zapatos

What is the behavior of a photon inside the event horizon? Is it able to travel at c from our perspective (if we could see it)? Since it cannot escape, does it simply orbit the black hole? If it is travelling on a path from the center of the black hole toward the event horizon, since we know that it cannot escape, does it lose velocity? Do photons even exist inside the event horizon?

I just read A Universe from Nothing by Lawrence Krauss and this book makes the argument that the universe may very well have come from nothing. He said "The lesson is clear: quantum gravity not only appears to allow universes to be created from nothing - meaning, in this case, I emphasize, the absence of space and time - it may require them." A great book covering many aspect of science I see being discussed here every day, presented at a high enough level for me to understand (although I'd be hard pressed to summarize it. ). You may wish to take a look at it.

Great explanations from both of you, thanks. I understand why natural selection seems a likely component of life now. Do you think it possible that natural selection can ever stop happening in a life form at some point? For example, let's say the DNA (or whatever) is not only the carrier of genetic information, but also serves as a physical structure of the organism that is critical for life. Then if the carrier of genetic information has mutations, it would affect the physical structure, thus resulting in death. And of course then no possibility of passing on the mutation. Or am I getting too far fetched?

ydoaPs started out fine when he said that the fear of an imminent nuclear weapons program is "Based on absolutely zero evidence". He then went from that statement to "Iran does not have a nuclear weapon program". My question is, What led ydoaPs to assert that "Iran does not have a nuclear weapon program"? Not all "zero evidence" is equal. If you have never looked for a nuclear weapons program you have no evidence of one. If you've looked extensively and not come up with any you still have no evidence of one. However, if you have no evidence after looking, and can specifically rule out a nuclear weapons program at some sites, then you can speak with more confidence (but not certainty) that one does not exist. The more you look the more confidence you have. I believe you can provide evidence that a nuclear weapons program does not exist (as opposed to providing evidence that an invisible dragon doesn't exit). An invisible dragon is supernatural and leaves no natural trace of itself. A nuclear weapons program is natural and therefore exists in nature. While it would be difficult, it is possible to search every inch of Iran and provide evidence that no trace of those components of a nuclear weapons program exists in Iran. Partial evidence that a nuclear weapons program does not exist would of course come from things such as unrestricted access to suspected sites by the IAEA, as this is a partial search of the country. After all of this writing I believe I would have been better served if my first response to ydoaPs had been: "You have asserted that Iran does not have a nuclear weapons program. What level of confidence do you have in that statement and why?"

Since extraterrestrial life is an unknown, I think a definition that is more flexible would be required. Perhaps something that says 'points x, y, and z are required, but indicators of life also include points a, b, and c'. In this case I would include Darwinian evolution as a possible indicator of life, but not a requirement for life. I'm speculating, and that is why my support has been only imagined scenarios. Is it really that unlikely that the ability to evolve in some form of life might exist at one time and then be lost? Why? Again, I think it is reasonable to create a definition of life that includes 'possible indicators' of life that don't necessarily have to exist in all possible life forms.

Yeah, line one is clearly out of whack. I stick with line two.

WTF? If you tell me you are hiding an invisible dragon in your garage I'm just supposed to accept that claim and not question it? I guess they changed the rules on this site. I didn't realize that you were now allowed to make factual claims but not be expected to provide evidence. :blink:

Based on absolutely zero evidence, btw. 1) Iran does not have a nuclear weapon program. I understand that there is no evidence (known publicly at least) that Iran has a nuclear weapons program, and I have heard many people say they don't think that Iran has a nuclear weapons program, but I am curious how much evidence you have that Iran does not have a nuclear weapons program. I was unable to find any although admittedly I may have missed something.

I don't see the possibility of an artificial uterus anytime soon, but this might be something to think about long term. http://en.wikipedia.org/wiki/Artificial_uterus

Unfortunately I don't think any concession to the pro-life crowd short of 'life begins at conception' will do. I also don't think changing the discussion to personhood will do either. From my perspective we should just go with the idea that abortion is legal and come up with a 'reasonable' time frame needed to recognize the pregnancy and make a decision on whether or not to terminate. I think 26 weeks sounds like a reasonable time frame. There will never be agreement on when life begins, when personhood begins, what brain function determines life, etc. Therefore we should try to stay away from that kind of discussion. Abortion was made legal without answers to those questions, so let's not introduce them now. I like this proposal a lot, except for the problem that the date of independent living will likely shorten over time. I'd prefer to lock the date in.

