swansont

The moving of light source doesn't matter to the observer of the light source measuring the speed of light relative to him. But it matters if he is measuring the speed of light relative to some other frame. Co-location does not imply simultaneity if the co-located points are moving with respect to each other.

! Moderator Note This is off-topic for this thread and also not mainstream physics. If you wish to discuss it, start a thread in the speculations forum

But if you are going to incur debt, now is the time to do it, when debt is cheap. Putting people to work through spending at least has the benefit of removing them from unemployment and gets them paying more in taxes. Each dollar of spending that goes to wages doesn't cost a whole dollar. The total amount of work that needs to be done is much larger than what was in the stimulus bill is why; I don't think the stimulus was sold as curing all of the issues. We have been scrimping on maintenance for decades to help fuel the illusion that low taxes is a viable condition. Preventative maintenance not sexy, so nobody cares too much, until there's a catastrophe. (But then it's a crisis, and we temporarily respond well to crises these days — we ask no questions and are even willing to make some sacrifices) I don't think not hearing about it has any more weight than not hearing about it in the past; it's more "out of sight, out of mind."

Carat is a unit of mass. While the value per carat is variable depending on the specifics, diamonds are indeed sold by weight, and the price (for gem-quality diamonds, at least) is not linear (e.g. a 2 carat diamond is not simply twice the price of a 1 carat diamond)

They both have to agree on what each observer sees, because the solutions are single-valued. This is neither a flaw in nor a violation of any principle of relativity.

As I pointed out a few posts back, compensation for civilian employees comprises only about 7% of the budget (and military pay is about 4.5%). The government buys a lot of products and services. We have almost 150,000 structurally deficient bridges, and most of them are in use. http://slacktivist.typepad.com/slacktivist/2010/08/5-bridges.html The stimulus package included $50 billion of transportation infrastructure. That's $333k per bridge, if money is spent all on bridges, which it isn't. That's puny. The Wilson bridge reconstruction cost $2.5 billion. The repairs on the Tappan Zee is estimated at $6.4 billion I'd hate to be a politician who votes against infrastructure improvement when the next bridge collapses, especially of there is a loss of life involved.

Strength of field is the local value for g, which is GM/r^2. The gravitational potential, which tells you the extent of the dilation, is GM/r. With the proper choices of M and r you can have earth's acceleration, but a larger or smaller amount of time dilation. (e.g. by doubling or halving r and changing M by a factor of 4, you can double or halve the potential with g still at 9.8 m/s^2) Myriad demonstrations of time dilation have been quantitative, so it's much more than saying increasing gravity reddening the source.

An object deeper in a gravitational well will feel more dilation. It's not the strength of the field.

It's circular about the wire. The field direction is given by the right-hand rule: If your thumb points in the direction of the conventional current, your fingers will curl in the direction of the field.

Fusion does not directly produce IR photons. They are produced from the other processes discussed in this thread. What is lacking in these answers that have been given, that you persist in asking the same question over and over?

I agree. What time is (or what energy is or what momentum is) are metaphysical questions. At some level, it's bookkeeping which allows us to quantify what's going on around us. These are the useful parameters since they can be measured and have some use to us. The rotation of the earth doesn't "use" energy, per se, and is used to measure time. It has energy, but then, so does a meter stick. For that to be true one must expect that a charged particle held in a strong electric field would feel time dilation. I don't know of any theoretical framework which would lead to this, nor any experimental evidence to indicate that it's true.

I take it you have not read The Hitchhiker's Guide to the Galaxy

It doesn't begin to move under those conditions. It is already moving. It's called conservation of angular momentum. Entropy does not absorb energy. No. A change in entropy cannot, in and of itself, cause rotational motion. That requires a torque.

The answer has been given to you.

Yup. This was a discussion of the ladder paradox, not your "who is older, A or B" scenario. There was no discussion of clock synchronization or time dilation. I think everyone here realizes that there is no absolute frame in SR.

Because, like much of the way physics is done, it is approximately correct. And there's a lot you can do with an approximately correct model. The trick is in knowing the conditions under which it breaks down.

Newton's laws are the basis for the study of dynamics and statics.

Good summary of the evidence recently at S.W.A.B. http://scienceblogs.com/startswithabang/2010/09/geocentrism_was_galileo_wrong.php

Mea culpa. I did not read the whole thing carefully; I was focusing in on 3&26 wondering who had mentioned the ladder paradox, so I shouldn't have quoted the whole statement without pointing out that there were errors. You are quite correct: each will think the other has been shortened by length contraction and that is the source of the "paradox," as it involves the doors shutting and opening. From the barn frame the ladder is shortened and quite easily fits inside, so the front door can shut before the back door is opened. But from the ladder perspective the barn is contracted and the ladder will not fit inside, so the back door must open before the front door shuts. Thus there is a straightforward example of the order of events changing depending on the frame of reference, which is driven by simultaneity being relative.

You may not have meant to target anyone, but that's what ended up happening. It became personal when you quoted my posts and told me, erroneously, what I was saying or doing, and what my objective was in doing so. I don't like being misrepresented.

There's a lot here, but I will comment on this for the moment: The government has been doing this, and government civilian employee compensation comprises about 7% of the total budget, so it's not like many companies, where compensation is a large fraction of the budget.

For your scenario, the answer is probably easy: use data from 2 years ago for the 2 LY object and 3 years ago for the 1 LY object. At such distances the speeds are small, and the objects will not have moved much. The more distant object still moves faster. For the broader picture, and more distant objects, the distances used are the distances now, not the distances when the light was emitted. http://www.astro.ucla.edu/~wright/cosmology_faq.html#DN

I posted it, and like most of these so-called paradoxes, they really aren't — it's a paradox only if one assumes simultaneity is absolute. The reason I mentioned it was to rebut the notion that the order of events couldn't differ in different frames. The ladder "paradox" is a classic example of that very thing; the order of the events, i.e. the ladder entering the barn and the doors shutting and opening, depends on which frame the observer is in. No forces need be involved, though. You can look at the situation after the ladder is moving relative to the barn, and there are no accelerations to worry about.

Yes, or in this case, not raising price in order to not lose market share. If you have an additional cost in the form of taxes, and you want to raise prices to compensate (which was your contention, a few posts back), you may suffer a loss of sales if your competitors do not, even if demand is inelastic. We were talking about the effect of taxes. Unrelated costs are irrelevant to the discussion. I agree, saying our taxes are insufficiently high because others are higher is silly. Our taxes are insufficiently high because we spend more than we take in, and nobody is willing or able to cut spending. But, it still remains a fact that the most recent balancing of the budget came with higher taxes, and the economy was doing OK in that era.

My issue isn't that you drew attention to the logic. It's that you did it by repeatedly accusing the wrong target of using that logic.