Why hasn't ET phoned Earth? Maybe aliens are waiting for the exact right moment.

[Admin]

A new search for alien signals focuses on planetary transits, when exoplanets pass right in front of their suns.

Why hasn't ET phoned Earth? Maybe aliens are waiting for the exact right moment. : Read more

 

[Helio]

The argument that a transit is a great time to send us messages seems nuts. The background noise could not be worse. The SOHO spacescope, and others in L1, would be useless if they weren't using a halo orbit to keep them outside the apparent disk of the Sun.

SWAIM?

 

[COLGeek]

In transit as define by what reference point (either end and with what offset given the distance between both planets)? I agree with Helio, this seems to make little practical sense.

 

[rod]

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[COLGeek]

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No kidding. Does generate lots of clicks and theories, though.

 

[billslugg]

It might be advantageous to wait 1/4 of a year and transmit 90° from the direction to your star. Any receiving antenna would have the transmitting planet as far off to one side from the star as possible.

 

[Helio]

It might be advantageous to wait 1/4 of a year and transmit 90° from the direction to your star. Any receiving antenna would have the transmitting planet as far off to one side from the star as possible.

Yes. We have direct images of a number of exoplanets thanks to coronagraphs. The greater the elongation, the less the noise.

 

[Jan Steinman]

I don't understand what this even means, given the distances involved.

Our nearest star is about four and a quarter years away at the speed of light.

Would aliens on a planet circling Proxima Centauri (for example) send us radio signals when their planet was directly between their star and ours, or at a point in time that was about ninety days before that point, so that by the time the signal reached us, it would look like it was coming from the transiting planet?

Or would they be sending such a signal when we, the target, were either transiting, or would be transiting in 0.2465 of one of our years?

I guess I don't understand the goal of the timing, or I'd understand the timing better.

 

[billslugg]

If you are on a planet and you want to send a signal to other far away planets you need to alert your potential audience of your existence so they will turn their antennas towards you. One way to do that is to always be sending your signal in a direction opposite of your Sun. This way, anyone who just happened to be looking at your Sun would see your planet in transit and, at the same time would be right in the middle of the transmitted signal. They would think "Look, there is a planet crossing that Sun, I wonder if it might be sending a signal" and they would point their receiver antenna towards it and be able to hear the signal.
One problem with this is that they would also be pointing their antenna directly at the star, all of which are very noisy in the radio spectrum. We suggest they modify their strategy and wait until they are as far from their Sun as possible as viewed by any potential receiver. That would be exactly 1/4 of a local year from a transit. In that case they would be somewhat removed sideways from the star and we might hear their signal better.

 

[Rick From CT]

The most logical reason we haven't been contacted by aliens, or even detected any alien transmissions, is they don't use radio waves. My favorite theory is they've seeded the universe with quantum entangled communications devices that allow instantaneous communications regardless of distance. Something like the ansible device described in Enders Game. If we could find a way to tune into that, we'd really have something. I suspect contact will happen naturally as our work with quantum entanglement evolves.

 

[Jan Steinman]

they've seeded the universe with quantum entangled communications devices that allow instantaneous communications…

Violates Bell's Theorem. Three smart guys (ACZ) recently got Nobel Prizes for validating Bell.

Quantum entanglement is expected to be useful in cryptography, but not in superluminal communications.

 

[150 generation]

The most logical reason for something is often the most simple. Why we haven’t received any signals from aliens may be because there are no aliens.

 

[150 generation]

Maybe we aren’t receiving alien signals because there are no aliens?

 

[Dave]

Intelligent lifeforms of course are out there. It is the reason we listen. It is certainly possible that some intelligent lifeforms wish to contact us. What we need to figure out is how to break down the incredible barriers to communication. After all, we are dealing with a completely different world, unlike anything we have ever known.

There could be a time differential problem, within the signal itself. Say for sake of argument that intelligent life exists on a world that has a 2 year orbit (earth time) the speed of the signal may be travelling at half speed. The reality of time, for this world may operate entirely at half speed in comparison to our own. It would not be in sync within our time frame. You may have to listen within their time frame. For this world 2 years is one year in our time. A child who is two years old on our world would only be a year old on this planet. A child who is a year old in a two year period possibly exists in a different frame of time.

The language barrier must also be overcome. For example, if you want to hear a dolphin or whale speak and you wish to communicate, you must first learn their language.

 

[Helio]

Time is found to be even across the universe. The mainstream view is that all the clocks run at essentially the same rate for all galaxies. Orbital period would have no effect on the rate of time. There would be tiny difference in time rate if the exoplanet had less or more surface gravity, but insignificant for the purpose of communications.

Signals from other galaxies will be redshifted, so their frequency would vary, but astronomers know how to compensate for this.

So far, there is one key ingredient to make communication with exoplanetary worlds work -- lots of patience.

Perhaps another hundred years or so of scientific discoveries will change this, and I suspect it will happen.

