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seen Dec 17 at 4:57

Aug
11
comment Do all black holes have a singularity?
@Jerry Schirmer. My error.. I meant "the event-horizon for a blackhole of equivlent mass", not the event horizon itself.
Jun
27
comment on what fundamental force is a black hole based on?
I think gravity is the inward force but what is the outward force that keeps it from collapsing to a singularity? (some theories say that the singularity does not exist)
May
5
comment Would we feel the rotation of a rotating habitat?
I should add that he only have his senses to rely on.
Apr
5
comment Can a neutron star compress until it's converted to a black hole?
is it a coincidence that degeneracy pressure of neutron stars is enough to keep it outside the Schwarzschild radius?
Apr
2
comment Can we prove that the universe is finite or infinite?
not necessarily. the universe could be a fractal. en.m.wikipedia.org/wiki/Olbers'_paradox
Mar
19
comment Given that matter cannot escape a black hole, how did the big bang produce the universe we see today?
wouldn't energy also attract itself due to gravity even if there was no matter in the beginning?
Jan
13
comment Is there a way to create an artificial solar eclipse?
"it would take an object the size of the moon to totally block out its light" is not entirely true. At the distance of the moon, it would indeed take an object the moons size. At half the distance, it would take half the size object (in diameter). If the blocking object is extremely close to the earth's surface, It would need to be much smaller. A large dense cloud can often block the sun completely. However atmosphere scattering would probably not make it completely dark.
Nov
16
comment Is the CMB rest frame special? where does it come from?
Actually, the answer is to "where the photons come from", and not "where does the rest frame come from"?
Oct
11
comment What makes us think we can actually detect gravitational waves?
I think the trampoline argument may not be 100% accurate. In that, we are travelling on the wave, while in the question, the wave goes through the car as well. In the trampoline example, the car itself would be distorted as per the distortion of the trampoline.
Sep
27
comment Are there planets that do not rotate on their axis?
@Zassounotsukushi: I gather from this article that even for rotation, the sum of all background motion causes the illusion of an absolute frame without any fictious forces.
Sep
27
comment How long does it take to travel 36 light years with tolerable acceleration and deceleration?
@FlorinAndrei: It gets shorter relative to earth but for the rocket and the people inside, everything will be just fine. They have other things to worry about though, for instance, to avoid being turned into cosmic goo by near-light speed protons hitting them on the way.
Sep
27
comment Are there planets that do not rotate on their axis?
@Zassounotsukushi: Angular velocity and angular momemtum are still measured w.r.t. a frame of reference. Even intrinsic angular momentum depends on the frame of reference. Correct me if I am mistaken.
Sep
27
comment Are there planets that do not rotate on their axis?
@Zassounotsukushi: I think it is incorrect to say that rotation does not require a frame of reference. It does, otherwise, you are implicitly assuming an absolute reference frame (i.e., aether).
Sep
17
comment Are there planets that do not rotate on their axis?
I still don't understand what it means for something to "not rotate". Nor rotate relative to what frame of reference? The stars in the background are actually moving.
Sep
15
comment Why do we always see the same side of the Moon?
I made an error above. Only if we stay on the line passing thru the centres of earth and moon do we really see the same side.
Sep
15
comment Why do we always see the same side of the Moon?
Technically, we don't always see the same side of the moon. It depends on the location on earth we observe from. However, from the same point on earth, we do see the same side of the moon.
Sep
14
comment If the Earth didn't rotate, how would a Foucault pendulum work?
'Didn't rotate' relative to what frame of reference? Tidally locked with the sun is one possibility, as is the possibility that it does not rotate w.r.t the milky way centre, or maybe you mean a particular galactic cluster? Even the distant stars and galaxies are moving, so there seems to be no "universal stationary frame of reference".
Sep
13
comment What can the D-Wave quantum computer do?
@joe Fitzsimons: true. My bad. I meant NP. Though, the first part of the claim is not entirely wrong. NP complete is part of NP.
Sep
12
comment What can the D-Wave quantum computer do?
If it can solve one NP complete problem then it should be able to solve any NP complete problem, including factoring. I highly doubt it can solve an NP complete problem though.
Sep
8
comment What is Energy made of?
How can matter be converted to trait of matter? Can a person be converted to age? It just does not make sense. Energy must be made of something. Or else mass itself is not made of anything.