Spyman

And I am telling you that it does NOT matter if it "will vaporize in the atmosphere", because if it is large enough we will die anyway! We are back at post #10, reread it very carefully and come back when you are able to actually provide the evidence needed to support your claim. "The amount of energy released by a single large collision or many small collisions is essentially the same, given the physics of kinetic and potential energy." http://en.wikipedia.org/wiki/Asteroid-impact_avoidance Both a spherical swarm with 1 000 000 000 000 000 pieces of 10 cm diameter iron balls or one single solid iron ball of 10 km diameter will kill us. (If they hit us with sufficient speed, like Comet Shoemaker–Levy 9 that hit Jupiter with a collision speed of approximately 60 km/s.)

The center of mass of the Earth-Moon system contains both bodies mass and yet Earth doesn't occupy everything up to the Moon's backside. The Singularity is a theoretical point in the center that is containing the Black Hole's mass, but this singularity also signals the break down of Relativity so there is likely something else at the center. So whatever hypothetical core the Black Hole has it doesn't need to reach all the way out the Event Horizon, it could very well and most likely does have a surface much much further down. Once something pass the Event Horizon it is outside of our boundary in spacetime beyond which its events cannot affect us. I am not knowledged enough in Relativity to comment on how relative timekeeping proceeds from there, but as far as I understand it that something is *outside* of our rate of time. Here is a good link for advanced readers: 7.3 Falling Into and Hovering Near A Black Hole

First: IF you allow something to violate the known laws of science then you can no longer use those broken laws to predict what would happen. Secondly: There are a lot of objects in the Universe receding from us right now with speeds greater than light due to the expansion of the Universe. If you would have a long enough rope and tied it to a spaceship that takes of in any direction then at some very very distant point it will seem to start to gain speed and accelerate to speeds greater than light, since it would gain recessional velocity from the expansion, as seen from the other end of the rope down on Earth. Even if the rope should be on a suffiently large reel letting out rope freely it would not be able to spin with the speed of light and therefore the rope should start to streach faster than light and snap somewhere in between the spaceship and Earth. Further more if the rope should be able to streach out and hold for a short duration while the spaceship is receding slightly above lightspeed there would not happen any strange stuff along its extension and you would still not be able to climb it faster than light to reach the ship. EDIT: I didn't realise that this thread was named "time travel" so I want to add that the hypothetical distant spaceship or any distant galaxy that we can observe today receding from us with speeds greater than light are not thought to be going backwards in time.

Well then, since I said: "break it up into smaller pieces will only help if it is to small to cause an catastrophic extinction level event". It seems you now have changed all your statements so they agree with everything I said in post #4. There will always remain a possibility for an unexpected and to fast approaching or entirely to huge rock for us to handle, so to ensure humanity's survival we need to spread out to several self supported colonies beyond this system. But I think we already have the needed knowledge to deflect a threat from a large amount of ordinary asteroids, if we only get enough warning time to perform required actions. The earlier we manage to alter its trajectory the less needed change in direction is necessary.

Clearly it is fully possible to return to the exact same previously visited location in all three space dimensions but not in the time dimension.

Whether you like it or not, that is enough to disprove your claim that the inside of an observer's past light cone is not observable. I have not tried to prove that in the future there will be 2 Earths, one in the present and one with 3 sec. of delay.

Contradicted by this statement: Yes sure, but that was not the only thing I wrote, was it? You are cherry picking statements and ignoring the context. Yes, of course it is an image travelling at c, you are avoiding the question and trying to wriggle your way out of it. I thought I proved in my post #141 that the interior is observable and you agreed, but never mind carry on...

See - You are doing it again Michel, you don't even seem to be trying to understand what I said and engage in my arguments. I never claimed anything of what you seem to think I did. So I am done repeating my points and trying to explain where you are clearly wrong and why. When I look in a mirror I belive I see myself in the past, the real me, not another Spyman that is not me or something else. What do you think you see in the mirror, since it can't be the real Michel and not another Michel either, is it a fake Michel?

