The Academics Thread

[Pariah]

2 hours ago, Cancer said:

Me, I want to reply with a link to a video clip of some insane sadist killing people with a cordless drill....

 

Trepanning for the win! 

[Old Man]

4 hours ago, Bazza said:

All the world is staged, 
and freedom, truth, and peace

are it’s casualties.

 

*its

[L. Marcus]

Whose on first base?

[Old Man]

Dude.

[Pariah]

No, Who's on first base.

[Bazza]

1 hour ago, Old Man said:

 

*its

i blame autocorrect 

[Old Man]

2 hours ago, Bazza said:

i blame autocorrect 

You know, autocorrect does that to me too and it pisses me off when it does. 

[Bazza]

Autocorrect (in)corrects lots of things it should leave alone. (tempted to misspell every word just written as an Autocorrect autocorrect). 

[Pariah]

Autocorrect can be turned off, you know.

 

(But if I do that, then I'm left with my own typing, which will almost certainly produce more errors. It's a lose-lose proposition.)

[Ternaugh]

Autocorrect on my current phone is atrocious. It will actively fight for the wrong word, and keeps on wanting to revert back to emojis as its default autocomplete state.

 

On my previous phone, the autocorrect was oddly helpful with word and phrase suggestions. I had started typing, "Let me see if",  and the phone suggested, one word at a time, "poodles can fly".

 

 

[Pariah]

Well, with sufficient initial thrust....

[L. Marcus]

Heh heh, thrust ...

[Logan D. Hurricanes]

MIT, here we come!

 

[Old Man]

[Bazza]

It’s science as it it is empirical testing of a hypothesis. It is also stupid. 

[L. Marcus]

"The difference between science and messing around is writing things down."

[Cancer]

I make my students roll dice, flip coins, watch the moon, and peer through spectroscopes in the dark.  I don't ask that they jump off buildings.

[Logan D. Hurricanes]

That's called taking initiative!

 

[Starlord]

44 minutes ago, Cancer said:

I make my students roll dice, flip coins, watch the moon, and peer through spectroscopes in the dark.  I don't ask that they jump off buildings.

 

No time like the present!

[L. Marcus]

No-Time Toulouse!

[Bazza]

How do you measure the immeasurable? 

[Cancer]

That's sort of what observational cosmologists have been doing for the last hundred years or so.

[Bazza]

may I ask, how? 

[Bazza]

10 of Today’s Most Influential Mathematicians
https://olmayanaergi.medium.com/10-of-todays-most-influential-mathematicians-af3372fb5ea

[Cancer]

1 hour ago, Bazza said:

may I ask, how? 

 

Yeesh, it's like most observational sciences: study what you can with the means at hand, and when patterns appear in your measurements let those guide you towards deeper investigation.  When you are starting from nearly nothing in terms of concrete, backed-by-evidence concepts, anything helps.  When you don't have a good understanding of your target, you collect measurements of just about anything of your subject.  To have begun with a preferred theoretical model in such circumstances probably would have been the opposite of helpful.  Even the Greeks knew that the simplest grand concepts of cosmology produced grossly bad predictions of how the universe ought to appear: this is Olbers's Paradox, where the simplest sort of model predicts that the entire sky should be as bright as the disk of the Sun, which is obviously wrong.  But through history up into the mid-to-late 19th Century there was no clue as to where the problems lay among the assumptions going into the paradox.

 

For a long time, the observers and experimentalists were different from the theoreticians.  Both sides were at least somewhat aware of the others' work, but the people doing the observations were not personally invested in the ultimate theories; and the theoreticians often did not have their finger on the limitations of possible observables or experimental tricks.  In the early Universe theory discipline, the two groups have drawn closer together (at least it appears that way to the outsider), but it is still true that people working on the forefront of theory are different from those who are making cutting-edge observations that test the theories.

 

That is considered healthy: the people making measurements have no stake in the models they are testing.  There is no temptation, even subconsciously, to fudge the data to fit your preconceptions better, in that arrangement.

