Stack Exchange Network

Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

Questions tagged [physics]

Use this tag for questions about the physical nature of reality and in particular claims that are strictly about the field of physics. Please use specific tags if the question is about other sciences such as chemistry. Also consider to add [electromagnetism] and [radiation] if appropriate.

221
votes
4answers
26k views

Does hot water freeze faster than cold water?

Is it true that hot water freezes faster than cold water and if so, what practical applications have there been found for this phenomenon?
218
votes
2answers
32k views

Has man walked on the Moon?

Is there any concrete, solid proof of this space odyssey? Is there a way that I personally have a look a it? Let's say, with a nice telescope ?
177
votes
1answer
18k views

Do cats always land on their feet?

Assuming a fall from a survivable height, will a cat always land on its feet? Has this been studied? Is there real data to back it up?
122
votes
5answers
23k views

Do atoms exist?

There are plenty of examples of people doubting ([1], [2], [3], [4], [5]) or denying ([6], [7], [8]) the existence of atoms. Is there any compelling evidence for the existence of atoms? Has anyone ...
103
votes
5answers
7k views

Are personal electronics a risk to commercial aviation?

Are personal electronics (of present or recent past; e.g. cell phones, mp3 players, iPads) a risk to commercial air travel? Is the typical request to "turn off all personal electronic devices" based ...
94
votes
4answers
35k views

Can bullets fired into the air kill a person when they fall?

Lately, I've been watching the Libyan civil war in the media, and both sides in the conflict often celebrate success by firing their AK-47s into the air. Not to say that firing guns into the air is ...
81
votes
1answer
8k views

Does this video show a water droplet in gravitational orbit?

Andrew Rader, an author and engineeer, tweeted a GIF video showing a droplet of water rotating around some sort of probe. Everything has gravity - here's a droplet of water orbiting a needle in 0G....
74
votes
2answers
13k views

Do snowballs snowball?

"Snowball" as a verb, means to increase rapidly in size - a reference to the Snowball Effect: The common analogy is with the rolling of a snowball down a snow-covered hillside. As it rolls the ball ...
72
votes
1answer
11k views

Are the claims made by Indian Ministers / personalities regarding ancient Indian inventions true?

In the past couple of years, several Indian Ministers / personalities have made claims regarding existence of modern inventions in Ancient India. Prime Minister Modi claimed that genetic science ...
69
votes
4answers
14k views

Do wooden building fires get hotter than 600°C?

After the recent Notre-Dame de Paris fire, there has been a heavily re-posted tweet going around in response to an earlier claim that a golden cross did not melt or deform - due to an act of God. ...
65
votes
1answer
8k views

Antistatic bracelet without a ground connection

Last winter in Japan, some of my friends were buying bracelets like this, that claim to prevent or reduce static shocks: Here is an advertisement picture describing how it is supposed to be used, ...
64
votes
2answers
8k views

Does water have a memory as claimed in homeopathy?

In homeopathic remedies the original substance is often diluted to a point where statistically there should be not a single molecule left of the original substance. The most common explanation by ...
62
votes
2answers
7k views

Are old glass panes thicker on the bottom due to “flow”?

I ran into this common belief today, and was surprised that it has not been addressed here before. I think this belief is common enough that most anyone has heard it. Especially if they are touring ...
58
votes
2answers
15k views

Has the laser at Magurele, Romania reached a tenth of the Sun's power?

This month the laser at Magurele, Romania became the most powerful laser in the world, according to various sources. Related: Is the laser built in Măgurele, România, the most powerful in the ...
57
votes
1answer
15k views

Does a column of marching soldiers have to break their rhythm while crossing a bridge to prevent its collapse?

I recently stumbled across this article "Why are soldiers ordered to break their marching steps while crossing a bridge?" (The Times of India) where a claim is made: When soldiers march in three ...
56
votes
1answer
69k views

Did an F-15 airplane successfully land with just one wing?

I've just been forwarded a video about a jetfighter landing with just one wing and I wonder if this could indeed be true. Here's the link to the video: One-Winged F 15 Crash Landing Video (landing ...
56
votes
1answer
24k views

Is Starlite a hoax?

