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Are photons massless?

Are photons massless? If so, how is light “bent” around planets & stars?
Tim from Channel Islands (Age 45-54)


3 Responses

  1. Photons are indeed massless as you have said.
    We normally talk about how gravity pulls objects with mass towards each other, however Einsteins theory of Relativity told us we could describe it another way.
    Relativity tells us that objects with mass actually bend space-time; Light always travels in a straight line, however when it gets near a star, space-time is warped. This means that as it travels in a straight line it follows the warped space and seems to bend.
    The easiest way to understand this is if we imagine a sheet of rubber (or something elsatic) pulled tight. If you put a heavy ball on this sheet it will distort the sheet around the ball. If you now roll a smaller ball across the sheet in a straight line it will follow the curve in the sheet that the larger ball has created.

  2. Photons are massless and the answer is that objects fall in a gravitational field at the same rate irrespective of the mass object.

    I agree that this is not intuitive at all but I’m sure you heard of the famous case af Galileo dropping a cannonball and a marble off the Leaning Tower of Pisa (probably not what actually happened). Now, air resistance may complicate matters, but in a vacuum both of these would hit the floor at the same time.

    Einstein took this idea much further and had the idea that mass actually curves spacetime. Something that weighs as much as the sun actually bends space so much we can see the effect of light being bent by it.

    Incidentally, the reason that it is so hard to see light falling under gravity is because it is travelling so quickly. This means it moves a very long way in the time it takes gravity to shift it by a small amount.

  3. When it is said that anything that occupies space and has mass is called matter to what does the term mass refer–to inertia or perhaps the quantity of matter? When I say that matter is anything that has mass and occupies space to what does the term mass refer to? Does it refer to dimensive quantity[amount of stuff under dimensions] ?
    If we take a particle that is solid to what does it owe its solidity? If we say a particle is a mass particle what does the term mass refer to? Perhaps it is better to say the particle consists of matter and has a certain solidity which is the property called density.
    When we say a photon is massless what does one mean? It’s rest mass is 0 and consequently it has no mass [whatever mass is]?
    The notion that there is no rest mass arises because the photon is in constant motion. Is the photon pure energy? Certainly the photon has inertia or its speed would be infinite. It has a limiting principle. And a photon must necessarily have matter of some kind. Everything has matter that exists. The non acceptance of this reality leads to endless confusion as seen in the usage of the terms matter and mass.
    Does not one talk of dark matter and dark energy as if they are the same. And if they are they have different modes of existence depending on conditions. What does one mean by matter in the terms dark matter? Matter and energy cannot be the same but energy can be a property of matter unless one means that matter and energy are the exact identical things.
    Does a photon have density? Is it not a particle and is it not a solid particle or are we just to say it seems to have these characteristics? Do photons not bounce off things? Or is this only the appearances and its really pure energy that has momentum and acts like a particle? How is anything pure, raw energy?
    If light has matter this opens up the whole question of gravity as well challenging space-time as gravity.

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