1
vote
2answers
285 views

Doubt concerning centripetal acceleration

What is the centripetal acceleration and angular velocity of a child located 8.2 m the center of a carousel? The speed (size of the tangential velocity) of the child is 2.1 m / s A train moves in a ...
7
votes
1answer
1k views

What are the characteristics of the magnetic field surrounding a human brain?

The human brain is said to produce a magnetic field resulting from the action potentials released inside the brain. What's the nature of such a field in terms of size and strength, and what is the ...
3
votes
4answers
381 views

Is a Rubbia thorium reactor safer than other modern reactor types?

I keep wondering how a Rubbia thorium reactor would handle a natural disaster of Fukushima level intensity. As I understand it the nuclear chain reaction would stop instantly if the power is cut, but ...
1
vote
0answers
128 views

Linewidth pressure broadening due to organic molecules

In relation to atmospheric spectroscopy and some other gaseous spectroscopy applications where organic molecules are present in the vapor, does anyone know of any papers or resources on pressure ...
3
votes
2answers
587 views

The most price-efficient experimental setup involving SPDC, single-photon counting etc

I would like a suggestion on a price-efficient way of experimenting with spontaneous down-conversion and single-photon counting. The simple dual-slit experiment could be one part of an application ...
4
votes
1answer
161 views

Wave equation for sound waves and moving source

Is there a way to take a moving source already into account when one derives the wave equation for sound waves and derive from that using only math the Doppler effect for moving sources?
8
votes
4answers
380 views

Direct exposure to the vacuum of space

I was watching a few sci-fi movies and was wondering the real science explaining what would happen if you were to be subject to the conditions of outerspace. I read the wikipedia article on space ...
7
votes
2answers
743 views

What does the data in various stages of analysis from a particle collision look like?

I've been following the news around the work they are doing at the LHC particle accelerator in CERN. I am wondering what the raw data that is used to visualize the collisions looks like. Maybe someone ...
3
votes
5answers
6k views

Conversion of mass to energy in chemical/nuclear reactions

Is mass converted into energy in exothermic chemical / nuclear reactions? My (A Level) knowledge of chemistry suggests that this isn't the case. In a simple burning reaction, e.g. $C+O_2\to ...
11
votes
5answers
2k views

What happens to light and mass in the center of a black hole?

I know that black holes are "black" because nothing can escape it due to the massive gravity, but I am wondering if there are any theories as to what happens to the light or mass that enters a black ...
4
votes
2answers
840 views

How is the mechanism of greenhouse gases interacting with IR radiation?

How does atmospheric CO2 and other Greenhousgases (GHG) affect the incoming (from sun) and outgoing (from earth) radiation. I understand that at certain wavenumbers (or areas of wavenumbers) in the ...
2
votes
1answer
418 views

Does magnetised material lose weight?

I've had argument on a forum about this. People think, that: if the same object is magnetised, it has less energy. so by $E = mc^2$ it weighs less than an object that is not magnetised (hence spin of ...
1
vote
0answers
226 views

Macroscopic superposition of humans and past thoughts? [closed]

Decoherence apparently only works if a lot of degrees in the environment are measured with infinitely many copies reaching to all eternity. If too few memories and records survive with infinitely many ...
5
votes
2answers
199 views

Advice sought on choosing a camera for a Meade LX10

I have a Meade LX10 and have never done any astrophotography (except with some computerised SBIG ST9s on my university's LX200s). I would like to get started at home, but could do with some advice on ...
4
votes
1answer
195 views

Argument for quantum theoretic conformality of $\cal{N}=2$ super-Chern-Simon's theory in $2+1$ dimensions

I am using the standard symbols of $V_\mu$ for the gauge field, $\lambda$ for its fermionic superpartner and $F$ and $D$ be scalar fields which make the whole thing a $\cal{N}=2$ vector/gauge ...
0
votes
1answer
392 views

The acceleration of a particle in uniform electro-magnetic field

A particle of charge $q$ and mass $m_0$ is subject to the action of a uniform electro-magnetic field $\vec{E}=(0,E,0), \vec{B}=(0,0,B)$ and at $t = 0$ moves with velocity $\vec{v}=(v_1,v_2,v_3)$. ...
1
vote
2answers
1k views

Function of electric water pump

What is the function of electric water pump, i.e does it push or pull water or both?
2
votes
2answers
195 views

Reference for solid state particle detector

I'm looking for a good introductory text on solid state devices for particle detection. Thanks a lot.
28
votes
7answers
5k views

Why is the observable universe so big?

