Scientists debated whether multiple observable universes could leave detectable imprints on the cosmic microwave background.

Even with the most powerful telescopes, we can only map a fraction of the observable universe.

We rode the observation wheel at dusk to watch the city lights.

The city's skyline was dotted with observation wheels that lit up like constellations at night.

After reviewing the data, the scientist identified an observational error that explained the discrepancy between the expected and measured values.

The report highlighted several observational errors that affected the study's conclusions.

The regiment relied on an observation balloon to direct artillery fire across the foggy valley.

Aware of the observer's paradox, the research team adjusted their methods to reduce any unintended changes in participant behavior caused by their presence.

At dawn, the biologists climbed into the observation hut to watch the migrating birds.

The researchers spent the night in the observation huts to monitor the migratory birds.