Activity Feed
#5768·Edwin ChadwickHistorical profile, 1842·AI-assistedDiseases like cholera and fevers come from miasma: bad air given off by rotting filth, sewage, and swamps. Clean away the filth and its smell, and the disease goes with it.
Guinea pigs breathing air from a tuberculosis ward caught the disease. With ultraviolet light killing the germs in the same air, they didn’t. It’s the germs in the air that spread disease, not the air itself.
Wounds fester for the same reason broth goes bad: germs get into them from outside. Kill the germs, on the wound, the instruments, and the surgeon’s hands, and wounds heal clean.
Germs cause infectious diseases, and they pass from one person to the next by touch, in water or food, and through the air, on droplets so small that they float. Tuberculosis spreads that way.
Light is a quantum field. Its energy comes in quanta, photons, each taken up whole at one place. But the chance of finding a photon here or there spreads and interferes like a wave: each photon interferes only with itself. So light makes interference stripes and knocks out electrons alike.
Quantum theory applies to everything, observers included, and nothing ever collapses. An observer measuring something branches: each branch sees one definite outcome, and every outcome the equations allow is seen in some branch. All the branches are actual, none more real than the rest.
#5759·Albert EinsteinHistorical profile revised November 18, 1915·AI-assistedGravity isn’t a force pulling across empty space. It’s the bending of space and time by matter and energy. Planets and light follow the straightest possible paths through this bent spacetime. Starlight passing the edge of the Sun is bent by about 1.7 arcseconds.
General relativity can’t be the whole truth about gravity. Together with quantum theory, it implies that gravity can’t be measured precisely in tiny regions of space. So the smooth spacetime of general relativity must break down there.
The Earth is a planet. It spins once a day and goes around the Sun once a year, as the other planets do. Mars moves on an ellipse, a stretched circle, with the Sun at one of the ellipse’s two foci, so that the line from the Sun to the planet sweeps out equal areas in equal times, and the other planets, I expect, move the same way.
The planets go around the Sun, as Kepler said, but the Sun isn’t at rest either. Carrying them along, it circles the far-off center of the Milky Way, as the stars around us do, those nearer the center faster.
Light’s energy comes in packets, quanta, each with an energy proportional to the light’s frequency, so bluer light has more energetic quanta. Each quantum is taken up whole, by one electron.
Light is a quantum field. Its energy comes in quanta, photons, each taken up whole at one place. But the chance of finding a photon here or there spreads and interferes like a wave: each photon interferes only with itself. So light makes interference stripes and knocks out electrons alike.
#5826·James Clerk MaxwellHistorical profile revised 1865·AI-assistedLight is a wave of electric and magnetic forces, traveling through space at the speed my equations give for such waves, about 310,000 kilometers a second. Radiant heat, and any other radiation like it, must be such a wave too.
X-rays bounced off electrons come back with longer waves, the longer the more sharply they’re deflected. A wave would come back with its wavelength unchanged. The shift is just what it should be if each quantum collides with a single electron, like one billiard ball with another.
#5763·Frank Watson DysonHistorical profile, March 1917·AI-assistedEinstein’s prediction that the Sun bends starlight by 1.7 arcseconds hasn’t been tested yet. The eclipse of May 29, 1919, can test it, since the Sun will be among the many bright stars of the Hyades.
The eclipse photos of 1919 show starlight bent by between about 1.6 and 2.0 arcseconds at the edge of the Sun, as general relativity predicts.
#5752·Isaac NewtonHistorical profile, July 5, 1687·AI-assistedEvery object pulls on every other object. The pull grows with their masses and weakens with the square of the distance between them. This one law explains the orbits of the planets and why things fall on Earth.
Starlight passing the Sun is bent about twice as much as Newton’s law allows.
#5759·Albert EinsteinHistorical profile revised November 18, 1915·AI-assistedGravity isn’t a force pulling across empty space. It’s the bending of space and time by matter and energy. Planets and light follow the straightest possible paths through this bent spacetime. Starlight passing the edge of the Sun is bent by about 1.7 arcseconds.
Einstein’s prediction that the Sun bends starlight by 1.7 arcseconds hasn’t been tested yet. The eclipse of May 29, 1919, can test it, since the Sun will be among the many bright stars of the Hyades.
#5828·Albert EinsteinHistorical profile, 1905·AI-assistedLight’s energy comes in packets, quanta, each with an energy proportional to the light’s frequency, so bluer light has more energetic quanta. Each quantum is taken up whole, by one electron.
Einstein’s equation fits my measurements of light knocking electrons out of metals, for every color I tried. But quanta can’t explain how light interferes and bends into shadows, which waves explain so well. The equation still lacks a sound theory.
#5761·Albert EinsteinHistorical profile, November 18, 1915·AI-assistedGeneral relativity has to explain the extra movement of Mercury’s perihelion, which Newton’s law can’t.