The observable universe is approximately 13.7 billion years old. But yet it is 80 billion light years across. Isn't this a contradiction?
18
votes
2answers
951 views

Why is the universe map shaped like an oval?

I understand that the Mollweide projection is used to show the map of the universe. Although I understand how this projection can be interesting for Earth where most populated (and of interest) ...
7
votes
2answers
768 views

Finding Directions using moon

Is it possible to find directions just by looking at moon(not full bright)? I was curious to use the clue that if moon is half lit then the direction in which it is lit will it be east?
2
votes
2answers
1k views

Evaporation from a capillary tube

Consider a capillary tube (say from a liquid / capillary thermometer), that means a tube of small internal diameter which holds liquid by capillary action . The tube is fulfilled with water and closed ...
-1
votes
2answers
659 views

A fan in a hot room at what point does it put in more energy that it dissipates

If a fan that is using 50 watts is moving 1 m³/min of air. Lets say the walls are the same temperature as the air so there’s no heat dissipation there. How do I know if the fan is putting in more ...
18
votes
6answers
66k views

How exactly does time slow down near a black hole?

How exactly does time slow down near a black hole? I have heard this as a possible way of time traveling, and I do understand that it is due in some way to the massive gravity around a black hole, but ...
3
votes
2answers
236 views

electron orbits

Is there an upper limit to the number of orbits an electron can have around say a proton? Arent there states that are unstable(for n!=1) with corresponding mean/half lives and therefore uncertainty in ...
1
vote
1answer
313 views

Artificial Gravity - Spinning Station Questions II

In an answer to Artificial Gravity - Spinning Station Questions Vintage wrote: A theoretical space station of radius 900 meters, doing a complete rotation every 60 seconds (in order to generate ...
3
votes
2answers
399 views

Example of a wavefunction that cannot be represented by a single Slater determinant

I know that in general, interacting fermions cannot necessarily be described by a single Slater determinant. Can anyone provide a simple example of a state that has no such representation?
7
votes
2answers
1k views

Free particle in magnetic field / Landau quantization

I have a question concerning a possible derivation of the Landau quantization. In our lecture notes (and some other places as well), the following ansatz is used: $$ \Psi(x,y,z) = ...
11
votes
4answers
4k views

How to find the Andromeda galaxy without using a go-to telescope?

In other words, what is the proper technique (star-hopping or other?) in order to find and properly point a telescope to this target? Would a star atlas or other tool/reference help? Can I use the ...
4
votes
1answer
527 views

Artificial Gravity - Spinning Station Questions

I've done a little research but I can't seem to find the answers to these questions in regards to a spinning space station simulating gravity. 1) If we imagine the space station as a hollow doughnut ...
2
votes
2answers
2k views

Ascent rate and size of balloon

I am part of a school project, Project Stratos to send a balloon to the edge of space (the closer side :P) and was wondering how you would work out the accent rate of a large balloon (roughly 1m^3 of ...
11
votes
5answers
3k views

How would you describe a black hole to a complete layman?

Non-astrophysicist visitors to Black Hole, will most likely barely make it past the introduction before getting lost in the technical details. Moreover, the Wikipedia article does not teach laypeople ...
14
votes
6answers
1k views

Double light speed

Let's say we have $2$ particles facing each other and traveling at speed of light Let's say I'm sitting on #$1$ particle so in my point of view #$2$ particle's speed is $c+c=2c$, double light speed? ...
9
votes
3answers
1k views

If you throw dynamite into a pool of lava, will it explode or melt?

