# losfomot

Senior Members

323

1. ## falling faster than light

The situation can never happen. The closer you get to the speed of light the shorter the distance to your destination (length contraction). You will always hit the source of gravity before you reach the speed of light relative to that source.
2. ## Basic question about the special theory of relativity

I don't think you've got that right. The train contracts in the direction of travel... if the train was moving toward you, you wouldn't have a skinny train, you would have a short one (The distance between the front of the train and the back of the train would become smaller) The way your describing it, the distance between the left and right sides of the train becomes smaller ie. a skinny train. I'm no expert, but that doesn't sound right.
3. ## Basic question about the special theory of relativity

You're still sounding a bit confusing... why do you keep saying '1*c' ? What does that mean? 1*c = c so why not just say c. At any rate, saying that is wrong. A person on the track watching the train approach would NOT see the light approaching at 1*c faster than the train. The light from the train would approach the observer at exactly c. The train itself would have to approach the observer slightly slower than c (since the train cannot actually be moving at c relative to anything)
4. ## Very Fast Flywheel

I don't think so... the problem in doing it experimentally is the centrifugal force generated... For a 10 meter diameter Flywheel... just to get the rim to a speed of 300km/sec (or 0.1% of c) would require the wheel to turn at a rate of 572,958 RPM (or 9549 RPS) This would generate an acceleration, at the rim, of about 18 million km/s/s... I don't think there will ever be a material that can withstand that kind of force. Just for the heck of it... For a 2km diameter flywheel... just to get the rim to a speed of 300 km/sec (or 0.1% of c) would require the wheel to turn at a rate of about 2865 RPM (or 48 RPS). This would generate an acceleration, at the rim, of about 90,000 km/sec/sec... there might be a material that can withstand that kind of acceleration, so let's take this one a bit further... Let's say our 2km diameter flywheel was constructed on top of a scale that showed a base weight (flywheel not moving) of 1,000,000 kg (probably an unrealistically small number for this size of flywheel, but...). If we got that wheel up to 2865 RPM (and the wheel managed to hold together against the tremendous centrifugal force) our scale should now read 1,000,001 kg. Yep, 1 kg is all we would gain from our 2km wheel whipping around almost 48 times every second. Length would also only contract by 0.0001%. And Time would also only dilate by .0001% I hope my #s are right, it would have been quite a mess if I had tried to show my work as I did it... I'm sure Norm or someone will correct me if I am wrong... The point is, it would be very hard/expensive to construct an apparatus to test this. EDIT- Actually my 1 kg figure is even too much, since the mass increases to .0001% the closer you get to the rim, the mass of the flywheel, as a whole, would increase much less than 0.0001%.
5. ## To all crac...err...alternative scientists

I think these statements about the first article are a twisted exaggeration. More generally about the OP... People need someone to look up to... why not Einstein? Why get defensive about people that look up to him? He is a marker of a time when the universe became that much more understandable. It is not (generally) HIM as a super-physicist that people revere... it is more him as a symbol. Einstein opened up a new world of physics, but if he hadn't done it, someone else would have. When people say things like 'where's the next Einstein?' they really mean, 'where's the next major turning point in our understanding of the universe?' Einstein was a doorman... he opened a bunch of doors for us all at once. Science is opening a door here and there in some places, peeking through some keyholes in others, trying to fashion keys and lockpicks. The world is waiting for the next doorman to come along and open another bunch of doors. Inevitably it will happen, and the person that does it will be the next big thing to Einstein. It could be some little thing that any physicist could have and would have stumbled upon eventually, but because BenTheMan stumbled on it, and because he's a pretty smart guy in general, it is his name that will go down in the history (and physics) books, it is him that will be famously quoted for statements (even ones that have nothing to do with physics), and it will be his name that people will use when waiting for the next big turning point in physics... 'where's the next BenTheMan?' ... there will be some people on some future science forums that ask 'why do people worship BenTheMan? I mean, don't get me wrong, he was a smart guy, but was he the smartest physicist ever to live? I don't think so.'
6. ## Very Fast Flywheel

