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Start with the ISS: https://spotthestation.nasa.gov/sightings/ it can be very bright (-5.9)--second only to the moon (at night, duh). Moreover, its angular diameter is on the order of that of Jupit …

Since you have "no idea" how to address this, it's good to start with the fundamentals and make some order-of-magnitude estimates and bounds. First is the sun's contribution. The sun's output is: $$ L …

Tidal friction is referring to the entire planet changing shape, not just the meager 1 TW of wind driven friction (https://earthobservatory.nasa.gov/images/654/dissipation-of-tidal-energy). The rotat …

If photons have mass, they travel at: $$ \frac {pc^2} E = \frac{\gamma m vc^2}{\gamma mc^2} = v$$ With $c=1$: $$ v = \frac p E = \frac p {\sqrt{p^2 + m^2}} $$ and with $\hbar=1$: $$\frac E p =\frac{\o …

So you'd have to use the Compton wavelength of the electron $\lambda_e = \frac 1 2 $ cm, and the Bohr radius is: $$a_0 = \frac{\alpha \lambda_e}{2\pi} \approx 11{\,}{\rm cm}$$ You could estimate the p …

A thousand years on earth would be a single (solar) day if the earthed had a sidereal rotation period of 0.999001 years.

Ultracold neutrons have velocities of a few to tens of meters per second and can be transported from source to experiment on ballistic trajectories (governed by gravity). (See the PF2 experiment at In …

As pointed out in the comments, the energy in the LHC is very high. High enough that the interactions are with partons inside the proton, where a parton is any one of the 3 valence quarks (u, u, d), o …

As technical answers appear, I'll just address the "imagine it" part. Tidal forces near black hole are similar to centrifugal forces on a spinning body. For a stellar mass black hole at 100 km, the ti …

The density of nuclear matter is on the order of $2 \times 10^{17}\, {\rm kg/m^3}$, while the Planck density--the density at which quantum gravity is "interesting"--is: $$\rho_P = \frac{m_P}{l^3_P}= \ …

This is a classic classical question that is designed to get us to understand how big Avogadro's number is. We know our lungs are much smaller then the atmosphere, but as $N_A \rightarrow \infty$, any …

This is mostly an engineering concern. Thanks to $\sigma T^4$, these hot things the size of a grapefruit lose energy quickly. The actual reactions producing the majority of the energy are over in well …

You're basically talking about the Earth going inside the Roche limit of the other body: the near side falls in faster than the rest of the planet (it's lifted into the sky), while the far side is flu …

So 5.5 Pg of neutrons is $3.3 \times 10^{39}$ neutrons. Their diameter is 1.75 fm--so end-to-end: 5.75 Ym.

The potential energy of a uniform sphere of charge $Q$ is: $$ U_Q = \frac 3 5 \frac 1 {4\pi\epsilon_0} \frac{Q^2}R $$ while the gravitational binding energy is: $$ U_G = -\frac 3 5 \frac{GM^2} R $$ (B …