Category Archives: Video
Time Travel
A nit: if “strength of gravity” means the value of g, then it’s incorrect. The amount of dilation is due to the depth in your gravitational well (the gravitational potential), which is important if you compare two planets with each other. Since the force varies as 1/r^2 and the potential as 1/r, it’s possible to contrive a planet whose mass and size are such that gravity (g) is weaker, but you are “deeper in the well” and your clock runs slower (or the opposite). If you are talking about a single planet then the distinction doesn’t matter, but the details do. You don’t want to misapply the model because of a vague description such as this.
At the end he tells us that 24k miles will slow you be about 5 nanoseconds, but you may already have known that.
I Am Impressed
… and perhaps McKayla Maroney would be, too.
Three videos on the high bar, and one with a floor exercise move.
Splish Splash
Humble drops of water levitate their way to stardom
First the researchers increase the strength of the field, which flattens the floating drops into discs. They then turn the drops into stars by tuning the field to the resonant frequency of the drops – or exact multiples of that frequency. Using a particular multiple produces a star with the corresponding number of spikes.
Darth Says to Take Lorraine to the Dance
Three Illusions That Will Destroy Your Brain
[W]atch this, and if it doesn’t melt your brain, I can no longer help you.
More Fun with Lenz's Law
I’ve linked to videos showing the effect before, but it’s still cool. I notice he spins the magnet — that gives an even faster change to the magnetic field, and enhances the braking beyond what simply dropping it would do. I looked at the effect with a coil, by measuring the induced voltage some time back.
A Wildcat on the Streets …
De-Mag-Ni-Tize! De-Mag-Ni-Tize!
(I’m picturing a dalek-like voice saying this, instead of ex-term-in-ate!)
Mechanical shock also tends to lessen the magnetization of a ferromagnet, and you can also scramble it with a strong oscillating external field. That will at least wound it, if not not kill it.
Captcha
This is pretty cool.
J002E3 is a object that was discovered in Earth orbit in 2002. It was initially thought to be an asteroid, but turns out that it was probably the S-IVB third stage of Apollo 12.
It was off in a heliocentric orbit for 31 years, made a brief 6-orbit visit home, and now it’s off galavanting around the sun again. May get captured temporarily again in 2040
It looks like “chasing the moon” on the last orbit is what gets it kicked out of earth orbit.
Sane Clown Posse Time
Vertiasium and Minute Physics team up to explain magnets.
I was worried for a minute they were going to leave it at “magnets behave that way because electrons behave like tiny magnets” which only moves the goalposts, but there’s a nice reality check there, and it’s good even though they don’t delve too much into the quantum — they gloss over that it’s related to spin, and also lean a little on the Bohr description of the orbital motion. (IOW, it’s not that the orbital motion cancels, per se, it’s that there are no classical trajectories to begin with.
I saw this at It’s Okay to be Smart, and in a followup I think that Joe is right when he claims that when Feynman says (in the last video in the link) he can’t explain magnets, he’s not actually saying he can’t explain what the videos covered — he actually does (briefly) mention the answer. He’s explaining why “why” questions are difficult in physics — we always hit that point (mentioned in the video above) where you have to say “No-one knows. That’s just the way the universe works”.