I was not trying to develop an appropriate definition of life. You asked if there were any problems with a specific definition and I pointed out a problem that may exist if you were including extraterrestrial life. If you are not including extraterrestrial life I have no problem with that definition. If you are including extraterrestrial life, then I do. Without mutations to DNA we would not have evolution. If a life form exists that cannot have a heritable mutation, darwinian evolution would not apply. Abiogenesis could be part of it. An environment may exist that allows for a simple form of life to form over and over again without reproducing. A life form may exist where the information on how to reproduce is encoded on a portion of the organism critical to life. If that portion of the organism changes, it cannot live. We hadn't been necessarily discussing 'complex' life forms. That will likely be a different issue as that life form needed some method to become complex. Although I suppose it is possible for a life form to originally be subject to evolutioin, but then to have that ability to evolve cease due to environmental or organism functions.

The risk is not greater just because of the greater likelihood. As you pointed out, risk is a combination of likelihood and impact. Based on your scenario you have not shown that the risk of local terrorism is greater than the risk of nuclear holocaust. I would not be surprised to find that at this point in time that Israel has determined that the risk of nuclear annihilation is a bigger risk to Israel than a suicide bomber in a market. While it is nice that you have such confidence that Israel need not worry about Iran, I doubt that Israel has your confidence. When contemplating the possible end of the Jewish state due to an Iranian nuclear strike (one bomb will quite likely do it), I imagine that Israel believes a bit more risk mitigation is in order.

No need for me to propose anything. It is already being done. http://en.wikipedia.org/wiki/Astrobiology Without developing a hypothesis about how life on Mars may have existed, scientists would not know how to design their experiments. http://en.wikipedia.org/wiki/Life_on_Mars Well, as I said, if we are talking about extraterrestrial life, Darwinian evolution may not be a factor. Evolution on earth is possible due to DNA and how it is replicated. It is easy enough to imagine scenarios where that type of replication, and thus Darwinian evolution, would not take place.

One of the reasons to make a definition of life which you don't know exists is to aid you in your research. If an astrobiologist wishes to search for life on places other than earth it is helpful to have some idea of the evidence you should be searching for. Developing a hypothesis based on what you already know is not really that hard. It is standard science. http://en.wikipedia.org/wiki/Astrobiology

Are you limiting your definition of 'life' to life on earth? I would not be surprised to find there is a something on another planet that acts as life on earth does with the exception of Darwinian evolution.

Right, and that's my point. We can both point to situations where extra guns are better and worse to have around. The way you said it was that more guns did not make the situation better. If you meant to say that in some instances the situation is not better, then I agree. According to the news reports I read the properly trained people killed NO innocent bystanders; only the person who had just murdered someone and was pointing his gun at the police. Since your premise is wrong I don't think it can be used to support your conclusion. Understood. I wanted to call it out though because it was misleading. Again, I don't think you have the data to support this conclusion. A man with a gun just killed someone on the streets of New York indicating he was not too concerned with the safety of others. He then threatened police with that gun. Given that the result of additional guns on the scene resulted in only one more death (that of the gunman) and no bystanders (although they were wounded, mostly by bullet fragments), a reasonable argument can be made that more guns on the scene saved lives. Zero guns would have been perfect. You are counting the shooter as not having a gun too, right? I don't understand your 'added irony' point or your 'rather than miss it' point. Are you suggesting if I want to address one comment you make in a post that I must address all comments you make? Ok... I agree that is not a good idea. Did someone from the US treat you badly? I notice that you rarely pass up the opportunity to subtly (or not so subtly) put down the US, its people, history, cutoms, etc. On behalf of all Americans, I would like to apologize for whatever it is we did to annoy you.

He didn't say 'they don't necessarily make us safer'. He said 'having more guns present doesn't make the situation better. That is more than a semantic quibble. It is the difference between 'it does happen' and 'it doesn't happen'. If he misspoke then I withdraw my comment.

I don't believe you have the evidence to make that claim. I can easily point to situations where more guns present does make the situation better.

If you are quoting someone else you should put it in quotes or use the quote function, and you should also name the source of the quote. It is very confusing (and against the rules) to not do so.

What are these bold steps you allude to?

Oklahoma City bombing in 1995.

This is an example of making charcoal in a large drum. Simply downsize for the container you are using. http://www.eaglequest.com/~bbq/charcoal/

On the other hand this is a proof based on words and not data. The likelihood of life could have been infinitesimally small and we were just damn lucky that tiny chance came through. Starting with a different theory we could have come to the conclusion that life was not possible.

Unfortunately 'privacy' is a very general term. It seems to me that if Obama takes an action that erodes some aspect of rights we believe are contained in the term 'privacy', and his actions are ruled to be legal, then this newly defined (and more limited) definition of 'privacy' is indeed the level of privacy we were guaranteed by the constitution. While I have no desire to give up any rights I've been exercising, whether guaranteed or not, it seems unreasonable to fault him for playing by the rules.

Ok. I understand how privacy is being eroded. I guess I was thrown by your statement that he is abusing the bill of rights. As long as what he is doing is legal I don't see how he could be viewed as eroding our rights under the constitution.