Questions in this tag must be answered in a manner that can be understood by a general audience with at most a basic understanding of physics, mathematics and related sciences. Apply it to questions where the asker clearly requests such answers.

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6
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2answers
2k views

Popular books on QM

After some discussions with my friend about some "popular" aspects of quantum mechanics, my friend asked me whether there exist any books that could convey the basic ideas in a non-technical way (my ...
0
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1answer
62 views

How do individual masses 'add up' to create a gravitational field?

The combined mass of the Earth is responsible for its local gravitational force. However, this combined mass is made up from of lots and lots (and lots) of atoms, each with their own individual mass ...
80
votes
9answers
9k views

How fast does gravity propagate?

A thought experiment: Imagine the Sun is suddenly removed. We wouldn't notice a difference for 8 minutes, because that's how long light takes to get from the Sun's surface to Earth. However, what ...
3
votes
0answers
52 views

Red shift and expansion of universe [duplicate]

We have been led to believe that in the theory of universe expansion, the farthest object is moving faster away from us than the nearest object, attributing the difference to red shift. Question: is ...
1
vote
2answers
100 views

Meaning of “realism” in quantum mechanics

When physicists doing work in quantum measurement, decoherence, Bells' inequalities etc. use the term "realism" what exactly do they mean? I'm looking for answers targeted towards, say, someone whose ...
4
votes
4answers
113 views

Is the Air Blue? [duplicate]

Randall Monroe, a credible source in my opinion, says that the sky is blue because the air is: Normal light interacts with the atmosphere through Rayleigh scattering. You may have heard of ...
3
votes
1answer
24 views

In the Holometer experiment, why would one of the split laser beams arriving back at a slightly different time indicate the universe was quantized?

All the pop-sci articles I've read have a description of the set-up similar to this: It uses a pair of laser interferometers placed close to one another, each sending a one-kilowatt beam of light ...
5
votes
2answers
2k views

Why does a glass breaks when subject to very sharp sound like in opera?

I have seen in Ripleys believe it or not that an opera singer generates a very high frequency of sound and breaks a glass window.How do they do it?
1
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0answers
19 views

Why is a rainbow in the sky always an arch? [duplicate]

It's been raining a lot lately in the bay area of California (thankfully! keep it coming rain gods!) which puts me and my dad in a contemplative mood. The rain has given us something to contemplate: ...
3
votes
1answer
188 views

Moving the endpoints of a wormhole towards each other

Suppose we have a perfectly safe portal/wormhole and we place the two endpoints facing each other so that a person between them would see an endless corridor (with infinite number of herself). What ...
1
vote
0answers
19 views

How to introduce symmetry of particles to a layperson? [closed]

I want to introduce the concept of special unitary symmetry and how it is important in particle physics to a layperson. Without being technical, is there a way to explain the fundamental concept?
462
votes
20answers
176k views

Cooling a cup of coffee with help of a spoon

During the breakfast with my colleagues, a question popped into my head: What is the fastest method to cool a cup of coffee, if your only available instrument is a spoon? A qualitative answer would ...
1
vote
0answers
28 views

Is the electron of carbon identical to that of hydrogen? How to prove it? [duplicate]

I am still confused with whether, for example, the electron of carbon is exactly identical to that of hydrogen. How can the scientist confirm this?
11
votes
2answers
950 views

How can I explain or demonstrate the Lorentz Force to a 12 year old?

I'm a space physicist. I've been working with a group of school students (aged between around 10 and 12) exploring the Sun, the Earth and the solar system. We've talked about some basics of magnetism ...
21
votes
5answers
5k views

Does a car consume more fuel when it's raining?

Yesterday my wife asked me that question, and I couldn't answer. Consider a car, in a sunny day, and that is consumes x gallons per mile. Considering that everything is equal, except that it's ...
2
votes
2answers
81 views

Would a person in a gravity well observe the sky as rapidly moving due to time shift?

