4 ms·

Reminds me of https://en.wikiquote.org/wiki/Oil_drop_experiment https://en.wikiquote.org/wiki/Oil_drop_experiment, famously described by Feynman, > Millikan me

Reminds me of https://en.wikiquote.org/wiki/Oil_drop_experiment https://en.wikiquote.org/wiki/Oil_drop_experiment, famously described by Feynman, > Millikan measured the charge on an electron by an experiment with falling oil drops, and got an answer which we now know not to be quite right. It's a little bit off because he had the incorrect value for the viscosity of air. It's interesting to look at the history of measurements of the charge of an electron, after Millikan. If you plot them as a function of time, you find that one is a little bit bigger than Millikan's, and the next one's a little bit bigger than that, and the next one's a little bit bigger than that, until finally they settle down to a number which is higher.

m-watson 4y ago
That experiment is also used to teach about selective data exclusion (potential scientific fraud) as well as a resistance to challenging an already published value (future experiments searching to verify Millikan's value rather than show it was incorrect or off) in a lot of experimental classes. https://en.wikipedia.org/wiki/Oil_drop_experiment https://en.wikipedia.org/wiki/Oil_drop_experiment
hinkley 4y ago
Is that part of the genesis for these conversations about how perhaps the physical constants of the universe are slowly changing over time? If you look at the 'right' experiments, the speed of light slowly crept up over time too, IIRC. When the movement is all in one direction it's easy to speculate that maybe that's because the target keeps moving.
- hither_shores 4y ago
  No, any possible variation in fundamental "constants" is going to be far slower. The fine-structure constant (which is generally what's actually being discussed when people talk about a variable speed of light), for instance, changes by no more than a factor of about 10^-17 per year.
  - hinkley 4y ago
    Did we know that 70 years ago? I’m talking about history, not today.
    - hither_shores 4y ago
      That particular bound wasn't. Others were. For example: Millikan's value for the electron charge was about .995 of the current best measurements. That was about a century ago. So either someone was wrong, the average rate of change has dramatically increased recently (in which case the universe is conspiring against physicists and all bets are off), or human biochemistry is significantly younger than human civilization.
antognini 4y ago
Another example I recently came across was the early measurements of the AU using radar. The first two experiments tried to bounce radar off of Venus had very noisy data, but they seemed to have a detection that implied a distance that was pretty close to the earlier measurements that had been done using parallax. But after the equipment was upgraded, the detections went away and it turned out that they had just been noise. Later on an even more powerful radar system was able to successfully bounce a radar signal off of Venus and it turned out that the AU was quite a bit different from its earlier value.

m-watson 4y ago

That experiment is also used to teach about selective data exclusion (potential scientific fraud) as well as a resistance to challenging an already published value (future experiments searching to verify Millikan's value rather than show it was incorrect or off) in a lot of experimental classes. https://en.wikipedia.org/wiki/Oil_drop_experiment https://en.wikipedia.org/wiki/Oil_drop_experiment

hinkley 4y ago

Is that part of the genesis for these conversations about how perhaps the physical constants of the universe are slowly changing over time? If you look at the 'right' experiments, the speed of light slowly crept up over time too, IIRC. When the movement is all in one direction it's easy to speculate that maybe that's because the target keeps moving.

hither_shores 4y ago
No, any possible variation in fundamental "constants" is going to be far slower. The fine-structure constant (which is generally what's actually being discussed when people talk about a variable speed of light), for instance, changes by no more than a factor of about 10^-17 per year.
- hinkley 4y ago
  Did we know that 70 years ago? I’m talking about history, not today.
  - hither_shores 4y ago
    That particular bound wasn't. Others were. For example: Millikan's value for the electron charge was about .995 of the current best measurements. That was about a century ago. So either someone was wrong, the average rate of change has dramatically increased recently (in which case the universe is conspiring against physicists and all bets are off), or human biochemistry is significantly younger than human civilization.

antognini 4y ago

Another example I recently came across was the early measurements of the AU using radar. The first two experiments tried to bounce radar off of Venus had very noisy data, but they seemed to have a detection that implied a distance that was pretty close to the earlier measurements that had been done using parallax. But after the equipment was upgraded, the detections went away and it turned out that they had just been noise. Later on an even more powerful radar system was able to successfully bounce a radar signal off of Venus and it turned out that the AU was quite a bit different from its earlier value.