 

[billslugg]

There is a "quiet window" from 1 GHz to 10 GHz. Below that stars create huge amounts of noise, above that the atmosphere absorbs them.

Signals from other civilizations will be very weak and unfortunately, humans make a lot of radio noise in that "quiet window". The only places in the solar system out of view of Earth are an orbit at 1 AU on the far side of the Sun and the far side of the Moon. Unfortunately the Moon is about to be orbited by a number of communications satellites.

 

[Dave]

Time itself of course is constant. An intelligent lifeform from another world may have a different perspective of time from our own. Looking at different speeds may be essential. Think of it this way, you will not hear a record properly at 33 speed if you play it at 78.

 

[Dave]

It is very difficult to define the present, between two different worlds. Gravitational fields may be different also changing the perspective. An intelligent lifeform on another world may disagree with you on what the present is. This will also change the past and the future.

 

[Dave]

Time speeds up and slows down when planets have different velocities. A second on earth is not the same length everywhere in the universe. This is Einstein's theory and it has been proven true.

 

[Helio]

Time speeds up and slows down when planets have different velocities. A second on earth is not the same length everywhere in the universe. This is Einstein's theory and it has been proven true.

Yes, but the bigger picture is not that variant. With a microscope, even glass looks rough.

 

[Unclear Engineer]

I think a big step in our understanding of this issue will occur when we have had the chance to thoroughly investigate Mars for evidence of prior life forms. It would help us put some constraints on the probabilities in Drake's Equation for the likelihood that there is anybody out there who is close enough to communicate with us.

There would still be plenty of uncertainty in the parameters, but understanding whether life is almost certain to originate quickly is big factor in guessing at how many planets might have life that could evolve intelligence suficient for us to detect it from here.

 

[Helio]

I think a big step in our understanding of this issue will occur when we have had the chance to thoroughly investigate Mars for evidence of prior life forms. It would help us put some constraints on the probabilities in Drake's Equation for the likelihood that there is anybody out there who is close enough to communicate with us.

There would still be plenty of uncertainty in the parameters, but understanding whether life is almost certain to originate quickly is big factor in guessing at how many planets might have life that could evolve intelligence suficient for us to detect it from here.

Agreed.

I will only add that it's still somewhat unclear how all the planets fell into their orbital slots after all their orbital shenanigans of long ago. It's been a while since I noticed any work on formation models, but when I did, they had come remarkably close at having a solid model, yet, IIRC, Pluto was a fly in their ointment.

So, there might be some ancient history to Mars that will need to be considered more than expected.

 

[Unclear Engineer]

One of the things that could make life on other planets a lot less probable would be a requirement for something like our large moon.

There are some theories that a stable, livable environment requires plate techtonic recycling of the elements in the crust and atmosphere, and that may require some tidal force dragging and heating, which basically converts rotational energy to heat and orbital energy. Strangely, Jupiter's inner moon IO may have so much tidal heating that it is too hot, and Europa may have more of the "Goldylocks" combination of heat, water and atmospheric pressure for life to develope.

But, nothing in our solar system seems to have a surface environment and atmosphere needed to produce an intelligent species that can look out at the stars and wonder if there is life on that 3rd rock from the Sun.

See https://www.nasa.gov/planetarymissions/io-volcano-observer

 

[Dave]

I believe the earth is in our solar system. We all tend to look at the search for intelligent lifeforms using our own vantage point, however life may evolve on another world at either a slower or faster rate. A male or female who is 40 years old on earth may only be 20 years old (to us) in the same orbital period on another world, simply due to that orbit being twice as long. For example, these lifeforms may age at a slower rate. Time itself may be constant, but reality may be different.

 

[Unclear Engineer]

OK, yes, the Earth we evolved and live on is in our solar system. But, it doesn't house "alien" life forms that can look at Earth from afar and wonder if something like them or us lives on our blue marble. Remember the context, please.

Regarding what I suggest we call the "speed of life" on other worlds, I think it probably would have more to do with temperature than planetary orbital period. Chemical reactions tend to be faster at higher temperatures, and live depends on chemical reactions more than photo periods.

Even on Earth, we have a wide variety of life forms with substantiallydifferent "speeds" to their lives. Warm blooded mammals are usually more quick-reaction and have shorter life spans than cold blooded reptiles. Smaller warm blooded animals seem to have shorter life times than larger warm blooded animals. And faster animals, such as hummingbirds, seem to have higher temperatures and shorter life spans.

Animals are of course tuned to their particular habitats, especially with respect to timing of activities. So some orbital periods, such as those that create changes in temperature, have corresponding cycles in animal metabolism and behaviors. Day'night, winter/summer, dry/rainy and even full-moon/new-moon. But, lifetimes for at least the most developed animals cover multiple cycles of those changes.

So, whether at 20 year old person here is equivalent in maturity to an intelligent being that has circled his/her/its/their home star 20 times doesn't really matter. But, how long they live might matter. And whether or not they can go into a metabolic stacis might matter a lot with regard to how far they can travel in space.