If aliens landed on Earth tomorrow, what would they eat?

With the release of "Disclosure Day," Steven Spielberg's new film about aliens, a question as old as science fiction itself resurfaces: If aliens were to arrive on Earth, would they come to conquer us, to study us. or perhaps to eat. The science-journalism coverage adds useful context, while the strongest evidential footing still comes from the underlying data, papers or institutional documentation.

It is relevant because Earth science becomes stronger when local observations can be placed inside a broader physical pattern that spans time and geography. The planet operates as a coupled system in which atmospheric, oceanic, cryospheric and solid-Earth processes interact across timescales from days to millions of years. A measurement that captures one variable at one location and one moment has limited interpretive value until it is embedded in the longer series and wider spatial coverage that allow natural variability to be separated from forced change. By José Miguel Soriano del Castillo, The Conversation This article has been reviewed according to Science X's editorial process and policies. There is no scientific evidence that extraterrestrial beings have visited Earth, let alone any information about what they eat.

But the literal meaning of "extraterrestrial" is simply "from outside Earth. " In that broad sense, the only extraterrestrials whose diet we know of are, oddly enough, humans. While their experiences do not tell us what an alien would eat, they do show us that leaving Earth changes the way we eat.

A creature weighing 70 kilograms (154 pounds) would require around 1, 700 kcal per day, similar to an adult human at basal metabolic rate. And an alien weighing 150 kilograms (331 pounds) could need more than 3, 000 kcal per day, even without moving around a lot.

Discover the latest in science, tech, and space with over 100, 000 subscribers who rely on Phys. org for daily insights. A 150 kg endothermic reptilian might need 3, 000 kcal a day at rest, and considerably more if it engages in physical activity.

The broader interest lies in linking the observation to climatic, geophysical or environmental dynamics that extend well beyond the immediate event or location. Earth science is unusual in that its most important questions operate on timescales that no single research career can observe directly, making the archival record, whether in ice, sediment, rock or satellite data, as important as any new measurement. Results that can be embedded in that record, and that either confirm or challenge the patterns it reveals, carry disproportionate scientific weight.

If an extraterrestrial visitor were based on carbon, water and chemistry similar to that found on Earth, our planet would offer them a somewhat risky buffet. On Earth, for instance, a koala is almost entirely dependent on eucalyptus, while a cow needs its particular microbiota to digest the cellulose in grass.

Because this item comes through Phys. org Space as science journalism, it should be treated as contextual reporting rather than primary evidence. Good science reporting can identify why a result matters, connect it to the wider literature and make technical work readable, but the decisive evidence remains in the original paper, dataset, mission release or technical record. That distinction is especially important when a story is later repeated by aggregators, because repetition increases visibility, not evidential strength.

The next step is to place the result inside longer time series and to compare it with independent instruments and independent sites. Earth system observations gain most of their interpretive power from network density and temporal depth, not from any single measurement however precise. Model simulations that assimilate the new data will help clarify whether the observation fits comfortably within known natural variability or represents a shift that existing models do not reproduce.

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