PigKnight
First Post
I'm pretty sure c is a grade some people get in physics class.
I C wut u did there.
But, for realsies, why is it called c? Latin? Kicks-n-giggles? Discovering scientist?
I'm pretty sure c is a grade some people get in physics class.
But, for realsies, why is it called c? Latin? Kicks-n-giggles? Discovering scientist?
At the time the limit was discovered, the only massless particle known was the photon.
Are photons really massless though? I mean theyre all the time getting sucked into black holes, if they had no mass a black hole wouldnt affect it, right?
Relation to gravity
In physics, there are two distinct concepts of mass: the gravitational mass and the inertial mass. The gravitational mass is the quantity that determines the strength of the gravitational field generated by an object, as well as the gravitational force acting on the object when it is immersed in a gravitational field produced by other bodies. The inertial mass, on the other hand, quantifies how much an object accelerates if a given force is applied to it. The mass–energy equivalence in special relativity refers to the inertial mass. However, already in the context of Newton gravity, the Weak Equivalence Principle is postulated: the gravitational and the inertial mass of every object are the same. Thus, the mass–energy equivalence, combined with the Weak Equivalence Principle, results in the prediction that all forms of energy contribute to the gravitational field generated by an object. This observation is one of the pillars of the general theory of relativity.
The above prediction, that all forms of energy interact gravitationally, has been subject to experimental tests. The first observation testing this prediction was made in 1919.[30] During a solar eclipse, Arthur Eddington observed that the light from stars passing close to the Sun was bent. The effect is due to the gravitational attraction of light by the sun. The observation confirmed that the energy carried by light indeed is equivalent to a gravitational mass. Another seminal experiment, the Pound–Rebka experiment, was performed in 1960.[31] In this test a beam of light was emitted from the top of a tower and detected at the bottom. The frequency of the light detected was higher than the light emitted. This result confirms that the energy of photons increases when they fall in the gravitational field of the earth. The energy, and therefore the gravitational mass, of photons is proportional to their frequency as stated by the Planck's relation.
Yes. Light moves at the speed it does because that's the fastest anything can move. Other things move at that speed, too - radio waves, the whole EM spectrum, lots of stuff.
The speed of light's a bit of a misnomer - light moves at various speeds, up to the universal speed limit. In different mediums, it slows down. In a vacuum, though, light moves at c.
Hi,
I'm finding two (in the end, equivalent) explanations:
1) Gravity works on the total energy of an object.
2) Light always travels in straight lines. Or rather, since on a curved surface, "straight line" requires modification, light always travels along the shortest possible line between points. Then, gravity causes space-time to be curved, and the straight lines of light in gravitationally flat space are modified to the apparently curved lines in the curved space near a mass.
Does light actually slow down in different media, or does it simply take a longer path (by, say, reflecting off multiple particles resulting in a wandering, yet relatively straight, path)?
Ahh ok, #2 makes sense, #1 is a little harder for me to wrap my brain around.
I read the article, and while I'm no physicist, I have to say that I'm not impressed.
Talking about the "speed" of light ties into another one of our quantum-physics problems: we don't much understand what Time is, either.
We get a lot of great examples of the watch that doesn't turn as many times when it's close to the speed of light, or the person who doesn't age as much. But if the position of a watch's hands are what determines how much time has elapsed, then I can make time speed up or slow down with my pinky. Or if it's time that ages people, why all the anti-aging focus on anti-oxidants and other nutrients?
But - does a photon have an age? Can a graviton be a spring chicken?