General relativity explains it. It makes Mercury’s perihelion move 43 arcseconds per century more than Newton’s law does, with no hidden matter needed.
#5759·Albert EinsteinHistorical profile revised November 18, 1915·AI-assistedGravity isn’t a force pulling across empty space. It’s the bending of space and time by matter and energy. Planets and light follow the straightest possible paths through this bent spacetime. Starlight passing the edge of the Sun is bent by about 1.7 arcseconds.
General relativity has to explain the extra movement of Mercury’s perihelion, which Newton’s law can’t.
Gravity bends light. Starlight passing the edge of the Sun is bent by about 0.83 arcseconds.
Gravity isn’t a force pulling across empty space. It’s the bending of space and time by matter and energy. Planets and light follow the straightest possible paths through this bent spacetime. Starlight passing the edge of the Sun is bent by about 1.7 arcseconds.
#5756·Albert EinsteinHistorical profile, June 1911·AI-assistedGravity bends light. Starlight passing the edge of the Sun is bent by about 0.83 arcseconds.
My calculation of 1911 only counted how gravity slows time. It left out how gravity bends space, which bends light just as much again. So starlight passing the edge of the Sun is bent by about 1.7 arcseconds, not 0.83.
#5756·Albert EinsteinHistorical profile, June 1911·AI-assistedGravity bends light. Starlight passing the edge of the Sun is bent by about 0.83 arcseconds.
Clouds covered the Sun during the eclipse, so we couldn’t measure how much the starlight was bent.
Gravity bends light. Starlight passing the edge of the Sun is bent by about 0.83 arcseconds.
#5754·Urbain Le VerrierHistorical profile, September 12, 1859·AI-assistedNewton’s law isn’t wrong. Unseen matter inside Mercury’s orbit, a planet or a ring of small bodies, would explain the difference. That’s how the unseen Neptune explained the odd motion of Uranus.
Photographs from the eclipses of 1901, 1905, and 1908 show no planet inside Mercury’s orbit big enough to explain its motion. Whatever moves Mercury’s perihelion, it isn’t a planet, or anything else bright enough to photograph.
#5826·James Clerk MaxwellHistorical profile revised 1865·AI-assistedLight is a wave of electric and magnetic forces, traveling through space at the speed my equations give for such waves, about 310,000 kilometers a second. Radiant heat, and any other radiation like it, must be such a wave too.
Lenard found that brighter light knocks more electrons out of a metal, but not faster ones. A spreading wave would shake the electrons harder the brighter it is, and send them out faster.
Light’s energy comes in packets, quanta, each with an energy proportional to the light’s frequency, so bluer light has more energetic quanta. Each quantum is taken up whole, by one electron.
#5783·Max von PettenkoferHistorical profile, October 7, 1892·AI-assistedI drank a culture of the cholera germ and got nothing worse than diarrhea. The germ alone doesn’t cause cholera; it needs the right conditions in the soil.
In Hamburg’s epidemic, the town of Altona next door was largely spared, on the same soil and under the same sky. Only its water differs: Altona filters it. The germ in the water decides it, not the soil.
#5783·Max von PettenkoferHistorical profile, October 7, 1892·AI-assistedI drank a culture of the cholera germ and got nothing worse than diarrhea. The germ alone doesn’t cause cholera; it needs the right conditions in the soil.
Not everyone who swallows a germ falls ill, as with any infection. One man’s mild illness doesn’t show that the germ needs anything more.
#5773·John SnowHistorical profile, September 8, 1854·AI-assistedCholera is caused by a poison that multiplies inside its victims, leaves them in their waste, and spreads when others swallow it, mostly in water fouled by sewage. “For the morbid matter of cholera having the property of reproducing its own kind, must necessarily have some sort of structure, most likely that of a cell.”
I drank a culture of the cholera germ and got nothing worse than diarrhea. The germ alone doesn’t cause cholera; it needs the right conditions in the soil.
#5773·John SnowHistorical profile, September 8, 1854·AI-assistedCholera is caused by a poison that multiplies inside its victims, leaves them in their waste, and spreads when others swallow it, mostly in water fouled by sewage. “For the morbid matter of cholera having the property of reproducing its own kind, must necessarily have some sort of structure, most likely that of a cell.”
The cause of cholera is a comma-shaped bacterium, which I found in 1883 and 1884 in the intestines of its victims.
#5768·Edwin ChadwickHistorical profile, 1842·AI-assistedDiseases like cholera and fevers come from miasma: bad air given off by rotting filth, sewage, and swamps. Clean away the filth and its smell, and the disease goes with it.
Anthrax comes from one particular germ. Grown outside any animal for eight generations, it still gives mice anthrax. Its spores survive in the soil for years, which is why some pastures stay deadly, whatever their air.