History of Science

I’ve been learning about the History of Science courtesy of Crash Course. It’s really interesting.

I first found out that the history of science was fascinating from Connections by James Burke. This was a PBS series back in the day (the late 1970s) (and it’s not really PBS, since it came across the pond from the BBC), and each one traced a series of scientific and technological discoveries from ancient to modern times. The first episode traced the invention of the plough to modern power blackouts. While the show looks dated (hey, it’s over 40 years old!), if you can get past that, it really rewards viewing. You can watch it on YouTube here.

Anyway, the YouTube playlist for the Crash Course History of Science is 46 episodes long, so I have some watching ahead of me.

#crashcourse

Terminal Velocity

Today I went skydiving with my son! First time for both of us. Until you’ve done lots of dives you have to go in tandem with an experienced skydiver. So we went to the Sussex Skydiving, and checked in. We each got hooked into one half of a tandem rig. Then we went up in the airplane to 14,000 feet (along with our instructors and the other people jumping). At that altitude the plane leveled off and pairs started jumping out.

First the instructor attaches you to their suit (the other half of the tandem rig). He tightens the straps so you’re up nice and snug, as one unit. Then we moved together to the open door, and I put my feet out. My instructor then pushed us out of the plane.

The first few seconds were somewhat disorienting, but I quickly got my bearings and started hooting and hollering. Of course, now that we were falling up to 120 mph the wind was so loud I couldn’t hear anything!

So the title of the post refers to the maximum downward velocity, in this case 120 mph. At this speed the downward pull of gravity is canceled out by the drag of falling through the air, so this is the fastest we went going down. We had about 60 seconds of free fall. Now, it turns out that in tandem jumping the instructor uses a drogue chute to stabilize the two of you. This means our drag was higher than without it, so our terminal velocity was lower. Also, two people falling in a tandem rig would have more weight for the amount of surface area, and their terminal velocity (without the drogue) would be higher. So I don’t really know what a single person’s terminal velocity would be.

Then the instructor pulled the chute and we slowed down. The chute provided much more drag, so our terminal velocity was less. Finally we landed back at the airport. For this the instructor had us dive, then level out just above the ground. We stuck our feet out in front, and hit the ground. Our forward and downward momentum was very low and we skidded for a few feet before stopping.

So Rileysci, how was it?

It was very exciting! Certainly more thrilling than large roller coasters. But I’m kind of old, and I had issues. Isome ear pain when going up in the airplane. Surprisingly, I didn’t notice any pain on the way down, but my body was overwhelmed with other things at the time and didn’t notice. While going down with the chute open I was kind of dizzy, probably from my nervous system being overwhelmed. It’s taken a while for my body to get back to equilibrium (yay homeostasis!). Overall it was something to check off my bucket list, but I won’t do this again.

My son enjoyed it much more and will definitely be doing this again before the summer ends.

#sussexskydiving

No detectable alien civilizations at 60 million stars

Breakthrough Listen has been looking (listening?) for alien life in our milky way galaxy and at the 100 nearest galaxies. They’ve been specifically listening in areas of our galaxy where the stars are more closely packed: the galactic core. They examined over 60 million stars, but haven’t found anything significant.

My hypothesis

I think that we’re unlikely to find signals from alien civilizations because I think we’re looking for the wrong things. I look at it this way: we’ve been looking for the kind of signals that we put out. Stuff like radio waves. That makes sense given our history; we’ve been dumping radio waves for over 100 years. But that presumes that aliens would similarly be putting out organized electromagnetic radiation. What if the hypothetical aliens have come up with a more efficient way to send information to themselves. What if they’ve stopped using radio, etc.

Perhaps they’ve shifted to using tightbeam laser communication. That wouldn’t be sending signals all over the place, just to the destination. It’s also more energy efficient.

It’s like using listening for AM radio signals, but the people you’re listening for have switched to FM. The way of encoding information is different, and could just appear as random static.

If intelligent life out there is using some method to communicate that we haven’t thought of, then we may not be able to detect them, even if we’ve scanned their system for signals.

Of course I don’t have a solution to this problem. I know much less than the experts on what other methods intelligent life could be using to communicate; I’m just a middle school science teacher. I’d love to find evidence of alien intelligence. I just think that we’re looking for a needle in a haystack where no one is allowed to access the haystack directly.

I think that we may find extra-terrestrial life, but it won’t be intelligent life. It’ll be something like bacteria. Perhaps life is relatively common, but it doesn’t evolve to what we think of as intelligence. How would we know if there were a habitable planet within 50 light years that has life with the intelligence chimpanzees? They wouldn’t be broadcasting anything.

COVID-19 herd immunity? Not so fast.

Herd immunity (or community immunity if you like rhymes) is the point when enough of the population has been immunizes so that a disease can’t spread much. Maybe only a few people get sick, but outbreaks are stopped because there just aren’t enough vulnerable people around for the disease to spread.

And boy, would we just love to get to that point with COVID-19. But at least in the USA it doesn’t look like we’ll get there. Why? Because you need enough of the population immunized. Something around 80% is needed(it varies depending on each disease’s R number). But with about 25% of the population here refusing to get immunized, we may never reach it.