Isn't that what we were talking about? I don't know why it has to circulate, but yes, mass is just a stable form of very dense energy... I agree, others probably don't. Yes, an outside observer would see the wheel increasing in mass with an increase in speed... moreso closer to the rim of the flywheel. This is how the wheel stores energy to compensate for the speed of light being constant in all frames. (Now, if you were to throw an indestructible stick into the spokes of our relativistically fast, mass-increased flywheel... stopping it all at once, I would have to agree with the term DOOMSDAY WHEEL) What is so disappointing? What were you expecting?
7. ## Very Fast Flywheel

The result is opposite? I thought it would be the same, only your looking at it from the opposite direction. With a black hole your approaching the horizon from the outside... With our flywheel, your approaching the horizon (the rim) from the inside... in both cases, the circumference of the flywheel (or event horizon) gets smaller, the closer you get to the rim. Assuming you are correct, a 300 meter radius would give an acceleration (at the rim) equal to the speed of light (sort of a reverse black hole). And the rim would have a rotational speed of only (about) 10% of the speed of light. Hmmm... We are going to need lower rpms and a bigger flywheel in order to get the rim moving faster, because no amount of spiderman silk or nanotubes or anything else will hold up to that kind of centrifugal force.
8. ## Very Fast Flywheel

Ummm... what is the radius we are talking about? That was kinda my question. Are you referring to my original post which brought up a 10 meter diameter? Or are you assuming that I already know the radius of the real-world flywheels that you just brought up? In all honesty, I am not interested in the centrifugal forces acting on the flywheel, I am more interested in the relativistic effects. I am sure that, as you get into relativistic speeds, the centrifugal forces become extremely large. But let's assume that the flywheel is made of nanotubes or lets even skip ahead to a material that is strong enough to withstand any centrifugal force that we might reach for the duration of this thread. I hope we don't have to use that equation. I thought we should be able to simply take the length of the perimeter along with the rpm, and we will have the speed at which the rim of our flywheel is traveling. For example... using your 10,000rpm with my original 10 meter diameter flywheel, the rim would be only moving at 5236 m/s or 1.746% of the speed of light. What I am really interested in is what happens when the rim travels closer to the speed of light? What would time dilation and length contraction do to the flywheel? As Sisyphus put it... what would you see from the hub looking out or the rim looking in? What would you see as an outside observer watching the flywheel turn? (aside from a blur) Would the fly wheel hold together? (again, disregarding centrifugal (or centripetal) forces) For example, from the point of view of the rim, I would imagine that the diameter of the flywheel would have to be significantly smaller than if measured from the point of view of the hub. If I am right, are these just differences in measurement or would these effects have a physical impact on the flywheel?
9. ## Very Fast Flywheel

10,000 rpm does not sound particularly fast... how big are they? Do you mean just because of the centrifugal forces, or a relativistic effect? Can you elaborate on that?
10. ## Science-based criticisms of Farsight's Theories

I'm sad to hear this thread is being closed... it's obviously very popular... why not just move it to speculations and leave it open?
11. ## earth and moon

I think the most correct response would be to say that the Earth-Moon system is orbiting the Sun. If the Earth suddenly vaporized, the moon would continue it's orbit around the Sun.
12. ## black hole gedanken

If you lower the string slowly, then I believe the answer is that you can lower as much string as you want, you will never reach the event horizon.
13. ## Frozen water = dirty water?

I noticed that when I freeze a bottle of water and then thaw it out, it is filled with little floaties. Does anyone know what this is? The water is crystal clear before freezing. It is in a sealed, unopened, plastic bottle. I've tried different brands of water and the same thing happens.

I like to use this one. When I enter z=1100 this calculator most definitely tells me that objects were moving at super-luminal speeds at that time in the universe.

