Questions tagged [order-of-magnitude]
The order-of-magnitude tag has no usage guidance.
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Order of magnitude of time derivatives of gravitational potential and gravitational vector potential on Earth
[This question is connected with this one. Since the estimation and measurement of spatial gradients and time derivatives have very different levels of difficulties, I thought it best to ask two ...
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Order of magnitude of gravitational vector potential & its gradient on Earth
In post-Newtonian approximation of gravitation, the metric on and around the Earth is taken to have the expression
$$
\begin{bmatrix}
-1+\frac{2}{c^2}U+ \frac{2}{c^4}(\psi-U^2) + \mathrm{O}(c^{-5})
&...
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Do people have an attractive force?
The definition of gravity is this from google:
"the force that attracts a body toward the center of the earth, or toward any other physical body having mass."
Ok what about the actual ...
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Order of magnitude of $v=\sqrt{q^2/Mr}$
I'm developing a problem and already found the solution, I know is correct to assume in my problem that the velocity of an electron is:
$$v=\sqrt{\frac{q^2}{Mr}},$$
where $q$ is the charge of the ...
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Is overusing gravitational slingshots a real concern?
I was thinking of the trading of kinetic energy during a gravitational slingshot maneuver and wondered if the kinetic energy lost during that process makes any noticeable impact on the orbit of the ...
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Why has it been so hard to come up with testable predictions for string theory? [closed]
String theory has yet to come up with any easily testable predictions despite decades of work.
Why is this? Why is it so difficult to come up with testable predictions for string theory?
Why is it ...
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What are the experimental difficulties in measuring the Unruh effect?
The Unruh effect was predicted in 1976.
As someone with no background in experimental physics I find it surprising this effect hasn't been measured yet. What are the experimental difficulties (and ...
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Can double copy address the weakness of gravity?
I hope I didn't miss a post that already answers this question. I am simply wondering if there is a natural framework in the double copy approach to explain the weakness of gravity? I don't require ...
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How can we determine the energy scale of a physics theory?
It is very common in physics, when we refer to the most diverse theories, on the most diverse length scales, we also refer to their energy scale. It is through the energy scale that we classify a ...
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“Massive” v.s. “Supermassive” black holes
I think I understand what a black hole is. When there is enough mass in a given area the “bend” in time space approaches infinite (please correct me if this is wrong).
I understand there are different ...
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What exactly is order of magnitude?
I am little bit confused with what order of magnitude is. In my book it says, when we write approximate values of quantities in powers of ten i.e $10^b$, then $10^b$ is the order of magnitude. But ...
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What does it mean that gravitation separated from the four forces at $10^{-36}$ seconds?
Physicists have used math to calculate that gravitation separated from the 4 forces at 10^-36 seconds after the big bang, which is even before the inflationary period. The universe was still smaller ...
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Is the exact definition of the Planck units important?
Wikipedia says there are other, possibly better ways to define the Planck Units based on whether we want to factor in or out a $2$ or a $\pi$ or a $4\pi$ as the case may be. Most of them represent ...
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Steady Couette flow where the moving wall suddenly stops
Let it be a planar Couette flow for an incompressible fluid with dynamic viscosity $\mu$ and density $\rho$ that has reached the steady-state. Assuming that the plates are placed at the $xz$ plane, ...
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Scaling difficulty of landing a rocket
I am wondering whether it is more difficult to land (as spaceX does) a rocket of height $k L$ than landing a rocket of height $L$? Is there some scaling law? Or at least is there a way to see in the ...
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