How can a dimension be hidden?
Extra dimensions pop up everywhere in physics. From string theory to attempts at unifying general relativity with quantum theory. But how can it be that we can’t see them?
(more…)Category: Special Relativity
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Why Is There No Sound Postulate?
In physics, the speed of a wave is defined independently from the speed of its source.
Then why did Einstein say that the speed of lightwaves is independent of their source – why not claim that the speed of any wave is independent of its source?
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A derivation of the Minkowski metric
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A derivation of the Lorentz equations
For a future blog post I’m working on, I would like to show how the Lorentz transformations are derived. To remind you, the Lorentz transformations tell us how variables change when we go from one reference frame to another one that is moving relative to the first.
We start in a reference frame S, in which there is only one spatial dimension, $x$. Now compare S with a reference frame S’ moving with velocity $v$ in a positive $x$ direction. How do we relate $x$ and $t$ in S to their equivalents $x’$ and $t’$ in S’?
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Trains, clocks and lightspeed
Yesterday I received an email with a very interesting question about Einstein’s lightclock. Why do we assume that light in a moving lightclock travels a longer distance than in a clock that stands still? If we throw a ball into the air in a moving train, it falls down vertically, right? Why is that different for a clock? This is a great question! It helps us realise what it actually means to say that things happen in absolute space (as Newton believed).
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Galilean Relativity
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