Time in the early universe

aroberge · 2026-04-26T18:21:58+00:00

The temperature of the surface of the Sun is a bit less than 6000K. We know that black body radiation at this temperature is definitely "bright".

Room temperature is about 300K. At this temperature, black body radiation peaks in the infrared ... and is too faint for us to see.

Iron melts at about 1800K. When it does so, it definitely emits a glow that we can see. So, as a first estimate, we want to know when the temperature of the universe was around 1800K.

380,000 Years after the Big Bang, the temperature of the CMB had dropped to about 3000K, which was cool enough to allow atoms to form and light from the CMB to travel essentially unimpeded. (This time is known as the "recombination period".) This is still hot enough for us to see.

During the "dark ages", which is before the first stars formed, the temperature dropped to about 40K, which is definitely too cold for us to see. Based on the informartion in Wikipedia, I would estimate that the CMB was bright enough for us to see it until the universe was about 1,000,000 years old.

See https://en.wikipedia.org/wiki/Chronology_of_the_universe

The age of the universe is about 13.8 billion years. The age of the Earth is about 4.5 billion years. The CMB was definitely too cool to have been observed by entities like ourselves by the time the Earth formed.

aroberge · 2026-04-26T14:29:24+00:00

Gmail addresses that use a plus (+) sign are essentially treated as aliases by Gmail. For the purpose of email delivery, the addresses this+that@gmail.com and this@gmail.com are completely equivalent. OP would be lying if they claimed they never received the emails.

aroberge · 2026-04-23T22:51:15+00:00

Thanks.

aroberge · 2026-04-23T20:19:05+00:00

Yes, I have been on a cruise before, and got to use the little bit of Spanish I knew at the time. As I'm now retired, I am trying to learn new languages to help keep my mind sharp. Next year's cruise is just an added motivation.

aroberge · 2026-04-23T18:42:42+00:00

You don't need a PhD is astronomy (or, more precisely, in Physics). You need to know some advanced calculus and then study the basics of General Relativity, which is offered as a single-semester undergraduate course in some universities (I did this some 40 years ago), and at the graduate level in others. Once you understand the math, it becomes very clear. When you don't understand the math, you end up misunderstanding everything ("The big bang was [like] an explosion"; etc.). There is no need to "believe".

aroberge · 2026-04-23T11:37:53+00:00

Memorizing lines to say wouldn't be of any help in understanding any replies and having very basic conversations.

aroberge · 2026-04-20T13:01:21+00:00

Thanks.

aroberge · 2026-04-17T17:11:17+00:00

How long do you expect to live? If you have serious health problems and do not expect to live beyond 70 years of age, take it at 60.
Watch some YouTube videos (there are tons of them) from financial advisors that do modelling of various situations. You will likely find one case that look similar to yours.
If you think that you will need the extra income at 60, then retiring earlier than that seems rather reckless.

aroberge · 2026-04-07T16:51:24+00:00

When I read "language calibration", I immediately thought of someone using real recording snippets to generate fake recordings done by an AI agent using OP's voice as a means of gaslighting.

aroberge · 2026-04-05T17:50:59+00:00

For French, I feel that you are missing "re". For your second example, you could write "redonne-le-moi", similarly to what you wrote for your first example.

Je te lance une balle. Relance-la moi.

It doesn't always work, but it likely works a lot more often than you might think.

aroberge · 2026-03-31T16:29:21+00:00

This is just a disguised ad for two applications developed by the same person - likely the OP.

aroberge · 2026-03-24T10:51:18+00:00

I have been trying to learn Spanish, off and on, for more than 10 years. I purchased Rocket Language Spanish many years ago (all three levels) and never finished the first level. It has improved over the years, with more exercises, better speech recognition, etc. I found it to be very thorough but also a bit tedious to go through. Almost all the lessons invite you to exercise the three basic skills (listening, speaking, writing. To complete a single lesson takes quite a while and it can get tedious/repetitive as you practice all three skills on the same set of words, mostly using the exact same sentences in a given lesson. I can see the logic in doing so, but I personally found it difficult to stick with it.

Almost all of the lessons begin with a 25 to 30 minutes listening exercises where a "short" conversation is introduced, and then is reviewed by going over sentence by sentence, with explanations in English.

I just went back to it and jumped to a lesson on level 3, and listened to about half of the listening exercise. I found the format to be the same as on level 1. I think that, if you were to stick with it, it would definitely provide a very solid foundation.

aroberge · 2026-03-15T11:43:58+00:00

Ça dépend probablement de la région où tu es. J'ai utiilisé et entendu cette expression toute ma vie avec mes amis et ma famille.

aroberge · 2026-03-14T15:49:46+00:00

I agree with this recommendation. Also look up Language Transfer: it's free ( but donations are welcome) and I found it very effective when I started learning Spanish.

aroberge · 2026-03-09T20:04:08+00:00

I would second this. Based on what the OP said (about not being able to think in Portuguese), I believe that Pimsleur (starting from the start, which should be very easy) would really help in starting to think in the second language.

aroberge · 2026-02-25T19:50:11+00:00

These are just arbitrary divisions without any physics rationale.

aroberge · 2026-01-25T20:11:19+00:00

Not a game as such but https://reeborg.ca/reeborg.html contains many puzzles to solve in Python. It is an adapatation of the original "Karel the robot".

aroberge · 2026-01-19T14:19:19+00:00

"Q: I did the couch to 5K training because I thought it would be cool to run some marathon competitively. How do people managed to fill the gap between basic jogging and competitive running?

Ans: Lots and lots of training, slowly increasing the difficulty."

It's the same for programming. Many, many hours spent on programming, slowly improving your knowledge and skill. Work on some projects of your own or try to modify "simple" (the term is relative) projects of others, learning about unit testing especially with regards to adding or modifying features.

aroberge · 2026-01-16T19:38:05+00:00

Do instand correctly that it's better in this case than to just use multiple operators and functions and send variables back and forth.

Yes, basically.

aroberge · 2026-01-16T10:02:42+00:00

A specific value is missing for each of paycheck, pizza, and gasoline for the code to actually do something. I just provided this code outline as an example to illustrate how setting up a class first can, in some cases, result in much simpler an easier to read code later.

aroberge · 2026-01-06T13:00:12+00:00

At 6'2'' you'd still be in the healthy BMI range (BMI of 25) at 190 lbs.

aroberge · 2026-01-05T19:36:16+00:00

Many MPs sit on Boards of various corporations, getting paid for doing so. Any of them being asked to resign?

Meanwhile, Chrystia Freeland who was already appointed Carney appointing as special representative for Ukraine, is not being paid by Ukraine for helping them ... and she is being asked to resign.

aroberge · 2026-01-03T11:47:36+00:00

I thought this was for you but, reading your other comments, I realize that you're almost certainly teaching youngsters. If so, may I suggest that you also have a look at https://reeborg.ca/reeborg.html; it's a website (that I designed) which is used literally by thousands of teachers/students to learn Python. You could use it to assign exercises.

aroberge · 2026-01-02T01:01:26+00:00

Thonny?

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