Inspired by the movie Interstellar (2014) - I was wondering about the crew on the surface of the planet which was deep in the gravity field of the black hole (Gargantua) - if they would look up at the ...
0
votes
1answer
35 views

are GPS points versus an area?

I have a $\text{i2c}$ GPS module I got working yesterday, and here are my co-ordinates. Latitude: 44.901354999999995 Longitude: -68.97112333333333 What I am having trouble figuring out is that ...
4
votes
4answers
186 views

What is the way to prevent the cream from settling on the surface of hot milk with least manual labour?

I have seen Cooling a cup of coffee with help of a spoon but that question has a restriction of using only a spoon. My problem is that I have to boil the milk before pouring it in the bottle for the ...
7
votes
3answers
593 views

Why (in relatively non-technical terms) are Calabi-Yau manifolds favored for compactified dimensions in string theory?

I was hoping for an answer in general terms avoiding things like holonomy, Chern classes, Kahler manifolds, fibre bundles and terms of similar ilk. Simply, what are the compelling reasons for ...
25
votes
4answers
5k views

Is space “real”, or is it some sort of accepted postulate?

What is space? It seems to be everywhere in the equations of physics, as some sort of postulate or hidden hypothesis. We also have a direct experience of it, but is it "real"? The fact that we ...
19
votes
1answer
4k views

Physics behind this neutrino-related joke

In the comment section of a newspaper article reporting on the 2015 Nobel Prize for Physics, which was awarded for work on neutrino oscillation, I found the following joke: "I'm sorry, we do not ...
5
votes
2answers
415 views

Better explanation of the common general relativity illustration (stretched sheet of fabric)

I've seen many science popularisation documentaries and read few books (obviously not being scientist myself). I am able to process and understand basic ideas behind most of these. However for general ...
1
vote
0answers
90 views

A model that predicts the universe is finite in space and time

A physics professor talked in the YouTube video Cosmological Constant & The End of the Universe - Sixty Symbols about a paper he and his colleagues published. The paper presents a model that ties ...
5
votes
1answer
258 views

Is a singularity a real thing?

I've heard the work a few times now, the most recent in the star trek film. Is a singularity a real thing? If so what is it?
-3
votes
2answers
119 views

Why is there uncertainty in physics? [closed]

In physics, why do we come up with a theory that is unable to explain what is actually going in a phenomenon? Just we are creating a theory which explains the results and satisfies the data, does ...
0
votes
1answer
114 views

Would a pipe from the surface to the Earth's exosphere suck all atmosphere to the space? [closed]

If I built a tube from Earth's surface to the exosphere, would all the air be sucked out to space? If this pipe reached to a big planet, like Jupiter, would its gravity through the pipe suck our ...
75
votes
8answers
8k views

Why does space expansion not expand matter?

I have looked at other questions on this site (e.g. "why does space expansion affect matter") but can't find the answer I am looking for. So here is my question: One often hears talk of space ...
4
votes
1answer
887 views

Negative Energy and Wormholes

Apparently to create wormholes you need negative energy/matter. Say you had negative matter/energy, how would it be applied towards making a wormhole?
6
votes
5answers
9k views

Is coherent light required for interference in Young's double slit experiment?

In this Veritasium video, a home experiment is presented which appears to produce a very good double-slit interference pattern with normal sunlight. The experiment is an empty cardboard box with a ...
5
votes
3answers
787 views

Big bang and time

I heard Carl Sagan talking about the Universe 15 Billion years ago, and the Big Bang. He made the statement that it was the biggest explosion of all time (at first I thought this a subtle pun). This ...
81
votes
7answers
9k views

Why is there a scarcity of lithium?

One of the major impediments to the widespread adoption of electric cars is a shortage of lithium for the batteries. I read an article a while back that says that there is simply not enough lithium ...
1
vote
3answers
185 views

How is this possible that photons are absorbed?

From the lessons on QM, I got impression that there are some discrete orbitals that emit light when electron drops from one to another. Specific molecules emit light in very narrow bands, therefore. ...
2
votes
1answer
202 views

How does a tightrope walker return to equilibrium?