Delay exploits the fact that both the Earth and the impactor are in orbit. An impact occurs when both reach the same point in space at the same time, or more correctly when some point on Earth's surface intersects the impactor's orbit when the impactor arrives. Since the Earth is approximately 12,750 km in diameter and moves at approx. 30 km per second in its orbit, it travels a distance of one planetary diameter in about 425 seconds, or slightly over seven minutes. Delaying, or advancing the impactor's arrival by times of this magnitude can, depending on the exact geometry of the impact, cause it to miss the Earth. http://en.wikipedia.org/wiki/Asteroid-impact_avoidance#Collision_avoidance_strategies Asteroids usually have a direct orbit. By February 2011, astronomers have identified a mere 36 asteroids in retrograde orbits. The retrograde asteroids may be burnt-out comets. Comets from the Oort cloud are much more likely than asteroids to be retrograde. Halley's Comet has a retrograde orbit around the Sun. The first Kuiper belt object discovered to have a retrograde orbit is 2008 KV42. http://en.wikipedia.org/wiki/Retrograde_motion#Asteroids.2C_comets.2C_and_Kuiper_belt_objects

A Black Hole is from an outside view the volume enclosed by its Event Horizon, for a full understanding of distances and flow of time on the inside you need to learn General Relativity.

Ok Michel, have it your way. There is no point in trying to discuss with you if you stubbornly refuse to acknowledge raised issues.

But the thing is that there is another you in the past waving at you in the future and it is in theory possible for you to observe it. You need to reconsider the reality of observation and its impact on your view of time beacuse you make contradictory claims. You need to to bear in mind that this is not a recording, it is real photons emitted live directly from yourself, they are equally real and valid as the photons coming from the astronaut standing beside the mirror on the Moon. The history that both these two live streams of photons show you are equally real and both the astronaut and you who were emitting these photons were also equally real, there is no fake or altered images trying to fool you. When you are standing here on Earth and looking up at the Moon it is not orbiting around the Earth gravity you feel under your feet, according to Relativity gravity also travel at the speed of light, so the Moon you see is subjected to and orbiting around old Earth gravity from the past. In fact if you would draw this on a spacetime diagram, you will notice that the Moon you see in the skye is orbiting the exact same old Earth gravity that you would see in the mirror, which is holding the reflection of the past you down on the surface of the old Earth.

The ignition coil from an old car is fully capable to produce long sparks and is around the same size as an small Coca-Cola bottle.

I think it's little easier to push the 'tiny' rock than the 6 000 000 000 000 000 000 000 000 kg massive 13 000 km wide blue sphere.

It might not be practically possible, but in theory you could place a mirror on the Moon and with a good telescope you could then see the reflection of yourself 3 seconds back in the past. Edited to insert Michel's quote since my post ended up on a new page. Edit 2: Corrected the time for light signals between the Moon and Earth.

I interpret it as they try to point out a serious threat without sounding like doomsday prophets. First I would like you to validate your bold claim that: "Sunlight ... is ... more energy than some meteor". Prove it, assume the meteor consists of mostly rocky material, had a diameter of 10 km and a relative impact velocity of 60 km/s against Earth. Please show us how the total solar energy absorbed by Earth in a few seconds is more than the kinetic energy it would release in the atmosphere. Secondly, the deadliness of an killer asteroid impact is not due to its capability to penetrate and shatter the Earth's crust at one local site. The danger is their ability to on global scale affect the whole Earth's climate by injecting very large quantities of dust and small particles into the atmosphere causing a long period of nuclear winter or by increased heating to an longstanding uninhabitable temperature. Various studies and simulations have been made and the general consensus seems to be that the dangerously threshold diameter is between 1 and 2 km, where sizes above 10 km would ensure humanity to be completely destroyed, larger sizes of hundreds of kilometers can vaporize all the Earth's oceans. I am not an expert on asteroids or impacts and there is not likely anyone that to one hundred percent can guarantee their predicted outcome and its difference between one large asteroid or many small pieces. But everything I have read about the subject, from general public information to more advanced scientific articles made by professionals, consistently agrees that breaking it up into smaller pieces won't help and might even make it worse. So, once again I will ask you to provide evidence, please give us one quote and a link to any creditable source claiming that breaking up an asteroid larger than 10 km in diameter to smaller pieces before it would hit Earth could save the human race from armageddon. Because I am simply not going to take your word for it. I never claimed that nuclear bombs would be without drawbacks, I said it could be used to: "fragment, vaporize and/or deflect an asteroid". The ultimate goal would obviously not be to fragment the asteroid but to make it MISS Earth completely. (If an attempt with nuclear weapons should fail it would not be good and could certainly become worse.)

