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by Hypnosifl
Wed Apr 05, 2017 1:36 am UTC
Forum: Science
Topic: Miscellaneous Science Questions
Replies: 2910
Views: 683154

Re: RELATIVITY QUESTIONS! (and other common queries)

The relativistic Doppler effect and it's equation are just the straightforward combination of the concepts/equations of the Doppler effect and time dilation. If you derive it in an inertial frame, sure. But all the terms of Doppler equation can be understood in terms of local measurements which don...
by Hypnosifl
Sun Apr 02, 2017 12:22 am UTC
Forum: Science
Topic: Miscellaneous Science Questions
Replies: 2910
Views: 683154

Re: RELATIVITY QUESTIONS! (and other common queries)

Quizatzhaderac wrote:I think Eebster meant that the Doppler shift isn't a relativistic effect.

There is a non-relativistic Doppler effect, but the relativistic version obeys a different equation, so I think a Doppler shift obeying that equation would count as a "relativistic effect".
by Hypnosifl
Thu Mar 30, 2017 6:35 am UTC
Forum: Science
Topic: Miscellaneous Science Questions
Replies: 2910
Views: 683154

Re: RELATIVITY QUESTIONS! (and other common queries)

The important difference is that the observer on Earth knows there will be a Doppler shift and can correct for it. But there is no "correcting for" time dilation, because it is correct. In what sense is the Doppler shifted rate less correct than the time dilated rate? After all, there is ...
by Hypnosifl
Wed Mar 29, 2017 4:18 am UTC
Forum: Science
Topic: Miscellaneous Science Questions
Replies: 2910
Views: 683154

Re: RELATIVITY QUESTIONS! (and other common queries)

And remember there's also a Doppler shift depending on whether the traveling twin is moving toward or away from the stationary one. Yes, as gmalivuk says, due to the doppler effect, the rate at which a transmitter moving relative to you will seem sped up (if it is moving towards you) or slowed down...
by Hypnosifl
Mon Mar 27, 2017 4:29 am UTC
Forum: Science
Topic: Walking on a neutronium Dyson Sphere
Replies: 15
Views: 5443

Re: Walking on a neutronium Dyson Sphere

It's been hypothesized by physicists that there might be a possible type of nucleonic matter, called "strange matter", which could exist stably without the need for enormous external pressures as in neutron stars. I posted some stuff on this on the worldbuilding stack exchange website--see...
by Hypnosifl
Tue Aug 02, 2016 12:42 am UTC
Forum: Science
Topic: Is the Hyperloop remotely possible?
Replies: 62
Views: 8912

Re: Is the Hyperloop remotely possible?

A minor leak is not the issue, a catastrophic failure is the issue, i.e. a gaping hole in the tube. Mechanical brakes are useless here, they still have to withstand the shockwave. Imagine a fifty mile blowgun with a constant 300 kilonewton force blowing into it. Saying "we're aware of the prob...
by Hypnosifl
Mon Jun 13, 2016 1:20 am UTC
Forum: Science
Topic: Reversing entropy with unlimited energy
Replies: 9
Views: 3817

Re: Reversing entropy with unlimited energy

The context for the discussion was the idea that since energy is not conserved in an expanding universe you could get effectively limitless amounts of energy by tying one end of a thousands of light-years long rope to a dynamo and the other end to some far away star (we're ignoring some minor engin...
by Hypnosifl
Sat Jun 11, 2016 6:21 pm UTC
Forum: Science
Topic: Stable Orbits inside a black hole?
Replies: 5
Views: 2723

Re: Stable Orbits inside a black hole?

Also note that the singularity of an ideal rotating black hole is a "spacelike singularity" rather than a "timelike singularity", so once inside the inner horizon it would appear as physical ring sitting in space rather than simply being part of everyone's inevitable future (for ...
by Hypnosifl
Thu May 19, 2016 9:39 pm UTC
Forum: Science
Topic: Miscellaneous Science Questions
Replies: 2910
Views: 683154

Re: RELATIVITY QUESTIONS! (and other common queries)

Define "almost". As close to Born-rigid as possible without creating Ehtenfest's paradox when it rotates. Maybe he means relatively far away from a relatively light body, like, I dunno, a few meters away from the surface of the sun? That is what I meant. If you're talking about a region w...
by Hypnosifl
Mon May 16, 2016 6:16 pm UTC
Forum: Science
Topic: Miscellaneous Science Questions
Replies: 2910
Views: 683154

Re: RELATIVITY QUESTIONS! (and other common queries)

