• Content Count

  • Joined

  • Last visited

  • Days Won


Everything posted by swansont

  1. It's really not a question of either.
  2. That's not technically the photoelectric effect - you need to absorb a photon and ionize the atom for that. What you are describing is excitation and de-excitation.
  3. Science or scientists? That religion can be flexible is why it isn't scientific. It can explain anything, even two mutually exclusive points. There is no way to disprove it, in principle, so it is unscientific.
  4. There were the invisible pink fairies... "I can explain just about everything with invisible pink fairies, and you can't disprove their existence. But it's useless as a theory, as there is no predictive power, and nothing that is explained that isn't already. (feel free to substitute the deity of your choice into that)" (me)
  5. No, really, they aren't. Creationism is in no way a valid theory. It can't be a theory because it's not science - it's religion masquerading as science. But a wolf in sheep's clothing is still a wolf.
  6. swansont

    GPS and SRT

    To do the proper SR calculation, though, you have to compare to an observer at rest. Even though we want to think of ourselves as being in an inertial frame, we are not. Our reference clocks are referenced to be on the geoid - the idealized average sea-level. The earth is an oblate spheroid - there is an equitorial bulge and flattening at the poles - and one must also account for gravitational redshifts. If you solve for the equipotential surface of the geoid, you find that the kinetic term (time dilation) cancels the deformation term (gravitational redshift) so that a clock on the geoid always runs at the same rate, regardless of rotation speed. The rotational velocity is not "disregarded." GPS satellites are in inclined orbits at about 55 degrees, not equatorial orbits, so your relative velocity calculation is flawed anyway, as velocity is a vector.
  7. Nothing would go faster than 10 m/s.
  8. It depends on the frequencies the material can absorb. Individual atoms have very distinct absorption bands, and when atoms form molecules and molecules form solids you have many different states, with ranges of frequencies, that can be absorbed. But there are still frequencies that cannot be absorbed, or the probability is much smaller. These colors are reflected, while the others are absorbed.
  9. c is constant, which is the speed of light in a vacuum. The propagation speed of light through a medium is c/n, where n is the index of refraction.
  10. If you have an object undergoing a constant acceleration, then the v vs t curve will be continuous and pass through zero. Unless you have infinite acceleration I don't think you can get away from having a point with zero velocity.
  11. I have had trouble with an optical mouse on light-colored surfaces. One is my desk, which is very light wood laminate, and the other was a white filing cabinet.
  12. First of all you must realize that skin is a poor thermometer. It is a much better measure of heat transfer, which is why a piece of metal feels colder than a piece of wood at the same temperature (below body temperature) - the metal conducts heat better away from your skin. There are three types of heat transfer - conduction, convection and radiation. The sun radiates a lot of energy - more than a kW per square meter - and you feel that on your face inside the car. But there is little convection, since there is no wind, and minimal conduction, since air is a gas and doesn't have a large heat capacity. So what you feel is the radiation heat transfer, as the other forms have been reduced.
  13. Name the fixed point. Then explain why that's not arbitrarily defined, and why it matters. Timekeeping is generally done in the ECI, or earth-centered inertial frame, since that is most convenient for us. The rotation of the earth does not cause deviations, since the time dilation contribution from the motion is cancelled by the change in gravitational redshift that depends on the oblateness.
  14. g is an acceleration. In what units is it equal to 10?
  15. swansont

    Types of people

    What about Cameron Willingham? He was convicted in August 1992 of the arson murders of his three young children, and executed in February 2004. Is he a monster? Does your answer change if you find out that arson experts have called the evidence into question, saying there is no basis for thinking the fire was arson, and that he was convicted, in part, because he didn't show remorse or the kind of grief the jury was looking for? IOW, he was very likely innocent.
  16. My experience was different. That sounds more like High School. For me, in college it was almost all exam results. No graded HW - no professor had the time. For classes with labs, the lab reports counted for some, but there was no other gradeable work for science and math classes. In grad school there were graded problem sets, but not for the undergrads.