Laser pointer and a low-friction surface and a cat.
Best Depiction of Equivalence Principle: Inception.
A quick recap: Acceleration is motion in which either an object’s speed or direction (that is, its velocity) changes. Mathematically, acceleration and gravity are equivalent, just like energy and mass. If you’re riding in the elevator and someone cuts the cable, you’ll go into free fall. It will feel as if you were weightless as you float inside the elevator. Since both you and the elevator are falling at the same rate, you won’t be able to feel gravity’s pull. So from your limited perspective, you might conclude (erroneously) that gravity had inexplicably disappeared. The reverse happens when you accelerate in a car: you feel a force pushing you into you seat. If you can feel gravity’s influence, you can conclude that he is accelerating. And that apparent weightlessness is what’s depicted in this amazing scene — set in an elevator, natch! — in Inception
Perhaps Anti-Tyson is a little harsh, but soon after I see a great discussion by Neil deGrasse Tyson on science being driven by passion and curiosity, I read some blather from someone who’s basically pissed off that a physicist wrote something other than a physics textbook. Speculating on the metaphysical implications of science isn’t my particular cup of tea, but it’s not up to me to tell others that they can’t engage in it — as long as they don’t think they’re doing science. One never knows what speculation might spark an actual scientific advance, or when one might recognize that there is an actual falsifiable scientific principle embedded in one of those thoughts. (Leo Szilard is said to have come up with the idea of the fission chain reaction by seeing a traffic light change. Who the hell knows where inspiration comes from?)
I think it’s worth noting that John Horgan is the author of The End of Science, which I believe is the book (and concept) that Tyson was blasting in the interview as being shortsighted.
Is theorizing about parallel universes as immoral as betting on derivatives based on subprime mortgages? I wouldn’t go that far. Nor do I think all scientists should be seeking cures for cancer, more efficient solar cells or other potential boons to humanity. But scientists should, at the very least, investigate the world in which we live rather than worlds that exist—as far as we will ever know—only in their imaginations.
Now, I haven’t read the book, and I can’t say for sure how it is presented. If it’s being misrepresented as actual physics, then Greene is in error. But that doesn’t seem to be the complaint. Horgan knows its speculation, because he identifies it as such. His objection appears to be that a physicist was doing something that’s not physics! How dare he do that! If a physicist wants to write a book about metaphysics, or poetry, or whatever, who the hell is John Horgan to tell him/her otherwise, or to say what we do with our (free) time?
Here’s how explain xkcd works.
1) We post the cartoon on Monday, Wednesday and Fridays with our attempt to explain what is going on in the cartoon.
2) You comment on the cartoon and explanation and tell us what we have missed.
3) Others vote up or down your comment to help us pick out the best explanation.
xkcd is funny as hell (which is an odd saying; I imagine hell isn’t all that funny which makes this a pretty low hurdle, or so one might think) but can be quite obscure if you aren’t “in” on the topic of a particular cartoon.
h/t to J
There seem to be a lot of physicists, however, who believe they know everything there is to know about biology (it’s a minor subdivision of physics, don’t you know), and will blithely say the most awesomely stupid things about it. Here, for instance, is Michio Kaku simply babbling in reply to a question about evolution, and getting everything wrong. It’s painful to watch.
Kaku’s tendency to bather via an orifice other than his mouth has been noted more than once in the blogohedron, and he doesn’t even need to leave the field of physics to do it. The question here is why PZ thinks that he is representative of physicists? How does he get from one to a lot of physicists?
The question is why does Michio Kaku, who happens to be a physicist, think he is a master of all science. Leave the rest of us out of it.
There are an estimated 6 million calories in an elephant – enough energy to keep a human sated for over eight years. But at the Tsavo West National Park in Kenya, it took wild animals just seven days to reduce a dead elephant to nothing more than a pile of bones
As of writing this I have watched only the second half, which is linked in the link, to see the part about how the desire to improve life isn’t what drives basic science, it’s a byproduct. Scientists generally aren’t looking that far ahead, even if they could. You’re driven by curiosity which is aimed at the problem in front of you. Others can (and do) take discoveries and apply them.
I liked the “utility belt of understanding” metaphor, and since it’s Neil deGrasse Tyson, there’s a lot of good stuff (except for the part where he’s confusing Millikan with Michelson)