Category Archives: science

Why Is Today Feb 29?

Over at the Bad Astronomy site, there is a very clear explanation why we have leap years. It has to do with the number of days in a year not being exactly 365 days, but about 365.25. Adding extra days over the years has an effect of syncing the calendar with actual physical years. (Remember that 1 day = one rotation of the Earth and 1 year = one orbit of the Earth around the Sun.)

The algorithm to determine if a year (in A.D., like 2008; for B.E., subtract 543 first) is a leap year is this: If the year is divisible by 400, it’s a leap year. If it’s not divisible by 400 but divisible by 100, it’s not a leap year. If it’s not divisible by 100 but divisible by 4, it’s a leap year. Other years are not a leap year.

Besides the article, the site is an excellent source of information about science and astronomy. A few of my favorite articles are Bad Movies, Apollo Moon Hoax, Coriolis Effect vs. Water Drain Direction (and here too), and Just Another Face in the Crowd.

I first heard of Bad Astronomy during my honeymoon. Aor and I went to Sydney, Australia for honeymoon. I, being a very romantic guy, went to visit Sydney bookstores with Aor in tow. I bought Phil Plait’s Bad Astronomy book and found it to be one of the best science books I read in (not so) recent years.

เว็บตารางธาตุดีที่สุดในโลก (หรือน่าจะดีที่สุดในระบบสุริยะด้วย)

ถ้าคุณอยากรู้เรื่องเกี่ยวกับธาตุต่างๆ คุณต้องไปดูที่ The Elements คุณจะเห็นรูป ประวัติ วิธีผลิต ตัวอย่างการใช้งาน ข้อมูลเกี่ยวข้อง การแปรธาตุ และอื่นๆ

ผู้สร้างคือ Theodore Gray ซี่งเป็นผู้ร่วมก่อตั้งบริษัทที่สร้าง Mathematica เขาบอกคร่าวๆว่าเขาใช้ Mathematica อย่างไรในการผลิตเว็บอันนี้ที่นี่

ยกตัวอย่างเช่นถ้าคุณจะผลิตไฮโดรเจนคุณก็สามารถดูวิธีทำได้ที่นี่ หรือที่หน้านี้คุณจะได้รู้ว่าคุณไม่สามารถถ่ายรูปไอของไอโอดีนบนพื้นหลังสีดำได้เนื่องจากไอจะไม่สะท้อนแสง

This is another resource for my homeschooling project.

Understand Classical Mechanics Precisely, Very Precisely

The excellent Nerd Wisdom website steered me toward a most unusual book about understand classical mechanics (Lagrangian and friends, see contents for details) precisely enough that computers can manipulate the expressions involved. Not numerical values, expressions.

I remember that when I learned about all these stuffs back in college, I was a master of symbol manipulation and automatically assumed or ignored details as necessary to arrive at the final solutions. Many of my friends had more trouble doing this since they were more precise thinkers and never got used to hand-waving arguments involved. This book would be a great boon to them. There’s no ambiguity left in the symbols if computers can understand them.

Young physicists in training might find this useful too.