The visibility of our buildings and lights to alien civilizations depends on several factors, including the distance to those civilizations, the technology they have to detect signs of life on other planets, and whether they are actively searching for signs of life.

For example, Earth’s lights are visible from space to astronauts and probes orbiting our planet. In addition, our radio and television broadcasts have been traveling through space for decades, forming a “bubble” of electromagnetic signals that extends ever further away. However, the vastness of space and the limited speed of light mean that these signals become extremely weak as they travel away from Earth, which could make them difficult for distant alien civilizations to detect.

If there are sufficiently advanced alien civilizations nearby, it is possible that they could detect our signals and even identify the presence of life on our planet. However, so far we have no concrete evidence of contact with alien civilizations, and the question remains largely speculative.

How could ETs see our buildings?

If advanced alien civilizations possess sufficiently sophisticated observation technology, they could detect our constructions in several ways:

1. **Optical observation:** Just as we use telescopes to observe distant stars and galaxies, alien civilizations could use advanced optical technology to detect structures on distant planets. Large structures such as skyscrapers, bridges, and even large man-made structures like the Great Wall of China could be visible through powerful telescopes.

2. **Remote sensing:** Remote sensing technologies, such as radar and satellites, could be used to map a planet's surface and identify geometric patterns that indicate the presence of built structures.

3. **Infrastructure signals:** In addition to physical structures, alien civilizations could also detect infrastructure signals, such as artificial lights at night, radio emissions, and other electromagnetic signals generated by our technological activities.

4. **Environmental changes:** Human construction and industrial activities can cause significant changes to a planet's environment, such as deforestation, air pollution, and urbanization. These changes could be detected by alien civilizations studying the atmospheric composition and surface of distant planets.

In short, if an alien civilization possesses advanced observation technology and is actively searching for signs of life on other planets, it is possible that they could detect our human constructions and activities.

Observing the construction of the first pyramids in Egypt

Observing the first pyramids in Egypt would be a fascinating event for an alien civilization. The pyramids are impressive structures, built thousands of years ago using techniques that were advanced in engineering and architecture at the time.

An advanced alien civilization could observe the construction of the pyramids in several ways:

1. **Optical observation:** Using powerful telescopes, they could observe changes in the landscape as the pyramids were built over time. They could record detailed images of the construction techniques used by the ancient Egyptians.

2. **Remote Sensing:** If they had advanced remote sensing technology, they could detect variations in temperature, radiation patterns, and other characteristics of the area where the pyramids were being built. This information could reveal patterns of human activity associated with the construction of the pyramids.

3. **Infrastructure analysis:** They could detect geometric patterns and complex structures emerging in the landscape, indicating the construction of the pyramids. In addition, they could detect changes in the infrastructure around the pyramids, such as the construction of roads and the movement of building materials.

4. **Environmental Monitoring:** An advanced alien civilization could monitor environmental changes caused by the construction of the pyramids, such as the extraction of building materials, the displacement of earth, and the impact on local water and vegetation conditions.

Observing the construction of Egypt's first pyramids could offer valuable insights into the history and technological capabilities of human civilization to an alien civilization interested in studying other life forms in the universe.