I do not understand how tightrope walkers return themselves to equilibrium. I am not concerned with the direction along the rope or wire where their base can be large, and they are able to move ...
0
votes
0answers
73 views

Is this a good explanation of electron mobility to the layman?

I'm writing an informative paper on graphene for my writing class (layman-oriented), and was describing electron mobility in very simplified terms. Let me know if anything is mistaken, badly ...
1
vote
2answers
818 views

If time stops for an object, does that object feel gravity?

As far as I understand The GTR, it is said that Mass bends space-time which causes gravity. So every Mass in this universe is flowing through space-time example earth is moving along with space-time ...
2
votes
2answers
328 views

Many-worlds interpretation vs 'just' randomness?

I have this question about MWI I always wanted to ask but never dared to! It could be that I just don't know enough physics to understand the answer, or the question! Anyway, here goes: What is it ...
13
votes
9answers
8k views

Is there a proof of existence of time?

It seems to me that there is no such thing as time. There is only movement in the universe and we compare our own movement to a different object to have a sense of time. It can be a clock or a atomic ...
6
votes
3answers
3k views

What are the fundamental problems of being in a 2 dimensional world?

I was reading through Stephen Hawking's explanation of two - dimensional space. In that he mentioned that it will be very difficult to design a living being that could exist only in 2 dimension. What ...
7
votes
4answers
5k views

Can you make ice red hot?

This video clip allegedly shows an otherwise unspecified ice cube that turns red hot (and burns) due to induction heating. Can somebody explain how this works?
12
votes
8answers
4k views

Why are extra dimensions necessary?

Some theories have more than 4 dimensions of spacetime. But we only observe 4 spacetime dimensions in the real world, cf. e.g. this Phys.SE post. Why are the theories (e.g. string theory) that ...
1
vote
2answers
6k views

Is water considered a substance with low friction or high friction?

Like, for example, rubber is a substance with high friction, as an object with neither high or low friction would easily stop on it, and wouldn't skid. Ice is considered an object with low friction, ...
0
votes
0answers
13 views

How 2nd-order nonlinear optic response is used in the telecom market?

References According to this paper, 2nd order NLO response is important for telecom. According to Wikipedia, Lithium niobate is used extensively in the telecoms market, e.g. in mobile telephones ...
30
votes
4answers
9k views

Blowing your own sail?

How it this possible? Even if the gif is fake, the Mythbusters did it and with a large sail it really moves forward. What is the explanation?
10
votes
2answers
1k views

Movie airplanes and suction

Having watched a recent action movie (with zombies in it) I wondered whether the suction from a hole in the airplane's hull would really be able to rip out luggage, persons and even seating benches. ...
3
votes
1answer
330 views

Does decreasing the length of the line between a harness and zip wire increase the velocity at which you travel?

My friend is an instructor at an outdoor adventure centre which has lots of zip wires. The instructor's harness has a shorter line that attaches to the zip wire than the normal harness does and she ...
0
votes
1answer
109 views

Scientific Laws for Engineering Materials [closed]

I have a conceptual question. There is a law in science for every phenomenon in nature, like gravity or electric field. But also there are laws for springs or capacitors etc... I mean the ...
1
vote
3answers
145 views

Why did scientists need to invent light years?

Why did scientists need to invent light years? What's so important about having a light year? I have been learning that a light year is $9.461 \times 10^{15} \, \mathrm{m}$. My question is, why are ...
2
votes
1answer
62 views

The fly and the sphere of iron

When I was a child, I read something like the following in a book whose name I have now forgotten (I tried to find the original quote on the web, but although there are some similar passages the ...
6
votes
3answers
641 views
13
votes
6answers
5k views

What is our location relative to the Big Bang?

Given what we know about space, time and the movement of galaxies, have we or can we determine what our position is in relation to the projected location of the Big Bang? I've read some introductory ...