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Questions tagged [estimation]

A rough calculation or an approximation of the value, number, quantity, or extent of something so that it is usable for some purpose even if the input data may be incomplete or uncertain.

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How accurate does the ISS's velocity and altitude need to be to maintain orbit?

We know the the ISS is not drifting weightless in space, but rather is constantly falling as it circles the Earth. To do this it must be at a specific altitude and moving with a specific velocity. ...
foolishmuse's user avatar
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1 vote
1 answer
66 views

Boat floatation load [closed]

I was reading about boats, from what i was reading a qubic meter of air should be able to float a 1 ton boat so as far as i understand the equalibrium point will be if a boat wight is 1 ton - 1 qubic ...
Hitab's user avatar
  • 21
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0 answers
26 views

Is there an estimate for how many monopoles would be produced in the very early universe?

The question really hits it with this one. I haven't really found some good numbers other than the whole “It'd be so many (per Hubble vol) to recollapse the universe”. I don't know if that comes of as ...
Mike's user avatar
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0 answers
74 views

Does the Host Rock of This Mexican Hyalite Show Signs of Uranium Minerals? I Previously Cut It and Am Now Concerned

I previously cut a Hyalite specimen from Zacatecas, Mexico. Using a Geiger counter, I measured a slightly higher level of radioactivity on the cut surface compared to the environment. Although I know ...
Flame Gems's user avatar
6 votes
2 answers
292 views

Does life erode Earth's mass over time?

Since life converts matter to energy, and there's no natural process that does the opposite (aside from supernovas), does this mean that the mass of our planet is gradually diminishing? I asked ...
Lynx's user avatar
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5 votes
1 answer
458 views

Bound states between neutrinos using Schrödinger's equation?

I would like to see if it's possible that neutrinos (with sufficiently slow velocities) could form bound states in a universe with matter (such as ours) There is a cosmic neutrino background in the ...
vengaq's user avatar
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0 votes
1 answer
102 views

How many photons pass through us every second?

I just read this answer https://physics.stackexchange.com/a/229374, which says that, when a magnet rotates, photons are emitted with wavelength $λ=c/f$, where $f$ is the frequency of rotation. And ...
Flamethrower's user avatar
0 votes
0 answers
42 views

How can I find the distance between planet and black hole?

With the movie Interstellar how I can find time dilation of the Miller's planet? Do I need find the distance between the planet and the black hole? Then I can find the time dilation? If not, please ...
Enma isme's user avatar
0 votes
0 answers
69 views

Why can we use $|p| \approx\hbar /\langle x\rangle$ as an approximation?

In our lecture, the approximation for the zeeman energy shift is $$\frac{2e \vec{p} \vec{A}}{2m} \approx \frac{e \hbar B}{m}.$$ Here, symmetric gauge was used (therefore $A \approx r B$) and my ...
phein1's user avatar
  • 11
11 votes
2 answers
2k views

What percentage of light gets scattered by a mirror?

Sunlight strikes a mirror at a 45 degree angle. The vast majority of light will be reflected about the normal. Some light will be absorbed by the mirror. Some light will be transmitted through the ...
causative's user avatar
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6 votes
4 answers
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Accelerating Expansion of Universe - Why Not Caused by Radiation?

As I understand it, dark matter and dark energy are used as an 'explanation' for how universe expansion is accelerating; because without it gravity would be expected to cause a long term shrinking. ...
Claud's user avatar
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140 votes
2 answers
71k views

How many photons are received per bit transmitted from Voyager 1?

As of 2024, according to https://voyager.jpl.nasa.gov/ , Voyager 1 is around one light·day away from Earth and still in radio contact. When Voyager 1 sends messages to Earth, roughly how many photons ...
Craig Gidney's user avatar
  • 7,022
2 votes
1 answer
60 views

Acceleration at peak of a gravitational wave

The amplitude of the strongest gravitational wave signal detected by LIGO sofar can maybe be expressed as an acceleration? If so, what would the numerical value be (in m/s^2)? I would like to compare ...
Wouter M.'s user avatar
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0 votes
2 answers
67 views

Are these levels of RF radiation harmful?

I live on the top floor of a building that has four 5G antennas on the roof. The house is curved, and from my viewpoint, I can partially see one of the antennas pointing towards me. Curious about the ...
Armands L.'s user avatar
0 votes
2 answers
63 views

Will a nuclear blast just above the surface of an asteroid push it, or just heat it and maybe produce outgassing?

Will a nuclear blast just above the surface of an asteroid push/nudge it, or just heat it and maybe produce outgassing? In other words, would nukes be actually useful to deflect asteroids?
Mark Besser's user avatar
0 votes
1 answer
56 views

How long does it take to saturate the water vapor pressure in a small enclosed space?

