous discovery. Gliese 581g in particular, because calculations of what its size and temperature would be suggested that it could potentially be hospitable to life, if it had a rocky surface. Scientists called it within the habitable, or 'Goldlilocks’, zone, because it wasn’t too hot, it wasn’t too cold, it was just right for life. 

Because these planets were assumed to be too close to their star to be seen directly with telescopes, astronomers Paul Butler from the Carnegie Institution for Science and Steven Vogt of the University of California, both based in the US, watched for the subtle wobbles created by the gravity of these planets as they orbited around Gliese 581 and tugged back and forth on it.

"The time it took the ‘planet' to complete one orbit (37 days) told them how far it was from the star,” says Michael D. Lemonick at National Geographic. "In the case of this cool star, that was 'just at the right distance to have liquid water on its surface', Butler said at the time. The strength of the tugging, meanwhile, told them the planet was about three times as massive as Earth."

The Known as the 'Doppler Method', this technique of finding planets is not nearly as accurate as another technique used by the Kepler Space Telescope, which is based on the shadows cast by planets on their stars as they orbit around them. The Kepler Space Telescope has discovered over 3,000 planets and planet-candidates since 2009 using this method.

Robertson and his team weren’t convinced by the evidence offered up by Butler, Vogt, and the Doppler Method, so they studied the emissions coming off the red dwarf star to see what clues they could give. 

Jason Koebler at Motherboard explains:

“The team says that the false readings that were originally believed to be planets were actually due to intense magnetic activity on the star itself - much like sunspots on the Sun. This crazy intense activity created false positives for planets d and g. When Robertson studied the sodium and hydrogen emissions coming off the star, that much became obvious.”

Based on what they found, Robertson concluded that the existence of 581d is an "artefact of stellar activity which, when incompletely corrected, causes the false detection of planet g". 

This is because the existence of Gliese 581g was based on the gravity that Gliese 581d exerted on it, which has now proven to not exist, says Koebler. "In fact, Robertson writes that the existence of planet g 'was simply leftover noise created by stellar activity'. Poor guy."

"It's unfortunate that the other planets don't exist," said co-author Suvrath Mahadevan, also from Penn State University. "But the important takeaway is that stellar activity is an important source of contamination, and that we can [now] take it into account."