Random links #18

Written on 4 November 2019, 04:51pm

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The only thing that truly matters in public speaking is not confidence, stage presence, or smooth talking. It’s having something worth saying.

The Official TED Guide to Public Speaking via

Every winner begins as a loser but not every failure leads to success.  It turns out that trying again and again only works if you learn from your previous failures. The idea is to work smart, not hard.

Failure Found to be an “Essential Prerequisite” For Success

Would you notice? Some students were presented with an onscreen calculator that was programmed to give the wrong answers. Researchers found most participants raised few or no suspicions when presented with wrong answers, until the answers were quite wrong. 

Would you notice if your calculator was lying to you?

Fingerprinting happens when sites force your browser to hand over innocent-looking but largely unchanging technical information about your computer, such as the resolution of your screen, your operating system or the fonts you have installed. Combined, those details create a picture of your device as unique as the skin on your thumb.

What is fingerprinting? The online tracking you can’t avoid

Imagine a world where the global space race never ended. This “what if” take on history from Ronald D. Moore spotlights the lives of NASA astronauts—the heroes and rock stars of their time—and their families.

For all mankind
What if?…

Space movies scientific goofs

Written on 24 October 2019, 11:39am

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I recently watched a number of space movies. Apollo 11, Apollo 13 and First Man looked more like a documentary – following the real events that happened 50 years ago. But then I also watched (or re-watched in the first 3 cases) Gravity, The Martian, Interstellar and Ad Astra – where the directors left their imagination free. But how scientifically-accurate are these 4 movies? Here is some insight.

Warning – spoilers ahead. You have been warned!

Ad Astra (2019)

I should probably start by saying that I didn’t like Ad Astra. Partially because of the story (which I found silly), partially because the whole masculinity idea was ridiculous, but more importantly, because it was full of science goofs. I really liked the idea of the regular service to the Moon and beyond, but, as soon as Brad Pitt climbed into a firing rocket, the movie started to feel bad. And then it didn’t get any better.

So here is a non-exhaustive list of science goofs from Ad Astra:

  • Climbing up inside a rocket while the engines are running? Wow. Just wow.
  • Using a piece of metal to travel through Neptune’s rings? Sure, in Tom&Jerry, but in reality, the relative velocities would be so big that shooting with bullets would feel like a water pistol…
  • Using the blast from a nuclear explosion in space to thrust you back to Earth? There is no atmosphere in space, so a shock wave is out of question. The only thing that the explosion would create is debris.
  • How would the main character jump into a years-old trip knowing that the life support supply is limited? Either he planned to kill somebody or never thought about that. Neither of this fits the character.
  • Using a rotating radar to slingshot you through space? Sure. But with that extraordinary precision? Unlikely.

The guys behind Ad Astra simply don’t get how space works. Almost everything related to the space travel is wrong. There are scenes like the rocket hijacking one when people who know a bit of physics feel insulted. What’s even worse, there was no need for such inaccuracies:

There could have been solid science reasons to motivate nearly all of the film’s more far-fetched plot points.


Read more: imdb.com, USA Today

Gravity (2013)

Gravity is the kind of movie that grows on you. I didn’t really enjoy it first time I saw it, but after watching it again several years later, I liked the main idea of the movie: our fragility and helplessness in space. The director admitted from the beginning that “Gravity is not a documentary; it is a piece of fiction“. Consequently there are a number of space goofs as well:

  • The ISS and the Hubble space telescope are orbiting Earth at different altitudes (420km vs 560km). They are both in low-Earth orbit, but could never be so close to each other. The Chinese space station was not in space when the last space shuttle was retired from service.
  • The communication satellites are much, much higher: 22240 miles (geostationary orbit). So there was no way the debris of the communication satellites would have any impact on the Shuttle/Hubble telescope.
  • Communication with the world would continue through ground stations even if the communication satellites were off
  • The space walk is not so easy at it seems in the movie. You cannot simply put on your space suit and jump off to space. Decompression sickness is a real problem, as is the exhaustion. At the end of a space walk, the astronauts are exhausted and must gradually re-accommodate to breathing air (during the space walk they are breathing pure oxygen at lower pressure). Plus, in the movie, there is no sign that the astronauts were wearing any thermal / cooling / ventilation system, nor a space diaper. Just some sexy panties 🙂
  • Finally, the thing with the fire extinguisher: in theory, it’s doable. But in practice, you are much more likely to go into a spin, unless you manage to point the jet really close to your center of gravity.
  • As in ‘Ad Astra’, the mechanics of moving in space are not very accurate:

It is hard for most people to understand the difficulty in being in orbit trying to reach another object in orbit. Accelerating an object in the direction of travel will actually not move you forward. Instead the energy is used up raising the object’s altitude, where it will have a slower orbital speed and therefore actually move “backwards” in orbit.


Overall, Gravity manages to give a good idea on the look and feel of the space. The science goofs rarely distract you from watching the movie. And the message in the end is brilliant. The entire landing scene is like the evolution of life, in one shot.

Read more: nasa.gov, popsci.com, wikipedia.