No, you are just taking the distance light can travel in that time, using it as a radius, and doubling it for a maximum diameter. That is not what I meant. Yes, the farther apart they are spacially, the faster they are moving away from each other. If they are far enough apart, they will be moving away at speeds approaching light speed. If they are even farther apart, they will be moving away at speeds faster than light. I understood what you meant. Yes. (although that rate changes over time (for everyone)) Not regarding co-moving objects (objects moving away from each other due to the expansion of space) It is one of the few times objects can go faster than light. I thought that there has always been super-luminal expansion. I am not sure what the Hubble parameter was when the universe was 380,000 years old, but I think it was pretty high. I calcu-guess an answer of 2,300,000 km/sec/Mpc Which should mean (by v = H0d) that anything more than 425,478 LY away would have been moving away faster than light. Of course, I am probably way out in left field with these calcu-guesses.

First off, I don't think this is true, the distances could have been further apart than that, because the expansion can result in two points moving apart faster than the speed of light. So 380,000 years after the big bang, the universe could have had a diameter larger than 380,000 light years, but anyway... Pick a photon at that time in the universe and the relative spot in spacetime that the Earth will eventually occupy (we'll call this spot E). Let's say the two are 100,000 light years apart. The photon is racing toward E at the speed of light, but the universe is expanding, so E is moving away from the photon at a considerable speed. 100,000 years later, and the photon is still 98,000 light years away from E. 98,000 years after that, and the photon is still 96,000 light years away from E... still moving toward E at the speed of light, but having a hard time catching up to E because of expansion... 13 billion years or so later, the photon has finally caught up to E. escape what? the universe? Not round and around, it goes in as straight a line as spacetime allows it to go in, it just has a hard time catching up to other parts of the universe because of expansion... there is a part of the universe (that the photon is moving toward) that is moving away (because of expansion) faster than light... so the photon will never catch up to that point in the universe (unless the dynamics of the universe change in the future, and the expansion slows down)
17. ## Very Fast Flywheel

The perimeter is moving near the speed of light, but the hub is not anywhere near that speed... wouldn't time dilation and length contraction come into play? More so the closer to the perimeter?
18. ## Very Fast Flywheel

Say we were to make a 10 meter (arbitrary number) diameter flywheel in a vacuum and, with a series of gears, constantly increase the rpm of that wheel. There will be a huge difference in speed between the hub and the outer edge of the wheel... Relativistically, what would happen to the wheel? (apart from flying apart from the force of the spin.... let's assume it is made from a VERY strong material)
19. ## Density

Obviously O2 gas is not denser that water. I figured it might be the atomic density or some such craziness, but anyway, I got my initial figure of 1.43 g/cc here Of course down below the list it says: Sorry, I shall try to double check things a bit better next time. Anyway, so the answer to my original question would be yes. I did mean, and should have stated, STP. What this all comes down to (for me) is this: The densest element on the periodic table is Osmium... have we been able to make a molecule/compound/material denser than 22.6 g/cc? and if not, is it possible?
20. ## replicator technology

A replicator does not make something out of nothing. It takes energy (from the warp core or whatever) and converts that energy into whatever matter we ask it too. No conservation law is broken.
21. ## Density

That example does not make it seem so trivial... H20 density = 1 H density = .09 O density = 1.43 I should have worded my question like so: Can a material be denser than the densest element it is composed of ?
22. ## Density

Can a material (or molecule) be denser than the elements that compose it? I notice that the element Carbon has a density of 2.267, while diamond (which is Carbon) has a density of about 3.5 It occurs to me, though, that 2.267 could be an average density of the different forms of Carbon... is this so?
23. ## nuclear fusion or cold fusion

Its funny that nobody has cleared you up yet on what fusion is... probably everyone thinks it is a simple enough question that you should do a little simple research for yourself, and they are right. Anyway, it does not involve water, except that water is a source of the hydrogen that you could use for the fusion. Put simply, fusion is taking two atoms (like two hydrogen atoms) and forcing them together, using lots of heat and pressure... the result is one heavier atom (like helium) and some leftover energy that is quite substantial. It is a way of turning mass into energy, and there is a lot of energy in a small amount of mass. Cold fusion is accomplishing the same thing, but at room temperature and normal pressure. Wikipedia is a great place to check things out for yourself.

Do any of you know of any science based radio stations on the internet. I like to listen to thought provoking shows, but I can't really find a station devoted to that kind of thing.
25. ## weird cloud thingy

The grey cloud is denser. It has more moisture. It is more likely to cry.
×