## How Quantum Entanglement Works – For Dummies

5. December, 2022

So you’ve heard about this “quantum entanglement” stuff and how Einstein was apparently worried it might break the speed of light.

It doesn’t and he wasn’t.

Here is the simple version: Take a piece of paper. Rip it apart once. Check the pieces that you got. Maybe scribble something on it. Mix the two pieces behind your back. Give one of them to a friend without looking. Send the friend to the end of the universe. If he refuses, find a real friend. Wait a few billion years. Open your hand. In that instant, no matter how far away your friend is, you will know what piece he has in his hands.

The complicated version: Quantum is weird but some stuff is actually easy to understand. There are just a few ways to create entangled particles. All of them have something in common: The pieces must add up exactly to what you put in. This isn’t magic or some badly written Star *beep* episode. Imagine you put in a piece of paper (or a photon – a blip of light). You can’t have more paper (or more light) after splitting it. In the case of the photon: If you add energy, you get more light but no entanglement.

So the entangled photon pairs are always half of the original in terms of energy (which roughly translates to “half as bright”). And they always go in exactly opposite directions (see conservation of momentum). Things like that. Which means you know everything about the two particles except one thing: You don’t know which is which unless you look.

If you keep one of them around and sent the other away, and then at some later point look at what you kept, you know exactly and instantly what the other must look like, no matter how far away it is now.

But you can’t change the far particle anymore. Same as you can’t add text to the paper which your friend at the edge of the universe is holding. So you can’t use this to beam information.

Sorry.

Be grateful for having friends like that. A pity that you sent him away.

## Dark Forest is a Fairy Tale

16. December, 2021

The Dark Forest, an idea developed by Liu Cixin for his Remembrance of Earth’s Past series (also known for the first book “The Three-Body Problem” is just a fairy tale: Interesting to think about, there is a morale but it’s not based on reality.

Proof: We are still here.

The Dark Forest fairy tale is a solution to the Fermi paradox: If there are billions of planets like earth out there, where is everyone? The Dark Forest claims that every civilization that is foolish enough to expose itself gets gets wiped out.

Fact: We have exposed ourselves for millions of years now. Out planet has sent signals “lots of biological life here” for about 500 million years to anyone who cares.

Assuming that the Milky Way has a size of 100’000 light years, this means every civilization out there know about Earth for at least 499.9 million years. If they were out to kill us, we would be long gone by now. Why wait until we can send rockets to space if they are so afraid of any competition?

How would they know about us? We can already detect planets in other star systems (the current count at the writing of this article is 4604, see http://www.openexoplanetcatalogue.com/). In a few years, we’ll be able to tell all the planets close to us which can carry life, for values of close around 100 light years. A decade later, I expect that to work for any star system 1’000 light years around us. In a 100 years, I’ll expect scientists to come up with a trick to scan every star in our galaxy. An easy (if slow) way would be to send probes up and down out of the disk to get a better overview. Conclusion: We know a way to see every star system in the galaxy today. It’s only going to get better.

Some people worry that the technical signals we send could trigger an attack but those signals get lost in the background noise fairly quickly (much less that 100 light years). This is not the case for the most prominent signal: The amount of oxygen in Earth’s atmosphere. If you’re close to the plane of the ecliptic (i.e. when you look at the sun, the Earth will pass between you and the sun), you can see the Oxygen line in the star’s spectrum for thousands of light years. Everyone else has to wait until Earth moves in front of some background object.

There is no useful way to hide this signal. We could burn the oxygen, making Earth inhospitable. Or we could cover the planet with a rock layer; also not great unless you can live from a rock and salt water diet.

For an economical argument: When Ruanda invaded the Democratic Republic of Congo to get control of Coltan mining, they made roughtly \$240 million/yr from selling the ore. China makes that much money by selling smart phones and electronics to other states every day (source: Home Deus by Yuval Harari). My take: killing other civilizations is a form of economical suicide.

Conclusion: The Dark Forest is an interesting thought experiment. As a solution for the Fermi paradox, I find it implausible.

