Module 02
Amsterdam, Netherlands
Every one of these numbers is a distance measured against something. Change what you measure against and the answer changes — by a factor of a thousand.
measured against the Sun
This is the largest frame in which every digit is exact. Your rotation and Earth's orbit both come from real ephemerides, so nothing here is assumed. The frames below are just as honest, but two of them rest on a measured constant rather than a computed one.
Earth runs fastest in early January, at its closest to the Sun, and slowest in early July. That is a spread of about a kilometre per second across the year. Your birthday, 15 JUN 1990, is marked.
Not stages of one trip. Four separate answers to the same question, each complete in itself.
Rotation alone. At the equator this is 1,674 km/h; at the poles it is nothing at all. Computed from your latitude, not assumed.
Your rotation added to Earth's orbit as vectors, not as numbers. At midnight the two work together and you are moving faster than at noon — and Earth itself runs from 29.3 to 30.3 km/s depending on where it is in its ellipse.
The Sun circles the galactic centre once every 225 million years. Its speed is the least certain number here: published values run from 220 to 250 km/s, and we use 247.
The closest thing to being still that the universe offers: the frame in which the afterglow of the Big Bang looks the same in every direction. This already includes the galactic orbit — it does not get added on top.
Why you cannot add up speeds — the reference frames explained →
Values used, and where they come from
Rotation and orbit: computed per instant from astronomy-engine (MIT), not from a fixed figure. Earth's own state vector, and yours from your latitude.
Sun around the galactic centre: 247 km/s. Genuinely uncertain — published values run from 220 to 250 km/s, so treat this figure as good to about ten per cent.
Sun against the microwave background: 369.82 km/s towards galactic longitude 264.021°, latitude 48.253° (Planck 2018 dipole). This is the Sun's motion, not the Local Group's 620 km/s.
Galactic to equatorial conversion checked against the known position of the galactic centre and pole.