I have difficulty with accepting his way of calculation. I wonder if he first adjusted all movement in different directions into a single displacement vector. I doubt it by his choice of words.
i doubt he used vector addition as well. i readily admit that he leaves out quite a few variations in net velocities. for instance, the angular velocity caused by the rotation of the earth combined with the angular velocity of the earth orbiting the sun yields a net velocity for an observer on the earth's equator that varies between the maximum value of ~70,400 mi/h that he mentions in the video, and a minimum velocity of ~68,320 mi/h that he doesn't mention in the video. note that this is only the velocity of an observer on the earth's equator
with respect to the sun.
likewise, he speaks of only one velocity of the earth with respect to the Milkyway Galaxy. but just as in the situation above, the angular velocity of the earth as it orbits the solar system combined with the velocity of the solar system as it orbits the Milkyway results in a net velocity that again oscillates between a minimum and a maximum value. note that this is only the velocity of the earth
with respect to the core of the Milkyway Galaxy.
but what specifically is it about his method that you have difficulty accepting? is it the final summation of velocities he does toward the end of the video? if so, i also disagree with that method. in reality, he's not summing velocities - rather he is only summing speeds at that point. and he is summing speeds that do not yield a very accurate velocity of the earth or an earthling observer with respect to the center of the galaxy due to the fact that all of those calculated speeds rarely, if ever, have the same exact direction. in other words, depending on the location of an observer on the earth's equator as it rotates, the location of the earth in its orbit about the sun, and the location of the solar system in its orbit about the galaxy, the net velocity is more than likely going to be a combination of sums and differences of speeds due to their varying directions, and not just a sum of the absolute values of all the calculated speeds.
that being said, i think he still comes up with a fairly accurate representation of our velocity around the center of our galaxy. the angular velocity of an equatorial observer with respect to the center of the earth and the angular velocity of the earth around the sun is insignificant in comparison to the both angular velocity of the solar system around the galaxy and the velocity of the solar system as it travels above and below the plane of the galaxy. if we were outside the Milkyway looking in, velocities induced by the earth's rotation and orbit would hardly be noticeable and contribute a minimal amount of accuracy to our actual velocity as were move through the galaxy. in other words, his roundabout calculation of ~575,000 mi/h is probably fairly accurate, give or take a certain margin of error that might be in the thousands of milers per hour.
i really don't care to comment on his ideas regarding the speed of the galaxy itself through the universe. while i suppose its possible to calculate the speed of the galaxy as it plows through the interstellar medium, there is certainly no way to calculate its speed relative to a body that is absolutely stationary with respect to the universe - there is no such thing, and there is no such concept.
...and i think his estimate, despite just being a fun thought experiment, is still fairly accurate up to a certain point.
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