Science desk
< January 3	<< Dec \| January \| Feb >>	January 5 >

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is a transcluded archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

January 4

The loopholes that form the galaxy part 2 ，to make the question clearer

According to the law of entropy increase, the longer the time, the more serious (degeneration) from order to disorder, that is, stars with energy emit energy outward. This shows that the universe cannot evolve, there is only one creator. Before the evolution of the solar system, the distribution of energy and matter was even, just like a cup of hot coffee, and then evolved into the current solar system with regular energy and matter distribution. This process violates experimental phenomena. After the Big Bang, energy and matter spread outward. Where did the matter and energy form galaxies? — Preceding unsigned comment added by Fluenceerr11001 (talk • contribs) 03:39, 4 January 2021 (UTC)[reply]

You may wish to read "Dissipative system". Graeme Bartlett (talk) 03:42, 4 January 2021 (UTC)[reply]

Entropy reduction can only be used on the earth, biological, because biological genes control entropy reduction.That article only mentioned the earth, not the universe. So it cannot be used in the universe, because the universe is matter and the environment is close to nothingness.@Graeme Bartlett: — Preceding unsigned comment added by Fluenceerr11001 (talk • contribs) 14:32, 5 January 2021 (UTC)[reply]

Well on galactic scale see Lambda-CDM model and Galaxy formation and evolution (PS previous paragraph was not my writing, just pinging me) Graeme Bartlett (talk) 00:30, 6 January 2021 (UTC)[reply]

Rain, probability of

What is the average probability of rain falling at any particular time in any particular part of the world? Sandbh (talk) 04:24, 4 January 2021 (UTC)[reply]

We could answer using the probabilistic quantitative precipitation forecast; but any answer we provide could throw off our threat score. The simple act of making a quantitative forecast affects the verifiable reliability of all other predictions.... Nimur (talk) 08:46, 4 January 2021 (UTC)[reply]

Bullet deceleration

Similar questions have been asked elsewhere in the internet, but I want to resolve two specific experiments (in both cases no wind is assumed):

1 If everything is calculated properly for a given firearm and a given bullet, would a person standing at a proper distance (apparently slightly exceeding the effective range of that firearm) see the decelerating bullet aimed at him and falling to his feet?
2 If the shooter shoots in a ballistic trajectory and, again, if everything is calculated correctly, would another person standing at a foo distance see the decelerating bullet falling from the sky and potentially catch it?

Thanks. 212.180.235.46 (talk) 09:57, 4 January 2021 (UTC)[reply]

It'd still be going very fast if it was initially pointed at him but yes if it'd hit the ground near his feet then potentially bounce into him, even if it was a rainbow-like arc it'd be dangerously fast to catch, see celebratory gunfire deaths. Mythbusters has shown that bullets are never slow unless they point straight up. Even if it was exactly straight up which would require great accuracy and your blimp altitude was not one foot wrong so it would be almost no speed it'd still be spinning fast which may or may not hurt your skin. And you might need bottled oxygen for the sticking your hand out the blimp part. Being hit by them on the way down is not advised. Sagittarian Milky Way (talk) 10:57, 4 January 2021 (UTC)[reply]

It will be difficult to see the bullet, but catching it in a reflex should be possible, just like Isao Machii can slice bullets fired at him in half. Count Iblis (talk) 11:40, 4 January 2021 (UTC)[reply]

With a kevlar mitt, see celebratory gunfire deaths. Sagittarian Milky Way (talk) 11:55, 4 January 2021 (UTC)[reply]

Catching a bullet travelling at 30 metres per second (98 ft/s)? Don't try this at home, kids. --Lambiam 12:29, 4 January 2021 (UTC)[reply]

Would a bigger bullet travel slower than a smaller bullet and be easier to see and catch? TrogWoolley (talk) 14:42, 4 January 2021 (UTC)[reply]

