Description Usage Arguments Details Note Author(s) Examples

Getting and setting the speed of light

1 2 3 |

`c` |
Scalar, speed of light. If missing, return the speed of light |

`downstairs` |
Boolean, with default |

`to_natural,change_time` |
Boolean, specifying the nature of the passive transform matrix |

In the context of an R package, the symbol “c” presents particular problems. In the gyrogroup package, the speed of light is denoted “sol”, for ‘speed of light’.

The speed of light is a global variable, governed by
`options("c")`

. If `NULL`

, define `c=1`

.

Function `eta()`

returns the Minkowski flat-space metric

*
omitted*

Note that the top-left element of `eta()`

is *-c^2*, not
*-1*.

Function `ptm()`

returns a passive transformation matrix that
converts displacement vectors to (`to_natural=TRUE`

) and from
(`to_natural=FALSE`

) natural units. Argument `change_time`

specifies whether to change the unit of time (if `TRUE`

) or the
unit of length (if `FALSE`

).

Typing “`sol(299792458)`

” is a lot easier than typing
“`options("c"=299792458)`

”, which is why the package uses
the idiom that it does.

Robin K. S. Hankin

1 2 3 4 5 6 7 8 9 | ```
sol() # returns current speed of light
sol(299792458) # use SI units
sol() # speed of light now SI value
eta() # note [t,t] term
u <- as.3vel(c(100,200,300)) # fast terrestrial speed, but not relativistic
boost(u) # boost matrix practically Galilean
is.consistent.boost(boost(u)) # should be TRUE
sol(1) # revert to relativisitic units
``` |

RobinHankin/gyrogroup documentation built on Feb. 19, 2019, 3:20 a.m.

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