About 40 years ago, Maurice Ward, a hairdresser and amateur chemist, developed a plastic that was said to be resistant to extreme heat. Able to withstand a laser beam that could produce a temperature ...
54
votes
3answers
13k views

Does plutonium exist in the world, apart from being manufactured?

In reference to the Manhattan Project at Los Alamos, a mathematician, Peter Lax, described his time working there as "living science fiction". He said: we were told essentially the basic thing: ...
53
votes
4answers
12k views

Does water swirl the opposite way on the other hemisphere?

I have heard this one several times but was never given a convincing explanation. Is this a real phenomenon? (Bonus points for a good physical description of the behavior or reasons it couldn't occur....
52
votes
3answers
63k views

Can cats survive a fall from any height?

So here's the premise. A cat reaches its terminal velocity after around 10meters of free fall. A cat can survive a landing from a speed equal to its terminal velocity. Therefore a cat can survive a ...
50
votes
1answer
47k views

Are Katanas made of steel folded 1000 times?

A Katana needs to be made of steel folded 1000 times, according to eHow: Pound the tamahagane into two separate blades. These need to be heated, pounded by hand, and folded 1,000 times each to ...
48
votes
3answers
133k views

Is it unsafe to swim during a lightning storm?

I was cautioned by mom that I mustn't go swimming when there is lightning; the theory is that it is more likely for lightning to hit you when you are in the water. Is this fear justified?
47
votes
2answers
10k views

Will a bullet be split in half if it hits a butter knife that is fixed in place?

I was reading a manga, and I saw this: So I was wondering. Will a bullet be split in half if it hits a butter knife that is fixed in place? Have there been experiments to test that?
47
votes
1answer
7k views

Did Benjamin Franklin perform an experiment by flying a kite in a lightning storm?

Is there any credible evidence that Benjamin Franklin actually did his famous kite experiment?
44
votes
1answer
15k views

Is it impossible to fold a sheet of paper in half more than seven times?

It's a commonly stated belief that no one can fold a piece of paper in half after doing so seven times. Even I have been unable to fold a piece of normal paper for an 8th time. Is this true for ...
43
votes
2answers
15k views

Are nebulae colored?

The pictures of nebulae are always depicted as vividly colored and with a great variety of colors: Source Omega nebula Source Eagle nebula pillars According to the English wikipedia article on ...
42
votes
3answers
13k views

Can mountains on Earth grow higher than 49,000 feet (15,000 m)?

I just saw this picture in Learn Something Every Day and thought of you. Some of the sites I've found reason it with gravity but doesn't explain very well.
41
votes
2answers
14k views

Is it safe to stand by the windows during a thunderstorm?

There is widespread belief in my culture that we should not stay near door or windows during lightning. So people advise others to stay inside house with doors and windows closed to be safe from ...
38
votes
1answer
11k views

Did/does the US government keep secret papers by Nikola Tesla?

A popular conspiracy theory holds that Tesla invented a free energy device, but that the powers that be prevented him from publishing it, because it would hurt their investments. Of course, free ...
38
votes
2answers
38k views

Can you recharge non-rechargeable alkaline batteries?

There are conflicting reports of whether it is possible to safely recharge alkaline batteries (not lithium) that are not sold as rechargable. The packaging for batteries regularly has cautions ...
36
votes
1answer
10k views

Did a nuclear blast devastate Port Chicago on July 17, 1944?

On July 17, 1944 at the Port Chicago naval base, near the San Francisco Bay area, an explosion of epic proportions occurred on a dock handling munitions. The Evening Independent, Jul 18, 1944, via ...
35
votes
2answers
3k views

Did Thomas Edison test 1600 materials for the filament of his light bulb?

From this webpage: In 1879, after testing more that 1600 materials for the right filament, including coconut fiber, fishing line, and even hairs from a friend's beard, Edison and his workers ...
34
votes
2answers
11k views

Did Manahel Thabet develop a groundbreaking formula to measure distance in space without the use of light?

I stumbled upon the Wikipedia page of Manahel Thabet recently. Here are some extracts from the Wikipedia page. "At the age of 25, she earned her first PhD in Financial Engineering magna cum laude, ...
34
votes
1answer
22k views

Reading while lying down is more strenuous (unhealthy) for eyes

My friend heard that reading while lying down is more strenuous (unhealthy) for eyes. I like reading in bed (books, tablet). Is there some study that confirms this hypothesis? I use two positions (...
33
votes
2answers
6k views

Is alcohol for consumption tested for carbon-14 radioactivity to be considered legal?

