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Compared with a completely still universal reference point, how fast am I moving and in which direction? (continued)

Robin Maguire
Hobart, Tasmania, Australia

In terms of linear motion, who are we to say whether or not the entire universe is moving to the left at a million miles an hour, or northwards at an inch per aeon?

When it comes to how fast you're moving and in which direction, Monty Python's Galaxy Song sums things up nicely

But for rotational displacement, the situation is entirely different. Some measurable effects depend on an absolute rate of angular velocity. If we can put a satellite into a stable circular orbit and measure its exact distance from the centre of Earth, this will enable us to calculate its orbital period in absolute terms, and thus to discover in absolute terms the true rotational speed of Earth, or the solar system, or the universe.

Common sense suggests that the universe cannot be rotating too fast, or else the centrifugal effects would mess up all those expanding universe calculations and someone would have noticed. On the other hand, might this explain some of the mysteries about dark matter?

Richard Miller
London, UK

You could name any speed you wanted (up to the speed of light) and that would almost certainly be your speed relative to something somewhere in the universe. Pick whatever reference point makes the most sense for the context, be it Earth, the sun, the Milky Way or something even larger.

Gerald Legg
Hurstpierpoint, Sussex, UK

Monty Python’s summarises things nicely.

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