I was playing a table-top rpg with a friend. It was set... well it was pretty weird, so I won't get into it. Suffice it to say the bad guy had a stick of dynamite and we were on a volcano. I hit the ...
22
votes
7answers
1k views

Can one do the maths of physics without using $\sqrt{-1}$?

The use of imaginary and complex values comes up in many physics and engineering derivations. I have a question about that: Is the use of complex numbers simply to make the process of derivation ...
1
vote
0answers
219 views

Presence Of an Another Universe [duplicate]

Possible Duplicate: Experimental evidence for parallel universes Is there an universe similar to ours somewhere else, I mean I had heard from Einsteins theories that,actually when I am ...
4
votes
2answers
699 views

Is the entire Universe the same age?

Is all of the visible Universe exactly the same age everywhere? What about the Universe beyond what we can see?
6
votes
1answer
33 views

Lack of exoplanet missions in the decadal survey

In recent exoplanet meeting "The Next 40 Years of Exoplanets", there was much discussion of the inablity of the community to agree on whether to support coronagraph missions or interferometer ...
2
votes
0answers
61 views

Degenerated Anderson Model Simulation

I'm trying to simulate the degenerative Anderson model. So depending on an energy difference first orbital and afterwards spin magnetism occurs. First i try to solve an easier ansatz with a limitation ...
0
votes
2answers
154 views

Space Interferometry Mission (SIM) cancellation [closed]

NASA's SIM mission was recently cancelled despite \$600 million being spent already over the last ten years. Has this \$600m been completely wasted or has any new technology been developed that could ...
0
votes
2answers
66 views

Study of exoplanets reaching saturation point [closed]

In recent exoplanet meeting The Next 40 Years of Exoplanets, it was mentioned a few times that the field/topic is becoming saturated. In what ways is it becoming saturated, and can you see the effect ...
6
votes
2answers
1k views

Why is BTZ black hole asymptotically $AdS_3$?

The metric for the BTZ black hole is $ds^2=-N^2dt^2+N^{-2}dr^2+r^2(N^\phi dt +d\phi)^2$ where $N^2=-M+\frac{r^2}{l^2}+\frac{J^2}{4r^2}$ and $N^\phi=-\frac{J}{2r^2}$. It is often said that BTZ black ...
4
votes
4answers
288 views

Could dark energy be the effect of gravity at great distances?

This may be a silly question, but is it possible that dark energy and gravity are related to each other? Space-time is deformed everywhere in space by objects with mass. The more massive the object, ...
5
votes
3answers
247 views

What does a planet look like in the infrared?

I've been trying to find a good source for what the planets look like in the infrared, specifically if viewed as a point source. I've been working with a low resolution telescope that senses in the ...
7
votes
3answers
683 views

Electrons in CRT

In a CRT, where do the ejected electrons go after they cause fluorescence on the screen, have they lost most of their energy, or do they actually go through the glass?
6
votes
2answers
1k views

Why did my liquid soda freeze once I pulled it out of the fridge?

Can someone explain in both layman's terms and also technically why when I pulled my glass filled with liquid soda from the freezer, the liquid soda quickly froze? Doesn't this violate the 2nd law of ...
1
vote
2answers
339 views

Running: Determine how much more energy is needed per extra kilogram of weight

(I recently asked this on maths but was directed here) I have recently become a runner and having a keen interest in kinematics I'm very interested in the maths/physics of my running. Can someone ...
2
votes
0answers
72 views

Complementarity between the laws of physics? [closed]

Is this following proposal plausible, worth considering, or dismissable as lunatic fringe science? What if the universe isn't really what we think it is but some universal quantum computer where we ...
-1
votes
1answer
829 views

How to simplify e to power of j.t [closed]

I have exam tommorow and cant get this figured out :( dont blame me but please answer this question. I Want to simplify this term: 3 times ((e topowerof 5jt) + (e topowerof -5jt)) Thanks.
16
votes
2answers
208 views

What is a “Trojan Moon”?

Today I read an article about Saturn's moon Helene, and it was described as a "Trojan Moon" but no further explanation was given. It was difficult to even get any context about the term from the ...

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