Firstoff, in his general relativity Einstein showed that dimensions could bend, curve, and move. This is an experimentally proven fact. Dimensions can, and do, move.
In an earlier post we logically prove that the photon remains stationary in the fourth dimension:
According to Einstein & Bria...
After proving that the photon remains stationary in the fourth dimension, we must conclude that the fourth dimension is moving at c.
In an earlier post we logically prove that the photon remains stationary in the fourth dimension:
According to Einstein & Brian Greene, does the photon remain sta...
@JohnRennie Well, he's ready for our advanced class. Unless the poster is a native German speaker, the capitalization of abstraction is a powerful channel marker.
In order to get dark energy to dominate, wouldn't you first need another form of energy to push the expansion until dark energy could dominate? Otherwise I don't understand how the universe could shift from having a decelerating expansion to an accelerating expansion. Is there any analogy that co...
Currently, Dark energy (68.3%) and Dark matter (26.8%) together constitute about 95.1% total matter-energy content of the universe while only 4.9% is ordinary baryonic matter. Was this always the case? Are these ratios constant since the big bang or did they change over time?
anyone know how to show that $|G| = 12$ where $G$ is the group of rigid motions in $\mathbb{R}^3$ of a tetrahedron?it's not as easy as in $\mathbb{R}^2$ to show rotations and reflections..
is it like $r$ is the rotations clockwise of a face, then $a$ is the rotations of the faces? 4 different faces and 3 different rotations of each face so $4*3 = 12$?
@dmckee true but most forums work the same way. people get mad at you for reposting your thread when you could just bump them. i guess if they're new to forums in general it makes sense
@Obliv A "rigid body" is one in which each particle or mass element remains the same distance from all the others. Rigid motion is motion of a rigid body.
The chapter on the subject in a mechanics texts is generally about general rotational motion, because the translational part is pretty boring.
@dmckee I am told to show that the amount of rigid motions of a tetrahedron in $\mathbb{R}^3$ is only 12. So I need a more specific/constrained definition of rigid motion I think
well I found the solution here crazyproject.wordpress.com/2010/01/08/… it's just a matter of understanding what the notation means. I was thinking there was another way of writing this. Something I'm more familiar with.
@Obliv Oh well, I tried. I find myself disinclined to believe it's a great loss.
user54412
@JohnRennie You gave him far more leeway than I would have. Considering every other comment he makes begins by mentioning his PhD in physics and Ivy League education, it's pretty clear he's not a particularly intelligent troll.
To be fair it is a hard concept for beginners to SR. I wonder if we need a definitive canonical Q/A for it as the current duplicates are somewhat scattered.
@DanielSank there is a distinct odour of troll around Astrophysics Math.
It staggers me that people who have potential access to real physicists choose to reject their help. In my days as a teenage physics nerd (long before the Internet existed) I would have given my right arm for the sort of access the PSE offers.
Just noticed the existence of Beer, Wine & Spirits on the network. They are still feeling their way as yet. I wonder what kind of site it will mature into.
@JohnRennie The internet is the great Equalizer. Anyone can publish their meanest thoughts to the world at large with a click of a button. In your nerd days these people were mostly confined to their desk and whatever souls they could corner in the library.
I've heard that drinking beer lowers sexual desire and potency, and that's the physiological effect of hops.
Is it true? Does drinking a lot of beer have negative long-term effects on sexual desire or potency? Or is it just an urban myth, based on negative impacts of drinking too much?
@BernardMeurer remember yesterday when I pointed out that functions are vectors and then integration is a linear operation on functions? Don't forget that.
Brazilian education is very focused on getting you to see everything humanely possible, without really understanding most of those things; and that goes for all subjects
@AccidentalFourierTransform At least in College I'm hoping they won't expect me to know every single bloody philosopher that has ever existed on the face of this god forsaken land
@DanielSank Nope, we had 0 calculus at school. I picked it up by myself during my last year but I never used it so I just forgot it all except limits and derivatives
@BernardMeurer With the ideal of a "Liberal Education" (here liberal means wide-ranging rather than a political stance; though on many campuses that also applies) means they will expect you to dabble in a range of subjects, but you get to focus on your major field of study.
@BernardMeurer Yep. I'd encourage you to work the system so that you can take as many classes that interest you for general education (that's the dabbling) as possible.
The final project was a shoe box full of bones and our assignment was to write up a lab report on what we thought happened to the previous owners of said bones.
They tried to fool us by including bones from non-human animals.
@DanielSank Nice. I took "Human Origins" from Brian Fagan. Aad "The History of Technology". And "Great Moments in the History of Public Policy" and made each of them cover a different gen ed. Good times.
@BernardMeurer Hahaha, I don't remember. I just remember that he was somehow involved. I think I made the story pretty tame. I'm sensitive about murder and violence.
@BernardMeurer When I was at UCSB they had a sociology course entitles "Human Sexuality" that covered a couple of gen eds. It was the most popular course on campus and it wasn't the cakewalk that many expected it to be.