I am trying to create an as much humid as possible small enclosed space (like a zip bag). If I leave more than required amount of water in the zip bag, how long does it roughly take to reach the ...
mete's user avatar
  • 101
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0 answers
54 views

Derivation of Compton wavelength in Tong's QFT notes

On page 2 of David Tong's notes on QFT: http://www.damtp.cam.ac.uk/user/tong/qft.html, he makes use of Heisenberg's uncertainty principle to describe relativistic effects for a particle of mass $m$ in ...
ratchet411's user avatar
0 votes
1 answer
54 views

The Darkening of the Sky During a Total Solar Eclipse

During a solar eclipse, the sky maintains a high brightness even when the Sun is, say, 95% eclipsed by the Moon. During the last ten seconds before totality is when most of the darkening of the sky ...
michaelc35's user avatar
15 votes
4 answers
8k views

If microwave ovens run at 2.4 GHz, what is the long-term effect on living tissue of exposure to this frequency, but with a thousand times less energy?

Very low power electromagnetic waves with a frequency of 2.4 GHz can't cook anything. That's obvious, despite the heating effect such radiation has on water. However, what if such an object containing ...
Mesijé vopřenej Vo zeď's user avatar
0 votes
0 answers
35 views

How long for boiling water to cool down in a cooler?

I have no knowledge in physics but I drink green tea, and it requires water at 70 degree (so does the package say). My boiler can only heat to 100 degrees (not below), so I would like to know how long ...
Victor's user avatar
  • 1
10 votes
3 answers
5k views

How much pressure would it take to compress a block of solid steel into one-tenth the original volume?

We all know to compress objects into smaller volumes, you would need to apply pressure to them. The required pressure depends on how strong the material is and which form is it (gas, liquid, solid). I ...
ZanMoon-chan's user avatar
0 votes
0 answers
48 views

It is possible to estimate the height of an explosion by its looks?

There's various social media postings (e.g. on reddit or on Twitter) saying this is what an exoatmospheric intercept (by an Arrow) missile looks like (I took 4 frames from the video, in case you don't ...
got trolled too much this week's user avatar
3 votes
3 answers
329 views

Comparison of clocks running at different heights in a gravitational field

I hope this question has not yet been asked. If so then please link me to the answer. If I build an apparatus which, on flicking a switch, sends a light beam, a distance to a mirror, and reflects it ...
Paul Hinrichsen's user avatar
10 votes
1 answer
1k views

What fraction of the universe's energy is contained in photons?

From each point in the universe, the light of billions of stars, galaxies, supernovae etc. can be detected. So there seems to be a lot of energy/momentum "in flight". Is it possible to ...
2080's user avatar
  • 347
0 votes
2 answers
118 views

Size of an atom

This may be a naive question, but today, while reading about the Rutherford experiment in my high school chemistry textbook, I came across the following sentence: "Calculations by Rutherford ...
tensorman666's user avatar
0 votes
0 answers
78 views

How strong of an MRI machine would be able to kill a person?

Previous title: How strong of a magnetic field could dissociate water molecules? (Changed as this is probably not possible) This is part of an attempt to answer the question 'How much MRI is enough to ...
upbeatmeeting's user avatar
1 vote
1 answer
112 views

How did Newton determine the average density of Earth is twice the density of the surface rocks? [closed]

I've read that Newton determined the average density of Earth is twice the density of the surface rocks, but I can't find his computation anywhere. I presume he used the differential calculus in some ...
lee pappas's user avatar
0 votes
1 answer
33 views

Measuring distances between the stars

If we know how far away are the two known stars from Earth, then is it a safe bet that we can know how far apart those two stars are from each other using sine rules? Does that mean we must first ...
user6760's user avatar
  • 13k
1 vote
1 answer
57 views

What is the amount of force applied on my back while I'm brushing teeth leaning forward?

This is a question I've had for several years but never had the knowledge to calculate myself. Please keep in mind I don't have much background in physics (learned some on middle school I guess...), ...
Yoda's user avatar
  • 11
4 votes
2 answers
2k views

How far can we go in space?

I'm a noob in physics & math, so I'm just looking for a scientific answer for a small fiction project. My question is : How far can we realistically go in space, if we managed to "use" ...
Django's user avatar
  • 51
1 vote
2 answers
118 views

Is it plausible that Earth's magnetism can induce heart attacks by affecting red blood cells? [closed]

https://ui.adsabs.harvard.edu/abs/2014cosp...40E1114G/abstract#%3A~%3Atext%3DIt%20was%20shown%20statistically%20that%2Ccomparison%20with%20quiet%20geomagnetic%20conditions This study says that on ...
Malcom's user avatar
  • 39
4 votes
2 answers
125 views

Temperature estimation based on very quick measurements

I want to preface by saying I'm not a physicist, I'm a hardware designer at an R&D center trying to wrap my head around temperature measurements, so please forgive me if my questions are stupid or ...
Iliyan Antov's user avatar
1 vote
2 answers
207 views

How to obtain the center of mass energy needed to form a black hole in a particle accelerator?

