Consider a pair of brothers, identical twins. One gets a job as an astronaut and rockets into deep space. The other stays on Earth. When the traveling twin returns home, he discovers he's younger than his brother. This is Einstein's Twin Paradox, and although it sounds strange, it is absolutely true. The theory of relativity tells us that the faster you travel through space, the slower you travel through time. Rocketing to Alpha Centauri—warp 9, please—is a good way to stay young. Or is it? Some researchers are beginning to believe that space travel could have the opposite effect. It could make you prematurely old. "The problem with Einstein's paradox is that it doesn't fold in biology - specifically, space radiation and the biology of aging," says Frank Cucinotta, NASA's chief scientist for radiation studies at the Johnson Space Center. While the astronaut twin is hurtling through space, Cucinotta explains, his chromosomes are exposed to penetrating cosmic rays. This can damage his telomeres—little molecular "caps" on the ends of his DNA. Here on Earth, the loss of telomeres has been linked to aging.

So far, the risk hasn't been a major concern: The effect on shuttle and space station astronauts, if any, would be very small. These astronauts orbit inside of Earth's protective magnetic field, which deflects most cosmic rays. But by 2018, NASA plans to send humans outside of that protective bubble to return to the moon and eventually travel to Mars. Astronauts on those missions could be exposed to cosmic rays for weeks or months at a time. Naturally, NASA is keen to find out whether or not the danger of "radiation aging" really exists, and if so, how to handle it.

View: Full Article | Source: Physorg.com

This whole concept has always bothered me. One brother stays on Earth and watches the ship fly away at nearly the speed of light. Fine. The problem is that the other brother "stays still" and watches Earth fly away from his apparently stationary ship. Earth and the ship move apart relative to each other. Neither one moves relative to its own frame of reference. Why would one age and the other wouldn't? Both are experiencing the same thing.

I really think it has more to do with accelleration. I don't think a constant velocity will distort space-time.

But I do agree with this article.

if we used electromagnetic-flux propulsion devices we wouldn't have this problem

and if we had the technology to make suits that deflect these penetrating rays it, again, wouldn't be a problem

- Jesus Christ

Actually they aren't experiencing the same thing because they have different frames of reference. This is the whole basis of relativity. Each will see their watches moving at the normal rate but each would see time moving differently for the other.
The effect of time dilation may be counter to intuition but is measurable. The effect is brought about by the fact that light always travels at the same speed regardless of the speed of the observer. For this to be true then time has to run at different speeds for the different observers. This theory has been tested out in particle accelerators. Certain sub atomic particles have a short but constant life time. If Einstein is right then if the particles are accelerated to relativistic speeds (speeds which are a significant fraction of the speed of light) then from the point of view of the stationary observer the particles should live longer. (From the point of view of the particles they are decaying at exactly the same rate). When these experiments have been carried out thee particle life expectancy has increased exactly as predicted by Einstein.

The title of this article is a bit deseptive as Einsteins twin paradox was never meant to take into account biological proceses. Think of another example involving twins. One of them eats healthily, goes to the gym, doesn't smoke and stays out of the sun. The other eats badly, doesn't exercise, smokes and spends far to long trying to get a tan. The second twin would have been aged by biological processes but would still be the same age as his twin. This is because biological aging is not wholly influenced by actual age. It doesn't mean that Einstien was wrong it just means that there are other factors which need to be taken into account.

Maybe, but I thought it still works if the ship accelerates very fast, then coasts at almost c for a long time. The time spent accelerating can be much shorter than the time spent coasting.

I find this paragraph very interesting, here they are saying that they want to know the effect of the radiation on humans. Now how many missions have been sent to the moon, would not all the astronauts on these missions be the best indicators of the effect, or didn't they go to the moon? Is the cosmic radiation too dangerous for man to go outside our protective magnetic field without proper protection? What protection will the new space ships and suits have when they are sent to the moon in 2018? I don't know, but I think that it is a bit dodgy that they didn't think about this before, back when the first moon landings where suppose to of happened. Now I know that not many people knew about or what was cosmic radiation, but I believe NASA did. So what protection did they give the original astronauts to go to the moon with, it seems that the more I think about it the more unanswered questions I get.


I totally agree Waspie_Dwarf

The effects of radiation are cumulative. Humans can survive large radiation doses for short periods of times. However smaller radiation doses can cause problems over long periods. The Apollo astronauts spent only a few days outside of the Van Allen belts and so, although exposed to higher radiation doses than normal it was not for long enough to lead to radiation sickness.

NASA's plans for a return to the moon and then on to Mars will eventually lead to astronauts spending months in these raised levels of radiation and so, unless the astronauts are shielded, will greatly increase their chances of cancer.

Another problem is solar storms. These do pump out enough radiation to incapacitate or kill an astronaut in a very short period of time. NASA always knew that if a solar storm hit during an Apollo mission they would lose the crew. By luck no such storms hit during the 9 missions which flew beyond the Van Allen belts. In the case of long duration missions (which will last months) to the moon and Mars it is almost certain that such storms will hit the crews. Hence the crews will need radiation shelters to protect themselves during such periods.

The lack of radiation protection in the Apollo era and the need for it in the future are not inconsistent with America having been to the moon in the late '60's and early '70's.

Cheer's Waspie_Dwarf that was a good response.

Interesting...

TeraLink Was Here!

Thanks, Waspie_Dwarf, for the crisp and informative responses.

Cosmic rays are the nuclei of atoms, accelerated to far higher energies than can be achieved by human accelerators. Shuttle astronauts can close their eyes and see continual streaks made by these nuclei. Earth's magnetic field doesn't deflect cosmic rays. We are protected only by the 10 miles of air over our heads.

Neither interstellar nor interplanetary flight is possible by technology. If the cosmic rays don't kill you, the prolonged weightlessness will. After only 5 days of weightlessness, the astronaut has lost 30% of his muscle mass, although this loss can be reduced by rigorous exercise 2 hours a day, using bungee cords to provide some artificial gravity. NASA should be closed down. It is a complete waste of time, money, and lives.

~~~Cebrakon

High energy cosmic rays are actually gamma rays not atomic nuclei. The solar wind does contain atomic nuclei however and it is possible to shield against them. Interplanetary flight is perfactly achievable by technology. Soviet cosmonauts have spent periods in excess of 1 year in weightlessness without an lasting ill effects.

Not the same gravity fields.