Category Archives: Physics
Only 5? You Just Made the List, Buddy.
5 Atrocious Science Clichés to Throw Down a Black Hole
After careful consideration and consultation with members of the local science writing community (only some of them were drunk), we have selected the five most annoying and ubiquitous clichés we think should be sucked into a black hole, forever banished from all future descriptions of science.
Funny — I just saw “shedding light” in several headlines on my RSS feed before getting to this, and “shedding light on black holes” (ouch!) got me ~41k Google hits.
I’m surprised “quantum leap’ isn’t on the list. Quantum means discrete, not big, i.e. the opposite of quantum is continuum.
I’d also add “all heat and no light” because visible light from a blackbody is heat, and it can certainly be used to warm things up. Radiant energy is radiant energy. The problem here is that out experience is with “hot” things is at around 400K or so, where most of the blackbody radiation is in the infrared. So we equate infrared radiation with heat, and they just aren’t synonymous. You can be burned with focused visible light (ask an ant if you don’t believe me — oh, wait, you can’t: they’ve all been burned up). A microwave oven is another example of radiant energy transfer which doesn’t involve the infrared as the source.
Doctor Obvious, Come Here … Slowly
Higher Speed Limits Cost Lives, Researchers Find
“This is a failed policy because it was, in essence, an experiment over 10 years. People assumed that increasing the speed limit would not have an impact,” said Friedman. “We’ve shown that something has happened and it’s quite dramatic.”
Umm, really? People assumed that if you drive faster, with its associated reduction in response times and increase in collision energy, that there would be no effect? I think people wanted the higher speed limit despite the higher risk it entailed, in part because of other safety advances.
Friedman uses the example of the 3,000 people who died in the September 11th terrorist attacks.
“That tragic event has led to a whole foreign policy,” he said. “We estimate that approximately 12,500 people died as a result of a policy to deregulate speed enforcement — four times what happened on September 11th — and yet changing the policy to reduce speed limits may be very difficult.”
What they don’t say is that despite the extra ~1250 deaths per year from the higher speed, overall deaths have fallen, and the rate per vehicle-mile has dropped dramatically over the years. Per mile traveled, you’re about half as likely to die as compared to 1980.
The problem with simply presenting a number is that there is no basis for a valid comparison. The apples-to-oranges 9/11 fatalities number is given instead. The graph shows about 15,000 fatalities per year, currently, making this a 9% increase, which discounts the possibility of other influences such as more cars on the road and more miles being traveled, which the fatality rate statistic indicates. (Though that can be influenced by many things as well)
A more meaningful analysis might go something like this. My upcoming vacation will entail me driving perhaps 1,000 miles. I can drive slower if I choose, but I have to consider if saving a half-hour of travel is worth it. Since being on the road for ~8 hours means fatigue comes into play, it might actually be safer to cut down on the travel time. If the fatality rate is 2 per 100 million miles, this means a statistical chance of 0.002%, which is quite small. And we’re talking about increasing this by 10%, to 0.0022%. The sin-by-omission in the article has you focusing on the dramatic large number rather than the overall picture.
Masquerade
It’s a chemistry site, but this is all physics
One For the Hotshot
Uncertain Principles: Pop Quiz: Michelson Interferometer
When there’s no light on the viewing screen, we have light going into the interferometer, but no light coming out. What happened to the light?
It’s important to note a clarification Chad gives in the comments
To clarify (or maybe confuse) things a bit: this is a hypothetical idealized Michelson interferometer in which the beams have zero divergence. Thus, you don’t get a ring pattern, just a single spot of light.
Until reading that I wasn’t liking any of the answers.
Though I didn’t comment, I did choose the right answer.
Continue reading
Found at a Yard Sale?
Someone asks, What is it?
I surmise this was found at Freddy Roentgen’s yard sale, selling his grandfather’s dusty lab equipment. It’s an x-ray tube — boil off electrons, accelerate them and have them slam into the copper target, where they emit bremsstrahlung and also ionize the target, which will give some x-rays during the recombination if it involves inner-shell electrons. It’s unshielded, so it’s probably pretty old and/or taken out of a shielded device. I’d imagine a newer device to be more compact and with more recognizable connectors.
No Talkies, Yet
Here you’ll find animated illustrations that explain the inner workings of a variety of steam, Stirling, and internal combustion engines.
In this Corner …
… weighing in at nil, the aether!
Skulls in the Stars: Lord Rayleigh vs. the Aether! (1902)
One of the most fascinating aspects of 19th century physics is that many remarkable ideas and ingenious experiments were motivated by a physical hypothesis which we now know to be incorrect: namely, the aether. When light was demonstrated to have wavelike properties in the early 1800s, it was natural to reason that, like other types of waves, light must result from the excitation of some medium: after all, water waves arise from the oscillations of water, sound waves arise from the oscillation of air, and string vibrations are of course the oscillations of string. The hypothetical medium which carries light vibrations was dubbed the “aether”, due to its unknown, “aetherial” nature.
Forget the Hearse 'Cause I Never Die
Dot Physics: A demo for the color black
What do you see when you are in a completely dark room with no lights?