Anthony Fauci isn’t talking about getting there anymore. He’s shifted to trying to get as many people immunized as possible. Others are more explicit:

“It’s theoretically possible but we as a society have rejected that,” said Dr. Gregory Poland, director of the Mayo Clinic’s Vaccine Research Group. “There is no eradication at this point, it’s off the table. The only thing we can talk about is control.”

— Dr. Gregory Poland from an article in USA Today

Control. Not the nice kind where we’ve beaten the disease. The kind where we have to be careful for a long time. These anti-vaxers are just making things worse. It’s called a conspiracy theory for a reason: it’s like circular reasoning and non-falsifiability. i.e. not science, and not trustworthy. It’s like these people are afraid of critical thinking.

Sigh.

Let’s just hope we get there in spite of them. Maybe some parts of the US will get herd immunity while others just won’t have enough people who believe in science.

Fundamental Equations, Chaos, Fractals, and Leaky Faucets

It’s been a while since I’ve written here. Busy teaching. (I know, lame excuse).

So I go and watch some video on YouTube, and on the side is the list of suggested videos. For a while there’s been this one by Veritasium (Derek Muller). Now, Derek is a fantastic science educator, and is who I want to be when I grow up. One problem is he’s younger than me by over a decade. Hmm. Have to work on that somehow.

Anyway, the video that was just waiting for me to finally click on it was this one. It’s about an equation that will change how you see the world.

The Logistic Map

The math is very simple: x_{n+1}=r x_n(1-x_n) where r is the growth rate. This is a very simple equation with a negative feedback loop.

When you graph r by the equilibrium population, you get this:

from the Wikipedia article on the Logistic Map

What!?

Once the growth rate hits 3, the equilibrium population splits, and oscillates between two values. Then just after 3.4 it splits again. And very soon it becomes chaotic. Oh, and fractal. The chaotic nature was used for pseudorandom number generators.

The Mandelbrot set

Does mentioning fractals make you think of the Mandelbrot set? If it doesn’t, then you have some research to do.

From the Wikipedia article on the Mandelbrot Set

It’s probably the most famous fractal out there. Heck Johnathan Coulton has done a song about it.

But evidently if you somehow rotate the Mandelbrot Set along it’s real number axis, you get this:

From Physics Forum

Look familiar? At this point I started getting a headache, but it was one of those good, excited headaches that come from having your reality twisted about.

Leaky Faucets

Oh yeah, leaks. Derek then mentions that if you get your faucet going drip, drip, drip, and then increase the water pressure just right, it will start doubling: drip drip, drip drip, drip drip. Push it a little more, and you get chaotic behavior.

Of course the YouTube video is so much better than my explanation. Go watch it.

Are you Mind Blind?

How well do you visualize things you remember or imagine? Try to imagine this: You have climbed to the top of a hill. You scramble to the top of some rocks. Ahead of you, past some more hills with trees on them, is a mountain range rising above the hills. The sky is mostly blue with a few fluffy clouds, and a plane going by leaving a contrail.

How well did you visualize that? Could you see it in your mind’s eye? Or was it just a description without an image?

If you couldn’t visualize it, then you may have aphantasia, a condition that 2-5 percent of people may have. This can affect how well we can recall things, to how we can imagine the future, and even dream.

See links for more information:

  1. Being ‘mind-blind’ may make remembering, dreaming and imagining harder, study finds
  2. A cognitive profile of multi-sensory imagery, memory and dreaming in aphantasia

Happy Summer Solstice

How would you like to watch the summer solstice sunrise or sunset at Stonehenge?

The solstices are the two days when the sun is the furthest north or south from the celestial equator. The full path that the sun takes over the year is the analemma. The solstices are the furthest north and south points on the analemma.

Stonehenge is one of the most well known monuments. The ring of standing stones was built between 3000 BCE and 2000 BCE. This English Heritage website is doing/has done livestreams of sunrise and sunset from the site.

What’s up with all these models?

Here we are, in the middle of dealing with COVID-19. We’re stuck at home, trying our best to deal with a bad situation. We naturally want to know when things will go back to some semblance of normal.

To do this, we need models. In science, a model is a way to make some part of the world easier to understand. In this case, how dangerous COVID-19 is. We hear about esoteric things like R0 (R-naught), which is how many people an infected person infects. But that’s hard to figure out. So we predict what the things that make up R0 are. That means that different people/organizations come up with different values of R0. The same things go into trying to determine how deadly this blasted disease is. Just what goes into making these predictions anyway?

Well, the author of the webcomic Saturday Morning Breakfast Cereal has a really good explanation of what scientists are dealing with trying to come up with a good model. You can read it over here. It gets into the nitty-gritty of what is going into the models for COVID-19. As such, it is pretty technical. But worth reading if you want to know more about why R0 seems to be different in the US than in Italy.

Visualize distancing with avatars

Right now, with COVID-19 wreaking havoc on our communities, it is important to be physically distancing ourselves from others. This is hard to do. Humans are social animals, and we crave contact with others.

Here’s a site that uses avatars that you customize that will help explain why distancing is important, and why we need to keep doing it until we have a way to get immunity.

And here’s a video I made on why it is imporant to keep distancing ourselves.