Not sure I understand the question. The reference frame is a specific event at a specific velocity. That's where and when you make the measurement. You measure the geodesic distance. It has to be symmetrical . . . In special relativity, simply specifying an object's velocity as its worldline passes...
by Hypnosifl
Thu May 12, 2016 9:40 pm UTC
Forum: Science
Topic: Miscellaneous Science Questions
Replies: 2910
Views: 683154

Re: RELATIVITY QUESTIONS! (and other common queries)

Isn't "1 meter apart" well-defined as the distance at which a light roundtrip takes 2/c? In special relativity, that definition would only make sense if the light emitter and the light reflector are at rest relative to each other, right? And in general relativity I think there's no coordi...
by Hypnosifl
Fri May 06, 2016 12:02 am UTC
Forum: Science
Topic: Can you (passively) heat an object hotter than your source?
Replies: 98
Views: 24905

Re: Can you (passively) heat an object hotter than your source?

But in a conventional sense, it will be in thermal equilibrium; the surface of the sun will be thousands of degrees, the laser will be at (say) 80C or whatever, and the object will be tens of thousands of degrees, and everything will be stable. Sure, the heat from the laser, will be radiating to fr...
by Hypnosifl
Tue May 03, 2016 7:57 pm UTC
Forum: Science
Topic: Can you (passively) heat an object hotter than your source?
Replies: 98
Views: 24905

Re: Can you (passively) heat an object hotter than your source?

I mean yeah that's the same as the first thing I said. Well, your first comment said "properties of the pump (in this case the sun) will be changing as time goes on. In particular it will eventually use up all of its nuclear fuel", so I was making the point that if you start with the pump...
by Hypnosifl
Tue May 03, 2016 2:44 pm UTC
Forum: Science
Topic: Can you (passively) heat an object hotter than your source?
Replies: 98
Views: 24905

Re: Can you (passively) heat an object hotter than your source?

Another situation is as follows: Imagine you have some magical thing which will stay temperature T forever. Now put it in your big mirror sphere with a laser and target. The pump will pump the laser and the laser will have a population inversion and shine laser light onto the target. This will be t...
by Hypnosifl
Mon May 02, 2016 4:49 pm UTC
Forum: Science
Topic: Can you (passively) heat an object hotter than your source?
Replies: 98
Views: 24905

Re: Can you (passively) heat an object hotter than your source?

Gotcha, I misunderstood what you meant by "steady state".
by Hypnosifl
Mon May 02, 2016 3:42 pm UTC
Forum: Science
Topic: Can you (passively) heat an object hotter than your source?
Replies: 98
Views: 24905

Re: Can you (passively) heat an object hotter than your source?

My point was as follows: a laser pumped by say a blackbody will not be in thermal equilibrium. The black body will be at some finite positive temperature. In steady state the laser will be a finite NEGATIVE temperature. The fact there is a temperature difference means that BY DEFINITION OF THERMAL ...
by Hypnosifl
Mon May 02, 2016 3:40 am UTC
Forum: Science
Topic: Can you (passively) heat an object hotter than your source?
Replies: 98
Views: 24905

Re: Can you (passively) heat an object hotter than your source?

^ this is absolute, total bullshit, continuous wave lasers you just shine pumping light in the side and continuous laser light comes out one end. :roll: But do you think they would continue to do this if the laser was at a uniform internal temperature before (or while) the pumping light hit the sid...
by Hypnosifl
Sun May 01, 2016 8:29 pm UTC
Forum: Science
Topic: Can you (passively) heat an object hotter than your source?
Replies: 98
Views: 24905

Re: Can you (passively) heat an object hotter than your source?

TLDR: lasers are always out of equilibrium. You can't insist upon a system where a laser is lasing and the whole system is in thermal equilibrium. Thanks for the explanation. As for the question about my overarching point, I was just using a simple thermodynamic thought-experiment to try to show th...
by Hypnosifl
Tue Apr 26, 2016 11:52 pm UTC
Forum: Science
Topic: Can you (passively) heat an object hotter than your source?
Replies: 98
Views: 24905

Re: Can you (passively) heat an object hotter than your source?

Yes, you've answered a totally different question, and one in which the answer is that there's never, ever, any heat flow under any circumstances; and one where you can draw no conclusions with respect to the original question, nor with respect to lasers. Why do you think you can draw no conclusion...
by Hypnosifl
Tue Apr 26, 2016 3:53 am UTC
Forum: Science
Topic: Can you (passively) heat an object hotter than your source?
Replies: 98
Views: 24905

Re: Can you (passively) heat an object hotter than your source?

