Distant Galaxies

[garyclaytonpalmer]

If all the galaxies in the known universe are so far away and we cannot travel the speed of light, will mankind ever be able to visit one or any of them? At current available speeds what is the quickest we could get to the closest galaxy?

[apodman]

Closest major galaxy (M31) is 2,400,000 light years distant.
At 1/20,000 of the speed of light, we can get there in 48,000,000,000 years.

Closest visible galaxy (Large Magellanic Cloud) is 180,000 light years distant.
At 1/20,000 of the speed of light, we can get there in 3,600,000,000 years.

Sagittarius dwarf galaxy (http://antwrp.gsfc.nasa.gov/apod/ap970329.html) is 60,000 light years distant.
At 1/20,000 of the speed of light, we can get there in 1,200,000,000 years.

Canis Major dwarf galaxy (http://antwrp.gsfc.nasa.gov/apod/ap071104.html) is 42,000 light years distant.
At 1/20,000 of the speed of light, we can get there in 840,000,000 years.

In any of those time frames, we might not still be recognizable as mankind.

[garyclaytonpalmer]

So I guess my question is, Being the size of the universe I guess all we ver will do as humans is look at it from our telescopes and be amazed by its splender and send robotic missions to distant worlds.
May there be any worlds outside our solar system we can go to other than the nine known planets?

[Chris Peterson]

So I guess my question is, Being the size of the universe I guess all we ver will do as humans is look at it from our telescopes and be amazed by its splender and send robotic missions to distant worlds.
May there be any worlds outside our solar system we can go to other than the nine known planets?

If we ever developed a truly stable civilization, visiting other stars isn't all that challenging. It doesn't even take a million years to get to every star in the galaxy.

The fact that we don't have any visitors from other stars is one reason for believing that stable, long-lived civilizations may not exist.

[apodman]

There are plenty of extrasolar planets within a few dozen light years of Earth, some less than 10 light years away. Even so, increasing our speed by a factor of 100 to 1/200 of the speed of light would mean a one-way trip of 2000 years, so it would be a multi-generational mission. But I'm going to go out on a limb and say that spacecraft speeds of a large fraction of the speed of light will be possible some day, and that we will at least be able to send robotic probes to extrasolar planets that can transmit information back to us within a single lifetime. If we find a nice planet, why not send humans eventually? But we have plenty to explore in our own solar system first, and haven't even gotten people to Mars yet. And high speed space travel has a lot of technical problems besides getting the speed; for one thing, hitting a piece of dust at 100,000 miles per second would be devastating, so start designing you deflector dishes now.

[bystander]

How long would it take assuming a 1 g acceleration to halfway, and 1 g deceleration for the remainder?

[The Code]

We must understand more and work out how to cover those distances in a realistic ''Time'' frame. There is no other way.

Mark

[garyclaytonpalmer]

How do we know we are not extraterrestrials, coming here thousands of years ago, placed here by ancestors from another world to study the planet and make way for ourselves to eventually go to other worlds? Maybe we came here not realising our presence on what we call Earth would be so destructive to the major existence of every other creature and thing on Earth.
Or maybe by learning of this planet we have not been able to control our nature and we fight each other and take more from the world than we have learned to give back. Maybe in time we will learn to recycle the things we use of this planet and be able to put everything back as our extraterrestrial ancestors found it many years ago. Then either they will return or we will go out and seek them and find out why no other aliens have come here. Maybe other cultures from other galaxies have learned the lessons of their own worlds and don't think its safe to interfer with other worlds.
I often wonder what it was like for early man, and all the cultures of the world before technology allowed other humans like the Spanish or self appointed religons to travel the world and destroy cultures simply because they would not convert to Christianity. The American Indians that were here for thousands of years living semipeacefully with nature had it made. I wonder with no outside influence if they would have ever built a culture that would go to other countrys by ships or ever evolve to space travel.
Why did european man evolve to build vessels to take them around the world while most Indians were still in the stone age when the Spanish arrived?
I don't mean to get off my origianl subject of space travel, but our ancestors may have known about aliens coming here from other worlds, but with out proper decyphering of their stone writtings we may never know the truth. many cultures have ancient petrigylphs showing odd images of beings not of this world. Or maybe they just drew cartoons like we do of imaginary charactors?

