Earth Speeding Through the Universe and How is Speed Measured in Spacecraft

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Did you know that we're travelling at 600,000 km/hr on planet Earth as our home galaxy, the Milky Way, orbits the Local Group, a group of neighbouring galaxies? That's somewhat faster than the mere 1000 km/hr velocity of a point on the island of Ireland, due to the Earth turning on its axis. We don't experience the effects of constant velocity on our bodies, only acceleration and deceleration. So we can't tell whether we're stationary or moving. In space, there aren't any wheels on the ground or axles that can be used to determine velocity by measuring how fast they turn (in older cars, there was simply a cable connected between the driveshaft and speedometer). Aircraft use pitot tubes mounted in the fuselage, with an orifice at the end of the tube exposed to moving air. As air flows over the hole, pressure drops in the tube and this can be converted into a velocity measurement. Spacecraft don't have this luxury because there's no air in space, and instead uses accelerometers. These measure acceleration and deceleration. A process known as dead reckoning can then be employed to determine velocity (by integrating acceleration, knowing how long that acceleration acted for) and distance travelled (by integrating velocity, knowing how long the velocity lasted). Ancient mariners also used dead reckoning to determine their position in the ocean by regularly measuring a vessel’s speed in knots and its direction using a compass.