## Is Climate Change Just A Lot Of Hot Air?

26. June, 2015

A thought-provoking video by MinuteEarth:

## The End is Nigh, Part 2

16. June, 2013

A while ago, I asked whether wars on water, burning fossil fuel or air conditioning will kill us first.

Turns out it’s probably air conditioning.

Currently, we’re facing a couple of problems. We’re polluting the oceans with plastics, stressing many strands of the food chain and fish much more than we should. Sounds bad but we’ll run out of oil for plastics before we can poison everything and fishing fleets will quickly disappear with their prey – along with a few million people. So that sucks but it’s not a big problem in the sense that it’ll kill us – it will most likely resolve itself by becoming uneconomical.

Same goes for burning fossil fuels. We have a lot of them but the amount is finite and we’ll eventually run out of them. In a few years, the effect on the environment will put a lot of strain on the global economy. We’ll lose ships and planes in storms or they can’t even leave port. But again, as soon as this happens, the supply of fossil fuels will dry up since the platforms to make them available won’t be able to survive the weather we created.

Water? There will be wars over water but they will be pretty local. Israel, for example, will have to build many desalinating plants. And terrorists will love to blow them up. But water is on the radar since everyone involved is aware that access to water is so important.

AC is going to kill us? I must be kidding, right?

No.

First of all, no one believes that air conditioning is a problem. But think about it:

1. Asia is mostly tropical. People are getting more rich and demand better living conditions.
2. AC need a lot of electricity which comes from mostly from fossil fuel
3. The coolants will heat up the planet much more efficiently than any other gas we produce as soon as it leaks and it will – most people in Asia know the concept of recycling but they dump their broken stuff in the forest just like we did a few years ago.
4. Staying cool is essential to be productive and to be able to concentrate. It’s not (only) a luxury.

## Demons? Really? Really! But not as you think

23. February, 2010

I just read Linus Torvalds’ post “Demons? Really?” Which is about exorcism in case you don’t want to read his piece. Apparently, there are people who believe that you can drive a demon with prayers from a human body. Which is complete nonsense according to Linus.

Really?

What are we talking about here? What is a demon? I’m not sure what the scientific definition would be but I’m pretty sure that the people discussing the topic don’t know either. They don’t care. For them, the demon is not important but to help the possessed.

From our scientific eye, talking about demons and exorcism is ridiculous. We assume that a demon is probably some kind of sickness and the poor victim would be better off in a hospital or psychiatric care. They are just sick. Just imagine when you are in pain. It affects your mood: You become thin-skinned and easily irritated. So the sickness has a mental component.

Treating the sickness would solve the mental issues. So we’re happy and the missionaries must be stupid. Or so we think.

Question: Have you ever been in this situation? In a village thousands of miles away from anywhere? Without clear water, healthy food, and people with a yearly income in the range of \$5 or less? Good luck finding medicine for them or sending them to a doctor. They either have no access to such resources or can’t afford it.

What do you do? Walk away, happy with the fact that you know what would help? Or do you stay and try to help to the best of your abilities?

If you stay, what can you do? You have no medicine, you’re no doctor and you probably have no idea what is really going on. There are people around, probably from the same village who think “I don’t know what he has but I don’t want it! Let’s get rid of him before we all get sick!” These people still have to learn that modern science exists. They couldn’t care less because for them, the biggest issue is how to get enough food to survive another week. National Geographics? FDA? These are all non-issues for these people.

For them, the sick are possessed because that is something they can relate to. It explains the unknown. Demons can be shooed away.

So what do you do? Stick to your scientific knowledge? Or do you start to pray to drive the demon out? Showing compassion, doing what is expected from you, possibly triggering the self-healing effects of a placebo? Doing what you can in such a situation?

Yes, we can mock these people because they probably believe that demons really exist. But maybe they have understood hundreds of years ago that science can only help the rich. People who have (almost) unbound access to good water, food and electricity.

Maybe for them, it’s more important to help than to be right.

## 10 Ways to be a Better Thinker

20. August, 2009

There is an article on CNN about ten ways to be more happy with your brain.