[garyclaytonpalmer]

One said about a realistic Time frame. Thats what a stone age man would have said to his grandson when he had a dream about television tech. Imagine a time when new tech was not the vogue. At one time humans could barely imagine finding a new food source like planting instead of just harvesting. Now we can't imagine being able to advance the speed of light or build ships strong enough to withstand supersonic dust particles. maybe I am sure possibly future man will builf new metal alloys that will be stronger and better than even the current Titanium metals.

[The Code]

How do we know we are not extraterrestrials, coming here thousands of years ago, placed here by ancestors from another world to study the planet and make way for ourselves to eventually go to other worlds?

Because we can trace the human DNA back 47 million years, when we looked more like dogs with tails. Stone age man, could not comprehend extracting iron out of rocks , so i doubt anybody them days, dreamed of 20th Century Tech.. As for light speed travel... Small potatoes.. http://www.youtube.com/watch?v=JANwVq018C4

Mark

[apodman]

How long would it take assuming a 1 g acceleration to halfway, and 1 g deceleration for the remainder?

My relativity is rusty and my book is in a box, but I think 1 g acceleration would give you less return in velocity as you got closer to the speed of light. For a ballpark estimate, however, let's pretend you could accelerate at 1 g until you got to the speed of light. Your acceleration (=a) would be 9.8 m/sec². Your velocity (=at) after a year would be (9.8 m/sec²)(3.16E7 sec)=3.1E8 m/sec. The speed of light is 3E8 m/sec, so shortly before a year was up you would have attained maximum velocity. Your distance traveled (=½at²) would be (½)(9.8 m/sec²)(1E15 sec²)=4.9E15 m or about ½ light year. So in rough terms, you could take a year of 1 g acceleration at the beginning of your trip (traveling ½ light year) to get to cruising speed, coast at high speed for the long middle of your trip, and take another year (traveling ½ light year) at the end of your trip to decelerate. So if you could travel arbitrarily close to the speed of light, the time for your trip would be 1 year each for the first and last half light years and 1 year for each light year in between, or 1 year more in total time than the distance in light years.

[harry]

G'day rom the land of ozzz

To dream.

This is what made man create what ever.

To travel to another star, it's just another dream.

Where there is a WILL there is a way.

It's not about how fast you can travel, it's a matter of how you can survive the trip.

[Chris Peterson]

So if you could travel arbitrarily close to the speed of light, the time for your trip would be 1 year each for the first and last half light years and 1 year for each light year in between, or 1 year more in total time than the distance in light years.

That would be the duration of your trip in the reference frame of your origin. In your own frame, the duration is much less. You can go many light years in much less than years if you can accelerate continuously.

[William Roeder]

How long would it take assuming a 1 g acceleration to halfway, and 1 g deceleration for the remainder?

My relativity is rusty and my book is in a box, but I think 1 g acceleration would give you less return in velocity as you got closer to the speed of light.

I actually did the calculation when my relativity was fresh. What you wrote was correct, but if you continue to accelerate your clock slows down dramatically. Thus you can reach anywhere in the universe in 25 years. Double it since you have to slow down. Of course a trip of N light years (N>>2) 2N years would have passed on Earth.

[apodman]

... if you can accelerate continuously.

Carrying and accelerating the fuel to do that is the problem. I suggest we come up with an ingenious method of liberating quarks just in time to project them backward to push the spaceship forward. That way we get action-reaction from the greater mass contained within the lower mass protons and neutrons we carry. Just my quantum fantasy talking.

---

Time dilation is fine for the explorers themselves, but the longer time that passes on Earth during the spaceflight matters to us folks back on Earth who are waiting for the report.

[Chris Peterson]

Carrying and accelerating the fuel to do that is the problem.

Fuel's no problem, because you don't have to carry it. You can scoop it up all around, and the faster you go, the more there is. The problem is energy. It takes a LOT of energy to accelerate continuously. Really, really a lot.

[astrolabe]

Hello All,

Fun food for thought and a good subject for mental gymnastics! I remember seeing an "Our Gang" (Little Rascals) episode once where two little kids in a homemade soapbox-derby-type vehicle had in their possession a very large horseshoe magnet by which they were able to get around town by aiming it at a car and off they would go! Change direction? No problem, just aim at another car going the other way.

If one believes that gravity is an attractive force then maybe just "surfing " gravity waves, which theoretically propagate at c, would do the trick.

