How would a lunar eclipse appear if Earth had no atmosphere?

A lunar eclipse occurs when the Earth passes directly between the sun and the moon, casting a shadow on the moon. If Earth had no atmosphere, the way light interacts with the environment would be significantly different.

In the absence of an atmosphere, there would be no scattering of sunlight, which normally occurs when light passes through Earth's atmosphere. During a typical lunar eclipse, some sunlight is refracted and scattered through the atmosphere, which can result in the moon appearing a reddish color due to the Earth's atmosphere filtering and bending some of the light (a phenomenon known as Rayleigh scattering). This is often why a lunar eclipse is sometimes referred to as a "blood moon."

If there were no atmosphere, the moon would not receive this refracted light, which means it would be much darker in appearance during the eclipse. Instead of appearing reddish or even somewhat visible due to the atmosphere's influence, the moon would likely appear completely black because it would be fully within the shadow cast by the Earth, without the additional light that atmosphere provides. Thus, the correct outcome in this scenario is that the moon would appear completely black.