I just viewed this interesting video about radioactive ethanol from plants as opposed to non-radioactive ethanol from crude oil. In it, the professor says he's heard it's illegal in the USA to sell ...
32
votes
3answers
25k views

Do knives get dull in dishwashers?

Everybody keeps telling me don't put knives in dishwashers. And if I ask them why, nobody seems to have an answer or an argument to support his/her advice. So I thought I'll shoot the question to ...
31
votes
2answers
6k views

Does the Gravitational constant fluctuate?

Rupert Sheldrake recently had a TEDx presentation removed from the TEDx web-site, for making various controversial claims, basically calling all of science into doubt. I am highly skeptical about ...
30
votes
1answer
10k views

Did the Quran predict the speed of light?

It appears to be popular to claim that the Qur'an predicted the speed of light before it was scientifically well understood. Although none of the sources state that outright, that is what they imply. ...
30
votes
1answer
3k views

Is it dangerous to throw a coin off a building?

A long time ago I had this discussion with some people if throwing a coin of a building is dangerous (potentially deadly) if it hits someone. The height of the building should be skyscraper-like so ...
30
votes
2answers
33k views

Is biting a gold coin a working method to verify its authenticity?

Julia Murray & Kelsey Serwa In movies you commonly see treasure hunters, pirates, thieves, ... bite down on a gold coin to verify it's real gold. (Gold Medal winners often pose with the medal ...
30
votes
0answers
609 views

Does cutting paper dull a knife quickly?

This question is a follow-up to "How to test the sharpness of a knife?", my answer to it, and the comments my answer generated. Charlie Brumbaugh wanted to know how to tell when he is done when ...
29
votes
1answer
14k views

Did Albert Einstein say “the only reason for time is so that everything doesn't happen at once”?

The quote The only reason for time is so that everything doesn't happen at once. is attributed to Einstein with some regularity. (For example, Google returns 47,700 results, of which all except 5,...
29
votes
1answer
2k views

Did this building cause carpet to burn and cars to melt?

The BBC reports that a building with curved glass in London appears to have caused damage nearby as a result of the architecture focusing the sun's rays. Seems plausible enough to me, but is this ...
29
votes
1answer
68k views

Is leaving your AC fan (blower) on 24/7 during summer more efficient than leaving it on auto?

The AC guy that fixed my AC recently said I should turn my AC fan on 24/7 and this would increase the efficiency of my AC system. I looked it up and found this same claim in several places: City Data ...
29
votes
1answer
2k views

Can the health of an alkaline battery be determined by bouncing it?

I was just sent a YouTube video, which appears to demonstrate that one can determine the "health" of a battery (current voltage, useful lifetime remaining, etc.) by bouncing it on a level surface. A ...
28
votes
5answers
11k views

Is the “Back to the future” Huvr board real?

This website is promoting a hovering skateboard. As far as my knowledge can tell, this seems fake. The only two known technologies I know of which can hover like that are magnets and quantum ...
28
votes
1answer
4k views

Is NASA working on warp drive?

I am cynical about a report on Gizmodo that NASA is developing Warp Drive. This was trending on Google Plus tonight and gathering a bit of attention. http://gizmodo.com/5942634/nasa-starts-...
28
votes
1answer
12k views

Is there any data on how efficient Tesla wireless power transmission was?

It's widely believed that Nikola Tesla not only demonstrated wireless power transmission but his works in this field were very successful. Wikipedia only says this The electric energy transmitted ...
28
votes
1answer
5k views

Do trackers hold their ears to the ground?

There is a trope (in movies and cartoons and elsewhere) of Native American (or other) trackers are sometimes depicted as listening to the ground to presumably hear far away horses or other animals ...
27
votes
1answer
7k views

Did a lightning strike make a river roll and boil?

There's a video that I just came across on Facebook: original source: http://www.youtube.com/watch?v=TD2hyCUePL0 alternative copy: https://www.facebook.com/hardbond/videos/10155610316509339/ In the ...