1
Does Gravity Travel at the Speed of Light? (1998)
Updated 2011 by Steve Carlip, and 1998 by Steve Carlip, Matthew Wiener and Geoffrey Landis. Original by Steve Carlip.
John Baez
- Popular posts
- 10
- Total points
- 1,184
- HN comments
- 842
- Rank
- #1,731 personal
Visit math.ucr.edu → On Hacker News Nov 2008 – Mar 2025
Science & Space 7Math & Algorithms 5History & Retro Computing 1Design & UX 1
2
The Beauty of Roots (2011)
Around 2006, my friend Dan Christensen created a fascinating picture of all the roots of all polynomials of degree ≤ 5 with integer coefficients ranging from -4 to 4:
3
Can a Human See a Single Photon? (1996)
The human eye is very sensitive; but can we see a single photon? The answer is yes: sensors in the retina can respond to a single photon. But neural filters only allow a signal to pass to the brain to trigger a conscious response when at least about five to nine arrive within less than 100 ms. If we could consciously…
4
Why is C the symbol for the speed of light? (2004)
"As for c , that is the speed of light in vacuum, and if you ask why c , the answer is that it is the initial letter of celeritas , the Latin word meaning speed." Isaac Asimov in "C for Celeritas (1959)" [1]
5
Noether's Theorem in a Nutshell (2020)
Noether's theorem is an amazing result which lets physicists get conserved quantities from symmetries of the laws of nature. Time translation symmetry gives conservation of energy; space translation symmetry gives conservation of momentum; rotation symmetry gives conservation of angular momentum, and so on.
6
Is Faster-Than-Light Travel or Communication Possible? (1997)
It might be thought that special relativity provides a short negative answer to this question. In actual fact, there are many trivial ways in which things can be going faster than light (FTL) in a sense, and there may be other more genuine possibilities. On the other hand, there are also good reasons to believe that…
7
Beautiful plots of roots of polynomials
Click on the picture for bigger view. Roots of quadratic polynomials are in grey; roots of cubics are in cyan; roots of quartics are in red and roots of quintics are in black. The horizontal axis of symmetry is the real axis; the vertical axis of symmetry is the imaginary axis. The big hole in the middle is centered…
8
500 Exabytes per Raindrop
People like to say this is the "information age". But just how much information are we talking about? I recently found a nice source of... umm... information about this question:
9
Torsors (2010)
When you first read about "torsors", they're bound to seem a bit too darn sophisticated for their own good. Mostly this is because nobody explains them very well. So, I want to convince you that they're actually very simple and natural. I'll do this by giving you three examples from physics:
10
The Relativistic Rocket
Thanks to Alan R. Wilson for correcting a two-word typo involving GPS satellites. Thanks to Aron Yoffe for suggesting the newtonian comparison. Thanks to Tom Fuchs for suggesting the analogy to the stone thrown upwards. Fuel numbers added by Don Koks, 2004. Updated by Phil Gibbs, 1998. Thanks to Bill Woods for…