The Martian (2015)

The movies does a really good job in following the story from the novel of Andy Weir. This means that it also inherits the artistic licenses from the book. The science goofs are small and far apart, here is the list:

  • Due to the low atmospheric pressure on Mars, the wind would not be strong enough to tip a space ship. Plus, how come the second ship (Ares IV) can wait on Mars for years without any stability problem?
  • Figuring out an emergency escape route from Mars would be trivial for NASA and would not require a space nerd to figure it out. Also, using the Ares IV would be the obvious solution to get out of Mars
  • The Ironman scene has the same problems with the fire extinguisher scene from Gravity. See above.
  • Getting in and out of the space suit would not be so trivial. There are different pressures in the space suit compared to the hab. Stepping into the space suit and going out of the hab would require similar preparations as for a space walk, just as in Gravity:

Dropping from 14 PSI to 4.7 PSI pressure requires a progressive decompression sequence each time, which takes over two hours by the NASA protocol. The astronaut must pre-breathe pure oxygen to purge nitrogen from the body for this time, plus a period of “vigorous exercise” at the start of each pre-breathing and decompression sequence. Without this, the astronaut will get “the bends” due to nitrogen in the body tissues forming bubbles.


Once you accept the idea that people have a small base on Mars, things go smoothly from a scientific point of view. Brilliant movie; I highly recommend reading the book before watching the movie.

Read more: The Guardian, MovieMistakes.com

Interstellar (2014)

I might be subjective on this, because it’s one of my favorite movies. Or because the film director hired a scientific consultant who later on wrote a book and then won a Nobel price in physics for the detection of the gravitational waves. Or the fact that you need a degree in astrophysics to understand the science goofs of Interstellar:

No one can survive the g-force necessary to produce 7 years of time dilation per hour.

— https://www.imdb.com/title/tt0816692/goofs

What’s amazing for me is how Nolan manages to mix scientific facts with a great story. He even gets the time travel right; I cannot recall any other movie where the time relativity is presented in a better way.

Theoretical physicist Michio Kaku praised the film for its scientific accuracy and has said Interstellar “could set the gold standard for science fiction movies for years to come.” 

— Wikipedia
2014: A black hole as described in ‘The science of Interstellar’ book
2019: NASA Visualization of a Black Hole’s Warped World

Random links #17

Written on 7 October 2019, 02:49pm

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Electric planes

Air travel is bad for the planet—and travelers may finally be getting the message.
The change in mindset is due to increasing awareness of the issue thanks to attention-grabbing protests, like when activist group Extinction Rebellion shut down Heathrow Airport and climate warrior Greta Thunberg sailed across the Atlantic in a zero-emissions yacht to speak at the UN’s climate summit.

Does flight shaming work?

Solution? Hybrid or full electric planes. Also tested by NASA.

Heavyside, from Kitty Hawk is really silent and has a range of about 100 miles

Radiation in space is a big deal

If we want to prepare astronauts to fly to Mars, then we have a lot of problems to solve when it comes to health and well being. There are both psychological (isolation, confinement, sleep disturbance, etc) but also physiological (micro-gravity long time effects, radiation) factors to overcome. One of the most important is the radiation.

Radiation on Earth is about 4.6 mSv/year. On the Moon – 300/400x. On Mars – 1000x.

How can we reduce the radiation impact? Medical selection of the most resistant individuals, shielding (the ISS has 3 highly shielded areas) and medication. Hibernation is also an option, not explored yet.

Radiation sensitivity decreases with age. A teenager is 2 times more sensitive than a 30-years old adult, which is in turn 2 times more sensitive than a 50-years old.

Space travel affects the astronauts’ immune system. Various factors play a part in this process, i.e. weightlessness, cosmic radiation, isolation and the inevitable stress. At the request of European, American and Russian space agencies, SCK•CEN tests the blood of astronauts when they return from a long space mission. We perform analyses using advanced biochemical and molecular techniques.
Long-term exposure cannot be avoided during long distance missions, e.g. to Mars – for which the return flight takes 18 months. Sensitivity to cosmic radiation varies considerably between people, and consequently also between astronauts. 

The Belgian Nuclear Research Centre

Time matters

The Tesla dashcam writes its rolling clips in the /recent folder. The manually saved clips are stored in the /saved folder. Recently Tesla introduced the Sentry mode, which automatically saves events when the car is parked (ex. a person or a car is passing by).

The Tesla engineers thought that it’s appropriate to save these clips not in a dedicated folder (like /sentry), but in the same /saved folder where the manual clips are saved.

The outcome? When I want to look for a video that I manually saved, I have no easy way to find it. Sentry mode produces a huge number of videos, sometimes 10 videos for a half an hour spent in a busy parking. Finding the right folder among literally hundreds of other folders is like finding a needle in a haystack.

Compare this to the following bit:

One day Jobs complained to Larry Kenyon (the engineer of the Macintosh OS) that it was taking too long to boot up. Kenyon explained why reducing the boot-up time wasn’t possible, but Jobs cut him off: “If it would save a person’s life, could you find a way to shave 10 seconds off the boot time?”. He then showed on a whiteboard that if the Mac had five million users and it took 10 seconds extra to turn it on every day, that added up to 300 million or so hours a year — the equivalent of at least 100 lifetimes a year. After a few weeks, Kenyon had the machine booting up 28 seconds faster.

Steve Jobs Insane Productivity Secrets