Can Aliens Find Us? Oct. 23, 2003 by Seth Shostak - Senior Astronomer Bottom line? With radio technology slightly more advanced than our own, Homo sapiens is detectable out to a distance of roughly 50 light-years. Within that distance are about 5,000 stars, all of which have had the enviable pleasure of receiving terrestrial television. And each day, a fresh stellar system is exposed to signals from Earth.

400 Volt and 150 microFarad

The point at which tidal forces destroy an object or kill a person depends on the black hole's size. For a supermassive black hole, such as those found at a galaxy's center, this point lies within the event horizon, so an astronaut may cross the event horizon without noticing any squashing and pulling, although it remains only a matter of time, as once inside an event horizon, falling towards the center is inevitable. For small black holes whose Schwarzschild radius is much closer to the singularity, the tidal forces would kill even before the astronaut reaches the event horizon. http://en.wikipedia.org/wiki/Spaghettification

I have already made a different thread for that problem in Suggestions, Comments and Support: Changeable Votes of Reputation For a short duration after voting

Actually with Moontanman's and Michel's suggestions we have four issues. The other two are: 3. The most suitable limit of negative votes each day 4. The possibility to view how many votes made on any post

Yes, that would be nice, but it could also be showed with votes made, like in the example Rep:0 Votes:6 or maybe 0(6).

What is so funny with an assured catastrophe? Your argument sounds like you think a blast from a shotgun is harmless to you, because you have survived the sunlight for your whole life. The amount of energy released by a single large collision or many small collisions is essentially the same, given the physics of kinetic and potential energy. http://en.wikipedia.org/wiki/Asteroid-impact_avoidance I don't think such nuclear bombs are supposed to explode far from the asteroid, more likely they are set to detonate on impact or inside it. Detonating a nuclear explosion above the surface (or on the surface or beneath it) of an NEO would be one option, with the blast vaporizing part of the surface of the object and nudging it off course with the reaction. This is a form of nuclear pulse propulsion. Even if not completely vaporized, the resulting reduction of mass from the blast combined with the radiation blast and rocket exhaust effect from ejecta could produce positive results. http://en.wikipedia.org/wiki/Asteroid-impact_avoidance

A water analogy can be useful in understanding resistance, water pressure is voltage potential and water flow is electrical current. The battery is a pump increasing pressure, the rheostat is a valve choking the flow and the lightbulb is a waterwheel powered by the flow of water. Unless the circuit is fatal for the battery and rapidly exhausting it, it will keep the voltage fairly constant independent of the load. In the analogy the pump is assumed to keep a constant pressure before the valve independent of it is fully open or closed. The rheostat is a variable resistance throttling the electrical current through it depending on the voltage drop over it. In the analogy the valve strangles the flow of water by closing the hole water is passing through, causing a pressure drop over it. The lightbulb is also a resistor where the electrical current are choked by its resistance depending on applied voltage. In the analogy the waterwheel will oppose the movement and cause the water flow to slow down, a higher pressure will cause a higher flow. Therefore by reducing the resistance you are opening the valve and a larger hole will allow more water to pass. Since more water are allowed to reach the intake of the waterwheel, the pressure pushing water through it will increase, which will cause a greater flow. The waterwheel will start to spin faster or the lightbulb will shine brighter.

But then you could feel too guilty to vote negative on a bad post that person makes later on, at least I would... I agree with this one too, I have refrained from voting positive because I was discouraged by the member's begging for rep in their signature.