To determine how long it takes to cross the Milky Way galaxy in Earth's reference frame, we need to consider the concept of "light-year" and the speed of light.
A light-year is a unit of distance, defined as the distance light travels in one year, which is approximately 9.46 trillion kilometers (or about 5.88 trillion miles).
Given that it takes 52,000 light-years to cross the Milky Way galaxy, we can calculate the corresponding distance in kilometers or miles. Multiplying 52,000 by the distance of one light-year, we find that it is approximately 491 trillion kilometers (or about 305 trillion miles).
Now, let's consider the speed of light. In a vacuum, light travels at a speed of about 299,792 kilometers per second (or approximately 186,282 miles per second).
To determine the time it would take to cross the Milky Way in Earth's reference frame, we divide the distance by the speed of light. Using the distance of 491 trillion kilometers, we find that it would take roughly 1.64 million years to traverse the Milky Way.
It's important to note that this calculation assumes a constant speed of light and doesn't account for relativistic effects or the fact that humans currently do not possess the means to travel anywhere near the speed of light. Therefore, in practical terms, the timeframe to cross the Milky Way remains far beyond our technological capabilities with current understanding and technology.