[Chris Peterson]

Hello All,

Fun food for thought and a good subject for mental gymnastics! I remember seeing an "Our Gang" (Little Rascals) episode once where two little kids in a homemade soapbox-derby-type vehicle had in their possession a very large horseshoe magnet by which they were able to get around town by aiming it at a car and off they would go! Change direction? No problem, just aim at another car going the other way.

If one believes that gravity is an attractive force then maybe just "surfing " gravity waves, which theoretically propagate at c, would do the trick.

I think the problem here is the extremely low energy available in gravity waves, even assuming you found some way to tap it. Also, while gravity is easily modeled as an "attractive force", it is actually a distortion in spacetime- something that is particularly apparent when looking at gravity waves. If you were in a pond with a big drain in it, you would sense some "attractive force" on you when near the drain. But if you were elsewhere in the pond, with tiny ripples on the surface moving in all different directions, what "force" would you feel other than a sort of Brownian chop? How would you use those ripples to move yourself?

[apodman]

I remember seeing an "Our Gang" (Little Rascals) episode once where two little kids in a homemade soapbox-derby-type vehicle had in their possession a very large horseshoe magnet by which they were able to get around town by aiming it at a car and off they would go! Change direction? No problem, just aim at another car going the other way.

Diet Smith, inventor of the two-way wrist radio, made this Magnetic Space Coupe (which operated on the principle described above) for Dick Tracy:



---

On an old Saturday morning cartoon show, probably Scooby Doo, in one episode the evil Dr. Shaman used a giant horseshoe magnet to pluck satellites out of orbit. The magnetic device was named the "Shaman U".

[The Code]

How about we make a star ship, with a proper warp engine?

http://en.wikipedia.org/wiki/Warp_drive

http://worldofweirdthings.com/2009/05/1 ... arp-drive/

Mark

[garyclaytonpalmer]

Man need not be able to know how to take iron from rock to have dreams of doing the imaginable. Have you never dreamed of flying like superman, or being able to walk on the moon? I think early man having seen the moon could have imagined being able to go there somehow. He dreamed up the idea of God's and making things imanginary come real in spirit /vision quests.

[makc]

I think early man did not knew that moon is large enough to walk on it.

p.s. I once did a calculation saying that with just 0.99999999999997761 of light speed you could reach the nearest galaxy in two weeks not really all that encouraging.

[garyclaytonpalmer]

It always amazes me how a simple question in any forum, pormotes so many answers and debates on the subject question...

[Chris Peterson]

It always amazes me how a simple question in any forum, pormotes so many answers and debates on the subject question...

Sometimes that's because what seem to be simple questions aren't really. In this case, the question has to be considered with respect to special relativity, which while not very difficult can be quite non-intuitive. When relativity is involved, questions containing "how long does it take" get interesting, since the answer is different for different frames of reference. It takes very long indeed to get to another galaxy if you're staying behind and monitoring the trip, but not necessarily long at all if you're in the spaceship going there.

[neufer]

It always amazes me how a simple question in any forum, promotes so many answers and debates on the subject question...

Sometimes that's because what seem to be simple questions aren't really. In this case, the question has to be considered with respect to special relativity, which while not very difficult can be quite non-intuitive. When relativity is involved, questions containing "how long does it take" get interesting, since the answer is different for different frames of reference. It takes very long indeed to get to another galaxy if you're staying behind and monitoring the trip, but not necessarily long at all if you're in the spaceship going there.

<<Suppose that a spacecraft accelerates at 1 g until midpoint of the journey; and then is turned around and decelerates at 1 g until arriving at its destination. For most of the trip the velocity would be very close to the speed of light and time would slow down enormously. A nearby mission objective, a sun that may have planets, is Barnard's Star, about 6 lyrs away. It could be reached in about 8 years as measured by clocks aboard the ship; the center of the Milky Way could be reached in 21 years; M31, the Andromeda galaxy, could be reached in 28 years.

In principle, such a journey would even permit us to circumnavigate the known universe in some 56 years ship time.
[Note: curiously, 56 years is the same duration as a trip that bothered to actually STOP at Andromeda
and then return home to a ticker tape welcome celebration somewhere around 4,000,000 AD].

We would return [from circumnavigating the known universe] tens of billions of years
in our future - to find the Earth a charred cinder and the Sun dead.>> - Carl Sagan _Cosmos_