The question clearly is not about the heat death of the universe I wasn't talking about the heat death of the universe, I said "a hypothetical scenario where the Sun, the target, and the laser are all enclosed within a perfectly reflective chamber with no energy flowing in or out, and the whol...
by Hypnosifl
Sun Apr 24, 2016 5:19 pm UTC
Forum: Fictional Science
Topic: Time-compressed but non-FTL interstellar travel.
Replies: 13
Views: 7533

Re: Time-compressed but non-FTL interstellar travel.

Afaik, tho, picking out a preferred reference frame isn't *bad*. Our universe doesn't appear to have one, but it's fine theoretically for one to exist. Yes I agree, but I figured there was a good chance the OP realized that one way of getting around the "FTL -> causality violations" probl...
by Hypnosifl
Sun Apr 24, 2016 4:21 am UTC
Forum: Fictional Science
Topic: Time-compressed but non-FTL interstellar travel.
Replies: 13
Views: 7533

Re: Time-compressed but non-FTL interstellar travel.

No wait, that's exactly what I intended. My thought was that M-space is configured (by magic) in such a way that the vector you take through space dictates a specific time shift. Like I said: going from 1,1,5:t' to 1,1,1:t", then t" must be t' - 4 I didn't mean that to be a special case f...
by Hypnosifl
Sun Apr 24, 2016 4:12 am UTC
Forum: Fictional Science
Topic: Time-compressed but non-FTL interstellar travel.
Replies: 13
Views: 7533

Re: Time-compressed but non-FTL interstellar travel.

The above argument hinges heavily upon the definitions of the relativity of simultaneity. Under the definitions used in the arguments above, it seems that "now" corresponds to the outer edge of the observer's light cone--i.e. everything that you can see happening "now" is regard...
by Hypnosifl
Thu Apr 14, 2016 6:07 pm UTC
Forum: Science
Topic: Can you (passively) heat an object hotter than your source?
Replies: 98
Views: 24905

Re: Can you (passively) heat an object hotter than your source?

Well, when the sun, the target, and the laser are in a closed system the target will heat to the temperature of the sun. Once it heats beyond that temperature it will radiate more energy, and that energy will go towards heating the sun. Yes, that was what I meant when I said the temperature should ...
by Hypnosifl
Tue Apr 12, 2016 11:14 pm UTC
Forum: Science
Topic: Can you (passively) heat an object hotter than your source?
Replies: 98
Views: 24905

Re: Can you (passively) heat an object hotter than your source?

We're talking about a rod, with silvered mirrors on each end and mirrors directing sunlight from the sides. There's no moving parts, no electricity, no external power source, other than the Sun. That's a passive system, sorry. I don't think 'passive' is the correct term here, "linear optics&qu...
by Hypnosifl
Mon Apr 11, 2016 3:20 am UTC
Forum: Fictional Science
Topic: What does a million-ton black hole eat?
Replies: 32
Views: 15425

Re: What does a million-ton black hole eat?

As far as the Hawking radiation goes, as I said before, if you use electrically neutral particles the interaction with the radiation may not have much effect on them. Okay, but you just suggested smashing charged particles together to create the nearby feeder black hole. I only mentioned neutral pa...
by Hypnosifl
Mon Apr 11, 2016 2:33 am UTC
Forum: Fictional Science
Topic: What does a million-ton black hole eat?
Replies: 32
Views: 15425

Re: What does a million-ton black hole eat?

No, there aren't plausible ways to create black holes that size on demand, but there are fictional methods that at least don't nullify the entire premise of why you'd be using the black hole in the first place. If you can move things fast enough to have tons worth of kinetic energy, then you've got...
by Hypnosifl
Mon Apr 11, 2016 12:18 am UTC
Forum: Fictional Science
Topic: What does a million-ton black hole eat?
Replies: 32
Views: 15425

Re: What does a million-ton black hole eat?

None of that answers the question of how you slow it down in the first place. Why "slow it down"? Are you assuming that whatever machine is used to create a million-ton black hole would tend to create one that has a very high velocity relative to the machine? If so, why? No, I'm simply as...
by Hypnosifl
Sun Apr 10, 2016 10:11 pm UTC
Forum: Fictional Science
Topic: What does a million-ton black hole eat?
Replies: 32
Views: 15425

Re: What does a million-ton black hole eat?

gmalivuk wrote:None of that answers the question of how you slow it down in the first place.

Why "slow it down"? Are you assuming that whatever machine is used to create a million-ton black hole would tend to create one that has a very high velocity relative to the machine? If so, why?
by Hypnosifl
Sun Apr 10, 2016 8:07 pm UTC
Forum: Fictional Science
Topic: What does a million-ton black hole eat?
Replies: 32
Views: 15425

Re: What does a million-ton black hole eat?

