The Earth is not a perfect sphere; it is an oblate spheroid, meaning it is slightly flattened at the poles and bulges at the equator due to its rotation. However, when space probes or satellites capture images of the Earth from a distance, they often appear to show the Earth as a sphere. This can be attributed to a few reasons:
Perspective: When viewing the Earth from space, the distance and angle from which the image is taken can affect the apparent shape. From a significant distance, the Earth's oblate spheroid shape may not be readily apparent, and it may appear more spherical.
Limited field of view: The cameras on space probes and satellites typically have a limited field of view, capturing only a portion of the Earth at a time. The images are often composited or stitched together to create a full view of the Earth. During this process, any irregularities in shape or curvature may be minimized or not visible due to the limited perspective.
Image processing: Images captured by space probes often go through processing and enhancement before being released to the public. These processes can include adjusting colors, contrast, and sharpness to create visually appealing and scientifically useful images. In the process, any minor irregularities in shape may be further diminished or not visible in the final images.
It's important to note that while the images may portray the Earth as a sphere, scientists and researchers are well aware of its actual oblate spheroid shape. They have precise measurements and models that accurately describe the Earth's shape, taking into account the flattening at the poles and bulging at the equator. The spherical representation is simply a visual simplification for the sake of convenience and ease of understanding in many cases.