Recent content by LastScattered1090

What is meant by time is "cosmic time" i.e. proper time measured by observers who are co-moving with the expansion, but who are otherwise not moving "through" space (in co-moving coordinates). We imagine their clocks all having been synchronized at cosmic time t = 0: the beginning of the...

Lagrange Points are specific to a two-body gravitationally-interacting system. So I guess the question is: which Lagrange points are you referring to? If you are thinking of Earth-Sun Lagrange points, then yeah, maybe you could start to build up through interferometry an aperture approaching the...

@SherLOCKed I guess one thing that confuses me is why there is a summation over 2ℓ + 1 in this case. That would make sense whenever averaging over all the m modes within a given multipole ℓ. But Cℓ is the same for every m mode at a given ℓ by assumption of statistical isotropy. So summing over m...

I guess this is off topic, but yeah by the old definitions based on powers of 2, computer storage sellers were indeed being dishonest, because every MB they sold you was 1 million bytes and not 10242 bytes. But once k and M prefixes in computing were redefined as powers of 10 to be consistent...

What everyone has said so far is accurate. I'd just further clarify that in this context, a "day" is defined as precisely 86,400 (=60*60*24) SI seconds, according to the International Astronomical Union: https://www.iau.org/public/themes/measuring/ So a Julian Year is 365.25 of those days...

Yeah and another point (that I didn't see being made above, but maybe it was), is that this quantity is not even constrained to be positive, so the direction of the force can change from mutual attraction to mutual repulsion depending on the charges involved. Hard to get Keplerian orbits with a...

Yeah! As I was reading, I was wondering why so many hoops were being jumped through to determine the tangential acceleration when it's basically given in the problem (vt(t) is given to be a linear function)

Doesn't that suggest that, given your assumed stiffness/spring constant, the mass will come to a stop in much less than one second? Can you think of ways to apply the equations for a spring to figure out what the stopping time would be?

@thementalist123 Yeah this is a badly-phrased question, but your attempt is also confusing. Even if you don't use LaTeX, can you at least put each step on a separate line so that we know what you're doing? In the thin lens equation, u and v are one of each of the following: image distance...

@Zeusex This seems like a poorly-written problem with insufficient information to me. There's no mention of 5% stretch in the problem, yet you assume this in your solution. Are you sure this is the full text of the problem? What is the significance of "after 20 m"? Rotating uncontrollably...

No problem, glad to be of help! :)

For your problem, it seems that candela (lumens per unit of solid angle) are largely irrelevant to your problem. If a source is isotropic, meaning equally bright in all directions, then the number of candela will just be equal to the total number of lumens divided by 4pi steradians, which is the...

The assumption that every sightline should terminate on a luminous object is indeed based on the premise of a static Universe of infinite age, not just infinite spatial extent. With non-static Universe of finite age, two things make this assumption untrue Finite age combined with finite speed...

This is a really good point. I encountered this when working with lead-acid batteries for a suborbital experiment; I am not sure if it applies to alkaline cells. But for lead-acids, the battery capacity rating (in A*h) from the manufacturer only applies at one specific assumed/nominal discharge...

My best guess is non-negligible series resistance in the circuit, even when R = 0.