The maximum speed at which an object can hit Earth without breaking apart depends on various factors such as the object's size, composition, and structural integrity, as well as the angle of entry and the Earth's atmospheric conditions.
When an object enters Earth's atmosphere, it experiences intense aerodynamic forces and heating due to air resistance. These forces can cause the object to break apart or burn up if it exceeds certain speed limits.
For smaller objects like meteoroids or asteroids, they usually burn up in the atmosphere if they are traveling at speeds above a few tens of kilometers per second. This is because the air friction generates tremendous heat, causing the object's surface to melt or vaporize. However, smaller objects are more likely to burn up due to their relatively larger surface area-to-mass ratio.
Larger objects, such as spacecraft or artificial satellites, are typically designed to withstand the re-entry forces and can survive higher speeds. The exact speed limit for such objects depends on their design and construction. For example, space shuttles were designed to withstand re-entry speeds of around 28,000 kilometers per hour (17,500 miles per hour), while the Apollo capsules that carried astronauts back from the Moon reached speeds of approximately 39,000 kilometers per hour (24,000 miles per hour) during re-entry.
In summary, the maximum speed an object can hit Earth without breaking apart depends on its size, composition, design, and atmospheric conditions. The specific speed limit would vary for different objects and scenarios.