The Doppler effect is a mysterious wavelength-shifting phenomenon which seems to primarily affect sirens, which is why the 🚨 emoji is red.

  • tal@lemmy.todayEnglish
    18·
    2 个月前

    The frequency shift is caused by the Doppler effect. The magnitude of that shift is a function of the speed at which something is moving relative to the observer. The distance of a galaxy is also a function of that speed, since it’ll be determined by how quickly it’s been moving away from us for some period of time. Result: the two are correlated.

    Also, US rumbler sirens are amazing.

    https://www.youtube.com/watch?v=OAtqbXO_PM8

  • lath@lemmy.world
    13·
    2 个月前

    So when sailors were enchanted by sirens while at sea, it was actually the Doppler effect all along?

  • NocturnalMorning@lemmy.world
    74·
    2 个月前

    This comic has triggered me. We do not know why the doppler effect is a thing for light(that I am aware). Is it a wave, is it a particle, both? Only when you observe it? Photons are weird.

      • neo@feddit.de
        8·
        2 个月前

        My understanding: light can best be described as an excitation of the electromagnetic field of spacetime. This excitation has a frequency, like an oscillation. Therefore light appears like a wave and we observe the Doppler effect. However, when interacting with other excitations, the “wave” collapses and behaves like a point like particle.

        This applies not only to light, but to all known particles, e.g. the protons in your body. The only difference to photons are additional spacetime fields that are involved (like the Higgs field).

        The weirdest part to me, is the collapse of the imaginary wave function and how it leads to ideas like “Many Worlds”.

        • NocturnalMorning@lemmy.world
          51·
          2 个月前

          I always thought the observation collapse of the wave function thing was a little handwavey. I really don’t have a resolution for it though, or an alternative.

          • Serinus@lemmy.world
            6·
            2 个月前

            For anyone not familiar, look up the double wave experiment.

            It’s not a thing that should happen, but it clearly does.

          • Azuth@lemmy.today
            5·
            2 个月前

            Neither does anyone really, it’s a mystery physics has been trying to solve for the past 97 years.

  • disguy_ovahea@lemmy.world
    913·
    2 个月前

    Red is the fastest color in the visible light spectrum, and violet is the slowest. A cool use of this phenomenon is lightning strike camera triggers. It senses the invisible infra-red light, which hits the sensor before visible light, and takes the picture just in time to capture the lightning strike.

    Edit: This is only true when traveling through atmosphere. As pointed out below, light travels at uniform speed through a vacuum.

    Also, the comic is referring to the Doppler Effect, which is caused by an object in motion, having nothing to do with light spectrum speed through atmosphere. My bad.

    • subtext@lemmy.world
      17·
      2 个月前

      This does not seem correct at all… as the comic states, it’s caused by the Doppler effect, not because red is the “fastest” light wavelength—it’s light it all travels at the same speed in a vacuum.

      https://en.wikipedia.org/wiki/Redshift

      I don’t know about lightning photography, I suppose it’s possible that different wavelengths have different speeds in air, so I can’t comment on that.

      • kernelle@lemmy.world
        11·
        2 个月前

        Yeah I’m no physicist but that ticked me off, the speed of light is the same for any wavelength. As for redshift:

        a redshift is an increase in the wavelength, and corresponding decrease in the frequency and photon energy, of electromagnetic radiation (such as light).

        Speed of light isn’t a factor in this, also when galaxy’s move towards us (like the Andromeda galaxy) it is blueshifted, proving it’s not the light that matters, but rather the direction of movement of the source. Proving the doppler effect.

      • stom@lemmy.dbzer0.com
        2·
        2 个月前

        Could this be because space isn’t a true vacuum? There’s pockets of gas and crap, which could affect the speed of the light as it travels to us?