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Re: Long trips
Bert22306   7/25/2014 9:12:58 PM
Good point. I had ignored the Lorentz Transformation because we're still talking about very low speeds, at 1/20 c.

So okay, while on earth everyone will have aged 84.8 years, by the time you reach Proxima Centauri, those on the spaceship will "only" have aged a little less than 83.1 years.

The other point is, we could postulate that if you can get close to c, then you really wouldn't need to go any faster. Because even though the rest of the universe is aging really fast as you travel, you aren't. So you might say, the traveler should be prepared to leave everything else behind, and never go back to what he knew, but at least he can survive a journey lasting many thousands of years, say.

Okay, but that pesky Lorentz Transformation also applies to mass. Which means that to accelerate the vehicle to relativistic speeds, it will take huge amounts of energy. So for example, assume you travel at a way faster 0.9c, the mass of your spaceship will be 2.3X as great as when it's at rest, and you will age 43.6 percent as much as if at rest.

And that's already up at 0.9c. So to really take advantage of time dilation, since even 0.9c doesn't buy you a whole lot on a journey of 20,000 light-years, you would have to really really pay a price on energy required.

Conclusion: we need to find a way around the speed of light.

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Re: Long trips
y_sasaki   7/25/2014 8:57:24 PM
Einstein's relative theory says if the object speed near the speed of light, the time on that moving object slows down from "still" observer. It is called Lorentz Transformation. Equasion of Lorentz factor is




Where v=speed of object, c=speed of light.

When v=0.2c, gamma is 1.02. The clock inside the space ship slows down (relative to clock on "still" Earth). only only 2%. It would not make 84.8yers (on Earth) to 20 years (on the space ship)...

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Long trips
Bert22306   7/25/2014 5:02:32 PM
First, I quibble with this point:

Worden said an anti-proton pulse could propel space travel at speeds up to one-twentieth of the speed of light, making it possible to complete the journey to the nearest star system in 20 years.

The closest star system is Proxima Centauri, 4.24 light-years distant. If your space ship can truly travel at a constant 1/20 * c, I mean not at its peak speed but steady state, then it would take 84.8 years to get there, as opposed to 20.

If you take our fastest space vehicle to date, Voyager 1, approximately 17.3 Km/sec, it would take more than 73,200 years to reach Proxima Centauri, and more than 75,000 years to reach Alpha Centauri. Both trips would take longer than mankind has been in existence - almost twice as long as homo sapiens has been around. These are the closest stars to us, amazingly enough.

So yeah, we definitely need to go a whole lot faster, and even to "bypass" the speed of light somehow or other. Space warps, wormholes, anything that allows us to find shortcuts between points A and B, through higher dimensions. Star systems that are of interest to us, that we have already detected, are multiple thousands or millions of light-years away. IIRC, the closest potentially earth-like planet we know about is 12 light-years away, and there are numerous within 50 light-years. Those numbers imply right next door, but they really aren't!

As to fussing only with the closest planets or the moon, you know guys, if the cavemen had thought that way, we'd still be living in caves. You have to invest in more than just what's needed for tomorrow. Because the answers to what might appear to be intractable problems might just come from what we don't know or have experienced yet.

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Re: Moon Base
chrisnfolsom   7/25/2014 12:50:53 PM
I agree, but the first issue is making it to orbit easily and without so much chemical energy.  I believe using an electric catapault to get small packages up near orbit and using much less rocket power to get the rest of the way would be the best way to speed things along - use Elon's vacuume tube transport technology and go up the side of a mountain a few miles long at 4000mph you are 1/4 of the way to escape velocity and arguably the hardest 1/4 of the flight.

Smaller non-living or non-g-force limited packages could be sped up and launched at much higher speeds and assembled in orbit.

Sending packages to space should be routine by now - and the bonanza of metals, materials processing and who knows what else would be much more accessible.

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Re: Moon Base
docdivakar   7/25/2014 10:47:19 AM
@Wnderer & @kris: ditto... going to the moon may become a dire necessity in a couple of generations when we run out of resources like minerals. NASA / human race pooling together should focus on cost effective ways to run moon missions!

MP Divakar

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Re: Moon Base
krisi   7/25/2014 10:32:38 AM
I agree...why people are so obsessed with going so far...focus on solving problems at home (moon is the closest to experiment)

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Moon Base
Wnderer   7/25/2014 9:21:11 AM
I rather see NASA focus on missions closer to home. We should return to the Moon. The Moon is great platform for gravity wave detectors, neutrino detectors, and telescopes. A radio telescope on the Moon linked to radio telescopes on Earth would make a telescope with an effective aperature of the distance between the Earth and the Moon.  We should build a Moon base with robots and a couple of astronauts to monitor and repair these experiments. The secrets of the universe are right there.

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