## Physics Stack Exchange by Kiwix

Q&A for active researchers, academics and students of physics

### Most popular questions

640 Cooling a cup of coffee with help of a spoon 2011-02-16T12:09:27.020

414 Can I compute the mass of a coin based on the sound of its fall? 2014-06-26T11:27:38.900

386 How does light bend around my finger tip? 2014-05-03T00:20:47.187

366 How does gravity escape a black hole? 2010-11-16T17:39:59.213

310 Book recommendations 2011-07-12T06:04:21.747

301 Why are mirror images flipped horizontally but not vertically? 2011-04-07T19:39:39.457

262 Do we know why there is a speed limit in our universe? 2016-01-20T17:07:17.560

257 Why don't metals bond when touched together? 2013-11-19T18:29:00.520

256 What experiment would disprove string theory? 2010-11-02T19:51:03.887

256 Why do ballpoint pens write better on pages that have pages below them? 2017-10-08T13:39:06.593

245 What is Chirped Pulse Amplification, and why is it important enough to warrant a Nobel Prize? 2018-10-02T17:27:32.137

238 Did the Big Bang happen at a point? 2014-09-23T10:03:58.110

230 If I sliced the universe in half, would the slice go through a star? 2018-02-26T12:15:12.960

225 Why are four-legged chairs so common? 2016-01-20T15:58:46.377

224 How do towels stay on hooks? 2018-01-23T21:10:25.330

222 What really allows airplanes to fly? 2010-11-06T03:23:18.563

211 Don't heavier objects actually fall faster because they exert their own gravity? 2011-01-21T20:10:15.837

199 Why does kinetic energy increase quadratically, not linearly, with speed? 2010-11-10T23:59:43.297

195 Why is the detection of gravitational waves so significant? 2016-02-11T14:18:42.637

190 Surviving under water in air bubble 2013-06-13T21:56:04.640

188 Strange ice found in my garden 2018-02-22T09:58:09.703

184 What exactly is a photon? 2016-08-07T10:27:03.637

180 Does Earth really have two high-tide bulges on opposite sides? 2014-06-25T21:59:42.257

164 Why does NASA use gold foil on equipment and gold-coated visors? 2013-08-17T11:03:26.700

163 When separating an Oreo cookie, why does the cream stick to just one side only? 2017-05-31T20:24:18.367

162 Are units of angle really dimensionless? 2016-04-27T00:54:45.537

160 Why doesn't matter pass through other matter if atoms are 99.999% empty space? 2014-07-14T19:36:10.020

158 Could Legolas actually see that far? 2014-07-02T16:54:49.210

158 How does a knife cut things at the atomic level? 2014-09-05T18:09:07.077

151 How do I explain to a six year old why people on the other side of the Earth don't fall off? 2014-01-20T13:29:55.347

150 Why do we actually see the sun? 2013-07-03T19:52:25.150

148 Why do shadows from the sun join each other when near enough? 2014-01-18T15:15:04.017

147 Why does Stephen Hawking say black holes don't exist? 2014-01-26T15:44:30.467

146 If photons have no mass, how can they have momentum? 2010-12-24T13:17:10.747

146 Why do sunbeams diverge even though the sun is much more than a few kilometers away? 2014-12-25T11:14:54.877

142 Simple check for the global shape of the Earth 2018-10-15T06:46:21.803

141 Why are the wet patches on these floor tiles circular? 2018-03-03T22:04:19.710

140 Why is my hand not burned by the air in an oven at 200°C? 2017-01-28T18:50:27.967

139 Why does space expansion not expand matter? 2010-12-21T03:59:29.420

139 Why don't electrons crash into the nuclei they "orbit"? 2012-01-25T15:04:37.523

139 Why is nuclear waste more dangerous than the original nuclear fuel? 2016-11-16T02:55:13.973

138 Why are the harmonics of a piano tone not multiples of the base frequency? 2016-07-17T16:45:32.343

137 Why does a mirror split my laser beam? 2016-03-02T15:01:41.830

135 Why do we not have spin greater than 2? 2011-09-21T13:36:34.750

135 Is $\pi^2 \approx g$ a coincidence? 2016-08-22T02:13:11.797

133 What makes a theory "Quantum"? 2018-04-04T18:54:42.803

131 Why are the windows of bridges of ships always inclined? 2017-01-08T20:45:37.587

129 If you view the Earth from far enough away can you observe its past? 2011-07-06T15:39:21.670

128 Gauge symmetry is not a symmetry? 2011-08-23T02:48:20.713

126 How can you weigh your own head in an accurate way? 2013-07-12T08:51:59.347