Once, Hawking has brushed aside the worries about LHC forming black holes massive enough to actually cause damage. I want to know which estimate he has used. After all, it is not possible to asign a ...
Confuse-ray30's user avatar
3 votes
3 answers
103 views

What's the limit on the length of string that can be pulled by a person? [closed]

Imagine it's pre-industrial times, and a king wants to keep control of his vast empire. One of the biggest problems was how slow it was to transmit information; it could take weeks to be notified of ...
Reuben Matthews's user avatar
0 votes
0 answers
95 views

How much time passes relative to the protons inside the LHC?

The time depends on the speed of movement. Protons in the LHC move at near-light speed. Therefore, they perceive a different time than the scientist who is observing them. My question is how much time ...
nilecrocodile's user avatar
0 votes
0 answers
49 views

Rocket Exhaust Ground Impact: Exhaust Gas Velocity vs. Pressure

Thanks for anyone that can help. Say we have a rocket engine in the vacuum of space with exhaust velocity of 2,000m/s or more, but low pressure exiting nozzle, say 1-2psi. A wider nozzle engineered ...
Nomadicus's user avatar
-6 votes
2 answers
112 views

Do people have an attractive force?

The definition of gravity is this from google: "the force that attracts a body toward the center of the earth, or toward any other physical body having mass." Ok what about the actual ...
user55665484375's user avatar
0 votes
0 answers
29 views

How does gas flow change with gas composition?

How does gas composition affect gas flow rate with all other parameters being constant? I am trying to calculate the flow rate of raw biogas with 63% CH4 and 37% CO2 relative to purified biogas with ...
Samuel Soroaster's user avatar
1 vote
1 answer
27 views

Do frame dragging affects falling object?

Imagine there is a tall tower erected at the equator, a pulse of light is beamed from the top of the tower to the ground. Do I need to consider frame dragging? After all the spacetime is being tucked ...
user6760's user avatar
  • 13k
0 votes
1 answer
86 views

What would be the Joule requirement to a railgun launch a conventional bullet at mach 7?

The railgun project from the US Naval Surface Warfare Center Dahlgren Division shoots a projectile of 3.2kg at a speed of mach 7 with 18.4 megajoules of energy. How many joules would a railgun need to ...
Fulano's user avatar
  • 277
0 votes
2 answers
83 views

Would be possible to cover all the deserts with solar plates and satisfy the demand of electricity?

if we covered all the deserts with solar plates , would that be the solution to the energy crisis ? i mean put a solar plates in ALL the deserts of the earth to harvest all solar power
Jose Perez's user avatar
0 votes
1 answer
45 views

Coriolis effect in the bathroom? [duplicate]

I understand that the Coriolis effect is not responsible for the spin effect in the bathroom, but I have never seen a rigorous math prof of this. Where could I find a proof of this? What references ...
eraldcoil's user avatar
  • 213
1 vote
0 answers
50 views

GRB 221009A Comparison with solar flare NOOA scale

I'm trying to found a comparison of the energy received on Earth by GRB 221009A in comparison of various solar flares based on NOAA Space Weather Scales (or other). I failed to find any comparison (...
Vincent ISOZ's user avatar
1 vote
0 answers
41 views

Can I guess the order of magnitude of the current inside a spark based on a picture?

In this video, Steve Mould explains how an inflammable gas can be ignited with a spark created by the piezoelectric effect. At 01:11, there is a close up on the spark with a scale in the background. ...
cjorssen's user avatar
1 vote
0 answers
48 views

How much radiation on the surface of the moon during a Coronal Mass Ejection (CME)?

I'm writing a book set on the moon. A Coronal Mass Ejection (CME) as large as the Carrington Event hits it. Three astronauts are caught out during an EVA. They will cover their rover in regolith to ...
L.R. Lam's user avatar
1 vote
1 answer
168 views

Does a geodesic exist that will take someone across the event horizon?

I saw the movie "Interstellar" a few years back, and was amazed that Cooper was able to fall from 1 AU into a black hole before his daughter turned 110. Intuitively, I would think that there ...
The Shepard's user avatar
9 votes
1 answer
1k views

Nuclear fission in the Sun

The Sun's energy comes primarily from fusion of light elements in its core. It is estimated that a very small fraction of mass of the Sun (~$10^{-12}$ times the abundance of hydrogen) is uranium (both ...
Johnsmith's user avatar
  • 133
0 votes
0 answers
30 views

Estimation of errors in actual experiments

I encountered a statement in a research paper I read which confused me- “In order to estimate the random error in our data, we calculated the average distance between a line of best fit and the ...
Akarsh Sahay's user avatar
1 vote
1 answer
104 views

At the TOV limit (almost black hole), how much of a neutron star's primordial mass has been converted to energy?

The following rough approximation seems to show a neutron star at its Tolman–Oppenheimer–Volkoff limit of 2.17 solar masses and 12km radius, has gravitational binding energy on the same order as its ...
James Bowery's user avatar
  • 1,357
0 votes
0 answers
68 views

How fast must an incompressible ball, with mass $M$ and radius $R$, rotate to form a black hole?

An incompressible sphere with a uniformly distributed mass $M$ and radius $R$ is rotating in empty space. How fast must the sphere rotate to form a black hole? Will this happen when the kinetic energy ...
Il Guercio's user avatar

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