So a helium atom walks into a communist party meeting, and they tell him he has to leave: “We don’t want any noble gases here.”
And the helium doesn’t react.
For the previous joke, click here.
Category Archives: Physics
Quantum physics joke
Q: How many quantum physicists does it take to change a blown lightbulb?
A: None: as soon as anyone notices the lightbulb it changes profoundly (the wave function collapses and the lightbulbs pops into existence –usually more-or -less where it was.)
For the previous joke, click here
Why is the galaxy stable?
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We are located about 30,000 light years out from the galactic center (1.8E17 miles), and the galaxy goes round every 200,000,000 years. From the rotational rate and diameter I calculate that we’re moving at roughly 1,000,000,000 miles/year or 100,000 mph — not a bad speed to expect to come from random variation of the gas molecule speeds. Maxwell averaging should reduce the speed to 2000 mph at most, I’d think.
Even more interesting, the rotation speed suggests the galaxy’s gone around about 50 times since it condensed. That’s an awful lot of turns for our galactic arms to retain stable; you’d expect that the outer parts of the arms would have rotated far fewer times, perhaps only once, while the inner parts would rotate perhaps 1000 times. After a billion years, you’d expect the arms to be gone. The going explanation is dark matter, matter we can’t see.
After bugging astrophysicists for a few years, I’ve come to believe that many of their models (MACHOs, WIMPs) don’t make much sense. I’ve come to model the distribution of dark matter on my own, as a particular distribution gas cloud of light particles. There is only one distribution that will result in the galaxy rotating as a unit — can you figure out what that is? Not that I now know what dark matter is, but at least I think I know where it is. Now all we need to do is find the missing matter. As a challenge, see if you can calculate the distribution of dark matter that would result in the galaxy rotating as a unit.
— Robert Buxbaum
The universe is not endless
You may have heard that the universe is not endless, ending at a brick wall, perhaps, some 15 billion light years out. But what you may not know is that there is a classic proof, going back to the middle ages to show that the universe is not an endless expanse of stars.
Consider an endless universe with a uniform distribution of stars. We would expect that, in any large-enough space of this universe there would have to be many stars, e.g. between 100 and 101 trillion miles from earth. At this distance, each of these stars is close enough to see, and the combination of them (the sum in this volumetric shell) will shed a small amount of heat on the earth. Now consider another shell, the same thickness but twice as far from us; if the universe is uniform, there will be 4 times as many stars, but since these stars will be at twice the distance; that is between 200 and 201 trillion miles from earth, each star will present us with ¼ as much heat as the stars in the first shell. Now, since there are 4 times more stars, the total effect is to radiate as much heat to us as from the first shell.
The same argument goes for each shell of 1 trillion miles thick: each one presents us with the same amount of heat. If the universe is infinite and uniform, we find there will be an infinite number of shells radiating this amount of heat, and therefore an infinite amount of heat bathing us. We should expect to roast from all of it. Since we have not roasted, we conclude that the universe is not an endless, uniform expanse.
The universe could still be uniform and not endless (ending with a brick wall, as in the Hitch-hikers guide), or it could be expanding from a big bang 15 Billion years ago. This latter is suggested by the red shift, but not a favored solution of creationists for some reason. Or it could be a closed, oscillating (or not) 4 dimensional hypersphere (Einstein). That is, it could be a non Euclidean, black hole. Or it could be fractal (Mandelbrot). Or it could be a combination of all of the above.
For a thought about galactic arms see here. October 22, 2012.
Why tornadoes and hurricanes lift up cars, cows, etc.
Here’s a video I made for my nieces and any other young adults on why it is that tornadoes and hurricanes lift stuff up. It’s all centrifugal forces — the same forces that generate the low pressure zone at the center of hurricanes. The explanation is from Albert Einstein, who goes on show why it is that rivers don’t run straight; before you read any more of it, I’d suggest you first watch the video here. It’s from my Facebook page, so it should be visible.
If can’t see, you may have to friend me on Facebook, but until then the video shows a glass coffee cup with some coffee grounds and water in it. Originally, the grounds are at the bottom of the cup showing that they are heavier than the water. When I swirl the water in the cup, you’ll see that the grounds are lifted up into a heap in the center with some flowing all around in a circle — to the top surface and then to the walls of the cup. This is the same path followed by light things (papers for example) in a tornado. Cows, houses and cars that are caught up in real tornadoes get sucked in and lifted up too, but they never get to the top to be thrown outward.
The explanation for the lifting is that the upper layers of liquid swirl faster than the lower layers. As a result there is a low pressure zone above the middle of the swirl. The water (or air) moves upward into this lower pressure area and drags along with it cows, cars, houses and the like (Here’s another post on the subject of where the swirl comes from). The reason the swirl is faster above the bottom of the cup is that the cup bottom adds drag to the flow (the very bottom isn’t swirling at all). The faster rotating, upper flows have a reasonable amount of centrifugal force and thus a lower pressure in the middle of the swirl, and a higher pressure further out. The non-rotating bottom has a more uniform pressure that’s relatively higher in the middle, and relatively lower on the outside. As a result there is a secondary flow where air moves down around the outside of the flow and up in the middle. You can see this secondary flow in the video by following the lighter grounds.
Robert. E. Buxbaum. Weather is not exactly climate, but in my opinion both are cyclic and chaotic. I find there is little evidence that we can stop climate change, and suspect there is no advantage to wanting the earth colder. There was a tornado drought in 2013, and a hurricane draught too. You may not have heard of either because it’s hard to report on the storms that didn’t happen.
Higgs Boson joke
A Higgs boson walks into a church, and they throw him out, saying: “There’s no room here for a particle that thinks it’s GOD.” But the Higgs boson comes back. “You can’t throw me out, you can’t have mass without me.”