NowThatWeKnow

I am far from an expert but I did find this. Remember visible light is only a small portion of the EM range. http://en.wikipedia.org/wiki/Uranium-238 "Uranium-238 is also used as a radiation shield — its alpha radiation is easily stopped by the non-radioactive casing of the shielding and the uranium's high atomic weight and high number of electrons is highly effective in absorbing gamma rays and x-rays. However, it is not as effective as ordinary water for stopping fast neutrons. Both metallic depleted uranium and depleted uranium dioxide are being used as materials for radiation shielding. Uranium is about five times better as a gamma ray shield than lead, so a shield with the same effectivity can be packed into a thinner layer."

Different frequencies are very different. X-ray is an electromagnetic radiation you are familiar with that penetrates and then you have gamma rays.

More then just cameron would benefit from you (or anyone else) putting it into layman terms. Two frames are doing the same thing relative to each other so what determines which twin stays younger? It seems that acceleration, deceleration and gravitational potential are the only differences to be considered. I recently read where the clock speed differences are consistent during a trip and do not happen at one point.

But one twin is older then the other when they reunite.

You are not alone. As many times as I have read about the twins, it still confuses me. I was reading an article just yesterday about time differences between two inertial frames with no acceleration involved. I thought that acceleration is what broke the symmetry between the clocks but now I am not so sure. How else would you know who is traveling and who is at rest?

There is a difference in clocks running at different speeds and stopping the clock. The twin story I read said the difference in age was years, not seconds. http://www.phys.unsw.edu.au/einsteinlight/jw/module4_twin_paradox.htm

Maybe not simple and far from fact but it is easier to think about than a universe with a boundary or one without.

Quantum theory = very small Infinite universes = very large plus pure speculation This thread may experience a relativistic ride. Welcome Maybe we are the "cursor".

Very interesting but with a lot of unknowns. I wonder if these massive black holes may be another source for heavy elements in the galaxy. It would seem there would be plenty of pressure and energy for developing them and the jets could disperse it.

You can find all sorts of things over in the "speculation" section. Other areas of this forum require something to back them up like math or observations.

I guess you already absorbed all the information in the link iNow posted?

I can see where "illusion" may not fit much of the time. When two frames meet, the results will not be an illusion. Thanks for the replies.

Exactly, the kinetic energy and relativistic mass are equally varible depending on what you are comparing your speed to.

You may be right and I was confused by "but can we move something "negatively" somehow? so a reference points ages faster than another reference point moving at normal speeds?" If so he was sort of answering the question before he asked it.

It makes it sound like gamma [math] y[/math] is some kind of resistance in space despite the fact that a continuous 1G acceleration will cover more distance at a faster and faster rate according to your clocks on the ship. Earth time is the one that seems to be stuck at the speed of light. That could be a relevant factor on a trip.

Someone please correct me if I am wrong but I would guess that gravity 4000 miles from the black hole would be similar to gravity at the earths surface. A new set of rules apply as you get closer to the black hole. Going towards the center of the earth your weight would decrease and getting closer to the black hole your weight woud increase. All bets off when you get close to the black hole. Again, corrections welcome if needed. Edit - I love it when I am right. finally http://amazing-space.stsci.edu/resources/explorations/blackholes/teacher/sciencebackground.html#5

A variable value that is only relative to someone else does not seem very relevant. Unless maybe when you are using a particle collider.

Traveling back in time takes advance planning. If you want to come back to 2010 in 2020 you could send Earth on a relativistic trip now and wait on Mars for it's return. As mentioned, you could do the same with gravity. But even if you could ignore the gravity of the Sun and Earth you would only go ahead in time by about 1 minute a year. As Baby Astronaut says, "unless my calculations are totally screwy"

A black hole could have the mass of the Earth or millions of stars. A black hole with the mass of Earth would have a similar gravity as Earth. And I would think a similar time dilation. I have a feeling that stopping time is like reaching the speed of light. You will never quite get there.

If relativistic mass is only seen by an observer outside of the particular frame in question, it must be an illusion. You could have several inertial frames moving about at different speeds and no one could agree on the relativistic mass of each one, yet they would all agree that their own mass is at rest.

NASA Foilsim will let you calculate lift with different angles of attack, airfoil size, camber and speed. Change the "Input" field for different options. http://www.grc.nasa.gov/WWW/K-12/airplane/foil2.html The lithium ion battery would give the most power for weight and is used in radio control aircraft with excellent success. It does get pricey as the size goes up.

I agree. A one kilogram rock equivalent to [math]8.98755179 * 10^{16} joules[/math]. As mentioned, antimatter is our only hope.

Your head ages faster then your feet and they share the same "now". "...sound like an Abbott & Costello bit." Yep

The definition of "now" http://www.einstein-online.info/en/spotlights/Now/index.html "two events are simultaneous if and only if they can be seen on the same photograph, taken with a double camera placed exactly in the middle between their locations."

I resemble that remark.