3 claim verifications about bacteria bacteria ×
“The "five-second rule" — the belief that food dropped on the floor is safe to eat if picked up within five seconds — prevents the transfer of harmful bacteria to food.”
The five-second rule does not prevent harmful bacteria from transferring to dropped food. Peer-reviewed research, including a comprehensive 2016 Rutgers study, shows bacteria can transfer to food in less than one second upon contact. While longer contact times may increase contamination, there is no safe window. Factors like moisture, surface type, and contamination level often matter more than time. The claim is not supported by scientific evidence.
“If all the world's bacteria were stacked on top of each other, the resulting column would stretch approximately 10 billion light-years.”
The claim that stacked bacteria would stretch "10 billion light-years" is misleading. Using the most widely cited estimate of ~5×10³⁰ bacteria at ~2 µm average length, the stack reaches roughly 1 billion light-years — a full order of magnitude less. Even generous assumptions (including archaea) yield ~6 billion light-years. The only sources citing "10 billion" are popular trivia pages, while the original 1998 Whitman estimate actually claimed "a trillion light-years." The general concept of an astronomically vast distance is valid, but the specific figure is not mathematically supported.
“Approximately half of the cells in the human body are non-human cells, primarily composed of microorganisms such as bacteria.”
The claim is largely accurate. The best peer-reviewed research (Sender et al., 2016) estimates ~38 trillion bacterial cells versus ~30 trillion human cells, making bacteria roughly 56% of all cells — reasonably described as "approximately half." However, this is a point estimate for a 70 kg adult male with significant uncertainty (~25%) and population variation. The claim also omits that by mass, bacteria account for only ~0.2 kg, so "approximately half" applies to cell count, not biological dominance.