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Old 02-26-2017, 05:06 PM
 
Location: Western U.S.
375 posts, read 188,519 times
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Quote:
Originally Posted by irman View Post
Then when you get there, you may find it is not there anymore ...
What did you see when you started out 200,000 years back ?
Whatever you saw, took 200,000 years to get to *you*, then another 200,000 years for you to get there, that is 400,000 years ...

Aw shucks ...
At least more fun to dream about stuff like this then to think of even more stupid things to say about our politicians ...
This is true. About how that star you set out for on the other edge of the galaxy could have expired by the time you reach it.

But it's very unlikely. Since 100,000 years is a drop in the bucket for an average star. As they often live for billions of years. Like our sun, which at 4.6 billion years of age is about half way through its life.

So a couple hundred thousand years is one fifth of a million, which is one one-thousandth of a billion.

So it's like a couple days to a guy who lives to be 100.

Thus, odds are in your favor that the star would be there. Like going to visit a 100 year old, what are the odds you happen to leave to see him on the day before he died, when you can visit him anytime during his life?
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Old 02-27-2017, 12:24 PM
 
Location: God's Gift to Mankind for flying anything
5,374 posts, read 11,281,537 times
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Awww Guess I wont go then, I do not have to time sit around for that many years ...

I get impatient to wait for that 2 minute hot water in my cup from my Microwave oven .

Still fun to talk about things that do not get anywhere !
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Old 03-02-2017, 06:01 PM
 
Location: Houston, Texas
1,178 posts, read 1,354,453 times
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Quote:
Originally Posted by LAX Star View Post
Exactly!

The closest star (actually a binary 2-star system) to Earth--excluding our own sun of course, which is simply a very average main sequence star--is the Proxima Centauri system. It is 4.3 LY away from us. So, at speed-of-light travel it would STILL take a tad over four years to get there! Mind boggling, ain't it! Take a look at a pic of our Milky Way Galaxy and see all those stars! There are about 200 billion or so. And to think that just the closest one of those is over four light years away.

At speed of light travel (solt) it would take about 200,000 years just to cross our Galaxy from edge to edge!

And to wit: there are hundreds of billions of other galaxies.

Our sun is a mere 93 million miles away. The light from it to reach us here on Earth takes about 8 minutes. That distance is called an Astronomical Unit. (AU).

OF course we currently have no propulsion technology capable of reaching anywhere near light speeds. And we probably never will. At present, with our bestest fastest technology, it would take us nearly 12,000 years to reach Proxima Centauri.

And yes....I a Cosmology nerd! LOL
What type of tech would get us to Alpha Centauri in 12,000 years? I've read with our current tech it would take 165,000 years. With nuclear pulse propulsion it would take 60 years and its theorized that with antimatter engines you can reach speeds between 50%-80% the speed of light. We still don't have either nuclear pulse propulsion or antimatter engines
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Old 03-02-2017, 10:26 PM
 
Location: Type 0.7 Kardashev
10,576 posts, read 7,459,514 times
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Quote:
Originally Posted by Canaan-84 View Post
What type of tech would get us to Alpha Centauri in 12,000 years? I've read with our current tech it would take 165,000 years. With nuclear pulse propulsion it would take 60 years and its theorized that with antimatter engines you can reach speeds between 50%-80% the speed of light. We still don't have either nuclear pulse propulsion or antimatter engines
The fastest man-made object is NASA's Juno spacecraft, which reached a velocity of ~165,000 mph en route to Jupiter. At that rate, it would take 23.5 days to get to the nearest star from Earth. Of course, the nearest star to Earth is the Sun.

That pace would require over 18,000 years to get to where the next nearest star is now - Proxima Centauri, the smallest member of the Alpha Centauri system, lying 4.2 light-years away. In reality, since Proxima Centauri is currently moving in a closing direction relative to the Sun and will be about 3.5 light-years distant in 18,000 years, it would take Juno somewhat less time to get there if it had been pointed in an intercepting direction.

Note:
In about 28,000 years (at which point the co-orbital Alpha Centauri A & B will be closer to the Earth than Proxima Centauri - the latter orbits the former in a period of roughly 500,000 years, while the two primary stars orbit about each other every 80 years), the Alpha Centauri system will reach its closest approach to the Sun and will then slowly begin to recede from our home star. In a little over 30,000 years, Ross 248 - a red dwarf - will become the nearest extrasolar star. Somewhat beyond 40,000 years, Gliese 445 - another red dwarf - will be the nearest star. And then, over 50,000 years from now, because Ross 248 and Gliese 445 are on more elliptical trajectories, Alpha Centauri - though still receding from the Sun - will again be our closest stellar companion.

Another note:
Alpha Centauri is the name of the nearest star system to the Sun. It consists of three stars - Alpha Centauri A (a little bigger than the Sun), Alpha Centauri B (a little smaller than the Sun), and Alpha Centauri C (usually called Proxima Centauri, as it is the most proximate star to our own star, a red dwarf which is much smaller than the Sun). So remember - Alpha Centauri is not a star but a star system, of which each star has its own designation.
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Old 03-02-2017, 11:20 PM
 
Location: Houston, Texas
1,178 posts, read 1,354,453 times
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Quote:
Originally Posted by Unsettomati View Post
The fastest man-made object is NASA's Juno spacecraft, which reached a velocity of ~165,000 mph en route to Jupiter. At that rate, it would take 23.5 days to get to the nearest star from Earth. Of course, the nearest star to Earth is the Sun.

That pace would require over 18,000 years to get to where the next nearest star is now - Proxima Centauri, the smallest member of the Alpha Centauri system, lying 4.2 light-years away. In reality, since Proxima Centauri is currently moving in a closing direction relative to the Sun and will be about 3.5 light-years distant in 18,000 years, it would take Juno somewhat less time to get there if it had been pointed in an intercepting direction.