 

As a science, cosmology got going in the 20th Century.

 

Einstein formulated field equations to describe the response of the Universe to the gravity made by more or less uniform distributions of matter, and he and others working with those equations found no static solutions, unless you add in an ad hoc constant to keep things static.  The only natural solutions to those field equations had either a uniformly expanding universe or a uniformly collapsing one.  Initially, you sort of shrugged at that for lack of data.

 

Slipher and Hubble took spectra of the galaxies because they had a new and unmatched new instrument to do so, the just-completed Mt Wilson 100-inch reflector.  The Doppler shifts in those spectra were larger for galaxies more distant (and Hubble's means of judging distance were crude and he knew it and admitted it, but he had no alternative), other than a very few nearby ones.  Preliminary conclusion: the simple result from Einstein's field equations has something going for it, because the Universe is expanding; because among simple geometric ideas, only that can produce that further<--> faster recession result Hubble found.

 

Then you press on: try to find better ways to assess distances, do population statistics for the galaxies, observe that galaxies come in groups and clusters and that there is a baffling variety of types and sizes but that variety seems uncorrelated with position in the sky, other than some correlations with how numerous the clusters were.  In the 1940s another unprecedented instrument was completed, the 48-inch Schmidt telescope, and it mapped the entire sky that could be observed from southern California.  Our own galaxy gets in the way, but thousands of galaxy clusters can be found in a systematic way from that uniform data set.

 

After WW2, other wavebands open up: radio telescopes see a sky that bears very little resemblance to the one seen by optical telescopes, but correlating the contents of the two panoramas is hard because early radio telescopes had MUCH poorer angular resolution than even the unaided eye has; some stuff is clearly interstellar gas, but other stuff isn't.  In the 1960s two breakthroughs come; in the first, Cyril Hazard and John Bolton use timings of lunar occultations of a bright radio source to isolate the position of that source to high precision, so that Martin Schmidt and others could point the 200-inch telescope at it and find a pointlike visible source accompanied by a faint streak, and the pointlike source had an enormous Dopper shift indicating it was very distant.  In the second, Robert Wilson and Arno Penzias were working on microwave telescope technology and found a uniform microwave glow around the entire sky; this had been predicted in 1948 by Alpher and Gamow in a model for a hot "big bang" model for the Universe (and a hint of it was found in interstellar gas, and commented on by Gerhard Herzberg in his textbook of the early 1950s, but he did not recognize it for what it was), and brought back to everyone's attention in the '60's by Dicke and Zel'dovich. 

 

The microwave background at a stroke compels you hot Big Bang models, and those make a strong link between the origin and evolution of the Universe and the fundamental forces as studied in the nuclear and particle physics; the proportions of the light nuclei (the isotopes of hydrogen, helium, lithium) in the oldest, most pristine matter we could find were sought after and found to be generally consistent with those models (see Weinberg's The First Three Minutes about this).

 

The first gravitational lensing features to be observed were found in the late 1980s, when a drastic improvement in detector technology (the availability of decent quality large CCD arrays) brought them into the regime of observable phenomena.  After a few heady months of WinTActualF reactions at seeing these strange coherent arc features seemingly stretching across impossibly enormous intergalactic distances, these were shown to be not physical objects but distorted images wrought by gravity, another prediction of Einstein's, and opening peepholes into very ancient situations where a foreground cluster fortuitously lensed much more distant galaxies, funneling light into images that could be observed from the ground despite the light's sources being much too distance to observe without that external gathering.

 

Since then, better technology in detectors, telescopes, spacecraft have allowed all these lines of inquiry to continue with exponentially increasing detail.  In general, the conclusions make for a coherent picture of the Universe and its evolution based on an inflationary, hot Big Bang model.  It cannot, of course, see all the away back to time zero; and there are unexplained bits, some disagreements between observations and models that are not yet understood ... this is way of all sciences (there are always things you don't understand as well as you would like).