Thursday, December 17, 2020

Gaia’s stellar motion for the next 1.6 million years

The stars are constantly moving across the sky. Known as proper motion, this motion is imperceptible to the unaided eye but is being measured with increasing precision by Gaia. This animation shows the proper motions of 40 000 stars, all located within 100 parsecs (326 light years) of the Solar System. The animation begins with the stars in their current positions; the brightness of each dot representing the brightness of the star it represents.

As the animation begins, the trails grow, showing how the stars will change position over the next 80,000 years. Short trails indicate that the star is moving more slowly across the sky, whereas long trails indicate faster motion. To avoid the animation becoming too difficult to interpret, the oldest parts of the trails are erased to only show the newer parts of the stellar motions into the future.

Sometimes it appears as if a star is accelerating (as indicated by a longer trail). This is due to the star getting closer to us. Proper motion is a measure of angular velocity, which means that close-by stars appear to move more quicker across the sky even when their speed is the same as that of other, more distant stars.

Towards the end of the animation, the stars appear to congregate on the right side of the image, leaving the left side emptier. This is an artefact and is caused by the average motion of the Solar System with respect to the surrounding stars.

The animation ends by showing star trails for 400 thousand years into the future.

Saturday, December 12, 2020

Cameras and Lenses

Over the course of this article we’ll build a simple camera from first principles. Our first steps will be very modest – we’ll simply try to take any picture. To do that we need to have a sensor capable of detecting and measuring light that shines onto it.

Saturday, December 5, 2020

Your Smart TV is probably ignoring your PiHole

Smart devices manufacturers often “hard-code” in a public DNS server, like Google’s, and their devices ignore whatever DNS server is assigned by your router - such as your PiHole.

Nearly 70% of smart TVs and 46% of game consoles were found to contain hardcoded DNS settings - allowing them to simply ignore your local network’s DNS server entirely. On average, Smart TVs generate an average of 60 megabytes of outgoing Internet traffic per day, all the while bypassing tools like PiHole.

Thursday, December 3, 2020

AI Generated Music

We started with the original SampleRNN research code in theano. It's a hierarchical LSTM network. LSTMs can be trained to generate sequences. Sequences of whatever. Could be text. Could be weather. We train it on the raw acoustic waveforms of metal albums. As it listens, it tries to guess the next fraction of a millisecond. It plays this game millions of times over a few days. After training, we ask it to come up with its own music, similar to how a weather forecast machine can be asked to invent centuries of seemingly plausible weather patterns.

It hallucinates 10 hours of music this way. That's way too much. So we built another tool to explore and curate it. We find the bits we like and arrange them into an album for human consumption.

It's a challenge to train nets. There's all these hyperparameters to try. How big is it? What's the learning rate? How many tiers of the hierarchy? Which gradient descent optimizer? How does it sample from the distribution? If you get it wrong, it sounds like white noise, silence, or barely anything. It's like brewing beer. How much yeast? How much sugar? You set the parameters early on, and you don't know if it's going to taste good until way later.

We trained 100s of nets until we found good hyperparameters and we published it for the world to use.