So what are we supposed to believe?

[jonesdave116]

I read two science articles. One said that astronomers have discovered what could be 11 billion planets in the goldilocks zone hinting that there could be life on these planets. Then another article soon after said that astronomers after careful study of the universe they could find no sign of an advanced civilization or even a hint of life.

So what should a layman be thinking?

One should think, assuming the two articles are the ones I'm assuming they are, that:

1) We have found no Kardashev Type III civilisations in a sweep of 100 000 galaxies. Type III civilisations are those proposed by Kardashev to be capable of harnessing the energy of an entire galaxy.
http://io9.com/a-scan-of-100-000-galaxies-shows-no-sign-of-kardashev-i-1697932767

2) Kepler, and other instruments, lead us to believe there are likely to be rocky planets within or close to the HZ of their stars for roughly 1 in 10 stars in this galaxy. Ergo there COULD be life on those planets.
http://articles.latimes.com/2013/nov/04/science/la-sci-earth-like-planets-20131105

 

[Beelzebuddy]

That might be true over a short distance. But intuitively it would seem there must be a break even point where distance trumps volume. In other words, which is faster if you were delivering the data to the other side of the planet?

Also truck. The original saying is: "Never underestimate the bandwidth of a van full of tapes hurtling down a highway."

Let's say you get 1 megabyte per second to the other side of the world, and that a truck moving at highway speeds would take about a month to get there.

You'll transmit 30x24x3600 = 2952000 megabytes, or a little under three terabytes over the course of that month.

Googling current tape drive capacity, one drive is 10 TB. Bringing that one physical drive across the entire world has more than tripled our bandwidth. And a truck can hold many more drives.

 

[Ziggurat]

That might be true over a short distance. But intuitively it would seem there must be a break even point where distance trumps volume. In other words, which is faster if you were delivering the data to the other side of the planet?

If you allow for air transport (ie, stick a container on a plane), then I think even the opposite side of the planet is still higher bandwidth (of course, the latency is garbage).

https://what-if.xkcd.com/31/

 

[Ziggurat]

Googling current tape drive capacity, one drive is 10 TB.

That's economical, but if you really want to push densities, go for some microSD cards. A stack of 128 GB cards just 5 mm high, 22 mm wide, and 3 mm deep (5x2x2 cards) will give you 20 terrabytes, and I'm pretty sure that's physically smaller than your tape.

 

[Beelzebuddy]

That's economical, but if you really want to push densities, go for some microSD cards. A stack of 128 GB cards just 5 mm high, 22 mm wide, and 3 mm deep (5x2x2 cards) will give you 20 terrabytes, and I'm pretty sure that's physically smaller than your tape.

Yeah, but getting the data off them would be an absolute bitch, so I've never liked that comparison.

 

[Hercules Rockefeller]

That's economical, but if you really want to push densities, go for some microSD cards. A stack of 128 GB cards just 5 mm high, 22 mm wide, and 3 mm deep (5x2x2 cards) will give you 20 terrabytes, and I'm pretty sure that's physically smaller than your tape.

Aren't you moving much, much more information than that, just by moving the card itself?

 

[casebro]

But how long does it take to load and unload the truck?

 

[Skeptic Ginger]

So much about the truck metaphor is fungible: Travel by maximum truck speed, travel by boat or put the truck in a cargo plane.

Then there is the size of the fiber optic cable. Has that been limited in this calculation?

 

[xterra]

Won't somebody think about the truck driver?

The guy's gotta eat, sleep, etc, and also probably is union and thus is limited in the number of driving hours per day.

This slows the rate of transfer considerably.

 

[Roboramma]

Also truck. The original saying is: "Never underestimate the bandwidth of a van full of tapes hurtling down a highway."

Let's say you get 1 megabyte per second to the other side of the world, and that a truck moving at highway speeds would take about a month to get there.

You'll transmit 30x24x3600 = 2952000 megabytes, or a little under three terabytes over the course of that month.

Googling current tape drive capacity, one drive is 10 TB. Bringing that one physical drive across the entire world has more than tripled our bandwidth. And a truck can hold many more drives.

Not to mention that we can send more than 1 truck. The first truck takes 1 month to arrive, but the second truck arrives almost immediately after the first.

In one month we send 10 TB. But assume that you've got 60 trucks and one truck leaves / day. In two months you'll have sent 300 TB, and in three months 600 TB, and you're rate into the future will be a constant 300 TB/month.

 

[Ziggurat]

Yeah, but getting the data off them would be an absolute bitch, so I've never liked that comparison.

Depending on the problem in question, though, you don't necessarily need to do that. For example, if you're transferring archived information from one location to another, but that information won't need to be accessed any time soon, then no problem. Alternatively, you can think of accessing the information on it not in terms of how long you need to read the entire contents off the card, but how fast it takes to select a specific card or cards, and that may not be terribly slow OR hard, given the amount of data in question.

But yes, I've phrased the question merely in terms of peak bandwidth. In practice, there are many other metrics of interest (such as latency or cost) which can make physical transport of storage devices less favorable.

 

[Ziggurat]

So much about the truck metaphor is fungible: Travel by maximum truck speed, travel by boat or put the truck in a cargo plane.

Then there is the size of the fiber optic cable. Has that been limited in this calculation?

If we limit it to existing trucks, storage devices, and fiber optic cables, then trucks win. But again, only in terms of top bandwidth. Plenty of other metrics mater in most cases.

 

[Pianoro]

That might be true over a short distance. But intuitively it would seem there must be a break even point where distance trumps volume. In other words, which is faster if you were delivering the data to the other side of the planet?