"Slightly larger", in this case, means 5.73 times larger. Thanks for doing the math on that. That doesn't account for the fact that you also need to force it into a circular orbit at that distance. Sure, both black holes are radiating more than enough power to do that, but only if you can...
by Hypnosifl
Sat Apr 09, 2016 5:53 am UTC
Forum: Fictional Science
Topic: What does a million-ton black hole eat?
Replies: 32
Views: 15425

Re: What does a million-ton black hole eat?

Gravitating bodies don't "spiral into each other", they orbit. Orbits only decay (into "spirals") when they're losing energy, which doesn't happen on useful timescales here. (Unless the ammo BHs are charged, but that gives the same problems as any other charged material.) I was ...
by Hypnosifl
Fri Apr 08, 2016 10:15 pm UTC
Forum: Fictional Science
Topic: What does a million-ton black hole eat?
Replies: 32
Views: 15425

Re: What does a million-ton black hole eat?

To actually get anything into a black hole this small, it needs to be a massive particle moving with more kinetic energy than its rest mass, or it needs to be photons. In either case, you need some power source outside the black hole that can produce as much or more energy than the mass equivalent ...
by Hypnosifl
Mon Apr 04, 2016 12:11 pm UTC
Forum: Science
Topic: square base cups
Replies: 24
Views: 5786

Re: square base cups

Wait, what? The base is acting as a lever arm in whatever direction the cup is struck, where the cup is struck defines another lever arm between that point and the point of the base on which the cup is tipping, and we'd ideally want to increase torque on the first and reduce it on the second, but r...
by Hypnosifl
Sun Apr 03, 2016 11:00 pm UTC
Forum: Science
Topic: square base cups
Replies: 24
Views: 5786

Re: square base cups

Given two cups, with the same area of bases, if one is square and one is round, I think round would better shape because all edges of the cup are the same distance from the center of gravity. the square cup would have some edge space closer to the center. the only way the square would be less likel...
by Hypnosifl
Fri Apr 01, 2016 11:01 pm UTC
Forum: Science
Topic: Miscellaneous Science Questions
Replies: 2910
Views: 683154

Re: RELATIVITY QUESTIONS! (and other common queries)

So, you say you understand the examples with FTL spaceships. Could you elaborate on your understanding of how these can break causality as a starting point? A transporter is exactly the same, is the issue. Well, 'understand' would be pushing it, but all the examples seem to depend on communication ...
by Hypnosifl
Fri Apr 01, 2016 10:51 pm UTC
Forum: Fictional Science
Topic: New (economically) type of FTL travel
Replies: 16
Views: 9490

Re: New (economically) type of FTL travel

The Tachyon anti-telephone paradox can still be done by passing paper notes, by using FTL ships to send the messages. Are you talking about what would happen if there was no preferred frame for FTL travel? I thought you said earlier that you were imagining a preferred frame, which would prevent thi...
by Hypnosifl
Sat Mar 12, 2016 7:27 pm UTC
Forum: Fictional Science
Topic: New (economically) type of FTL travel
Replies: 16
Views: 9490

Re: New (economically) type of FTL travel

Any trajectory that's FTL can be used to cause a time paradox. So you might want to handwave that away as well. One way out of this is to posit a preferred reference frame for FTL travel, so regardless of a person's velocity relative to this frame (and how their definition of simultaneity differs f...
by Hypnosifl
Thu Mar 10, 2016 2:30 am UTC
Forum: Science
Topic: Miscellaneous Science Questions
Replies: 2910
Views: 683154

Re: RELATIVITY QUESTIONS! (and other common queries)

If space and time are both infinitely extensible, there is no privileged choice of x and t coordinates. If space makes a loop (pac man universe, cylinder), then there is a privileged frame in which x has the minimum value for length around the circle, and t is orthogonal to that. A rocket which lea...
by Hypnosifl
Tue Mar 08, 2016 9:17 pm UTC
Forum: Science
Topic: is Chicago ever the "front" of the planet?
Replies: 30
Views: 6657

Re: is Chicago ever the "front" of the planet?

Or the villain/victim are not initially at rest relative to the Earth. True, but in that case Galilean relativity implies all that matters is their velocity relative to the Earth, if you already know that then their velocity relative to the Sun doesn't have any additional relevance, so the villain ...
by Hypnosifl
Tue Mar 08, 2016 12:05 am UTC
Forum: Science
Topic: is Chicago ever the "front" of the planet?
Replies: 30
Views: 6657

Re: is Chicago ever the "front" of the planet?

If you want to "smack" somebody, what good does it do to have the ground racing past at 30km/s? I've already explained that I understand the idea of smacking something with Earth's orbital speed as the idea that you'd completely stop something and have Earth run into it at full speed. Whi...

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