733 reputation
413
bio website
location
age
visits member for 4 years, 3 months
seen 12 hours ago

Feb
12
comment What happens before a radioactive element decays?
@RenéNyffenegger your best bet is to get used to the idea that "random" is scientific. It's a very precise kind of "random". Randomness can be highly scientific, and an entire branch of mathematics is dedicated to drawing accurate conclusions about "random" things.
Feb
2
comment Is there a small enough planet or asteroid you can orbit by jumping?
"though I wouldn't like approaching a planet with high speed" — but if you ran/jumped to start on your orbit, then that's how fast you'll touch back down, so it's not like you'll actually be moving at a very high speed upon touchdown. It's physically impossible to end up moving faster than that if the surface is a perfect sphere.
Feb
2
comment Why $F=ma$ and not $F=m\dot{a}$?
This could be asked about any law of our universe. Now, some of them can be derived from more general ones, but for now the best answer available is "because that's the formula that matches observation" and "we don't know what ultimately made our universe the way it is".
Aug
30
comment Can a human size object move so fast that it ceases to be observable?
@Jim What do you care whether we say "yes" or "no"? We all agree that the photons will be reflected and that they are observable. THAT is what matters here. Whether you call it a "yes" or a "no" is irrelevant. Some answers like to go beyond that and contemplate whether a human can spot these photons without specialized equipment, that's all.
Aug
30
comment Can a human size object move so fast that it ceases to be observable?
@Jim as long as we agree that you don't know that you see the filter, I don't mind whether it's called "visible" or "invisible"; that's a separate question. Although "observable" seems to be a more accurate term: a camouflaged sniper is definitely observable, and "invisible" doesn't seem appropriate despite being very hard to see, so I see your point.
Aug
29
revised Why aren't all rocks in space orbiting bigger rocks?
False info deleted: Rosetta does not literally orbit the asteroid, presumably because matching the speed to within 8cm per second is too hard at such a distance
Aug
28
awarded  Nice Answer
Aug
27
comment Can a human size object move so fast that it ceases to be observable?
@KyleKanos Fair enough. By your definition, moving fast or slow doesn't matter, obviously the same quantity of photons still get reflected. But I hope you can also see why others find the practical definition of "can a human actually see it" more interesting.
Aug
26
revised Can a human size object move so fast that it ceases to be observable?
added 5 characters in body
Aug
26
awarded  Yearling
Aug
26
revised How do electrons interact if one of them had just exited the two slits of the double-slit experiment?
added 4 characters in body
Aug
26
comment Can a human size object move so fast that it ceases to be observable?
Why do you define "blurred" as "able to see"? Ask the person doing the observation to list all the things they see. If they fail to list the blur, they didn't see it. Simple.
Aug
26
revised Can a human size object move so fast that it ceases to be observable?
added 543 characters in body
Aug
26
comment Can a human size object move so fast that it ceases to be observable?
@KyleKanos Define "invisible". If it's deadly yet someone tries to walk right through it, dying as a result, was it sufficiently invisible? How careful an observation is required to fail to detect the moving object before you would agree to call it "invisible"?
Aug
25
revised What is the closest general-relativistic equivalent of a “time slice”?
removed redundant example
Aug
23
answered Can a human size object move so fast that it ceases to be observable?
Aug
23
comment Can a human size object move so fast that it ceases to be observable?
@Jim you're lucky this is not Skeptics.SE, where claims such as that the brain dumps the light into images 30 times per second need to actually be supported by respectable sources.
Aug
20
comment Is “now” or “the present moment” properly defined in GR?
Somewhat related: what is the closest GR equivalent of a time slice?
Aug
10
comment Where am I confused about force addition?
Agreed with @BMS; easiest way to think about it. Now change the direction a little bit, bit by bit, and it won't seem so counter-intuitive that at 90°, you could still say that the forces kind of cancel out (though, more correctly, don't fully add up).
Aug
7
revised Why aren't all rocks in space orbiting bigger rocks?
added 268 characters in body