There is an old but still very interesting to read paper here:
http://www.rfreitas.com/Astro/InterstellarProbesJBIS1980.htm#Figure1

It shows that the energetic efficiency (energy required to communicate a certain amount of information per time interval) is compareable on the interstellar scale for probes and photons (radiowaves).

The theoretical concept of spacecraft for the express purpose of communication is called a Bracewell Probe. One advantage of this approach is that once the probe has reached its target, real time communication is possible.

 

[Rum]

Life as we know it could be, and I suspect actually is, very very rare.

Even so assuming a roughly agreed number of stars in the universe at 10 to the power of 24 stars (That’s a 1 followed by twenty-four zeros) and assuming only one in a million have planets capable of supporting life as we know it and one in another million where it happens, and another one in a million where complex life resembling ours happens, that is still several million stars. Of course in a universe as vast as ours - and one I venture nobody here can remotely envisage, even an 'advanced' culture capable of transmitting some sort of signal could well be so remote that it is a hopeless task to detect it.

The above ignores time of course. Complex life may well have developed and died out on millions of other planets over the lifetime of the later (more stable) billions of years the universe has been around.

It seems likely there is complex life out there but expecting to be able to contact it is expecting too much.

Of course we could be unique and made in the image of god!

 

[Ziggurat]

Of course we could be unique and made in the image of god!

Not if you look anything like your avatar.

 

[barehl]

The space race boosted technologies in several fields. Has SETI?

SETI is intimately involved with signal fidelity. Anything that advances your ability to detect a signal at a lower energy level or in a noisier background also increases your ability to broadcast and receive signals. This is also related to things like storage on magnetic media.

One of the issues that has not been mentioned is the way information is encoded. It is very easy to detect an AM signal that is encoded for sound. It is more difficult to detect an FM signal encoded for sound. It is even more difficult to detect image data, contrary to what was depicted in the movie, Contact. It is extremely difficult to detect a digital signal because it looks very similar to background noise. I'm sure most people have had the experience of getting a fax machine on the phone. It just sounds like noise because the fax signal is digital.

So, if we are dealing with digital signals then we have to include cryptography. You look for things like repeating patterns. This type of code breaking goes back to at least WWI. This is used in other areas such as investment where computers look for patterns in the market. I believe it's also used in areas like sunspot and weather research as well as disease patterns, and some areas of life sciences. Basically, when you have a lot of data but no theory, you look for patterns. So SETI is not really as isolated as it might appear.

 

[MG1962]

SETI is intimately involved with signal fidelity. Anything that advances your ability to detect a signal at a lower energy level or in a noisier background also increases your ability to broadcast and receive signals. This is also related to things like storage on magnetic media.

One of the issues that has not been mentioned is the way information is encoded. It is very easy to detect an AM signal that is encoded for sound. It is more difficult to detect an FM signal encoded for sound. It is even more difficult to detect image data, contrary to what was depicted in the movie, Contact. It is extremely difficult to detect a digital signal because it looks very similar to background noise. I'm sure most people have had the experience of getting a fax machine on the phone. It just sounds like noise because the fax signal is digital.

So, if we are dealing with digital signals then we have to include cryptography. You look for things like repeating patterns. This type of code breaking goes back to at least WWI. This is used in other areas such as investment where computers look for patterns in the market. I believe it's also used in areas like sunspot and weather research as well as disease patterns, and some areas of life sciences. Basically, when you have a lot of data but no theory, you look for patterns. So SETI is not really as isolated as it might appear.

The other thing we have to consider is the increasing efficiency of the signal. For example increasing loads of data are being carried by secure sources such as cable, fibre optic etc etc. Even wifi (as we all have encountered has a very small broadcast radius.

 

[barehl]

1) We have found no Kardashev Type III civilisations in a sweep of 100 000 galaxies. Type III civilisations are those proposed by Kardashev to be capable of harnessing the energy of an entire galaxy.
http://io9.com/a-scan-of-100-000-galaxies-shows-no-sign-of-kardashev-i-1697932767

I've already mentioned that Type II and III are impossible so not finding them is not particularly surprising. Freeman Dyson came up with this concept back in 1937.

2) Kepler, and other instruments, lead us to believe there are likely to be rocky planets within or close to the HZ of their stars for roughly 1 in 10 stars in this galaxy. Ergo there COULD be life on those planets.
http://articles.latimes.com/2013/nov/04/science/la-sci-earth-like-planets-20131105

This list is embarrassing. You can find it here. It starts with an overestimate of the size of the habitable zone. They claim it goes from Venus out to the asteroid belt. Actually the Earth is either just inside or just outside the habitable zone. So, starting with Earth is reasonable. It only extends out to about Mars, not nearly to the asteroid belt. Secondly, they count planets that have no possibility of having life including planets smaller than the moon and as large as 3 Earth masses. They have yet to turn up even one candidate where life is possible. That's out of 150,000 Kepler Objects of Interest.

 

[MG1962]

Secondly, they count planets that have no possibility of having life including planets smaller than the moon and as large as 3 Earth masses. They have yet to turn up even one candidate where life is possible. That's out of 150,000 Kepler Objects of Interest.

I am not sure I see what the issue is with a planet of three Earth masses

 

[barehl]

I am not sure I see what the issue is with a planet of three Earth masses

It looks like around 1.7 Earth masses, you start forming gas dwarf planets.

The outer edge of the zone is about Mars. To go larger than this you have to be out farther and then the planet starts holding onto gas. In other words, it looks like anything large enough at the orbit of the asteroid belt would become a mini-Neptune. The number may not be exact but I'm comfortable saying that anything over 2 Earth masses won't have life.