Cap'n Refsmmat

You do realize that every cell in the human body contains the same DNA, right? (Apart from mutations and such, of course.) You don't need to use brain space to store information in DNA.

Mr. Friedmann is, understandably, somewhat annoyed by your decision to upload the entirety of his copyrighted work to Google Docs and share it on SFN. Thank you for switching the link to the Google Docs preview, which is substantially more legal.

When your browser requests avatars and user photos, the server tells it "you can safely use this copy for the next seven days," and so your browser doesn't bother loading it again until that time has elapsed. This means that your browser takes a while to notice when avatars change. You can force your browser to reload your avatar: http://www.refreshyourcache.com/en/cache/ It's not a server-side issue, so uploading your avatar again won't change it.

You can easily check for yourself that: [math]1.5^2 - 3(1.5) + 4 = 1.75[/math] so [math]x=1.5[/math] is not a solution. Instead, it seems your calculator is telling you the real part of the complex solution, which is: [math]x = \frac{1}{2}(3 \pm i \sqrt 7)[/math] where [math]i = \sqrt{-1}[/math].

At my university (University of Texas at Austin), undergraduate physics enrollment has gone up fairly dramatically in the past few years. Mostly it's been attributed to a marketing initiative undertaken by the department, which did things like open houses during new student orientation so students could discover that physics research isn't all about inclined planes and massless pulleys. We will have to see if the trend continues. I'd like to see physics gain recognition as more than just something for hopelessly academic types.

Sounds like a prediction to me.

That's the opposite of what the hypothesis is saying. Note that the hypothesis says "reduces the risk". You can't test this with one case. You can, however, test it with many cases, so you could say that "children raised on farms, on average, have..."

http://www.cplusplus.com/reference/clibrary/cstdlib/srand/

As I said, have you seeded the random number generator?

Is this C? Have you seeded the random number generator before using it? If you don't, it'll be seeded with the same value each time you run the program, and it will generate the same sequence of random numbers every time.

I'm not aware of a name, if there is one. http://farside.ph.utexas.edu/teaching/301/lectures/node87.html Well, we know that [math]p=mv[/math]. So: [math]\frac{dp}{dt} = \frac{d}{dt} mv = m \frac{d}{dt}v = ma[/math] Saying that this is equal to force is the definition of force, rather than a derived result. It's how we define what force is: it's something which causes a change in momentum or an acceleration. That's pretty much the definition of the center of gravity. To measure local acceleration due to gravity, one can use a gravimeter: https://en.wikipedia.org/wiki/Gravimeter

Yes. Of course, if she trusts Bob, and Bob says it's the correct message...

It's possible, but the point of cryptographic hash functions is that it is very, very difficult to generate a message that produces a given hash. That's called a preimage attack, and it basically requires brute-forcing it: try a bunch of messages until you get one which has the right hash. It takes a very, very long time.

.mov files aren't Flash but a QuickTime file format created by Apple. You can install QuickTime on Windows if you need to. .fla files should be portable, presuming you have Flash Professional, which is the program used to create Flash animations, not view them. XCF files are for static graphics, not animation. But I've not used GIMP on different systems, so I can't really answer about compatibility.

If the hash function is known publicly, can't the malicious interceptor just hash the altered message? I could easily intercept {m, h(m)} and replace it with {n, h(n)}, where n is my evil replacement message.

You're correct that it doesn't protect against replay attacks. But can an attacker manipulate the message without a replay attack, and still produce a valid hash? Think about that for a bit.

A prediction is just something you expect will happen if the statement is true. For example, here's a hypothesis: "Gravity pulls objects downwards with a uniform acceleration." Now, here's a prediction: "If I drop these two objects from the same height, they'll hit the ground at the same time." That's a prediction which would be true if they hypothesis is correct. It's how we test the hypothesis. You can take anything that would be true if the hypothesis is true and wouldn't be true otherwise. (So while "if I set this on fire, it will be hot" is true, it's not a prediction of my hypothesis, and it won't help me determine if the hypothesis is valid.) So for your example, you'd predict what would happen to children in different households.

Some file formats have facility for it, others don't. For example, the TIFF image format provides facility for adding data fields with whatever sorts of information you'd like. Other formats don't provide easy extension.

I find the conspiratorial tone here interesting, and I'm sure the chairman of our physics department -- a successful plasma physicist -- would be amused. Part of the point of fusion research is that you don't know what plasma behavior is important to study unless you try it.

This is much like the old "relativistic flashlight" idea, which I have a simulation of here: http://www.refsmmat.com/jsphys/relativity/relativity.html#flashlight (Works best on Firefox and Chrome. Press Next to switch to the reference frame of the observer, instead of that of the flashlight.) And yes, the time it takes for the light to reach the target is dependent on reference frame. From the perspective of observer A, the distance to the target is slightly shorter, and the photon is able to get there faster; from the perspective of observer B, A's clock is running slow.

These days, Java is very nearly as fast as C. I don't believe it's been formally standardized, though. Using C is a safe bet, though.

After whose hour? The observer on Earth will claim that the rocket's clock is running slowly. An observer on the rocket will claim that it is running at exactly the right speed. Watch the animation I posted.

No; an observer on the ground will see the rocket's clock as running slow. You can see this effect on light clocks in this online demonstration: http://www.refsmmat.com/jsphys/relativity/relativity.html#light-clock In the first version (hit Play to start), photons bounce back and forth at a known rate. When you press Next, you switch to the reference frame of the high-velocity observer; to him, the photons must travel on the diagonal, so the light clock takes longer to tick. An observer moving with the light clock will not notice this effect. (Note: the demonstration will work best in recent versions of Firefox and Chrome.)

Yes, an observer sitting on the rocket will see that the clock is ticking at exactly the frequency he'd expect if he were sitting on Earth and watching a stationary clock.

Or a printer which provides a slot for memory cards, or anything like that. I know when I plug in my printer I get a bunch of removable drives -- one for each memory card slot.