Bigger of the same shape and initial speed will of course be less affected by air resistance and have higher terminal velocity when shot exactly up which is the only way to make the bullet tested in the article hit as slowly as 30 meters per second. I would not even try the Mythbusters shooting straight up method, what if there's an error and it's half the speed of sound? Sagittarian Milky Way (talk) 15:13, 4 January 2021 (UTC)[reply]

This anecdote ain't worth much but it may be better than absolutely nothing. Once upon a time at a target range, a bullet out of nowhere – presumably aimed too high from a neighboring range – hit the ground about 4~10 metres from me. Yes, I saw it come down. —Tamfang (talk) 06:04, 8 January 2021 (UTC)[reply]

The Science Of Why Firing Your Gun Up Into The Air Can Be Lethal says that a spent bullet falls at about 150 miles per hour (241 kilometers per hour) depending on size, which I imagine is slow enough to see if you're looking in the right direction. It also says that a .30 rifle bullet can pierce human skin at 85 mph (137 kph). This report says that an astonishing 65 American people died from stray bullets in one year. Alansplodge (talk) 17:00, 9 January 2021 (UTC)[reply]

Delayed response to heat

When I touch the kettle with my palm to check if it's hot enough, I've noticed that the thermal sensation is delayed by about 1-2 seconds (meaning initially I don't feel anything and then the burning sensation comes rapidly as if multiplied). Why is that? I'm healthy for the record and believe this has something to do with human physiology, perhaps others also experience it 212.180.235.46 (talk) 17:24, 4 January 2021 (UTC)[reply]

Nerve conduction velocity for heat is slow. Also heat has to conduct through your dead skin to activate ze heat sensors and heat them to the new higher equilibrium temperature they'll have in that hand-kettle geometry which isn't instant. Sagittarian Milky Way (talk) 17:43, 4 January 2021 (UTC)[reply]

What's more, before you touched the kettle, it was cooled by room-temperature air of maybe 18°C. Assuming you're talking about an electric kettle (the kettles you put on the stove get far to hot to touch), it will be made of a poor heat conductor like plastic, so the outside surface doesn't get very hot. Once you touch it, the air cooling stops and the temperature will rise. PiusImpavidus (talk) 09:35, 5 January 2021 (UTC)[reply]

We don't use electric kettles in America, 120 volts is too low for the normal wire size to carry the watts. You just put the kettle on the methane or electric stove and heat the water. Sagittarian Milky Way (talk) 13:45, 5 January 2021 (UTC)[reply]

How quaint. Alansplodge (talk) 00:09, 6 January 2021 (UTC)[reply]

But the fire is an advanced fire. I can heat spoons orange in them. Sometimes the thick metal coil is even covered with a glass that doesn't crack to make spill cleaning easier. Don't expect that in a cheap $1300 apartment miles from Manhattan though. You can also get the fire one but that doesn't need thick-ass special wires (rods?) or more 120 volt wires than usual to power all those like iron coils. It does need a pipe that goes from your metal crown of methane to Oklahoma though. How much power do your futuristic kettles use by the way? The circuit breaker or fuse will trip if whatever keeps the power at 1,800 or 2,400 watts max fails here. This is why portable appliances like vacuum cleaners often have 1,800 watts. I once lived 4 miles from Manhattan CBD and I had to unscrew a light bulb-type fuse for drawing 1,801 watts in the wrong set of sockets. The fuse strip melts and destroys the fuse to make sure the copper wall wires don't. This building was almost floor-length dress old — which is young for Brooklyn. Sagittarian Milky Way (talk) 00:46, 6 January 2021 (UTC)[reply]

During male orgasm, what really happen in brain?

I like to know During male orgasm, what really happen in brain? From various medical sites, I came to know that contractions of muscles occur throughout the body, but what happens in brain? Rizosome (talk) 17:45, 4 January 2021 (UTC)[reply]

Happiness. Sagittarian Milky Way (talk) 17:49, 4 January 2021 (UTC)[reply]

Our article: Orgasm#Brain. -- ToE 19:50, 4 January 2021 (UTC)[reply]

Wikipedia:Reference desk/Archives/Science/2021 January 4

Contents