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History In The Making: NASA's New Horizons Probe Makes Pluto/Charon System Approach Today (*New pics of Pluto/Charon/Hydra Included*)

Mr. Sinister

By Mr. Sinister
in The Tailgate

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Major Harris

Major Harris

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Now a knock on the military. I am 100% against future space exploration moved into some sort of military capacity. I don't want the Air Force exploring the moon, Mars, etc. To me, that takes the wonder and science out of it and makes it seem like we are taking these resources by force. That's just me though.

But what do you do when lethal blue people won't let you get to the precious unobtainium?

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DCSaints_fan

DCSaints_fan

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The speed of light is too slow. Proxima Centauri is over 4 light years away.

Going the speed of light is great for extremely local space travel. Our moon is a little over 1 light-second away. Mars is up to 22 light-minutes away.

I think there are other means. It's being discovered that space and time may be a "fabric", bendable perhaps. Theories on wormholes are plausible.

 

Light speed would only be too slow for those left behind.   For those on board, the journey would be much quicker, depending on how close to the speed of light they are travelling.   A consequence of special relativity is the time dilation effect is T = ƴTo where ƴ (gamma) is the Lorentz factor 1/√(1 - v²/c²) (read 1 over the square root of the quantity 1 - square of velocity over square of the speed of light), T is the time elapsed measured by a stationary observer (relative to the traveller), and To is the time measured by the traveller.   When you plug in ratios of the speed of light, like v = 0.5 c, you can see that To becomes smaller relative to T   In other words time "slows down" for those onboard the starship - though only in terms of what the travellers are observing for objects stationary to them.  An somewhat paradoxically, the stationary observer also sees time slowing down for the travellers onboard the starship !  This gets to the heart of relativity is that there is no "absolute" or preferred frame of reference  - in the domain of special relativity we speak only in terms of velocities relative between observers (If you're more interested in this subject, look up the Twins Paradox)

 

Anyway, it is true that up to about 75% light speed (v = 0.75c), the time dilation effect is pretty small (Lorentz factor of 1.5 at this speed), so a journey taking 4 years would appear to take 4/1.5 = 2.6 years.   An improvement, but it doesn't change a years long journey into months or weeks

 

But at 90% the speed of light, the Lorentz factor is about 2.3, so the voyage to Alpha Centauri would appear to take only 4/2.3 ~ 1.7 years for the travellers

 

At 95% light speed, the Lorentz factor becomes 3.2 so the journey would take only 4/3.2 ~ 1.25 years

 

At 99% light speed, Lorentz factor is 7.1 and the journey takes only 4/7.1 ~ 0.56 years, 6 months.   Now we are getting to the order of a cruise length for a naval vessel.

 

Of course, there is a problem accelerating close to the speed of light requiring exponential energy.  This post is too long so I won't go into detail, but for any reasonable payload, you are talking about energies which aren't possible for humanity to generate at the moment

 

However, even if we could get to only say, 10% light speed, with hybernation and/or generational starship designs, it may be possible to make "short hops" of ~10-20 light years taking ~100-200 years.   This seems like small potatoes where you're talking about the galaxy being on the order of ~30,000 light years in diameter, but given the age the stars being on the order of the billions of years, we (or any other starfaring civilization) would have a quite a long time for exploration.  Such that within only a few million years after discovery of interstellar travel, the galaxy should be completely run over with a starfaring civilization - thus leading to the Fermi paradox.     

 

There are proposals such as Orion and the Buzzard ramjet that only use convental technology which might be feasible, that aren't only purely theoretical like the Alcubierre drive.   However to construct such designs we would be talking on the order of 1 year of US GNP totally dedicated to the project, and that wouldn't be feasible politically.

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d0ublestr0ker0ll

d0ublestr0ker0ll

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^^^

Awesome post. I forgot that the closer you get to light speed, the more time slows down for the traveler. It seems like a good way to time travel in a sense, where you can zip around at 99% light speed and return to Earth decades later, when you feel only a few years older.

What do you think would happen to a body when it starts nearing light speed? Would it stay intact?

6 months to the Centauris is still extremely daunting. That is at top speed to the nearest stars. Go to a star a bit further and when you get home your wife will be a geriatric, your kids older than you are. Seems like it'd get twisted.

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PokerPacker

PokerPacker

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Love it when I'm not the only nerd around who will throw out equations.

Now to move beyond equations and into the depths of insanity: When you reach the speed of light, time comes to a halt. So a photon that travelled to my eye from a star in the Andromeda Galaxy, according to its own frame of reference, did not take any time travelling from the Andromeda Galaxy to my eye; instead, as far as it is concerned, when it was born, it existed simultaneously in that star in the Andromeda Galaxy and my eye. :o How does that make sense since it's travelling a distance? Well... it's not. To go along with time dilation, there is a corresponding space contraction; according to the photon, that star in the Andromeda Galaxy and my eye are in the same spot; it never travelled from one to the other but rather exists in a reality where 2.5 million years ago in the Andromeda Galaxy is the spot in space and time as right now on Earth. Or something like that.

