Sergey Nemirovsky/Shutterstock
How come, when the front door of my house is open, a fly can enter my home easily, but not escape as easily out of the same door?
David Gibson,
Ashburton, New Zealand
Shutterstock / YIUCHEUNG
We know the maximum possible speed is that of light in a vacuum. But is there a maximum possible acceleration too?
John Corey,
Melrose, New York, US
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