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This week’s new questions

Is there anoptimal way to clean a glass jar? What would the horizon and landscape look like on a disc-shaped “flat Earth” planet?

2B5DJY0 Row of homemade jars of jam for sale on the market counter.

An easy way to clean out a glass jar is to pour some water in it, screw on the lid and shake it. Is there an optimal amount of water to put in for the most effective cleaning?

Alan Baker
Swarthmore, Pennsylvania, US

A 3D illustration of the now debunked competing conspiracy theory that the Earth is flat, as it appears from land, rather than spherical. Earth texture maps courtesy of NASA.gov; Shutterstock ID 1240127368; purchase_order: -; job: -; client: -; other:

What would the horizon and landscape look like on a disc-shaped planet?
Gary Miller
Metamora, Michigan, US

Last Word is 鶹ý’s long-running series in which readers give scientific answers to each other’s questions, ranging from the minutiae of everyday life to absurd astronomical hypotheticals. To answer a question or ask a new one, email lastword@newscientist.com

To answer this question – or ask a new one – email lastword@newscientist.com.

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