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mistertim

mistertim

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Good post, DCSaints_fan. This stuff has always interested me. We could use time dilation to our advantage but we'd probably still need to use some sort of hibernation for any trips that aren't "down the street" from us (in galactic terms). Like you pointed out, unless you're traveling at a very very substantial percent of the speed of light, the time dilation effects are pretty minimal. And getting a large spacecraft up to 99% the speed of light would require an ungodly amount of energy. So I'd say we're better off thinking of moving space as opposed to moving in space. The Alcubierre drive is definitely fascinating, though the problem there is that (from what I remember...haven't read up on it in a while) we'd need exotic matter and large amounts of negative energy. IIRC the energy requirements for that would be pretty ungodly too so it would require some new source of energy we haven't really thought of.

 

Maybe Donald Trump's hair holds the keys.

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skinsmarydu

skinsmarydu

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Maybe Donald Trump's hair holds the keys.

My dad worked on the development & design of 39-A&B...probably his greatest achievement. If he didn't have Alzheimer's now, he'd laugh himself silly on that comment!

I've always loved space, stars, and just wondering. Then I married an engineer. I didn't want all of the questions answered. It's cool to just wonder.

/wonderful life

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mistertim

mistertim

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Love it when I'm not the only nerd around who will throw out equations.

Now to move beyond equations and into the depths of insanity: When you reach the speed of light, time comes to a halt. So a photon that travelled to my eye from a star in the Andromeda Galaxy, according to its own frame of reference, did not take any time travelling from the Andromeda Galaxy to my eye; instead, as far as it is concerned, when it was born, it existed simultaneously in that star in the Andromeda Galaxy and my eye. :o How does that make sense since it's travelling a distance? Well... it's not. To go along with time dilation, there is a corresponding space contraction; according to the photon, that star in the Andromeda Galaxy and my eye are in the same spot; it never travelled from one to the other but rather exists in a reality where 2.5 billion years ago in the Andromeda Galaxy is the spot in space and time as right now on Earth. Or something like that.

It gets even nuttier if you start thinking about what a tachyon's frame of reference and life would be like as a (admittedly theoretical) particle that travels faster than light and has imaginary rest mass.

 

:blink:

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Bang

Bang

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I have nothing to contribute but I am greatly enjoying the discussion

Me too.

but, my step-brother is one of the mission scientists.

It's pretty cool, I'm glad and proud for him to be part of such a major historical event.

 

~J

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MrSilverMaC

MrSilverMaC

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Traveling at the speed of light is a waste of effort in a practical sense for man's effort to find a home other than earth or just explore the universe beyond our solar system in general. Only the people on the craft traveling that fast enjoy the benefits of time slowing while the entire race left on Earth possibly die out in the 100,000 years it would take them to visit the other side of just our galaxy. We need to learn if we can survive going through a wormhole and how to generate them ourselves to really be able to take advantage of a new potential home planet or explore neighboring galaxies/super clusters.

Unless you guys are talking about building a vehicle large enough to fit all of us :)

That would be cool too.

https://www.nasa.gov/mission_pages/sunearth/news/mag-portals.html

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d0ublestr0ker0ll

d0ublestr0ker0ll

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Unless you guys are talking about building a vehicle large enough to fit all of us :)

Reminds me of the documentary "Evacuate Earth". They interview a bunch of scientists about a scenario where a neutron star is headed on a collision course with Earth. The only means of survival is escaping the planet. It starts with us knowing it'll hit us 75 years in advance. We build an enormous ship that spirals around to create artificial gravity, kind of like the halos in Halo. An artificial ecosystem and habitat fill the incredibly enormous ship. Yet, only a few hundred thousand people are chosen to make the trip to the nearest Earth-like planet. Their great grandchildren will be the ones who are alive when the ship arrives at said planet. Having to leave 99% of humanity on Earth to get incinerated incites worldwide riots and warfare before the inevitable.

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mistertim

mistertim

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Speaking of worm holes. Are we sure that they even exist?

Still completely theoretical. The math works and the theory is sound, but we haven't had any direct observations of one. And if they only exist at the heart of black holes, we never will either. My understanding is the biggest issue with wormholes isn't the math or the theory it is finding ways to keep them open and stable. It would take tremendous amounts of energy and/or exotic matter/negative energy to do so. We aren't anywhere near cracking that sort of mystery yet.

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PokerPacker

PokerPacker

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It gets even nuttier if you start thinking about what a tachyon's frame of reference and life would be like as a (admittedly theoretical) particle that travels faster than light and has imaginary rest mass.

 

:blink:

The Tachyon is a fun concept to play with, but I'm pretty sure science has pretty much dismissed it as a thing. I do recall an episode of Star Trek: TNG revolving around Tachyons (not that they've only been used once) where Q was jumping Picard around between three different times so he could figure out the cause of this giant rip in space-time only for Picard to realize that he himself created that rip in the future by probing it with Tachyon pulses and the rip propagated and expanded in the past.
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mistertim

mistertim

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The Tachyon is a fun concept to play with, but I'm pretty sure science has pretty much dismissed it as a thing. I do recall an episode of Star Trek: TNG revolving around Tachyons (not that they've only been used once) where Q was jumping Picard around between three different times so he could figure out the cause of this giant rip in space-time only for Picard to realize that he himself created that rip in the future by probing it with Tachyon pulses and the rip propagated and expanded in the past.

I remember that episode! It was a good one.

 

And in Star Trek it seems they use Tachyons as a cure all for so many things.

 

"Captain, I believe if we fire a tachyon pulse directly into the spacetime distortion it may free the enterprise. Don't ask me how, I'm just making **** up as I go and Tachyons sounds pretty cool"

 

"Make it so"

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