Note:
In about 28,000 years (at which point the co-orbital Alpha Centauri A & B will be closer to the Earth than Proxima Centauri - the latter orbits the former in a period of roughly 500,000 years, while the two primary stars orbit about each other every 80 years), the Alpha Centauri system will reach its closest approach to the Sun and will then slowly begin to recede from our home star. In a little over 30,000 years, Ross 248 - a red dwarf - will become the nearest extrasolar star. Somewhat beyond 40,000 years, Gliese 445 - another red dwarf - will be the nearest star. And then, over 50,000 years from now, because Ross 248 and Gliese 445 are on more elliptical trajectories, Alpha Centauri - though still receding from the Sun - will again be our closest stellar companion.

Another note:
Alpha Centauri is the name of the nearest star system to the Sun. It consists of three stars - Alpha Centauri A (a little bigger than the Sun), Alpha Centauri B (a little smaller than the Sun), and Alpha Centauri C (usually called Proxima Centauri, as it is the most proximate star to our own star, a red dwarf which is much smaller than the Sun). So remember - Alpha Centauri is not a star but a star system, of which each star has its own designation.
I see, did not know they had used a faster propulsion system. Assumed it had not changed since Voyager 1 at 38,000+ mph reached Jupiter in 2 years and it took Juno 5 years to reach Jupiter; I assume Juno had other missions before reaching Jupiter for it to have taken much longer to get there. It was launched in 2011 but in 2013 was still within Earth's vicinity as that year it used Earth for a Gravity assist to slingshot it towards Jupiter. Which still doesn't make sense since it took Juno nearly the same amount of time to reach Jupiter as Voyager 1, even though it was traveling more than 4 times faster.
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Old 03-04-2017, 08:02 PM
 
Location: Type 0.7 Kardashev
10,576 posts, read 7,459,514 times
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Quote:
Originally Posted by Canaan-84 View Post
I see, did not know they had used a faster propulsion system. Assumed it had not changed since Voyager 1 at 38,000+ mph reached Jupiter in 2 years and it took Juno 5 years to reach Jupiter; I assume Juno had other missions before reaching Jupiter for it to have taken much longer to get there. It was launched in 2011 but in 2013 was still within Earth's vicinity as that year it used Earth for a Gravity assist to slingshot it towards Jupiter. Which still doesn't make sense since it took Juno nearly the same amount of time to reach Jupiter as Voyager 1, even though it was traveling more than 4 times faster.
Voyager 1 took 18 months to travel from Earth to Jupiter - launch to Jupiter fly-by (September 1977 to March 1979).

Juno took 33 months to travel from Earth to Jupiter - Earth fly-by to Jupiter orbital inserton (October 2013 to July 2016).

That's less than 2x faster for Voyager 1. Since Juno was launched into a solar orbit, and only later was redirected towards Jupiter, the part of the mission prior to heading toward Jupiter obviously cannot be counted as time it took to get to Jupiter from Earth.

There are also other mission variants. Voyager 1 was launched on a Titan III, which produced more than 3x as much thrust as the Atlas V which launched Juno. And Jupiter is not some object with a fixed distance from Earth. Both orbit the Sun in their elliptical orbits, aligning at different points in their respective orbits. No two missions will be the same.

Also of note is the fact that Voyager 1 was a fly-by mission, whereas Juno entered Jovian orbit. Orbital insertion requires fuel for a deceleration burn, and the faster the spacecraft travels en route, the more fuel it has to carry in order to brake upon arrival at its destination. Voyager 1 only needed to carry small amounts of fuel for brief trajectory-correction burns. It is straightforward spacecraft design economics to require less fuel for the insertion burn by not flinging the spacecraft as hard at its target as one possibly can.
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Old 03-05-2017, 01:06 AM
 
Location: Houston, Texas
1,178 posts, read 1,354,453 times
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Quote:
Originally Posted by Unsettomati View Post
Voyager 1 took 18 months to travel from Earth to Jupiter - launch to Jupiter fly-by (September 1977 to March 1979).

Juno took 33 months to travel from Earth to Jupiter - Earth fly-by to Jupiter orbital inserton (October 2013 to July 2016).

That's less than 2x faster for Voyager 1. Since Juno was launched into a solar orbit, and only later was redirected towards Jupiter, the part of the mission prior to heading toward Jupiter obviously cannot be counted as time it took to get to Jupiter from Earth.

There are also other mission variants. Voyager 1 was launched on a Titan III, which produced more than 3x as much thrust as the Atlas V which launched Juno. And Jupiter is not some object with a fixed distance from Earth. Both orbit the Sun in their elliptical orbits, aligning at different points in their respective orbits. No two missions will be the same.

Also of note is the fact that Voyager 1 was a fly-by mission, whereas Juno entered Jovian orbit. Orbital insertion requires fuel for a deceleration burn, and the faster the spacecraft travels en route, the more fuel it has to carry in order to brake upon arrival at its destination. Voyager 1 only needed to carry small amounts of fuel for brief trajectory-correction burns. It is straightforward spacecraft design economics to require less fuel for the insertion burn by not flinging the spacecraft as hard at its target as one possibly can.
I said 4 times faster because you said Juno speeds were 165,000 mph while Voyager 1 speed is 38,000 mph, wasn't counting the times that Juno was orbiting the Sun or Earth. Yes I know Jupiter is not stationary but at 4X the speed, you would think it would have given it a major advantage.
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Old 03-05-2017, 09:48 AM
 
Location: On the road
2,684 posts, read 2,042,528 times
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Speed and distance are relative in space. Trajectories are often non-linear. Even a trip to the moon requires a non-linear trajectory.
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